Time-gated optical spectroscopy of field-effect-stimulated recombination via interfacial point defects in fully processed silicon carbide power MOSFETs
Sprache des Titels:
Englisch
Original Kurzfassung:
Fully processed SiC power MOSFETs emit light during switching of the gate terminal, while the drain and source terminals are both grounded. The emitted photons are caused by defect-assisted recombination of electrons and holes at the 4???-SiC/SiO2 interface, and can be detected through the SiC substrate. Here we present time-gated spectroscopic characterization of these interfacial point defects. Unlike in previous studies, the devices were opened in such a way that the drain contact remained electrically active. A separate examination of the photons emitted at the rising and falling transitions of the gate-source voltage enabled the extraction of two different spectral components. One of these components consists of a single transition with phonon replicas of a local vibrational mode with an astonishingly high energy of 220?meV?well above the highest phonon modes in 4???-SiC and SiO2 of 120 and 137?meV, respectively. On the basis of a quantum mechanical model, we successfully fitted its emission spectrum and assigned it to donor-acceptor-pair recombination involving a carbon-cluster-like defect. Other transitions were assigned to EH6/7-assisted, EK2-D, and nitrogen-aluminum donor-acceptor-pair recombination. Because of the relevance of these defects in the operation of SiC MOSFETs, these insights will contribute to improved reliability and performance of these devices.
Forschungs-