A GaN thin film on an Si substrate and a preparation method thereof

Abstract

The present invention discloses a GaN thin film on an Si substrate and a preparation method thereof. The GaN thin film on the Si substrate includes: a base AlN layer grown on the Si substrate, a first AlGaN layer grown on the base AlN layer, an Si x N y layer grown on the Si x N y layer, a second AlGaN layer grown on the Si x N y layer, a low-temperature GaN layer grown on the second AlGaN layer, and a high-temperature GaN layer grown on the low-temperature GaN layer. In the embodiment of the present invention, an Si x N y layer is inserted into the buffer layer structure, which is beneficial to relieving the stress generated during the growth of the epitaxial layer, and this layer can effectively pin dislocations, and finally can effectively relieve the defect density in the thin film, thereby realizing the growth of a GaN thin film with high crystal quality; the present invention uses Si as a substrate, and the substrate is easy to obtain, which is beneficial to reducing the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to a GaN thin film on an Si substrate and a preparation method thereof. Background Art

[0002] As a new type of solid lighting source and green light source, light-emitting diodes (LEDs) have outstanding characteristics such as small size, low power consumption, environmental protection, long service life, high brightness, low heat, and multi-color, and are widely used in outdoor lighting, commercial lighting, and decoration projects. At present, under the background of the increasingly severe global warming problem, saving energy and reducing greenhouse gas emissions have become important issues faced by the world. Low-carbon economy based on low energy consumption, low pollution, and low emissions will become an important direction of economic development. In the lighting field, the application of LED lighting products is attracting the attention of the world. As a new type of green light source product, LED is bound to be the future development trend. However, at present, the application cost of LED is relatively high and the luminous efficiency is relatively low, which will greatly limit the development of LED towards high-efficiency energy-saving and environmental protection.

[0003] Group III nitride GaN has extremely excellent properties in electricity, optics, and acoustics, and has received extensive attention in recent years. GaN is a direct bandgap material, with fast acoustic wave transmission speed, good chemical and thermal stability, high thermal conductivity, low thermal expansion coefficient, and high breakdown dielectric strength, and is an ideal material for manufacturing high-efficiency semiconductor devices such as LED devices. At present, the luminous efficiency of GaN-based blue LEDs has now reached 28% and is still increasing further, which is much higher than the luminous efficiency of currently commonly used lighting methods such as incandescent lamps (about 2%) or fluorescent lamps (about 10%). In addition, deep ultraviolet LEDs have broad application prospects in the fields of national defense technology, information technology, biopharmaceuticals, environmental monitoring, public health, disinfection, etc.

[0004] For LEDs to truly achieve large-scale and wide application, it is necessary to further improve the luminous efficiency of LED chips and at the same time reduce the price of LED chips. Although the luminous efficiency of blue / white LEDs has exceeded that of fluorescent lamps and incandescent lamps, the luminous efficiency of commercial LEDs is still lower than that of sodium lamps (150 lm / W), and the price per lumen / watt is relatively high. For example, the development of AlGaN-based deep ultraviolet LEDs has made some progress, but performance problems such as low external quantum efficiency and low luminous power still hinder their commercialization. High-quality epitaxial materials are the basis for preparing high-performance GaN-based LEDs. At present, most GaN-based LEDs are epitaxially grown on sapphire and SiC substrates. The large-size sapphire and SiC substrates are expensive, resulting in high manufacturing costs of LEDs. Therefore, there is an urgent need to find a low-cost substrate material and a more effective buffer layer structure for epitaxial growth of high-quality GaN thin films. Summary of the invention

[0005] The present invention aims to provide a GaN film on a Si substrate and a preparation method thereof, aiming to solve the problem in the prior art that the growth cost of the GaN film is high and the performance needs to be improved.

[0006] The embodiment of the present invention provides a GaN film on a Si substrate, which comprises: a base AlN layer grown on a Si substrate, a first AlGaN layer grown on the base AlN layer, and a Si substrate on the first AlGaN layer. x N y layer, grown on the Si x N y a second AlGaN layer on the AlGaN layer, a low-temperature GaN layer grown on the second AlGaN layer, and a high-temperature GaN layer grown on the low-temperature GaN layer.

