V-shaped dislocations in a GaN epitaxial layer on GaN substrate

Atsushi Tanaka,Manato Deki,Michal Bockowski,Maki Kushimoto,Hiroshi Amano,Shigeyoshi Usami,Shugo Nitta,Kentaro Nagamatsu,Yoshio Honda

doi:10.1063/1.5114866

Abstract

In this study, V-shaped dislocations in a GaN epitaxial layer on a free-standing GaN substrate were observed. Our investigation further revealed that the V-shaped dislocations were newly generated at the interface in the epilayer rather than propagated from the GaN substrate. V-shaped dislocations consist of two straight parts. The straight parts of the V-shaped dislocations were separated from each other in the m-direction and tilted toward the step-flow direction of the GaN epitaxial layer. The V-shaped dislocations are continuous single dislocations having a Burgers vector component of 1a and an intrinsic stacking fault between their straight parts.

Highlights

A commercially available epi-ready n-type Gallium nitride (GaN) (0001) substrate20 with a threading dislocation density (TDD) of 103 cm−2 was used in this study
An undoped GaN epitaxial layer was grown on the substrate by metalorganic vapor phase epitaxy (MOVPE), in which trimethylgallium (TMGa) and ammonia (NH3) were used as precursors and hydrogen (H2) was the carrier gas
We investigated dislocation propagation in the samples by multiphoton excitation photoluminescence microscopy (MEPM), which is an excellent tool for observing the shape of dislocations in GaN as reported in Ref. 21

Summary

Introduction

ABSTRACT In this study, V-shaped dislocations in a GaN epitaxial layer on a free-standing GaN substrate were observed. Our investigation further revealed that the V-shaped dislocations were newly generated at the interface in the epilayer rather than propagated from the GaN substrate. The straight parts of the V-shaped dislocations were separated from each other in the m-direction and tilted toward the step-flow direction of the GaN epitaxial layer.

Results

Conclusion