Study on the influence of variable temperature growth on the properties of highly strained InGaAs/GaAs MQWs grown by MOCVD

Abstract

The InGaAs/GaAs multiple quantum wells (MQWs) have played an important role in the epitaxial structure of semiconductor laser, solar cell, detector and so on. However, the preparation of high-quality InGaAs/GaAs MQWs with high indium content has always been a research problem. In this paper, five periods InGaAs/GaAs MQWs were obtained with two methods by metal-organic chemical vapor deposition (MOCVD): constant and variable temperature growth methods, respectively. Our systematic theoretical and experimental studies indicated that there were wedding cake-like stacked steps on the surface of constant temperature sample, revealing an inhomogeneous distribution of layer thickness and indium content. Such interface fluctuations were manifested as two peaks in the photoluminescence (PL) spectra at low temperature, which were confirmed by theoretical fitting as the localized states emission (LE) peak and the free-carrier emission (FE) peak, respectively. For variable temperature sample, the change in the growth temperature of the barrier and well layers in each period could transform the morphology to a step-flow-mode surface, thus eliminating the localized states in MQWs. It could be seen that the variable temperature growth method was superior to the constant temperature method, the surface morphology, optical characteristics and crystal quality were all improved. This study will provide technical support for optimizing the device performance of InGaAs/GaAs MQWs with high indium content.