Doping-induced strain in N-doped 4H–SiC crystals

Abstract

Stress in epitaxial layers due to crystal lattice mismatch directly influences the growth, structure, and basic electrophysical parameters of epitaxial films and also to a large extent the degradation processes in semiconductor devices. In this letter, we present a theoretical model for calculating the induced lattice compression due to N doping and the critical thickness concerning formation of misfit dislocations in homoepitaxial 4H–SiC layers with different N-doping levels. For example: The model predicts that substrates with a N concentration of 3×1019 cm−3 induce misfit dislocations when the epilayer thickness reaches ∼10 μm. Also, the N-doping concentration in the 1×1018–1×1019 cm−3 range yields a strain that not will cause misfit dislocactions at the substrate and epilayer interface until an epilayer thickness of 200–300 μm is reached. Supporting evidence of the induced lattice compression due to N doping have been done by synchrotron white-beam x-ray topography on samples with different N-doping levels and are compared with the predicted results from the model.