WO1999028977A1

WO1999028977A1 - SEMICONDUCTOR DEVICE BASED ON HETEROEPITAXIAL FILMS OF NITRIDE COMPOUNDS Gal-xAlxN

Info

Publication number: WO1999028977A1
Application number: PCT/RU1998/000397
Authority: WO
Inventors: Iosif Moiseevich Kotelyansky; Mikhail Iosifovich Kotelyansky; Valery Borisovich Kravchenko
Original assignee: Iosif Moiseevich Kotelyansky; Mikhail Iosifovich Kotelyansky; Valery Borisovich Kravchenko
Priority date: 1997-11-28
Filing date: 1998-11-25
Publication date: 1999-06-10
Also published as: RU2186447C2

Abstract

Semiconductor device based on heteroepitaxial films of nitride compounds Gal-x-AlxN includes monocrystalline sapphire substrate, with the orientation of the working surface, containing directions ∫1100⊃, on which is located heteroepitaxial layered structure, consisting of at least one buffer sublayer and one layer of the semiconductor nitride compound Gal-xAlxN, where: 0 « x « l. Buffer sublayer is made of the material, crystalline structure of which belongs to the cubic syngony with parameter 'a' of the unit cell, lying within the limits from 1.05 n to 1.20 n (Å), where n = 3, 4, 6, 8, and at the same time surface of the sublayer contains direction ∫112⊃, parallel to the direction ∫1100⊃ of the substrate surfaces and of the surfaces of the semiconductor films. Structures of the different semiconductor devices: heterolaser, light emitting diode, photo diode, and field effect transistors are shown.

Description

SEMICONDUCTOR DEVICE BASED ON HETEROEPITAXIAL FILMS OF NITRIDE COMPOUNDS Gaι. Al_xN

BACKGROUND OF THE INVENTION

1 Field of the Invention The Invention belongs to the area of state electronics, namely to the semiconductor devices, designed for the amplification, generation, and switching of the electromagnetic oscillations, capable to work at extended levels of oower and temperature, as well for the reception and generation of optical oscillations in the visible and ultraviolet wavelength ranges 2 Prior Art

Perspective semiconductor devices based on the heteroepitaxial films of the mtπde compounds of type A B^v (e g H Morkos et al, Large-band-gap SιC,III-V nitπde and II- VI ZnSe-based semiconductor device technologies, J. Applied Physics, v 76, N 3, 1 August 1994, p p 1363-1398) [1] The main disadvantage of such devices is the bad working pa- rameters reproducibility, fast degradation of the films due to the high 10⁸ - 10¹⁰ cm^"2 defect concentration These defects are due to high lattice parameters mismatch between the contacting lattice planes of the substrate and of the superconductor film For currently used monocrystalline substrates, used for the heteroepitaxial growth of the (0001 ) GaN films, the mismatch is 16% for the (0001) Al₂O₃ , 9 5% for (111) MgAl₂O₄ , 3 5% for (0001) SiC To reduce the mismatch the buffer layer is used, located between the working surface of the substrate and semiconductor film This buffer layer is made of the mateπals with wurtzite type crystal structure ZnO, GaN, A1N

Known is semiconductor device - light emitting diode, technology of which is de- scribed in (see, T Detchprohm et al, Hydride vapour phase epitaxial growth of high quality GaN films using ZnO buffer layer , AppI.Phys.Lett , v 61, N 22, p p 2688-2690, 1992) [2] This device includes the sapphire substrate with the oπentation of the working surface (0001 ) with the heteroepitaxail structure built on it The heteroepitaxial structure includes a) buffer sublayer of zinc oxide 500 A thick, designed to reduce the mismatch between the (0001) plane of the substrate and heteroepitaxial semiconductor films of nitπde compounds A^m B making the active region of the device, b) //-emitting film of GaN, doped with //-type conduction silicon with thickness of - 3 mkm, c) thin (thickness of 20 A ) active film of the undoped solid solution InoosGaosisN, d) /-emitting film of GaN, doped by /-type magnesium, with thickness of 1 mkm Part of the surface and emitter layers is covered by the ohmic contacts of Ti/Al for //-GaN and

