Depletion-mode InGaAs metal-oxide-semiconductor field-effect transistor with oxide gate dielectric grown by atomic-layer deposition

Abstract

Recently, significant progress has been made on GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using atomic-layer deposition (ALD)-grown ${\mathrm{Al}}_2{\mathrm{O}}_3$ as gate dielectric. We show here that further improvement can be achieved by inserting a thin ${\mathrm{In}}_{\text{0.2}}{\mathrm{Ga}}_{\text{0.8}}\mathrm{As}$ layer as part of the channel between ${\mathrm{Al}}_2{\mathrm{O}}_3$ and GaAs channel. A 1-μm-gate-length, depletion-mode, n-channel ${\mathrm{In}}_{\text{0.2}}{\mathrm{Ga}}_{\text{0.8}}\mathrm{As/GaAs}$ MOSFET with an ${\mathrm{Al}}_2{\mathrm{O}}_3$ gate oxide of 160 Å shows a gate leakage current density less than ${10}^{\text{−4}}\hspace{0.17em}{\mathrm{A/cm}}^2,$ a maximum transconductance ∼105 mS/mm, and a strong accumulation current at $V_{\mathrm{gs}}\text{>0}$ in addition to buried-channel conduction. Together with longer gate-length devices, we deduce electron accumulation surface mobility for ${\mathrm{In}}_{\text{0.2}}{\mathrm{Ga}}_{\text{0.8}}\mathrm{As}$ as high as 660 cm²/V s at ${\mathrm{Al}}_2{\mathrm{O}}_3/{\mathrm{In}}_{\text{0.2}}{\mathrm{Ga}}_{\text{0.8}}\mathrm{As}$ interface.