CN112687779A - AlGaN film structure of Si substrate and preparation method thereof - Google Patents

Abstract

The invention discloses an AlGaN film structure of a Si substrate and a preparation method thereof, wherein the AlGaN film structure of the Si substrate comprises: the high-temperature AlGaN light-emitting diode comprises a basic AlN layer grown on a Si substrate, a first high-temperature AlN layer grown on the basic AlN layer, a low-temperature AlN layer grown on the first high-temperature AlN layer, a second high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the second high-temperature AlN layer and a second AlGaN layer grown on the first AlGaN layer, wherein the thickness of the second AlGaN layer is larger than that of the first AlGaN layer. According to the invention, the AlN buffer layer is prepared on the Si substrate, and the technology of combining the low temperature with the high temperature AlN buffer layer is adopted, so that the reduction of the meltback etching reaction between Si and Ga at high temperature can be effectively avoided, the defects of the prior art are overcome, and the high-performance AlGaN film is obtained.

Description

AlGaN film structure of Si substrate and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to an AlGaN film structure of a Si substrate and a preparation method thereof.

Background

The deep ultraviolet light has wide application prospect in the fields of national defense technology, information technology, bio-pharmaceuticals, environmental monitoring, public health, sterilization, disinfection and the like. The traditional ultraviolet light sources used at present are gas lasers and mercury lamps, and have the defects of large volume, high energy consumption, pollution and the like. An AlGaN-based compound semiconductor ultraviolet Light Emitting Diode (LED) is a solid ultraviolet light source and has the advantages of small volume, high efficiency, long service life, environmental friendliness, low energy consumption, no pollution and the like. The AlGaN material with high Al component is an irreplaceable material system for preparing high-performance deep ultraviolet LEDs, has great requirements in civil and military aspects, such as the medical and health fields of sterilization, cancer detection, skin disease treatment and the like, and has the advantages of no mercury pollution, adjustable wavelength, small volume, good integration, low energy consumption, long service life and the like.

In recent years, the development of AlGaN-based deep ultraviolet LEDs has made some progress, but the commercialization of AlGaN-based deep ultraviolet LEDs is still hindered by performance problems such as low external quantum efficiency and low light emitting power, and high-quality epitaxial materials are the basis for preparing high-performance deep ultraviolet LEDs. Currently, high-quality AlGaN materials are generally manufactured by a heteroepitaxy method, a Si substrate is also adopted as an epitaxial substrate of the AlGaN-based deep ultraviolet LED, but a larger lattice mismatch exists between the Si substrate and the epitaxially grown AlGaN material. Therefore, in order to realize the growth of high-quality AlGaN materials and high-performance deep ultraviolet LED epitaxial wafers on Si substrates, it is still necessary to overcome the major defects such as lattice mismatch, crystal dislocation, and stacking fault.

Disclosure of Invention

The invention aims to provide an AlGaN film structure of a Si substrate and a preparation method thereof, and aims to solve the problem that the performance of the AlGaN film structure in the prior art needs to be improved.

The embodiment of the invention provides an AlGaN film structure of a Si substrate, which comprises: the high-temperature AlGaN light-emitting diode comprises a basic AlN layer grown on a Si substrate, a first high-temperature AlN layer grown on the basic AlN layer, a low-temperature AlN layer grown on the first high-temperature AlN layer, a second high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the second high-temperature AlN layer and a second AlGaN layer grown on the first AlGaN layer, wherein the thickness of the second AlGaN layer is larger than that of the first AlGaN layer.

Preferably, the thickness of the basic AlN layer is 10 to 200 nm.

Preferably, the thickness of the first high-temperature AlN layer is 200 to 500 nm.

Preferably, the thickness of the first high-temperature AlN layer is 300to 400 nm.

Preferably, the thickness of the low-temperature AlN layer is 200-500 nm.

Preferably, the thickness of the low-temperature AlN layer is 300-400 nm.

Preferably, the thickness of the second high-temperature AlN layer is 500-800 nm.

Preferably, the thickness of the first AlGaN layer is 100 to 300 nm.

Preferably, the thickness of the second AlGaN layer is 800-2000 nm.

The embodiment of the invention also provides a preparation method of the AlGaN thin film structure of the Si substrate, which comprises the following steps:

selecting a Si substrate;

growing a basic AlN layer on the Si substrate;

growing a first high-temperature AlN layer on the base AlN layer;

growing a low-temperature AlN layer on the first high-temperature AlN layer;

growing a second high-temperature AlN layer on the low-temperature AlN layer;

growing a first AlGaN layer on the second high-temperature AlN layer;

growing a second AlGaN layer on the first AlGaN layer.

