Time‐resolved photoluminescence and steady‐state optical studies of GaInNAs and GaInAs single quantum wells

Abstract

Time-resolved photoluminescence spectroscopy is used to investigate carrier dynamics of Ga 1-x In x N y As 1-y (x ~ 0.33, y ~ 0.01) single quantum well (QW) structures. PL spectra measured as a function of temperature together with the PL decay times at wavelengths around and below the PL peak energy are used to determine de-trapping activation energies and time constants. The results are interpreted in terms of simultaneous thermal excitation of deep localized excitons to shallow localized states. According to the model, with increasing temperatures, localized excitons gain enough thermal energy to populate the free exciton states in quantum well with shorter lifetimes due to coherent nature of free excitons. In addition, at temperatures around and above 80 K, more non-radiative channels become available to compete with the radiative processes leading to shorter time constants. 1 Introduction Dilute nitride alloys (GaAsN, InGaAsN and GaAsSbN) have recently attracted considerable attention as promising materials for long wavelength laser diodes as well as high efficient multijunction solar cells. The incorporation of a low content of nitrogen (< 2%) in the host material induces dramatic changes in the optical and electronic properties [1][2][3]. However, the compositional nonuniformity of nitrogen and indium induces a spatial distribution of different sized clusters hence to the associated states [4,5]. These cluster states reflect potential fluctuations that are inherent in the disordered systems resulting in the creation of intrinsic regions of strong localization. Strongly localized states dominate radiative recombination dynamics at low temperatures. In this contribution, we report on the time resolved photoluminescence (TRPL) studies of sequentially grown GaInNAs/GaAs and GaInAs/GaAs single quantum wells. We interpret our results in terms of localized excitons in nitrogen containing quantum well but free exciton recombination in nitrogen free well.