Method for epitaxial growth of gallium selenide (GaSe) on [111] oriented silicon substrate

Abstract

The present invention relates to a method for epitaxially growing GaSe on a [111] oriented silicon substrate, comprising: a step of selecting a [111] oriented silicon substrate, wherein the substrate is produced by cutting a silicon rod (1) in a bevel direction, wherein the bevel direction is one of three [11-2] crystal directions, and the bevel angle (α) is less than or equal to 0.1°, and the surface of the obtained substrate forms an ortho plane (2), wherein the ortho plane (2) has a plurality of terraces (21) and at least one step (22) between two terraces (21); and a passivation step, wherein the ortho plane (2) is formed on the ortho plane of the silicon substrate. A two-dimensional GaSe layer is formed by depositing an atomic double layer of gallium and selenium on a surface (2) to form a passivated adjacent surface (3) made of silicon-gallium-selenium (Si-Ga-Se), wherein the passivated adjacent surface has a plurality of passivation terraces (31) and at least one passivation step (32) between two passivation terraces; and a step of forming a two-dimensional GaSe layer by epitaxial growth on the passivated surface (3), wherein the forming step includes a step of nucleation from each passivation step (32), and a step of lateral growth of nuclei (41) obtained from the nucleation step on the passivation terrace (31). The present invention also relates to a structure obtained by epitaxial growth.

Description

Technical Field

[0001] The technical field of the present invention is heterogeneous integration of semiconductor materials on silicon substrates, and more specifically relates to epitaxying two-dimensional gallium selenide (2D GaSe) in a single orientation on a

[111] oriented silicon substrate (which can be represented by Si(111)).

[0002] Among the many applications of the invention, mention may be made of microelectronics, photonics, sensors, radio-frequency related technologies, microsystems (MEMS), components of the Internet of Things and more broadly of "more-than-Moore" applications or so-called "spin-off" technologies, i.e. technologies that incorporate several functions on a single silicon chip. Background Art

[0003] Silicon (Si) is the semiconductor that is the basis of micro- and nano-electronics. Its highly mature technology for manufacturing integrated circuits (ICs) has undergone impressive progress in miniaturization and performance improvements.

[0004] However, other semiconductors exhibit complementary (electronic, optical, mechanical, etc.) properties that may be advantageous for implementation on silicon-based chips.

[0005] In this context, a new class of materials has recently emerged: "2D materials". "2D materials" refers to materials that consist of sheets (or stacks of sheets) a few atoms thick. The term "two-dimensional" materials is also used. These materials are electronically saturated, so stacking of several of these sheets occurs via van der Waals bonding. Among 2D materials, some are semiconductors. Their very low thickness gives rise to very unique electronic, optoelectronic and mechanical properties. Materials that are not structured as one or more sheets, but have ionic or covalent bonds throughout their volume may also be called "3D materials", such as conventional semiconductor materials.

[0006] Monolithic heterogeneous integration of 2D materials by epitaxy on silicon substrates is a very promising route to add novel (electronic, optical, photonic, mechanical, biological, etc.) functionalities to the highly mature silicon-based CMOS (complementary metal-oxide-semiconductor) integrated circuits. It can also overcome the troublesome problem of dislocations in the crystal lattice of more conventional (Ge, III-V, GaN, etc.) semiconductors epitaxially grown on silicon.

[0007] Among all 2D materials, gallium selenide (GaSe) is a very interesting material for epitaxy on

[111] oriented silicon substrates, because dangling bonds on the silicon surface can be electronically passivated by atomic layers of gallium (Ga) and selenium (Se) to form a stable and electronically passivated Si-Ga-Se interface, which allows the subsequent growth of two-dimensional GaSe material (called "2D GaSe") by van der Waals epitaxy. The atomic bilayer of gallium and selenium can be formed by using the molecular beam epitaxy (MBE) technique, which consists in projecting one or more molecular beams onto the substrate.

[0008] The expression "electronically passivate" or "electronic passivation" refers to the removal of dangling bonds (or reactive Si-H bonds in a hydrogen-containing environment). The expression "electronically saturated surface" may also be used.