The embodiment of the invention provides an AlGaN film structure of a Si substrate and a preparation method thereof, wherein the AlGaN film structure of the Si substrate comprises the following components: the high-temperature AlGaN light-emitting diode comprises a basic AlN layer grown on a Si substrate, a first high-temperature AlN layer grown on the basic AlN layer, a low-temperature AlN layer grown on the first high-temperature AlN layer, a second high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the second high-temperature AlN layer and a second AlGaN layer grown on the first AlGaN layer, wherein the thickness of the second AlGaN layer is larger than that of the first AlGaN layer. According to the invention, the basic AlN layer is prepared on the Si substrate, and the technology of combining the low temperature with the high temperature AlN buffer layer is adopted, so that the reduction of the meltback etching reaction between Si and Ga at high temperature can be effectively avoided, the defects of the prior art are overcome, and the high-performance AlGaN film is obtained.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an AlGaN thin film structure of a Si substrate according to an embodiment of the present invention;

fig. 2 is a schematic flow chart illustrating a method for manufacturing an AlGaN thin film structure on a Si substrate according to an embodiment of the present invention;

FIG. 3 is an XRD pattern of an AlGaN thin film structure of a Si substrate prepared according to an embodiment of the present invention;

fig. 4 is another XRD pattern of the AlGaN thin film structure of the Si substrate prepared in the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

An embodiment of the present invention provides an AlGaN thin film structure of a Si substrate, as shown in fig. 1, which includes: a base AlN layer 102 grown on a Si substrate 101, a first high-temperature AlN layer 103 grown on the base AlN layer 102, a low-temperature AlN layer 104 grown on the first high-temperature AlN layer 103, a second high-temperature AlN layer 105 grown on the low-temperature AlN layer 104, a first AlGaN layer 106 grown on the second high-temperature AlN layer 105, and a second AlGaN layer 107 grown on the first AlGaN layer 106, wherein the thickness of the second AlGaN layer 107 is larger than the thickness of the first AlGaN layer 106.

The AlGaN film structure in the embodiment of the invention is a high Al component AlGaN film (the Al component is 0.8-1, wherein the component means the proportion of Al to Al and Ga, if Al is 0.8, Ga is 0.2, and the AlGaN film is Al_0.8Ga_0.2N thin film), in other words, the AlGaN thin film structure is Al_xGa_1-xN (x is more than or equal to 0.8 and less than 1). Because the Ga and the Si are subjected to a melt-back etching reaction under a high-temperature condition, the Ga-containing semiconductor material cannot be directly obtained by epitaxial growth on a Si substrate under the high-temperature condition, and epitaxial growth failure is caused. AlN or GaN single crystal substrate materials with lattice parameters similar to those of AlGaN are expensive and are not suitable for large-scale commercial production. In order to effectively use a Si substrate to carry out epitaxial growth of AlGaN materials at low cost, the AlN buffer layer (namely the basic AlN layer 102) is prepared on the Si substrate, and the technology of combining the low temperature and the high temperature AlN buffer layer is adopted, so that the reduction of the meltback etching reaction between Si and Ga at high temperature can be effectively avoided, the defects of the prior art are overcome, and the high-performance AlGaN film is obtained. The invention is inThe growth of AlGaN with high Al component on the Si substrate is equivalent to the doping of a small amount of Ga in the AlN material.

Preferably, the thickness of the basic AlN layer 102 is 10 to 200nm, such as 100 nm. The base AlN layer 102 provides a low-cost, higher crystal quality nitride template for subsequent epitaxial growth.

Preferably, the first high-temperature AlN layer 103 (high-temperature AlN buffer layer) has a thickness of 200 to 500 nm. Preferably, the thickness of the first high-temperature AlN layer 103 is 300to 400nm, such as 350 nm. The first high-temperature AlN layer 103 is grown under high-temperature conditions in order to further improve the crystal quality of the AlN material.

Preferably, the thickness of the low-temperature AlN layer 104 (low-temperature AlN buffer layer) is 200 to 500 nm. Preferably, the low-temperature AlN layer 104 has a thickness of 300to 400nm, such as 350 nm.

Preferably, the thickness of the second high-temperature AlN layer 105 (high-temperature AlN buffer layer) is 500 to 800 nm. Preferably, the second high-temperature AlN layer 105 has a thickness of 600 to 700nm, such as 650 nm. Because lattice mismatch exists between AlN and Si and mismatch stress exists, the quality of AlN material crystals grown by the structures of the basic AlN layer 102 and the first high-temperature AlN layer 103 is not good enough, a low-temperature and high-temperature growth process needs to be repeated once, the low-temperature AlN layer 104 serves as a nucleation layer, and the second high-temperature AlN layer 105 continues to grow at high temperature, so that the quality of AlN crystals is further improved.

