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

Recently, significant progress has been made on GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using atomic-layer deposition (ALD)-grown Al2O3 as gate dielectric. We show here that further improvement can be achieved by inserting a thin In0.2Ga0.8As layer as part of the channel between Al2O3 and GaAs channel. A 1-mum-gate-length, depletion-mode, n-channel In0.2Ga0.8As/GaAs MOSFET with an Al2O3 gate oxide of 160 A shows a gate leakage current density less than 10(-4) A/cm(2), a maximum transconductance similar to105 mS/mm, and a strong accumulation current at V-gs>0 in addition to buried-channel conduction. Together with longer gate-length devices, we deduce electron accumulation surface mobility for In0.2Ga0.8As as high as 660 cm2/V s at Al2O3/In0.2Ga0.8As interface. (C) 2004 American Institute of Physics.