We report p-type behavior for undoped GaN 1-x Sb x alloys with x ! 0.06 grown by molecular beam epitaxy at low temperatures (400 C). Rapid thermal annealing of the GaN 1-x Sb x films at temperatures >400 C is shown to generate hole concentrations greater than 10 19 cm À3 , an order of magnitude higher than typical p-type GaN achieved by Mg doping. The p-type conductivity is attributed to a large upward shift of the valence band edge resulting from the band anticrossing interaction between localized Sb levels and extended states of the host matrix.

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