Reliability evaluation of 4H-SiC JFETs using IV characteristics and Low Frequency noise

HK Chan, RC Stevens, JP Goss, NG Wright and AB Horsfall
Materials Science Forum

Two sets of 4H-SiC signal-lateral JFETs were thermally aged at 400°C and 500°C in furnaces open to air for 1000 hours. IV and low frequency noise measurements were performed on these devices and the results were compared against the as-fabricated sample. The data from IV characterisation demonstrates that the linear and saturated drain-source current decreases monotonically with stress temperature. In addition, the linear characteristics of the JFETs have shifted approximately 1.5V along the drain-source voltage axis. Whilst the devices thermally aged at 400°C show no degradation in magnitude and behaviour in Noise Power Spectral Density (NPSD), the NPSD of 500°C stressed devices has increase approximately 30dB and it shows a full frequency spectrum of 1/f dependency up to 100 kHz. A further investigation of the noise origin reveals that the Normalised Noise Power Spectral Density (NNPSD) of the aged sample is directly proportional to RDS which is similar to the as-fabricated sample. Thus we hypothesize that the existing noise sources have intensified possibly due to the evolution of defects.

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