Computer system and method for manufacturing germanium films

Abstract

A method of fabricating a germanium film on a germanium substrate is described. The method generally has selecting a coupling strength indicator that indicates a force that decouples the germanium film from the germanium substrate when applied to the germanium film; based on the coupling strength indicator, using reference data that associates a plurality of reference sets of fabrication parameters with corresponding reference coupling strength indicators to determine a set of fabrication parameters, the set of fabrication parameters including at least a first deposition temperature and a second deposition temperature that is higher than the first deposition temperature; and fabricating the germanium film on the germanium substrate based on the set of fabrication parameters, the germanium film requiring a decoupling force that is greater than the force to decouple the germanium film from the germanium substrate.

Description

Technical Field

[0001] This improvement relates generally to germanium films, and more specifically to computer-based methods and systems for manufacturing such films. Background Technology

[0002] Self-standing single-crystal germanium (Ge) films have recently shown increasing interest in a variety of applications, including infrared waveguides, photodetectors, lasers, biosensors, flexible optoelectronic devices, and lightweight solar cells (e.g., high-efficiency III-V solar cells), to name just a few. In the latter case, for example, the widespread use of germanium-based solar cells in terrestrial and space applications is often hampered by the weight and cost of bulk germanium substrates. Therefore, using thin germanium films as substrates for these devices can provide a suitable solution, as the resulting devices can be detached from the parent germanium substrate and then transferred to lightweight and low-cost supports. Furthermore, once detached, the parent germanium substrate can be repaired and reused, thereby reducing overall manufacturing costs.

[0003] Several attempts have been made to produce thin germanium films that can be detached from their corresponding parent germanium substrates. For example, Abderraouf et al. (see “Mesoporous germanium morphology transformation for lift-off process and substrate re-use.” Applied Physics Letters 102.1 (2013)) investigated the morphology and transformation of electrochemically formed mesoporous Ge bilayers during ultra-high vacuum annealing at 600–700 °C. This transformation process restructures the pores of the bottom porous Ge layer into faceted spherical voids, which can then rupture to allow the upper porous Ge layer to detach. Furthermore, PCT Publication WO 2022 / 170431 A1 discloses a process in which two non-porous Ge layers are deposited on a porous Ge layer at different temperatures. During annealing, significant morphological changes in the porous Ge layer were demonstrated, allowing the non-porous Ge layer to detach from the Ge substrate and form a Ge film. While existing thin germanium film fabrication processes are satisfactory to some extent, there is still room for improvement. For example, there is still room for improvement in ensuring sufficient coupling between the thin germanium film and the substrate to prevent self-detachment, but without excessive coupling that would hinder timely detachment and breakage. Therefore, it is necessary to control the degree of adhesion between the thin germanium film and the substrate. Summary of the Invention

[0004] Several techniques exist for fabricating thin germanium films, including epitaxial lift-off, smart dicing, controlled peeling, nanopatterned 2D materials, unsupported germanium, and porous layer lift-off. The latter technique involves using a porous germanium layer (also referred to as a "PGe layer") produced by a low-cost, wafer-scalable electrochemical etching technique as a template for epitaxial structure deposition. The weakly porous interface created between the germanium film (also referred to as the "film") and the corresponding bulk germanium substrate (also referred to as the "substrate") is then used as a facilitator to promote the film's detachment from the substrate.

[0005] While some demonstrations of this method have been completed and high material quality of the films has been demonstrated, challenges have been identified due to the variability in the coupling strength between the film and the substrate. It has been found that changing one or more manufacturing parameters can, consequently, alter the resulting coupling strength. Therefore, a method and system are provided that can determine the correct set of manufacturing parameters based on the desired coupling strength, thereby obtaining films coupled to their respective substrates with the desired coupling strength. This control over coupling strength is ideal, as the coupling strength needs to be strong enough to withstand device processing and prevent any undesirable autoattachment, yet weak enough to allow for high-yield, timely decoupling processes without causing the film to break.

[0006] According to a first aspect of this disclosure, a method for fabricating a germanium film on a germanium substrate is provided, the method comprising: selecting a coupling strength indicator, the coupling strength indicator indicating a force that decouples the germanium film from the germanium substrate when applied to the germanium film; determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference sets of manufacturing parameters with corresponding reference coupling strength indicators, the set of manufacturing parameters including at least a first deposition temperature and a second deposition temperature above the first deposition temperature; and fabricating the germanium film on the germanium substrate based on the set of manufacturing parameters, the fabrication comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at the first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at the second deposition temperature above the first deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer.

[0007] According to a second aspect of this disclosure, a system for fabricating a germanium film on a germanium substrate is provided, the system comprising: a computer receiving a coupling strength indicator indicating a force that decouples the germanium film from the germanium substrate when applied to it; the computer determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference manufacturing parameter sets with corresponding reference coupling strength indicators, the set of manufacturing parameters including at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature; and a manufacturing apparatus communicatively coupled to the computer. The device is configured to manufacture the germanium film on the germanium substrate based on the manufacturing parameter set, the manufacturing comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and a decoupling device communicatively coupled to the computer, the decoupling device being configured to apply a decoupling force to the germanium film, the decoupling force being greater than the force of the coupling strength indicator, thereby decoupling the germanium film from the germanium substrate.

[0008] According to a third aspect of this disclosure, a method for fabricating a germanium film on a germanium substrate is provided, the method comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and after the deposition of the first non-porous layer and the deposition of the second non-porous layer, heating the first non-porous layer of germanium and the second non-porous layer of the germanium and the germanium substrate to a first annealing temperature and continuing for a first time period, the first annealing temperature being higher than the first deposition temperature and the second deposition temperature.

[0009] According to a fourth aspect of this disclosure, a method for fabricating a germanium film on a germanium substrate is provided, the method comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature, the deposited first non-porous layer sealing the pores of the porous layer to capture a volume of voids within the porous layer while maintaining the original structure of the pores; depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and altering the original structure of the pores by heating the first non-porous layer, the second non-porous layer, and the germanium substrate to a given temperature and continuing for a given time period, the alteration comprising reorganizing the pores into a plurality of larger cavities, wherein a plurality of pillars extending between the germanium substrate and the first non-porous layer are interspersed in the plurality of larger cavities, the plurality of pillars having a pillar surface coverage Cps between 1% and 35%, the pillar surface coverage being given by: Among them, Ap i Let N represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, Am represent the total area of ​​the germanium film, Dp represent the column density, and Ap represent the cross-sectional area of ​​the i-th column. avg This represents the average cross-sectional area of ​​the column.

[0010] According to a fifth aspect of this disclosure, a method for manufacturing a semiconductor film on a semiconductor substrate is provided, the method comprising: selecting a coupling strength indicator, the coupling strength indicator indicating a force that decouples the semiconductor film from the semiconductor substrate when applied to the semiconductor film; determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference sets of manufacturing parameters with corresponding reference coupling strength indicators, the set of manufacturing parameters including at least a first deposition temperature and a second deposition temperature above the first deposition temperature; and manufacturing the semiconductor film on the semiconductor substrate based on the set of manufacturing parameters, the manufacturing comprising: depositing a first non-porous layer of semiconductor material onto a porous layer of the semiconductor substrate at the first deposition temperature; and depositing a second non-porous layer of semiconductor material onto the first non-porous layer at the second deposition temperature above the first deposition temperature, the semiconductor film having the first non-porous layer and the second non-porous layer.

[0011] Further according to a fifth aspect of this disclosure, the method further includes applying a decoupling force to the semiconductor film, the decoupling force being greater than the force of the coupling strength indicator, thereby obtaining a decoupled semiconductor film and a semiconductor substrate having a detached surface.

[0012] Further according to a fifth aspect of this disclosure, the method also includes cleaning a detached surface of the semiconductor substrate, forming another porous layer in the semiconductor substrate, and fabricating a second semiconductor film on the semiconductor substrate.

[0013] Further according to a fifth aspect of this disclosure, when the coupling strength indicator indicates weak coupling, the first deposition temperature is set between 275°C and 325°C, and when the coupling strength indicator indicates strong coupling, the first deposition temperature is set between 350°C and 400°C.

[0014] Further according to a fifth aspect of this disclosure, when the coupling strength indicator indicates weak coupling, the second deposition temperature is set between 525°C and 575°C, and when the coupling strength indicator indicates strong coupling, the second deposition temperature is set between 425°C and 475°C.

[0015] Further according to a fifth aspect of this disclosure, the manufacturing parameter set has a first annealing temperature, the manufacturing comprising: after the deposition of the second non-porous layer, heating the first non-porous layer, the second non-porous layer, and the semiconductor substrate to the first annealing temperature and maintaining it for a given time period, the given time period preferably being between 45 minutes and 75 minutes.

[0016] Further according to a fifth aspect of this disclosure, when the coupling strength indicator indicates weak coupling, the first annealing temperature is set between 500°C and 725°C, and when the coupling strength indicator indicates strong coupling, the first annealing temperature is set between 775°C and 850°C.

[0017] Further according to a fifth aspect of this disclosure, the manufacturing parameter set has at least one of an initial porous layer thickness and an initial porous layer porosity, the manufacturing comprising: fabricating the porous layer in the semiconductor substrate based on the at least one of the initial porous layer thickness and the initial porous layer porosity prior to depositing the first non-porous layer.

[0018] Further according to a fifth aspect of this disclosure, when the coupling strength indicator indicates weak coupling, the initial porous layer thickness is set between 250 nm and 400 nm, and when the coupling strength indicator indicates strong coupling, the initial porous layer thickness is set between 100 nm and 200 nm.

[0019] Further according to a fifth aspect of this disclosure, when the coupling strength indicator indicates weak coupling, the initial porous layer porosity is between 50% and 60%, and when the coupling strength indicator indicates strong coupling, the initial porous layer porosity is between 20% and 50%.

[0020] Further according to a fifth aspect of this disclosure, the deposition step forms a plurality of pillars extending within the porous layer of the semiconductor substrate, and the selected coupling strength indicator includes at least one of a pillar size value indicating the average pillar size, a pillar height value indicating the average pillar height, and a pillar density value indicating the pillar density.

[0021] According to a sixth aspect of this disclosure, a system for fabricating a semiconductor film on a semiconductor substrate is provided, the system comprising: a computer receiving a coupling strength indicator indicating a force that decouples the semiconductor film from the semiconductor substrate when applied to the semiconductor film; the computer determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference manufacturing parameter sets with corresponding reference coupling strength indicators, the set of manufacturing parameter sets including at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature; and a manufacturing apparatus communicatively coupled to the computer, the manufacturing apparatus being configured to be based on... The manufacturing parameters set fabricate the semiconductor film on the semiconductor substrate, the fabrication comprising: depositing a first non-porous layer of semiconductor material onto a porous layer of the semiconductor substrate at a first deposition temperature; and depositing a second non-porous layer of semiconductor material onto the first non-porous layer at a second deposition temperature, the semiconductor film having the first non-porous layer and the second non-porous layer; and a decoupling device communicatively coupled to the computer, the decoupling device being configured to apply a decoupling force to the semiconductor film, the decoupling force being greater than the force of the coupling strength indicator, thereby decoupling the semiconductor film from the semiconductor substrate.

[0022] Further according to a sixth aspect of this disclosure, the decoupling device is configured to pull the semiconductor film from the semiconductor substrate.

[0023] Furthermore, according to a sixth aspect of this disclosure, the reference data is stored on a computer-accessible, non-transitory computer-readable storage medium.

[0024] According to a seventh aspect of this disclosure, a method for fabricating a semiconductor film on a semiconductor substrate is provided, the method comprising: depositing a first non-porous layer of semiconductor material onto a porous layer of the semiconductor substrate at a first deposition temperature; depositing a second non-porous layer of semiconductor material onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, the semiconductor film having the first non-porous layer and the second non-porous layer; and after the deposition of the first non-porous layer and the deposition of the second non-porous layer, heating the first non-porous layer of semiconductor material and the second non-porous layer of semiconductor material and the semiconductor substrate to a first annealing temperature and continuing for a first time period, the first annealing temperature being higher than the first deposition temperature and the second deposition temperature.

[0025] Further according to the seventh aspect of this disclosure, the first annealing temperature is between 500°C and 725°C.

[0026] Further according to a seventh aspect of this disclosure, the porosity of the porous layer is between 50% and 55%, and the thickness is between 300 nm and 400 nm.

[0027] Further according to the seventh aspect of this disclosure, the first annealing temperature is between 775°C and 850°C.

[0028] Further according to the seventh aspect of this disclosure, the porosity of the porous layer is between 50% and 55%, and the thickness is between 200 nm and 300 nm.

