Investigation on Photoluminescence Blue Shift of InGaN/GaN Quantum Wells Induced by Surface Band Bending

Abstract

The effects of GaN cap layer thickness and doping type on photoluminescence (PL) are investigated for InGaN/GaN quantum wells (QWs), which are deposited on a C-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). As for the results, the QWs capped with an unintentional doped (un-doped) GaN layer show a linear PL blue shift behavior with decreased cap layer thickness, while for the QWs capped with a heavy n- or p-doped GaN layer none of the similar behaviors are observed until the cap layer is less than 25 nm. These phenomena are well explained by introducing the effects of upward surface band bending. Surface polarization discontinuity and surface states are considered as the origins of the surface band bending. Furthermore, the actual surface band bending value of the un-doped GaN is also extracted as Eb = 1.54 ±0.08 eV from the linear PL blue shift behavior.