Analysis shows, that this structure does not provide high stability and reproducibility of the device characteπstics

Indeed, hexagonal plane parameters mismatch between the contacting planes (0001) ZnO and (0001) GaN is small 2,3% But unfortunately, mismatch for other planes in contact (0001) ZnO and (0001) Al₂O₃ is 14% Such large mismatch is due to the fact, that contacting planes (0001) Al₂O₃ and (0001) ZnO are twisted relative to each other by 30° around the [0001] direction, so that direction <1100> of Al₂O₃ is parallel to <1120> ZnO Translation peπod along <lϊ θ> Al₂Oι equals 2,747 A , and for <1120> ZnO - 3,25 A, which creates the large mismatch

Due to the large mismatch the (0001) ZnO film can grow on (0001) Al₂O₃ only by "island" (three-dimensional) growth mechanism This growth mechanism, as known, allows to obtain only the "mosaic"' crystal structure film, consisting of separate grains with large amount of grain boundaπes and high structure defect concentration Naturally, the thin semiconductor films, grown on such buffer film, also have the "mosaic" crystal structure with large amount of grain boundaπes and high defect concentration

As (0001) Al₂O₃ and (0001) GaN are twisted relative to each other by 30° around the direction [0001], and cleavage planes of Al O-, and GaN are also twisted around direction [0001] by the same angle of 30° This creates severe technological difficulties in manufactuπng semiconductor laser with mirrors made on the cleavage planes of the semiconductor films SUMMARY OF THE INVENTION The goal of the invention is to develop semiconductor device based on heteroepitaxial films of nitride compounds Gaι._xAl_xN, with better working parameters stability and enhanced lifetime. Semiconductor device includes: monocrystalline sapphire substrate, with the working surface, containing at least one of <1 100> directions, heteroepitaxial layer structure, made on the working surface, and containing, at least, one buffer sublayer and at least one layer of semiconductor nitride compound Gaι-χAl_xN, where: 0< x <1, and at least two electrodes, the said buffer sublayer is located between the working surface of the substrate and the said layer of semiconductor nitride compound Gaι._xAl_xN.

Semiconductor device differs by buffer sublayer made of material, crystalline structure of which belongs to the cubic syngony, and parameter "a" of the unit cubic cell is cho- sen according to the condition:

1,05 n < a (A) < 1,20 n , where // = 3,4,6,8 (1), at the same time this direction <1100>, located in the working surface of the substrate parallel to direction <112>, located in the surface and the aforementioned buffer sublayer. Buffer sublayer made of material with crystalline structure of α-Fe type, with pa- rameter "a" of it's unit cell from the range from 3, 15 A to 3,60 A.

Besides, buffer sublayer can be made of material with crystalline structure of NaCl type and with the unit cell parameter "a" within the range of values from 4,20 A to 4,80 A. Buffer sublayer may be also made of material with crystalline structure of spinel type and with unit cell parameter V within the range from 8,40 A to 9,60 A. In addition to that, buffer sublayer can be made of material, with conductivity large enough to perform the function of the electrode.

The result is achieved based on the following arguments.

As known, the polytypism is characteristic for the gallium and aluminum nitrides. They can crystallize both in hexagonal and cubic modifications. Hexagonal GaN and AIN have wurtzite structure, while their cubic modifications have structure of zinc blende type The two modifications differ only by the sequence of the densely packed planes, and hexagonal unit cell parameters are closely related to the parameters of its cubic polytype unit cell For the same compound

- 1/2 - /2 a _cubιc As the densely packed planes (0001) and (1 1 1) of the polytypes of the same compound have the same symmetry and plane mesh parameters, we can consider only the case when the heteroepitaxial film with the wurtzite structure, for instance, is deposited on the heteroepitaxial buffer sublayer with cubic structure

