Correlation between transient decays in wide gap semiconductors: Photoluminescence vs. photocurrent

Abstract

Recently, we introduced the Thermalization–Recombination (TR) Model to explain the ubiquitous broad subgap photoluminescence bands in wide bandgap semiconductors [M. Niehus, R. Schwarz, Phys. Status Solidi C 3 (2006) 1637]. The model describes the competition between the thermalization and recombination dynamics of excess carriers trapped in localized states distributed exponentially in energy. In this contribution, we confronted the theoretical and qualitative predictions of the TR Model with experimental results of transient photoluminescence (TPL) of pulsed laser deposited (PLD) polycrystalline gallium nitride (GaN) and polycrystalline zinc oxide (ZnO). The TPL results are compared with transient photocurrent (TPC) measurements in order to highlight the relation between TPL and TPC, as well as similarities in the relaxation dynamics of GaN and ZnO. The general features of the transient decays for both materials can be explained within the framework of the TR model, which is shown to offer significant inside into the relaxation dynamics of wide gap semiconductor materials .