[0007] In one embodiment, the thickness of the base AlN layer is 100-500 nm.

[0008] In one embodiment, the thickness of the base AlN layer is 200-400 nm.

[0009] In one embodiment, the thickness of the first AlGaN layer is 100-500 nm.

[0010] In one embodiment, the thickness of the first AlGaN layer is 200-300 nm.

[0011] In one embodiment, the Si x N y The thickness of the layer is 2 to 10 nm.

[0012] In one embodiment, the thickness of the second AlGaN layer is 100-500 nm.

[0013] In one embodiment, the thickness of the low-temperature GaN layer is 100-500 nm.

[0014] In one embodiment, the high temperature GaN layer has a thickness of 1-3 μm.

[0015] The present invention also provides a method for preparing a GaN thin film on a Si substrate as described above, which comprises:

[0016] Select Si substrate;

[0017] growing a base AlN layer on the Si substrate;

[0018] growing a first AlGaN layer on the base AlN layer;

[0019] Grow Si on the first AlGaN layer x N y layer;

[0020] Grow a second AlGaN layer on the Si x N y layer;

[0021] Grow a low-temperature GaN layer on the second AlGaN layer;

[0022] Grow a high-temperature GaN layer on the low-temperature GaN layer.

[0023] An embodiment of the present invention provides a GaN thin film on a Si substrate and a preparation method. The GaN thin film on the Si substrate includes: a base AlN layer grown on the Si substrate, a first AlGaN layer grown on the base AlN layer, and Si x N y layer grown on the first AlGaN layer, a second AlGaN layer grown on the Si x N y layer, a low-temperature GaN layer grown on the second AlGaN layer, and a high-temperature GaN layer grown on the low-temperature GaN layer. In the buffer layer structure of the embodiment of the present invention, a Si x N y layer is inserted, which is beneficial to relieve the stress generated during the growth of the epitaxial layer, and this layer can effectively pin dislocations, and finally can effectively relieve the defect density in the thin film, so as to realize the growth of a GaN thin film with high crystal quality; the present invention uses Si as the substrate, and the substrate is easy to obtain, which is beneficial to reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of a GaN thin film on a Si substrate provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic flow chart of a preparation method of a GaN thin film on a Si substrate provided by an embodiment of the present invention;

[0027] Figure 3 It is an XRD pattern of a GaN thin film on a Si substrate prepared by an embodiment of the present invention;

[0028] Figure 4XRD pattern of the GaN thin film on the Si substrate prepared in another embodiment of the present invention. Detailed implementation manners

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0031] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0032] It should be further understood that the term " / and / " used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0033] An embodiment of the present invention provides a GaN thin film on a Si substrate, as Figure 1 shown, which includes: a base AlN layer 102 grown on a Si substrate 101, a first AlGaN layer 103 grown on the base AlN layer 102, a Si x N y layer 104 grown on the first AlGaN layer 103, a second AlGaN layer 105 grown on the Si x N y layer 104, a low-temperature GaN layer 106 grown on the second AlGaN layer 105, and a high-temperature GaN layer 107 grown on the low-temperature GaN layer 106.

[0034] In the embodiment of the present invention, Si x N yThe layer 104 is beneficial to relieve the stress generated during the growth of the epitaxial layer, and this layer can effectively pin dislocations, and finally can effectively relieve the defect density in the thin film, so as to realize the growth of high-crystalline-quality GaN thin film; in the present invention, Si is used as the substrate, and the substrate is easy to obtain, which is beneficial to reducing the production cost.

[0035] In one embodiment, the thickness of the base AlN layer 102 is 100 - 500 nm. More preferably, the thickness of the base AlN layer 102 is 200 - 400 nm, such as 300 nm. The base AlN layer 102 is to prevent the remelting and etching reaction between Ga and Si at high temperature when growing the subsequent Ga-component-containing material, resulting in the failure of subsequent growth.

