Abstract
We report the temperature dependence of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of biaxial α-SnS in the spectral energy region from 0.74 to 6.42 eV and temperatures from 27 to 350 K using spectroscopic ellipsometry. Bulk SnS was grown by temperature gradient method. Dielectric response functions were obtained using multilayer calculations to remove artifacts due to surface roughness. We observe sharpening and blue-shifting of CPs with decreasing temperature. A strong exciton effect is detected only in the armchair direction at low temperature. New CPs are observed at low temperature that cannot be detected at room temperature. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose–Einstein statistical factor and the temperature coefficient for describing the electron–phonon interaction.
A calculation is made of the temperature dependence of the energy levels of shallow donor impurities in silicon. This temperature dependence arises from the electron–phonon interaction and we consider mixing only of the {1s}, {2s), and {2p0} electronic states. A comparison is made with experiment for the case of phosphorus-doped silicon.
The spectral distribution of photoconductivity and the temperature dependence of the photocurrent of monocrystals MnGaInS4 are studied. The intrinsic and extrinsic photoconductivities are revealed in the spectrum of photoconductivity. The wavelength range of 0.640–0.760 μm is shown when manganese deficiency in crystals appears and is due to an acceptor defect. The temperature dependence of the band gap in the monocrystals MnGaInS4 is related to the electron – phonon interaction. In the studied temperatures, increase in the photocurrent is associated with the thermal depletion of the attachment levels. The activation energy of the attachment levels is estimated.
Temperature dependence of the dielectric function and critical points of α-SnS from 27 to 350 K
