Native defects in gallium arsenide grown by molecular beam epitaxy and metallorganic chemical vapour deposition: effects of irradiation

Gallium arsenide (GaAs), doped n with silicon nominally to 1015 and 1016 cm−3, grown by molecular beam epitaxy (MBE) and by metallorganic chemical vapour deposition (MOCVD), was characterized by photoluminescence (PL) spectroscopy. In MOCVD GaAs, we found the signature of the arsenic antisite (AsGa) at 0.702 eV, but in MBE GaAs we found the signature of the gallium antisite (GaAs) at 1.441 eV as well as silicon at the arsenic site (SiAs) at 1.483 eV. We used proton (0.6–10 MeV) irradiation to increase the number of intrinsic defects. The fluence range was 1010 to 1013 cm−2 for MOCVD GaAs, and 1010 to 1014 cm−2 for MBE GaAs. At low fluences, the effect of irradiation was to reduce the PL intensity, which became 10% at 1011 cm−2 in MOCVD GaAs, and 10% at 1012 cm−2 in MBE GaAs. Annealing the samples to 550 °C for 30 min resulted in the total recovery of the PL intensity for MBE GaAs, but only a 70% recovery in MOCVD GaAs even at these low fluences. The signature of gallium vacancies (VGa) appeared only in the irradiated MOCVD samples, at a fluence of 1011 cm−2 and higher, but never in the MBE samples. We conclude that MOCVD GaAs was grown under arsenic rich conditions but MBE GaAs under gallium rich conditions. MBE material is about ten times more resistant to radiation than MOCVD GaAs. The presence of VGa in this material may limit the optical output of devices depending on electron-hole recombination. In the case of as-grown MBE GaAs, the presence of SiAs and GaAs lowers the electron-hole recombination efficiency.