Hemt epitaxial wafer and preparation method thereof, hemt device

Abstract

The disclosure provides a HEMT epitaxial wafer and a preparation method thereof and a HEMT device, and belongs to the technical field of semiconductor devices. The HEMT epitaxial wafer comprises a Si substrate, a composite transition layer, an AlGaN buffer layer, an AlGaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked on the Si substrate, the composite transition layer comprises a low-temperature BP nucleation layer, a high-temperature BP nucleation layer and a pre-deposited Al layer which are sequentially stacked on the Si substrate, and the growth temperature of the low-temperature BP nucleation layer is lower than that of the high-temperature BP nucleation layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of semiconductor devices, and particularly relates to a HEMT epitaxial wafer, a preparation method thereof and a HEMT device. BACKGROUND

[0002] A high electron mobility transistor (HEMT) is a kind of heterojunction field effect transistor. A HEMT epitaxial wafer is the basis for preparing a HEMT device, and the HEMT epitaxial wafer comprises a silicon (Si) substrate and an aluminum gallium nitride (AlGaN) buffer layer, an AlGaN high resistance layer, a gallium nitride (GaN) channel layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked on the Si substrate.

[0003] The performance of the HEMT device is largely dependent on the crystal quality of the epitaxial layer. In order to reduce the lattice mismatch between the Si substrate and the GaN in the epitaxial layer, reduce the dislocation density and improve the crystal quality of the epitaxial layer, a low-temperature aluminum nitride (AlN) nucleation layer and a high-temperature AlN nucleation layer are usually arranged between the Si substrate and the AlGaN buffer layer.

[0004] However, since the lattice constants of GaN and AlN are 0.3189 nm and 0.3112 nm respectively, and the band gap widths of GaN and AlN are 3.4 eV and 6.2 eV respectively, the lattice constant (0.5431 nm) and the band gap width (1.12 eV) of Si are quite different from those of GaN and AlN, and the crystal quality of the epitaxial layer grown on the low-temperature AlN nucleation layer and the high-temperature AlN nucleation layer is not high. SUMMARY

[0005] The present disclosure provides a HEMT epitaxial wafer, a preparation method thereof and a HEMT device, which can improve the crystal quality of the HEMT epitaxial wafer. The technical solution is as follows:

[0006] The present disclosure provides a HEMT epitaxial wafer, which comprises:

[0007] a Si substrate, a composite transition layer, an AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked on the Si substrate,

[0008] The composite transition layer comprises a low-temperature boron phosphide (BP) nucleation layer, a high-temperature BP nucleation layer and a pre-deposited Al layer which are sequentially stacked on the Si substrate, and the growth temperature of the low-temperature BP nucleation layer is lower than that of the high-temperature BP nucleation layer.

[0009] Optionally, the growth temperature of the low-temperature BP nucleation layer ranges from 600 to 800 DEG C, and the growth temperature of the high-temperature BP nucleation layer ranges from 900 to 1100 DEG C.

[0010] The thickness of the low-temperature BP nucleation layer ranges from 10 to 40 nm, and the growth temperature of the high-temperature BP nucleation layer ranges from 150 to 250 nm.

[0011] The growth pressure of the low-temperature BP nucleation layer ranges from 200 to 300 mbar, and the growth pressure of the high-temperature BP nucleation layer ranges from 50 to 100 mbar.

[0012] Optionally, the growth temperature of the pre-deposited Al layer ranges from 900 to 1100 DEG C, the growth pressure of the pre-deposited Al layer ranges from 40 to 70 mbar, and the thickness of the pre-deposited Al layer ranges from 1 to 5 nm.

[0013] Optionally, the HEMT epitaxial wafer further comprises an AlN interlayer between the GaN channel layer and the AlGaN barrier layer.

[0014] The disclosure provides a preparation method of a HEMT epitaxial wafer, which comprises:

[0015] providing a Si substrate;

[0016] growing a composite transition layer on the Si substrate, the composite transition layer comprising a low-temperature BP nucleation layer, a high-temperature BP nucleation layer and a pre-deposited Al layer stacked in sequence on the Si substrate;

[0017] growing an AlGaN buffer layer, an AlGaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer in sequence on the composite transition layer.

