경사면 사파이어 기판을 이용한 무극성 m면 질화갈륨 박막 성장 방법

Abstract

Most of GaN-based devices have been grown on polar GaN along the [0001] direction. But, GaN-based materials have large piezoelectric fields, therefore piezoelectric fields can be reduced in the polarization. Thus, we conclude that efficient optical devices can be obtained by control of the crystal orientation, growth of the non-polar epilayer is indispensable. The proposal suggests using off-cut (1010) plane sapphire substrate to achieve high quality non-polar (1010) plane GaN thin film.

In previous studies, non-polar growth methods have been attempted MOVPE, MOCVD, HVPE, MBE and various growth systems. However, it is difficult to grow non-polar nitrides grown on due to the strong anisotropy of the surface properties epitaxial layers with a high density of crystalline defects. So, In-situ surface observation is effective to control dislocation densities as possible in non-polar growth by using gas-source molecular beam epitaxy.

In this experiment, we reported epitaxial growth of m- plane GaN on m- sapphire substrates, We have found that the crystal orientations of the as grown m- plane GaN either non-polar m- plane (1010) / semi-polar (1122) and (1013) plane. Grown under identical condition, for the epitaxial layer affects the surface morphology by the growth of nitridation temperature [low temperature nitridation (LNT) and high temperature nitridation (HNT)] depend on. The substrates were on a- axis 2 degree off-angle m-sapphire.

Analysis of crystal orientations were indexed surface by reflection high energy electron diffraction (RHEED), evaluated of optical properties by photoluminescence (PL), Surface morphologies of the samples were characterized by field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM).