Method for growing doped gallium oxide thin film on homogeneous substrate and photoelectric detector

Abstract

The invention provides a method for growing a doped gallium oxide thin film on a homogeneous substrate and a photoelectric detector. The invention discloses a method for growing a gallium oxide-doped thin film on a homogeneous substrate. The method comprises the following steps: epitaxially growing a gallium oxide thin film on a gallium oxide substrate doped with a target doping element; and annealing the gallium oxide substrate and the gallium oxide thin film, so that the target doping element is diffused into the gallium oxide thin film from the gallium oxide substrate, and the doped gallium oxide thin film is obtained.

Description

Technical Field

[0001] The present invention relates to the field of thin films, and in particular, to a method for growing doped gallium oxide thin films on a homogeneous substrate and a photodetector. Background Art

[0002] Gallium oxide (Ga2O3) is a semiconductor material with an ultra-wide bandgap. Its bandgap is 4.8 eV, and the theoretical critical breakdown field strength is about 8 MV / cm. The above properties make it have excellent performance in the field of high-voltage (about greater than 1000 V) and high-power (several kilowatts and above) electronic devices. Gallium oxide is also considered an ideal candidate material for photodetectors (such as ultraviolet or X-ray photodetectors).

[0003] When doping gallium oxide thin films according to the current doping methods, there are many lattice defects generated.

[0004] Therefore, a new method for growing doped gallium oxide thin films is needed to improve the above problems. Summary of the Invention

[0005] In view of this, the present invention provides a method for growing doped gallium oxide thin films on a homogeneous substrate and a photodetector, in an attempt to solve or at least alleviate at least one of the above problems.

[0006] According to one aspect of the present invention, there is provided a method for growing doped gallium oxide thin films on a homogeneous substrate, including: epitaxially growing a gallium oxide thin film on a gallium oxide substrate doped with a target doping element; annealing the gallium oxide substrate and the gallium oxide thin film so that the target doping element diffuses from the gallium oxide substrate into the gallium oxide thin film to obtain a doped gallium oxide thin film.

[0007] Optionally, in the method according to the present invention, the step of epitaxially growing a gallium oxide thin film on a gallium oxide substrate doped with a target doping element includes: epitaxially growing a gallium oxide thin film on the gallium oxide substrate by metalorganic chemical vapor deposition.

[0008] Optionally, in the method according to the present invention, when epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the growth temperature is 500 - 900 °C, and the chamber pressure is 10 - 200 Torr.

[0009] Optionally, in the method according to the present invention, when epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the gallium source flow rate is 10 - 300 sccm, and the oxygen source flow rate is 200 - 5000 sccm.

[0010] Optionally, in the method according to the present invention, when epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the tray rotation speed is 0 - 240 rpm.

[0011] Optionally, in the method according to the present invention, when annealing the gallium oxide substrate and the gallium oxide thin film, the annealing temperature is 800 - 1100 °C, and the annealing time is 1 - 15 min.

[0012] Optionally, in the method according to the present invention, the thickness of the gallium oxide thin film is 1 - 2000 nm.

[0013] Optionally, in the method according to the present invention, it further includes: successively cleaning the initial gallium oxide substrate with an organic solvent, a piranha solution, and BOE to obtain the gallium oxide substrate.

[0014] Optionally, in the method according to the present invention, the target doping element includes at least one of iron, zinc, copper, magnesium, and aluminum.

[0015] According to a second aspect of the present invention, there is provided a photodetector, including: a gallium oxide substrate; a doped gallium oxide thin film on the gallium oxide substrate; and a metal electrode disposed on the surface of the doped gallium oxide thin film.

[0016] In the method for growing a doped gallium oxide thin film on a homogeneous substrate of the present invention, a homogeneous substrate, that is, a gallium oxide substrate, is used. Not only is the gallium oxide substrate doped with the target doping element used as the only impurity source, but also the lattice mismatch degree between the substrate and the gallium oxide thin film can be reduced. Subsequently, the gallium oxide substrate and the gallium oxide thin film are annealed, and the target doping element is controlled to diffuse upward from the gallium oxide substrate into the gallium oxide thin film through the annealing process, while also avoiding the damage to the lattice caused by the ion implantation method.

