Features of the Band-Edge Injection Electroluminescence in 4H-SiC pn Structures

Abstract

Band-edge (hνmax=3.17-3.18 eV at T=293 K) injection electroluminescence (IEL) characteristics of 4H-SiC pn structures as a function of doping, electron irradiation, temperature, and current are presented. The intensity of the UV band increases with temperature in the range 290-800 K (with an activation energy Ea of about 90 meV), which is observed for the first time in a wide range of current densities from 9 A/cm2 up to 2∙104 A/cm2. This effect is a fundamental feature of the band-edge IEL in SiC pn structures. The dependence of the intensity L on the current is of the power-law type, L~Jm; at high currents m≈1 at T=650-800 K. This result is probably the first direct observation of the diffusion current in SiC pn structures. The rise in the intensity of the band-edge IEL with increasing temperature and its decrease upon irradiation are probably due to the corresponding change in the lifetime of nonequilibrium carriers.