A nitride thin film and a method for preparing the same

Abstract

The application aims to provide a nitride film and a preparation method thereof, and belongs to the technical field of semiconductor epitaxy process. The nitride film comprises a buffer layer on a substrate, and alternately deposited heavily doped nitride layers and unintentionally doped nitride layers on the buffer layer. The heavily doped nitride layers have a rough surface structure, and the unintentionally doped nitride layers have a flat surface structure. The rough structure of the heavily doped nitride layers can cause bending and termination of dislocations, thereby reducing the dislocation density in the subsequently grown epitaxial film. The rough heavily doped nitride layers are also beneficial to stress release, thereby reducing the stress in the epitaxial film. The flat surface of the unintentionally doped nitride layers has a low surface roughness, thereby providing a good growth surface for the subsequent growth of the epitaxial film. Therefore, the alternately deposited heavily doped nitride layers and unintentionally doped nitride layers can reduce the defects in the subsequently grown epitaxial film, thereby being beneficial to improving the device performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor epitaxy process, and particularly relates to a nitride film and a preparation method thereof. BACKGROUND

[0002] III-nitride semiconductor materials represented by GaN have wide application prospects in the fields of optoelectronic devices and electronic devices due to their wide band gap, high breakdown field and high electron saturation velocity, and are currently a research hotspot in the global semiconductor field.

[0003] Currently, nitride materials such as GaN and AlN are mainly grown by hetero-epitaxy on sapphire substrates, SiC or Si substrates. However, there is a large lattice mismatch and thermal mismatch between the hetero-substrate and the nitride material, resulting in a large number of defects such as dislocations, V-pits and stacking faults in the epitaxial film, which seriously affect the performance of the device.

[0004] Lateral epitaxial growth technology and patterned substrate growth technology are used to reduce the dislocation density in the epitaxial film. The principle is to first pattern the substrate (thin film), and then filter the dislocations by using a special epitaxial growth technology. However, the cost of the patterned substrate (thin film) is relatively high, and the lateral epitaxial growth speed is relatively low, which will significantly increase the process time and manufacturing cost. In addition, the quality of the epitaxial film is strongly dependent on the shape, size, angle and other parameters of the pattern, and it is not easy to accurately control these parameters on a large area. SUMMARY

[0005] The present application aims to solve the above-mentioned defects in the prior art, and provides a nitride film and a preparation method thereof, which can effectively reduce the density of defects such as dislocations in the epitaxial film, and the preparation method is simple and has low manufacturing cost.

[0006] The application adopts the following technical scheme:

[0007] A nitride film, comprising a substrate, a buffer layer on the substrate, and alternately deposited heavily doped nitride layers and unintentionally doped nitride layers on the buffer layer, wherein the number of periods of the alternately deposited heavily doped nitride layers and unintentionally doped nitride layers is 1-1000, the heavily doped nitride layers have a rough surface structure, and the unintentionally doped nitride layers have a flat surface structure.

[0008] Further, the substrate comprises any one of Si, SiC, GaN and sapphire.

[0009] Further, the thickness of the buffer layer is 1-5000 nm, and the buffer layer comprises any one of GaN, AlN, AlGaN, AlGaN / GaN and AlN / GaN.

[0010] Further, the nitride of the heavily doped nitride layer comprises any one of GaN, AlN, AlGaN, and the doping element is Si, and the doping concentration is 5x1018~5x1021cm-3. 18 21 cm -3 .

[0011] Further, the nitride of the unintentionally doped nitride layer comprises any one of GaN, AlN, AlGaN.

[0012] Further, the thickness of the heavily doped nitride layer is 1~5000nm, and the thickness of the unintentionally doped nitride layer is 1~5000nm.

[0013] Further, the rough surface structure has a 3D island growth structure, and the flat surface structure has a 2D layer growth structure.

[0014] A preparation method of a nitride thin film, comprising the following steps:

[0015] Step 1: growing a buffer layer on a substrate;

[0016] Step 2: alternately depositing a heavily doped nitride layer and an unintentionally doped nitride layer on the buffer layer to obtain the nitride thin film.

[0017] Further, the substrate needs to be cleaned and surface-nitrided, and the substrate is placed in a metal organic chemical vapor deposition device cavity, baked in H2atmosphere for 1~30min at a temperature of 1000~1500℃, and then NH3is introduced to perform substrate surface nitriding for 5~500s.