[0017] Furthermore, since the thin film grown by the present invention has few lattice defects and a low background carrier concentration, the dark current of the photodetector prepared from the doped gallium oxide thin film is small, the response is fast, and the performance is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0019] Figure 1 Shows a schematic diagram of a method 100 for growing a doped gallium oxide thin film on a homogeneous substrate according to an embodiment of the present invention;

[0020] Figure 2 Shows a schematic diagram of a transmission electron microscope image of a doped gallium oxide thin film according to an embodiment of the present invention;

[0021] Figure 3 Shows a schematic diagram of a photodetector according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0023] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprising", "including", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0025] In cases where expressions such as "at least one of A, B, and C, etc." are used, generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0026] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged, and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary, and in practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0027] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element can be directly on the other layer / element, or there can be an intermediate layer / element between them. Additionally, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element can be "under" the other layer / element.

[0028] Five crystal phases of gallium oxide materials have been discovered, including α, β, γ, δ, and ε; among them, the monoclinic β-phase Ga2O3 is the most stable. The β-Ga2O3 material has shown intrinsic n-type conductivity when undoped; intrinsic defects such as oxygen vacancies or gallium interstitials are easily formed in its lattice structure, so problems such as large dark current and obvious persistent photoconductivity effect occur. A large dark current refers to the phenomenon that the background current generated under dark conditions significantly exceeds the normal level. The reasons for the large dark current include: lattice defects or impurities in the semiconductor provide donor energy levels and ionize a large number of free electrons at room temperature, increasing the dark current. The persistent photoconductivity effect refers to the physical phenomenon that the conductivity or photocurrent of the material can still remain at a high level for a long time after the light illumination stops. The possible reasons for the persistent photoconductivity effect include carrier traps caused by crystal defects and impurity atoms, which prolong the lifetime of non-equilibrium carriers.

[0029] To solve problems such as large dark current and obvious persistent photoconductivity effect, it is necessary to select appropriate acceptor impurities for compensating doping of gallium oxide materials. One doping method is doping by ion implantation; this method of implanting specific dopants will cause damage to gallium oxide crystals and there are many lattice defects, which in turn leads to poor performance of photodetectors prepared with this thin film.

[0030] Considering that the lattice mismatch is relatively high when growing gallium oxide thin films using a hetero-substrate, a method for growing doped gallium oxide thin films on a homo-substrate is proposed. Figure 1 FIG. shows a schematic diagram of a method 100 for growing doped gallium oxide thin films on a homo-substrate according to an embodiment of the present invention. As Figure 1 shown, method 100 starts from step 110, and a gallium oxide thin film is epitaxially grown on a gallium oxide substrate doped with a target doping element.

[0031] According to one embodiment, the gallium oxide substrate is obtained from an initial gallium oxide substrate. The initial gallium oxide substrate is a gallium oxide substrate doped with a target doping element that has not been cleaned and dried. First, the initial gallium oxide substrate is sequentially cleaned with an organic solvent, a piranha solution, and a BOE solution.

[0032] According to one embodiment, when performing the organic solvent cleaning, the organic solvent may include at least one of acetone (CH3COCH3), ethanol (C2H5OH), isopropanol ((CH3)2CO), and NMP (N-methylpyrrolidone). The cleaning time for each organic solvent can be more than 1 minute.

[0033] According to an embodiment of the present invention, when performing the organic solvent cleaning, acetone and isopropanol are sequentially used for cleaning. The present invention does not limit the specific cleaning method, such as ultrasonic cleaning with acetone for 10 minutes and then ultrasonic cleaning with isopropanol for 10 minutes.

[0034] According to an embodiment of the present invention, when performing piranha solution cleaning, the piranha solution can be used for 15 minutes. The piranha solution refers to a mixture of concentrated sulfuric acid and 30% hydrogen peroxide.

[0035] According to an embodiment of the present invention, when performing BOE cleaning, the BOE can be used for 30 minutes. BOE refers to Buffered Oxide Etch.

[0036] According to an embodiment of the present invention, for the initial gallium oxide substrate after BOE cleaning, it is rinsed clean with deionized water.

[0037] According to an embodiment of the present invention, after rinsing the initial gallium oxide substrate with deionized water, it is dried. The specific drying method can be to dry it with nitrogen to obtain a gallium oxide substrate on which a gallium oxide thin film can be grown.

[0038] According to an embodiment of the present invention, the gallium oxide material used as the substrate in the present invention can adopt the (010) crystal plane.

[0039] According to an embodiment, the target doping elements of the gallium oxide substrate include at least one of iron, zinc, copper, magnesium, and aluminum.

[0040] According to an embodiment of the present invention, the substrate used for growing the gallium oxide thin film in the present invention is a (010) crystal plane, iron-doped β-type gallium oxide single crystal substrate.

[0041] According to an embodiment of the present invention, metalorganic chemical vapor deposition (MOCVD) is used to epitaxially grow a gallium oxide thin film on a gallium oxide substrate.

[0042] According to an embodiment, when using MOCVD to epitaxially grow a gallium oxide thin film, the growth temperature is 500 - 900 °C, and the chamber pressure is 10 - 200 Torr. The chamber pressure is the growth pressure of the gallium oxide thin film in the reaction chamber.

[0043] According to an embodiment of the present invention, when using MOCVD to epitaxially grow a gallium oxide thin film, the growth temperature is 830 °C, and the chamber pressure is 60 Torr.

[0044] According to an embodiment, when using MOCVD to epitaxially grow a gallium oxide thin film, the gallium source flow rate is 10 - 300 sccm, and the oxygen source flow rate is 200 - 5000 sccm.

[0045] According to one embodiment, when growing gallium oxide thin films by MOCVD epitaxy, the gallium source used includes trimethylgallium ((CH3)3Ga) or triethylgallium (Ga(C2H5)3); the oxygen source used includes at least one of oxygen, ozone, nitric oxide, nitrogen dioxide, dinitrogen monoxide, and oxygen plasma.

[0046] According to an embodiment of the present invention, when growing gallium oxide thin films by MOCVD epitaxy, triethylgallium is used as the gallium source with a flow rate of 70 sccm; oxygen is used as the oxygen source with a flow rate of 1000 sccm. The present invention does not limit the specific gallium source and gallium source flow rate, or the oxygen source and oxygen source flow rate; specific parameters can be set according to the phase, composition stoichiometric ratio, etc. of the desired gallium oxide material to be grown.

[0047] According to an embodiment of the present invention, when growing gallium oxide thin films by MOCVD epitaxy, the tray rotation speed can be set to 0 - 240 rpm.

[0048] According to another embodiment of the present invention, when growing gallium oxide thin films by MOCVD epitaxy, the tray rotation speed can be set to 60 rpm, and the growth time is 30 min.

[0049] Subsequently, step 120 is executed to anneal the gallium oxide substrate and the gallium oxide thin film, so that the target doping element diffuses from the gallium oxide substrate into the gallium oxide thin film to obtain a doped gallium oxide thin film.

[0050] The current heterosubstrate used has a relatively high lattice mismatch with the grown thin film. The lattice mismatch is used to quantify the degree of difference in lattice constants between two materials. The lattice mismatch affects the epitaxial growth of crystals, generates a large number of defects in the epitaxial layer, and even makes it impossible to grow single crystals, affecting the performance and lifespan of the device. Therefore, in the method for growing doped gallium oxide thin films according to this embodiment, a homo-substrate, i.e., a gallium oxide substrate, is used. Not only is the gallium oxide substrate doped with the target doping element used as the only impurity source, but it can also reduce the lattice mismatch between the homo-substrate and the gallium oxide thin film.

[0051] Furthermore, annealing the gallium oxide substrate and the gallium oxide thin film controls the upward diffusion doping of the target doping element from the gallium oxide substrate into the gallium oxide thin film through the annealing process, while also avoiding damage to the lattice caused by the ion implantation method. During the thin film growth process, a small portion of iron ions in the substrate will diffuse into the gallium oxide thin film, but the doping amount in this process cannot meet the predetermined requirements. Therefore, subsequent annealing steps are needed to further promote the upward diffusion of iron ions and the uniform distribution of iron ions in the gallium oxide thin film. The method adopted by the present invention has a simple and stable process, small damage to the crystal, low cost, and does not require an external doping source.

