Silicon nitride (NH4)(2)S-x passivation of n-GaAs to unpin the Fermi level

Silicon nitride is deposited by the direct plasma enhanced chemical vapour deposition (PECVD) technique at a low power on an it-type GaAs sample treated with (NH4)(2)S-x. Metal-insulator-semiconductor (MIS) structures are fabricated on this sample and annealed at 450 degrees C in nitrogen for 5 min. The 1 MHz capacitance-voltage (C-V) characteristics of these devices demonstrate accumulation, depletion and inversion regions. The interface State density (D-it) estimated from the 1 MHz C-V curve using the high frequency method has shown that the minimum D-it achieved is similar to 4 x 10(11)cm(-2)eV(-1).