As we have noticed before, large lattice parameters mismatch between the Al₂O~, (0001) and (0001) of wurtzite, for instance GaN , is due to the 30° twist around the [0001 ] direction We noticed that once the twist is eliminated, the lattice parameters mismatch becomes substantially smaller. Indeed, two translations peπods along < 1100> of Al₂O₃ (2 2 747 = 5 494 A ) coincides with the 0 5% accuracy with the a single translation along < 1100> GaN , equal 5 52A , two translations along < 1 120> Al₂O₃ , equal 2- 4 76 = 9 52 A , is also with the 0 5% accuracy coincides with three translations along < 1120> GaN ( 3 • 3 189 = 9 56 A)

To eliminate the twist, we propose to use a buffer (intermediate) layer (or several layers) of the material with cubic syngony, which at the heteroepitaxy on (0001) Al₂O} has the surface oπentation { 111 }, and direction < 1 12> in this plane is parallel to the -" 1 100> type direction of the Al₂O₃, lying m the (0001) plane of Al₂O-, When the wurtzite type mateπal is further grown on the { 1 11 } surface of the cubic syngony mateπal, the following epitaxial relationships can be obtained

(0001) Al₂O, || {l l l }cub,c ||

(2), <1 Ϊ00> Al₂O, || <1 12>_cubtc || <lTθO>_WέΛate (3) In this case the lattice parameters mismatch between the sapphire substrate surface and semiconductor film is practically absent

Besides, cleavage planes of sapphire and wurtzite, become parallel This makes cleavage planes of the sapphire substrate and of the semiconductor film with wurtzite structure, forming the active region of the semiconductor device -- heterolaser, being paral- lei This is especially important for the laser device fabrication

Therefore, almost perfect lattice parameters match between, for instance, (0001) Al₂O₃ and { 1 1 1 } of the buffer layer on one side, and {1 1 1 } of the buffer sublayer and (0001) of the film with wurtzite structure, for instance, GaN , on the other side, can be achieved Then the cubic lattice unit cell parameter of the buffer sublayer matenal a can be determined from the relationship

where 2 747 A - is a translation period along Al₂O₃ <1100>, and // is an integer, which gives a = 1 125 // A As the unit cell lattice parameters of the Ga, In and Al nitπdes, as well as solid solutions of Ga, In, and Al, used in semiconductor devices, are within the range from 3 11 to 3 25 A Mateπals with a unit cell parameter a less than 2 5 A , or greater, than 13 A are practically absent According to the Invention, it is reasonable to use as buffer sublayer mateπals with cubic syngony with the value of a within the range of 1 05 // to 1 20 n A, where // equals 3, 4, 6, 8 Values of 5, 7, 9 or 10 are not acceptable for n . , these values do not allow to achieve the desired result

Note, that in case when the deposited heteroepitaxial semiconductor film with the polytype structure of zinc blende type, heteroepitaxial buffer layer mateπal is also chosen according to the aforementioned conditions Thus, Invention allows ) to improve structure perfection of the heteroepitaxial nitπde films of compound of type A^fflB^v, forming active region of the semiconductor device, and, hence, to substantially improve the device characteπstics reproducibility and to enhance it's lifetime, b) to eliminate 30° twist of the cleavage planes of sapphire substrate and semicon- ductor films This allows to manufacture laser resonator cavity of the cleavage plane of semiconductor films

Heteroepitaxial buffer sublayer may be made of the mateπal with cubic syngony with crystalline lattice of different types, like for instance α-Fe, NaCl, spinel Buffer sublayer mateπals can be dielectrics, like for instance BaCeOs , MgO, In₂CdO₄ or Na₂MoO₄, or conducting materials, like for instance nitride and carbide of niobium, hafnium, scandium, titanium, their solid solutions, as well as metals: niobium, tantalum.

