Studies on Fabrication and Reliability of GaN High-Resistivity-Cap-Layer HEMT

In this paper, we systematically investigate the effect of hydrogen plasma treatment radio frequency (RF) power, treatment time, and rapid thermal annealing (RTA) on the performance of high-resistivity-cap-layer high-electron-mobility-transistor (HRCL-HEMT). It is found that high RF power contributes to obtain high drain current, but induces more damage. An appropriate RTA process not only can repair the plasma damage but also improves the static characteristics of HRCL-HEMT. Subsequently, a large hydrogen plasma treatment time window of 4 min is demonstrated with an optimized RF power of 2 W and RTA at 350 °C for 5 min. Furthermore, the thermal stability of the optimized HRCL-HEMT is investigated by high temperature test and long-term thermal stress test. No obvious degradation of
${V}_{\text {TH}}$
,
${I}_{G}$
,
${R}_{\text {SH}}$
, and dynamic
${R}_{ \mathrm{\scriptscriptstyle ON}}$
is observed in both before and after passivation devices after 1000-h thermal stress. Finally, gate reliability of the HRCL-HEMT is also analyzed by time-to-failure test. The maximum gate voltage is determined to be 6.28 V for a ten-year lifetime with a failure rate of 1% at 25 °C.