Vertical profiling of ultrafast carrier dynamics in partially strain relaxed and strained InGaN grown on GaN/sapphire template of different In composition

Abstract

InGaN is one of the important ternary alloys which enables the nitrides to have bandgap energy in a wide range of 0.77-3.44 eV corresponding to the photon wavelength of 360-1610 nm by simply adjusting In content. However, the research on the InGaN has primarily focused on low-dimensional structures though knowledge of the physical properties of bulk InGaN thin-film is important in designing optoelectronic applications that utilize thick InGaN layers. In this study, we revisited partially strain relaxed bulk InGaN thin-films of different In compositions. We found that fast carrier decay was caused by hot carrier cooling due to the presence of oxygen impurity, and the slow carrier decay was governed by the carrier localization initiated by V-shape defects which concentrated at the bottom of the InGaN layer starting at InGaN/GaN interface. We also observed that the V-shape defects became severe, and the slow decay carrier lifetime decreased as In composition of the InGaN layer increased. Our observation gives guidance in designing optoelectronic applications using partially relaxed thick InGaN layers, such as buffer layers for long-wavelength InGaN light emitting diodes as well as solar absorber layer for InGaN photovoltaic cells.