Buffer sublayer, made of conducting material, can in addition play a role of one of the electrodes of the device. Heteroepitaxial layered structure may contain several buffer sublayers. Using several buffer sublayers significantly broadens the possibilities of more gradual matching of the crystal lattices parameters and thermal coefficients of sapphire substrate and buffer sublayer, on one side, and buffer sublayer and semiconductor nitride film, on the other. But, according to this Invention, when several buffer sublayers are used at least one of them, must made of the material with cubic syngony and with parameter a, satisfying the condition (1). For instance, layered structure may contain buffer sublayers of niobium and it's nitride, or one sublayer of niobium, and another sublayer - of hafnium nitride, or one sublayer of hafnium nitride, and another - of zinc oxide,- material with wurtzite structure. Sapphire substrate can have orientations with it's working surface not only (0001), but also other orientation, that contains direction of <1100> type. These surfaces, are twisted from the basal surface and (0001) around direction <1100> by an angle, the value of which is in the range from 0° to 90°. Example of such surface are planes of type { 1120}, on which, as on (0001) Al₂O₃, may be grown: heteroepitaxial buffer sublayer of the material with cubic syngony with orientation of the surface { 11 1 } and heteroepitaxial semiconductor film of compound Gaι._xAl_xN with wurtzite structure, with orientation

(0001), and/or their zinc blende polytypes with orientation { 1 1 1 }, and one of the directions of <112> type of the surface of sublayer being parallel to <1100>-type direction of the surface of the substrate and wurtzite films, or, correspondingly, <112> of films with zinc blende structure. This can be surfaces of type { 112/}, where / - real number. On these surfaces may be grown heteroepitaxial sublayer of material with cubic syngony, with at least one of the directions of type <1 12> of it's surface being parallel to direction of type <1 100> of the surfaces of substrate and films.

For the semiconductor device fabrication, for instance, such as heterolasers, light emitting diodes, field effect transistors, that have active region consisting of the multilayer semiconductor heterostructure with "quantum dots", "quantum wires", the substrates with non-singular (low-symmetry), in particular "vicinal" working surfaces are used. Such surfaces are not atomically smooth, and can be represented as multi-step surfaces, bound by the low Miller index planes. It is possible, under certain conditions, to obtain "quantum dots", and "quantum wires" on such surfaces, as a result of the self-organisation growth. process.

According to the Invention, it is possible to use sapphire substrates with the working non-singular surface, containing direction < 1 100>, which also belongs to the { 1 12/} family. Buffer sublayer surface, grown on such working surfaces of the sapphire substrate, is also a non-singular plane. It belongs to the family o^f planes containing direction of type < 1 12>. Direction < 1 12>, located in the surface of the sublayer, is parallel to the < 1100> direction of the substrate working surface. And the surface of the semiconductor film, deposited on the non-singular buffer sublayer surface, belongs to the { 112/} family and their < 1100> direction is parallel to < 112>, located in the surface of the sublayer.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures show structures of some of the types of the semiconductor devices, that can be realized according to this invention:

FIG.1 - heterolaser;

FIG.2 - light emitting diode;

FIG.3 - photo diode for the ultraviolet wavelength range; FIG.4 - field effect transistor (FET);

FIG.5 - field effect transistor (FET);

FIG.6 - high electron mobility field effect transistor (HEMT).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example 1. FIG.1 shows structure of the semiconductor device - heterolaser - multi-quantum-well (MQW) structure laser diode (LD) of the blue wavelength range.

Laser contains sapphire substrate 10 with orientation of working surface (0001), containing direction <1 100> On the substrate 10 is located heteroepitaxial layered struc- ture 11, with the buffer sublayer 12. Accordinglo condition (1) buffer sublayer 12 with thickness of 500 A is made of niobium (Nb), material with cubic syngony, with crystalline structure of α-Fe type, with unit cell parameter a = 3,30 A . Sublayer has orientation { 111 }, with the direction <1 12> of the surface { 1 1 1 } of Nb being parallel to the directions <1 100> of the (0001) surface of the substrate 10 and semiconductor films (layers 13-21).

