PHOTOLUMINESCENCE OF N-TYPE CDTE-I GROWN BY MOLECULAR-BEAM EPITAXY

Liquid helium temperature and temperature-dependent photoluminescence (PL) spectroscopy have been performed on highly n-type-doped CdTe:I fi lms grown by molecular beam epitaxy. The samples were grown on 2-degre es off (001) oriented bulk CdTe substrates at substrate temperatures f rom 170 to 250-degrees-C, and exhibit room-temperature electron concen trations of 1 X 10(17) cm-3. The brightest PL edge emission at liquid helium and room temperatures was observed from a sample grown at 210-d egrees-C. At T = 5 K, the iodine donor radiative recombination was obs erved at 1.593 eV, corresponding to a donor ionization energy of 14 me V for the I(Te) substitutional donor, in agreement with the predicted hydrogenic donor ionization energy for CdTe. The thermal quenching beh avior of the edge emission peak is a two-step process involving both 1 0 and 14 meV activation energies. These activation energies are relate d to the thermalization of the I(Te) donor from the ground state to th e first excited state (1s --> 2s, 10 meV), and complete thermalization from the donor ground state to the conduction band (14 meV).