Silicon nitride/(NH<inf>4</inf>)<inf>2</inf>S<inf>x</inf> 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 n-type GaAs sample treated with (NH4)2Sx. Metal-insulator-semiconductor (MIS) structures are fabricated on this sample and annealed at 450°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 (Dit) estimated from the 1 MHz C-V curve using the high frequency method has shown that the minimum Dit achieved is ∼4 × 1011cm-2eV-1.