Structure contains layer 13 of GaN (thickness 3 mkm), //-type conduction, doped with Si; layer 14 of the In_o.osGao.₉sN compound, thickness 0,1 mkm, //-type, doped by Si, and also a layer 15 of the compound Al_0.o₈Ga . ₂ N (thickness 0,5 mkm), //-type, doped by Si. Further are located: layer 16 - of GaN ( 0,1 mkm thick), //-type, doped by Si, 17 - laser active region, consisted of the heterostructure of In₀,ιsGao_,8sN - In₀,o₂Gao.₉₈N with three "quantum wells". This heterostructure contains three films of Ino,ιsGao,₈sN, doped by Si, with thickness 35 A each, that make quantum wells. Between these films are located two wider-gap films of In₀,o₂Gao, ₈N, doped by Si, each having thickness of 70 A . Then goes the layer 18 of the compound Alo_. Gao,₈N, doped by Mg, /z-type, with thickness of 200 A , layer 19 of //-GaN, doped by Mg, thickness 0,1 mkm. Then follows the layer 20 of compound Alo,o8Gao,₉₂N, doped by Mg, /-type (thickness 0,5 mkm), and a layer 21 of GaN, doped by Mg, />-type (thickness 0,3 mkm). Position 22 is an electrode of Ni/Au providing an ohmic contact to //-GaN, and pos. 23 - electrode Ti/Al providing the ohmic contact to

Layers 16 and 19 serve as optic waveguides, and layers 15 and 20 are the emitting layers. When constant voltage is applied to the electrodes 22 and 23 in the forward direction, the non-equilibrium charge carriers are injected from emitting films 15 and 20 into the laser active region 17, recombination of which generates blue light radiation.

Heterolaser contains the Fabri-Perot resonator (not shown at figure), formed by the mirrors of the cleavage planes of the heteroepitaxial semiconductor films. These mirrors are covered by the λ/4 dielectric layers of TiO₂ - SiO₂. Layers 13, 14 and 21 are auxiliary. They provide more homogeneous current density, reduce internal mechanical stresses, reduce concentration of the defects and other recombination centers on the boundaries of the heterojunctions of the laser active region. Example 2. Structure of the semiconductor device - heterolaser is analogous to the example I (see. FIG.l).

Sapphire substrate 10 has orientation of the working surface (1120), containing directions of type <1100>, on which the buffer sublayer 12 with thickness 100 A of hafnium nitride (HfN) (structure of the NaCl type, parameter a = 4,50 A) is deposited. Sublayer 12 has orientation { 1 1 1 } HfN, with one of the direction <112> HfN parallel to the direction of type <1 100>, located in the planes (1120) of the substrate 10 and (0001) of the semiconductor films (layers 13 - 21).

Example 3. Structure of the semiconductor device - heterolaser is similar to the ex- ample 1 (see. FIG. l).

Heteroepitaxial layered structure 11 contains two buffer sublayers 12: first 121, located on the surface of the substrate 10, made of Nb (parameters see above) and on top of it is deposited the second sublayer - 122 of niobium nitride NbN (structure of the NaCl type, a = 4,40 A ). Both sublayers have orientation {111 } and <112> Nb and <1 12> NbN are parallel to the <1100> of the substrate 10 and semiconductor films (layers 13-21).

Example 4. Structure of the semiconductor device - heterolaser similar to the example 2 (see. FIG.l).

Heteroepitaxial layered structure 11 contains two buffer sublayers 12: the first sublayer -121, thickness 100 A , made of HfN (see parameters above) is located immedi- ately on the substrate 10 surface, and the second sublayer - 122 of zinc oxide ZnO (thickness 0,5 mkm) is deposited on top of it. Orientation of this sublayer 121 is - { 1 1 1 } HfN, and sublayer 122 (0001) ZnO and with <112> HfN and <U00> ZnO parallel to the <1100> of the substrate 10 and semiconductor films (layers 13-21).

