GaN Ring Oscillators Operational at 500 °C Based on a GaN-on-Si Platform

A study of GaN for high temperature (HT, up to 500 °C) digital circuits was conducted. A HT-robust GaN-on-Si technology based on enhancement-mode p-GaN-gate AlGaN/GaN high electron mobility transistors (HEMTs) and depletion-mode AlGaN/GaN HEMTs was proposed and used to implement different digital circuit configurations, namely E/D-mode and E/E-mode (E: enhancement, D: depletion). The E/D-mode inverter was found to offer significantly better performance in terms of voltage swing, noise margin, and gain, across temperature and
${V}_{\textit {DD}}$
scaling. As calculated from E/D-mode ring oscillators (ROs) with
${L}_{G}=2\,\,\mu \text{m}$
, a RO exhibited a propagation delay (
${t}_{p}$
) of < 1.48 ns/stage at 500 °C. The best RO achieved
${t}_{p} < 0.18$
ns/stage at 25 °C. To the best of the authors’ knowledge, the proposed technology sets a new boundary of
${t}_{p}$
vs.
${L}_{G}$
in wide band gap digital logic, and is operational at the highest reported temperature (500 °C) of a GaN digital circuit. The results reflect the promising potential of the proposed technology for emerging HT applications at 500 °C and beyond.