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-TH) is over 2 V with less than 0.15 V shift from 25 degrees C to 200 degrees C. The specific ON-resistance (R-ON) increases from 0.82 at 25 degrees C to 1.8 m Omega.cm(2) at 200 degrees C. The thermal stability of V-TH and RON are superior to the values reported in SiC MOSFETs and JFETs. At 200 degrees C, the gate leak-age and drain leakage currents remain below 100 mu A 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 PooleFrenkel (PF) emission model. An avalanche breakdown voltage (BVAVA) with positive temperature coefficient is shown in both the quasi-static IV sweep and the unclamped inductive switching (UIS) tests. The UIS tests also reveal a BVAVA over 1700 V and a critical avalanche energy (E-AVA) of 7.44 J/cm(2), with the E-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.