Increased Mobility in Enhancement Mode 4H-SiC MOSFET Using a Thin SiO₂/ Al₂O₃Gate Stack

A field effect mobility of 125 cm <tex-math notation="LaTeX">²/V· s </tex-math> and a subthreshold slope of 130 mV/dec were obtained in enhancement mode 4H-SiC MOSFETs with a channel length of <tex-math notation="LaTeX">2~μ m </tex-math> . The fabricated devices utilized a gate stack comprising a 0.7 nm thin thermal SiO 2 , thereby reducing defects following oxidation, and a 40 nm thick Al 2 O 3 formed by atomic layer deposition. A high mobility was maintained over a wide gate voltage range and resulted in increases of up to <tex-math notation="LaTeX">120× </tex-math> in drain current for the same gate overdrive voltage compared to MOSFETs having a thicker thermal SiO 2 gate stack with the same effective oxide thickness fabricated alongside. Nitridation is not included in either MOSFET process.