Low temperature photoluminescence spectra of InS single crystals

Cataloged from PDF version of article.Photoluminescence (PL) spectra of InS were investigated in the wavelength region 477.5–860 nm and in the temperature range 8.5–293 K. We observed three PL bands centered at 605 nm (A-band), 626 nm (B-band) and 820 nm (C-band). The A- and B-bands are due to radiative transitions from the donor level at 0.01 eV below the bottom of the conduction band to the valence band and from the donor level at 0.06 eV below the bottom of the conduction band to the acceptor level 0.12 eV above the top of the valence band, respectively. The proposed energy-level scheme allows us to interpret the recombination processes in InS single crystals. Copyright © 1997 Published by Elsevier Ltd

Trap levels in layered semiconductor Ga2SeS

Cataloged from PDF version of article.Trap levels in nominally undoped Ga2SeS layered crystals have been characterized by thermally stimulated current (TSC) measurements. During the measurements, current was allowed to flow along the c-axis of the crystals in the temperature range of 10-300 K. Two distinct TSC peaks were observed in the spectra, deconvolution of which yielded three peaks. The results are analyzed by curve fitting, peak shape and initial rise methods. They all seem to be in good agreement with each other. The activation energies of three trapping centers in Ga2SeS are found to be 72, 100 and 150 meV. The capture cross section of these traps are 6.7 x 10(-23), 1.8 x 10(-23) and 2.8 x 10(-22) cm(2) with concentrations of 1.3 x 10(12), 5.4 x 10(12) and 4.2 x 10(12) cm(-3), respectively. (C) 2004 Elsevier Ltd. All rights reserved

Temperature dependence of the Raman-active phonon frequencies in indium sulfide

Cataloged from PDF version of article.The temperature dependence of the Raman-active mode frequencies in indium sulfide was measured in the range from 10 to 300 K. The analysis of the temperature dependence of the A(g) intralayer optical modes show that Raman frequency shift results from the change of harmonic frequency with volume expansion and anharmonic coupling to phonons of other branches. The pure-temperature contribution (phonon-phonon coupling) is due to three- and four-phonon processes. (C) 1999 Elsevier Science Ltd. All rights reserved

Temperature dependence of the first-order Raman scattering in GaS layered crystals

Cataloged from PDF version of article.The temperature dependence (15-293 K) of the six Raman-active mode frequencies and linewidths in gallium sulfide has been measured in the frequency range from 15 to 380 cm(-1). We observed softening and broadening of the optical phonon lines with increasing temperature. Comparison between the experimental data and theories of the shift and broadening of the interlayer and intralayer phonon lines during the heating of the crystal showed that the experimental dependencies can be explained by the contributions from thermal expansion and lattice anharmonicity. The pure-temperature contribution (phonon-phonon coupling) is due to three- and four-phonon processes. (C) 2000 Elsevier Science Ltd. All rights reserved

Low temperature photoluminescence spectra of layered semiconductor TlGaS2

Cataloged from PDF version of article.Photoluminescence (PL) spectra of TlGaS2 layered single crystals were studied in the wavelength region 500-860 nm and in the temperature range 9.5-293 K. We observed a total of three PL bands centered at 568 nm (2.183 eV, A-band), 718 nm (1.727 eV, B-band) and 780 nm (1.590 eV, C-band) at various temperatures. We have also studied the variations of the A- and B-band intensities vs excitation laser density in the range from 7 × 10-2 to 9 W cm-2. The A- and B-bands were found to be due to radiative transitions from the deep donor levels located at 0.362 and 0.738 eV below the bottom of the conduction band to the shallow acceptor levels at 0.005 and 0.085 eV located above the top of the valence band, respectively. The proposed energy-level diagram permits us to interpret the recombination processes in TlGaS2 layered single crystals. © 1997 Elsevier Science Ltd

Thermally stimulated currents in layered Ga4SeS3 semiconductor

Cataloged from PDF version of article.Thermally stimulated current (TSC) measurements are carried out on nominally undoped Ga4SeS3 layered semiconductor samples with the cur-rent flowing along the c-axis in the temperature range of 10 to 150 K. The results are analyzed according to various methods, such as curve fitting, initial rise and Chen's methods, which seem to be in good agreement with each other. Experimental evidence is found for the presence of three trapping centers in Ga4SeS3 with activation energies of 70, 210 and 357 meV. The calculation yielded 7.9 x 10(-21), 7.0 x 10(-19) and 1.5 x 10(-13) cm(2) for the capture cross section, and 1.6 x 10(10), 6.5 x 10(10) and 1.2 x 10(11) cm(-3) for the concentration of the traps studied. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Donor-acceptor pair recombination in AgIn5S8 single crystals

Cataloged from PDF version of article.Photoluminescence (PL) spectra of AgIn5S8 single crystals were investigated in the 1.44-1.91 eV energy region and in the 10-170 K temperature range. The PL band was observed to be centered at 1.65 eV at 10 K and an excitation intensity of 0.97 W cm(-2). The redshift of this band with increasing temperature and with decreasing excitation intensity was observed. To explain the observed PL behavior, we propose that the emission is due to radiative recombination of a donor-acceptor pair, with an electron occupying a donor level located at 0.06 eV below the conduction band, and a hole occupying an acceptor level located at 0.32 eV above the valence band. (C) 1999 American Institute of Physics

Trap levels in layered semiconductor Ga 2 SeS

Abstract Trap levels in nominally undoped Ga 2 SeS layered crystals have been characterized by thermally stimulated current (TSC) measurements. During the measurements, current was allowed to flow along the c-axis of the crystals in the temperature range of 10-300 K. Two distinct TSC peaks were observed in the spectra, deconvolution of which yielded three peaks. The results are analyzed by curve fitting, peak shape and initial rise methods. They all seem to be in good agreement with each other. The activation energies of three trapping centers in Ga 2 SeS are found to be 72, 100 and 150 meV. The capture cross section of these traps are 6.7!10 K23 , 1

Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure

In this work we report on Hall effect, resistivity and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about -105 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both 3D and 2D electrons, the increase rate being higher for 2D electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium cloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.Comment: 18 pages, Latex, 10 postscript figure