Impact of sandwiched strain periodic multilayer AlN/GaN on strain and crystalline quality of a-plane GaN

Anas Kamarundzaman,Wan Haliza Abd Majid,Azzuliani Supangat,Al-Zuhairi Omar,Adreen Azman,Ahmad Shuhaimi Abu Bakar,Noor Azrina Talik

doi:10.1038/s41598-021-89201-8

Anas Kamarundzaman, Wan Haliza Abd Majid + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-89201-8

Copy DOI

Abstract

We demonstrated high-quality single crystalline a-plane undoped-gallium nitride grown on a nonpatterned r-plane sapphire substrate via metal–organic chemical vapor deposition. The effect of four different numbers of sandwiched strain-periodic AlN/GaN multilayers on the strain state, crystal quality, optical and electrical properties was investigated. Field emission scanning electron microscopy and atomic force microscopy showed that the surface morphology was improved upon insertion of 120 pairs of AlN/GaN thin layers with a root-mean-square roughness of 2.15 nm. On-axis X-ray ω-scan rocking curves showed enhanced crystalline quality: the full width at half maximum decreased from 1224 to 756 arcsec along the [0001] direction and from 2628 to 1360 arcsec along the [1–100] direction for a-GaN grown with 120 pairs of AlN/GaN compared to a-GaN without AlN/GaN pairs. Reciprocal space mapping showed that a-plane GaN with a high number of AlN/GaN pairs exhibits near-relaxation strain states. Room-temperature photoluminescence spectra showed that the sample with the highest number of AlN/GaN pairs exhibited the lowest-intensity yellow and blue luminescence bands, indicating a reduction in defects and dislocations. The a-plane InGaN/GaN LEDs with 120 pairs of SSPM-L AlN/GaN exhibited a significant increase (~ 250%) in light output power compared to that of LEDs without SSPM-L AlN/GaN pairs.

Highlights

The performance of gallium nitride (GaN)-based light-emitting devices has improved tremendously in recent years
The objective of this study was to investigate how different numbers of sandwiched strain-periodic multilayer (SSPM-L) enhance the surface morphology, crystalline quality and strain state of a-GaN epitaxial layers grown on r-sapphire for application to light-emitting devices
The results showed the surface morphology, crystalline quality and strain state of the a-GaN epitaxial layer were clearly enhanced for a large number of SSPM-L AlN/GaN

Summary

Introduction

The performance of gallium nitride (GaN)-based light-emitting devices has improved tremendously in recent years. The lattice mismatch and thermal expansion coefficient differential along the [11,12,13,14,15,16,17,18,19,20] and [0001] directions induce distortions in the grown GaN unit cell that interrupt hexagonal symmetry This phenomenon promotes defects and increases the densities of dislocations, such as BSFs and TDs, leading to challenges in determining the lattice parameters, because more variables need to be c onsidered. The objective of this study was to investigate how different numbers of SSPM-Ls enhance the surface morphology, crystalline quality and strain state of a-GaN epitaxial layers grown on r-sapphire for application to light-emitting devices. The a-plane InGaN/GaN LEDs exhibited a high output power and high indium (In) incorporation for a InGaN/GaN multiple-quantum well (MQW) grown on a large number of SSPM-L AlN/GaN pairs

Objectives

Methods

Results

Conclusion