[0018] Further, the buffer layer is grown on the substrate at a growth temperature of 450~1500℃, a V / III ratio of 20~50000, and a pressure of 50~750Torr, and the carrier gas comprises N2, H2or N2 / H2mixed gas.

[0019] Further, the heavily doped nitride layer and the unintentionally doped nitride layer are alternately deposited on the buffer layer, first, the epitaxial growth of the heavily doped nitride layer uses SiH4or Si2H6to provide the doping element Si, uses N2and H2as carrier gas, and uses island growth mode or layer-island hybrid mode to form a heavily doped nitride layer with island structure, and the growth temperature is 600~1500℃, the V / III ratio is 20~50000, and the pressure is 50~750Torr;

[0020] ​The epitaxial growth of the unintentionally doped nitride layer does not need a dopant, uses N2 or H2 or a mixed gas of N2 / H2 as a carrier gas, the growth temperature is 600-1500℃, the V / III ratio is 20-50000, the pressure is 50-750 Torr, and the unintentionally doped nitride layer with a flat surface is formed by using a layer growth mode;

[0021] Finally, the growth process of the heavily doped GaN layer and the unintentionally doped GaN layer is repeated to realize a multi-period stacking structure.

[0022] The beneficial effects of the present application are as follows:

[0023] In the heteroepitaxial thin film growth process, due to the large lattice mismatch between the epitaxial layer and the hetero-substrate, stress accumulates in the epitaxial film, resulting in a large number of dislocations and other defects. The buffer layer technology can reduce the dislocation density to a certain extent and improve the quality of the epitaxial film, but the dislocation density in the nitride epitaxial film is still high. The present application proposes to introduce a multi-layer structure of alternately deposited heavily doped nitride layer / unintentionally doped nitride layer on the buffer layer. First, during the deposition of the heavily doped nitride layer, the heavy doping will cause the surface to be roughened, and the rough heavily doped nitride layer can cause the bending and termination of dislocations on one hand and reduce the dislocation density in the epitaxial film on the other hand. Second, the unintentionally doped nitride layer is grown on the rough heavily doped nitride layer, and the unintentionally doped nitride layer has a flat surface, which provides a good growth surface for the subsequent growth of the epitaxial film. The heavily doped nitride layer / unintentionally doped nitride layer can be alternately deposited multiple times, and each deposition of the heavily doped nitride layer will cause the bending or termination of dislocations, while the unintentionally doped nitride layer will repair the surface to make it flat. After multiple alternately deposited, a low dislocation density and high-quality nitride substrate can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structure schematic diagram of the GaN thin film of the embodiment 1 of the present application;

[0025] Figure 2 It is a structure schematic diagram of the GaN thin film of the embodiment 2 of the present application;

[0026] Figure 3 It is a structure schematic diagram of the AlN thin film of the embodiment 3 of the present application;

[0027] Figure 4 It is a structure schematic diagram of the AlGaN thin film of the embodiment 4 of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described below with reference to the drawings.

[0029] Embodiment 1

[0030] Referring to Figure 1 As shown in the figure, a GaN film is disclosed, comprising:

[0031] A substrate, in this embodiment, the substrate is a sapphire substrate, and in other embodiments, it can also be other substrate materials, such as Si, SiC, GaN, etc.

[0032] A buffer layer on the sapphire substrate, the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, AlN / GaN, and in this embodiment, the buffer layer is GaN, and the thickness of the buffer layer is 1-5000 nm.

[0033] A heavily doped GaN layer on the buffer layer, the heavily doped GaN layer has an island structure, and the thickness of the heavily doped GaN layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×10 18 ~1×10 21 cm -3 , preferably 8.5×10 18 cm -3 , 5.5×10 19 cm -3 , 8.5×10 19 cm -3 , 1.5×10 20 cm -3 , 2.5×10 20 cm -3 , 4.5×10 20 cm -3 , 7.5×10 20 cm -3 .

[0034] An unintentionally doped GaN layer on the heavily doped GaN layer, the thickness of the unintentionally doped layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm.