[0018] Optionally, the growing of the composite transition layer on the Si substrate comprises preparing the low-temperature BP nucleation layer in the following manner:

[0019] growing the low-temperature BP nucleation layer with a thickness ranging from 10 to 40 nm at a growth temperature ranging from 600 to 800 DEG C and a growth pressure ranging from 200 to 300 mbar.

[0020] Optionally, the growing of the composite transition layer on the Si substrate comprises preparing the high-temperature BP nucleation layer in the following manner:

[0021] The high-temperature BP nucleation layer has a thickness in a range of 150nm to 250nm, and is grown under conditions that the growth temperature is in a range of 900℃ to 1100℃ and the growth pressure is in a range of 50mbar to 100mbar.

[0022] Optionally, the growing the composite transition layer on the Si substrate comprises: preparing the pre-deposited Al layer in the following manner:

[0023] The pre-deposited Al layer has a thickness in a range of 1nm to 5nm, and is grown under conditions that the growth temperature is in a range of 900℃ to 1100℃ and the growth pressure is in a range of 40mbar to 70mbar.

[0024] Optionally, the preparation method further comprises:

[0025] An AlN insertion layer is grown between the GaN channel layer and the AlGaN barrier layer.

[0026] The HEMT device provided by the embodiments of the present disclosure comprises the HEMT epitaxial wafer as described in any of the preceding embodiments.

[0027] The technical solutions provided by the embodiments of the present disclosure have the following beneficial effects:

[0028] By setting the nucleation layer as a double-layer structure composed of a low-temperature BP nucleation layer and a high-temperature BP nucleation layer, compared with a conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch with the GaN epitaxial layer, and can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth. When AlN is used as the nucleation layer, the lattice constant of AlN is smaller than that of Si and GaN, and the band gap of AlN is larger than that of Si and GaN, while the lattice constant and the band gap of BP are between those of Si and GaN, and BP can well play a buffering transition role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, after the growth of the high-temperature BP nucleation layer is completed, the pre-deposited Al layer is grown, which can avoid the reaction growth of BN caused by the contact between NH3 and BP, because there is a large lattice mismatch between BN and GaN, thereby avoiding the increase of the dislocation density of the GaN epitaxial layer. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0030] Figure 1 is a HEMT epitaxial wafer preparation method flow chart provided by the embodiment of the present disclosure;

[0031] Figure 2 is a HEMT epitaxial wafer preparation method flow chart provided by the embodiment of the present disclosure;

[0032] Figure 3 is a structure schematic diagram of a HEMT epitaxial wafer provided by the embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in combination with the drawings.

[0034] Unless otherwise defined, technical terms or scientific terms used herein should be understood as their common meanings to those having ordinary skill in the art to which the present disclosure pertains. The terms "first", "second", "third" and similar terms used in the specification and claims of the present patent application do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, the terms "one" or "a" and the like do not denote a quantity limitation, but mean that at least one exists. The terms "include" or "contain" and the like mean that the elements or objects appearing before the "include" or "contain" cover the elements or objects listed after the "include" or "contain" and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and the like are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right", "top", "bottom" and the like are only used to indicate relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0035] Figure 1 is a HEMT epitaxial wafer preparation method flow chart provided by the embodiment of the present disclosure, referring to Figure 1 The embodiment of the present disclosure provides a HEMT epitaxial wafer preparation method, and the preparation method of the HEMT epitaxial wafer comprises the following steps.

[0036] S101: providing a Si substrate.

[0037] The Si substrate can be a (111) crystal direction Si substrate.

[0038] S102: growing a composite transition layer on the Si substrate, the composite transition layer comprising a low-temperature BP nucleation layer, a high-temperature BP nucleation layer and a pre-deposited Al layer stacked in sequence on the Si substrate, the growth temperature of the low-temperature BP nucleation layer being lower than the growth temperature of the high-temperature BP nucleation layer.

[0039] Exemplarily, the growth temperature of the low-temperature BP nucleation layer ranges from 600 to 800 degrees Celsius, and the growth temperature of the high-temperature BP nucleation layer ranges from 900 to 1100 degrees Celsius; for example, the growth temperature of the low-temperature BP nucleation layer is 700 degrees Celsius, and the growth temperature of the high-temperature BP nucleation layer is 1000 degrees Celsius.

[0040] The thickness of the low-temperature BP nucleation layer ranges from 10 to 40 nanometers, and the thickness of the high-temperature BP nucleation layer ranges from 150 to 250 nanometers; for example, the thickness of the low-temperature BP nucleation layer is 25 nanometers, and the thickness of the high-temperature BP nucleation layer is 200 nanometers.

