The effect of interface processing on the distribution of interfacial defect states and the C-V characteristics of Ill-V metal-oxide-semiconductor field effect transistors

摘要

We have investigated the effect of interface formation and processing conditions of A1_2O_3 on GaAs on the density and distribution of interface state charge in the band gap. We have formed the insulator/semiconductor interface using both atomic layer deposition (ALD) and chemical vapor deposition (CVD). In situ ALD, ex situ ALD, and in situ CVD of aluminum oxide (A1_2O_3) on GaAs were employed using metal-organic CVD. Isopropanol (IPA) was chosen as the oxygen source for A1_2O_3 deposition. No arsenic or gallium oxide was detected at the in situ ALD Al_2O_3/GaAs interface, while gallium oxide was observed at the in situ CVD Al_2O_3/GaAs interface. The entire distributions of interfacial defects from different processes were determined by conductance frequency method with temperature-variation capacitance-voltage (C-V) measurements. The existence of Ga_2O_3 at the interface was found to be a possible method to lower the density of midgap defect states. From the C-V simulation, the midgap defect states are acceptorlike, which may originate from gallium vacancies near the interface. These states may also result in high frequency dispersion observed in the C-V curves of n-type metal-oxide-semiconductor field effect transistors. We correlate the interfacial defect states with the processes used to form the insulator-semiconductor interface.