Electrical and material characterization of sulfur-implanted GaSb

Abstract

Ion implantation has been studied relatively little as a nonepitaxial doping method for GaSb due in part to anomalous swelling that occurs at high doses. Aside from beryllium (Be+), there has been little success in identifying other ions as an implant species to dope a GaSb substrate p-type. In this paper, the role of sulfur (S+) as an implant species is investigated for doping GaSb and compared to Be+. Whereas the Be+ implant yields modest hole concentrations as a result of incomplete dopant activation, the S+ implant at a similar dose level realizes p-type carrier concentrations above 1 × 1019 cm−3 with sheet densities as high as 3.5 times the total implanted dose. X-ray diffraction spectroscopy shows that a postimplant anneal at 600 °C successfully recovers the crystallinity of the material, but atomic force microscopy suggests that surface damage may be the cause of the high carrier concentration from the sulfur implant. Preliminary photovoltaic data are reported for a device that employs the sulfur implant technique into a p-type GaSb substrate.