[0041] The growth pressure of the low-temperature BP nucleation layer ranges from 200 to 300 mbar, and the growth pressure of the high-temperature BP nucleation layer ranges from 50 to 100 mbar; for example, the growth pressure of the low-temperature BP nucleation layer is 250 mbar, and the growth pressure of the high-temperature BP nucleation layer is 75 mbar.

[0042] Exemplarily, the growth temperature of the pre-deposited Al layer ranges from 900 to 1100 degrees Celsius, the growth pressure of the pre-deposited Al layer ranges from 40 to 70 mbar, and the thickness of the pre-deposited Al layer ranges from 1 to 5 nanometers; for example, the growth temperature of the pre-deposited Al layer is 1000 degrees Celsius, the growth pressure of the pre-deposited Al layer is 55 mbar, and the thickness of the pre-deposited Al layer is 3.5 nanometers.

[0043] S103: sequentially growing an AlGaN buffer layer, an AlGaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer on the composite transition layer.

[0044] Exemplarily, the AlGaN buffer layer is an undoped AlGaN layer, the thickness of the AlGaN buffer layer ranges from 2.0 to 3.0 micrometers, and the Al component ranges from 0.2 to 0.8, which can ensure the quality of the AlGaN buffer layer.

[0045] Exemplarily, the thickness of the AlGaN high-resistance layer ranges from 1.0 to 2.0 micrometers, which can ensure the growth quality of the AlGaN high-resistance layer itself and effectively achieve the purpose of high resistance, that is, the high-resistance effect can be ensured.

[0046] Exemplarily, the AlGaN high-resistance layer is doped with C, and the doping concentration of the carbon element is 10 19 cm -3 -10 20 cm -3 The AlGaN high-resistance layer doped with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element in the above range can also ensure the quality of the AlGaN high-resistance layer itself.

[0047] Exemplarily, the thickness of the GaN channel layer ranges from 300nm to 600nm, so that the quality of the GaN channel layer is better, and the quality of the finally obtained HEMT epitaxial wafer is improved.

[0048] For example, the thickness of the GaN channel layer is 400nm. The thickness of the GaN channel layer is appropriate, and the cost is reasonable while the quality of the HEMT epitaxial wafer can be effectively improved.

[0049] Exemplarily, the thickness of the AlGaN barrier layer ranges from 20nm to 25nm, which can ensure the quality of the HEMT epitaxial wafer.

[0050] Exemplarily, the GaN cap layer can be a P-type GaN layer, which is convenient to prepare and obtain.

[0051] Optionally, the thickness of the GaN cap layer ranges from 3nm to 5nm, and the quality of the obtained GaN cap layer as a whole is better.

[0052] Exemplarily, the impurity in the GaN cap layer is Mg, which is convenient to prepare and obtain.

[0053] The nucleation layer is set as a double-layer structure composed of a low-temperature BP nucleation layer and a high-temperature BP nucleation layer. Compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth. When AlN is used as the nucleation layer, the lattice constant is smaller than that of Si and GaN, and the band gap is larger than that of Si and GaN, and the lattice constant and the band gap of BP are between Si and GaN, which can well play the role of buffer transition between Si substrate and GaN epitaxial layer, which is conducive to reducing the lattice mismatch between Si substrate and epitaxial layer and improving the crystal quality. In addition, after the growth of the high-temperature BP nucleation layer is completed, the pre-deposition Al layer is grown, which can avoid the reaction of NH3 and BP to grow BN, because there is a large lattice mismatch between BN and GaN, thereby avoiding the increase of the dislocation density of the GaN epitaxial layer.

[0054] Figure 2 is another flow chart of a HEMT epitaxial wafer preparation method provided by the embodiment of the present disclosure, referring to Figure 2 The HEMT epitaxial wafer preparation method can include:

[0055] S201: providing a Si substrate.

[0056] The Si substrate can be a (111) crystal direction Si substrate.

[0057] Optionally, step S201 comprises: placing the Si substrate into a metal-organic chemical vapor deposition (MOVCD) system, and processing the surface of the Si substrate under a hydrogen (H2) atmosphere, at a temperature of 1000-1200 DEG C, and a pressure of 50-150 mbar for 5-10 min, so as to remove impurities (such as oxides) on the surface of the Si substrate.

