4 results
Search Results
Now showing 1 - 4 of 4
Article Citation - WoS: 2Citation - Scopus: 2Space-charge-limited currents and photoconductive properties of Tl2InGaSe4 layered crystals(Taylor & Francis Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.The extrinsic electronic parameters of Tl2InGaSe4 layered crystals were investigated through measurement of the temperature-dependent dark conductivity, space-charge-limited currents and photoconductivity. Analysis of the dark conductivity reveals the existence of two extrinsic energy levels at 0.40 and 0.51 eV below the conduction band edge, which are dominant above and below 260 K, respectively. Current-voltage characteristics show that the one at 0.51 eV is a trapping energy level with a concentration of (4.8-7.7) x 10(10) cm(3). Photoconductivity measurements reveal the existence of another energy level located at 0.16 eV. In the studied temperature range, the photocurrent increases with increasing temperature. The dependence of the photoconductivity on the incident light intensity exhibits a linear recombination character near room temperature and a supralinear character as the temperature decreases. The change in recombination mechanism is attributed to an exchange in the behavior of sensitizing and recombination centres.Article Influence of Photonic Excitations on the Electrical Parameters of Tlins2 Crystals(Wiley-v C H verlag Gmbh, 2010) Qasrawi, A. F.; Gasanly, N. M.The photo-excitation effect on the current transport mechanism in TlInS2 crystals has been studied by means of dark and illuminated conductivity measurements. The temperature-dependent electrical conductivity analysis in the temperature region of 110-340 K revealed the domination of the thermionic emission and the thermally assisted variable range hopping (VRH) of charge carriers above and below 160 K, respectively. Above 160 K, the conductivity activation energies in the dark are found to be 0.28 and 0.15 eV in the temperature regions of 340-240 K and 230-160 K, respectively. In the temperature region of 110-150 K, the dark variable range hopping analysis revealed a density of localized states of 1.99x 10(22) cm(-3)eV(-1), an average hopping distance of 0.53 nm and an average hopping energy of 79.65 meV. When the sample was photo-excited, the values of the conductivity activation energies, the density of localized states near the Fermi level and the average hopping energy were observed to decrease sharply with increasing illumination intensity. On the other hand, the average hopping distance increased with rising illumination intensity. Such behaviours were attributed to the Fermi level shift and/or trap density reduction by electron-hole recombination. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimArticle Citation - WoS: 17Citation - Scopus: 17Trap Distribution in Tlins2 Layered Crystals From Thermally Stimulated Current Measurements(Korean Physical Soc, 2008) Isik, M.; Goksen, K.; Gasanly, N. M.; Ozkan, H.We have carried out thermally stimulated current (TSC) measurements with the current flowing along the layer on as-grown TlInS2 layered single crystals in the low temperature range 10 - 110 K with different heating rates of 0.1 - 1.5 K/s. Experimental evidence was found for the presence of two shallow electron trapping centers with activation energies of 12 and 14 meV. Their capture cross sections have been determined as 2.2 x 10(-23) and 7.1 x 10(-25) cm(2), respectively. It was concluded that retrapping in these centers is negligible, which was confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumed slow retrapping. An exponential distribution of electron traps was revealed from the analysis of the TSC data obtained at different light excitation temperatures. This experimental technique provided a value of 27 meV/decade for the trap distribution. The parameters of the monoclinic unit cell were determined by studying the X-ray powder diffraction.Article Citation - WoS: 1Citation - Scopus: 1Optoelectronic Properties of Tl3inse4 Single Crystals(Taylor & Francis Ltd, 2010) Qasrawi, A. F.; Gasanly, N. M.The crystal structure, temperature-dependent electrical conductivity, Hall coefficient, current-voltage characteristics, absorption spectra and temperature- and illumination-dependent photoconductivity of Tl3InSe4 single crystals were investigated. Tl3InSe4 crystallises in a body-centred lattice with tetragonal symmetry and belongs to the space group [image omitted]. The crystals are extrinsic p-type semiconductors and exhibit a conductivity conversion from p- to n-type at a critical temperature, Tc, of 283 K. They are observed to have Schottky diode properties in an Ag/Tl3InSe4/Ag Schottky barrier device structure. The absorption spectra displays two maxima, one related to an indirect energy band gap of 1.20 eV and another corresponding to exciton transitions. The photocurrent is observed to be strongly affected by the conductivity type of the crystal. The incident light intensity dependence of the photocurrent is found to be supralinear, linear and sublinear, indicating strong recombination at the surface, monomolecular recombination and bimolecular recombination, respectively, in the regions where the sample is p-type ([image omitted]), at [image omitted], and in the n-type region ([image omitted]). In the n-type region, the photocurrent increases with decreasing temperature down to 250 K, below which the photocurrent is temperature invariant. The change in recombination mechanism is attributed to the change in the behaviour of sensitising and recombination centres.
