Si- and Mg-doped GaN layers were grown onc-plane sapphire substrates by molecular beam epitaxy withNH3as the nitrogen precursor. Their optical and electrical properties were investigated by photoluminescence experiments and Hall measurements, respectively.P-type conductivity, with a net acceptor concentration of3×1017 cm−3and a mobility of 8cm2/V s, was obtained. Mesa-etched light-emitting diodes were processed fromp–njunctions. The turn-on voltage is 3 V and the forward current reaches 20 mA at 3.5 V. The room-temperature electroluminescence exhibits a strong emission at 390 nm. ©1998 American Institute of Physics.