Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers.

Yuan Gao,Hongchang Tao,Shengrui Xu,Ruoshi Peng,Yue Hao,Jincheng Zhang

doi:10.3390/ma13183933

Abstract

The utilization of sputtered AlN nucleation layers (NLs) and patterned sapphire substrates (PSSs) could greatly improve GaN crystal quality. However, the growth mechanism of GaN on PSSs with sputtered AlN NLs has not been thoroughly understood. In this paper, we deposited AlON by sputtering AlN with O2, and we found that the variation of thickness of sputtered AlON NLs greatly influenced GaN growth on PSSs. (1) For 10 nm thin AlON sputtering, no AlON was detected on the cone sidewalls. Still, GaN nucleated preferably in non-(0001) orientation on these sidewalls. (2) If the thickness of the sputtered AlON NL was 25 nm, AlON formed on the cone sidewalls and flat regions, and some small GaN crystals formed near the bottom of the cones. (3) If the sputtered AlON was 40 nm, the migration ability of Ga atoms would be enhanced, and GaN nucleated at the top of the cones, which have more chances to grow and generate more dislocations. Finally, the GaN growth mechanisms on PSSs with sputtered AlON NLs of different thicknesses were proposed.

Highlights

GaN-based light emitting diodes (LEDs) and laser diodes (LDs) have made huge progress in recent years [1,2,3]
Many works proved that the utilization of sputtered AlN/patterned sapphire substrates (PSSs) templates could improve the performance of GaN-based LEDs [18,19]
We systematically discussed the differences of GaN growth mechanisms on PSSs with sputtered AlON nucleation layers (NLs) of different thickness

Summary

Introduction

GaN-based light emitting diodes (LEDs) and laser diodes (LDs) have made huge progress in recent years [1,2,3]. With the appropriate nucleation layer (NL), most GaN grows in the flat regions between cones, though the flat region is a rather small proportion of the whole substrate, no matter what the geometry of the pattern is [10,11,12]. When using metal organic chemical vapor deposition (MOCVD) to grow AlN or GaN NLs, the influences of small GaN crystals become more noteworthy [13,14,16]. Compared to MOCVD-grown AlN or GaN NLs, Li-Chuan Chang et al found that the utilization of ex situ sputtered AlN NLs could suppress GaN nucleation on cones and improve the quality of GaN films on PSSs [17]. Many works proved that the utilization of sputtered AlN/PSS templates could improve the performance of GaN-based LEDs [18,19]

Methods

Results

Conclusion