Strain of M-plane GaN epitaxial layer grown on β-LiGaO2 (100) by plasma-assisted molecular beam epitaxy

Shuo-Ting You,Ikai Lo,Hui-Chun Hang,Mitch M C Chou,Huei-Jyun Shih

doi:10.1063/1.5037006

Abstract

We have grown a high-quality single-phase M-plane GaN on β-LiGaO2 (100) by plasma-assisted molecular beam epitaxy. The Hooke’s law for M-plane GaN was derived by a stress tenor transformation. From the analysis of M-plane GaN microstructure, the lattice strain of M-plane GaN along the [112¯0] and [0001] directions have been estimated. Based on the Hooke’s law, we calculated the ratio of anisotropic stress which was consistent with the ratio of thermal expansion-mismatch between GaN and LiGaO2 (100). We demonstrated that the thermal expansion mismatch was the major factor to degrade the quality of M-plane GaN on β-LiGaO2 (100).

Highlights

Wide direct bandgap semiconductor GaN has been applied to optoelectronic devices, such as light emitting diodes and laser diodes, for the region of blue and ultraviolet
The in-suit surface structure was characterized by the reflection high-energy electron diffraction (RHEED) measurement during the epilayer growth
Diffraction pattern which corresponded with GaN (101 ̄0) surface and the streaky diffraction pattern indicated that the growth of GaN on β-LiGaO2 was a 2D growth mode.[13]

Summary

Introduction

Wide direct bandgap semiconductor GaN has been applied to optoelectronic devices, such as light emitting diodes and laser diodes, for the region of blue and ultraviolet. In the general epitaxy of wurtzite film, the growth of GaN on sapphire (0001) substrate is a c-plane structure which is grown along with the [0001] direction. When the GaN/AlGaN heterostructure quantum-well is established, it will produce a quantum-confined Stark effect which diminishes luminous efficiency due to spatial separation of electron and hole carriers along [0001] direction by strong spontaneous and piezoelectric fields.[1] the growth of nonpolar M-plane GaN was considered to avoid the quantum-confined Stark effect in GaN/AlGaN quantum-well structure.[2] Many researches tried to grow M-plane GaN on different substrates such as Si (112), 4H-SiC and M-plane sapphire but these substrates had a common disadvantage of large lattice mismatch.[3,4,5,6] Because of the large lattice mismatch, the growth of M-plane GaN on these substrates induces a large stress in GaN epi-layers with high density of dislocations. We resolve the epi-layer peeling problem by a pre-cleaning substrate process to demonstrate a high-quality single-phase M-plane

Methods

Results

Conclusion