Example 5. Structure of the semiconductor device - heterolaser similar to example / (see. FIG. l).

Substrate 10 has orientation of it's surface { 1 126}, containing direction <1 100>. Buffer sublayer 12 is made of HfN (parameters see above) with thickness 1000 A . Located at the surface of sublayer 12 direction <1 12> HfN is parallel to <1 100> surface of the substrate 10. Example 6. Structure of the semiconductor device - heterolaser similar to example / (see. FIG. l).

Substrate 10 of Al₂O₃ has as it's working surface - non-singular "vicinal" surface { 112 20}, containing direction <1 100>. Surface of the buffer sublayer 12 of Nb (with pa- rameters as above) is also a non-singular plane, containing <1 12> of Nb parallel to the <1100> surface of the substrate 10. Surfaces of the layers 13 - 21 are also characterised non-singular plane belonging to the family { 1 12/}, which <1 100> is parallel to the <1 12> of Nb. Active region of the laser is a heterostructure of the solid solution Ino sGao.ssN - In₀.o₂Ga<)_{. 8}N with "quantum dots". Example 7. Structure of the semiconductor device - heterolaser similar to the example I (see. FIG. l).

Buffer sublayer 12 (thickness 500 A ) of bohr phosphide (BP) (structure of the sphalerite type with a = 4,53 A ). Orientation of the sublayer 12 { 11 1 } BP. At the same time <1 12> of BP is parallel to the <1 100> of the substrate 10. Example 8. Structure of the semiconductor device - heterolaser similar to the example 1 (see. FIG.l).

Buffer sublayer 12 (thickness 800 A ) made of compound In₂CdO₄ (structure of the spinel type, a = 9,11 A ). Orientation of the sublayer 12 - { 111 } In₂CdO₄ . At the same time direction <1 12> of the In₂CdO is parallel to the <1 100> of substrate 10 and semi- conductor layers 13-21.

Example 9. Structure of the semiconductor device -heterolaser similar to the example 1 (see. FIG. l).

Buffer sublayer 12 (thickness 800 A ) made of the solid solution In₀,₇Gao,₃CdO₄ (structure of the spinel type, a = 8,98 A ). Orientation of the sublayer 12 is - { 111 }. At the same time direction <1 12> of In_0.7Gao_,3CdO is parallel to the <1 100> of the substrate 10 and semiconductor layers 13-21.

Example 10. FIG.2 presents structure of the semiconductor device - light emitting diode.

The light emitting diode contains sapphire substrate 30 with orientation (0001), containing directions <1 100>. On the substrate 30 is located heteroepitaxial layered struc- ture 31. It includes two buffer sublayers: 321 and 322, made of, correspondingly, tantalum (Ta) (structure of the α-Fe type; a = 3,30 A ), thickness of 50 A , and it's carbide (TaC) (structure of the NaCl type with a - 4,45 A ), and thickness 800 A . Sublayers 321 and 322 have orientation { 111 } and their directions <1 12> Ta and <1 12> TaC are parallel to the <1100> of the surface (0001) of the substrate 30 and semiconductor films (layers 34-38). On the sublayer 322 is located layer 34 of AIN (thickness 1 mkm). Then follow: layer 35 of the //-GaN film (thickness 2 mkm); layer 36 - of the undoped compound Ino^sGao.ssN (thickness 30 A ), layer 37 - of compound Al₀, Gao_.8N //-type (thickness 0,1 mkm), layer 38 - /-GaN (thickness 0,5 mkm). Active region of the light emitting is formed by the three-layered (double) heterostructure (layers 35,36,37) with one "quantum well". Electrode 39 of Ti/Al is located on the surface of the //-GaN layer 38, and an electrode 40 of Ni/Au - on the part of the surface of the //-GaN layer 35. When voltage is applied to the electrodes 39 and 40 in forward direction in the active region of the light emitting diode green light (with the wavelength 0,5 - 0,55 mkm ) is generated. Example 11. Structure of the semiconductor device - light-emitting diode similar to example 10 (see. FIG.2).

