CN1313655C - Method for growing high-mobility gallium nitride epitaxial film - Google Patents

Abstract

A method for growing a high-mobility GaN epitaxial film, characterized in that it comprises the following steps: first growing a layer of low-temperature GaN nucleation layer on a substrate by metal-organic chemical vapor deposition; Temperature, grow a gallium nitride recovery layer on the low-temperature gallium nitride nucleation layer; finally, grow a non-intentionally doped gallium nitride layer on the gallium nitride recovery layer under the condition of a growth chamber pressure of 400-600torr, and the room temperature mobility Not less than 400cm ² /Vs.

Description

Method for growing high-mobility gallium nitride epitaxial film

technical field

The invention belongs to the technical field of semiconductors, in particular to an epitaxial growth method of a gallium nitride epitaxial film with room temperature mobility not less than 400 cm ² /Vs.

Background technique

As a typical representative of the third-generation semiconductor materials, III-V gallium nitride materials have great application prospects in the fields of optoelectronics and microelectronics due to their unique physical, chemical and mechanical properties. GaN materials can be used to prepare HEMT, HFET, HBT, JFET, MOSFET, SAW and other devices. Mobility is an important parameter to characterize the quality of materials, and the acquisition of high mobility materials is of great benefit to material research and device development. However, due to the lack of heterogeneous substrate materials that match GaN materials, the purity of the materials is difficult to improve, so it is difficult to obtain GaN materials with high mobility.

Before the present invention, the growth method of the high-mobility gallium nitride material that often adopts is: adopt metal-organic chemical vapor deposition (MOCVD) on the crystal plane of substrate sapphire (0001) or other substrates suitable for growing nitrides ) to grow a low-temperature GaN nucleation layer, and then increase the substrate temperature to grow an undoped or Si-doped GaN layer to improve mobility. If the doping method is used, although the doped atoms can improve the mobility of the GaN material, the doped atoms destroy the original crystal lattice of GaN, resulting in a decrease in the crystal quality of the GaN material. This approach therefore affects the performance of the material itself and the devices fabricated from it. For the method of directly growing intrinsic GaN without doping, the current mobility is mostly in the range of 200-500 cm ² /Vs. Therefore, how to further improve the mobility of non-doped GaN materials is an important issue in the development of nitride materials.

Contents of the invention

The purpose of the present invention is to provide a method for growing high-mobility gallium nitride epitaxial film, which method is through non-intentional doping, by controlling the growth conditions, such as temperature, pressure and adding a new structure of gallium nitride recovery layer, effectively The stress caused by lattice mismatch is relieved and the crystal quality is improved. A high-mobility intrinsic GaN material is grown. The invention also improves the flatness of the sample surface.

The present invention is a method for growing a high-mobility GaN epitaxial film, which is characterized in that it comprises the following steps:

First grow a low-temperature gallium nitride nucleation layer on the substrate by metal-organic chemical vapor deposition;

Then increase the temperature of the substrate, and grow a gallium nitride recovery layer on the low-temperature gallium nitride nucleation layer;

Finally, under the condition that the growth chamber pressure is 400-600 torr, a non-intentionally doped gallium nitride layer is grown on the gallium nitride recovery layer, and the mobility at room temperature is not less than 400cm ² /Vs.

The substrate mentioned therein is sapphire or silicon or silicon carbide or GaLiO ₃ , ZnO.

When growing the low-temperature GaN nucleation layer on the substrate, the temperature of the substrate is 500-600° C., the pressure is 400-600 torr, and the growth thickness is 0.01-0.06 μm.

Wherein, the growth temperature of the gallium nitride recovery layer is between 1000-1100° C., the growth pressure is 100-300 torr, and the growth thickness is 0.1-0.3 μm.

The growth temperature of the non-intentionally doped high-mobility gallium nitride layer is between 1000-1100° C., and the thickness of the gallium nitride film is 0.5-6 μm.

Description of drawings

To further illustrate the contents of the present invention, the present invention will be described in detail below in conjunction with specific embodiments, wherein:

1 is a schematic diagram of the growth structure of the intrinsic high mobility GaN layer of the present invention;

Fig. 2 is the variation curve of the mobility and carrier concentration of the high mobility GaN material of the present invention with temperature;

Fig. 3 is high mobility GaN X-ray rocking curve half peak width test result of the present invention;

Fig. 4 is the RMS test result of the surface roughness of the high mobility GaN of the present invention.

Detailed ways

The key of the invention lies in adding a new structure of gallium nitride recovery layer and growing non-intentionally doped high-mobility gallium nitride epitaxial film. By controlling the growth conditions, such as temperature and pressure to the optimum conditions, and with the addition of the new structure of the GaN recovery layer, the stress caused by the mismatch between the crystal lattice and the substrate is eliminated to the greatest extent, and the stress is the one that generates the crystal position. The main reason for the error. On the other hand, the non-intentionally doped GaN epitaxial layer effectively reduces the ionized impurities caused by doping, thereby improving the crystal quality and growing an intrinsic GaN material with high mobility. The invention also improves the flatness of the sample surface.

