Low-dislocation crack-free AlN film and epitaxial growth method thereof

Abstract

The invention discloses a low-dislocation crack-free AlN (aluminum nitride) thin film, which comprises an AlN nucleating layer, an AlN thin film layer, an AlN thin film layer and an AlN thin film layer, the high-temperature AlN layer is grown on the AlN nucleating layer; the low-temperature AlN layer is grown on the high-temperature AlN layer; a high temperature medium V / III ratio AlN layer grown over the low temperature AlN layer; and a high temperature low V / III ratio AlN layer grown over the high temperature medium V / III ratio AlN layer. According to the AlN thin film, the high-temperature medium V / III ratio AlN layer is inserted between the low-temperature AlN and the high-temperature low V / III ratio AlN to serve as a stress regulation and dislocation filtering layer. The high-temperature medium V / III ratio AlN layer can effectively reduce the tensile stress generated by thermal mismatch between the high-temperature AlN layer and the low-temperature AlN layer, so that the risk of film cracking is reduced, dislocation can be further filtered, and the low-dislocation crack-free AlN film is obtained. Epitaxial growth of a low-dislocation AlN thin film is the key to preparation of high-efficiency deep ultraviolet electronic devices, such as light-emitting diodes (LEDs), semiconductor lasers and high-frequency power devices.

Description

Technical Field

[0001] The invention relates to the technical field of new semiconductor materials, and in particular to a low-dislocation crack-free AlN film and an epitaxial growth method thereof. Background Art

[0002] Aluminum nitride (AlN), as the third generation wide bandgap semiconductor material, is a key material for preparing deep ultraviolet light-emitting diodes, semiconductor lasers, high-frequency power and other devices. Deep ultraviolet light-emitting diodes are widely used in sterilization and disinfection, protein analysis, medical diagnosis, drug discovery, endpoint detection, blood gas analysis, petrochemical analysis, gas detection, biological detection, ultraviolet curing, counterfeit currency identification, analytical instruments, ozone detection and other fields. UV-LED is in a period of rapid development, and its broad market prospects have become a new hot spot for global LED research and investment after semiconductor lighting LED.

[0003] Although deep ultraviolet LEDs are widely used, their performance limits their commercial application. At present, the quantum efficiency of deep ultraviolet LEDs is generally in the single digit, and the light extraction efficiency is only about 8%. One of the reasons is the lack of economical and affordable large AlN single crystal templates, so AlN films are grown on sapphire substrates as buffer layers for deep ultraviolet LEDs. However, due to the large lattice mismatch and thermal mismatch between sapphire and AlN films, the dislocation density of AlN films epitaxially grown on sapphire is very large and easy to crack, which seriously affects the luminous efficiency of deep ultraviolet LEDs and restricts the development and application of deep ultraviolet LEDs. Related studies have shown that the use of low-temperature AlN insertion layers can effectively reduce dislocation density. In our experiments, low-temperature AlN insertion layers can indeed significantly reduce dislocation density, but the AlN film is subjected to large tensile stress, resulting in severe cracking of the film. This is due to the large thermal adaptation between high-temperature AlN and low-temperature AlN. Cracked films obviously cannot be used as substrates for devices. While using a low-temperature AlN insertion layer to reduce dislocations, it is also necessary to reduce film stress and prevent AlN film cracking. A new epitaxial growth method needs to be proposed to solve the above existing problems.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a low dislocation crack-free AlN film and an epitaxial growth method thereof, so as to overcome the problem of film cracking caused by thermal mismatch in heteroepitaxial AlN film grown on a sapphire substrate using a high and low temperature AlN method.

[0006] To achieve the above object, the present invention provides a low-dislocation crack-free AlN film, comprising:

[0007] An AlN nucleation layer grown on top of a sapphire substrate;

[0008] a high temperature AlN layer grown on top of the AlN nucleation layer;

[0009] a low temperature AlN layer grown on top of the high temperature AlN layer;

[0010] a high temperature medium V / III ratio AlN layer grown on top of the low temperature AlN layer;

[0011] A high temperature low V / III ratio AlN layer is grown on the high temperature medium V / III ratio AlN layer.

[0012] Preferably, in the above technical solution, the thickness of the AlN nucleation layer is 10 nm to 30 nm.

[0013] Preferably, in the above technical solution, the high temperature AlN layer is a high temperature AlN layer grown by ammonia pulse flow, and has a thickness of 150nm to 300nm.

[0014] Preferably, in the above technical solution, the thickness of the low-temperature AlN layer is 150nm to 300nm.

[0015] Preferably, in the above technical solution, the thickness of the high temperature medium V / III ratio AlN layer is 200nm-2000nm.