[0029] Further according to the seventh aspect of this disclosure, the first annealing temperature is between 650°C and 750°C, the first time period is between 45 minutes and 75 minutes, the porosity of the porous layer is between 50% and 55%, and the thickness of the porous layer is between 200 nm and 300 nm.

[0030] According to an eighth aspect of this disclosure, a method for fabricating a semiconductor film on a semiconductor substrate is provided, the method comprising: depositing a first non-porous layer of semiconductor material onto a porous layer of the semiconductor substrate at a first deposition temperature, the deposition of the first non-porous layer sealing the pores of the porous layer to capture a volume of voids within the porous layer while maintaining the original structure of the pores; depositing a second non-porous layer of semiconductor material onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, the semiconductor film having the first non-porous layer and the second non-porous layer; and altering the original structure of the pores by heating the semiconductor substrate to a given temperature and continuing for a given time period, the alteration comprising reorganizing the pores into a plurality of larger cavities, the plurality of larger cavities having a plurality of pillars extending between the semiconductor substrate and the first non-porous layer interspersed therein, the plurality of pillars having a pillar surface coverage Cps between 1% and 35%, the pillar surface coverage being given by: Among them, Ap i Let N represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, Am represent the total area of ​​the semiconductor film, Dp represent the column density, and Ap represent the cross-sectional area of ​​the i-th column. avg This represents the average cross-sectional area of ​​the column.

[0031] Further according to an eighth aspect of this disclosure, the semiconductor film is coupled to the semiconductor substrate with a coupling strength between 0.25 MPa and 4.5 MPa.

[0032] Further according to the eighth aspect of this disclosure, the surface coverage of the column is between 1% and 5%, and the coupling strength is between 0.25 MPa and 0.75 MPa.

[0033] Further according to the eighth aspect of this disclosure, the thickness of the porous layer is between 300 nm and 500 nm.

[0034] Further according to the eighth aspect of this disclosure, the porosity of the porous layer is between 50% and 60%.

[0035] Further according to the eighth aspect of this disclosure, the surface coverage of the column is between 5% and 15%, and the coupling strength is between 0.75 MPa and 2.25 MPa.

[0036] Further according to the eighth aspect of this disclosure, the thickness of the porous layer is between 200 nm and 300 nm.

[0037] Further according to the eighth aspect of this disclosure, the porosity of the porous layer is between 30% and 50%.

[0038] Further according to the eighth aspect of this disclosure, the surface coverage of the column is between 20% and 35%, and the coupling strength is between 2.75 MPa and 4.5 MPa.

[0039] Further according to the eighth aspect of this disclosure, the thickness of the porous layer is between 100 nm and 200 nm.

[0040] Further according to the eighth aspect of this disclosure, the porosity of the porous layer is between 20% and 30%.

[0041] Further according to the eighth aspect of this disclosure, the heating is performed in at least one of the following cases: i) after the deposition of the first non-porous semiconductor layer and before the deposition of the second non-porous semiconductor layer, ii) during the deposition of the second non-porous semiconductor layer, and iii) after the deposition of the second non-porous semiconductor layer.

[0042] Further according to the eighth aspect of this disclosure, the given time period is between 45 minutes and 75 minutes.

[0043] Further according to the fifth, sixth, seventh and / or eighth aspects of this disclosure, the semiconductor substrate and the semiconductor film may, for example, include germanium.

[0044] Further according to the fifth, sixth, seventh and / or eighth aspects of this disclosure, at least one of the semiconductor substrate, the semiconductor film, the first non-porous layer and the second non-porous layer has a semiconductor material selected from: silicon (Si), indium tin oxide (ITO), zinc oxide (ZnO), and III-V group semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium gallium phosphide (GaInP), aluminum gallium arsenide phosphide (AlGaAsP), indium gallium arsenide phosphide (InGaAsP), and aluminum gallium arsenide phosphide (AlGaAsP). Indium phosphide (AlGaInP), aluminum gallium indium phosphide (InAlGaP), aluminum gallium indium phosphide (InGaAlP), aluminum gallium indium phosphide (AlInGaP), III-V heterostructures such as gallium nitride on silicon (GaN / Si), aluminum nitride on silicon (AlN / Si), gallium arsenide on silicon (GaAs / Si), gallium phosphide on silicon (GaP / Si), indium gallium arsenide on silicon (InGaAs / Si), aluminum indium nitride on silicon (AlInN / Si), gallium indium nitride on silicon (GaInN / Si), or any other III-V or III-N semiconductor material.

[0045] It should be noted that the term "coupling strength indicator" is intended to encompass any indicator that indicates the force capable of decoupling the film from the parent substrate. For example, a coupling strength indicator may be provided in the form of a force value, a pressure value, an intensity value, or a combination thereof. Force values ​​may be expressed in Newtons (N), while pressure / intensity values ​​may be expressed in Pascals (Pa). In some other embodiments, the coupling strength indicator may be provided in the form of a qualitative indicator such as "low coupling," "medium coupling," or "strong coupling." Additionally or alternatively, the coupling strength indicator may be provided in the form of one or more parameters related to the morphology of the pillars produced within the porous germanium layer. Such parameters may include, for example, pillar dimensions (e.g., average pillar diameter, average pillar height), pillar density, pillar surface coverage, etc.

[0046] The term "annealing temperature" refers to the temperature at which the annealing step is performed. The annealing step typically involves gradually heating a germanium substrate and / or a thin germanium film thereof to the annealing temperature at a given heating rate and holding that annealing temperature for a given time period.

[0047] The term "decoupling force" is intended to encompass any type of force that will be applied to the germanium film and / or the germanium substrate to decouple the film from the germanium substrate. Decoupling force can be a tensile force that pulls the germanium film away from the germanium substrate, and / or a shear force along a plane extending between the germanium film and the germanium substrate, to name just a few.

[0048] The term "coupling force" is intended to encompass the force that couples the film to the germanium substrate. Typically, a decoupling force corresponding to or exceeding the coupling force is required to decouple the film from the substrate.

[0049] The term "pillar surface coverage" is intended to quantify the amount of material within the plane intersecting with the pillars extending between the film and the substrate. The amount of porosity Cvs within the plane intersecting with the pillars between the film and the substrate will correspond to 1 minus the pillar surface coverage, i.e., Cvs = 1 - Cps. The pillar surface coverage can be calculated as follows. For example, the pillar surface coverage can be given by the following formula: Among them, Ap i Let represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, and Am represent the total area of ​​the germanium film. The column surface coverage can also be given by the following formula: Where Dp represents the column density, Ap avg This represents the average cross-sectional area of ​​the column. In some embodiments, the column has a circular shape. Therefore, the average cross-sectional area Ap is... avg can be Given, where D avg This represents the average diameter of the prism. Depending on the specific circumstances and the measurements taken of the prism, one of the equations will be more appropriate.

[0050] All the technical implementation details and advantages described with respect to a particular aspect of the invention are obviously applicable to all other aspects of the invention with the necessary modifications.

[0051] Many further features of this improvement and combinations thereof will be apparent to those skilled in the art upon reading this disclosure. Attached Figure Description

[0052] In the attached diagram,

[0053] Figure 1A is a perspective view of an example of a germanium substrate according to one or more embodiments, showing its porous layer;

[0054] Figure 1B is a perspective view of the germanium substrate of Figure 1A according to one or more embodiments, showing a germanium film coupled to the germanium substrate;

[0055] Figure 1C is a perspective view of the germanium substrate of Figure 1B according to one or more embodiments, showing the germanium film during the decoupling process;

[0056] Figure 1D is a perspective view of a germanium substrate after a cleaning process (e.g., a chemical etching process and / or a chemical mechanical removal process) according to one or more embodiments;

[0057] Figure 2 This is a schematic diagram of an example system for fabricating a germanium film on a germanium substrate according to one or more embodiments;

[0058] Figure 3 This is a schematic diagram of an example of reference data that associates a set of reference manufacturing parameters with a corresponding reference coupling strength indicator according to one or more embodiments;

[0059] Figure 4 This is a flowchart of an example method for fabricating a germanium film on a germanium substrate according to one or more embodiments;

[0060] Figure 5 It is based on one or more embodiments. Figure 2 A schematic diagram illustrating an example of the computing device of the system's computer;

[0061] Figure 6A It is a graph showing the deposition temperature over time during germanium film fabrication according to one or more embodiments, highlighting the first deposition step of depositing a first non-porous germanium layer onto a porous layer at a first deposition temperature;

[0062] Figure 6B -D is based on one or more implementation methods in the context of... Figure 6A Cross-sectional views of germanium substrates after non-porous germanium layers were deposited at first deposition temperatures of 300°C, 350°C, and 400°C, respectively.

[0063] Figure 6E -G is according to one or more implementation methods. Figure 6B Atomic force microscopy (AFM) images of non-porous germanium layers of -D;

[0064] Figure 7A This is a graph showing the deposition temperature over time during germanium film fabrication according to one or more embodiments, highlighting the... Figure 6A The annealing step is performed after the first deposition step;

[0065] Figure 7B -D is based on one or more implementation methods. Figure 6B -D germanium substrate in Figure 7A A cross-sectional view after the annealing step;

[0066] Figure 7E -G is according to one or more implementation methods. Figure 7B AFM image of a nonporous germanium layer with -D;

[0067] Figure 8A This is a graph showing the deposition temperature over time during germanium film fabrication according to one or more embodiments, highlighting the second deposition step of depositing a second non-porous germanium layer onto a first non-porous germanium layer at a second deposition temperature.

[0068] Figure 8B -D is based on one or more implementation methods. Figure 7B -D germanium substrate in Figure 8A A cross-sectional view following the second deposition step;

[0069] Figure 8E -G is according to one or more implementation methods. Figure 8B AFM image of a non-porous germanium layer with -D;

[0070] Figure 9A It is a graph showing the column diameter and column density as a function of a first deposition temperature according to one or more embodiments;

[0071] Figure 9B This is a graph showing the change in column surface coverage as a function of a first deposition temperature according to one or more embodiments, illustrating detachable regions and highly coupled regions;

[0072] Figure 9C This is a graph showing the column height as a function of a first deposition temperature according to one or more embodiments;

[0073] Figure 10A -E is a cross-sectional view of a germanium substrate with porous layers of different thicknesses according to one or more embodiments;

[0074] Figure 10F-J is based on one or more implementation methods. Figure 10A A cross-sectional view of a germanium substrate with -E after a germanium film has been deposited on the corresponding porous layer;

[0075] Figure 11A This is a graph showing the variation of the column diameter with the initial porous layer thickness according to one or more embodiments;

[0076] Figure 11B This is a graph showing the change in column height as a function of the initial porous layer thickness according to one or more embodiments;

[0077] Figure 11C It is a graph showing the change in column surface coverage as a function of initial porous layer thickness according to one or more embodiments;

[0078] Figure 11D This is a graph showing the coupling strength as a function of the initial porous layer thickness according to one or more embodiments;

[0079] Figure 12A -D indicates an implementation according to one or more embodiments. Figure 12A Initial porous layer and Figure 12B The average pore size of the first non-porous germanium layer in -D after second annealing at 400°C for 5 minutes, 10 minutes and 20 minutes, respectively;

[0080] Figure 12E This is a graph showing the change in intercrystalline spacing as a function of the duration of the second annealing, according to one or more embodiments;

[0081] Figure 13A It is a schematic diagram of a column extending from a germanium substrate, simulated based on one or more finite element models (FEMs);

[0082] Figure 13B It is based on one or more FEM simulations of pillars connected to a germanium film. Figure 13A A schematic diagram of a germanium substrate;

[0083] Figure 14A This is a cross-sectional view of a porous layer of a germanium substrate according to one or more embodiments;

[0084] Figure 14B This is a cross-sectional view of an example structure of a germanium film connected to a germanium substrate by pillars according to one or more embodiments. The structure is formed at a first deposition temperature of 300°C and a second deposition temperature of 450°C without any annealing step and is referred to as a "grown structure".

[0085] Figure 14C It is based on one or more embodiments. Figure 14B AFM images of the detached growth structure from the surface;

[0086] Figure 15A -E is a cross-sectional view of different grown-state structures after a post-deposition annealing step at first annealing temperatures of 650°C, 700°C, 750°C, 800°C and 850°C, according to one or more embodiments.

[0087] Figure 16A Scanning electron microscope (SEM) images of the detached surface of a grown structure according to one or more embodiments are shown. Figure 16E This is a diagram showing the diameter distribution of the resulting growth structure's columns;

[0088] Figure 16B SEM images of the detached surface of the grown structure according to one or more embodiments after a post-deposition annealing step at a first annealing temperature of 650°C are shown. Figure 16F This is a diagram showing the distribution of column diameters in the resulting structure;

[0089] Figure 16C SEM images of the detached surface of the grown structure according to one or more embodiments after a deposition-annealing step at a first annealing temperature of 700°C are shown. Figure 16G This is a diagram showing the distribution of column diameters in the resulting structure;

[0090] Figure 16D SEM images of the detached surface of the grown structure according to one or more embodiments after a post-deposition annealing step at a first annealing temperature of 750°C are shown. Figure 16H This is a diagram showing the distribution of column diameters in the resulting structure;

[0091] Figure 17A This is a graph showing the average column diameter (left axis) and column density (right axis) of grown structures that have undergone different post-deposition annealing steps according to one or more embodiments as a function of the first annealing temperature.

