CN1314078C - Cd(In,Ga)2O4/MgAl2O4Composite substrate material and preparation method thereof - Google Patents

Abstract

A Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material and a preparation method thereof. The composite substrate material is composed of a Cd(In, Ga) O ₄ covering layer provided on a MgAl ₂ O ₄ single crystal. The preparation method of the composite substrate material is: forming a Cd(In, Ga) O ₄ covering layer on a MgAl ₂ O ₄ (111) single crystal substrate by a pulse laser deposition method, and obtaining a crystallized Cd(In, Ga) O ₄ (111) thin film on the MgAl ₂ O ₄ (111) single crystal substrate through an annealing process. The preparation process of the composite substrate material of the invention is simple and easy to operate. The composite substrate Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ with such a structure is suitable for the epitaxial growth of high-quality GaN.

Description

Cd(In, Ga)2O4/MgAl2O4 Composite Substrate Material and Its Preparation Method

technical field

The invention relates to the epitaxial growth of InN-GaN-based blue light semiconductors, in particular to a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material and a preparation method thereof for the epitaxial growth of InN-GaN-based blue light semiconductors.

Background technique

Wide bandgap III-V compound semiconductor materials represented by GaN are receiving more and more attention, and they will be used in blue and green light-emitting diodes (LEDs) and laser diodes (LDs), high-density information reading and writing, underwater It has broad application prospects in communication, deep water exploration, laser printing, biological and medical engineering, as well as ultra-high-speed microelectronic devices and ultra-high-frequency microwave devices.

Due to GaN's high melting point, high hardness, and high saturated vapor pressure, high temperature and elegance are required to grow large-sized GaN bulk single crystals. The Polish High Pressure Research Center only produced strips with a width of 5 mm at a high temperature of 1600 ° C and a high pressure of 20 kbar. GaN bulk single crystal. At present, the technology to grow large-sized GaN bulk single crystals is still immature, and the cost of growth is high, and there is still a long distance from practical application.

Sapphire crystal (α-Al ₂ O ₃ ) is easy to prepare, cheap, and has good high temperature stability. α-Al ₂ O ₃ is currently the most commonly used InN-GaN epitaxial substrate material (see Jpn.J .Appl.Phys., Vol. 36, 1997, p. 1568).

The MgAl ₂ O ₄ crystal belongs to the cubic crystal system, the spinel structure, the lattice constant is 0.8083nm, and the melting point is 2130°C. Because the lattice mismatch between MgAl ₂ O ₄ and GaN reaches 9%, and its comprehensive properties are not as good as α-Al ₂ O ₃ , it is rarely used.

Currently, typical GaN-based blue LEDs are fabricated on sapphire substrates. Its structure is as follows from top to bottom: p-GaN/AlGaN barrel layer/InGaN-GaN quantumwells/AlGaN barrier layer/n-GaN/4μm GaN. Due to the extremely high resistivity of sapphire, the n-type and p-type electrodes of the device must be brought out from the same side. This not only increases the manufacturing difficulty of the device, but also increases the volume of the device. According to relevant data, for a sapphire substrate with a diameter of 2 inches, the current technology can only produce about 10,000 GaN devices. If the substrate material has a suitable conductivity, it will simplify the device manufacturing process. At the same time, its number can be increased to 3-4 times of the present.

In summary, prior art substrates (α-Al ₂ O ₃ and MgAl ₂ O ₄ ) have significant disadvantages:

(1) Using α-Al ₂ O ₃ as the substrate, the lattice mismatch between α-Al ₂ O ₃ and GaN is as high as 14%, which means that the prepared GaN film has a higher dislocation density and a large number of dots defect;

(2) Since the lattice mismatch between MgAl ₂ O ₄ and GaN reaches 9%, and the overall performance is not as good as that of α-Al ₂ O ₃ , it is less used;

(3) The above transparent oxide substrates are all non-conductive, making the device difficult to manufacture, and also increases the volume of the device, resulting in a lot of waste of raw materials.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material and its Preparation.

The Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material of the present invention is actually composed of a layer of Cd(In, Ga) ₂ O ₄ on the MgAl ₂ O ₄ single crystal. The bottom is suitable for epitaxial growth of high-quality InN-GaN-based blue semiconductor thin films.