[0016] Preferably, in the above technical solution, the high temperature and low V / III ratio AlN layer has a thickness of 1000nm-3000nm.

[0017] A method for epitaxial growth of the above-mentioned low-dislocation crack-free AlN film comprises the following steps:

[0018] (1) Cleaning the sapphire substrate, then placing it in an MOCVD reaction chamber, and introducing ammonia gas to nitride the surface of the sapphire substrate;

[0019] (2) growing an AlN nucleation layer on a nitrided sapphire substrate;

[0020] (3) growing a high temperature AlN layer on the AlN nucleation layer;

[0021] (4) growing a low-temperature AlN layer on the high-temperature AlN layer;

[0022] (5) growing a high temperature medium V / III ratio AlN layer on a low temperature AlN layer;

[0023] (6) Growing a high temperature, low V / III ratio AlN layer on a high temperature, medium V / III ratio AlN layer.

[0024] Preferably, in the above technical solution, the nitridation temperature of the sapphire surface in step (1) is 1000-1200° C., and the nitridation time is 2-10 min;

[0025] Preferably, in the above technical solution, step (2) grows the AlN nucleation layer at a temperature of 600 to 900° C.;

[0026] Preferably, in the above technical solution, step (3) grows the high temperature AlN layer at a temperature of 1050-1200° C. and a V / III ratio of 1000-4000, wherein the Al source is continuously introduced and ammonia is intermittently introduced;

[0027] Preferably, in the above technical solution, step (4) grows the low-temperature AlN layer at a temperature of 920-980° C. and a V / III ratio of 1000-4000;

[0028] Preferably, in the above technical solution, step (5) grows the high temperature medium V / III ratio AlN layer at a temperature of 1200-1300° C. and a V / III ratio of 300-700;

[0029] Preferably, in the above technical solution, step (6) grows the high temperature and low V / III ratio AlN layer at a temperature of 1200-1300° C. and a V / III ratio of 60-300.

[0030] Preferably, in the above technical solution, in step (3), ammonia is intermittently introduced with an on-off time of 3-15s / 2-6s.

[0031] Preferably, in the above technical solution, in step (3), ammonia is intermittently introduced with an on / off time of 12s / 6s.

[0032] Compared with the prior art, the present invention has the following beneficial effects: the low dislocation and crack-free AlN film prepared by the epitaxial growth method of the present invention has a high temperature medium V / III ratio AlN layer inserted between the low temperature AlN and the high temperature low V / III ratio AlN as a stress regulation and dislocation filtering layer. The high temperature medium V / III ratio AlN layer can effectively reduce the tensile stress generated by the thermal mismatch between the high and low temperature AlN layers, thereby reducing the risk of film cracking, and can further filter dislocations to obtain a low dislocation and crack-free AlN film. The AlN film is used as a substrate for deep ultraviolet LED devices, photodetectors, and AlN-based high electron mobility transistors. The crack-free and low dislocation AlN substrate of the present invention can greatly enhance the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of a low-dislocation crack-free AlN film according to the present invention;

[0034] Figure 2 is a Raman spectrum of a low-dislocation, crack-free AlN film according to Example 1 of the present invention;

[0035] Figure 3 This is a test graph of the XRD (002) and (102) plane rocking curves of the low dislocation and crack-free AlN film according to Example 1 of the present invention.

[0036] Figure 4 This is a cross-sectional TEM image of the low-dislocation, crack-free AlN film according to Example 1 of the present invention (below the [11-20] crystal zone axis).

[0037] Description of main reference numerals:

[0038] 1-sapphire substrate, 2-AlN nucleation layer, 3-high temperature AlN layer, 4-low temperature AlN layer, 5-high temperature medium V / III ratio AlN layer, 6-high temperature low V / III ratio AlN layer. DETAILED DESCRIPTION

[0039] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0040] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0041] Example 1

[0042] like Figure 1 As shown, according to a specific embodiment of the present invention, a method for epitaxial growth of the above-mentioned low-dislocation crack-free AlN film comprises the following steps:

[0043] (1) Cleaning the sapphire substrate, and then placing it in a MOCVD reaction chamber, introducing ammonia gas to nitride the surface of the sapphire substrate; the nitridation temperature of the sapphire surface is 1050° C., and the nitridation time is 2 min.

[0044] (2) Grow an AlN nucleation layer on a nitrided sapphire substrate. The AlN nucleation layer grows at a temperature of 750°C and has a thickness of 20 nm.

