STOICHIOMETRY-DEPENDENT DEEP LEVELS IN UNDOPED P-TYPE AL0.38GA0.62AS GROWN BY LIQUID-PHASE EPITAXY

Photocapacitance (PHCAP) and photoluminescence (PL) measurements were applied to unintentionally doped p-type Al0.38Ga0.62As grown by liquid phase epitaxy using the temperature difference method under controlle d vapor pressure. PHCAP spectra revealed three dominant deep levels at E-v + 0.9, E-v + 1.45, and E-v + 1.96 eV, and a deep level at E-v + 0 .9-1.5 eV which was not neutralized by forward bias injection. These l evel densities increase with increasing arsenic vapor pressure and net shallow acceptor density. Furthermore, PL spectra reveal a deep level at 1.6-1.7 eV. The PL intensity of this deep level increases with inc reasing arsenic vapor pressure. These deep levels are thought to be as sociated with excess As.