[0092] Figure 17B It is a graph showing the coupling strength as a function of the first annealing temperature according to one or more embodiments;

[0093] Figure 18A -D represents the respective implementation details used for FEM simulation according to one or more embodiments. Figure 16A -D binary format image of SEM image;

[0094] Figure 19 This is a graph showing the coupling strength as a function of the first annealing temperature according to one or more embodiments, showing experimental and simulated values; and

[0095] Figure 20This is a graph showing the variation of coupling strength with column surface coverage according to one or more embodiments. Detailed Implementation

[0096] Figure 1A-1D A perspective view of the parent germanium substrate 100 during the fabrication of the germanium film 102 and the decoupling of the film 102 from the substrate 100 is shown. More specifically, Figure 1A shows an example of a substrate 100 having a porous layer 104. The porous layer 104 is typically characterized by initial parameters, including but not limited to an initial porous layer thickness and an initial porous layer porosity. Figure 1B shows the substrate of Figure 1A on which the film 102 has been fabricated. In some embodiments, the film fabrication process includes a first germanium deposition step performed at a first deposition temperature and a second germanium deposition step performed at a second deposition temperature higher than the first deposition temperature. This covers the first epitaxial germanium deposition step resulting in the deposition of a first non-porous germanium layer on the porous layer of the substrate. The first non-porous germanium layer typically seals the pores of the porous layer of the substrate. The second epitaxial germanium deposition step results in the deposition of a second non-porous germanium layer on the first non-porous layer. Because the second deposition step is performed at a higher temperature, the pores of the porous layer typically undergo morphological changes, producing pillars 106 extending from the substrate and the first non-porous germanium layer. An example of this process is described in detail in PCT Patent Publication No. WO 2022 / 170431 A1. It has been found that the mechanical properties of the pillars (including, but not limited to, pillar height, pillar diameter, and pillar density) affect the strength of the coupling between the substrate and the film. It has also been found that changing certain manufacturing parameters can further alter the mechanical properties of the pillars. Therefore, by changing one or more manufacturing parameters, the resulting pillar morphology and associated coupling strength can be determined, which may be highly desirable because some applications may require stronger coupling between the substrate and the film, while others may require weaker coupling. Figure 1C shows an example film 102 being decoupled (or equivalently detached) from substrate 100. As shown, the manufacturing parameters of film 100 are selected to produce the desired coupling strength Fc. Therefore, when a decoupling force F greater than the desired coupling strength Fc is applied to film 102, the film decouples from the parent substrate 100, leaving broken pillars on the detached surface of the substrate. Figure 1D shows the parent substrate after the broken pillars 108 have been removed by an additional process (e.g., chemical etching or chemical mechanical removal). Therefore, the resulting substrate 100 is ready for another film manufacturing process, which can reduce manufacturing costs in the long term. It should be noted that the germanium film 102 and the germanium substrate 100 preferably comprise single-crystal germanium.

[0097] Figure 2An example of a system 200 for fabricating a germanium film on a germanium substrate according to one embodiment is shown. As shown, the system includes a computer 202, a fabrication apparatus 204, and a decoupling device 206. More specifically, the computer 202 is configured to receive a selected coupling strength indicator 208, which indicates the force that decouples the film from the substrate when applied to the film. In some embodiments, the coupling strength indicator 208 may be provided, for example, in the form of a force, pressure, or intensity value expressed in megapascals. However, in some embodiments, the coupling strength indicator 208 may be provided in the form of column dimensions (e.g., column diameter), column height, column density, etc. In some embodiments, it has been found that controlling the fabrication parameters to increase the column diameter can thereby increase the coupling strength. In some other embodiments, it has been found that controlling the fabrication parameters to increase the column height can thereby weaken the coupling strength. It is contemplated that different combinations of column size, height, and density can result in different coupling strengths. In some other embodiments, as yet another alternative, the coupling strength indicator 208 may be provided in the form of a percentage of column surface coverage.

[0098] As shown, computer 202 is configured to determine manufacturing parameter sets 210 based on coupling strength indicators using reference data 212, which associates different reference manufacturing parameter sets with corresponding reference coupling strength indicators. In some embodiments, computer 202 may also receive desired film characteristics 214, such as indicators of desired film thickness, surface roughness, etc. In these embodiments, computer 202 may also consider desired film characteristics 214 when determining manufacturing parameter sets 210. It is contemplated that manufacturing parameter sets 210 include at least a first deposition temperature indicating the temperature at which a first non-porous germanium layer is deposited and a second deposition temperature indicating the temperature at which a second non-porous germanium layer is deposited. However, it is understood that manufacturing parameter sets 210 may include many other manufacturing parameters 210, including but not limited to a first deposition duration, a first deposition thickness, a first deposition rate, a second deposition duration, a second deposition thickness, a second deposition rate, etc. For embodiments where a first annealing step is performed after the first and second depositions, the manufacturing parameter set 210 may include, but is not limited to, the presence of the first annealing step (this parameter may have binary values, such as yes / no, 1 / 0), the first annealing temperature, the first annealing duration, etc. For embodiments where a second annealing step is performed after the first deposition and before the second deposition, the manufacturing parameter set 210 may include, but is not limited to, the presence of the second annealing step (this parameter may have binary values, such as yes / no, 1 / 0), the second annealing temperature, the second annealing duration, etc. Additionally or alternatively, the manufacturing parameter set 210 may also include information related to the initial porous layer of the germanium substrate. For example, the initial porous layer thickness and the initial porous layer porosity may also be relevant manufacturing parameters 210 that can be changed to adjust the resulting coupling strength.

[0099] As shown, the manufacturing apparatus 204 is communicatively coupled to a computer. Therefore, the manufacturing apparatus 204 is configured to manufacture a germanium film on a germanium substrate based on a determined set of manufacturing parameters. Typically, film manufacturing includes the following steps: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature, wherein the germanium film has the first and second non-porous layers. Therefore, at least the first and second deposition temperatures are manufacturing parameters that can be changed to adjust the resulting coupling strength. The manufacturing apparatus 204 may be provided in the form of a programmable industrial chemical vapor deposition (CVD) apparatus, such as an improved chemical vapor deposition (MCVD) apparatus, a metal-organic chemical vapor deposition (MOCVD) apparatus, etc., depending on the implementation.

[0100] Still refer to Figure 2 The diagram illustrates a system 200 with a decoupling device 206 communicatively coupled to a computer 202. The decoupling device 206 is configured to apply a decoupling force to a film. When the decoupling force exceeds the force indicated by the coupling strength indicator 208, the germanium film is decoupled from the germanium substrate. The decoupling device 206 can be embodied by a robotic arm, such as one equipped with a scraper, or any other device capable of satisfactorily decoupling the film from the substrate after manufacturing. In some embodiments, the decoupling device 206 is configured to pull the germanium film from the germanium substrate.

[0101] It is anticipated that reference data 212 may be stored on a non-transitory computer-readable storage medium of a computer or on any computer storage medium accessible to the computer. Figure 3An example of this reference data 312 is shown. As illustrated, three different sets of reference manufacturing parameters are shown. In the first reference set, the manufacturing parameters include a first deposition temperature labeled "1", a second deposition temperature labeled "2", and no annealing step. The first set of reference manufacturing parameters can be used when a coupling force corresponding to the reference coupling strength indicator labeled "1" is desired. In the second reference set, the manufacturing parameters include a first deposition temperature labeled "3", a second deposition temperature labeled "4", and a first annealing step is present. More specifically, a first annealing temperature labeled "5" is provided for the first annealing step. The second set of reference manufacturing parameters can be used when a coupling force corresponding to the reference coupling strength indicator labeled "2" is desired. In the third reference set, the manufacturing parameters include a first deposition temperature labeled "3", a second deposition temperature labeled "4", and a second annealing step is present. More specifically, a second annealing temperature labeled "6" is provided for the second annealing step. The third set of reference manufacturing parameters can be used when a coupling force corresponding to the reference coupling strength indicator labeled "3" is desired. The reference data may have as many reference sets as experimental or simulation results can provide. Therefore, in some implementations, the reference data may include two or more reference sets. The reference data may include reference parameters such as porosity percentage, pore size, porous layer thickness, and associated reference coupling strength indicators.

[0102] Figure 4 A flowchart of an example method 400 for fabricating a germanium film on a germanium substrate is shown. In some embodiments, method 400 may be partially or entirely constructed by… Figure 2 System use Figure 3 The reference data is executed.

[0103] In step 402, a coupling strength indicator is selected. The coupling strength indicator typically indicates the force required to decouple the germanium film from the germanium substrate when applied to it. As mentioned above, the coupling strength indicator may correspond to a desired coupling strength value or a desired pillar characteristic, depending on the implementation. More specifically, the coupling strength indicator may be provided in the form of pillar size values, pillar height values, and pillar density values, respectively indicating one of the pillar size, pillar height, and pillar density associated with the pillars formed within the germanium film after the aforementioned deposition steps.

[0104] In step 404, a set of manufacturing parameters is determined based on a coupling strength indicator. Step 404 can be performed using accessible reference data. The reference data typically associates different reference sets of manufacturing parameters with corresponding reference coupling strength indicators. It is anticipated that the set of manufacturing parameters includes at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature. As described above, the first deposition temperature typically indicates the temperature at which a first non-porous germanium layer is deposited onto a porous layer on a germanium substrate, while the second deposition temperature indicates the temperature at which a second non-porous germanium layer is deposited onto the first non-porous germanium layer. It should be noted that the deposition of the second non-porous germanium layer at a higher second deposition temperature, or when an intermediate annealing step (often referred to herein as the "second annealing step"), causes at least a portion of the porous substrate layer to change its morphology and transform into a pillar-containing layer. The pillar-containing layer comprises pillars extending between the substrate and the first non-porous germanium layer and typically acts as a weak (or strong) interface that can break to decouple the film from the substrate. As described above, the pillars can be characterized by height, size, density, surface coverage, or a combination thereof.

[0105] In some embodiments, the first deposition temperature can be varied to affect the resulting coupling strength. For example, in embodiments where the coupling strength indicator indicates weak coupling, the first deposition temperature can be set between 275°C and 325°C. In embodiments where the coupling strength indicator indicates strong coupling, the first deposition temperature can be set between 350°C and 400°C. In embodiments where the coupling strength indicator indicates moderate coupling, the first deposition temperature can be set between 325°C and 350°C (excluding the endpoints), but these embodiments may not be preferred. These first deposition temperatures can depend on one or more other manufacturing parameters, including but not limited to the first deposition rate, the first deposition duration, the desired film thickness, etc. For example, the first deposition temperature described above is based on a first deposition rate considered to be low (e.g., 0.5 μm / h). In embodiments with a higher first deposition rate (e.g., 2 μm / h), the first deposition temperature can be, for example, 100°C higher than the temperature described above.

[0106] Additionally or alternatively, the second deposition temperature can be varied to adjust the resulting coupling strength. More specifically, in embodiments where the coupling strength indicator indicates weak coupling, the second deposition temperature can be set between 525°C and 575°C. In embodiments where the coupling strength indicator indicates strong coupling, the second deposition temperature is set between 425°C and 475°C. In embodiments where the coupling strength indicator indicates moderate coupling, the second deposition temperature can be set between 475°C and 525°C (excluding the endpoints), but these specific embodiments may not be preferred. As mentioned above, these temperatures can vary depending on other manufacturing parameters.

[0107] In some embodiments, the manufacturing parameter set includes a first annealing temperature useful when performing the first annealing step. In this disclosure, the first annealing step includes the following steps: after depositing the second non-porous layer, heating the first and second non-porous layers and the germanium substrate to the first annealing temperature and maintaining it for a given time period. The given time period can be between 45 minutes and 75 minutes, depending on the embodiment. In embodiments where the coupling strength indicator indicates weak coupling, the first annealing temperature can be set between 500°C and 725°C. In embodiments where the coupling strength indicator indicates strong coupling, the first annealing temperature can be set between 775°C and 850°C. In embodiments where the coupling strength indicator indicates moderate coupling, the first annealing temperature can be set between 725°C and 775°C (excluding the endpoints), but these embodiments may not be preferred. Similarly, these temperatures can vary depending on other manufacturing parameters. The first annealing duration is set to 1 hour. However, in some other embodiments, the first annealing duration can be greater than 1 hour or less than 1 hour, in which case the aforementioned first annealing temperature threshold of 750°C can be varied. Under no circumstances should the first annealing temperature reach a maximum of 938°C, as this corresponds to the melting temperature of germanium.