Cd(In, Ga) ₂ O ₄ is a solid solution compound formed by CdIn ₂ O ₄ and CdGa ₂ O ₄ , which belongs to cubic crystal system and spinel structure. The lattice mismatch between Cd(In, Ga) ₂ O ₄ (111) and GaN is very small. When CdIn ₂ O ₄ and CdGa ₂ O ₄ form a solid solution in an appropriate ratio, its (111) plane can be completely compatible with GaN However, due to the difficulty in growing large-size Cd(In, Ga) ₂ O ₄ bulk single crystals, the present invention proposes a method of using pulsed laser deposition to grow Cd(In, Ga) ₂ on MgAl ₂ O ₄ single crystal substrates O ₄ covering layer, thereby obtaining a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. Here, the _{MgAl2O4 single} crystal acts as _a support for the Cd(In,Ga) _2O4 transparent conductive thin film on it. The composite substrate [Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ ] with this structure is suitable for epitaxial growth of high-quality GaN.

Technical solution of the present invention is:

A preparation method of Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material, which mainly uses pulsed laser deposition method to prepare Cd(In, Ga) ₂ on MgAl ₂ O ₄ single crystal substrate O ₄ thin film, through high temperature annealing, form Cd(In, Ga) ₂ O ₄ single crystal capping layer on MgAl ₂ O ₄ single crystal substrate.

The preparation method of the preparation material of the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material of the present invention is characterized in that it includes the following specific steps:

<1> Preparation of Cd(In, Ga) ₂ O ₄ film on MgAl ₂ O ₄ single crystal substrate: send the polished and cleaned MgAl ₂ O ₄ single crystal substrate into the pulsed laser deposition system, Cd(In , Ga) ₂ O ₄ source adopts Cd(In,Ga) ₂ O ₄ polycrystalline target material; adopts KrF excimer laser with pulse width of 25-30ns, the lasing wavelength is 248nm, and the energy of about 10J/cm ² is passed through the lens Density concentrated light, irradiating the Cd(In, Ga) ₂ O ₄ target in the vacuum device through the optical window, and depositing Cd(In, Ga) 2 O 4 on the heated MgAl ₂ O ₄ single crystal substrate In, Ga) ₂ O ₄ film, the film thickness is greater than 100nm.

<2>High-temperature annealing: Put the obtained Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ sample into an annealing furnace, raise the temperature, and anneal at 700-1500°C in an oxygen-rich atmosphere to obtain Cd( In, Ga) ₂ O ₄ single crystal covering layer, forming Cd (In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material.

The raw material used for the Cd(In, Ga) ₂ O ₄ polycrystalline target and its ratio are CdO:In ₂ O ₃ :Ga ₂ O ₃ =2:1:1, and the purity of the obtained polycrystalline target is better than 99.999% %.

For the high temperature annealing treatment, the optimum temperature in the annealing furnace is 1000°C.

The features of the present invention are:

(1) A Cd(In, Ga) ₂ O ₄ substrate material for the epitaxial growth of InN-GaN-based blue light semiconductors is proposed. The degree of lattice mismatch is small, and the ratio of Mg and Cd can be appropriately changed to match the lattice of GaN (111), and the material is a transparent conductive oxide material.

(2) The present invention proposes to use pulsed laser deposition (PLD) technology to generate a Cd(In, Ga) ₂ O ₄ capping layer on a MgAl ₂ O ₄ single crystal substrate, thereby obtaining Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. The preparation process of the composite substrate is simple and easy to operate. The composite substrate [Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ ] with this structure is suitable for high-quality Epitaxial growth of GaN.

Description of drawings

Figure 1 is a schematic diagram of a pulsed laser deposition (PLD) system.

Detailed ways

Figure 1 is a schematic diagram of a pulsed laser deposition (PLD) system. The mechanism of PLD is to first focus the laser light of KrF excimer laser with a pulse width of 25-30ns and a wavelength of 248nm through the lens with an energy density of about 10J/ ^cm2 , and irradiate the Cd(In, Ga) in the vacuum device through the optical window. ₂ O ₄ polycrystalline target, after the target absorbs the laser, it becomes a high-temperature molten state due to electronic excitation, so that the surface of the material is evaporated and gasified, and the gaseous particles are released and diffused in columnar shape. Cd (In, Ga) ₂ O ₄ film is deposited on a suitably heated MgAl ₂ O ₄ single crystal substrate placed a few centimeters away from the target, attached and stacked. The film thickness is greater than 100nm.