[0052] The doped gallium oxide thin film grown by the present invention has few impurities, high crystal purity, and has undergone annealing treatment, so the film quality is relatively high. The background carrier concentration of the doped gallium oxide thin film grown by the present invention is low. The background carrier concentration refers to the number density of free electrons or holes in a semiconductor material that are not affected by an external electric field. The background carrier concentration is related to the doping concentration, lattice defects, etc. Since the grown gallium oxide thin film is doped with a target doping element (such as Fe), compensation doping is performed on the gallium oxide thin film, reducing the background carrier concentration; moreover, lattice damage is avoided during doping, and no other impurities are introduced, so the background carrier concentration is low.

[0053] According to one embodiment, when annealing the gallium oxide substrate and the gallium oxide thin film, the annealing temperature is generally higher than the growth temperature of the gallium oxide thin film, the annealing temperature is 800 - 1100 °C, and the annealing time is 1 - 15 min; under such annealing conditions, the upward diffusion of iron ions and the uniform distribution of iron ions in the gallium oxide thin film can be promoted.

[0054] According to an embodiment of the present invention, when annealing the gallium oxide substrate and the gallium oxide thin film, the annealing temperature is 900 degrees Celsius, and the annealing time is 3 - 5 min.

[0055] According to another embodiment of the present invention, in an RTP (Rapid Thermal Processing) device, the annealing temperature is set to 950 °C, and the gallium oxide substrate and the gallium oxide thin film are annealed for 5 min in an oxygen atmosphere to obtain a doped gallium oxide thin film. The RTP device can be specifically implemented as a rapid annealing furnace; the gallium oxide substrate can be specifically implemented as an iron-doped gallium oxide substrate; the grown doped gallium oxide thin film can be specifically implemented as an iron-doped gallium oxide thin film.

[0056] According to one embodiment, when annealing the gallium oxide substrate and the gallium oxide thin film, a suitable gas atmosphere is used to promote the upward doping of impurity ions from the substrate and their uniform distribution in the doped gallium oxide thin film. When annealing the gallium oxide substrate and the gallium oxide thin film, it can be carried out in a vacuum environment or using a gas atmosphere, including one of air, nitrogen, and oxygen.

[0057] According to an embodiment of the present invention, the annealing treatment can be carried out in an oxygen gas atmosphere.

[0058] According to an embodiment of the present invention, when annealing the gallium oxide substrate and the gallium oxide thin film, the annealing treatment can be directly carried out in the reaction chamber of MOCVD; it can also be annealed outside the reaction chamber after sampling. The present invention does not limit the specific annealing treatment method.

[0059] According to an embodiment of the present invention, the thickness of the gallium oxide thin film grown on the substrate can be achieved to be 1 - 2000 nm.

[0060] Figure 2 The schematic diagram of the transmission electron microscope image of the doped gallium oxide thin film according to an embodiment of the present invention is shown. From Figure 2 it can be seen that the film quality of the prepared doped gallium oxide thin film is relatively high.

[0061] According to an embodiment of the present invention, the present invention also prepares a photodetector based on the prepared doped gallium oxide thin film. Figure 3 The schematic diagram of the photodetector according to an embodiment of the present invention is shown. As Figure 3 shown, the photodetector includes a gallium oxide substrate 310, a doped gallium oxide thin film 320 on the gallium oxide substrate, and a metal electrode disposed on the surface of the doped gallium oxide thin film.

[0062] The doped gallium oxide thin film 320 is prepared by the method 100 for growing a doped gallium oxide thin film on a homogeneous substrate according to an embodiment of the present invention. Since the prepared gallium oxide thin film of the present invention has few film lattice defects and a low background carrier concentration, the dark current of the photodetector prepared based on the doped gallium oxide thin film is small, the response is fast, and the performance is relatively high. Figure 3 The shown metal electrode is an interdigital electrode 330. Figure 3 The implementation manner of the shown metal electrode is only exemplary, and the present invention does not limit the specific implementation manner of the metal electrode.

