Evidence for Phosphorus Passivation of Plasma-Induced Damage at GaAs Surface Probed by EL2 Traps

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Abstract
Change in EL2 density in the GaAs surface layer treated with H2 plasma and phosphine (PH3)-added H2 plasma has been investigated by means of deep level transient spectroscopy (DLTS) and isothermal capacitance transient spectroscopy (ICTS). Apparent reduction in the EL2 density occurs on the H2-plasma-treated GaAs surface in comparison with that on the untreated one, because of H passivation of EL2 centers. However, an annealing at 350°C for 3 min after the H2-plasma exposure leads to a remarkable increase of EL2 density on the surface, showing net introduction of EL2 centers during the plasma exposure. On the other hand, the generation of EL2 centers is suppressed when the surface is treated with the PH3-added plasma.