[0045] (3) Growing a high-temperature AlN layer on the AlN nucleation layer. The high-temperature AlN layer is grown at a temperature of 1170°C and a V / III ratio of 3200, wherein the Al source is continuously introduced and the ammonia is intermittently introduced, and the ammonia on-off time is 12s / 6s.

[0046] (4) Growing a low-temperature AlN layer on the high-temperature AlN layer. The low-temperature AlN layer is grown at a temperature of 950°C and a V / III ratio of 3200.

[0047] (5) Growing a high temperature medium V / III ratio AlN layer on the low temperature AlN layer. The high temperature medium V / III ratio AlN layer is grown at a temperature of 1300°C and a V / III ratio of 570.

[0048] (6) Growing a high temperature low V / III ratio AlN layer on a high temperature medium V / III ratio AlN layer. The high temperature low V / III ratio AlN layer is grown at a temperature of 1300°C and a V / III ratio of 160.

[0049] The low dislocation crack-free AlN film prepared according to the above method includes: a sapphire substrate 1; an AlN nucleation layer 2; which is grown on the sapphire substrate 1, and the thickness of the AlN nucleation layer is 20nm. A high-temperature AlN layer 3 is grown on the nucleation layer 2, and is an AlN layer grown by ammonia pulse flow, and the thickness of the high-temperature AlN layer is 200nm. A low-temperature AlN layer 4 is grown on the high-temperature AlN layer 3, and the thickness of the low-temperature AlN layer is 200nm. A high-temperature medium V / III ratio AlN layer 5 is grown on the low-temperature AlN layer 4, and the thickness of the high-temperature medium V / III ratio AlN layer is 600nm. A high-temperature low V / III ratio AlN layer 6 is grown on the high-temperature medium V / III ratio AlN layer 5, and the thickness of the high-temperature low V / III ratio AlN layer is 2000nm.

[0050] The low dislocation crack-free AlN film prepared in Example 1 was tested, and the test results are as follows:

[0051] See also Figure 2 This is the Raman spectrum of AlN film. There is no high-temperature medium V / III ratio AlN layer. That is, the high-temperature low V / III ratio AlN layer is grown directly on the low-temperature AlN layer. The E2high Raman peak of AlN film is located at 655.6cm -1 , indicating that the AlN film without high temperature medium V / III ratio insertion layer is subjected to relatively large tensile stress (the Raman peak of stress-free AlN film is 657.4 cm -1 ), while the AlN E2 high Raman peak of the high temperature medium V / III ratio AlN layer is located at 657.5 cm -1, indicating that the insertion layer with a high temperature medium V / III ratio can significantly reduce the tensile stress of the AlN film. At the same time, the AlN film is subjected to a slight compressive stress, which can effectively prevent the film from cracking.

[0052] See also Figure 3 It is the rocking curve test of XRD (002) and (102) planes of AlN film. The half-width value can reflect the dislocation density of the film. The smaller the value, the lower the dislocation density of the film. Due to the insertion of high temperature medium V / III ratio AlN layer, the half-width of the (102) rocking curve is reduced from 298 arcsec to 210 arcsec.

[0053] See also Figure 4 This is the cross-sectional TEM of the AlN film (below the [11-20] crystal zone axis). It can be clearly seen that the high-temperature medium V / III ratio AlN layer can effectively hinder the growth of dislocations toward the surface of the AlN film. Therefore, the insertion of the high-temperature medium V / III ratio AlN layer can further reduce the dislocation density of the AlN film.

[0054] Example 2

[0055] A method for epitaxial growth of the above-mentioned low-dislocation crack-free AlN film comprises the following steps:

[0056] (1) Cleaning the sapphire substrate, and then placing it in an MOCVD reaction chamber, introducing ammonia gas to nitride the surface of the sapphire substrate; the nitridation temperature of the sapphire surface is 1200° C., and the nitridation time is 10 min.

[0057] (2) Grow an AlN nucleation layer on a nitrided sapphire substrate. The AlN nucleation layer grows at a temperature of 900°C and has a thickness of 30 nm.

[0058] (3) Growing a high temperature AlN layer on the AlN nucleation layer. The high temperature AlN layer is grown at a temperature of 1200°C and a V / III ratio of 1000, wherein the Al source is continuously introduced and the ammonia is intermittently introduced, and the ammonia on-off time is 10s / 5s.

[0059] (4) Growing a low-temperature AlN layer on the high-temperature AlN layer. The low-temperature AlN layer is grown at a temperature of 980°C and a V / III ratio of 1000.

[0060] (5) Growing a high temperature medium V / III ratio AlN layer on the low temperature AlN layer. The high temperature medium V / III ratio AlN layer is grown at a temperature of 1300°C and a V / III ratio of 300.