[0108] In some embodiments, the manufacturing parameter set includes a second annealing temperature that is relevant to the second annealing step. As disclosed herein, the second annealing step includes the following steps: heating the first non-porous layer to the second annealing temperature and maintaining it for a given time period after depositing the first non-porous layer and before depositing the second non-porous layer. The given time period can be between 45 minutes and 75 minutes. In embodiments where the coupling strength indicator indicates strong coupling, the second annealing temperature can be set between 325°C and 350°C. However, in embodiments where the coupling strength indicator indicates weak coupling, the second annealing temperature is set between 400°C and 575°C. Again, these temperatures can vary depending on other manufacturing parameters. In some experiments, the second annealing duration is set to 1 hour. However, in some other embodiments, the second annealing duration can be greater than 1 hour or less than 1 hour, in which case the aforementioned second annealing temperature values ​​can vary. It should be understood that the second annealing temperature should be at least equal to or preferably higher than the second deposition temperature.

[0109] In some embodiments, the fabrication parameter set includes at least one of an initial porous layer thickness and an initial porous layer porosity. In these embodiments, method 400 includes the step of fabricating a porous layer in a germanium substrate based on the initial porous layer thickness and / or the initial porous layer porosity prior to depositing a first non-porous layer. In embodiments where the coupling strength indicator indicates weak coupling, the initial porous layer thickness may be set between 250 nm and 400 nm. In embodiments where the coupling strength indicator indicates strong coupling, the initial porous layer thickness may be set between 100 nm and 200 nm. In embodiments where the coupling strength indicator indicates moderate coupling, the initial porous layer thickness may be set between 200 nm and 250 nm (excluding the endpoints), but these embodiments may not be preferred. Similarly, in embodiments where the coupling strength indicator indicates weak coupling, the initial porous layer porosity may be between 50% and 60%. In embodiments where the coupling strength indicator indicates strong coupling, the initial porosity of the porous layer can be between 20% and 50%, preferably between about 30% and 50%, and most preferably between 40% and 50%. Typically, the amount of voids present in the columnar layer defines the resulting coupling strength. In other words, increasing the amount of voids in the columnar layer (e.g., higher porosity, greater thickness) can lead to weaker coupling. Conversely, reducing the amount of voids in the columnar layer, which can further increase the mass (e.g., lower porosity, smaller thickness), can lead to stronger coupling.

[0110] In step 406, a germanium film is fabricated on a germanium substrate based on the fabrication parameter set determined in step 404. Fabrication typically includes: a first deposition step comprising depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; and a second deposition step comprising depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature. The germanium film thus comprises at least the first and second non-porous layers. In some other embodiments, additional non-porous layers of the same or other semiconductor materials may be present. Examples of such semiconductor materials may include, but are not limited to, silicon (Si), indium tin oxide (ITO), zinc oxide (ZnO), III-V group semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium gallium phosphide (GaInP), aluminum gallium arsenide phosphide (AlGaAsP), indium gallium arsenide phosphide (InGaAsP), aluminum gallium indium phosphide (AlGaInP), aluminum gallium indium phosphide (InAlGaP), aluminum gallium indium phosphide (InGaAlP), aluminum gallium indium phosphide (AlInGaP), and III-V group heterostructures such as gallium nitride on silicon (GaN / Si), aluminum nitride on silicon (AlN / Si), gallium arsenide on silicon (GaAs / Si), gallium phosphide on silicon (GaP / Si), indium gallium arsenide on silicon (InGaAs / Si), aluminum indium nitride on silicon (AlInN / Si), and gallium indium nitride on silicon (GaInN / Si).

[0111] In step 408, a decoupling force is applied to the germanium film. The decoupling force is greater than the force indicated by the coupling strength indicator. Therefore, the germanium film is decoupled from the germanium substrate, leaving the decoupled germanium film and the germanium substrate with a detached surface. It should be understood that step 408, applying the decoupling force, is optional in some embodiments. In practice, the film can be sold while still coupled to the parent substrate, for example, for decoupling by a third party at a remote location.

[0112] In some embodiments, method 400 may include the steps of: cleaning the detached surface of the germanium substrate, forming another porous layer in the germanium substrate, and forming another germanium film on the germanium substrate based on a different set of manufacturing parameters. However, in some embodiments, for example, the same set of manufacturing parameters may be reused to sequentially form germanium films on the same parent substrate. The cleaning process may include any suitable type of cleaning process, including but not limited to chemical etching processes, chemical mechanical removal processes, etc.

[0113] Now refer to Figure 5 , Figure 2 The system's computer can be provided as a combination of hardware and software components. The hardware components can be implemented as computing device 500, an example of which is provided below. Figure 5The computing device 500 may have a processor 502, a memory 505, and an I / O interface 506. Instructions 508 for manufacturing germanium films, determining manufacturing parameter sets, and / or instructing manufacturing apparatus may be stored in the memory 505 and accessible by the processor 502.

[0114] Processor 502 may be, for example, a general-purpose microprocessor or microcomputer, a digital signal processing processor (DSP), an integrated circuit, a field-programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), a programmable logic computer (PLC), or any combination thereof.

[0115] The memory 505 may include any suitable combination of computer-readable memories, whether internal or external, such as random access memory (RAM), read-only memory (ROM), optical disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), ferroelectric RAM (FRAM), etc.

[0116] Each I / O interface 506 enables the computing device 500 to interconnect with one or more input devices such as a keyboard, mouse, or accessible database, or with one or more output devices such as a monitor, external network, or accessible database.

[0117] Each I / O interface 506 enables the computer to communicate with other components, exchange data with other components, access and connect to network resources, service applications, and perform other computing applications by connecting to a network (or multiple networks) capable of carrying data, including the Internet, Ethernet, Common Old-Style Telephone Service Line (POTS), Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), Digital Subscriber Line (DSL), coaxial cable, fiber optic, satellite, mobile, wireless (e.g., Wi-Fi, WiMAX), SS7 signaling network, fixed line, local area network, wide area network, etc., including any combination of these.

[0118] The computing device 500 and any software applications that can be run by the computing device 500 are merely examples. As will be apparent to those skilled in the art, other suitable implementations of the computer may also be provided.

[0119] Example 1 – Adjusting the coupling strength detachable from the germanium film by changing the first deposition temperature through porous germanium transformation.

[0120] In this embodiment, experimental tests were conducted during membrane fabrication. In these embodiments, the fabrication method includes the following steps: after depositing a first non-porous layer and before depositing a second non-porous layer, heating the first non-porous layer to a second annealing temperature and maintaining it for a given time period (also referred to as the "second annealing temperature"). These tests aim to determine the effect of the second annealing temperature on the resulting coupling strength.

[0121] More specifically, Figure 6A The diagram shows the variation of deposition temperature over time during germanium film fabrication, with a focus on the first deposition step (marked "#1" in the figure), in which a first non-porous germanium layer is deposited onto the porous layer at the first deposition temperature. Figure 6B -D is in Figure 6A Cross-sectional views of germanium substrates after deposition at first deposition temperatures of 300°C, 350°C, and 400°C, respectively. Figure 7A Emphasis was placed on Figure 6A The annealing step (marked "#2" in the figure) is performed after the first deposition step. Figure 7B -D indicates that in Figure 7A After the annealing step Figure 6B -D germanium substrate. Figure 8A The second deposition step (marked "#3" in the figure) is highlighted, in which the second non-porous germanium layer is deposited on the first non-porous germanium layer at the second deposition temperature. Figure 8B -D is Figure 7B -D germanium substrate in Figure 8A A cross-sectional view following the second deposition step. The results of these tests are summarized in... Figure 9A -B in. As shown in the figure. Figure 9A The changes in column diameter and column density with the first deposition temperature are shown, while Figure 9B The diagram illustrates the variation of column surface coverage with the first deposition temperature, showing detachable and highly coupled regions. It is understood that strongly coupled regions are observed when the second annealing temperature is set between 325°C and 350°C, while weakly coupled regions are observed when the second annealing temperature is set between 400°C and 575°C. In some embodiments, it has been found advantageous to determine the annealing temperature based on the initial porous layer porosity, the initial porous layer thickness, or a combination thereof.

[0122] The reorganization of porous germanium during sintering under various atmospheres is well-known, but its transformation into a porous layer and its relationship with membrane adhesion strength have not been thoroughly investigated. Furthermore, the effects of PGe properties and growth conditions on membrane mechanical properties have also been unstudied. In this embodiment, the effects of growth temperature and PGe thickness on the properties of the porous separation layer and their influence on the adhesion strength of Ge nanofilms are reported. The results show that membrane adhesion strength can be continuously customized, ranging from freestanding to quasi-welded structures, while maintaining surface and crystal quality.

[0123] In this embodiment, the PGe layer was prepared using bipolar electrochemical etching (BEE), employing p-type gallium doping (100), a resistivity of 8-30 mΩ·cm, and a 6° offset in the (111) direction. To prepare the PGe layer, etching and passivation asymmetric pulses were applied for a duration of 1 s. The current densities applied during BEE were 0.75 and 1.00 mA·cm⁻¹, respectively. -2 The BEE conditions employed allowed for the acquisition of a uniform PGe layer with a porosity of 45% on a 100 mm germanium substrate. The germanium substrate with the PGe layer on top was then rinsed with EtOH (99%, anhydrous) and dried under a nitrogen gas flow.

[0124] The germanium film was processed using a 4-inch VG Semicon V90F hybrid CBE / MBE reactor equipped with a liquid nitrogen cold trap at a temperature of 4.5 × 10⁻⁶. -6 Deposition was performed under Torr pressure. A Ge Knudsen cell heated to 1250 °C was used as a solid Ge source, providing a deposition rate of 0.5 μm / h. First, a 200 nm thick low-temperature (LT) first non-porous layer was deposited, followed by in-situ annealing at 550 °C for 10 min, and then a 700 nm thick second non-porous layer was deposited at 475 °C. The deposition temperature of the first non-porous layer (T...) was determined by... g A series of germanium film samples were produced by varying the temperature from 300℃ to 400℃ and the thickness of the PGe layer from 150nm to 350nm.

[0125] The adhesion strength of the germanium film was evaluated in quasi-static mode using appropriate software with a custom-made device equipped with a TA.XTPlus machine and a decoupling apparatus. The front and back sides of the sample were bonded to a specialized fixture using commercial JB WELD 8281 epoxy resin. The separation force of the layers was then converted to MPa based on the separation area.

[0126] Cross-sectional observations were performed using a scanning electron microscope (SEM) LEO 1540 XB® and a Thermo Scientific Scios 2 DualBeam to observe the PGe layer before and after the deposition process. An accelerating voltage of 20 keV was used for each SEM. The surface roughness of the germanium film was characterized by atomic force microscopy (AFM, Park System NX20) in non-contact mode (NCM) with a scan size of 5 × 5 μm. 2 The resolution is 512×512 pixels. 2 .

[0127] To investigate the effect of the deposition temperature of the first non-porous layer on PGe layer recombination and film adhesion properties, deposition temperatures were set at 300℃, 350℃, and 400℃. gBelow, a 200 nm thick first non-porous layer is deposited on a 200 nm thick PGe layer. The corresponding cross-sectional SEM and AFM characterizations are as follows: Figure 6B As shown in -G. In fact, the deposition temperature of the first non-porous layer has a significant impact on the morphological transformation of the PGe layer. For example... Figure 6B As shown, in T g At 300°C, the PGe layer remained unchanged after growing a 200 nm thick first non-porous layer. However, when T... g When the temperature is increased to 350°C, the overall thickness of the PGe layer shrinks by approximately 20%. Figure 6C This is a direct result of thermally induced PGe layer recombination. Furthermore, T... g Further increase to 400℃ ( Figure 6D This reduces the PGe layer thickness to 96 nm, representing a shrinkage of approximately 50%. The observed behavior can be understood based on the Ostwald ripening (OR) phenomenon, where an increase in the thermal budget leads to an increased degree of PGe recombination. Indeed, when the temperature reaches a certain threshold (above 300 °C for PGe), the surface mobility of Ge atoms within the pores increases, and the porous structure tends to minimize its surface energy by merging pores, thereby reducing its volume-to-surface-area ratio. This results in the formation of dense, interconnected columnar microcrystals, such as… Figure 6C As shown, and will be discussed further later. Figure 10A Ultimately, this leads to the formation of structures with a small number of cavities after coalescence at higher temperatures. Figure 6D ).

