P-type carbon doping of GaSb

Abstract

The growth of carbon-doped GaSb by MOVPE has never been reported to our knowledge, despite increasing interest in carbon-doped GaAsSb alloys for heterojunction bipolar transistor applications. In this work, we report the use of carbon tetrachloride (CCl₄) in conjunction with triethylgallium (TEGa) and trimethylantimony (TMSb) to achieve p-type doping levels in GaSb from 5 10¹⁶ cm⁻³ to greater than 10¹⁹ cm⁻³. High resolution x-ray diffraction measurements confirm that the effect of carbon on the lattice parameter is significant for hole concentrations above 1 10¹⁹ cm⁻³ as in the case of GaAs. By introducing controlled low doping levels of carbon into thick homoepitaxial samples, we have succeeded in identifying a carbon-related low temperature photoluminescence band at 795 meV, which we ascribe to band-to-acceptor transitions of carbon acceptors. Temperature-dependent Hall measurements on lightly carbon-doped samples yield somewhat lower binding energies than the spectroscopic data due to impurity banding in the acceptor excited states.