[0009] The gallium atomic layer thus bonded to the selenium atomic layer may be referred to as an "atomic bilayer" and may be considered a half-sheet of a "2D GaSe" material. Specifically, 2D GaSe refers to two-dimensional gallium selenide (as a sheet) consisting of four atomic layers in the order Se-Ga-Ga-Se.

[0010] However, the formation of a Si-Ga-Se interface can produce a surface with two types of domains that are mirror images of each other, resulting in Figure 1A (Orientation 1) and 1B (Orientation 2) shown in the antiphase defect.

[0011] Subsequent epitaxial growth of 2D GaSe material on this Si-Ga-Se interface, more specifically on this surface with mirror image domains 5, can also lead to the formation of GaSe grains with two orientations at 180° relative to each other, as Figure 2 When these GaSe grains coalesce, crystal defects (grain boundaries) will be formed, and these crystal defects may damage the optical, electronic, thermal and mechanical properties of 2D GaSe materials.

[0012] In general, the techniques used in the prior art for growing 2D GaSe are sensitive to the different orientations of the passivated Si(111) surface. Therefore, the 2D GaSe layer thus obtained always contains two types of domains (mirror images of each other) separated by grain boundaries, resulting in crystal defects.

[0013] The present invention aims to provide a method for epitaxially growing gallium selenide on a

[111] oriented silicon substrate without the above-mentioned disadvantages of the prior art.

[0014] More specifically, the present invention aims to provide a method for epitaxially growing 2D GaSe on a

[111] oriented silicon substrate, which method can reduce defects generated at the interface between the silicon substrate and the epitaxial layer of the 2D GaSe, in particular reduce the formation of anti-phase boundaries, and the method is industrially applicable, that is, directly implemented on a large scale (200mm and 300mm substrates) and has a high manufacturing yield. Summary of the invention

[0015] A method that can overcome these disadvantages is a method for epitaxially growing GaSe on a

[111] oriented silicon substrate, characterized in that the method comprises:

[0016] - a step of selecting a

[111] oriented silicon substrate, the substrate being produced by cutting a silicon rod in a miscut direction, the miscut direction being one of the three [11-2] crystallographic directions, the miscut angle being less than or equal to 0.1°, the surface of the substrate being obtained forming a vicinal surface having a plurality of terraces and at least one step between two terraces;

[0017] - a passivation step consisting of depositing an atomic bilayer of gallium and selenium on said vicinal plane of said silicon substrate to form a passivated vicinal plane made of silicon-gallium-selenium, said passivated vicinal plane having a plurality of passivation terraces and at least one passivation step between two passivation terraces;

[0018] - a step of forming a two-dimensional GaSe layer by epitaxy on the passivated adjacent planes, said forming step comprising a step of nucleation from each passivation step and a step of lateral growth of the nuclei obtained from the nucleation step on said passivation terraces.

[0019] The expression “the chamfer angle is less than or equal to 0.1°” is understood to mean that the absolute value of the chamfer angle is less than or equal to 0.1°, in other words, the chamfer angle is between -0.1° and +0.1°, inclusive.

[0020] The expression "lateral growth" is understood to mean that each nucleus grows from the step in a direction opposite to said step and along the main plane of the terrace.

[0021] The method combines the precise choice of Si(111) substrates that have been cut to exact specifications (allowing access to ortho planes) with conditions for epitaxial growth of GaSe that allow preferential nucleation of 2D GaSe by aligning the steps on the ortho planes.

[0022] Ortho planes are surfaces on which atoms are no longer distributed in a plane, but are organized in a set of regularly spaced steps whose height is a multiple of the distance between two consecutive planes of atoms in the material's lattice. The surface appears as a series of terraces and steps between them. Depending on the conditions under which the material is cut, the steps are ideally straight and parallel.

[0023] Thus, the method comprises selecting a

[111] oriented silicon substrate from a cylindrical rod of

[111] oriented silicon. The

[111] oriented plane of silicon is a dense plane. The ortho plane of the substrate is obtained from the cylindrical rod of

[111] oriented silicon by cutting the cylindrical rod of

[111] oriented silicon along a crystal plane slightly misoriented relative to the dense

[111] plane (i.e., its bevel angle is less than or equal to 0.1°).