Working surface of the sapphire substrate 30 with the orientation { 1120}, contains directions <1100>. Buffer sublayer 32 is made of a single layer of NbN (parameters as above) of the { 111 } NbN orientation. At the same time direction <112> of NbN is parallel to the <1100> of the surface { 1120} of the substrate 30 and (0001) of the semiconductor layers 34-38.

Example 12. Structure of the semiconductor device - light-emitting diode similar to example 11 (see. FIG.2).

Heteroepitaxial structure 31 contains barrier sublayer 32 of the solid solution Nbo,₉Hfo,ιN (structure of the NaCl type, a =4,41 A ), thickness of 500 A . Orientation of the sublayer - is { 1 1 1 } Nb_0,9Hf_0.ιN, and - <1 12> Nb_0.9Hfo,,N is parallel to the <1 100> of the surfaces { 1 120} of the substrate 30 and (0001) of the layers 34 -38.

Example 13 . FIG.3 shows the structure of the semiconductor device - photo diode for the ultraviolet wavelength range. Photo diode contains sapphire substrate 50 with orientation (0001), containing directions <1 100>. On substrate 50 is located the heteroepitaxial layered structure 51. It includes two barrier sublayers : 52 and 53, made of, correspondingly, Nb (parameters as above) and titanium nitride (TiN) (structure of the NaCl type, a = 4,23 A ). Thickness of the sublayer 52 is 0,1 mkm, and thickness of the sublayer 53 is 0,5 mkm. Orientation of the sublayer 52 is - { 111 } Nb, of the sublayer 52 is - { 111 } TiN and their directions <112> Nb and <1 12> TiN are parallel to the directions <1 100> of the surfaces (0001) of the substrate 50 and of the semiconductor layers 54 and 55. On the sublayer 53 are located: layer 54 of //-GaN (thickness 0,1 mkm) and layer 55 of/λ-GaN (thickness 0,1 mkm). On part of the surface of the layer 55, ohmic contact 56 of Ni/Au is formed. Barrier sublayer 52 of conducting material - niobium does in addition serve as an electrode and is equipped with the contact 57 made of aluminum.

Example 14. . FIG.4 shows structure of the semiconductor device - field effect transistor (FET). FET contains sapphire substrate 60 with orientation (0001), including directions

<1100>. On this surface is located the heteroepitaxial layered structure 61, consisted of buffer sublayer 62 (thickness 500 A ), made of Nb (parameters as above), with orientation { 111 } . At the same time directions <112> of Nb are parallel to the <1 100> of the substrate 60 and of the GaN layer 63, doped by Si to concentration n = 10¹⁷ cm.^"3, with the electron mobility μ = 350 cπTN s^"1. Thickness of the layer 63 is - 0,6 mkm. On parts of the surface of the layer 63 are deposited films of Ti (thickness 25 A ) and Au (thickness 1500 A ), forming two ohmic contacts (electrodes) 64 and 65: source (pos. 64) and drain (pos. 65). Between them is located the third electrode 66 of Ag - gate, that forms a Shottki barrier.

Example 15 . FIG.5 shows structure of the semiconductor device -FET of different design, than in Example 14.

FET includes sapphire substrate 70. with orientation (0001 ). On the substrate 70 is located heteroepitaxial layered structure 71. It contains buffer sublayer 72 (thickness 0,2 mkm) made of Nb (parameters as above), with orientation { 1 1 1 } Nb and buffer sublayer 73 (thickness 0, 1 mkm) of HfN (parameters as above), with orientation {11 1 } HfN. At the same time directions <112> of Nb and <112> of HfN are parallel to <1100> of the surfaces (0001) of the substrate 70, and layer 74 of «-GaN, 0,3 mkm thick. On parts of the surfaces of the layer 74 are located two layers 75, 76, serving as source - layer 75 and drain - layer 76, made of Ti (thickness 25 A ) and of Au (thickness 1500 A ). The gate of this transistor is a Shottki-barrier, formed of materials Nb and HfN of the buffer sublayers 72 and 73. Connecting to the gate is made through the electrode 77, made of aluminum film (thickness 0,2 mkm), and niobium sublayer 72.

