Effects of alloy potential fluctuations in InGaN epitaxial films

Abstract

Results of photoluminescence and photoconductivity measurements in In x Ga 1−x N epitaxial films are presented. The photoluminescence peak energy and intensity show several anomalous behaviours. The peak energy changes with temperature exhibiting an inverted S-shape dependence, where it decreases, then increases with increasing temperature in the range 40-100 K and finally decreases with increasing temperature. The intensity shows a temperature dependence similar to that of amorphous semiconductors and disordered superlattices. A blue shift of the photoluminescence energy with increasing excitation intensity is observed. A large Stokes shift between the photoluminescence peak position and the band edge transition energy is found; it decreases with decreasing indium content. A persistent photoconductivity effect has been detected up to room temperature with a stretched-exponential function for its decay rate. All these observations can be explained in a consistent way by alloy potential fluctuations, and these clearly indicate the existence of compositional fluctuations. These two related effects thus appear to constitute the mechanism for the widely observed localized excitons in InGaN-based devices.

Non-Exponential Photoionization of the DX Centers in Gallium Doped CdTe and Cd0.99Mn0.01Te

“…The photoionization of such a state proceeds in two steps resulting in the non-exponential kinetics of photoconductivity growth [2][3][4][5][6][7][8]. In consequence, the kinetics are modelled with formula…”

Absence of local-potential fluctuation effects in Si-doped InxGa1−xN epilayers studied by optical characterizations

“…The increase of In content clearly shows the aggravation of the S-shaped behavior of PL peak energy. According to Lin et al [5], the recombination of electron-hole (e-h) pair is considered to occurs around the localized states. The e-h recombination pair increases with In content in In x Ga 1Àx N epilayers due to strong alloy potential fluctuations.…”

“…In particular, room temperature photoluminescence (PL) emission from Si-doped In x Ga 1Àx N epilayers was found to be much stronger than that of undoped In x Ga 1Àx N epilayers. The influence of doping on the optical and structural characteristics of In x Ga 1Àx N/GaN heterostructures (HS) and In x Ga 1Àx N/GaN multi-quantum wells (MQWs) has been examined by many researchers using optical absorption (OA), PL, photoluminescence excitation (PLE) and X-ray diffraction (XRD) measurements [4,5]. In In x Ga 1Àx N/GaN MQWs, the effects of Si doping in the GaN barriers have been reported [6,7].…”

Time Resolved Optical Studies of InGaN Layers Grown on LGO

“…This is most likely caused by the alloy fluctuation in these samples. Previous studies [14] of PL lifetime have shown that the stretched exponential decay model [15,16] can offer insight into the recombination mechanisms in InGaN-related structures. According to this model the PL intensity decay is described by the following expression:…”