The impact of point defects in n-type GaN layers on thermal decomposition of InGaN/GaN QWs

Mikolaj Grabowski,Julita Smalc-Koziorowska,Szymon Grzanka,Grzegorz Gawlik,Robert Czernecki,Andrzej Turos,Mike Leszczyński,Roman Hrytsak,Ewa Grzanka,Joanna Moneta,Artur Lachowski

doi:10.1038/s41598-021-81017-w

Abstract

The aim of this paper is to give an experimental evidence that point defects (most probably gallium vacancies) induce decomposition of InGaN quantum wells (QWs) at high temperatures. In the experiment performed, we implanted GaN:Si/sapphire substrates with helium ions in order to introduce a high density of point defects. Then, we grew InGaN QWs on such substrates at temperature of 730 °C, what caused elimination of most (but not all) of the implantation-induced point defects expanding the crystal lattice. The InGaN QWs were almost identical to those grown on unimplanted GaN substrates. In the next step of the experiment, we annealed samples grown on unimplanted and implanted GaN at temperatures of 900 °C, 920 °C and 940 °C for half an hour. The samples were examined using Photoluminescence, X-ray Diffraction and Transmission Electron Microscopy. We found out that the decomposition of InGaN QWs started at lower temperatures for the samples grown on the implanted GaN substrates what provides a strong experimental support that point defects play important role in InGaN decomposition at high temperatures.

Highlights

IntroductionThe aim of this paper is to give an experimental evidence that point defects (most probably gallium vacancies) induce decomposition of InGaN quantum wells (QWs) at high temperatures
The aim of this paper is to give an experimental evidence that point defects induce decomposition of InGaN quantum wells (QWs) at high temperatures
Since Si-doped n-type GaN layer grown in MOVPE method contains a high concentration of Ga-vacancies[9] we have posed a hypothesis that point defects migration could be responsible for the InGaN QWs decomposition at high temperatures

Summary

Introduction

The aim of this paper is to give an experimental evidence that point defects (most probably gallium vacancies) induce decomposition of InGaN quantum wells (QWs) at high temperatures. InGaN has a large lattice mismatch to GaN: 10% between GaN and InN Those two factors cause a high defect density in InGaN layers: In-content fluctuations[1], high concentration of point d efects[2] and misfit dislocations for the layers above the critical thickness[3]. In order to check this hypothesis, we have performed the experiment consisting of three steps: (i) implantation of GaN:Si layer grown on sapphire template with He-ions to increase significantly the point defect concentration[10], (ii) growth of five-fold InGaN/GaN QWs on the unimplanted and implanted GaN layers at temperatures 730 °C—QWs and 810 °C—quantum barriers (QBs), (iii) annealing of these samples at temperatures 900 °C, 920 °C and 940 °C

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