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) ep ilayers grown by rf plasma-assisted molecular beam epitaxy on (100) Ga As are investigated by secondary ion mass spectroscopy and low-tempera ture 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 vo latility of Mg at growth temperature. In addition, we observe an accum ulation of Mg at the GaN/GaAs interface due to a diffusion of Mg to th e GaAs substrate. Low-temperature PL spectra reveal several well-separ ated lines. Besides a shallow acceptor level at E(A)congruent to 0.230 eV, additional Mg-related deep defect levels indicate an incorporatio n of Mg at off-gallium sites or as complexes. (C) 1998 American Instit ute of Physics. [S0003-6951(98)00239-3].