Effects of InGaN quantum disk thickness on the optical properties of GaN nanowires

Abstract

The impact of InGaN quantum disk (Qdisk) thickness on the optical emission properties of axial InGaN/GaN nanowires is experimentally studied. The luminescence of InGaN/GaN nanowire heterostructures grown by plasma assisted molecular beam epitaxy were measured using a combination of photoluminescence and cathodoluminescence spectroscopy. The variation of peak emission wavelength, spectral lineshape, width, and maximum intensity with the change of Qdisk thickness over the range of 4–12 nm was systematically analyzed. Both the spectroscopic measurements from the average InGaN Qdisk-related emissions reveal the presence of built-in piezoelectric strain as evidenced by the luminescence blueshift with increasing pump signal. To determine the material compositions and their spatial uniformity across the stacked InGaN Qdisks separated by GaN barriers, transmission electron microscopy with energy-dispersive x-ray spectroscopy were also performed. This provides further insights into the structural properties of the InGaN Qdisks within GaN nanowires. Thus, our experimental study serves to advance the understanding of, in general, III-nitride nanostructures for the implementation of classical and non-classical optoelectronic devices.