Carbon as an acceptor in cubic GaN/3C–SiC

Abstract

We report on carbon doping of cubic GaN by CBr4 using plasma-assisted molecular beam epitaxy. Cubic GaN:C samples were doped at different CBr4 beam equivalent pressures between 2×10−9 and 6×10−6mbar. The incorporated carbon concentration of up to 1×1020cm−3 was achieved in c-GaN:C as measured by secondary ion mass spectroscopy. The net donor/acceptor concentration was obtained by evaluation of capacitance-voltage data. Capacitance-voltage measurements on nominally undoped cubic GaN showed n-type conductivity. With an increase in CBr4 flux the conductivity type changed to p-type and for highest CBr4 flux an acceptor surplus of 1×1019cm−3 was obtained. The electrical properties of the c-GaN:C layers were investigated by current–voltage measurements and a decrease in the serial conductance by two orders of magnitude was demonstrated in c-GaN:C. A blue shift of the 2K donor–acceptor pair luminescence with an increase in carbon concentration was obtained.