[0128] Meanwhile, the PGe morphology transformation that occurs during the first non-porous layer deposition also involves the diffusion of Ge atoms into the PGe layer. Specifically, in the initial stage of Ge deposition on the PGe layer at temperatures of 300°C and below, the PGe layer does not undergo any transformation, thus limiting the diffusion of adsorbed atoms into the PGe layer. At higher deposition temperatures, the recombination-induced pore size increase increases the diffusion length of adsorbed atoms, contributing to pore filling. This increase in pore size or nanopores, coupled with the increase in thermal budget, leads to partial filling of the PGe layer during the first non-porous layer deposition. This phenomenon has a direct impact on the surface roughness of the film and the microstructure properties of the separation layer.

[0129] Therefore, as Figure 6EAs shown in Figure -G, the AFM images reveal that the root mean square (RMS) roughness increases with increasing deposition temperature. Indeed, without reconstruction of the PGe layer, the diffusion of adsorbed atoms into the PGe layer is restricted, resulting in a first non-porous layer with a surface roughness below 1 nm, close to the substrate surface roughness (0.23 ± 0.02 nm). With increasing deposition temperature, the porosity increases accordingly, hindering the formation of a smooth film surface. Therefore, the measured surface roughness is found to increase with increasing Tg, with the structure grown at 400 °C achieving an RMS roughness of 5 nm. Figure 6E and 6F The AFM images show that the increase in RMS roughness originates from pits generated by Ge nucleation on the rough surface of the recombined PGe layer. Therefore, the RMS roughness increases from 1.4 nm at 350 °C to 5 nm for structures grown at 400 °C with increasing PGe recombination degree.

[0130] To reduce surface roughness by sealing these pits and to enable the formation of a separation layer, the structure was annealed at 550°C. This annealing temperature indicates that the optimal temperature for PGe recombination is in the range of 550°C to 600°C. Indeed, when this thermal budget is applied, the PGe recombination kinetics are enhanced, ultimately leading to the formation of a separation layer. Figure 7B -G indicates that the operation is performed with Figure 6B The study analyzed the same three deposition conditions in -G, but added the final structural morphology of post-deposition annealing at 550℃ for 10 min in each experiment. The images show that for a Tg of 300℃, the separation layer is fully formed, with large pores confined within a planar region. Figure 7B ), and the surface remains smooth, with a measured RMS roughness of less than 1 nm ( Figure 7E ).

[0131] At higher deposition temperatures (350°C), a separation layer with smaller voids separated by larger columns was observed to form. Figure 7D ), and a rougher resulting surface, with an RMS of approximately 1 nm ( Figure 7F For the samples grown at 400 °C, although the surface roughness was slightly improved, the PGe layer appeared insensitive to the additional annealing step, indicating that remodeling had already been completed during the deposition of the first non-porous layer. For each of the three experiments, the surface roughness of the samples annealed after deposition was improved, confirming the benefit of this additional step in the process. The improvement appeared to be more significant for the samples with higher first non-porous layer deposition temperatures, likely due to the rougher surface at the start of the annealing step. To further improve surface roughness and increase film thickness, an additional 1 μm thick second non-porous layer was deposited at 475 °C after a high-temperature (HT) annealing step. SEM cross-sectional images of these structures showed no significant morphological evolution of the separation layer. Figure 8B-D), because the deposition temperature used is lower than the annealing temperature. Simultaneously, the deposition of a 1 μm thick second non-porous layer significantly improves the surface roughness of all germanium films compared to the first non-porous layer T. g =300℃, RMS roughness as low as 1nm, for T g =400℃, RMS roughness as low as 1.2nm ( Figure 8F -G). This morphological improvement comes from reducing the pit depth through gradual filling. In fact, using a first non-porous layer grown at below 300°C, a high-quality III-V heterostructure can be obtained, enabling the performance of the developed III-V solar cell to approach that of the same III-V structure grown on a bulk germanium substrate.

[0132] To further analyze the first non-porous layer T g The influence on the properties of the separation layer, based on the SEM cross-sectional image ( Figure 8B -D) The diameter and density of the column were estimated. The results are plotted on Figure 9A In fact, when T g When the temperature is increased from 300℃ to 400℃, the density of the column increases from 33 column bodies / μm. 2 Decreased to approximately 5 column heights / μm 2 The average diameter of the columns increased significantly from 70 nm to 330 nm. However, as... Figure 9C As shown, the column height appears unaffected by the deposition of a 1 μm thick second non-porous layer after the annealing step. In fact, after the annealing step, the average column height is approximately 92.5 nm, compared to approximately 98 nm after the deposition of the 1 μm thick first non-porous layer. After the annealing step, the remaining cavities significantly slow their migration to the PGe layer / first non-porous layer interface and promote lateral aggregation, thus minimizing the impact on column height and allowing for the formation of larger diameter columns. This significant evolution of pore size and density has a significant impact on germanium film adhesion. Indeed, for the first non-porous layer deposited at 300 °C, the film was found to detach easily, with a detachment yield of 100%. The corresponding adhesion was evaluated to be approximately 2 MPa. Meanwhile, for the first non-porous layer T… g The adhesion strength generated by the columnar properties of the membrane at 350°C and 400°C exceeds the limit of the tensile testing apparatus used, which is set by the epoxy resin adhesion strength of 4.5 MPa. The membrane adhesion strength can be increased by increasing the coverage of the columnar surface (…). Figure 9B This can be explained by the fact that the column surface coverage is estimated from the column diameter and density. Membrane adhesion increases with increasing column surface coverage, indicating that a larger column surface area requires greater force for membrane separation.

[0133] The increased adhesion is primarily due to the combined effect of PGe layer reorganization or pore filling, leading to pore annihilation. The amount of confined porosity within the separation layer influences the morphology and distribution of the columns, and thus, the membrane adhesion. To assess the impact of the amount of confined porosity within the separation layer on membrane adhesion, [the following was used]... Figure 8B The same deposition conditions were used for the structure shown (maintaining the T of the first non-porous layer). g The effect of PGe layer thickness on PGe recombination and adhesion properties was investigated at 300℃. PGe layer thicknesses ranging from 100 nm to 300 nm with 50 nm increments were studied. Figure 10A -E is shown.

[0134] The morphology of the separated layer was found to be strongly dependent on the initial PGe layer thickness. This was based on cross-sectional SEM images (…). Figure 10F -J), measured the dimensions of the column and summarized them. Figure 12A and 12B In the middle. The PGe structure formed towards the column is reorganized in Figure 12B The results are well presented. For a PGe layer with an initial thickness of 100 nm, the average height of the resulting pillars is 50 nm, and the diameter is approximately 120 nm. An initial increase in PGe layer thickness leads to a continuous increase in pillar height, reaching 90 nm, while simultaneously causing a continuous decrease in average diameter, dropping to 40 nm. Simultaneously, the pillar density initially increases with increasing PGe layer thickness, exceeding 50 pillars / μm for a 250 nm thick PGe layer. 2 ( Figure 12A Then, for a 300 nm thick PGe layer, the concentration drops sharply to only 10 columns / μm. 2 The latter phenomenon may be a direct consequence of the reduction in column diameter. In fact, columns with very small diameters (below a certain threshold) may not be stable enough and are expected to disappear, instead thickening the inner surface of their closely spaced columns or separating layers.

[0135] The combination of column diameter results and column density allows for the assessment of column surface coverage. Figure 12C In fact, it was found that when the PGe layer thickness increased from 100 nm to 300 nm, the surface coverage decreased significantly from nearly 22% to only 1%. This behavior has a significant impact on the film adhesion strength, such as... Figure 12DAs shown. In fact, for structures with high surface coverage, corresponding to a PGe layer thickness of less than 150 nm, the germanium film exhibits high adhesion strength, exceeding that of the epoxy resin adhesive used. Meanwhile, films deposited on a 300 nm thick PGe layer exhibit very low surface coverage, resulting in easily detachable films with adhesion strength lower than that of the copper strips used. However, PGe layer thicknesses between 150 nm and 300 nm (excluding the endpoints) show good suitability for detachable devices on germanium films, with adhesion allowing film release (lower than epoxy resin adhesion) and providing mechanically stable structures (higher than copper strip adhesion). It has been shown that germanium films deposited on structures with a 170 nm structure and a porosity close to that presented in this study can be detached and used for the growth of III-V materials. Furthermore, it has recently been demonstrated that a 200 nm thick PGe layer with the same porosity as presented in this study enables promising efficiencies in III-V solar cells.

[0136] While this embodiment demonstrates the potential of using the first non-porous layer deposition temperature to modulate film adhesion, it is worth mentioning that the first non-porous layer deposition temperature is specific to this study. Indeed, the formation of a detachable Ge film depends on the ability to form a dense layer while ensuring sufficient porosity is confined within the PGe layer to allow for the formation of pillars with a specific surface coverage during PGe layer recombination. These conditions are strongly dependent on the deposition temperature and rate. The substrate temperature drives PGe layer recombination during deposition. Therefore, it needs to be as low as possible to avoid rapid recombination. However, the deposition rate limits the total time for material deposition, which needs to be as short as possible to accelerate the formation of the dense layer and thus accelerate the confinement of porosity within the detachable layer. In this embodiment, the maximum Ge deposition rate achievable using a solid-state Ge source is approximately 0.5 μm / h, requiring a relatively long deposition time of over 20 minutes to obtain a 200 nm thick first non-porous layer. g At 400°C, this also means a very long annealing time, sufficient for the PGe layer to reorganize, leading to void annihilation and pore filling, potentially resulting in a fully welded and non-detachable film. To avoid this, it is necessary to minimize the thermal budget experienced by the PGe layer during the first non-porous layer period.

[0137] For deposition techniques requiring high substrate temperatures, the solution lies in increasing the deposition rate to minimize annealing time. In fact, a planar SEM analysis of annealing time-dependent PGe layer remodeling was performed at 400°C. The results are as follows... Figure 12A -D is shown.

[0138] It was found that increasing the annealing time to 20 minutes enhanced PGe layer remodeling through the OR phenomenon, resulting in increased pore size. Figure 12A The estimated average pore size of the initial porous structure extracted is approximately 20 nm. Figure 12EAs shown. This value increases monotonically with increasing annealing time, reaching an average value of approximately 80 nm after annealing time of 20 minutes. Figure 12E This behavior enhances Ge diffusion and pore filling (void annihilation) during the formation of the first non-porous layer at 400°C. To limit the effects of PGe layer recombination at relatively high deposition temperatures, the first non-porous layer needs to be deposited at a high deposition rate. For example, using depressurized chemical vapor deposition, Ge deposition rates can easily reach over 36 nm / min at 400°C. Using this deposition rate, the minimum required first non-porous layer thickness of approximately 100 nm can be achieved within 3 minutes. Therefore, it becomes possible to form a germanium film and confine sufficient porosity to ensure a detachable layer.

[0139] In summary, this embodiment highlights the significant impact of deposition parameters on porous structure recombination and, consequently, on the adhesion strength of the germanium film. It was found that increasing the deposition temperature of the first non-porous layer at a low deposition rate prevents film detachment due to the recombination of porous materials and the diffusion of Ge within the pores. AFM analysis revealed a direct correlation between deposition temperature and the surface roughness of the germanium film. This roughness can be significantly reduced to an RMS below 1 nm by a high-temperature annealing step and subsequent deposition of a 1 μm second non-porous layer. To achieve a detachable germanium film with low surface roughness, the deposition temperature of the first non-porous layer should be maintained at approximately 300 °C.

[0140] Furthermore, adjusting the thickness of the PGe layer at an appropriate first non-porous layer deposition temperature provides another method for controlling the adhesion strength of germanium films. The study in this embodiment shows that increasing the PGe layer thickness leads to an overall increase in porosity within the separation layer, thereby reducing the film adhesion strength. This embodiment specifically demonstrates the ability to adjust film adhesion from a state of easy detachment to a fully bonded film. The results presented herein can open new avenues for adjustable film adhesion strength for the detachment of controllable devices.

[0141] Example 2 – Adjusting the initial PGe layer thickness through porous germanium transformation to modify the coupling strength detachable from the germanium film.

[0142] In this embodiment, experimental testing was performed during film fabrication. More specifically, the testing aimed to determine whether the initial PGe layer thickness had any effect on the resulting coupling strength. In these embodiments, fabrication includes the step of creating a PGe layer in a germanium substrate based on the initial PGe layer thickness prior to depositing a first non-porous layer. As discussed, the initial PGe layer thickness can be part of a set of fabrication parameters. In these embodiments, for example, the etching conditions of the germanium substrate can be varied to obtain the initial PGe layer thickness. Figure 10A -E shows the germanium substrates with porous layers of different thicknesses used in these experiments. Figure 10F-J is a cross-sectional view showing the same germanium substrate after a germanium film has been deposited on the corresponding porous layer. As shown, the pillar diameter, pillar height, and pillar density appear to vary with the initial porous layer thickness. These results are... Figure 11A-11D This is illustrated in more detail below. Therefore, in embodiments where the coupling strength indicator indicates weak coupling, the initial PGe layer thickness can be set to 250 nm or more. Conversely, in embodiments where the coupling strength indicator indicates strong coupling, the initial PGe layer thickness can be set to 200 nm or less.

