Luminescence studies of HgCdTe alloys

Abstract

We report the observation in Hg_(1-x)Cd_(x)Te of band-to-band, band-to-acceptor, and donor-acceptor luminescence for material of x = 0.32 and 0.5, and bound exciton recombination luminescence, for material of x = 0.5. The band-to-band lineshape and variation in intensity with pump power are appropriate to an electron-hole plasma with recombination proceeding without wave vector conservation. Differences between the spectra among the four 0. 5 samples studied are attributed to variations in the Hg vacancy concentration. Shifts in luminescence energy across one of the x = 0.32 samples imply a change in composition across the surface of the sample of 0.03 cm^(-1). The absence of bound exciton luminescence in the x = 0.32 samples is consistent with theoretical calculations by Osbourn and Smith showing a radiative efficiency of 20% for bound excitons in material of this composition and 90% for x = 0.48 material. From line shape separations, we estimate acceptor binding energies of 14.0 ± 1.0 and 15.5 ± 2.0 meV in x = 0.32 and 0.48 materials, respectively, and donor binding energies of 1.0 ± 1.0 and 4.5 ± 2.0 meV, respectively.