Preferably, the thickness of the first AlGaN layer 106 is 100 to 300nm, such as 250 nm. Preferably, the thickness of the second AlGaN layer 107 is 800 to 2000nm, such as 1600 nm.

According to the invention, the AlGaN material with high Al component grows on the Si substrate, which is equivalent to doping a small amount of Ga in AlN, so that the lattice mismatch degree between AlGaN and AlN is small, and on a template of high-quality AlN, a first AlGaN layer 106 (nucleation layer) with high Al component grows at low temperature, and then a second AlGaN layer 107 grows at high temperature.

An embodiment of the present invention further provides a method for preparing the AlGaN thin film structure on the Si substrate, as shown in fig. 2, which includes steps S201 to S207:

s201, selecting a Si substrate;

s202, growing a basic AlN layer on the Si substrate;

s203, growing a first high-temperature AlN layer on the basic AlN layer;

s204, growing a low-temperature AlN layer on the first high-temperature AlN layer;

s205, growing a second high-temperature AlN layer on the low-temperature AlN layer;

s206, growing a first AlGaN layer on the second high-temperature AlN layer;

and S207, growing a second AlGaN layer on the first AlGaN layer.

Preferably, in the basic AlN layer growing step, a magnetron sputtering method is adopted, high-metal aluminum with the purity of 99.9999% is used as a target material, reaction gas (10-50 sccm helium, 50-300 sccm nitrogen and 1-5 sccm oxygen) is introduced, the substrate temperature is 600-800 ℃, and the growth rate is 1-2 mu m/h;

preferably, in the first high-temperature AlN layer growing step, a metal organic chemical vapor deposition method is used to grow a first high-temperature AlN layer on the base AlN layer, under the process conditions: trimethylaluminum is used as an Al source, ammonia is used as an N source, hydrogen is used as a carrier gas, the pressure of a reaction chamber is 50-300 torr, the temperature of a substrate is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 1-2 mu m/h;

preferably, in the low-temperature AlN layer growing step, a metal organic chemical vapor deposition method is used to grow a low-temperature AlN layer on the first high-temperature AlN layer, and the process conditions are: trimethylaluminum is used as an Al source, ammonia gas is used as an N source, hydrogen is used as a carrier gas, the pressure of a reaction chamber is 50-300 torr, the temperature of a substrate is 800-1000 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 1-2 μm/h;

preferably, in the second high-temperature AlN layer growing step, a metal organic chemical vapor deposition method is used to grow a second high-temperature AlN layer on the low-temperature AlN layer, and the process conditions are: trimethylaluminum is used as an Al source, ammonia is used as an N source, hydrogen is used as a carrier gas, the pressure of a reaction chamber is 50-300 torr, the temperature of a substrate is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 1-2 mu m/h;

preferably, in the step of growing the first AlGaN layer, a metal organic chemical vapor deposition method is adopted to grow the first AlGaN layer on the second high temperature AlN layer, and the process conditions are as follows: trimethylaluminum is used as an Al source, trimethylgallium is used as a Ga source, ammonia is used as an N source, hydrogen is used as a carrier gas, the pressure of a reaction chamber is 50-300 torr, the temperature of a substrate is 900-1100 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 1-2 μm/h;

preferably, in the second AlGaN layer growth step, a metal organic chemical vapor deposition method is adopted to grow a second AlGaN layer on the first AlGaN layer, and the process conditions are as follows: trimethyl gallium is used as a Ga source, ammonia gas is used as an N source, hydrogen is used as a carrier gas, the pressure of a reaction chamber is 50-300 torr, the temperature of a substrate is 1100-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 1-2 mu m/h.