[0024] The step of selecting may comprise a step of controlling these specifications of cutting the selected substrate.The step of controlling the substrate may comprise a step of measuring the substrate using X-ray diffraction, which makes it possible to obtain the misorientation characteristic of the substrate.

[0025] The cutting must be done to orient the arrangement direction of the steps so that the growth of 2D GaSe can be determined by these steps in the step of forming the 2D GaSe layer. This allows the preferential nucleation of 2D GaSe from the steps rather than within the terraces. Specifically, the orientation of the 2D GaSe layer will be determined by the arrangement direction of the steps.

[0026] In the step of forming a 2D GaSe layer by epitaxy, for example, during or after the nucleation step, a step of controlling the arrangement of GaSe nuclei against the steps can be added. The step of controlling the arrangement can include a step of measuring using a high-resolution scanning transmission electron microscope (STEM) that is capable of checking the presence of covalent bonds of GaSe atoms at the steps.

[0027] Finally, the combination of the selection step and the step of forming the 2D GaSe layer makes it possible to obtain a 2D GaSe layer with a single orientation, thereby overcoming the problem of grain boundaries. This 2D GaSe layer with a very low defect rate can then be used as an active layer of a silicon-on-silicon device with novel (electronic, optoelectronic, mechanical, etc.) functions.

[0028] According to one embodiment, the method further comprises a step of treating the vicinal surfaces to flatten the terraces of said vicinal surfaces until a substantially zero roughness is obtained on the terraces, said treating step being performed after the substrate selection step and before the passivation step.

[0029] The treatment step may consist in thermally treating the silicon substrate at a high temperature, preferably above 800° C. The pressure during the thermal treatment is preferably below 600 Torr.

[0030] According to one embodiment, the passivation step consists of metal organic chemical vapor deposition (MOCVD) with metal organic precursors. In particular, the metal organic precursors can be trimethyl gallium (TMGa) and diisopropyl selenide (DIPSe). The partial pressure of TMGa is preferably between 1 mTorr and 200 mTorr. The passivation step is preferably carried out at a temperature between 400° C. and 650° C. The passivation step is preferably carried out for a duration between 2 seconds and 30 seconds.

[0031] According to one embodiment, the nucleation step consists of metal organic chemical vapor deposition with a metal organic precursor. The partial pressure of the gallium precursor is preferably lower than or equal to 50 mTorr. The nucleation step is preferably carried out at a temperature between 400° C. and 650° C. The nucleation step is preferably carried out for a duration between 2 seconds and 30 seconds.

[0032] According to one embodiment, the lateral growth step consists of metal organic chemical vapor deposition with metal organic precursors. The partial pressure of the gallium precursor is preferably between 0.5 mTorr and 5 mTorr. The lateral growth step is preferably carried out at a temperature between 570°C and 650°C.

[0033] According to one embodiment, the method further comprises a step of removing oxide from said vicinal planes, said deoxidation step being performed after the substrate selection step and before the passivation step.

[0034] According to one embodiment, the method further comprises an additional step of epitaxially growing at least one 2D material other than 2D GaSe or at least one 3D semiconductor material, said additional epitaxially growing step being formed on the 2D GaSe layer.

[0035] Therefore, the 2D GaSe layer obtained by the method according to the present invention can be used as a high-quality buffer layer for the subsequent growth of other materials and has a low defect rate. At least one 2D material or at least one 3D material other than 2D GaSe can be selected from III-VI materials such as InSe, GaS, GaTe or a combination of III-VI materials, III-V materials such as GaN, InGaN, GaAs, GaSb or a combination of III-V materials, II-VI materials such as CdHgTe or a combination of II-VI materials, or IV-IV materials such as SiGe or Ge-Ge or a combination of IV-IV materials.

[0036] This method makes it possible to perform epitaxy by proceeding from each step of the vicinal plane of silicon Si(111) so as to obtain a 2D GaSe layer of single orientation without grain boundaries.

