Impact of elemental arsenic on electrical characteristicsof metal-oxide-semiconductor capacitors on GaAs using atomic-layer deposited Hf O 2 gate dielectric

The interface between Hf O 2 and sulfur-passivated GaAs was analyzed after atomic-layer deposition (ALD) and postdeposition annealing (PDA) using x-ray photoelectron spectroscopy. The Hf O 2 ALD process resulted in elemental arsenic buildup at the interface. Electrical measurements confirmed that the elemental arsenic caused anomalously large values for equivalent oxide thickness (EOT), hysteresis, and frequency dispersion in accumulation. Arsenic outdiffusion after PDA lowered the EOT but increased the gate leakage. Annealing the ( N H 4 ) 2 S -treated GaAs prior to ALD yielded an EOT of 1.85 nm and leakage of 6.6 × 10 − 4 A ∕ cm 2 at V g = V f b − 1 V . This modified passivation scheme looks promising for achieving a high-quality Hf O 2 ∕ Ga As interface.