[0036] In one embodiment, the thickness of the first AlGaN layer 103 is 100 - 500 nm. More preferably, the thickness of the first AlGaN layer 103 is 200 - 300 nm, such as 250 nm. The lattice parameter of the first AlGaN layer 103 is between that of AlN and GaN, and can play a role in reducing lattice mismatch and releasing stress. The first AlGaN layer 103 has a high Al content, and the component content of Al is ≥50%, that is, the first AlGaN layer 103 is Al x Ga 1-x N, where x≥0.5.

[0037] In one embodiment, the Si x N y layer 104 has a thickness of 2 - 10 nm. Preferably, the Si x N y layer 104 has a thickness of 4 - 6 nm, such as 5 nm. Since both the base AlN layer 102 and the first AlGaN layer 103 have a large defect density, directly growing GaN continuously will result in relatively poor crystal quality of the grown GaN. Therefore, it is necessary to insert a large-mismatch buffer layer Si x N y , to release the stress generated due to crystal mismatch. The Si x N y layer 104 is a large-mismatch buffer layer. Such a large-mismatch buffer layer is generally amorphous and usually has a large number of vacancy defects. Dislocations are easy to nucleate in this layer of material. At the same time, the vacancy defects can promote the slip of dislocations in the buffer layer and prevent dislocations from penetrating into the subsequent epitaxial layer. Therefore, this layer of large-mismatch buffer layer can play a role in stress release. The grown Si x N y layer 104 is an amorphous material, and any ratio may occur, so there is no fixed ratio for x and y.

[0038] In one embodiment, the thickness of the second AlGaN layer 105 is 100 - 500 nm, such as 250 nm. The second AlGaN layer 105 serves as a buffer layer to reduce lattice mismatch and release stress. The second AlGaN layer 105 has a low Al content, and the component content of Al is ≤10%, that is, the second AlGaN layer 105 is Al x Ga 1-x N, where x ≤ 0.1.

[0039] In one embodiment, the thickness of the low-temperature GaN layer 106 is 100 - 500 nm, such as 300 nm. The low-temperature GaN layer 106 is grown at a low temperature and contains a large number of dislocations and defects. This layer provides a bottom foundation for the growth of the subsequent high-crystal-quality high-temperature GaN layer 107.

[0040] In one embodiment, the thickness of the high-temperature GaN layer 107 is 1 - 3 μm, such as 2 μm.

[0041] The embodiment of the present invention also provides a method for preparing a GaN thin film on an Si substrate as described above, as Figure 2 shown, which includes steps S201 - S207:

[0042] S201. Select an Si substrate;

[0043] S202. Grow a base AlN layer on the Si substrate;

[0044] S203. Grow a first AlGaN layer on the base AlN layer;

[0045] S204. Grow an Si x N y layer on the first AlGaN layer;

[0046] S205. Grow a second AlGaN layer on the Si x N y layer;

[0047] S206. Grow a low-temperature GaN layer on the second AlGaN layer;

[0048] S207. Grow a high-temperature GaN layer on the low-temperature GaN layer.

[0049] Preferably, in the step of growing the base AlN layer, the base AlN layer is grown on the Si substrate by metalorganic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h;

[0050] Preferably, in the first AlGaN layer growth step, a first AlGaN layer is grown on the base AlN layer by metalorganic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h;

[0051] Preferably, in the Si x N y layer growth step, a Si x N y layer is grown on the first AlGaN layer by metalorganic chemical vapor deposition. The process conditions are as follows: silane is used as the Si source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h;

[0052] Preferably, in the second AlGaN layer growth step, a second AlGaN layer is grown on the Si x N y layer by metalorganic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h;

[0053] Preferably, in the low-temperature GaN layer growth step, a low-temperature GaN layer is grown on the second AlGaN layer by metalorganic chemical vapor deposition. The process conditions are as follows: trimethylgallium is used as the Ga source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 900 - 1000 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h;

[0054] Preferably, in the high-temperature GaN layer growth step, a high-temperature GaN layer is grown on the low-temperature GaN layer by metalorganic chemical vapor deposition. The process conditions are as follows: trimethylgallium is used as the Ga source, ammonia is used as the N source, hydrogen is used as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h.

