Detection of Very Fast Interface Traps at 4H-SiC/AlN and 4H-SiC/Al₂O₃ Interfaces

Abstract

Modest channel carrier mobility in SiC-MOSFETs with NO annealed gate oxides has been the main factor hampering development of low power devices (300 – 650 V). A very fast interface trap, noted as NI, has been suggested to be the main culprit for poor inversion channel carrier mobility. The origin of the NI trap is unknown, but it is likely a property of the SiO2 and it is enhanced during post nitridation. In this study we show that the NI trap is also detected in 4H-SiC/AlN and 4H-SiC/Al2O3 MIS-capacitors. Observations are done using conductance spectroscopy and capacitance voltage measurements at cryogenic temperatures. This strongly suggests that the NI trap is a property of the SiC surface and not the dielectric used to form the SiC/dielectric interface. Furthermore, a scanning transmission electron microscopy (STEM) was performed to confirm that there are no SiO2 layers or islands present at the 4H-SiC/AlN and 4H-SiC/Al2O3 interfaces.