Please refer to Fig. 1, a method for growing a high-mobility gallium nitride epitaxial film of the present invention, comprising the following steps:

First grow a layer of low-temperature gallium nitride nucleation layer 20 on the substrate 10 by metal-organic chemical vapor deposition (MOCVD); wherein the substrate 10 is sapphire or silicon or silicon carbide or GaLiO ₃ , ZnO; wherein the substrate When growing the low-temperature gallium nitride nucleation layer 20 on the substrate 10, the temperature of the substrate 10 is 500-600° C., the pressure is 400-600 torr, and the growth thickness is 0.01-0.06 μm;

Then increase the temperature of the substrate 10, and grow the gallium nitride recovery layer 30 on the low-temperature gallium nitride nucleation layer 20; wherein the growth temperature of the gallium nitride recovery layer 30 is between 1000-1100° C., and the growth pressure is 100-300 torr, The growth thickness is 0.1-0.3μm;

Finally, change the pressure of the growth chamber to grow the non-intentionally doped high-mobility GaN layer 40 on the GaN recovery layer 30; wherein the growth temperature of the non-intentionally doped high-mobility GaN layer 40 is between 1000-1100°C , the growth pressure is 400-600torr, and the gallium nitride film thickness is 0.5-6μm.

The gallium nitride grown by this method is high-mobility gallium nitride, and the mobility at room temperature is not less than 400 cm ² /Vs.

Example

Referring to Fig. 1, a method for growing a high-mobility gallium nitride epitaxial film of the present invention comprises the following steps:

1. Metal-organic chemical vapor deposition (MOCVD) is used on the substrate 10 sapphire (0001) or silicon (111) or silicon carbide (0001) or other substrates suitable for growing nitrides, such as GaLiO ₃ , ZnO, etc. A low-temperature gallium nitride nucleation layer is grown. The substrate temperature is about 500-600° C., the pressure is 400-600 torr, and the growth thickness is 0.01-0.06 μm.

2. Afterwards, the temperature of the substrate 10 is increased to grow the gallium nitride recovery layer. The growth temperature of the gallium nitride recovery layer is between 1000-1100° C., the growth pressure is 100-300 torr, and the growth thickness is 0.1-0.3 μm.

3. Finally, change the growth chamber pressure, unintentionally dope the high-mobility gallium nitride layer, the growth temperature is between 1000-1100°C, the growth pressure is 400-600torr, and the thickness of the gallium nitride film is about 0.5-6μm.

The samples obtained by the above steps are tested and analyzed, and it is proved that the gallium nitride grown by this method is a high-mobility gallium nitride material. Using the Vanderbilt HALL test method, it was confirmed that the mobility of the material is greater than 730cm ² /Vs at room temperature 300K, the carrier concentration is 1.8×10 ¹⁶ cm ^-3 , and the mobility at 77K is 1580cm ² /Vs, and the carrier concentration is 4.0×10 ¹⁵ cm ^-3 (Figure 2); at the same time, the crystal quality has been improved, and the half-maximum width of the rocking curve of the (0002) plane of the material is confirmed to be less than 6arcmin. (Figure 3) using a twin-crystal X-ray diffraction method; atomic force microscopy (AFM) The test method confirmed that the material had a surface roughness (RMS) of 0.159nm (Figure 4). The invention reduces the difficulty of the process, reduces the steps of the process, grows the high-quality intrinsically high-mobility gallium nitride material at one time, and optimizes the growth process.

Claims (5)

1. the method for high mobility epitaxy of gallium nitride film of growing is characterized in that, comprises the steps:

On substrate, adopt metal-organic chemical vapor deposition equipment growth one deck low temperature gan nucleating layer earlier;

The substrate temperature that raises subsequently, growing gallium nitride recovers layer on low temperature gan nucleating layer;

Be under the 400-600torr condition at growth room's pressure at last, recover the non-doped gallium nitride layer intentionally of growth on the layer at gan, this layer gallium nitride room temperature mobility is not less than 400cm ²/ V.s.

2. the method for growth high mobility epitaxy of gallium nitride film according to claim 1 is characterized in that, wherein said substrate is sapphire or silicon or silicon carbide or GaLiO ₃, ZnO.

3. the method for growth high mobility epitaxy of gallium nitride film according to claim 1, it is characterized in that wherein on substrate during growing low temperature gan nucleating layer, substrate temperature is 500-600 ℃, pressure is 400-600torr, and growth thickness is 0.01-0.06 μ m.

4. the method for growth high mobility epitaxy of gallium nitride film according to claim 1 is characterized in that, wherein between growth temperature 1000-1100 ℃ of gan recovery layer, growth pressure 100-300torr, growth thickness are 0.1-0.3 μ m.

5. the method for growth high mobility epitaxy of gallium nitride film according to claim 1, it is characterized in that, recover on the layer at gan wherein that growth is non-to be had a mind to mix during the high mobility gallium nitride layer, growth temperature is between 1000-1100 ℃, and the gan thickness is 0.5-6 μ m.

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