Power density dependent photoluminescence spectroscopy and Raman mapping of semi-polar and polar InGaN/GaN multiple quantum well samples

We present a study of polar and semi-polar InGaN/GaN multiple quantum well (MQW) samples. Power density dependent photoluminescence (PL) was conducted on the samples. The polar sample exhibited a large blue shift of 65 nm in the peak PL from low to high power density compared to 10 nm for the semi polar sample. The semi-polar sample displayed "chevron" shaped surface features. These chevrons were mapped using micro-PL spectroscopy and showed a red shift of 10 nm at the "join" of the chevron. Raman mapping of the chevron also showed an increase in amplitude of the Raman shift in this area. Angle dependent polarised Raman measurements were conducted on the semi-polar sample to potentially isolate the scattering from the InGaN layers. However, polarised mapping exhibited similar behaviour to the unpolarised maps at the chevron join, indicating that the GaN bulk layer is responsible for the observed scattering. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim