DC and RF Performance of Gate-Last AlN/GaN MOSHEMTs on Si With Regrown Source/Drain

Abstract

This paper presents the fabrication and characteristics of self-aligned gate-last AlN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) featuring regrown source/drain for low ON-state resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ). Previously, we demonstrated conventional enhancement-mode AlN/GaN MOSHEMTs on Si substrate with excellent DC performance but limited RF characteristics by large parasitic gate-to-source/drain overlap capacitance. In this paper, the self-aligned gate-last process was developed to minimize the parasitic capacitance. SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> sidewall and supporting layer were inserted to separate the gate head and source/drain. In the gate-last devices, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> has been improved to be ~40 GHz with a channel length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) of 210 nm. Delay time analysis showed that drain delay was relatively small compared with gate transit and parasitic charging time because of the self-aligned structure.