The pulse laser deposition (LPD) technique of the present invention prepares composite substrate material Cd (In, Ga) ₂ O ₄ /MgAl ₂ O ₄ The specific technological process of 4 is as follows:

<1> Send the polished and _cleaned MgAl ₂ O ₄ single crystal substrate into the pulsed laser deposition PLD system to prepare Cd(In, Ga) _{2 O 4 thin} film, and prepare Cd( In, Ga) ₂ O ₄ film, Cd (In, Ga) ₂ O ₄ source adopts more than 99.999% Cd (In, Ga) ₂ O ₄ polycrystalline target, the raw material used for the target is CdO: In ₂ O ₃ : Ga ₂ O ₃ =2:1:1. The system uses a KrF excimer laser with a pulse width of 25-30ns, the lasing wavelength is 248nm, the light is condensed through the lens with an energy density of about 10J/ ^cm2 , and irradiated to the Cd(In, Ga) ₂ O in the vacuum device through the optical window. ₄ target material, deposit Cd(In,Ga) ₂ O ₄ film in an oxygen-rich atmosphere, and the film thickness is greater than 100nm.

<2>Then put the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ sample obtained in the previous step into the annealing furnace, and anneal at 700-1500°C to obtain the Cd(In, Ga) ₂ O ₄ single crystal capping layer, thus obtaining the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. The composite substrate with this structure is suitable for the epitaxial growth of high-quality GaN.

The method for preparing the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate material with the pulsed laser deposition (PLD) experimental device shown in Figure 1 is described as follows with a preferred embodiment:

Example 1:

Send the polished and cleaned MgAl ₂ O ₄ single crystal substrate into the pulsed laser deposition PLD system to prepare Cd(In, Ga) ₂ O ₄ thin film, and the Cd(In, Ga) ₂ O ₄ source uses more than 99.999% Cd (In, Ga) ₂ O ₄ polycrystalline target. The system uses a KrF excimer laser with a pulse width of 25-30ns, the lasing wavelength is 248nm, the light is condensed through the lens with an energy density of about 10J/ ^cm2 , and irradiated to the Cd(In, Ga) ₂ O in the vacuum device through the optical window. ₄ target material, deposit Cd(In, Ga) ₂ O ₄ film in an oxygen-rich atmosphere, MgAl ₂ O ₄ single crystal substrate temperature is 300 ℃, control the thickness of Cd(In, Ga) ₂ O ₄ film to 300nm. Then put the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ sample obtained in the above step into an annealing furnace, raise the temperature to 1000°C for annealing treatment, and obtain a Cd(In, Ga) ₂ O ₄ single crystal covering layer, thereby obtaining a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. The composite substrate with this structure is suitable for the epitaxial growth of high-quality GaN.

Example 2:

Send the polished and cleaned MgAl ₂ O ₄ single crystal substrate into the pulsed laser deposition PLD system to prepare Cd(In, Ga) ₂ O ₄ thin film, and the Cd(In, Ga) ₂ O ₄ source uses more than 99.999% Cd (In, Ga) ₂ O ₄ polycrystalline target. The system uses a KrF excimer laser with a pulse width of 25-30ns, the lasing wavelength is 248nm, the light is condensed through the lens with an energy density of about 10J/ ^cm2 , and irradiated to the Cd(In, Ga) ₂ O in the vacuum device through the optical window. ₄ target material, deposit Cd(In, Ga) ₂ O ₄ film in an oxygen-rich atmosphere, MgAl ₂ O ₄ single crystal substrate temperature is 100 ℃, control the thickness of Cd(In, Ga) ₂ O ₄ film to 100nm. Then put the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ sample obtained in the above step into the annealing furnace, raise the temperature to 700°C for annealing treatment, and obtain the single crystal covering of Cd(In, Ga) ₂ O ₄ layer, thereby obtaining a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. The composite substrate with this structure is suitable for the epitaxial growth of high-quality GaN.