[0143] Example 3 – Changes in coupling strength detached from the germanium film can be achieved through porous germanium transformation and post-deposition annealing temperature adjustment.

[0144] In this embodiment, a method for fabricating a germanium film on a germanium substrate is proposed. The method typically includes a first step of depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature. The method further includes a second step of depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, wherein the germanium film has both the first and second non-porous layers. The method further includes a third step of heating the first and second non-porous layers of germanium, as well as the germanium substrate, to a first annealing temperature and maintaining this temperature for a first time period, the first annealing temperature being higher than the first and second deposition temperatures. This method is commonly referred to as a "post-growth annealing" method.

[0145] In embodiments where a weak coupling is desired between the germanium film and the germanium substrate, the following fabrication parameters are considered. For example, in these embodiments, the first annealing temperature is preferably between 500°C and 725°C. Additionally or alternatively, a porous layer can be prepared or selected to exhibit a porosity between 50% and 55% and a thickness between 300 nm and 400 nm.

[0146] In embodiments where a strong coupling is desired between the germanium film and the germanium substrate, the first annealing temperature is typically between 775°C and 850°C. In some embodiments, the porosity of the porous layer is between 50% and 55%, and the thickness is between 200 nm and 300 nm, which can also facilitate this stronger coupling.

[0147] In an exemplary application where the germanium film is to be used as a substrate for a photovoltaic device, the first annealing temperature is between 650°C and 750°C, and the first time period is between 45 minutes and 75 minutes. These conditions correspond to weak to moderate coupling and have been found to be satisfactory for photovoltaic applications. Furthermore, regarding the porous layer, a porosity between 50% and 55% and a thickness between 200 nm and 300 nm have been found to be satisfactory.

[0148] The methods described above are discussed in the following paragraphs, which explore the effect of post-deposition (or equivalently "post-growth") thermal annealing on the coupling strength of a detachable germanium film supported by nanoscale pillars on a parent germanium substrate. The post-deposition annealing step is sometimes referred to in this disclosure as the "first annealing step." The first annealing step can be defined as a step in film fabrication that includes heating the first and second non-porous layers, as well as the germanium substrate, to a first annealing temperature and maintaining this temperature for a given time period after the deposition of the second non-porous layer. As discussed in more detail below, it has been determined that in embodiments where the coupling strength indicator indicates weak coupling, the first annealing temperature can be set between 500°C and 725°C. In embodiments where the coupling strength indicator indicates strong coupling, the first annealing temperature can be set between 775°C and 850°C. In embodiments where the coupling strength indicator indicates moderate coupling, the first annealing temperature can be set between 725°C and 775°C (excluding the endpoints), but these embodiments may not be preferred. It has been shown that post-deposition heat treatment can effectively engineer film coupling strength by adjusting the pillar density and size. Therefore, tensile testing for separation, SEM imaging, and FEM-based simulations were combined to systematically study the morphological changes of the column-based separation layer and their impact on the coupling strength of the detachable membrane. Furthermore, the fit between simulation and experiment was used to extract the specific fracture strength of the Ge structure used.

[0149] In this embodiment, post-growth engineering of the coupling strength of germanium films on a PGe substrate was explored by inducing morphological changes in the separation layer via thermal budget (TB) control. It was indeed found that the pillars formed during PGe sintering during deposition evolved with post-deposition thermal annealing. Scanning electron microscopy (SEM) analysis of the residues from the broken pillars after detachment showed that the pillar diameter and density could be tuned by thermal annealing. Depending on the post-deposition annealing temperature, the coupling strength of the film could be continuously customized, ranging from 0.5 MPa to up to 3.5 MPa, while ensuring 100% detachment yield. The experimental results have been correlated with finite element modeling (FEM) considering the actual pillar distribution, revealing that pillar size and density are the dominant factors influencing the film coupling strength.

[0150] This study used a p-type (100) oriented Ge substrate, offset 6° in the (111) direction, with a resistivity of 8-30 mΩ·cm. Bipolar electrochemical etching (BEE) was used in an HF:EtOH (4:1;V:V) electrolyte solution at 1 mA·cm⁻¹. -2A uniform PGe layer was prepared on a 100 mm germanium substrate using symmetrical etch / passivation etch current density and a 1 s pulse duration. The resulting PGe layer had a porosity of approximately 53% and a thickness of approximately 230 nm. After BEE, the substrate was rinsed in EtOH and dried under N2. The germanium film was deposited via a two-step process: first, a 200 nm first non-porous layer was deposited at 300 °C, followed by a 700 nm thick second non-porous layer at 450 °C, in a hybrid VG Semicon V90F CBE / MBE reactor. Deposition was carried out under high vacuum (approximately 10... -6 The deposition was performed under Torr conditions using a solid-state Ge source, with the K-cell heated to 1250°C at a deposition rate of approximately 0.5 μm / h. After germanium film deposition, several sections approximately 2 cm thick were allowed to pass through. 2 The samples underwent post-growth heat treatment in a Carbolite tube furnace at temperatures between 650°C and 850°C for 1 hour under an (Ar:H2;90:10) atmosphere. The process was initiated at a heating rate of 25°C / min and then switched to 5°C / min before reaching the target value to avoid overheating. After annealing, the samples were cooled to room temperature. Surface and cross-sectional SEM imaging was performed using a Zeiss LEO1540 XB and a Thermo Scientific Scios 2 Dual Beam SEM tool with an accelerating voltage set to 20 kV. Root mean square (RMS) roughness was measured using atomic force microscopy (AFM) with a Veeco Dimension 3100 and an SSS-NCHR silicon probe. SEM images were processed in ImageJ software to determine crystallite / void size, layer morphology, and thickness.

[0151] The sample was fixed to an aluminum block from both sides of the back of the germanium film and the germanium substrate (using JB Weld 8281) to provide clamping points for the decoupling device. The force required for vertical separation of the thin germanium film from the parent substrate was measured using a conventional tensile testing method at a speed of 0.1 mm / s. The maximum load provided by the device was 600 N. The coupling strength (in MPa) was then obtained by dividing the measured force required for vertical separation by the surface area of ​​the detached film. To simulate the tensile test separation process and study the influence of columnar characteristics on epitaxial layer coupling under quasi-static assumptions, a 3D semi-empirical FEM model was developed using COMSOL Multiphysics (V 6.0, COMSOL AB, Stockholm, Sweden). This model is referred to below as the Random Columnar Distribution (RPD) model. Figure 13AAs illustrated, the RPD model is used to simulate the realistic situation of random distribution of the size and position of the cylinder. To do this, the input geometry is obtained by converting multiple local planar view SEM images into binary format. A uniform axial stress equal to the load limit of the tensile testing apparatus is then applied to the film while the substrate is clamped to simulate the experimental configuration.

[0152] Consider tetrahedral elements and a steady-state solver for mesh generation and solution of the problem. Figure 13B Based on the extraction of the maximum axial stress in the column, the coupling strength was estimated for different RPD model configurations.

[0153] The Ge material used in the simulation has the following properties: Young's modulus 103 GPa, (100) orientation Poisson's ratio 0.26. Here, we will use FEM simulation to determine the fracture strength of the structure used.

[0154] After porosification ( Figure 14A A 200 nm thick first non-porous Ge layer was deposited on top of the PGe layer at a low temperature (300 °C), enabling the deposition of a second non-porous layer at 450 °C without affecting the surface quality of the germanium film. The thermal budget (TB) during the deposition of the first non-porous layer caused the PGe layer to reshape into pillars connecting the germanium film and the germanium substrate, such as... Figure 14B As shown. The formation of independent pillars from a continuous sponge-like porous structure can be attributed to PGe recombination following the Ostwald ripening phenomenon. The resulting pillars have a diameter of 79 nm ± 10 nm and a height of 110 nm, corresponding to a 52% reduction in the total initial thickness of the PGe layer. The RMS surface roughness of the germanium film is approximately 0.7 nm ± 0.3 nm. Figure 14C ).

[0155] To investigate the influence of thermal budget on the morphology of porous microstructures and its relationship with coupling strength, annealing experiments were conducted; the results are reported in Figure 15A In the -E SEM image, a separation layer consisting of well-defined columns can be observed, which remains distinct even after annealing at up to 800℃, and the morphology of the columns has undergone significant morphological changes.

[0156] In fact, as the annealing temperature increases, the overall column size and spacing increase, while the overall density decreases. Meanwhile, for annealing temperatures below 750℃, the average column height decreases slightly by about 10 nm compared to the deposited sample. At 750℃, large submicron to micron-sized columns of various shapes appear, such as... Figure 15C and 16DAs shown, this indicates that more and more small-sized columns are merging, resulting in larger columns with lower density. This trend is further confirmed at higher temperatures (above 750°C), where the separation layer appears to be dominated by large-sized columns with lateral dimensions on the micrometer scale. Furthermore, at these high-temperature annealing temperatures that provide the system with high thermal energy, the inter-column void spaces gradually recombine into larger cavities with more energy-efficient 3D shapes, tending towards spherical voids, such as... Figure 15E As shown.

[0157] Further insights into the quantitative characteristics of the separated layer morphology were obtained through planar SEM imaging. To this end, the germanium film was mechanically detached from the substrate, leaving fractured pillars on the substrate surface, which could be analyzed by planar SEM observation. Complete detachment yield was achieved for structures annealed to 750 °C. Conversely, samples annealed at 800 °C and 850 °C exhibited coupling strengths exceeding the set limit of 4.5 MPa of the tensile testing equipment used, thus the corresponding films could not detach under our experimental conditions. Therefore, for these structures, a rough estimate of the pillar characteristics was made based on SEM cross-sectional imaging. Figure 16A -D shows a planar SEM image of the columnar structure after substrate removal, revealing more details of the columnar spatial and morphological distribution. For more quantitative analysis, these images were analyzed to obtain the columnar distribution, and then the average diameter of each sample column was obtained by fitting a log-normal function, such as... Figure 16E -H is shown.

[0158] The planar view images confirmed the previous assessment of the morphological transformation trend of the cylinders based on cross-sectional SEM images. Indeed, as the annealing temperature increased, the cylinder density decreased, while the average diameter continued to increase, as... Figure 16E As shown in -H. This trend can be understood as the small-sized pillars primarily transforming into supplementary Ge material, effectively supplying the inner surface of the separation layer. This may lead to a slight overall contraction in the observed weak layer height and a relative increase in the pillar diameter. Furthermore, closely spaced pillars may also coalesce, resulting in an observed increase in average diameter, while simultaneously increasing their dimensional dispersion and decreasing their overall density. In fact, a simple correlation between cross-sectional and planar view images reveals two mechanisms dependent on TB. Below 750°C, the weak layer characteristics are dominated by the transformation of small-sized pillars, maintaining a relatively constant height. For annealing temperatures above 750°C, the transformation to stable and sufficiently spaced pillars with larger lateral dimensions, through the transformation of separation voids into more energy-stable faceted 3D voids, leads to the evolution of the separation layer.

[0159] The evolution of column density and average diameter with annealing temperature is as follows: Figure 17AAs shown. Initially, the average diameter of the columns increases slowly with increasing TB, from 79 nm in the grown state to over 251 nm at 750 °C. Then, at 800 °C and 850 °C, we observed a faster increase in column size, reaching a diameter of 1.8 μm, as the voids begin to form faceted 3D features. Furthermore, the column density decreases exponentially with annealing temperature, from 2.6 × 10⁻⁶ in the deposited state to... 9 One column / cm 2 1×10 at 750℃ 8 One column / cm 2 And 1×10 at 850℃ 7 One column / cm 2 The significant morphological transformation of the separation layer induced by this post-growth annealing indicates a substantial impact on its mechanical properties. To evaluate this parameter, we investigated the effect of the separation layer morphology on the coupling strength of the germanium film, derived from the separation force measured using a tensile testing apparatus.

[0160] The average experimental coupling strength as a function of annealing temperature is shown in Figure 17B The results were presented with corresponding error bars. It was found that the coupling strength initially decreased with increasing annealing temperature, reaching a minimum at 700℃, and then monotonically increased with higher annealing temperatures. Furthermore, as previously mentioned, samples annealed at 800℃ and 850℃ did not detach under the conditions of available tensile testing, indicating a coupling strength higher than 4.5 MPa.

[0161] The observed changes in coupling strength can be related to Figure 17A The changes in column size and density are correlated. In fact, the decrease in coupling strength appears to be related to the decrease in column density, rather than to the slight increase in diameter. However, the increase in column size becomes the dominant factor controlling the film coupling strength when the annealing temperature is above 700°C.

