Arsenic incorporation in MBE grown Hg1-xCdxTe

The p-type doping of Hg1-xCdxTe (MCT) has proven to be a significant challe nge in present day MOT-based detector technology. One of the most promising acceptor candidates, arsenic, behaves as an amphoteric dopant which can be activated as an acceptor during Hg-rich, low temperature annealing of as-g rown molecular beam epitaxy (MBE) samples. This study focuses on developing an understanding of the microscopic behavior of arsenic incorporation duri ng MBE growth. In particular, the question of whether arsenic incorporates as individual As atoms, as As-2 dimers, or as As-4 tetramers is addressed f or MBE growth with an As, source. A quasithermodynamical model is employed to describe the MCT growth and As incorporation, with parameters fitted to an extensive database of samples grown at the Microphysics Laboratory. The best fits for growth temperatures between 175 and 185 degrees C are obtaine d for arsenic incorporation as As-4 or possibly as As, clusters, with lower probabilities for As-4 and individual As atoms. Based on these results, we investigate the relaxed atomic configurations of As-4 and As-2 in bulk HgT e by ab initio total energy calculations. The calculations are performed in the pseudopotential density-functional framework within the local density approximation, employing supercells with periodic boundary conditions. The lattice distortions due to As-4 and As-2 in bulk HgTe are predicted to be m odest due to the small size of these arsenic clusters.