Bose-Einstein statistics in thermalization and photoluminescence of quantum-well excitons

Quasiequilibrium relaxational thermodynamics is developed to understand LA-phonon-assisted thermalization of Bose-Einstein distributed excitons in quantum wells. We study quantum-statistical effects in the relaxational dynamics of the effective temperature of excitons T=T(t). When T is less than the degeneracy temperature T-0, well-developed Bose-Einstein statistics of quantum-well excitons leads to nonexponential and density-dependent thermalization. At low bath temperatures T-b-->0, the thermalization of quantum statistically degenerate excitons effectively slows down and T(t)proportional to 1/ln t. We also analyze the optical decay of Bose-Einstein distributed excitons in perfect quantum wells, and show how nonclassical statistics influences the effective lifetime tau(opt). In particular, tau(opt) of a strongly degenerate gas of excitons is given by 2 tau(R), where tau(R) is the intrinsic radiative lifetime of quasi-two-dimensional excitons. Kinetics of resonant photoluminescence of quantum-well excitons during their thermalization is studied within the thermodynamic approach and taking into account Bose-Einstein statistics. We find density-dependent photoluminescence dynamics of statistically degenerate excitons. Numerical modeling of the thermalization and photoluminescence kinetics of quasi-two-dimensional excitons are given for GaAs/AlxGa1-xAs quantum wells. [S0163-1829(99)05507-1].