Example 3:

Send the polished and cleaned MgAl ₂ O ₄ single crystal substrate into the pulsed laser deposition PLD system to prepare Cd(In, Ga) ₂ O ₄ thin film, and the Cd(In, Ga) ₂ O ₄ source uses more than 99.999% Cd (In, Ga) ₂ O ₄ polycrystalline target. The system uses a KrF excimer laser with a pulse width of 25-30ns, the lasing wavelength is 248nm, the light is condensed through the lens with an energy density of about 10J/ ^cm2 , and irradiated to the Cd(In, Ga) ₂ O in the vacuum device through the optical window. ₄ target material, deposit Cd(In, Ga) ₂ O ₄ film in an oxygen-rich atmosphere, MgAl ₂ O ₄ single crystal substrate temperature is 300 ℃, control the thickness of Cd(In, Ga) ₂ O ₄ film to 500nm. Then put the Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ sample obtained in the above step into an annealing furnace, raise the temperature to 1500°C for annealing treatment, and obtain a Cd(In, Ga) ₂ O ₄ single crystal covering layer, thereby obtaining a Cd(In, Ga) ₂ O ₄ /MgAl ₂ O ₄ composite substrate. The composite substrate with this structure is suitable for the epitaxial growth of high-quality GaN.

Claims (6)

1, a kind of Cd (In, Ga) ₂O ₄/ MgAl ₂O ₄Compound lining material is characterized in that at MgAl ₂O ₄Monocrystalline is provided with one deck Cd (In, Ga) ₂O ₄, consist of Cd (In, Ga) ₂O ₄/ MgAl ₂O ₄Compound substrate.

2, the described Cd of claim 1 (In, Ga) ₂O ₄/ MgAl ₂O ₄The preparation method of compound lining material is characterized in that utilizing the pulsed laser deposition method at MgAl ₂O ₄Prepare Cd (In, Ga) on the single crystalline substrate ₂O ₄Film, and then by high annealing, at MgAl ₂O ₄Form the crystallization film on the single crystalline substrate.

3, Cd according to claim 2 (In, Ga) ₂O ₄/ MgAl ₂O ₄The preparation method of compound lining material is characterized in that described pulsed laser deposition method is to utilize the KrF PRK of pulsewidth 25-30ns, and scioptics are with 10J/cm ²Energy density optically focused, the Cd (In, Ga) in optical window shines vacuum plant ₂O ₄The source, this Cd (In, Ga) ₂O ₄The source is evaporated, at the MgAl of heating ₂O ₄On the single crystalline substrate, deposit becomes Cd (In, Ga) ₂O ₄Film, thickness is greater than 100nm.

4, Cd according to claim 2 (In, Ga) ₂O ₄/ MgAl ₂O ₄The preparation method of compound lining material is characterized in that it comprises following concrete steps:

＜1〉at MgAl ₂O ₄Prepare Cd (In, Ga) on the single crystalline substrate ₂O ₄Film: the MgAl that will polish, cleaned ₂O ₄Single crystalline substrate is sent into the pulsed laser deposition system, utilizes Cd (In, Ga) ₂O ₄Target, the KrF excimer laser of employing pulsewidth 25-30ns, excitation wavelength is 248nm, scioptics are with 10J/cm ²Energy density optically focused, the Cd (In, Ga) in optical window shines vacuum plant ₂O ₄Target is under the reaction atmosphere of oxygen enrichment, at the MgAl of heating ₂O ₄Deposit Cd (In, Ga) on the single crystalline substrate ₂O ₄Film, thickness is greater than 100nm.

＜2〉Cd (In, Ga) ₂O ₄The crystallization of film: with the Cd (In, Ga) that obtains ₂O ₄/ MgAl ₂O ₄Sample is put into annealing furnace, heats up, and anneals at 700～1500 ℃, obtains Cd (In, Ga) ₂O ₄The crystallization layer forms Cd (In, Ga) ₂O ₄/ MgAl ₂O ₄Compound lining material.

5, Cd according to claim 2 (In, Ga) ₂O ₄/ MgAl ₂O ₄The preparation method of compound lining material is characterized in that earlier with the synthetic Cd (In, Ga) of solid-phase sintering synthetic method ₂O ₄Target, target is raw materials used to be CdO: In ₂O ₃: Ga ₂O ₃=2: 1: 1.

6, Cd according to claim 2 (In, Ga) ₂O ₄/ MgAl ₂O ₄The preparation method of compound lining material, the temperature that it is characterized in that described high annealing is 1000 ℃.

Images