[0162] Therefore, depending on the desired application and / or stripping method, finding the correct balance between column width and density is crucial, as excessively high values ​​of either parameter can hinder the stripping process. Thus, careful attention needs to be paid to the interaction between diameter and density to achieve the desired ease of stripping.

[0163] To further evaluate the indicators of the coupling strength between the studied structure and the experiment, FEM simulations based on a random distribution were performed using a realistic description of the self-organizing properties of the cylinder. This was achieved by analyzing planar SEM images (…). Figure 16A -D) is converted to a binary image ( Figure 18A -D) to construct the exact input cylinder geometry for each annealing temperature.

[0164] Given the wide range of available values ​​for the fracture strength of bulk Ge, we use an upper limit (160 MPa) and a lower limit (40 MPa) to determine the simulation range of the membrane coupling strength. Figure 19 The gray area in the figure represents the coupling strength. Interestingly, the calculated coupling strength follows the same trend as the experimental measurements. Furthermore, the average value of the experimentally measured coupling strength lies between the highest and lowest simulated coupling strength values. The best fit between the experimental measurements and the FEM simulation allows the extraction of 88 MPa as the most suitable fracture strength for the bulk Ge material in the studied structure. In fact, as... Figure 19 As shown, the simulated coupling strength perfectly matches the average experimental values, regardless of the annealing conditions (pillar density and size distribution). Since the simulation model does not account for any structural defects that could affect the film coupling strength, the results may indicate a defect-free separation layer. This finding is consistent with our previous study using high-resolution transmission electron microscopy on separation layers with similar nanoscale pillars, showing that no structural defects that could promote separation exist at either pillar interface.

[0165] FEM simulations are based on modeling defect-free structures at the interfaces between the pillar and the film and substrate. The consistency between simulations and experimental measurements makes the studied morphology more likely to be considered a defect-free structure, indicating that coupling variations are determined solely by the evolution of the pillar morphology.

[0166] The difference between the fracture strength of Ge obtained in this work and the reported fracture strength (160 MPa) of polished germanium substrates can be explained by the presence of angles in the structural geometry and the perpendicularity of the pillars to the substrate and germanium film, which weaken the coupling strength and generate fracture seeds.

[0167] To estimate the coupling strength of the undecoupled structure at 800℃ and 850℃, different FEM models were used. Data extracted from cross-sectional images helped create a structure with uniformly distributed columns, where the column diameter was fixed and the column spacing was determined by the measured density. The calculated coupling strengths for 800℃ and 850℃ were 5.8 and 7.3 MPa, respectively. Figure 19 ).

[0168] In summary, this embodiment reports a post-growth engineering modification of the coupling strength of a germanium film on a PGe substrate through a thermal budget-induced separation layer morphology transformation. It was found that the separation layer, formed by pillars connecting the detachable film to the substrate, undergoes different morphological transformations depending on the post-deposition annealing temperature. The results show that the pillar density decreases with increasing TB, while its average diameter increases with increasing TB. The film coupling strength was found to initially decrease with increasing TB within a mechanism dominated by pillar density. However, at higher annealing temperatures, the increase in pillar size and the transformation of cavities enhanced the coupling between the film and its parent substrate. 3D FEM simulations of the film coupling strength were performed using a semi-empirical model and compared with experimental measurements. A bulk fracture strength of 88 MPa was calculated by fitting the empirical data to the FEM model.

[0169] These results highlight the ability to controllably tune film coupling strength post-deposition to achieve the desired ease of detachment required by the chosen device lift-off method. Furthermore, these results allow for the optimization of detachable film deposition steps to tailor the force from which the film can adhere to the substrate based on the allocated TB. These findings pave the way for controlled film detachment, leading to significant progress toward the development of lightweight, low-cost solar cells and optoelectronic devices.

[0170] Example 4 – Results demonstrating the relationship between coupling strength and column surface coverage

[0171] On the other hand, a method for fabricating a germanium film on a germanium substrate has been proposed. This method typically includes a first step in which a first non-porous layer of germanium is deposited onto a PGe layer of the germanium substrate at a first deposition temperature. This deposition seals the pores of the PGe layer, thereby trapping a certain volume of voids within the PGe layer while maintaining the original structure of the pores. Rapid deposition of the first non-porous germanium layer is beneficial for trapping voids. Therefore, the deposition rate of this step is important and can be between 1 nm / min and 20 nm / min, preferably between 1 nm / min and 10 nm / min, and most preferably between 1 nm / min and 5 nm / min. The method includes a second step in which a second non-porous layer of germanium is deposited onto the first non-porous layer at a second deposition temperature higher than the first deposition temperature, resulting in a germanium film having both the first and second non-porous layers. The deposition rate of this second step is irrelevant as it only affects the thickness of the second non-porous germanium layer and not the resulting coupling strength. The method includes a third step in which the original structure of the pores is altered by heating the germanium substrate to a given temperature and maintaining it for a given time period. The change includes transforming the porosity into a plurality of larger cavities that define pillars extending between the germanium substrate and the first non-porous layer. In this respect, the pillars are defined by a pillar surface coverage Cps between 1% and 35%.

[0172] For example, the surface coverage of a column can be given by the following: Among them, Ap i Let represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, and Am represent the total area of ​​the germanium film. The column surface coverage can also be given as follows: Where Dp represents the column density, Ap avg This represents the average cross-sectional area of ​​the column. In some embodiments, the column has a circular shape. Therefore, the average cross-sectional area Ap is... avg can be Given, where D avg This represents the average diameter of the prism. Depending on the specific circumstances and the measurements taken of the prism, one of the equations will be more appropriate.

[0173] Given the above embodiments, applying heat to transform the original morphology / structure of the pores can be done in various ways and achieve similar results. More specifically, the heating step can be performed: 1) during the deposition of the first non-porous germanium layer, ii) after the deposition of the first non-porous germanium layer and before the deposition of the second non-porous germanium layer, iii) during the deposition of the second non-porous germanium layer, iv) after the deposition of the second non-porous germanium layer, or a combination thereof. As more heat is applied to the film, the column surface coverage decreases. In fact, as heat is applied, the microcrystals (i.e., germanium atoms or groups of germanium atoms) gain kinetic energy and vibrate, which tends to cause them to re-aggregate together. Therefore, the column size gradually increases, but the number decreases, which tends to reduce the overall column surface coverage. It has been found that this morphological change can only occur satisfactorily when a sufficient amount of porosity (e.g., air) is captured within the PGe layer through the deposition of the first non-porous germanium layer. The above paragraphs and embodiments illustrate different combinations for achieving a satisfactory porosity transformation.

[0174] Figure 20 Experimental results demonstrating the relationship between coupling strength and column surface coverage according to one embodiment are shown. As described above, columns obtained by reorganizing the membrane through a porous structure are attached to the substrate. The properties of the columns vary with initial parameters such as PGe structure thickness and porosity, as well as the applied thermal budget (the applied heat). Adhesion is directly affected by the column properties, typically expressed by parameters such as the average column diameter and column density. Larger columns and / or higher density impart high adhesion to the membrane, while smaller columns and / or lower density reduce adhesion and promote detachment. An increase in the average column diameter is generally accompanied by a decrease in column density, which can be explained by the OR phenomenon. Column surface coverage is a parameter combining the average column diameter and column density. It represents the percentage of the transverse surface covered by the columns. Figure 20As shown, the coupling strength was found to vary linearly with the surface coverage of the pillar. As also shown, within the scope of relevant applications, the germanium film is coupled to the germanium substrate with a coupling strength ranging from 0.25 MPa to 4.5 MPa.

[0175] In applications seeking weak coupling, the column surface coverage is between 1% and 5%, and the coupling strength is between 0.25 MPa and 0.75 MPa. Besides the methods described above, such weak coupling can be achieved using a porous layer with a thickness between 300 nm and 500 nm. In some embodiments, the porosity of the porous layer is between 50% and 60%. A PGe layer with greater thickness and / or higher porosity can help trap a larger amount of voids within the PGe layer, which in turn can help facilitate a lower column surface coverage.

[0176] In applications seeking moderate coupling, the surface coverage of the column is typically between 5% and 15%, and the coupling strength is between 0.75 MPa and 2.25 MPa. In these embodiments, the thickness of the PGe layer is between 200 nm and 300 nm, and the porosity is between 30% and 50%.

[0177] In applications where strong coupling is preferred, the column surface coverage can be between 20% and 35%, and the coupling strength can be between 2.75 MPa and 4.5 MPa. In these embodiments, the thickness of the PGe layer is between 100 nm and 200 nm, and the porosity is between 20% and 30%. In fact, having a thinner PGe layer or a porous layer with reduced porosity can result in fewer voids being trapped within the porous layer during the deposition of the first non-porous germanium layer, which in turn can promote a higher column surface coverage.

