Effect of potential fluctuations on photoluminescence in Mg‐doped GaN

Abstract

A model is proposed to explain dependencies of the defect-related photoluminescence (PL) intensities on temperature and excitation intensity in Mg-doped p-type GaN layers. Typical PL spectrum in Mg-doped GaN is dominated by a blue luminescence (BL) band with a maximum at about 2.8–2.9 eV and an ultraviolet luminescence (UVL) band with a maximum at about 3.1–3.2 eV. The BL intensity increases linearly while the UVL band intensity increases with a square power with excitation intensity in selected samples. In the proposed model, which is based on the concept of giant long-range potential fluctuations in Mg-doped GaN, the UVL band dominates in the potential valleys where electrons bound to shallow donors tend to accumulate. In contrast, the BL band dominates in the potential hills where the equilibrium concentration of holes bound to the shallow acceptor is much higher. The effect of potential fluctuations explains also pequliarities of quenching of the UVL and BL bands with temperature. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)