Nonradiative recombination at threading dislocations in 4H-SiC epilayers studied by micro-photoluminescence mapping

Threading dislocations (TDs) in 4H-SiC epilayers have been investigated by means of micro-photoluminescence (mu-PL) mapping at room temperature. Enhanced nonradiative recombination at TDs was confirmed experimentally, resulting in a reduced local PL emission intensity in the mu-PL intensity map performed at 390 nm (near band-edge emission). The behavior of nonradiative recombination at TDs depends on the dislocation type: the screw type of TDs shows stronger effect on the nonradiative recombination activity than the edge type, evidencing a larger local reduction of PL emission intensity. Furthermore, the contrast of TDs in the mu-PL intensity map greatly depends on the carrier lifetimes of the 4H-SiC epilayers. Lifetimes longer than 0.5 mu s are essential to obtain a discernible contrast for the individual TDs. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622336]