[0035] The specific preparation method is as follows:

[0036] A substrate is provided, selected from one of sapphire, Si, SiC, and GaN, and in this embodiment, it is a sapphire substrate, the substrate is cleaned and surface nitrided, specifically: the substrate is placed in a metal organic chemical vapor deposition (MOCVD) equipment cavity, baked in an H2 atmosphere for 1-30 min at a temperature of 1000-1500°C, and then NH3 is introduced to perform surface nitridation of the substrate, and the nitridation time is 5-300 s.

[0037] Growth of a buffer layer on the substrate, the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, AlN / GaN, the buffer layer is GaN in the embodiment, the growth temperature is 450-1300℃, the V / III ratio is 50-50000, the pressure is 50-750 Torr, and the carrier gas is selected from N2, H2, and N2 / H2 mixed gas. The thickness of the buffer layer is 1-5000 nm.

[0038] Deposition of a heavily doped GaN layer on the buffer layer: first, TMG and NH3 are introduced, N2 and H2 are introduced as carrier gas, SiH4 or Si2H6 is introduced to provide the doping element Si, island growth mode or layer-island mixed mode is adopted to form a heavily doped GaN layer with island structure, the growth temperature is 600-1500℃, the V / III ratio is 50-50000, and the pressure is 50-750 Torr.

[0039] Growth of an unintentionally doped GaN layer (u-GaN) on the heavily doped GaN layer: the doping source SiH4 is turned off, TMG and NH3 are introduced, N2 and H2 are introduced as carrier gas, and the unintentionally doped GaN layer is grown in a layer growth mode by increasing the growth temperature, reducing the growth pressure, or reducing the growth rate.

[0040] The thickness of the heavily doped GaN layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×1018-1×1021 cm-3, preferably 8.5×1018, 5.5×1018, 8.5×1019, 1.5×1019, 2.5×1019, 4.5×1019, or 7.5×1019 cm-3; the thickness of the unintentionally doped layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm. 18 ~1×10 21 cm -3 , preferably 8.5×10 18 cm -3 , 5.5×10 19 cm -3 , 8.5×10 19 cm -3 , 1.5×10 20 cm -3 , 2.5×10 20 cm -3 , 4.5×10 20 cm -3 , or 7.5×10 20 cm -3 .

[0041] Embodiment 2

[0042] Referring to Figure 2 As shown in the figure, a GaN film is disclosed, comprising:

[0043] a substrate, in this embodiment, the substrate is a sapphire substrate, and in other embodiments, it can also be other substrate materials, such as Si, SiC, GaN, etc.;

[0044] a buffer layer on the sapphire substrate, the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, AlN / GaN, and in this embodiment, the buffer layer is GaN, and the thickness of the buffer layer is 1-5000 nm;

[0045] an alternating stack structure of heavily doped GaN layers and unintentionally doped GaN layers on the GaN buffer layer, the heavily doped GaN layers have an island structure, the thickness of the heavily doped GaN layers is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×10 18 ~1×10 21 cm -3 , preferably 8.5×10 18 cm -3 , 5.5×10 19 cm -3 , 8.5×10 19 cm -3 , 1.5×10 20 cm -3 , 2.5×10 20 cm -3 , 4.5×10 20 cm -3 , 7.5×10 20 cm -3 . The thickness of the unintentionally doped GaN layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm.

[0046] The specific preparation method is as follows:

[0047] A substrate is provided, which is selected from one of sapphire, Si, SiC, and GaN, and in this embodiment, it is a sapphire substrate, the substrate is cleaned and surface nitrided, specifically: the substrate is placed in a metal organic chemical vapor deposition (MOCVD) equipment cavity, baked in an H2 atmosphere for 1-30 min at a temperature of 1000-1500°C, and then NH3 is introduced to perform surface nitridation of the substrate, and the nitridation time is 5-300 s.

[0048] Growth of a buffer layer on a substrate, the buffer layer has a thickness of 1-5000 nm, the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, AlN / GaN, and in this embodiment, the buffer layer is GaN, the growth temperature is 450-1300 °C, the V / III ratio is 50-50000, the pressure is 50-750 Torr, and the carrier gas is selected from N2, H2, and N2 / H2 mixed gas.

