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

Abstract

This work describes the high-temperature performance and avalanche capability of normally-OFF 1.2-kV-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 • C to 200 • C. The specific ON-resistance (R ON) increases from 0.82 at 25 • C to 1.8 m•cm 2 at 200 • C. The thermal stability of V TH and R 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 μA 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 AVA) with positive temperature coefficient is shown in both the quasistatic I-V sweep and the unclamped inductive switching (UIS) tests. The UIS tests also reveal a BV AVA 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.

Multidimensional device architectures for efficient power electronics

“…114 Finally, due to a higher power density, the device packaging and thermal management will be important, and a device-package, electrothermal co-design would be beneficial. (19,(33)(34)(35)(36)(37)(42)(43)(44). The four bands illustrate the performance limits of Si and WBG superjunction devices, WBG multichannel devices, as well as WBG FinFETs and trigate devices.…”

“…FinFET and trigate devices have been demonstrated in SiC [39][40][41][42] and GaN 38 , and in both vertical MOSFETs and lateral HEMTs, with the state-of-the-art performance exceeding the 1D 𝑅 limit. 19,36,[42][43][44] The device physics of these multidimensional device architectures will be elaborated in the following sections. Interestingly, their performance limits can be continuously enhanced by scaling certain structural parameters, resulting in a new band of device limits beyond the 1D limit line for each power semiconductor material (Fig.…”

“…This processing issue is not present for GaN Fin-JFETs due to their implantation-free fabrication. 44 In conjunction with the fin scaling, GaN fin channels can be doped 10 times higher than the drift region without impairing the E-mode operation, further lowering 𝑅 . An industrial vertical GaN Fin-JFET was demonstrated with an R ON,SP of 0.82 Ωꞏcm 2 and BV over 1700 V, 44,78 rendering the highest FOM in kilovolt-class transistors.…”

Comprehensive Design and Numerical Study of GaN Vertical MPS Diodes Towards Alleviated Electric Field Crowding and Efficient Carrier Injection

“…4(b), an effective electric field shielding effect can be formed, thus eliminating the leakage path across the Schottky region. In the meantime, the reverse leakage current flows through the reverse biased pn junction to the ohmic contact on the p-GaN structure, which has been observed in experimentally fabricated vertical GaN Fin-JFETs [33], [34]. As a result, by optimizing the p-doping concentration, the reverse breakdown and leakage behavior of the MPS diodes can be equivalent to that of a pn diode instead of a conventional planar SBD, leading to a dramatic improvement in the reverse characteristics.…”

On the Scope of GaN-Based Avalanche Photodiodes for Various Ultraviolet-Based Applications

“…On bulk GaN substrates, lo and behold, the impact ionization and avalanche breakdown were finally reported in p-i-n diodes in 2013 by Avogy Inc. (Disney et al, 2013). Since then, multiple research groups have reported the avalanche breakdown in GaN p-n diodes and extended the capability to Junction Field-Effect Transistors (JFETs) (Kizilyalli et al, 2013;Nomoto et al, 2016;Cao et al, 2018;Maeda et al, 2018;Ji D. et al, 2019;Maeda et al, 2019a;Fukushima et al, 2019;Ohta et al, 2019;Ji et al, 2020a;Ji et al, 2020b;Ji and Chowdhury, 2020;Liu et al, 2020;Liu et al, 2021). Our GaN APDs (Ji et al, 2020b), were also grown on the bulk GaN, which fulfilled the first requirement of high-qualitylow defect density (LDD) epitaxial films.…”