TEMPERATURE-DEPENDENCE OF THE EXCITONIC TRANSITIONS IN GAAS-GAALAS SUPERLATTICES UNDER A WEAK ELECTRIC-FIELD

The temperature variations (between 9 and 80 K) of the ratio rho = I-1/I0 of the intensities of the -1 and 0 peaks of the Wannier-Stark ladder in a GaAs-Ga0.65Al0.35As superlattice under an electric field are interpreted. The model is based on the thermal equilibrium between the two populations of excitons. The filling rate of every excitonic levels is given by the Maxwell-Boltzmann distribution function. A discrepancy appears at low temperatures (T < 50 K); the excitons are trapped into the direct state rather than in the crossed one, showing that the equilibrium statistics are not respected.