[0061] (6) Growth of a high temperature, low V / III ratio AlN layer on a high temperature, medium V / III ratio AlN layer. The high temperature, low V / III ratio AlN layer is grown at a temperature of 1300°C and a V / III ratio of 60.

[0062] The low dislocation crack-free AlN film prepared according to the above method includes: a sapphire substrate 1; an AlN nucleation layer 2; which is grown on the sapphire substrate 1, and the thickness of the AlN nucleation layer is 30nm. The high-temperature AlN layer 3 is grown on the nucleation layer 2, and is an AlN layer grown by ammonia pulse flow, and the thickness of the high-temperature AlN layer is 300nm. The low-temperature AlN layer 4 is grown on the high-temperature AlN layer 3, and the thickness of the low-temperature AlN layer is 150nm. The high-temperature medium V / III ratio AlN layer 5 is grown on the low-temperature AlN layer 4, and the thickness of the high-temperature medium V / III ratio AlN layer is 2000nm. The high-temperature low V / III ratio AlN layer 6 is grown on the high-temperature medium V / III ratio AlN layer 5, and the thickness of the high-temperature low V / III ratio AlN layer is 1000nm.

[0063] Example 3

[0064] A method for epitaxial growth of the above-mentioned low-dislocation crack-free AlN film comprises the following steps:

[0065] (1) Cleaning the sapphire substrate, and then placing it in a MOCVD reaction chamber, introducing ammonia gas to nitride the surface of the sapphire substrate; the nitridation temperature of the sapphire surface is 1000° C., and the nitridation time is 2 min.

[0066] (2) Grow an AlN nucleation layer on a nitrided sapphire substrate. The AlN nucleation layer grows at a temperature of 600°C and has a thickness of 10 nm.

[0067] (3) Growing a high-temperature AlN layer on the AlN nucleation layer. The high-temperature AlN layer is grown at a temperature of 1050°C and a V / III ratio of 4000, wherein the Al source is continuously introduced and the ammonia is intermittently introduced, and the ammonia on-off time is 12s / 6s.

[0068] (4) A low temperature AlN layer is grown on the high temperature AlN layer. The low temperature AlN layer is grown at a temperature of 920°C and a V / III ratio of 4000.

[0069] (5) Growing a high temperature medium V / III ratio AlN layer on the low temperature AlN layer. The high temperature medium V / III ratio AlN layer is grown at a temperature of 1200°C and a V / III ratio of 700.

[0070] (6) Growing a high temperature low V / III ratio AlN layer on a high temperature medium V / III ratio AlN layer. The high temperature low V / III ratio AlN layer is grown at a temperature of 1200°C and a V / III ratio of 300.

[0071] The low dislocation crack-free AlN film prepared according to the above method includes: a sapphire substrate 1; an AlN nucleation layer 2; which is grown on the sapphire substrate 1, and the thickness of the AlN nucleation layer is 10nm. The high-temperature AlN layer 3 is grown on the nucleation layer 2, and is an AlN layer grown by ammonia pulse flow, and the thickness of the high-temperature AlN layer is 150nm. The low-temperature AlN layer 4 is grown on the high-temperature AlN layer 3, and the thickness of the low-temperature AlN layer is 300nm. The high-temperature medium V / III ratio AlN layer 5 is grown on the low-temperature AlN layer 4, and the thickness of the high-temperature medium V / III ratio AlN layer is 200nm. The high-temperature low V / III ratio AlN layer 6 is grown on the high-temperature medium V / III ratio AlN layer 5, and the thickness of the high-temperature low V / III ratio AlN layer is 3000nm.

[0072] Example 4

[0073] A method for epitaxial growth of the above-mentioned low-dislocation crack-free AlN film comprises the following steps:

[0074] (1) Cleaning the sapphire substrate, and then placing it in a MOCVD reaction chamber, introducing ammonia gas to nitride the surface of the sapphire substrate; the nitridation temperature of the sapphire surface is 1050° C., and the nitridation time is 8 minutes.

[0075] (2) Grow an AlN nucleation layer on a nitrided sapphire substrate. The AlN nucleation layer grows at a temperature of 650°C and has a thickness of 15 nm.

[0076] (3) Growing a high-temperature AlN layer on the AlN nucleation layer. The high-temperature AlN layer is grown at a temperature of 1100°C and a V / III ratio of 2000, wherein the Al source is continuously introduced and ammonia is introduced intermittently, and the ammonia on-off time is 15s / 5s.

[0077] (4) Growing a low-temperature AlN layer on the high-temperature AlN layer. The low-temperature AlN layer is grown at a temperature of 930°C and a V / III ratio of 2500.