[0178] It is understood that the embodiments described above and illustrated are merely exemplary. For example, in some embodiments, the first and second deposition steps are performed sequentially in a manner that mimics a step-like function of temperature increase. However, in some embodiments, the first and second deposition steps may be performed continuously, wherein the temperature increases smoothly and continuously from the first deposition temperature to the second deposition temperature. It should be noted that while this description emphasizes germanium as a semiconductor material, it is contemplated that the methods and systems described herein can be applied to any other semiconductor material. Examples of such semiconductor materials may include, but are not limited to, silicon (Si), indium tin oxide (ITO), zinc oxide (ZnO), III-V group semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium gallium phosphide (GaInP), aluminum gallium arsenide phosphide (AlGaAsP), indium gallium arsenide phosphide (InGaAsP), aluminum gallium indium phosphide (AlGaInP), aluminum gallium indium phosphide (InAlGaP), aluminum gallium indium phosphide (InGaAlP), aluminum gallium indium phosphide (AlInGaP), III-V group heterostructures such as gallium nitride on silicon (GaN / Si), aluminum nitride on silicon (AlN / Si), gallium arsenide on silicon (GaAs / Si), gallium phosphide on silicon (GaP / Si), indium gallium arsenide on silicon (InGaAs / Si), aluminum indium nitride on silicon (AlInN / Si), gallium indium nitride on silicon (GaInN / Si), and other suitable types of semiconductor heterostructures. Semiconductor materials can be single-crystal, polycrystalline, etc. It should be noted that the ranges for deposition temperature, annealing temperature, and their corresponding rates and durations are merely exemplary, as they can vary depending on the type of manufacturing machine or process used. The scope is indicated by the appended claims. Claims (as amended under Article 19 of the Treaty) 1. A method of fabricating a germanium film on a germanium substrate, the method comprising: selecting a coupling strength indicator, the coupling strength indicator indicating a force that decouples the germanium film from the germanium substrate when applied to the germanium film; determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference sets of manufacturing parameters with corresponding reference coupling strength indicators, the set of manufacturing parameters including at least a first deposition temperature and a second deposition temperature above the first deposition temperature; and fabricating the germanium film on the germanium substrate based on the set of manufacturing parameters, the fabrication comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at the first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at the second deposition temperature above the first deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer. 2. The method of claim 1, further comprising applying a decoupling force to the germanium film, the decoupling force being greater than the force of the coupling strength indicator, thereby obtaining a decoupled germanium film and a germanium substrate having a detached surface. 3. The method of claim 1 or 2, further comprising cleaning the detached surface of the germanium substrate, forming another porous layer in the germanium substrate, and forming a second germanium film on the germanium substrate. 4. The method of any one of claims 1 to 3, wherein when the coupling strength indicator indicates weak coupling, the first deposition temperature is set between 275°C and 325°C, and when the coupling strength indicator indicates strong coupling, the first deposition temperature is set between 350°C and 400°C. 5. The method of any one of claims 1 to 4, wherein when the coupling strength indicator indicates weak coupling, the second deposition temperature is set between 525°C and 575°C, and when the coupling strength indicator indicates strong coupling, the second deposition temperature is set between 425°C and 475°C. 6. The method of any one of claims 1 to 5, wherein the manufacturing parameter set has a first annealing temperature, the manufacturing comprising: after the deposition of the second non-porous layer, heating the first non-porous layer and the second non-porous layer and the germanium substrate to the first annealing temperature and sustaining it for a given period of time, preferably between 45 minutes and 75 minutes. 7. The method of claim 6, wherein when the coupling strength indicator indicates weak coupling, the first annealing temperature is set between 500°C and 725°C, and when the coupling strength indicator indicates strong coupling, the first annealing temperature is set between 775°C and 850°C. 8. The method of any one of claims 1 to 7, wherein the manufacturing parameter set includes at least one of an initial porous layer thickness and an initial porous layer porosity, the manufacturing comprising: fabricating the porous layer in the germanium substrate based on at least one of the initial porous layer thickness and the initial porous layer porosity prior to depositing the first non-porous layer. 9. The method of claim 8, wherein when the coupling strength indicator indicates weak coupling, the initial porous layer thickness is set between 250 nm and 400 nm, and when the coupling strength indicator indicates strong coupling, the initial porous layer thickness is set between 100 nm and 200 nm. 10. The method of claim 8, wherein when the coupling strength indicator indicates weak coupling, the initial porous layer porosity is between 50% and 60%, and when the coupling strength indicator indicates strong coupling, the initial porous layer porosity is between 20% and 50%. 11. The method of any one of claims 1 to 10, wherein the deposition step forms a plurality of pillars extending within the porous layer of the germanium substrate, and the selected coupling strength indicator includes at least one of a pillar size value indicating average pillar size, a pillar height value indicating average pillar height, and a pillar density value indicating pillar density. 12. A system for fabricating a germanium film on a germanium substrate, the system comprising: a computer receiving a coupling strength indicator indicating a force that, when applied to the germanium film, decouples the germanium film from the germanium substrate; the computer determining a set of manufacturing parameters based on the coupling strength indicator using reference data that associates a plurality of reference sets of manufacturing parameters with corresponding reference coupling strength indicators, the set of manufacturing parameters including at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature; and a manufacturing apparatus communicatively coupled to the computer, the manufacturing apparatus being configured... To fabricate the germanium film on the germanium substrate based on the aforementioned set of manufacturing parameters, the fabrication includes: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and a decoupling device communicatively coupled to the computer, the decoupling device being configured to apply a decoupling force to the germanium film, the decoupling force being greater than the force of the coupling strength indicator, thereby decoupling the germanium film from the germanium substrate. 13. The system of claim 12, wherein the decoupling device is configured to pull the germanium film from the germanium substrate. 14. The system of claim 12 or 13, wherein the reference data is stored on the computer-accessible non-transitory computer-readable storage. 15. A method of fabricating a germanium film on a germanium substrate, the method comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature, the deposition of the first non-porous layer sealing the pores of the porous layer to capture a volume of voids within the porous layer while maintaining the original structure of the pores; depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature above the first deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and altering the original structure of the pores by heating the germanium substrate to a given temperature and sustaining it for a given time period, the alteration comprising reorganizing the pores into a plurality of larger cavities, wherein a plurality of pillars extending between the germanium substrate and the first non-porous layer are interspersed in the plurality of larger cavities, the plurality of pillars having a pillar surface coverage Cps between 1% and 35%, the pillar surface coverage being given by: Among them, Ap i Let N represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, Am represent the total area of ​​the germanium film, Dp represent the column density, and Ap represent the cross-sectional area of ​​the i-th column. avg This represents the average cross-sectional area of ​​the column. 16. The method of claim 15, wherein the germanium film is coupled to the germanium substrate with a coupling strength between 0.25 MPa and 4.5 MPa. 17. The method of claim 16, wherein the surface coverage of the column is between 1% and 5%, and the coupling strength is between 0.25 MPa and 0.75 MPa. 18. The method of claim 17, wherein the thickness of the porous layer is between 300 nm and 500 nm. 19. The method of claim 17, wherein the porosity of the porous layer is between 50% and 60%. 20. The method of claim 16, wherein the surface coverage of the column is between 5% and 15%, and the coupling strength is between 0.75 MPa and 2.25 MPa. 21. The method of claim 20, wherein the thickness of the porous layer is between 200 nm and 300 nm. 22. The method of claim 20, wherein the porosity of the porous layer is between 30% and 50%. 23. The method of claim 16, wherein the surface coverage of the column is between 20% and 35%, and the coupling strength is between 2.75 MPa and 4.5 MPa. 24. The method of claim 23, wherein the thickness of the porous layer is between 100 nm and 200 nm. 25. The method of claim 23, wherein the porosity of the porous layer is between 20% and 30%. 26. The method of any one of claims 15 to 25, wherein the heating is performed in at least one of the following cases: i) after the deposition of the first non-porous germanium layer and before the deposition of the second non-porous germanium layer, ii) during the deposition of the second non-porous germanium layer, and iii) after the deposition of the second non-porous germanium layer. 27. The method of any one of claims 15 to 26, wherein the given time period is between 45 minutes and 75 minutes.

Claims

1. A method for fabricating a germanium film on a germanium substrate, the method comprising: Select a coupling strength indicator that indicates the force that causes the germanium film to decouple from the germanium substrate when applied to the germanium film; Based on the coupling strength indicator, a manufacturing parameter set is determined using reference data that associates a plurality of reference manufacturing parameter sets with corresponding reference coupling strength indicators, the manufacturing parameter set including at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature; And fabricating the germanium film on the germanium substrate based on the fabrication parameter set, the fabrication comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at the first deposition temperature; And at a second deposition temperature higher than the first deposition temperature, a second non-porous layer of germanium is deposited onto the first non-porous layer, the germanium film having the first non-porous layer and the second non-porous layer.

2. The method of claim 1, further comprising applying a decoupling force to the germanium film, the decoupling force being greater than the force of the coupling strength indicator, thereby obtaining a decoupled germanium film and a germanium substrate having a detached surface.

3. The method of claim 1 or 2, further comprising cleaning the detached surface of the germanium substrate, forming another porous layer in the germanium substrate, and forming a second germanium film on the germanium substrate.

4. The method of any one of claims 1 to 3, wherein when the coupling strength indicator indicates weak coupling, the first deposition temperature is set between 275°C and 325°C, and when the coupling strength indicator indicates strong coupling, the first deposition temperature is set between 350°C and 400°C.

5. The method of any one of claims 1 to 4, wherein when the coupling strength indicator indicates weak coupling, the second deposition temperature is set between 525°C and 575°C, and when the coupling strength indicator indicates strong coupling, the second deposition temperature is set between 425°C and 475°C.

6. The method of any one of claims 1 to 5, wherein the manufacturing parameter set has a first annealing temperature, and the manufacturing comprises: After the deposition of the second non-porous layer, the first non-porous layer, the second non-porous layer, and the germanium substrate are heated to the first annealing temperature and maintained for a given period of time, preferably between 45 minutes and 75 minutes.

7. The method of claim 6, wherein when the coupling strength indicator indicates weak coupling, the first annealing temperature is set between 500°C and 725°C, and when the coupling strength indicator indicates strong coupling, the first annealing temperature is set between 775°C and 850°C.

8. The method of any one of claims 1 to 7, wherein the manufacturing parameter set includes at least one of an initial porous layer thickness and an initial porous layer porosity, the manufacturing comprising: Prior to depositing the first non-porous layer, the porous layer is fabricated in the germanium substrate based on at least one of the initial porous layer thickness and the initial porous layer porosity.

9. The method of claim 8, wherein when the coupling strength indicator indicates weak coupling, the initial porous layer thickness is set between 250 nm and 400 nm, and when the coupling strength indicator indicates strong coupling, the initial porous layer thickness is set between 100 nm and 200 nm.

10. The method of claim 8, wherein when the coupling strength indicator indicates weak coupling, the initial porous layer porosity is between 50% and 60%, and when the coupling strength indicator indicates strong coupling, the initial porous layer porosity is between 20% and 50%.

11. The method of any one of claims 1 to 10, wherein the deposition step forms a plurality of pillars extending within the porous layer of the germanium substrate, and the selected coupling strength indicator includes at least one of a pillar size value indicating average pillar size, a pillar height value indicating average pillar height, and a pillar density value indicating pillar density.

12. A system for fabricating a germanium film on a germanium substrate, the system comprising: A computer that receives a coupling strength indicator, the coupling strength indicator indicating the force that decouples the germanium film from the germanium substrate when applied to the germanium film; The computer determines a set of manufacturing parameters based on the coupling strength indicator using reference data that associates multiple sets of reference manufacturing parameters with corresponding reference coupling strength indicators. The set of manufacturing parameters includes at least a first deposition temperature and a second deposition temperature higher than the first deposition temperature. A manufacturing apparatus communicatively coupled to the computer, the manufacturing apparatus being configured to manufacture the germanium film on the germanium substrate based on the manufacturing parameter set, the manufacturing comprising: depositing a first non-porous layer of germanium onto a porous layer of the germanium substrate at a first deposition temperature; and depositing a second non-porous layer of germanium onto the first non-porous layer at a second deposition temperature, the germanium film having the first non-porous layer and the second non-porous layer; and a decoupling device communicatively coupled to the computer, the decoupling device being configured to apply a decoupling force to the germanium film, the decoupling force being greater than the force of the coupling strength indicator, thereby decoupling the germanium film from the germanium substrate.

13. The system of claim 12, wherein the decoupling device is configured to pull the germanium film from the germanium substrate.

14. The system of claim 12 or 13, wherein the reference data is stored on the computer-accessible non-transitory computer-readable storage.

15. A method for fabricating a germanium film on a germanium substrate, the method comprising: At a first deposition temperature, a first non-porous layer of germanium is deposited onto the porous layer of the germanium substrate; At a second deposition temperature higher than the first deposition temperature, a second non-porous layer of germanium is deposited on the first non-porous layer, and the germanium film has the first non-porous layer and the second non-porous layer; After the deposition of the first non-porous layer and the deposition of the second non-porous layer, the first non-porous layer and the second non-porous layer of germanium and the germanium substrate are heated to a first annealing temperature and maintained for a first time period, wherein the first annealing temperature is higher than the first deposition temperature and the second deposition temperature.

16. The method of claim 15, wherein the first annealing temperature is between 500°C and 725°C.

17. The method of claim 16, wherein the porosity of the porous layer is between 50% and 55%, and the thickness is between 300 nm and 400 nm.

18. The method of claim 15, wherein the first annealing temperature is between 775°C and 850°C.

19. The method of claim 18, wherein the porosity of the porous layer is between 50% and 55%, and the thickness is between 200 nm and 300 nm.

20. The method of any one of claims 15 to 19, wherein the first annealing temperature is between 650°C and 750°C, the first time period is between 45 minutes and 75 minutes, the porosity of the porous layer is between 50% and 55%, and the thickness of the porous layer is between 200 nm and 300 nm.

21. A method for fabricating a germanium film on a germanium substrate, the method comprising: At a first deposition temperature, a first non-porous layer of germanium is deposited onto a porous layer of the germanium substrate. The deposited first non-porous layer seals the pores of the porous layer, thereby capturing a certain volume of voids within the porous layer while maintaining the original structure of the pores. At a second deposition temperature higher than the first deposition temperature, a second non-porous layer of germanium is deposited onto the first non-porous layer. The germanium film has the first non-porous layer and the second non-porous layer. The original structure of the pores is altered by heating the germanium substrate to a given temperature and maintaining it for a given time period. This alteration includes reorganizing the pores into a plurality of larger cavities, in which a plurality of pillars extending between the germanium substrate and the first non-porous layer are interspersed. The pillars have a pillar surface coverage Cps between 1% and 35%, the pillar surface coverage being given by: Among them, Ap i Let N represent the cross-sectional area of ​​the i-th column, N represent the total number of columns, Am represent the total area of ​​the germanium film, Dp represent the column density, and Ap represent the cross-sectional area of ​​the i-th column. avg This represents the average cross-sectional area of ​​the column.

22. The method of claim 21, wherein the germanium film is coupled to the germanium substrate with a coupling strength between 0.25 MPa and 4.5 MPa.

23. The method of claim 22, wherein the surface coverage of the column is between 1% and 5%, and the coupling strength is between 0.25 MPa and 0.75 MPa.

24. The method of claim 23, wherein the thickness of the porous layer is between 300 nm and 500 nm.

25. The method of claim 23, wherein the porosity of the porous layer is between 50% and 60%.

26. The method of claim 22, wherein the surface coverage of the column is between 5% and 15%, and the coupling strength is between 0.75 MPa and 2.25 MPa.

27. The method of claim 26, wherein the thickness of the porous layer is between 200 nm and 300 nm.

28. The method of claim 26, wherein the porosity of the porous layer is between 30% and 50%.

29. The method of claim 22, wherein the surface coverage of the column is between 20% and 35%, and the coupling strength is between 2.75 MPa and 4.5 MPa.

30. The method of claim 29, wherein the thickness of the porous layer is between 100 nm and 200 nm.

31. The method of claim 29, wherein the porosity of the porous layer is between 20% and 30%.

32. The method of any one of claims 21 to 31, wherein the heating is performed in at least one of the following cases: i) after the deposition of the first non-porous germanium layer and before the deposition of the second non-porous germanium layer, ii) during the deposition of the second non-porous germanium layer, and iii) after the deposition of the second non-porous germanium layer.

33. The method of any one of claims 21 to 32, wherein the given time period is between 45 minutes and 75 minutes.

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