[0037] This approach can ultimately achieve a single orientation of 2D GaSe without anti-phase defects and is performed using an industrially applicable method that can be performed on a large scale with high yield, in particular using MOCVD on substrates that are compatible with standard micro / nano fabrication building blocks of the silicon technology platform.

[0038] Another subject of the invention is a structure obtained by epitaxy, comprising:

[0039] - a

[111] -oriented silicon substrate, the surface of which is a passivated vicinal surface, the passivated vicinal surface having a passivated terrace and at least one passivated step between two passivated terraces;

[0040] - A 2D GaSe layer formed on the passivation mesa and having a single orientation without antiphase boundaries.

[0041] The off-cut angle of the adjacent plane of the

[111] oriented silicon substrate is less than or equal to 0.1°.

[0042] Preferably, the [11-2] direction of the silicon surface is aligned with the [11-20] direction of GaSe. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features and advantages of the present invention will become apparent from the following non-limiting illustrative description given with reference to the accompanying drawings, in which:

[0044] [ Figure 1A ]and[ Figure 1B ] shows a Si-Ga-Se surface with two opposite orientations.

[0045] [ Figure 2 ] shows the formation of 2D GaSe grains with two orientations at 180° relative to each other.

[0046] [ Figure 3A ]、[ Figure 3B ]、[ Figure 3C ]、[ Figure 3D ]、[ Figure 3E ]、[ Figure 3F ]and[ Figure 3G ] shows an exemplary method for epitaxially growing 2D GaSe on a Si(111) substrate according to the present invention. DETAILED DESCRIPTION

[0047] Already described Figure 1A , Figure 1B and Figure 2 , which will not be repeated here.

[0048] Figures 3A to 3GAn exemplary method of epitaxially growing 2D GaSe on a Si(111) substrate according to the present invention is shown.

[0049] The first step of the method is a selection step, which consists in selecting a

[111] oriented silicon substrate obtained from a silicon crystal rod 1, which is sliced ​​into slices according to a cutting specification suitable for obtaining a

[111] oriented silicon adjacent plane 2 (also referred to as an adjacent Si (111) substrate).

[0050] More precisely, the adjacent Si(111) substrate is produced by cutting the silicon rod along the substrate's bevel directions 11, 12, 13, which are exactly along one of the three equal [11-2] crystal directions. In other words, the silicon crystal is cut along one of the following azimuthal angles: 90°, 30° or -30° relative to the [1-10] direction of the notch used for the orientation of the substrate's crystal lattice.

[0051] Figure 3A Shown are three identical [11-2] crystal directions in a top view of a Si(111) silicon crystal rod 1. The rod may be cut, for example, along a direction 11 corresponding to one of the three identical [11-2] crystal directions.

[0052] Figure 3B The misorientation parameter is shown. The misorientation of a crystal is defined by the bevel angle α, which defines the angle between the normal to the ortho plane 2 and the

[111] direction.

[0053] As mentioned in the disclosure of the present invention, in the ortho plane, atoms are not distributed in a plane, but are organized with a set of terraces and at least one step spaced apart by two terraces. The height of the step is a multiple of the distance between two continuous atomic planes. Therefore, the ortho plane 2 shown is represented by a series of terraces 21 and at least one step 22 between the two terraces. The width L of the terrace corresponds to the size along the [11-2] crystal direction selected for cutting. The height h of the step corresponds to the size along the

[111] crystal direction.

[0054] The width L of the mesa 21 can be determined from the chamfer angle α using the following formula:

[0055] [Math1]

[0056] L = h / (tan α)

[0057] Where h is the height of the step.

[0058] In the case of Si(111), the height of the step is about 0.3 nm.

[0059] The misorientation of the crystal is also defined by the off-angle direction as one of the three [11-2] crystal directions as described above.

[0060] In addition, in order to have wide terraces and thus a low step density, the chamfer angle is selected to be less than or equal to 0.1°. A low step density is advantageous for a low density of nuclei, thus limiting potential defects (particularly dislocations) that may occur during the GaSe nucleation step. The expression "low step density" is generally understood to mean steps with a terrace width of at least 200 nanometers.

