Method of preparing low-dislocation density GaN thin film on Si substrate by adopting carbon nanotubes as periodic dielectric mask

Abstract

The invention provides a method of preparing a low-dislocation density GaN thin film on a Si substrate by adopting carbon nanotubes as a periodic dielectric mask. The method comprises steps: trimethylgallium (TMGa) and trimethylaluminum (TMAl) are used as an III-group source, an ammonia gas (NH3) serves as a V-group source, silane (SiH4) serves as an n-type doping source, after a high-temperature AlN nucleation layer grows on the Si substrate, two layers or three layers or four layers one-way (crossed) carbon nanotube periodic dielectric masks are prepared to pattern the AlN / Si substrate layer; then, a selective area epitaxial method is adopted to grow a low-Al component AlxGa1-xN merged layer with a thickness of 0.3 to 0.5 micrometer and the Al component no more than 0.25 on the patterned AlN / Si substrate template; then, four layers of GaN grow respectively, three layers of low-temperature AlyGa1-yN stress control layers are inserted in two GaN layers, wherein the Al component y is gradually decreased along with the increasing of layers and y is no less than 0.5 but no more than 1; and thus, the low-dislocation density, non-crack and high-crystal quality GaN / Si thin film can be acquired, wherein the thin film has a thickness of 2 micrometer, the half width of the 002 surface is 500 aresec, and the half width of the 102 surface is 610 aresec.

Description

technical field [0001] The invention belongs to the technical field of semiconductor optoelectronics, and relates to a method for preparing a low dislocation density GaN thin film on a Si substrate, in particular to a method for patterning an AlN / Si substrate template using a carbon nanotube periodic dielectric mask, and forming an AlN / Si substrate template on a GaN During the growth process, the technology of inserting and growing a multilayer low-temperature AlGaN layer whose Al composition decreases with the increase of the layer is used as the stress control layer, and the method of preparing a GaN film with low dislocation density, no cracks and high crystal quality on the Si substrate. Background technique [0002] The Si substrate is large in size and cheap, which can reduce the cost of epitaxial growth. Compared with the insulating sapphire substrate with high hardness and poor thermal conductivity, the conductive Si substrate can effectively simplify the substrate t...

AI Technical Summary

Problems solved by technology

However, the problems and difficulties in growing GaN on Si substrates by metalorganic vapor phase epitaxy (MOVPE) method lie in: ① The lattice distortion of (0001) GaN wurtzite structure and Si (111) substrate with diamond structure The ratio is 20.4%, which will generate a large number of dislocations; ②The thermal mismatch between GaN and Si is as high as 56%, and the epitaxial layer will bear a large tensile stress during the cooling project after the epitaxial growth is completed

Since the thickness of the epitaxial layer is much smaller than that of the substrate, microcracks will occur in the epitaxial layer, which seriously affects the characteristics of GaN devices

③ When GaN is directly grown on Si substrate, NH 3 It is easy to react with the substrate Si to form amorphous SiN on the substrate surface, which affects the growth quality of GaN

④There is also a strong chemical reaction between the metal Ga and the substrate Si, which will cause the substrate to dissolve back, thereby destroying the flatness of the interface

⑤When growing at high temperature, Si in the substrate will diffuse to the surface of the buffer layer. If not properly controlled, it will affect the growth mode of GaN, thus destroying the crystal quality

⑥In addition, since Si is a non-polar semiconductor, there will be some problems related to the polarity of the compound when GaN, AlN or other polar semiconductors are grown on it

But the dislocation density is still high

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