Self-heating in high-power AlGaN-GaN HFETs

TLDR

Heat dissipation strongly influences HFET characteristics immediately after applying source‑drain voltage. The study compares self‑heating in AlGaN‑GaN HFETs fabricated on sapphire versus SiC substrates. For HFETs with epilayer thickness below 1.5 µm, the thermal impedance is governed by the substrate, and devices on 6H‑SiC exhibit a thermal impedance about ten times lower than those on sapphire, demonstrating that SiC‑based AlGaN‑GaN HFETs combine superior electron transport with excellent thermal performance, making them suitable for high‑power applications.

Abstract

We compare self-heating effects in AlGaN-GaN heterostructure field effect transistors (HFETs) grown on sapphire and SiC substrates. Heat dissipation strongly affects the device characteristics soon after the application of the source-drain voltage (in less than 10/sup -7/ s). Our results show that in HFET's with the total epilayer thickness less than 1.5 μm, the thermal impedance, /spl Theta/ is primarily determined by the substrate material and not by the material of the active layer. For our devices grown on 6H-SiC substrates, we measured /spl Theta/ of approximately 2/spl deg/C/spl middot/mm/W, which was more than an order of magnitude smaller than /spl Theta/=25/spl deg/C mm/W measured for similar AlGaN/GaN HFET's grown on sapphire. Our results demonstrate that AlGaN-GaN HFET's grown on SiC substrates combine advantages of superior electron transport properties in AlGaN/GaN heterostructures with excellent thermal properties of SiC, which should make these devices suitable for high-power electronic applications.