The AlGaN thin film structure grown on the Si substrate prepared by the embodiment of the invention is used for preparing an ultraviolet LED: si-doped n-type AlGaN and Al are epitaxially grown in sequence on the AlGaN thin film structure grown on the Si substrate prepared in the embodiment_xGa_1-xAnd finally, electron beam evaporation is performed to form ohmic contact. The AlGaN-based ultraviolet LED device prepared on the Si substrate has the thickness of n-type AlGaN of about 1 mu m and the concentration of current carriers of 4 multiplied by 10¹⁸cm^-3；Al_xGa_1-xN/Al_yGa_1-yThe thickness of the N multi-quantum well layer is about 160nm, the period number is 10, wherein the Al layer is single-layer_xGa_1-xThe N well layer is 3nm in thickness and is a single layer of Al_yGa_1-yThe thickness of the N barrier layer is 13nm, the thickness of the p-type magnesium-doped AlGaN layer is about 150nm, and the concentration of the current carrier is 3 multiplied by 10¹⁷cm^-3. Under the working current of 20mA, the light output power of the LED device is 3.3mW, and the turn-on voltage value is 4.18V. In another embodiment of the AlGaN thin film structure, the light output power of the LED device is 3.5mW and the turn-on voltage is 4.4V at an operating current of 20 mA.

FIG. 3 shows Al prepared in this example_0.9Ga_0.1XRD pattern of N thin film structure (crystal face index 0002), FIG. 4 is another Al prepared in this example_0.9Ga_0.1N filmXRD pattern of structure (crystal face index 10-12) and Al can be seen from X-ray backswing curve_0.9Ga_0.1The value of the full width at half maximum (FWHM) of the X-ray rocking curve of N (0002, crystal face index) is lower than 250arcsec, Al_0.9Ga_0.1The half-peak width value of an X-ray swinging back curve of N (10-12, crystal face index) is 390 arcsec; the high-quality AlGaN film structure is shown to be epitaxially grown on the Si substrate.

According to the invention, firstly, a magnetron sputtering technology is adopted to prepare an AlN buffer layer (namely a basic AlN layer) on a Si substrate, and then a low-temperature and high-temperature AlN buffer layer combined technology is adopted, so that the stress generated in the growth process of an epitaxial layer is relieved, and the defect density in a film is relieved, thereby realizing the growth of the AlGaN film with high crystal quality and high Al component; the invention can effectively reduce the formation of dislocation, prepare the high-quality high-Al component AlGaN film, is beneficial to improving the radiation recombination efficiency of carriers, reduces the non-radiation recombination efficiency, and can greatly improve nitride semiconductor devices such as semiconductor lasers, photoelectric detectors and light emitting diodes; according to the invention, Si is used as the substrate, the substrate is easy to obtain and low in price, and the production cost is favorably reduced; the growth process of the invention is unique, simple and feasible, and has repeatability; the method can obtain the epitaxial layer film with high quality and smooth interface, and further prepare the AlGaN-based photoelectric device with high performance and high luminous efficiency.

The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Claims (10)

1. An AlGaN thin film structure on a Si substrate, comprising: the high-temperature AlGaN light-emitting diode comprises a basic AlN layer grown on a Si substrate, a first high-temperature AlN layer grown on the basic AlN layer, a low-temperature AlN layer grown on the first high-temperature AlN layer, a second high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the second high-temperature AlN layer and a second AlGaN layer grown on the first AlGaN layer, wherein the thickness of the second AlGaN layer is larger than that of the first AlGaN layer.

2. The Si-substrate AlGaN thin film structure according to claim 1, wherein the thickness of the basic AlN layer is 10 to 200 nm.

3. The Si-substrate AlGaN thin film structure according to claim 1, wherein the first high-temperature AlN layer has a thickness of 200 to 500 nm.

4. The Si-substrate AlGaN thin film structure according to claim 3, wherein the first high-temperature AlN layer has a thickness of 300to 400 nm.

5. The Si-substrate AlGaN thin film structure according to claim 1, wherein the low-temperature AlN layer has a thickness of 200 to 500 nm.

6. The Si-substrate AlGaN thin film structure according to claim 5, wherein the low-temperature AlN layer has a thickness of 300to 400 nm.

7. The Si-substrate AlGaN thin film structure according to claim 1, wherein the second high-temperature AlN layer has a thickness of 500 to 800 nm.

8. The Si-substrate AlGaN thin film structure according to claim 1, wherein the first AlGaN layer has a thickness of 100 to 300 nm.

9. The Si-substrate AlGaN thin film structure according to claim 1, wherein the second AlGaN layer has a thickness of 800 to 2000 nm.

10. The method for preparing an AlGaN thin film structure of a Si substrate according to any one of claims 1 to 9, comprising:

selecting a Si substrate;

growing a basic AlN layer on the Si substrate;

growing a first high-temperature AlN layer on the base AlN layer;

growing a low-temperature AlN layer on the first high-temperature AlN layer;

growing a second high-temperature AlN layer on the low-temperature AlN layer;

growing a first AlGaN layer on the second high-temperature AlN layer;

growing a second AlGaN layer on the first AlGaN layer.

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