[0055] The GaN thin film grown on the Si substrate prepared in the embodiment of the present invention is used to prepare an LED: Si-doped n-type GaN and In are epitaxially grown in sequence on the GaN thin film grown on the Si substrate prepared in this embodiment. x Ga 1-x N multiple quantum well layers, Mg-doped p-type GaN layer, and finally metal electrodes are electron beam evaporated and annealed to form ohmic contacts. For the GaN-based LED device prepared on the Si substrate, the thickness of the n-type GaN is about 1 μm, and the carrier concentration is 4×10 18 cm -3 ; The thickness of the In x Ga 1-x N / GaN multiple quantum well layer is about 130 nm, and the number of periods is 10. Among them, the In x Ga 1-x N well layer is 3 nm, the GaN barrier layer is 10 nm, the thickness of the p-type Mg-doped GaN layer is about 150 nm, and the carrier concentration is 3×10 17 cm -3 . At a working current of 20 mA, the light output power of the LED device is 4.02 mW, and the turn-on voltage value is 3 V. In another embodiment, at a working current of 20 mA, the light output power of the prepared LED device is 3.5 mW, and the turn-on voltage value is 3.1 V.

[0056] Figure 3 is the XRD pattern of the GaN thin film (0002 crystal plane) prepared in the embodiment of the present invention. Figure 4 is the XRD pattern of the GaN thin film (10-12 crystal plane) prepared in the embodiment of the present invention. It can be seen from the X-ray rocking curve that the full width at half maximum (FWHM) value of the X-ray rocking curve of GaN (0002) is lower than 230 arcsec, and the full width at half maximum value of GaN (10-12) is 250 arcsec; it indicates that high-quality GaN thin films have been epitaxially grown on the Si substrate.

[0057] In the embodiment of the present invention, amorphous Si x N y is inserted into the buffer layer structure as a large lattice mismatch buffer layer (i.e., Si x N ylayer), which is beneficial to relieve the stress generated during the growth of the epitaxial layer. Moreover, the amorphous buffer layer can effectively pin dislocations, and ultimately can effectively relieve the defect density in the thin film, thereby realizing the growth of GaN thin film with high crystal quality. The present invention can effectively reduce the formation of dislocations, prepare high-quality GaN thin films, which is beneficial to improving the radiative recombination efficiency of carriers and reducing the non-radiative recombination efficiency, and can greatly improve the performance of nitride semiconductor devices such as semiconductor lasers, photodetectors, light-emitting diodes and solar cells. The present invention uses Si as the substrate, which is easy to obtain and cheap, and is beneficial to reducing the production cost. The growth process of the present invention is unique and simple to implement, and has repeatability. The present invention can obtain an epitaxial layer thin film with high quality and smooth interface, and then prepare high-performance and high-light-emitting-efficiency GaN-based optoelectronic devices. This method is simple to implement, has remarkable effects and is inexpensive.

[0058] The various embodiments in the specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0059] It should also be noted that in this specification, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

Claims

1. A GaN thin film on an Si substrate, characterized in that, Including: A base AlN layer grown on a Si substrate, a first AlGaN layer grown on the base AlN layer, Si x N y layer, a second AlGaN layer grown on the Si x N y layer, a low-temperature GaN layer grown on the second AlGaN layer, and a high-temperature GaN layer grown on the low-temperature GaN layer; The thickness of the base AlN layer is 200 - 400 nm; The thickness of the first AlGaN layer is 250 nm; the first AlGaN layer is Al x Ga 1-x GaN, where x ≥ 0.5; The said Si x N y layer has a thickness of 5 nm; The thickness of the second AlGaN layer is 250 nm; the second AlGaN layer is Al x Ga 1-x GaN, where x ≤ 0.1; The thickness of the low-temperature GaN layer is 300 nm; The thickness of the high-temperature GaN layer is 2 μm.

2. A method for preparing a GaN thin film on an Si substrate as described in claim 1, characterized in that, Including: Select an Si substrate; Grow a base AlN layer on the Si substrate; Grow a first AlGaN layer on the base AlN layer; Si is grown on the first AlGaN layer x N y layer Grow a second AlGaN layer on the Si x N y layer; Grow a low-temperature GaN layer on the second AlGaN layer; Grow a high-temperature GaN layer on the low-temperature GaN layer.

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