A 1680-V (at 1 $\hbox{mA/cm}^{2}$) 54-A (at 780 $\hbox{W/cm}^{2}$) Normally ON 4H-SiC JFET With 0.143- $\hbox{cm}^{2}$ Active Area

IEEE Electron Device Lett.

Stewart

Hearne

et al. 2010

A normally-ON 9-kV (at 0.1-mA/cm 2 drain leakage) 1.52 × 10 −3 -cm 2 active-area vertical-channel SiC JFET (VJFET) is fabricated with no e-beam lithography, no epitaxial regrowth, and a three-step junction-termination-extension edge termination, which is connected to the gate bus through an ion-implanted sloped extension. The VJFET exhibits low leakage currents and a sharp onset of gate-voltage breakdown occurring at 80 V. To lower resistance, the VJFET is designed to be very normally-ON, which minimizes the channel resistance contribution. At a gate bias of 0 V, the VJFET's drain current is 73 mA with a forward drain voltage drop of 5 V (240 W/cm 2 ), a specific ON-state resistance of 104 mΩ · cm 2 , and a current gain of I D /I G = 6.4 × 10 6 . Operating at a unipolar gate bias of 2.5 V lowers the ON-state resistance to 96 mΩ · cm 2 and raises the drain-current output to 79.3 mA, with the current gain being relatively high at I D /I G = 2346. Thus, this 9-kV VJFET is capable of efficient power switching operation with high current gain at a low unipolar resistance.

mentioning

confidence: 99%

A 9-kV Normally-on Vertical-Channel SiC JFET for Unipolar Operation

IEEE Electron Device Lett.

Stewart

Hearne

et al. 2010

“…with vertical [1], [2] and lateral [3], [4] channels have been fabricated with resistances of 5.5 and 10 mΩ · cm 2 , respectively. However, power circuit designers desire normallyoff (N-OFF) devices due to their inherent fault protection capabilities.…”

mentioning

confidence: 99%

“…The review of this letter was arranged by Editor S.-H. Ryu and low-voltage N-OFF SiC vertical-channel JFETs (VJFETs), connected in the cascode configuration, have been successfully implemented [5]. In this letter, we examine the merit of a 1290-V recessed-implanted-gate (RIG) no-epitaxial-regrowth N-OFF 4H-SiC VJFET stand-alone power switch, which is based on the manufacturable large-area VJFET design of [1] and [2]. We present the first 1200-V-class N-OFF (V gs = 0 V) VJFET to achieve its voltage rating with a sharp onset of breakdown occurring at ≤ 1 mA/cm 2 leakage drain-current density.…”

mentioning

confidence: 99%

Investigation of the Suitability of 1200-V Normally-Off Recessed-Implanted-Gate SiC VJFETs for Efficient Power-Switching Applications

IEEE Electron Device Lett.

Hearne

Stewart

et al. 2009

Self Cite

A recessed-implanted-gate (RIG) 1290-V normallyoff (N-OFF) 4H-SiC vertical-channel JFET (VJFET), fabricated with a single masked ion implantation and no epitaxial regrowth, is evaluated for efficient power conditioning applications. The relationship between the VJFET's ON-state resistance and current gain is elucidated. Under high-current-gain operation, which is required for efficient power switching, the 1200-V N-OFF (enhancement mode) VJFET exhibits a prohibitively high ON-state resistance. Comparison with 1200-V normally-on VJFETs, fabricated on the same wafer, confirms experimentally that the strong gate-depletion-region overlap required for 1200-V N-OFF blocking is the principal contributor to the prohibitively high specific ON-state resistance observed under high-current-gain VJFET operation. Perfecting the 1200-V edge termination structure, which can reduce the theoretical drift specific ON-state resistance from 2.2 to 1.5 mΩ · cm 2 , has a negligible impact in decreasing the channel-dominated 1200-V N-OFF VJFET resistance. The RIG VJFET channel-region optimization simulations (assuming a single commercial implantation and no epitaxial regrowth) revealed that, although aggressively increasing channel doping lowers the resistance, the corresponding reduction in the source mesa width can prohibitively limit manufacturability.Index Terms-Current gain, enhancement mode, JFET, normally-off (N-OFF), vertical channel, 1200 V, 4H-SiC.

“…3 Investigation of the suitability of 1200 V normally-off vertical-channel SiC JFETs for power switching applications SiC JFETs are presently regarded as the most mature solution for 1200 V high power/temperature switching applications as they have no oxide mobility or reliability issues, do not suffer from forward voltage degradation, and can operate at high current gains [23,24] and at elevated temperatures [25,26]. Circuit designers are attracted to these capabilities of VJFET power devices and would like to deploy them as direct replacements of power silicon MOSFETs and IGBTs.…”

mentioning

confidence: 99%

“…By reducing the source-pillar width to 0.6 μm and 0.5 μm (all other design parameters identical for VJFETs situated on the same wafer), the VJFETs become normally-off to 80 V and 280 V, respectively. As stated in Section 2, normally-on 1200 V-class large-area JFETs with lateral [12,21] and vertical [23,24] channels have been fabricated. They typically utilize ~12 μm drift layers doped at mid 10 15 cm -3 , and have specific on-state resistances of 10 mΩ cm 2 and 5.5 mΩ cm 2 for the lateral and vertical channel cases, respectively.…”

mentioning

confidence: 99%

1200 V SiC vertical‐channel‐JFETs and cascode switches

Physica Status Solidi (a)

2009

Wide band gap semiconductors like silicon carbide (SiC) are currently being developed for high power/temperature applications. Silicon carbide is ideally suited for power switching due to its high saturated drift velocity, its high critical field strength, its excellent thermal conductivity, and its mechanical strength. For power devices, the tenfold increase in critical field strength of SiC relative to Si allows high voltage blocking layers to be fabricated significantly thinner than those of comparable Si devices. This reduces device on‐state resistance and the associated conduction and switching losses, while maintaining the same high voltage blocking capability. The specific on‐state resistance of 4H‐SiC is approximately 400 times lower than that of Si at a given breakdown voltage. This allows for high current operation at relatively low forward voltage drop. In addition, the wide band gap of SiC allows operation at high temperatures where conventional Si devices fail. In this article, we will review Northrop Grumman's single‐implant no‐epitaxial‐regrowth vertical‐channel JFET. The feasibility of efficient 1200 V normally‐off VJFET operation will be investigated. The all‐SiC VJFET based cascode switch will be introduced and aspects of its operation evaluated. High temperature DC characteristics of VJFETs and 1200 V normally‐off cascode switches will be discussed. Finally, the development of large‐area high‐current 1200 V VJFETs and their edge termination performance will be presented. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)