PREPARATION OF GASB BY MOLECULAR-BEAM EPITAXY AND ELECTRICAL AND PHOTOLUMINESCENCE CHARACTERIZATION

The molecular beam epitaxy and the characterization of high-quality, n on-intentionally doped and Te-doped GaSb are reported. The undoped lay ers have 77 K Hall hole concentrations p = 1-3 x 10(15) cm(-3) and mob ilities mu = 3000-5600 cm(2) V-1 s(-1), which compare favourably with the best results reported so far. Photoluminescence (PL) measurements at 70 K point to a relatively low concentration of intrinsic Ga-Sb ant isite defects, responsible for the p-type behaviour. A simultaneous fi t of mu and p was performed in the 40-300 K temperature range by using a model with two accepters, one of them having two charge states; the levels have energies consistent with those deduced by PL experiments. n-Doping was obtained approximately in the range 1 x 10(16)-1 x 10(18 ) cm(-3) by using Te from an SnTe source. The mobility values are defi nitely higher than those reported in the literature and obtained with the same source, and they slightly exceed those achieved in GaSb elope d using a GaTe Te source. A procedure for the analysis of electrical d ata has been set up and tested for n-GaSb with free carrier concentrat ions lower than a few 10(17) cm(-3).