Diffraction Contrast of Threading Dislocations in GaN and 4H-SiC Epitaxial Layers Using Electron Channeling Contrast Imaging

Forescattered electron channeling contrast imaging (ECCI) offers the potential for imaging and analyzing extended defects in a scanning electron microscope (SEM). Indeed, it is shown that ECCI is able to determine the Burgers vector of threading dislocations with the aid of carefully determined experimental parameters and accompanying image simulations. Simulations are compared with ECC images from samples with features that are relatively easily studied and modeled: those based on specially engineered 4H-SiC mesa substrates. These mesas serve as substrates for both homoepitaxial 4H-SiC layers and heteroepitaxial GaN layers in which images of threading dislocations (TDs) have been recorded using ECCI and found to strongly resemble diffraction contrast simulations of TD intensity profiles.