Investigations of deep lying wide bandgap GaN and InGaN quantum well structures: A challenge for ellipsometric methods

Abstract

In this contribution we address the problems in characterizing typical group‐III‐nitride QW structures used in LED or laser applications by spectroscopic ellipsometry. Since the buffer layers are transparent in the visible and near UV and the whole layer stack is a few microns thick, the contributions of the nanometer thick QWs to the signal is very small and with ellipsometers with typical resolution in the polarization states hardly to detect. We discuss this in detail for two typical structures – Al‐GaN/GaN and InGaN/GaN – and quantify how the resolution must be improved to overcome this experimental limitation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)