[0063] According to an embodiment, the metal electrode disposed on the doped gallium oxide thin film can be specifically implemented as at least one of a Ti / Au structure, a Ti / Al / Ni / Au structure, a Cr / Au structure, Ag, In, Al, indium tin oxide (ITO), a Ni / Au structure, Pt, PtO, Au, or graphene. The metal electrode can be prepared by an electron beam evaporation or magnetron sputtering process.

[0064] According to an embodiment, the metal electrode can be specifically implemented as at least one of a square electrode, a circular electrode, an interdigital electrode, or a polygonal electrode.

[0065] According to an embodiment of the present invention, the metal electrode is a Ti / Al / Ni / Au structure from bottom to top, that is, the metal electrode is Ti, Al, Ni, and Au in sequence from bottom to top. Among them, the thicknesses of Ti, Al, Ni, and Au are 20 nm, 100 nm, 60 nm, and 80 nm respectively. To promote the ohmic contact between the metal electrode and the doped gallium oxide thin film, in the lithography process, after the photoresist is peeled off, the photodetector is annealed in a nitrogen atmosphere at a temperature of 470 °C for 1 min to obtain the final device.

[0066] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur in a different order than that noted in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram or flowchart, and combinations of blocks in the block diagram or flowchart, can be implemented by a dedicated hardware-based system that performs the specified functions or operations, or by a combination of dedicated hardware and computer instructions. Those skilled in the art will appreciate that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present disclosure.

[0067] The embodiments of the present disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments have been described separately above, this does not mean that the measures in the respective embodiments cannot be used advantageously in combination. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present disclosure.

[0068] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present invention.

[0069] The embodiments of the present invention have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although the embodiments have been described separately above, this does not mean that the measures in the respective embodiments cannot be used advantageously in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present invention.

Claims

1. A method for growing a doped gallium oxide thin film on a homogeneous substrate, comprising: Epitaxially growing a gallium oxide thin film on a gallium oxide substrate doped with a target doping element; Annealing the gallium oxide substrate and the gallium oxide thin film so that the target doping element diffuses from the gallium oxide substrate into the gallium oxide thin film to obtain a doped gallium oxide thin film.

2. The method according to claim 1, wherein Epitaxially growing a gallium oxide thin film on a gallium oxide substrate doped with a target doping element includes: Epitaxially growing a gallium oxide thin film on the gallium oxide substrate by metalorganic chemical vapor deposition.

3. The method according to claim 2, wherein When epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the growth temperature is 500 - 900 °C, and the chamber pressure is 10 - 200 Torr.

4. The method according to any one of claims 1-3, wherein, When epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the gallium source flow rate is 10 - 300 sccm, and the oxygen source flow rate is 200 - 5000 sccm.

5. The method according to any one of claims 1-3, wherein When epitaxially growing a gallium oxide thin film on the gallium oxide substrate, the tray rotation speed is 0 - 240 rpm.

6. The method according to any one of claims 1 to 3, wherein When annealing the gallium oxide substrate and the gallium oxide thin film, the annealing temperature is 800 - 1100 °C, and the annealing time is 1 - 15 min.

7. The method according to any one of claims 1-3, wherein The thickness of the gallium oxide thin film is 1 - 2000 nm.

8. The method according to any one of claims 1 - 3, further comprising: Successively cleaning the initial gallium oxide substrate with an organic solvent, a piranha solution, and a BOE solution to obtain the gallium oxide substrate.

9. The method according to any one of claims 1-3, wherein The target doping element includes at least one of iron, zinc, copper, magnesium, and aluminum.

10. A photodetector, comprising: A gallium oxide substrate; A doped gallium oxide thin film on the gallium oxide substrate, the doped gallium oxide thin film being prepared according to the method for growing a doped gallium oxide thin film on a homogeneous substrate according to any one of claims 1 - 9; A metal electrode disposed on the surface of the doped gallium oxide thin film.

Images