Avinash Srikrishnan Kashyap

Direct comparison of silicon and silicon carbide power transistors in high-frequency hard-switched applications

RECENT progress in wide bandgap power (WBG) switches shows great potential. Silicon carbide (SiC) is a promising material for power devices with breakdown voltages of several hundred volts up to 10 kV. SiC Schottky power diodes have achieved widespread commercial acceptance. Recently, much progress has been made on active SiC switches, including JFETs, thyristors, BJTs, IGBTs, and MOSFETs. Many a great promise has been made, and wondrous claims abound, but the question remains: will they live up to the hype? We explore this question for the class of high-frequency, hard-switched converters with input voltages of up to 600 VDC and power throughputs in the kilowatt range. Experimental evidence shows that both superior efficiency and higher power density may be obtained via the use of SiC MOSFETs. A direct comparison is made using silicon power devices (IGBTs and MOSFETs) and SiC MOSFETs in a 200 kHz, 6 kW, 600 V hard-switched converter. The losses are measured and conduction and switching losses of the active devices are estimated. Total losses can be reduced by a factor of 2–5 by substitution of SiC MOSFETs for Si active power devices.

Silicon Carbide High Temperature Operational Amplifier

Development of silicon carbide operational amplifier offers an attractive alternative building block for the replacement of silicon and silicon-on-insulator analog circuits in harsh environment applications. NMOS-based enhancement mode silicon carbide device technology was utilized to demonstrate feasibility of operational amplifiers for use in harsh environment applications. This study reports on the results of characterization of operational amplifiers at room temperature and high temperatures up to 350°C. The development of high temperature packaging techniques enabled assembly of a functional oscillator board tested up to 350°C. A test fixture with high temperature sockets enabling quick swap of operational amplifiers is also discussed as an important tool in high temperature electronics research and development.

Compact modeling of silicon carbide lateral MOSFETs for extreme environment integrated circuits

Silicon carbide (SiC) based semiconductor devices have been gaining tremendous traction in the last decade due to the inherent material advantages [1]. While most of the efforts in developing SiC devices are focused on discrete power semiconductors, a team at GE GRC is developing SiC based integrated circuits that can be used in extremely high temperature applications such as geothermal drilling, aviation electronics, space exploration etc. [2] This ability of SiC is attributed to its low intrinsic carrier concentration, due to which SiC based devices have leakage currents that are several orders of magnitude lower than their Si counterparts under high ambient temperatures.

A silicon carbide integrated circuit implementing nonlinear-carrier control for boost converter applications

The properties of silicon carbide (SiC) integrated circuit (IC) processes are discussed and nonlinear-carrier control is proposed as a controller topology that can work within the design challenges presented by SiC. A boost converter with NLC controller is demonstrated using circuit blocks built with SiC IC models.

4H-SiC 1200 V Junction Barrier Schottky Diodes with High Avalanche Ruggedness

A state-of-the art family of 1200 V junction barrier Schottky (JBS) diodes was developed. These devices are highly competitive in switching applications thanks to low specific series resistance (1.8 mΩ.cm2 at current rating) and low capacitive charge (1420 nC.cm-2 at 800 V). A uniform avalanche distribution over the active area combined with an optimized high-voltage termination provides industry-leading UIS capabilities. Stringent reliability tests were performed to meet the qualification requirements for the industrial market.

Highly rugged 1200 V 80 mQ 4-H SiC power MOSFET

A novel 1200 V, 80 mΩ 4-H SiC power MOSFET with a shallow step p-body has been proposed for applications with highly rugged requirements. The innovative p-body design mitigates the problems arising due to the electric-field concentration at the corners that trigger the parasitic bipolar structure in conventional planar DMOS devices. TCAD simulations of the proposed device clearly demonstrate this improvement, along with significantly lower impact ionization rates at the corner of the p-body. The shallow step p-body approach, combined with a robust gate oxide and layout design, contributed to an industry-leading UIS capability of 2900 mJ of single pulse avalanche energy, and 5.8 μs of short circuit withstand time.