Example 16. .FIG.6 shows structure of the semiconductor device - high electron mobility field effect transistor (HEMT). Transistor contains sapphire substrate 80 with orientation (0001), on which is formed heteroepitaxial layered structure 81. It contains the first buffer sublayer 82 (thickness 400 A ) of Nb (parameters as above), with orientation {111} and the second buffer sublayer 83 of HfN (parameters as above) (thickness a 3000 A ) with orientation { 111 } . Directions <112> of Nb and <112> of HfN are parallel to the <1100> of the sub- strate 80 and of the semiconductor layer 84 of //-GaN (thickness 0,3 mkm). On the parts of the surface and this layer 84 are located two ohmic contacts - electrodes 85 and 86 of films of Ti (thickness 25 A ) and of Au (thickness 1500 A ), forming source and drain, correspondingly. On the layer 84 between the electrodes 85 and 86 is located layer 87 of Al₀,ι Gao,₈6N (thickness 0,1 mkm). On part of the surface of layer 87 is located the third electrode 88 of the transistor, forming Shottki barrier. Electrode 88 is formed by metallic film of the TiW alloy. This transistor exploits properties of the two-dimensional electron gas, formed on the boundary of the semiconductor heterostructure //-GaN - Al₀,ι Gao_.86N.

INDUSTRY APPLICABLE

Technical and economical advantages of this Invention are based on the enhanced lifetime of the semiconductor device, enhanced stability and reproducibility of the working parameters in mass production, due to the significant improvement of the crystal lattice perfection of the heteroepitaxial semiconductor films, forming active layers of the device.

The Invention can be realized with cuπent microelectronics technology.

Claims

1 Semiconductor device based on heteroepitaxial films of nit╧Çde compounds Ga╬╣-_XA1_XN, including monocrystal ne sapphire substrate (a), which has working surface (b), containing at least one of directions <1 100>, heteroepitaxial layered structure (c), formed on the working surface (b) and consisted of, at least, one buffer sublayer (d) and of at least one layer of (e) semiconductor nit╧Çde compound Ga╬╣. Al N, where 0 < x <1, and at least two electrodes (/), said buffer sublayer (d) is located between the substrate working surface (b) and said layer (e) of semiconductor nit╧Çde compound Ga╬╣._xAl N, wherein said buffer sublayer (d) is made of mate╧Çal (g), which crystalline structure has cubic syngony, with the parameter "a" of the unit cubic cell chosen according to the condi┬¼

1,05 n < a (A) < 1,20 // , where // = 3, 4, 6, 8 , at the same time direction <1100>, of the working surface (b) of the substrate is parallel to direction <112>, located in the surface of the said buffer sublayer (d).

2 Semiconductor device according to claim 1, wherein said buffer sublayer (d) made of mate╧Çal (g) with crystalline structure of ╬▒-Fe type, with parameter "a" of it's unit cell in the range of values from 3,15 A to 3,60 A

3 Semiconductor device according to claim 1, wherein according said buffer sublayer (d) made of the mate╧Çal (g) with crystalline structure of NaCl type, with parameter "a" of the unit cell in the range of values from 4,20 A to 4,80 A

4. Semiconductor device according to claim 1, wherein said buffer sublayer (d) made of the material (g) with crystalline structure of spinel type, with unit cell parameter "a" in the range of values from 8,40 A to 9,60 A .

5. Semiconductor device according to any one of Claims 1 to 3 , wherein at least one of the said buffer sublayers (d) is made of the material (g) with conductivity enough to be used as an electrode (/).