Enhancement-Mode N-Polar GaN MISFETs With Self-Aligned Source/Drain Regrowth

Abstract

We report gate-first enhancement-mode (E-mode) N-polar GaN MISFET devices with self-aligned source/drain regions by molecular beam epitaxy regrowth and with a SiN <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> gate dielectric. E-mode operation at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> = 4.0 V is demonstrated for devices with gate lengths >; 0.18 μm with a 20-nm GaN channel and a high-temperature SiN <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> gate dielectric. A high drain current of 0.74 A/mm was measured for an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Lg</i> = 0.62-μm device with a peak transconductance of 225 mS/mm and a positive threshold voltage of 1 V. The on resistance of the device was 2 Ω·mm. Devices show short-channel effect with decreasing gate lengths.