Island-ohmic-PGaN Gate HEMT: Toward Steep Subthreshold Swing and Enhanced Threshold Stability

Abstract

An Island-Ohmic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN gate (IO-PGaN) structure is proposed and fabricated on a GaN-on-Si wafer. Compared to the conventional Schottky- gate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN HEMTs, the “floating” <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN layer is connected with the gate terminal via the heavily doped <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> +-GaN island in the IO-PGaN devices. A JFET-like structure formed by the Schottky-metal/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN junction delivers a self-limited gate leakage. The proposed IO-PGaN HEMT alleviates the performance trade-off between the Ohmic- and Schottky gate technologies, delivering a limited gate leakage and a stable <italic 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">TH</sub> under gate/drain voltage stress conditions. Moreover, a TCAD simulation result and an energy band diagram are provided to illuminate the principle of enhanced <italic 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">TH</sub> stability of IO-PGaN devices.