[0078] (5) A high temperature medium V / III ratio AlN layer is grown on the low temperature AlN layer. The high temperature medium V / III ratio AlN layer is grown at a temperature of 1280°C and a V / III ratio of 450.

[0079] (6) Growing a high temperature low V / III ratio AlN layer on a high temperature medium V / III ratio AlN layer. The high temperature low V / III ratio AlN layer is grown at a temperature of 1280°C and a V / III ratio of 230.

[0080] The low dislocation crack-free AlN film prepared according to the above method includes: a sapphire substrate 1; an AlN nucleation layer 2; which is grown on the sapphire substrate 1, and the thickness of the AlN nucleation layer is 15nm. The high-temperature AlN layer 3 is grown on the nucleation layer 2, and is an AlN layer grown by ammonia pulse flow, and the thickness of the high-temperature AlN layer is 180nm. The low-temperature AlN layer 4 is grown on the high-temperature AlN layer 3, and the thickness of the low-temperature AlN layer is 200nm. The high-temperature medium V / III ratio AlN layer 5 is grown on the low-temperature AlN layer 4, and the thickness of the high-temperature medium V / III ratio AlN layer is 800nm. The high-temperature low V / III ratio AlN layer 6 is grown on the high-temperature medium V / III ratio AlN layer 5, and the thickness of the high-temperature low V / III ratio AlN layer is 2000nm.

[0081] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A low dislocation crack-free AlN film, characterized in that: include: An AlN nucleation layer grown on top of a sapphire substrate; a high temperature AlN layer grown on top of the AlN nucleation layer; a low temperature AlN layer grown on top of the high temperature AlN layer; a high temperature medium V / III ratio AlN layer grown on top of the low temperature AlN layer; A high temperature low V / III ratio AlN layer is grown on the high temperature medium V / III ratio AlN layer.

2. The low dislocation crack-free AlN film according to claim 1, characterized in that: The thickness of the AlN nucleation layer is 10 nm to 30 nm.

3. The low dislocation crack-free AlN film according to claim 1, characterized in that: The high temperature AlN layer is a high temperature AlN layer grown by ammonia pulse flow, and has a thickness of 150nm to 300nm.

4. The low dislocation crack-free AlN film according to claim 1, characterized in that: The thickness of the low-temperature AlN layer is 150nm-300nm.

5. The low dislocation crack-free AlN film according to claim 1, characterized in that: The high temperature medium V / III ratio AlN layer has a thickness of 200nm-2000nm.

6. The low dislocation crack-free AlN film according to claim 1, characterized in that: The thickness of the high temperature low V / III ratio AlN layer is 1000nm-3000nm.

7. A method for epitaxial growth of a low dislocation crack-free AlN film as claimed in claim 1, characterized in that: The following steps are involved: (1) Cleaning the sapphire substrate, then placing it in an MOCVD reaction chamber, and introducing ammonia gas to nitride the surface of the sapphire substrate; (2) growing an AlN nucleation layer on a nitrided sapphire substrate; (3) growing a high temperature AlN layer on the AlN nucleation layer; (4) growing a low-temperature AlN layer on the high-temperature AlN layer; (5) growing a high temperature medium V / III ratio AlN layer on a low temperature AlN layer; (6) Growing a high temperature, low V / III ratio AlN layer on a high temperature, medium V / III ratio AlN layer.

8. The epitaxial growth method of low dislocation crack-free AlN thin film according to claim 7, characterized in that: Step (1) The sapphire surface is nitrided at a temperature of 1000 to 1200° C. for 2 to 10 minutes; and / or step (2) growing the AlN nucleation layer at a temperature of 600 to 900° C.; and / or step (3) growing the high temperature AlN layer at a temperature of 1050-1200° C. and a V / III ratio of 1000-4000, wherein the Al source is continuously introduced and the ammonia is intermittently introduced; and / or step (4) growing the low temperature AlN layer at a temperature of 920-980° C. and a V / III ratio of 1000-4000; and / or step (5) growing the high temperature medium V / III ratio AlN layer at a temperature of 1200-1300° C. and a V / III ratio of 300-700; And / or step (6) grows the high temperature and low V / III ratio AlN layer at a temperature of 1200-1300° C. and a V / III ratio of 60-300.

9. The epitaxial growth method of low dislocation crack-free AlN thin film according to claim 8, characterized in that: In step (3), ammonia gas is intermittently introduced with an on-off time of 3-15s / 2-6s.

10. The epitaxial growth method of low dislocation crack-free AlN thin film according to claim 9, characterized in that: In step (3), ammonia gas is intermittently introduced with an on / off time of 12s / 6s.

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