InGaAsP n-channel inversion-mode metal-insulator-semiconductor field-effect transistor with low interface state density

Abstract

n‐channel inversion‐mode metal‐insulator‐semiconductor field‐effect transistors (MISFET’s) were fabricated on In_1−xGa_xAs_yP_1−y quaternary alloy (y≃2.2x) with chemical vapor deposition (CVD) Al₂O₃ gate insulator. The InGaAsP MISFET exhibited compositional dependence of the effective mobility μ_eff. μ_eff monotonically increased with increasing As molar fraction y in the 0⩽y⩽0.55 experimental range. The highest mobility obtained so far was 2300 cm²/V s at room temperature, higher than that of InP MISFET devices fabricated in this laboratory (400–800 cm²/V s). Very large temperature variation in threshold voltage and zero temperature coefficient of μ_eff were observed on InP(y = 0) devices. Contrasting to this, small temperature variation in the threshold voltage and the clear dependence of μ_eff on temperature, similar to that of the bulk mobility, were seen on InGaAsP MISFET’s. These excellent characteristics of the quaternary device appeared to be brought about through reduction in the interface states near the conduction band edge. The interface state density was estimated to be 1×10¹²/cm²eV, as compared to 1×10¹³ at the InP interface. A simple analysis, including the effect of the interface state on MISFET characteristics, explained the experimental results with good consistency.