[0061] Thus, a Si(111) substrate with slightly misoriented vicinal planes is obtained, ie, the off-cut angle is less than or equal to 0.1°.

[0062] After the selection step and before the treatment step described below, the method may include, for example, wet treatment with hydrogen fluoride (HF) or in Siconi TM The step of using plasma to remove oxide from the (111) silicon surface in a type deoxidation chamber.

[0063] The second step of the method is a processing step, which consists of processing the obtained ortho-plane 2 to flatten the

[111] oriented terrace 21. This makes the steps appear to be precisely oriented along the [11-2] direction, such as Figure 3C This treatment step, carried out at high temperature, consists in the surface diffusion of silicon atoms until they reach their equilibrium position, revealing the lowest energy

[111] oriented silicon planes. As a result, the residual roughness of the

[111] oriented terraces of the silicon substrate after cutting and chemical mechanical polishing (CMP) reaches values ​​close to zero.

[0064] This processing step is usually carried out by introducing the substrate into an epitaxy chamber. A gas, such as hydrogen, is introduced. Alternatively, it can be helium, argon or any other inert gas in column VIII of the periodic table.

[0065] The treatment step is typically performed at between 800°C and 1100°C.

[0066] The pressure in the chamber may be within a relatively large range, for example between 1 mTorr and 750 Torr, or even between 1 mTorr and 600 Torr. Preferably, the pressure in the chamber is low, that is, typically below 20 Torr, preferably below 10 Torr. The low pressure prevents the silicon from starting to be eroded by the gas, in particular hydrogen, and thus prevents the formation of pits on the silicon surface.

[0067] Processing time is usually between 5 and 30 minutes.

[0068] According to a specific exemplary embodiment, the conditions of the treating step are:

[0069] -Pressure in the chamber: 5-10 Torr;

[0070] - Temperature: 900°C;

[0071] - Duration of treatment: 10 minutes.

[0072] The third step of the method is a step of passivating the adjacent Si(111) surface, and this is formed by depositing a bilayer of atoms of gallium and selenium on the Si(111) surface, i.e., a layer of gallium (Ga) atoms and a layer of selenium (Se) atoms. This makes it possible to obtain the formation of a passivated adjacent plane 3 of Si-Ga-Se, such as Figure 3D Specifically, the highly reactive Si-H hydrogen bonds at the Si(111) surface are replaced by Si-Ga-Se bonds that are stable to high temperatures (up to about 650-750°C) and are electronically passivated, i.e., the valence shells of the atoms at the surface are full (valence electrons are paired). This very low energy passivated surface then allows the epitaxial growth of 2D materials without covalent bonding to the mesas 21 of the silicon substrate

[111] , as further described below.

[0073] A GaSe passivation bilayer formed by one atomic layer of Ga bonded to one atomic layer of Se also corresponds to a half-sheet of 2D GaSe material consisting of four atomic layers in the order Se-Ga-Ga-Se. 2D GaSe refers to gallium selenide structured as one or more sheets.

[0074] According to the invention, the expression "electronically passivated" surface or "electronic passivation" of a surface is understood to mean a surface which is chemically inert and stable even at high temperatures (up to about 650-750° C.), in which the atoms have a full valence layer. The expression "electronically saturated surface" may also be used.

[0075] To perform the passivation step, the Si(111) substrate remains in the epitaxial chamber and a GaSe semi-thin sheet is deposited using a deposition technique called Metal Organic Chemical Vapor Deposition (MOCVD). The MOCVD technique is performed by delivering metal organic precursors into the epitaxial chamber via a carrier gas.

[0076] To obtain GaSe semi-thin sheets using MOCVD, metal organic precursors that are gaseous at the temperatures used in the process, typically trimethylgallium (TMGa) and diisopropylselenide (DIPSe), are simultaneously introduced into the chamber. Alternatively, any other gallium precursor and / or any other selenium precursor may be used.

[0077] The carrier gas is usually hydrogen. Alternatively, it can be nitrogen or an inert gas from column VIII of the periodic table.

[0078] The passivation step is preferably carried out between 400°C and 650°C.

[0079] The total pressure in the chamber depends on the equipment, but values ​​are typically between 5 Torr and 200 Torr.

