Nanograin boundaries and silicon carbide photoluminescence

Abstract

The luminescence spectra of SiC crystals and films with grain boundaries (GB) on the atomic level were observed. The GB spectra are associated with luminescence centers localized in areas of specific structural abnormalities in the crystal, without reference to the one-dimensional layer-disordering. The zero-phonon part of GB spectra is always within the same energy range (2.890…2.945 eV) and does not fit in the dependence of its position in the energy scale on the percent of hexagonality, as in the case of stacking faults (SFᵢ) and deep level (DLᵢ) spectra. The zero-phonon part 2.945…2.890 eV with a fine structure is better observed in crystals with the centers of origin growth of the crystal, if Nᴰ – Nᴬ ~ (2…8)·10¹⁶ cm⁻³, ND ~ (2…7)·10¹⁷ cm⁻³. The edge phonons of the Brillouin zone TA-46 meV, LA-77 meV, TO-95 meV, and LO-104 meV are involved in the development of the GB spectrum. This spectrum may occur simultaneously with the DLᵢ and SFᵢ ones. The GB spectra also occur after high-temperature processing of the β-phase (in the 3C-SiC) with the appearance of the α-phase. The temperature range of observation is 4.2…40 K. There is synchronous thermal quenching of all elements in the fine structure. The thermal activation energy of quenching is Еₐᵀ ~ 7 meV.