Optical characterization of radiative deep centres in 6H SiC junction field effect transistors
Electroluminescence studies were carried out as a function of bias and temperature to understand the nature of deep centres in 6H–SiC n-channel junction field-effect transistors (FETS) for high-power applications. Vanadium impurities in different configurations were suggested to be responsible for the levels found. The contributions of hot and cold carriers were distinguished by biasing the devices both in the transistor-like and in the diode-like configurations. This allowed us to spatially localize the deep centres inside the device structure. In the transistor-like configuration, two broad emission bands (1.1–1.7 eV and 2.5–3 eV), superimposed to the contribution arising from hot carrier intraband transitions, were detected. The A band at 1.17 eV (observed only in the transistor-like configuration) was attributed to a radiative transition between an excited level and its ground state of a vanadium centre located in the n-type conductive channel. The B (1.32 eV) and C (1.62 eV) bands originated from the space–charge region of the p–n junctions in both the configurations and, contrary to the A band, they were characterized by a thermal capture barrier (180 meV) which inhibits the luminescence in the diode-like configuration at temperatures below 200 K.