Incorporation and optical properties of magnesium in cubic GaN epilayers grown by molecular beam epitaxy

The incorporation and optical properties of Mg in cubic GaN (c-GaN) epilayers grown by rf plasma-assisted molecular beam epitaxy on (100) GaAs are investigated by secondary ion mass spectroscopy and low-temperature photoluminescence (PL). By varying the Mg flux by more than four orders of magnitude, the incorporation of Mg saturates at high Mg flux and is limited to a value of about 5X10(18) cm(-3) due to the high volatility of Mg at growth temperature. In addition, we observe an accumulation of Mg at the GaN/GaAs interface due to a diffusion of Mg to the GaAs substrate. Low-temperature PL spectra reveal several well-separated lines. Besides a shallow acceptor level at E(A)congruent to 0.230 eV, additional Mg-related deep defect levels indicate an incorporation of Mg at off-gallium sites or as complexes. (C) 1998 American Institute of Physics. [S0003-6951(98)00239-3].