[0058] S202: growing a composite transition layer on the Si substrate.

[0059] In a possible implementation of the present disclosure, the growth process of the composite transition layer is as follows:

[0060] In the first step, a low-temperature BP nucleation layer with a thickness of 10-40 nm is grown under a growth temperature of 600-800 DEG C and a growth pressure of 200-300 mbar.

[0061] For example, the first step can comprise: growing the low-temperature BP nucleation layer under a temperature of 600-800 DEG C and a pressure of 200-300 mbar, with a V / III ratio of 500-800 during growth, and the low-temperature BP nucleation layer being in a three-dimensional island growth mode.

[0062] In the second step, a high-temperature BP nucleation layer with a thickness of 150-250 nm is grown under a growth temperature of 900-1100 DEG C and a growth pressure of 50-100 mbar.

[0063] For example, the second step can comprise: growing the high-temperature BP nucleation layer under a temperature of 900-1100 DEG C and a pressure of 50-100 mbar, with a V / III ratio of 50-80 during growth, and the low-temperature BP nucleation layer being in a two-dimensional flat growth mode.

[0064] In the third step, a pre-deposited Al layer with a thickness of 1-5 nm is grown under a growth temperature of 900-1100 DEG C and a growth pressure of 40-70 mbar.

[0065] Exemplarily, the third step can comprise: introducing the Al source into the reaction cavity at a flow rate of 50-200 sccm under a temperature condition of 900-1100℃ and a pressure condition of 40-70 mbar, and the introduction time is 10-20 seconds (s), without NH3, and a layer of Al film is pre-deposited on the surface of the high-temperature BP nucleation layer after the decomposition of the Al source, that is, a pre-deposited Al layer.

[0066] The Al source can be trimethylaluminum (TMAl).

[0067] By setting the nucleation layer into a double-layer structure composed of the low-temperature BP nucleation layer and the high-temperature BP nucleation layer, compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth. When AlN is used as the nucleation layer, its lattice constant is smaller than that of Si and GaN, and its band gap is larger than that of Si and GaN, while the lattice constant and the band gap of BP are between those of Si and GaN, which can well play the role of buffer transition between the Si substrate and the GaN epitaxial layer, and is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, after the growth of the high-temperature BP nucleation layer is completed, the pre-deposited Al layer is grown, which can avoid the reaction growth of BN by contacting NH3 with BP, because there is a large lattice mismatch between BN and GaN, thereby avoiding the increase of the dislocation density of the GaN epitaxial layer.

[0068] And by using the above growth conditions and thickness to grow the high-temperature BP nucleation layer, the low-temperature BP nucleation layer and the pre-deposited Al layer, the obtained high-temperature BP nucleation layer, the low-temperature BP nucleation layer and the pre-deposited Al layer can meet the above requirements of relieving the lattice mismatch and improving the crystal quality.

[0069] S203: growing an AlGaN buffer layer on the composite transition layer.

[0070] Optionally, the growth conditions of the AlGaN buffer layer include: the growth temperature is 1050-1200℃, the pressure is 40-70 mbar, NH3 and MO source (trimethylgallium TMGa and trimethylaluminum TMAl) are introduced into the reaction cavity to grow the AlGaN buffer layer. The AlGaN buffer layer is an undoped AlGaN layer, the thickness is 2.0-3.0 microns, and the Al component is 0.2-0.8, which can obtain a better quality AlGaN buffer layer.

[0071] S204: growing an AlGaN high-resistance layer on the AlGaN buffer layer.

[0072] The AlGaN high-resistance layer is grown on the AlGaN buffer layer, so that the lattice mismatch between the AlGaN buffer layer and the AlGaN high-resistance layer can be effectively reduced, the crystal quality of the obtained AlGaN high-resistance layer is improved, and the quality of the AlGaN high-resistance layer is guaranteed, so that the quality of other epitaxial materials grown on the AlGaN high-resistance layer is further improved.

[0073] Exemplarily, the growth temperature of the AlGaN high-resistance layer is in a range of 1000-1200℃, and the growth pressure of the AlGaN high-resistance layer is in a range of 40-70mbar.

[0074] The growth temperature and the growth pressure of the AlGaN high-resistance layer are in the above ranges respectively, so that the growth quality of the obtained AlGaN high-resistance layer is effectively improved.

[0075] Optionally, the thickness of the AlGaN high-resistance layer is in a range of 1.0-2.0 microns, so that the growth quality of the AlGaN high-resistance layer itself is guaranteed, and the high-resistance purpose is effectively achieved, that is, the high-resistance effect is guaranteed.

[0076] Optionally, the AlGaN high-resistance layer is doped with carbon (C), and the doping concentration of the carbon element is in a range of 10 19 cm -3 -10 20 cm -3 .

[0077] The AlGaN high-resistance layer doped with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element in the above range can also guarantee the quality of the AlGaN high-resistance layer itself.

[0078] Optionally, the Al component of the AlGaN high-resistance layer is in a range of 0.1-0.3.

[0079] S205: growing a GaN channel layer on the AlGaN high-resistance layer.

[0080] Optionally, the growth conditions of the GaN channel layer include that the growth temperature is in a range of 1050-1150℃, and the pressure is in a range of 150-250mbar. The GaN channel layer with good quality can be obtained.

[0081] Exemplarily, the thickness of the GaN channel layer is in a range of 300-600nm, so that the quality of the obtained GaN channel layer is good, and the quality of the finally obtained HEMT epitaxial wafer is improved.

[0082] S206: growing an AlN insertion layer on the GaN channel layer.

[0083] Optionally, the growth conditions of the AlN insertion layer include: a growth temperature of 1000-1100°C and a pressure of 30-70 mbar. A high-quality AlN insertion layer can be obtained.

[0084] Optionally, the thickness of the AlN insertion layer is 0.8-1.2 nm. For example, the thickness of the AlN insertion layer is 1 nm.

[0085] S207: growing an AlGaN barrier layer on the AlN insertion layer.

[0086] Optionally, the growth temperature of the AlGaN barrier layer is 1000-1100°C, and the growth pressure of the AlGaN barrier layer is 40-70 mbar. A high-quality AlGaN barrier layer can be obtained.

[0087] In an implementation provided by the present disclosure, the growth temperature of the AlGaN barrier layer can be 1050°C. The present disclosure does not limit this.

[0088] Optionally, the thickness of the AlGaN barrier layer is 20-25 nm.

[0089] Optionally, the Al component in the AlGaN barrier layer is 0.20-0.25.

[0090] S208: growing a GaN cap layer on the AlGaN barrier layer.

[0091] Optionally, the growth temperature of the GaN cap layer is 1000-1100°C, and the growth pressure of the AlGaN barrier layer is 100-200 mbar. A high-quality GaN cap layer can be obtained.

[0092] Optionally, the thickness of the GaN cap layer is 3-5 nm.

[0093] Optionally, after the epitaxial structure is grown, the temperature of the reaction cavity is reduced, and the epitaxial growth is completed at room temperature in a nitrogen atmosphere.

[0094] It should be noted that in the embodiments of the present disclosure, the growth method of the LED is realized by using a Veeco K 465i or C4 or RB MOCVD (Metal Organic Chemical Vapor Deposition) device. High-purity H2 (hydrogen) or high-purity N2 (nitrogen) or a mixed gas of high-purity H2 and high-purity N2 is used as a carrier gas, high-purity NH3 is used as an N source, trimethyl gallium (TMGa) and triethyl gallium (TEGa) are used as gallium sources, trimethyl indium (TMIn) is used as an indium source, silane (SiH4) is used as an N-type dopant, trimethyl aluminum (TMAl) is used as an aluminum source, and dimethyl magnesium (CP2Mg) is used as a P-type dopant, ferrocene (Cp2Fe) is used as a ferrous (Fe) source precursor. Carbon tetrabromide (CBr4) is used as a carbon (C) source precursor, and Cl2 is used as an etching gas.

[0095] Figure 3 is a structural schematic diagram of a HEMT epitaxial wafer provided by the present disclosure. Referring to Figure 3 , the HEMT epitaxial wafer comprises:

[0096] a Si substrate 1, a composite transition layer 2, an AlGaN buffer layer 3, an AlGaN high-resistance layer 4, a GaN channel layer 5, an AlGaN barrier layer 6, and a GaN cap layer 7 which are sequentially stacked on the Si substrate 1.

[0097] The composite transition layer 2 comprises a low-temperature BP nucleation layer 21, a high-temperature BP nucleation layer 22, and a pre-deposited Al layer 23 which are sequentially stacked on the Si substrate 1, and the growth temperature of the low-temperature BP nucleation layer 21 is lower than that of the high-temperature BP nucleation layer 22.

