Effect of Indium Composition on the Microstructural Properties and Performance of InGaN/GaN MQWs Solar Cells

Heng-Sheng Shan,Bin Chen,Shu-Fang Ma,Xiao-Ya Li,Bing-She Xu,Lu Li

doi:10.1109/access.2019.2959844

Abstract

In the present work, InGaN/GaN multiple quantum wells (MQWs) solar cells with different concentrations of indium have been investigated in-depth. It was demonstrated that applying a medium-high indium content (about 28%) does not facilitate solar cell photoelectric conversion efficiency due to the increase of edge dislocations. Moreover, the effects of different indium contents on InGaN/GaN MQWs solar cells were investigated and was revealed, that the short-circuit current density and photoelectric conversion efficiency are improved with the increase of indium contents. However, they show a noticeable reduction in the indium content of 28%. Furthermore, the optical properties and the behaviour of the microstructure defects were analysed. It was also demonstrated that the number of edge dislocations acted as non-radiation recombination centers increasing rapidly when the indium content reaches 28%, playing a key role in decreasing the active number of photon-generated carriers. As a result, the short-circuit current density and photoelectric conversion efficiency decrease obviously for an indium content of 28%. This work can provide insight into the origin of the degradation of these structures and the improvement of device design with medium-high indium contents.

Highlights

InGaN alloys as important semiconductors with appropriate direct bandgap have drawn increasing research interest in multi-junction solar cell, almost completely matching the solar spectrum [1], with an excellent absorption coefficient [2]
From the analysis described above, we can conclude that for the low indium contents from 7% to 18%, the multiple quantum wells (MQWs) are under complete stress state and high-quality epitaxial conditions indicated from the Reciprocal Space Mappings (RSMs) curves obtained from the XRD measurement
SUMMARY AND CONCLUSION The effect of indium contents on the optical and electrical characteristics of InGaN/GaN MQWs solar cells was investigated, and the behaviour of the InGaN microstructure was discussed in depth

Summary

INTRODUCTION

InGaN alloys as important semiconductors with appropriate direct bandgap have drawn increasing research interest in multi-junction solar cell, almost completely matching the solar spectrum [1], with an excellent absorption coefficient (an order of magnitude higher than in the case of GaN-based materials) [2]. The effect of the indium component on the performance of InGaN/GaN MQWs solar cells with indium components from 17% to 25% was investigated by Chio et al [19] They have reported that the influence of indium content on the short-circuit current density and fill factor is mainly caused by the competition between the tunnelling effect of the carriers and the recombination rate. In 2017, Liu et al investigated the influence of indium component for InGaN/GaN MQWs solar cells with indium concentration of 15.4%, 19.5%, and 21.4% [20] They have found that the unintentional background doping is higher with the increase of the indium content, reducing in this way the performance of the main device. Photoluminescence (PL) spectra, Reciprocal Space Mappings (RSMs), transmission electron microscopy (TEM) micrographs, and transmittance curves are measured and analysed to reveal the direct reason of solar cell degradation with medium-high indium components

DEVICE FABRICATION AND MEASUREMENT

Findings

DISCUSSION AND ANALYSIS

SUMMARY AND CONCLUSION