Investigation of the photoluminescence-linewidth broadening in periodic multiple narrow asymmetric coupled quantum wells

Abstract

Photoluminescence spectra were measured as a function of temperature and excitation intensity in two periodic multiple narrow asymmetric coupled quantum-well structures. The peaks of the spectra have been identified and the temperature-dependent natures of the recombination processes have been determined. The half-widths at half maximum of the line shapes were deduced by fitting the low-energy sides to Gaussian functions. The excellent fits indicate that inhomogeneous broadening is dominant. The rate at which the linewidth broadens with temperature is more dramatic below 140 K due to the sharp changes of the ionized impurity and of the longitudinal-optical-phonon scattering mechanisms. Above 140 K, the linewidth has a linear dependence on temperature due to the thermal excitation of the longitudinal optical phonons. By using the model proposed by Lee et al. we have determined the scattering rates of the longitudinal acoustic and optical phonons, of the impurities, and of the inhomogeneous broadening. Our results show that unless the growth is interrupted at each interface, the inhomogeneous broadening remains dominant up to room temperature. Measurement of the temperature dependence of the photoluminescence linewidth proves to be a simple and effective technique to investigate the scattering mechanisms of the photogenerated carriers and the origins of the emission peak's linewidth broadening in these structures.