[0080] The partial pressure of the gallium precursor is preferably between 1 mTorr and 200 mTorr.

[0081] The III / VI (Group III precursor / Group VI precursor) molar flux ratio is typically between 1 and 10.

[0082] The duration of the passivation step is typically between 2 and 30 seconds.

[0083] According to a specific exemplary embodiment, the conditions of the passivation step are:

[0084] -Total pressure in the chamber: 10-20 Torr;

[0085] -TMGa partial pressure: about 10 mTorr;

[0086] - Se / Ga (VI / III) molar flux ratio: about 3-4;

[0087] - Temperature: 530-550°C;

[0088] - Deactivation duration t: between 2 and 5 seconds.

[0089] The GaSe half-thin sheet used to obtain the passivated surface has a surface area of ​​approximately Thickness.

[0090] The MOCVD technique is advantageous because it allows good reproducibility, good uniformity on a substrate scale, and high crystal growth rates. It is therefore compatible with industrial applications.

[0091] Alternatively, other chemical vapor deposition (CVD) techniques may be used, such as plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or hydride vapor phase epitaxy (HVPE).

[0092] Alternatively, the technique of molecular beam epitaxy (MBE) can be used, which consists in projecting one or more molecular beams onto the substrate to carry out epitaxial growth.

[0093] The fourth step of the method is a step of forming a 2D GaSe layer on the passivated adjacent surface. It consists in growing GaSe two-dimensionally on the passivated surface 3 (in order to effectively obtain a 2D GaSe layer). Therefore, it consists of epitaxy, which includes a nucleation step and a step of lateral growth from the nucleus until a continuous buffer layer is formed. The steps of nucleation and lateral growth are described as follows.

[0094] The nucleation step is achieved by Figure 3E ), more precisely by depositing GaSe grains (or cores) 41 on the surface of the mesa and against the steps of the mesa. The GaSe cores 41 have an initial width typically between 1 and 20 nanometers.

[0095] For nucleation, the substrate is kept in a growth chamber and MOCVD technique is used. The precursors that can be used are the same as for the passivation step. The pressure employed is lower than that of the passivation step.

[0096] The carrier gas is usually hydrogen. Alternatively, it can be nitrogen, argon or any other inert gas in column VIII of the periodic table.

[0097] To promote nucleation against the steps rather than within the terraces, the partial pressure of the precursor (e.g., TMGa) is advantageously low or moderate (less than or equal to 50 mTorr) to minimize encounters between Ga and Se atoms with each other within the terraces rather than against the steps, and the temperature is high enough (at least 400°C, but preferably at least 500°C) to allow surface diffusion of atoms to the steps.

[0098] Therefore, the nucleation step is typically performed between 400°C and 650°C.

[0099] The total pressure is adjusted depending on the geometry of the chamber, but values ​​are typically between 5 Torr and 80 Torr.

[0100] The partial pressure of the gallium precursor is typically between 1 mTorr and 50 mTorr.

[0101] The VI / III molar flux ratio depends on the type of precursor; values ​​are typically between 3 and 4 Torr.

[0102] The duration of the nucleation step is typically between 2 and 30 seconds.

[0103] These conditions are therefore chosen to promote diffusion and attachment of Ga and Se atoms from the steps, which is the configuration of minimum energy. Therefore, the growth of 2D GaSe can be preferentially initiated from the steps, rather than starting growth on the terraces (such as in the middle of the terraces) in an uncontrolled manner.

[0104] During this nucleation step, the GaSe nuclei will be arranged from the terraces in a single orientation and precisely in the [11-2] direction of the silicon surface aligned with the [11-20] direction of the GaSe ([11-2] Si / / [11-20] GaSe )arrangement.

[0105] According to a specific exemplary embodiment, the conditions of the nucleation step are as follows:

[0106] -Total pressure in the chamber: 5-20 Torr;

[0107] -TMGa partial pressure: about 2-3 mTorr,

[0108] - Se / Ga (VI / III) molar flux ratio: about 3-4;

[0109] - Temperature: 530℃-550℃;

[0110] - Nucleation duration: 2-15 seconds.

