Electrically detected magnetic resonance study of a near interface trap in 4H SiC MOSFETs

It is well known that 4H silicon carbide (SiC) based metal oxide silicon field effect transistors (MOSFETs) have great promise in high power and high temperature applications. The reliability and performance of these MOSFETs is currently limited by the presence of SiC/SiO₂ interface and near interface traps which are poorly understood. Conventional electron paramagnetic resonance (EPR) studies of silicon samples have been utilized to argue for carbon dangling bond interface traps [1]. For several years, with several coworkers, we have explored these silicon carbide based MOSFETs with electrically detected magnetic resonance (EDMR), [2,3] establishing a connection between an isotropic EDMR spectrum with g=2.003 and deep level defects in the interface/near interface region of SiC MOSFETs. We tentatively linked the spectrum to a silicon vacancy or closely related defect. This assessment was tentative because we were not previously able to quantitatively evaluate the electron nuclear hyperfine interactions at the site. Through multiple improvements in EDMR hardware and data acquisition software, we have achieved a very large improvement in sensitivity and resolution in EDMR, which allows us to detect side peak features in the EDMR spectra caused by electron nuclear hyperfine interactions. This improved resolution allows far more definitive conclusions to be drawn about defect structure. In this work, we provide extremely strong experimental evidence identifying the structure of that defect. The evidence comes from very high resolution and sensitivity “fast passage” (FP) mode [4, 5] electrically detected magnetic resonance (EDMR) or FPEDMR of the ubiquitous EDMR spectrum.