[0049] A stack structure of a heavily doped GaN layer and an unintentionally doped GaN layer is alternately deposited on the buffer layer. First, the heavily doped GaN layer is grown, TMG and NH3 are introduced, N2 and H2 are introduced as carrier gas, SiH4 is introduced to provide the doping element Si, the heavily doped GaN layer with island structure is formed by using island growth mode or layer-island mixed mode, the growth temperature is 600-1500 °C, the V / III ratio is 50-50000, and the pressure is 50-750 Torr; then, the unintentionally doped GaN layer is grown, the doping source SiH4 is turned off, TMG and NH3 are introduced, N2 and H2 are introduced as carrier gas, and the unintentionally doped GaN layer is grown by layer growth mode by increasing the growth temperature, reducing the growth pressure or the growth rate. Finally, the growth process of the heavily doped GaN layer and the unintentionally doped GaN layer is repeated to realize a multi-period stack structure. In this embodiment, the number of stack periods of the heavily doped GaN layer and the unintentionally doped GaN layer is 2-1000, preferably 5, 10, 20, 50, 100, 200, or 500.

[0050] In this embodiment, the thickness of the heavily doped GaN layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×1018-1×1021 cm-3, preferably 8.5×1018, 5.5×1018, 8.5×1019, 1.5×1019, 2.5×1019, 4.5×1019, 7.5×1019, or 1×1020 cm-3. 18 ~1×10 21 cm -3 , preferably 8.5×1018 18 cm -3 , 5.5×1018 19 cm -3 , 8.5×1019 19 cm -3 , 1.5×1019 20 cm -3 , 2.5×1019 20 cm -3 , 4.5×1019 20 cm -3 , or 7.5×1019 20 cm -3The unintentionally doped GaN layer has a thickness of 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm.

[0051] Embodiment 3

[0052] Referring to Figure 3 The application discloses an AlN film, comprising:

[0053] A substrate, in the embodiment, the substrate is a sapphire substrate, and in other embodiments, the substrate can be other substrate materials, such as Si, SiC, GaN, etc.

[0054] A buffer layer on the sapphire substrate, the buffer layer has a thickness of 1-5000 nm, and the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN and AlN / GaN; in the embodiment, the buffer layer is AlN.

[0055] Alternately deposited heavily doped AlN layers / unintentionally doped AlN layers on the buffer layer, the number of cycles of the alternately deposited heavily doped AlN layers and unintentionally doped AlN layers is 1-1000, preferably 5, 10, 20, 50, 100, 200, 500.

[0056] The heavily doped layer has an island structure, the heavily doped layer has a thickness of 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×1018-1×1021 cm-3, preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 18 ~1×10 21 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 18 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 19 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 19 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 20 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 20 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 20 cm -3 , preferably 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 2.5×1019 cm-3, 4.5×1019 cm-3, 7.5×1019 cm-3. 20 cm -3 The unintentionally doped layer has a thickness of 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm.

[0057] The specific preparation method is as follows:

[0058] A substrate is provided, which is selected from sapphire, Si, SiC, GaN, and in this embodiment, the substrate is a sapphire substrate. The substrate is cleaned and surface-nitrided. Specifically, the substrate is placed in a chamber of a metal organic chemical vapor deposition (MOCVD) device, baked in an H2 atmosphere for 2-20 min at a temperature of 1000-1300 °C, and then surface-nitrided by introducing NH3, with a nitriding time of 20-500 s.

[0059] A buffer layer is grown on the substrate, with a thickness of 1-5000 nm, and the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, and AlN / GaN. In this embodiment, the buffer layer is AlN, and the growth temperature is 500-1500 °C, the V / III ratio is 20-50000, the pressure is 50-750 Torr, and the carrier gas is selected from N2, H2, and a mixture of N2 / H2.

[0060] The heavily-doped AlN layer and the unintentionally-doped AlN layer are alternately deposited on the buffer layer. In one growth cycle of the heavily-doped AlN layer / unintentionally-doped AlN layer, TMAl and NH3 are first introduced, N2 and H2 are introduced as carrier gases, and SiH4 is introduced to provide a doping element Si. The heavily-doped AlN layer is formed in an island growth mode or a layer-island mixed mode, with an island structure, at a growth temperature of 600-1500 °C, a V / III ratio of 20-50000, and a pressure of 50-750 Torr. Then, the doping source SiH4 is turned off, TMAl and NH3 are introduced, N2 and H2 are introduced as carrier gases, and the unintentionally-doped AlN layer is grown in a layer growth mode, at a growth temperature of 600-1500 °C, a V / III ratio of 20-50000, and a pressure of 50-750 Torr. The number of growth cycles of the heavily-doped layer / unintentionally-doped layer is 1-1000, and preferably, the number of growth cycles is 5, 10, 20, 50, 100, 200, or 500.