[0111] The step of lateral growth of GaSe grains consists in causing the GaSe grains 41 deposited in the nucleation step to grow laterally, that is, to grow laterally relative to the plane of the terrace on which the grains have been deposited, and to grow in this way by several micrometers, such as Figure 3F and 3G As shown, until the grains coalesce into a single oriented continuous layer 4 without grain boundaries.

[0112] The lateral growth step of the GaSe grains occurs at a lower partial pressure and a higher temperature than the nucleation step.

[0113] The substrate is held in a growth chamber.

[0114] The lateral growth step is typically performed between 570°C and 650°C.

[0115] The total pressure depends on the equipment used, but values ​​are typically between 5 Torr and 80 Torr.

[0116] The partial pressure of the precursor is typically between 0.5 mTorr and 5 mTorr.

[0117] The VI / III molar flux ratio is typically between 3 and 4.

[0118] The duration of the lateral growth step is typically between 5 minutes and 120 minutes.

[0119] According to a specific exemplary embodiment, the conditions of the growing step are as follows:

[0120] -Total pressure in the chamber: 5-20 Torr;

[0121] -TMGa partial pressure: about 1 mTorr,

[0122] - Se / Ga (VI / III) molar flux ratio: about 3-4;

[0123] -Temperature: 600℃-640℃;

[0124] - Growth duration: 1000 seconds - 2000 seconds.

[0125] The method according to the invention makes it possible to perform epitaxy by advancing GeSe nuclei from steps and thus obtain a 2D GaSe layer of single orientation and without grain boundaries.

[0126] The structures formed by this method include:

[0127] - a

[111] oriented silicon substrate, the surface of which is a passivated vicinal surface 3, wherein the passivated vicinal surface 3 has a passivation terrace 31 and at least one passivation step 32 between two passivation terraces;

[0128] - A 2D GaSe layer 4 formed on the passivated mesas and having a single orientation without antiphase boundaries.

[0129] The bevel angle α of the adjacent plane 3 of the

[111] -oriented silicon substrate is less than or equal to 0.1°.

[0130] Preferably, the orientation of GaSe relative to the structure of the silicon surface is ([11-2] Si / / [11-20] GaSe ).

[0131] The structures thus obtained are therefore of high crystalline quality and allow their integration in applications such as electronics, optics, energy, etc.

[0132] The process used can be large-scale and has high yields, thus making it compatible with use in industry.

[0133] The formed 2D GaSe layer can be used as a buffer layer, on which other 2D materials can be grown by van der Waals epitaxy using, for example, MOCVD techniques. These other 2D materials can, for example, be selected from other III-VI semiconductors, such as InSe, GaS, GaTe, etc., or a combination of several III-VI materials, in order to obtain an energy band arrangement corresponding to the type of component to be manufactured (photodetectors, LEDs, MOSFETs, TFETs and generally all "beyond Moore's Law" components).

[0134] Therefore, these additional layers can be grown in a single orientation, in epitaxial relationship with the 2D GaSe layer.

[0135] Instead of a 2D material, it can be a 3D material, which can be: a III-V material such as GaN, InGaN, GaAs, GaSb or a combination of several III-V materials, a II-VI material such as CdHgTe or a combination of several II-VI materials, or a IV-IV material such as SiGe or Ge-Ge or a combination of several IV-IV materials.

[0136] Unless otherwise stated or apparent, the different embodiments may be combined.The invention is not limited to the embodiments described above but extends to any embodiment falling within the scope of the claims.

[0137] Among the many applications of the invention, mention may be made of microelectronics, photonics, sensors, radio-frequency related technologies, micro-electromechanical systems (MEMS), components of the Internet of Things and more generally of "more-than-Moore" technologies or so-called "spin-off" technologies, i.e. technologies incorporating several functions on a single silicon chip.

