Band Gap Energies Of Crystals Research Articles

Composition-tuned optical absorption and luminescence of TlGaxIn1-xS2 layered mixed crystals at T = 10 K

Transmittance on TlGaxIn1-xS2 mixed crystals (0 ≤ x ≤ 1) was carried out in the 2.35–2.75 eV photon energy range at T = 10 K. Band gap energies of crystals were obtained utilizing the derivative spectra of transmittance and photon energy dependence of absorption coefficient. The dependence of direct band gap energy on composition at T = 10 K revealed that as gallium composition is elevated in the mixed crystals, the direct band gap energy increases from 2.56 to 2.67 eV.Photoluminescence spectra of TlGaxIn1-xS2 crystals were studied in the photon energy region of 2.30–2.95 eV at T = 10 K. The observed bands were attributed to transitions of electrons from shallow donor levels to valence band. The shift of PL bands to higher energies with increasing gallium content was revealed. Furthermore, composition ratio of crystals was determined from energy dispersive spectroscopy experiments.

The dynamic Stark effect under a not-too-strong femtosecond excitation regime in quantum well structures

Using straightforward time-dependent perturbation treatment, transient coherent radiation-semiconductor interaction mechanisms are investigated analytically in a quantum well structure (QWS) duly irradiated by a moderate power femtosecond laser with photon energy slightly less than the crystal bandgap energy. The transition energy is calculated by recognizing the finite potential well depth of the QWS. The effects of higher excitonic states on the Stark shift and self-energy correction are examined in GaAs/AlGaAs QWS. The study shows a red shift with increasing excitation intensity and the shift is also found to be less when all the discrete excitonic states below the band edge are considered together. An increased self-energy correction accompanies this red shift.