Understanding the impact of extended crystalline defects on 4H-SiC power MOSFETs by multiscale correlative electrical, optical and thermal characterizations

Extended defects in 4H-SiC epitaxy are currently the object of intensive studies, as they represent one of the limiting factor for the performances and reliability of 4H-SiC power devices. A multiscale correlative approach, based on the combination of device-level electrical measurements, micrometre resolution optical spectroscopies, and nanoscale resolution electrical (KPFM, sMIM) and thermal (SThM) scanning probe microscopies, has been applied to investigate the impact of prismatic stacking faults (“carrot-like”) on the electrical properties of 4H-SiC planar MOSFETs. The presence of a “carrot-like” defect in the device was found not to affect significantly the transistors electrical characteristics, whereas it showed an impact on the IDS-VDS characteristics of the body diode, resulting in an overcurrent at low forward bias and an increased series resistance at high current levels. The appearance of an extra peak in the micro-PL spectrum of 4H-SiC on the carrot-like defect area was ascribed to a band gap shrinking within the 4H-SiC. Such a scenario was confirmed by local variations of the surface potential and impedance signals on the carrot-like area. A significant reduction of local thermal conductivity on the carrot-like defect with respect to surrounding 4H-SiC, which may explain the increased body diode series resistance at high currents.