4H-SiC Power BJTs with High Current Gain and Low On-Resistance
4H-SiC BJTs have been fabricated with varying geometrical designs. The maximum value of the current gain was about 30 at IC=85 mA, VCE=14 V and room temperature (RT) for a 20 μm emitter width structure. A collector-emitter voltage drop VCE of 2 V at a forward collector current 55 mA (JC = 128 A/cm2) was obtained and a specific on-resistance of 15.4 m2·cm2 was extracted at RT. Optimum emitter finger widths and base-contact implant distances were derived from measurement. The temperature dependent DC I-V characteristics of the BJTs have been studied resulting in 45 % reduction of the gain and 75 % increase of the on-resistance at 225 oC compared to RT. Forward-bias stress on SiC BJTs was investigated and about 20 % reduction of the initial current gain was found after 27.5 hours. Resistive switching measurements with packaged SiC BJTs were performed showing a resistive fast turn-on with a VCE fall-time of 90 ns. The results indicate that significantly faster switching can be obtained by actively controlling the base current.
N. Wright, C.M. Johnson, K. Vassilevski, I. Nikitina and A. Horsfall
H. S. Lee et al., "4H-SiC Power BJTs with High Current Gain and Low On-Resistance", Materials Science Forum, Vols. 556-557, pp. 767-770, 2007