Photoluminescence of electron-irradiated4H−SiC

Abstract

We report the properties of a photoluminescence (PL) spectrum, here called $E_A,$ appearing after room-temperature electron irradiation of $4H-\mathrm{SiC}.$ The spectrum consists of several sharp no-phonon lines accompanied by a broad phonon-assisted structure. Among the samples investigated were epitaxial layers of low residual doping and highly doped substrates. Annealing at around 750 °C induces an abrupt change in the spectrum. Further annealing steps occur at temperatures above 750 °C eventually leading to the dominance of the strong $D_{\mathrm{I}}$ PL spectrum. We have investigated the polarization, temperature dependence, and excitation properties of the $E_A$ PL. Up to 40 no-phonon lines can be resolved in the $E_A$ spectrum. All the no-phonon lines appear within the span of approximately 100 meV (2.8–2.9 eV). By photoluminescence excitation spectroscopy we are able to establish the relationship between most of the different lines. The lines come in groups of two to four lines. The general characteristics of the line groups suggest that they are due to bound exciton recombination at isoelectronic defect centers.