1.2-kV Vertical GaN Fin-JFETs: High-Temperature Characteristics and Avalanche Capability

This work describes the high-temperature performance and avalanche capability of normally-off 1.2-K V-CLASS vertical gallium nitride (GaN) fin-channel junction field-effect transistors (Fin-JFETs). The GaN Fin-JFETs were fabricated by NexGen Power Systems, Inc. on 100-mm GaN-on-GaN wafers. The threshold voltage ( V
_{\text TH}
) is over 2 V with less than 0.15 V shift from 25 °C to 200 °C. The specific ON-resistance ( R
_{\scriptscriptstyle ON}
) increases from 0.82 at 25 °C to 1.8 \textmΩ·cm
²
at 200 °C. The thermal stability of V
_{\text TH}
and R
_{\scriptscriptstyle ON}
are superior to the values reported in SiC MOSFETs and JFETs. At 200 °C, the gate leakage and drain leakage currents remain below 100 μ\textA at -7-V gate bias and 1200-V drain bias, respectively. The gate leakage current mechanism is consistent with carrier hopping across the lateral p-n junction. The high-bias drain leakage current can be well described by the Poole-Frenkel (PF) emission model. An avalanche breakdown voltage ( BV
_{\text AVA}
) with positive temperature coefficient is shown in both the quasi-static I- V sweep and the unclamped inductive switching (UIS) tests. The UIS tests also reveal a BV
_{\text AVA}
over 1700 V and a critical avalanche energy ( E
_{\text AVA}
) of 7.44 J/cm
²
, with the E
_{\text AVA}
comparable to that of state-of-the-art SiC MOSFETs. These results show the great potentials of vertical GaN Fin-JFETs for medium-voltage power electronics applications.