Photoluminescence of electron-irradiated 4H-SiC

We report the properties of a photoluminescence (PL) spectrum, here called EA, appearing after room-temperature electron irradiation of 4H-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 hoped substrates. Annealing at around 750 degrees C induces an abrupt change in the spectrum. Further annealing steps occur at temperatures above 750 degrees C eventually leading to the dominance of the strong DI PL spectrum. We have investigated the polarization, temperature dependence, and excitation properties crf the; Ed FL. Up to 40 no-phonon lines can be resolved in the EA spectrum. All the no-phonon lines appeal 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. [S0163-1829(99)08611-7].