Strain relaxation and self-heating effects of fin AlGaN/GaN HEMTs

Abstract

In this paper, we present a methodology of 3D electro-thermo-mechanical simulation to analyze the strain relaxation and self-heating effects of fin AlGaN/GaN high electron mobility transistors (HEMTs). The free boundaries of narrow fins cause strain relaxation of the AlGaN barrier and a non-uniform strain distribution near the AlGaN/GaN interface. The strain relaxation not only reduces the surface piezoelectric polarization charges (PPCs), but also introduces space PPCs in AlGaN/GaN, leading to a reduction of two-dimensional electron gas density and a positive shift of threshold voltage (V th). The simulated V th shift with fin width agrees well with experimental results from literature. In addition, the inter-fin trenches facilitate more efficient lateral heat spreading and suppress the self-heating effect compared with the planar HEMTs with the same effective gate width.