Polarization field crossover in semi‐polar InGaN/GaN single quantum wells

Abstract

Abstract We present an electroreflectance study of the polarization field in semi‐polar (10 $ \bar 1\bar 1 $ ) and (11 $ \bar 2 $ 2) oriented InGaN quantum wells (QW). For the ( $ \bar 1\bar 1 $ ) sample, the flat‐QW condition (the electric field in the QW is zero) is at a reverse bias voltage. For the (11 $ \bar 2 $ 2) sample, the flat‐QW condition is at a forward bias voltage larger than the turn on voltage of the diode. However, the flat‐barrier condition (the electric field in the barrier region is zero) is at a forward bias voltage less than the turn on voltage of the diode. The flat‐QW condition and the flat‐barrier condition are determined by examining the zero‐crossing and the Franz‐Keldysh oscillations in the electroreflectance signal for (10 $ \bar 1\bar 1 $ ) and (11 $ \bar 2 $ 2) InGaN QWs, respectively. From the corresponding bias voltages, we deduce the polarization field in the QWs and conclude that in the semi‐polar InGaN/GaN QW there is a crossover angle between the polar and non‐polar orientations where the polarization field vanishes. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)