[0098] For example, the growth temperature of the low-temperature BP nucleation layer is in the range of 600-800℃, and the growth temperature of the high-temperature BP nucleation layer is in the range of 900-1100℃.

[0099] The thickness of the low-temperature BP nucleation layer is in the range of 10-40nm, and the growth temperature of the high-temperature BP nucleation layer is in the range of 150-250nm.

[0100] The growth pressure of the low-temperature BP nucleation layer is in the range of 200-300mbar, and the growth pressure of the high-temperature BP nucleation layer is in the range of 50-100mbar.

[0101] For example, the growth temperature of the pre-deposited Al layer is in the range of 900-1100℃, the growth pressure of the pre-deposited Al layer is in the range of 40-70mbar, and the thickness of the pre-deposited Al layer is in the range of 1-5nm.

[0102] The following Table 1 is a table of lattice field numbers and band gap widths of Si, BP, GaN, AlN and the like. As can be seen from Table 1:

[0103] Compared with a conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch with the GaN epitaxial layer, and can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer. When AlN is used as the nucleation layer, the lattice constant of AlN is smaller than that of Si and GaN, and the band gap of AlN is larger than that of Si and GaN. The lattice constant and the band gap of BP are between those of Si and GaN, and BP can well play a buffering and transitional role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, after the growth of the high-temperature BP nucleation layer is completed, the growth of the pre-deposited Al layer is performed, which can avoid the reaction and growth of BN caused by the contact between NH3 and BP, thereby avoiding the increase of the dislocation density of the GaN epitaxial layer.

[0104] Table 1

[0105] Parameter / substance Si BP GaN AlN Lattice constant (nm) 0.5431 0.4538 0.3189 0.3112 Band gap (eV) 1.12 2.0 3.4 6.2

[0106] The growth of the high-temperature BP nucleation layer, the low-temperature BP nucleation layer and the pre-deposited Al layer under the above growth conditions and thicknesses can ensure that the obtained high-temperature BP nucleation layer, the low-temperature BP nucleation layer and the pre-deposited Al layer meet the above requirements of relieving the lattice mismatch and improving the crystal quality.

[0107] Optionally, the HEMT epitaxial wafer further comprises an AlN insertion layer 8 located between the GaN channel layer and the AlGaN barrier layer.

[0108] For example, the thickness of the AlN insertion layer is 1 nm.

[0109] For example, the thickness of the AlN insertion layer is 1 nm.

[0110] For example, the thickness of the AlN insertion layer is 1 nm.

[0111] For example, the thickness of the AlN insertion layer is 1 nm.

[0112] For example, the thickness of the AlN insertion layer is 1 nm. 19 cm -3 -10 20 cm-3 The doping of the AlGaN high-resistance layer with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element in the above range can also ensure the quality of the AlGaN high-resistance layer itself.

[0113] For example, the thickness of the GaN channel layer is 300-600 nm, so that the quality of the GaN channel layer is good, and the quality of the finally obtained HEMT epitaxial wafer is improved.

[0114] For example, the thickness of the GaN channel layer is 400 nm. The thickness of the GaN channel layer is appropriate, the cost is reasonable, and the quality of the HEMT epitaxial wafer can be effectively improved.

[0115] For example, the thickness of the AlGaN barrier layer is 20-25 nm, which can ensure the quality of the HEMT epitaxial wafer.

[0116] For example, the GaN cap layer can be a P-type GaN layer, which is convenient to prepare and obtain.

[0117] Optionally, the thickness of the GaN cap layer is 3-5 nm, and the quality of the obtained GaN cap layer as a whole is good.

[0118] For example, the impurity in the GaN cap layer is Mg, which is convenient to prepare and obtain.

[0119] It should be noted that, Figure 3 The above is only one implementation of the HEMT epitaxial wafer provided by the embodiments of the present disclosure, and in other implementations provided by the present disclosure, the HEMT epitaxial wafer can also be other forms of HEMT epitaxial wafer including a reflection layer, and the present disclosure does not limit this.

