Instability of On-Resistance in Vertical GaN PIN Diodes Under High-Temperature and Voltage Stress

The ON-resistance (
${R}_{\text {ON}}{)}$
instability of vertical GaN PIN diodes under high-temperature (up to 400 °C) and forward voltages stress were comprehensively investigated. The turn-on voltages (
${V}_{\text {ON}}{)}$
of vertical GaN PIN diodes under high temperature and forward voltage stress were generally stable, while the instability of the
${R}_{\text {ON}}$
of the devices was very pronounced under these stresses. With temperature ramping up from 25 °C to 400 °C and then cooling down to 25 °C, both the
${R}_{\text {ON}}$
and ideality factor of the devices showed a similar trend of first decreasing and then increasing. The decrease in the ideality factor was attributed to the transition from Shockley–Read–Hall (SRH) recombination to carrier diffusion currents. During the long-time temperature stress, the
${R}_{\text {ON}}$
was unstable and increased for several hours at ~150 °C–200 °C, likely due to electrical-thermal effects and the activation of nitrogen vacancies (VN) in p-GaN. For the forward voltage stress, it was found that the shift of
${R}_{\text {ON}}$
was voltage-dependent and decreased from 1.05 to 0.6
$\text{m}\Omega $
cm2 with increasing forward voltage stress due to voltage-dependent carrier accumulation. Further, increased forward voltage stress will cause the subturn ON current due to high electric field-induced electron injection into the p-GaN layer. In addition, the device
${R}_{\text {ON}}$
can also be increased by high reverse voltage biasing due to holes being driven out of the p-GaN. These results can serve as a critical reference for the reliability study of vertical GaN devices and provide guidance for the future development of robust GaN power electronics.