Nanostructures in lightly doped silicon carbide crystals with polytypic defects

Abstract

In this work, photoluminescence spectra of lightly doped SiC crystals with ingrown original defects are reported. Undoped SiC single crystals with the impurity concentration of ND – NA ~ (2…8)*10¹⁶ cm⁻³, NA ~ (2…8)*10¹⁷ cm⁻³, and ND – NA ~ (1…5)*10¹⁷ cm⁻³, ND = 10¹⁸ cm⁻³ were investigated. The analysis of absorption, excitation and low temperature photoluminescence spectra suggests formation of a new micro-phase during the growth process and appearance of the deep-level (DL) spectra. The complex spectra of the crystals can be decomposed into the so-called DLi (i = 1, 2, 3, 4) spectra. The appearance of the DLi spectrum is associated with formation of new nano-phases. Data of photoluminescence, excitation and absorption spectra show the uniformity of different DLi spectra. Structurally, the general complexity of the DLi spectra correlated with the degree of disorder of the crystal and was connected with onedimensional disorder, the same as in the case of the stacking fault (SFi) spectra. The DLi spectra differ from SFi spectra and have other principles of construction and behavior. The DLi spectra are placed on a broad donor-acceptor pairs emission band in crystals with higher concentrations of non-compensated impurities. The excitation spectra for the DLi and SFi spectra coincide and indicate formation of nanostructures 14H₁<4334>, 10H₂<55>, 14H₂<77>, 8H<44>