NATIVE DEFECTS IN GALLIUM-ARSENIDE GROWN BY MOLECULAR-BEAM EPITAXY AND METALLORGANIC CHEMICAL-VAPOR-DEPOSITION - EFFECTS OF IRRADIATION

Gallium arsenide (GaAs), doped n with silicon nominally to 10(15) and 10(16) cm(-3), grown by molecular beam epitaxy (MBE) and by metallorga nic chemical vapour deposition (MOCVD), was characterized by photolumi nescence (PL) spectroscopy. In MOCVD GaAs, we found the signature of t he arsenic antisite (As-Ga) at 0.702 eV, but in MBE GaAs we found the signature of the gallium antisite (Ga-As) at 1.441 eV as well as silic on at the arsenic site (Si-As) at 1.483 eV. We used proton (0.6-10 MeV ) irradiation to increase the number of intrinsic defects. The fluence range was 10(10) to 10(13) cm(-2) for MOCVD GaAs, and 10(10) to 10(14 ) cm(-2) for MBE GaAs. At low fluences, the effect of irradiation was to reduce the PL intensity, which became 10% at 10(11) cm(-2) in MOCVD GaAs, and 10% at 10(12) cm(-2) in MBE GaAs. Annealing the samples to 550 degrees C for 30 min resulted in the total recovery of the PL inte nsity for MBE GaAs, but only a 70% recovery in MOCVD GaAs even at thes e low fluences. The signature of gallium vacancies (V-Ga) appeared onl y in the irradiated MOCVD samples, at a fluence of 10(11) cm(-2) and h igher, but never in the MBE samples. We conclude that MOCVD GaAs was g rown under arsenic rich conditions but MBE GaAs under gallium rich con ditions. MBE material is about ten times more resistant to radiation t han MOCVD GaAs. The presence of V-Ga in this material may limit the op tical output of devices depending on electron-hole recombination. In t he case of as-grown MBE GaAs, the presence of Si-As and Ga-As lowers t he electron-hole recombination efficiency.