Structure and strain variation in InGaN interlayers grown by PAMBE at low substrate temperatures

Abstract

We have considered the structural properties of InGaN thin interlayers with thicknesses from 1 up to 40nm, grown by plasma assisted molecular beam epitaxy (PAMBE) at substrate temperatures ∼500°C. Quantitative high resolution transmission electron microscopy (HRTEM) techniques were employed for the study of the structural characteristics and strain relaxation. Based on nanoscale strain measurements, it was determined that the indium content of the layers increased with increasing thickness under identical growth conditions. Layer thickness was larger than nominal up to the onset of strain relaxation. This behavior, as well as the roughening of the upper interface of the layers, was attributed to indium segregation. After the onset of plastic strain relaxation, indium incorporation increases at a slower rate with thickness. A multi-quantum well (MQW) heterostructure deposited at low temperature exhibited roughening of the InGaN layers and indium accumulation at troughs, concurrent with low defect content, resulting in improved carrier localization.