[0061] The heavily-doped layer has an island structure, with a thickness of 1-5000 nm, and preferably, the thickness is 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, or 2000 nm. The doping element of the heavily-doped layer is Si, and the doping concentration is 5×1018-1×1021 cm-3, and preferably, the doping concentration is 8.5×1018 cm-3, 5.5×1018 cm-3, 8.5×1018 cm-3, 1.5×1019 cm-3, 5×1019 cm-3, 1×1020 cm-3, 5×1020 cm-3, or 1×1021 cm-3. 18 ~1×10 21 cm -3 , preferably 8.5×10 18 cm -3 , 5.5×10 19 cm -3 , 8.5×10 19 cm -3 , 1.5×10 20 cm -3, 2.5×10 20 cm -3 , 4.5×10 20 cm -3 , 7.5×10 20 cm -3 . The thickness of the unintentionally doped layer is 1 to 5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm.

[0062] Example 4

[0063] Referring Figure 4 as shown, Example 4 of the present invention discloses an AlGaN thin film, comprising:

[0064] a substrate, which is a sapphire substrate in this embodiment, and can also be other substrate materials such as Si, SiC, GaN, etc. in other embodiments;

[0065] a buffer layer located on the sapphire substrate, the thickness of the buffer layer is 1 to 5000 nm, and the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, AlN / GaN.

[0066] alternately deposited heavily doped Al x Ga 1-x N (0 < x < 1) layer / unintentionally doped Al y Ga 1-y N (0 < y < 1) layer, the number of cycles of alternately deposited heavily doped layers and unintentionally doped layers is 1 to 1000, preferably 5, 10, 20, 50, 100, 200, 500.

[0067] The heavily doped layer has an island structure, the thickness of the heavily doped layer is 1 to 5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm; the doping element of the heavily doped layer is Si, and the doping concentration is 5×10 18 ~1×10 21 cm -3 , preferably 8.5×10 18 cm -3 , 5.5×10 19 cm -3 , 8.5×10 19 cm -3 , 1.5×10 20 cm -3 , 2.5×10 20 cm -3 , 4.5×10 20 cm-3 7.5 x 10 20 cm -3 The thickness of the unintentionally doped layer is 1-5000 nm.

[0068] The values of x and y in the heavily doped layer and the unintentionally doped layer can be the same or different.

[0069] The specific preparation method is as follows:

[0070] A substrate is provided, which is selected from one of sapphire, Si, SiC, GaN, and in the embodiment, the substrate is a sapphire substrate. The substrate is cleaned and surface-nitrided, specifically, the substrate is placed in a metal organic chemical vapor deposition (MOCVD) device cavity, baked in an H2 atmosphere for 2-20 min at a temperature of 1000-1300℃, and then NH3 is introduced to perform surface nitriding of the substrate, and the nitriding time is 20-500 s.

[0071] A buffer layer is grown on the substrate, and the buffer layer is selected from GaN, AlN, AlGaN, AlGaN / GaN, and AlN / GaN, and the thickness of the buffer layer is 1-5000 nm. The growth temperature is 500-1500℃, the V / III ratio is 20-50000, the pressure is 50-750 Torr, and the carrier gas is selected from N2, H2, and N2 / H2 mixed gas.

[0072] The heavily doped Al x Ga 1-x N (0 < x < 1) layer and the unintentionally doped Al y Ga 1-y N (0 < y < 1) layer are alternately deposited on the buffer layer. In one growth cycle of the heavily doped Al x Ga 1-x N (0 < x < 1) layer / unintentionally doped Al y Ga 1-y N (0 < y < 1) layer, TMAl, TMG, and NH3 are first introduced, N2 and H2 are introduced as carrier gas, and SiH4 is introduced to provide the doping element Si, and island growth mode or layer-island hybrid mode is adopted to form the heavily doped Al x Ga 1-x N (0 < x < 1) layer with island structure, the growth temperature is 600-1500℃, the V / III ratio is 20-50000, and the pressure is 50-750 Torr; then, the doping source SiH4 is turned off, TMAl, TMG, and NH3 are introduced, N2 and H2 are introduced as carrier gas, and the unintentionally doped Al y Ga 1-yThe N (0 < y < 1) layer is grown at a temperature of 600-1500 DEG C, a V / III ratio of 20-50000, and a pressure of 50-750 Torr. The growth cycle number of the heavily doped layer / non-intentionally doped layer is 1-1000, preferably 5, 10, 20, 50, 100, 200, 500.

