Broad photoluminescence band in undoped AlxGa1-xAs grown by organometallic vapor phase epitaxy

We have studied the 77 K photoluminescence (PL) of undoped-AlxGa1-xAs (0.21 less than or equal to x less than or equal to 0.83) grown by organometallic vapor phase epitaxy. A deep broad (DB) PL band is found at 1.6-1.7 eV at a range of x from 0.21 to 0.63, with a maximum intensity at around x = 0.5. Its large full width at half-maximum (similar to 200 meV) suggests that this emission originates from some impurity-defect complex. The Si- and C-doping dependencies of the PL reveal that the emission disappears in Si-doped n-type samples while it increases in intensity superlinearly with the hole concentration, thus, the emission center is C acceptor related. Furthermore, annealing Al0.52Ga0.48As samples in H-2 flow eliminates the emission, while annealing in AsH3 flow increases the emission. Based on these results, we have considered the doping and V/III dependencies of various major point defects present in p-type GaAs and those of the combinations of the C acceptor and these defects. It is concluded that the DB band originates from the substitutional C-As antisite complex (C-As-As-Ga). Mass-action rule analysis of the complex deduces a quadratic increase in the PL intensity with hole concentration, which generally explains the experimental results. (C) 1997 American Institute of Physics.