Claims

1. A method for epitaxially growing GaSe on a [111] oriented silicon substrate, characterized in that: The method comprises: - a step of selecting a [111] oriented silicon substrate, the substrate being produced by cutting a silicon rod (1) in a bevel direction, the bevel direction being one of the three [11-2] crystal directions, the bevel angle (α) being less than or equal to 0.1°, the surface of the obtained substrate forming an ortho plane (2), the ortho plane (2) having a plurality of terraces (21) and at least one step (22) between two terraces (21); - a passivation step consisting of depositing an atomic double layer of gallium and selenium on said vicinal surface (2) of said silicon substrate to form a passivated vicinal surface (3) made of silicon-gallium-selenium (Si-Ga-Se), said passivated vicinal surface having a plurality of passivation terraces (31) and at least one passivation step (32) between two passivation terraces; - A step of forming a two-dimensional GaSe layer by epitaxial growth on the passivated adjacent plane (3), the forming step comprising a step of nucleation from each passivation step (32), and a step of lateral growth of the nuclei (41) obtained from the nucleation step on the passivation terrace (31).

2. The method according to claim 1 further comprises a step of treating the vicinal surface to flatten the terrace (21) of the vicinal surface until a substantially zero roughness is obtained on the terrace, the treating step being performed after the substrate selection step and before the passivation step.

3. The method of claim 2, wherein the processing step consists of thermally treating the silicon substrate at a high temperature.

4. The method of claim 2, wherein the treating step consists of thermally treating the silicon substrate at a temperature higher than 800°C.

5. The method according to any one of claims 1 to 4, wherein the passivation step consists of metal organic chemical vapor deposition (MOCVD) using metal organic precursors.

6. The method of claim 5, wherein the metal organic precursor is trimethyl gallium (TMGa) and diisopropyl selenide (DIPSe). 7 . The method of claim 6 , wherein the partial pressure of trimethylgallium (TMGa) is between 1 mTorr and 200 mTorr.

8. The method of claim 5, wherein the passivation step is performed at a temperature between 400°C and 650°C and for a duration between 2 seconds and 30 seconds.

9. The method according to any one of claims 1 to 4, wherein the nucleation step consists of metal organic chemical vapor deposition using a metal organic precursor, the partial pressure of the gallium precursor being lower than or equal to 50 mTorr.

10. The method of claim 9, wherein the nucleation step is performed at a temperature between 400°C and 650°C.

11. The method of claim 9, wherein the nucleation step is performed for a duration between 2 seconds and 30 seconds.

12. The method according to any one of claims 1 to 4, wherein the lateral growth step consists of metal organic chemical vapor deposition using a metal organic precursor, the partial pressure of the gallium precursor being between 0.5 mTorr and 5 mTorr.

13. The method of claim 12, wherein the lateral growth step is performed at a temperature between 570°C and 650°C.

14. The method according to any one of claims 1 to 4, further comprising a step of removing oxide from the vicinal plane (2), the step of removing oxide being performed after the substrate selection step and before the passivation step.

15. The method according to any one of claims 1-4, further comprising an additional step of epitaxially growing at least one 2D material other than 2D GaSe or at least one 3D semiconductor material, the additional epitaxially growing step being formed on the 2D GaSe layer.

16. The method of claim 15, wherein the at least one 2D material other than 2D GaSe or the at least one 3D semiconductor material is selected from a III-VI material, a III-V material, a II-VI material, or a IV-IV material.

17. The method of claim 16, wherein the III-VI material is InSe, GaS, GaTe, or a combination of III-VI materials.

18. The method of claim 16, wherein the III-V material is GaN, InGaN, GaAs, GaSb, or a combination of III-V materials.

19. The method of claim 16, wherein the II-VI material is CdHgTe or a combination of II-VI materials.

20. The method of claim 16, wherein the IV-IV material is SiGe or Ge-Ge or a combination of IV-IV materials.

21. A structure obtained by the method for epitaxially growing GaSe on a [111] oriented silicon substrate according to any one of claims 1 to 20, comprising: - a [111]-oriented silicon substrate, the surface of which is a passivated vicinal surface (3), the passivated vicinal surface (3) having a passivation terrace (31) and at least one passivation step (32) between two passivation terraces, and the bevel angle (α) of the passivated vicinal surface (3) is less than or equal to 0.1°; - a 2D GaSe layer (4) formed on the passivation mesa and having a single orientation without antiphase boundaries.

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