[0120] The embodiments of the present disclosure provide a HEMT device, which includes an HEMT epitaxial wafer as shown in the above. Figure 3

[0121] The above is not intended to limit the present disclosure in any form, although the present disclosure has been disclosed as above through embodiments, however, it is not intended to limit the present disclosure, any person skilled in the art, without departing from the technical solution range of the present disclosure, can make some changes or modifications to the above disclosed technical content for equivalent embodiments, as long as it does not deviate from the technical solution of the present disclosure, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present disclosure, all still belong to the range of the technical solution of the present disclosure.​

Claims

1. A HEMT epitaxial wafer, characterized in that, The HEMT epitaxial wafer includes: A Si substrate, a composite transition layer, an AlGaN buffer layer, an AlGaN high-resistivity layer, a GaN channel layer, an AlGaN barrier layer, and a GaN capping layer are sequentially stacked on the Si substrate. The composite transition layer includes a low-temperature BP nucleation layer, a high-temperature BP nucleation layer, and a pre-laid Al layer sequentially stacked on the Si substrate. The growth temperature of the low-temperature BP nucleation layer is lower than that of the high-temperature BP nucleation layer. The pre-laid Al layer is an Al film formed on the surface of the high-temperature BP nucleation layer after the Al source introduced into the reaction chamber decomposes.

2. The HEMT epitaxial wafer according to claim 1, characterized in that, The growth temperature of the low-temperature BP nucleation layer ranges from 600℃ to 800℃, and the growth temperature of the high-temperature BP nucleation layer ranges from 900℃ to 1100℃. The thickness of the low-temperature BP nucleation layer ranges from 10 nm to 40 nm, and the thickness of the high-temperature BP nucleation layer ranges from 150 nm to 250 nm. The growth pressure of the low-temperature BP nucleation layer ranges from 200 mbar to 300 mbar, and the growth pressure of the high-temperature BP nucleation layer ranges from 50 mbar to 100 mbar.

3. The HEMT epitaxial wafer according to claim 1, characterized in that, The growth temperature of the pre-laid Al layer ranges from 900℃ to 1100℃, the growth pressure of the pre-laid Al layer ranges from 40mbar to 70mbar, and the thickness of the pre-laid Al layer ranges from 1nm to 5nm.

4. The HEMT epitaxial wafer according to any one of claims 1 to 3, characterized in that, The HEMT epitaxial wafer further includes an AlN insertion layer located between the GaN channel layer and the AlGaN barrier layer.

5. A method for preparing a HEMT epitaxial wafer, characterized in that, The preparation method includes: Provide a Si substrate; A composite transition layer is grown on the Si substrate. The composite transition layer includes a low-temperature BP nucleation layer, a high-temperature BP nucleation layer, and a pre-laid Al layer, which are sequentially stacked on the Si substrate. The pre-laid Al layer is an Al film formed on the surface of the high-temperature BP nucleation layer after the Al source introduced into the reaction chamber is decomposed. An AlGaN buffer layer, an AlGaN high-resistivity layer, a GaN channel layer, an AlGaN barrier layer, and a GaN capping layer are sequentially grown on the composite transition layer.

6. The preparation method according to claim 5, characterized in that, The growth of the composite transition layer on the Si substrate includes: preparing the low-temperature BP nucleation layer in the following manner: The low-temperature BP nucleation layer is grown under the conditions of a growth temperature ranging from 600℃ to 800℃, a growth pressure ranging from 200mbar to 300mbar, and a thickness ranging from 10nm to 40nm.

7. The preparation method according to claim 5, characterized in that, The growth of the composite transition layer on the Si substrate includes: preparing the high-temperature BP nucleation layer in the following manner: The high-temperature BP nucleation layer is grown under the conditions of a growth temperature ranging from 900℃ to 1100℃, a growth pressure ranging from 50mbar to 100mbar, and a thickness ranging from 150nm to 250nm.

8. The preparation method according to claim 5, characterized in that, The growth of the composite transition layer on the Si substrate includes: preparing the pre-laid Al layer in the following manner: The pre-laid Al layer is grown at a temperature ranging from 900℃ to 1100℃, a growth pressure ranging from 40mbar to 70mbar, and a thickness ranging from 1nm to 5nm.

9. The preparation method according to any one of claims 5 to 8, characterized in that, The preparation method further includes: An AlN insertion layer is grown between the GaN channel layer and the AlGaN barrier layer.

10. A HEMT device, characterized in that, The HEMT device includes the HEMT epitaxial wafer as described in any one of claims 1 to 4.

Images