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 qua ntum wells. We study quantum-statistical effects in the relaxational dynami cs 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 qua ntum-well excitons leads to nonexponential and density-dependent thermaliza tion. At low bath temperatures T-b-->0, the thermalization of quantum stati stically degenerate excitons effectively slows down and T(t)proportional to 1/ln t. We also analyze the optical decay of Bose-Einstein distributed exc itons in perfect quantum wells, and show how nonclassical statistics influe nces 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 intri nsic radiative lifetime of quasi-two-dimensional excitons. Kinetics of reso nant 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 o f statistically degenerate excitons. Numerical modeling of the thermalizati on and photoluminescence kinetics of quasi-two-dimensional excitons are giv en for GaAs/AlxGa1-xAs quantum wells. [S0163-1829(99)05507-1].