[0073] The heavily doped layer has an island structure, and the thickness of the heavily doped layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm. The doping element of the heavily doped layer is Si, and the doping concentration is 5*10 18 ~1*10 21 cm -3 , preferably 8.5*10 18 cm -3 , 5.5*10 19 cm -3 , 8.5*10 19 cm -3 , 1.5*10 20 cm -3 , 2.5*10 20 cm -3 , 4.5*10 20 cm -3 , 7.5*10 20 cm -3 . The thickness of the non-intentionally doped layer is 1-5000 nm, preferably 10 nm, 20 nm, 50 nm, 100 nm, 300 nm, 500 nm, 1000 nm, 2000 nm.

[0074] The nitride film (GaN, AlN, AlGaN) of the application has low dislocation density and good crystal quality, and can be widely applied in the fields of optoelectronic devices and electronic devices. The equipment used in the preparation method of the application includes but is not limited to a metal organic chemical vapor deposition system, a molecular beam epitaxy system and a vapor phase epitaxy system.

[0075] The above description is only used to illustrate the application, and does not limit the implementation method of the application in any form. Any modification or amendment to the application based on the shape, structure, feature and basic idea described in the application should be included in the scope of the intellectual property rights intended to be protected by the application.

Claims

1. A nitride thin film, characterized in that: The device includes a substrate, a buffer layer on the substrate, and alternating heavily doped nitride layers and unintentionally doped nitride layers deposited on the buffer layer. The number of periods of the alternating heavily doped nitride layers and unintentionally doped nitride layers is 5, 10, 20, 50, 100, 200, or 500. The heavily doped nitride layers have a rough surface structure, which has a 3D island-like growth structure. The unintentionally doped nitride layers have a flat surface structure, which has a 2D layered growth structure. The nitrides of the heavily doped nitride layer and the unintentionally doped nitride layer are both GaN or both AlN, or the nitride of the heavily doped nitride layer is Al x Ga 1-x N, where 0 < x < 1, and the nitride of the unintentionally doped nitride layer is Al y Ga 1-y N, where 0 < y < 1, and the values of x and y are the same or different; The nitride dopant element of the heavily doped nitride layer is Si, and the doping concentration is 5 × 10⁻⁶. 18 ~1×10 21 cm -3 .

2. The nitride thin film according to claim 1, characterized in that: The substrate includes any one of Si, SiC, GaN, and sapphire.

3. The nitride thin film according to claim 1, characterized in that: The thickness of the buffer layer is 1~5000nm, including any one of GaN, AlN, AlGaN, AlGaN / GaN, and AlN / GaN.

4. The nitride thin film according to claim 1, characterized in that: The thickness of the heavily doped nitride layer is 1~5000 nm, and the thickness of the unintentionally doped nitride layer is 1~5000 nm.

5. A method for preparing a nitride thin film as described in any one of claims 1 to 4, characterized in that: Includes the following steps: Step 1: Grow a buffer layer on the substrate at a growth temperature of 450~1500℃, a V / III ratio of 20~50000, and a pressure of 50~750 Torr. Step 2: Alternately deposit heavily doped nitride layers and unintentionally doped nitride layers on the buffer layer to obtain the nitride film; First, the epitaxial growth of the heavily doped nitride layer uses SiH4 or Si2H6 to provide the doping element Si, and N2 and H2 as carrier gases. The heavily doped nitride layer with an island structure is formed by island growth mode or layer-island hybrid mode. The growth temperature is 600~1500℃, the V / Ⅲ ratio is 20~50000, and the pressure is 50~750 Torr. Epitaxial growth of unintentionally doped nitride layers does not require dopants. The growth temperature is 600~1500℃, the V / III ratio is 20~50000, and the pressure is 50~750 Torr. An unintentionally doped nitride layer with a flat surface is formed by using a layered growth mode. Finally, the growth process of the heavily doped nitride layer and the unintentionally doped nitride layer is repeated to achieve a multi-cycle stacked structure.

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