DOES THE LOW-TEMPERATURE ARRHENIUS PLOT OF THE PHOTOLUMINESCENCE INTENSITY IN CDTE POINT TOWARDS AN ERRONEOUS ACTIVATION-ENERGY

Several experimental photoluminescence (PL) bands of different energie s for variously prepared CdTe samples are compared. Temperature variat ion of the PL intensity is modeled with two nonradiative thermal activ ation energies, of which E(T1) is dominant for about T less than or eq ual to 60 K, and E(T2) for the upper temperature range of the measurem ent. The size of E(T1) is invariably of the order of a few meV and, al though of unclear origin, its magnitude is usually interpreted as an e lectronic energy level difference over which the carriers escape by th ermal excitation. In CdTe the existence of such a small energy level d ifference E(T1) is not easy to explain. On the contrary, we find clear evidence that, at low temperature, the PL intensity reduction with in creasing temperature in fact results from the approximately T-2 temper ature dependent capture cross sections of the carriers at the recombin ation centers, and not from a genuine thermal activation energy E(T1). (C) 1997 American Institute of Physics.