InGaAs/GaAs metal-oxide-semiconductor heterostructure field-effect transistors with oxygen-plasma oxide and Al₂O₃ double-layer insulator

Surface condition before an insulator deposition is the key issue for the preparation of reliable GaAs-based metal-oxide-semiconductor (MOS) devices. This study presents the preparation and properties of InGaAs/GaAs MOS structures with a double-layer insulator consisting of an oxygen-plasma oxide covered by Al₂O₃. The structures were oxidized during 75 s and 150 s. Static measurements yielded a saturation drain current of ∼250 mA/mm at V_G = 1 V. Capacitance measurements showed improved performance in the depletion region compared with the structures without the double-layer insulator. Trapping effects were investigated by conductance vs. frequency measurements. The trap state density was in order of 10¹¹cm⁻²·eV⁻¹ with a continuous decrease with increased trap energy. The carrier mobility evaluation showed peak values of 3950 cm²/V·s for 75 s and 4570 cm²/V·s for 150 s oxidation times with the sheet charge density ≅2 × 10¹²cm⁻². The results demonstrate great potential of the procedure that was used to prepare the GaAs-based MOS devices with oxidized GaAs surface covered with an Al₂O₃ insulator.