Extrinsic p-type doping and analysis of HgCdTe grown by molecular beam epitaxy

Abstract

We have carried out basic research on the extrinsic p-type doping of mercury cadmium telluride epilayers grown by molecular beam epitaxy. The doping is performed with elemental arsenic and gold sources. HgCdTe epilayers of CdTe mole fraction in the range of the long-wavelength and mid-wavelength infrared were grown on (211)B CdTe/Si and CdZnTe substrates. The van der Pauw technique was utilized to study the temperature dependent Hall effect characteristics of the grown epilayers and the photoconductive decay method was used to obtain minority carrier lifetime data. Activation annealing of As at different temperatures was performed. P-type conversion of As doped samples at lower than conventional annealing temperatures was achieved. The influence of the annealing conditions on the Hall effect characteristics of the grown epilayers were studied. As activation in HgCdTe is also studied in the annealing experiments and compared to the current As activation models. We studied the surface and the bulk properties of our p-type doped samples by minority carrier lifetime measurements. Gold doping was achieved by deposition of Au on and its diffusion into samples. We also investigated the effects of vacancies on the mobility of Au dopants in the HgTe lattice by ab-initio pseudo-potential methods. For this study, we first determined the smallest supercell that will produce reliable results. Then total energy calculations were performed on supercells with nearest neighbor, 2 nd nearest neighbor, 3 rd nearest neighbor, etc. vacancies relative to Au sites.