Abstract
The temperature dependence of exciton-related photoluminescence in 4H-SiC grown by step-controlled epitaxy has been studied in detail. In the low-temperature region, luminescence by recombination of free excitons and excitons bound to neutral nitrogen donors could be observed. From the energy of luminescence peaks by bound excitons, the temperature dependence of the exciton energy gap in 4H-SiC was obtained. The luminescence spectra of free excitons could be explained using a theoretical Maxwellian distribution of the kinetic energy of free excitons, based on a law for indirect-band semiconductors. In thermal quenching properties, the intensity of luminescence by bound excitons decreased with temperature. The quenching energy for luminescence by bound excitons was about 25 meV which was almost coincident with the previously reported binding energy of 20 meV. On the other hand, the intensity of luminescence by free excitons increased to 50 K, and after showing the maximum, it became quenched. From a rate equation analysis using transfer processes among free excitons and bound excitons, the above behavior is explained semiquantitatively.
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