Gallium Sulfide Single Crystals Research Articles

TL and OSL studies on gallium sulfide (GaS) single crystals

Gallium sulfide (GaS) single crystals were investigated using thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements. TL experiments performed in the room temperature (RT)-450 °C range presented a glow curve consisting in six single discrete peaks. Analyses of TL glow curve by computerized glow curve deconvolution method showed that the trapping centers responsible for peaks are located at 0.98, 1.09, 1.15, 1.76, 1.87 and 1.90 eV. The order of kinetics found between 1 and 2 indicated the existence of general order of kinetics in TL process. Dose-dependent OSL measurements were performed in between 0.5 and 300 Gy. Taking into account the OSL response-dose relation, it was concluded that GaS single crystals may be a potential candidate as OSL dosimetric material in the 5 and 150 Gy range. Minimum detectable dose (MDD) value of the GaS single crystals were also determined using OSL signals. Furthermore, the reusability of GaS single crystals as dosimetric material and effect of fading with storage time were investigated.

Synthesis, growth and physical properties of silver gallium sulfide single crystals

The temperature oscillation method was used to synthesize dense single-phase polycrystalline AgGaS2 from high purity elements. AgGaS2 single crystal of 8mm diameter and 45mm length, free of voids and crack was obtained by the descending ampoule with steady ampoule rotation method using the synthesized polycrystalline charge. The grown crystal was subjected to powder X-ray diffraction and single crystal X-ray diffraction. The AgGaS2 has been studied using differential scanning calorimetry (DSC) technique. The single crystal has high transmission of 75% in the Mid IR region. The band gap energy was calculated using absorption spectrum. The stoichiometric composition of AgGaS2 was measured using energy dispersive spectrometry (EDAX). The structural and compositional uniformities of AgGaS2 were studied using micro-Raman scattering spectroscopy at room temperature. The photoluminescence behavior of AgGaS2 has been analyzed. It shows the maximum emission at 538nm. The resistivity of the grown single crystal has been measured.

Thermoluminescence in gallium sulfide crystals: an unusual heating rate dependence

Trap centres in gallium sulfide single crystals have been investigated by thermoluminescence measurements in the temperature range of 10–230 K. A curve-fitting method was utilized to evaluate the activation energies (52, 200 and 304 meV) of the revealed three trap centres. The heating rate dependence and trap distribution of the peaks have been studied using experimental techniques based on various heating rates and various illumination temperatures, respectively. An anomalous heating rate dependence of the high-temperature peak was found by carrying out TL measurements with various heating rates between 0.2 and 1.0 K/s. This behaviour was explained on the basis of a semi-localized transition model. Whereas normal heating rate dependence was established for low-temperature peak, that is, the TL intensity of the glow curve decreases and the peak maximum temperature shifts to higher values with increasing the heating rate. Moreover, a quasi-continuous trap distribution with the increase of activation energies from 52 to 90 meV, from 200 to 268 meV and from 304 to 469 meV for the observed three different traps was established employing the various illumination temperatures method.

Quantum efficiency coefficient for photogeneration of carriers in gallium sulphide singlecrystals

This paper presents investigations of the quantum efficiency coefficient for thephotogeneration of carriers in gallium sulphide (GaS) single crystals. Thereforethe spectral dependences (between 420 and 550 nm) of photoconductivity(σPC) were measured for temperatures from 80 to 333 K and for different light intensities. SinceσPC depends on the absorption and reflection coefficients, these parameters were determined in thesame range of temperatures. The least-squares method was applied to fit the experimentalσPC data with appropriate theoretical dependence. From this fitting, spectral dependences ofquantum efficiency coefficients for different temperatures and different light intensities wereobtained. A comparison of the values of absorption coefficient obtained from themeasurements of optical transmittance and from evaluation of the quantum efficiencycoefficient is presented.

The influence of light intensity on surface recombination in GaS single crystals

Gallium sulphide (GaS) is a layer structure semiconductor with relatively wide energy gap (Eg (295K)=2.5eV and Eg (80K)=2.62eV). It has potential applications in some areas of optoelectronics. This paper presents the investigations of the influence of light intensity on surface recombination velocity of charge carriers in GaS single crystals. To attain this purpose spectral dependences (between 420 and 550nm) of absorption coefficients, reflectivity coefficients and photoconductivity were measured in vacuum. The investigations were performed for various light intensities in several temperatures from 80 to 333K. The least square method was applied to fit the theoretical dependences of photoconductivity on wavelength and intensity of illumination at these temperatures. From the fittings the temperature and light intensity dependences of surface recombination velocity and bulk lifetime of charge carriers were obtained.

Optical and photoelectrical properties of lamellar gallium sulfide single crystals irradiated by γ-quanta

The influence of γ-quanta irradiation on photoelectrical and optical properties of lamellar GaS single crystals at different temperatures has been investigated. It is determined that the irradiation of pure crystals at the radiation dose equal to 30 krad results in the creation of shallow compensative acceptors, which are photoactive recombination centers (r-centers), and as a result of this both the photosensitivity and a luminescence connected with r-centers are increased. Irradiation with a radiation dose more than 100 krad results in the quenching of both photosensitivity and recombination luminescence due to formation of complexes (VGa VS). It is proposed that radiative recombination centers arising in the course of irradiation is conditioned by sulfur hole and interstitial gallium atoms.

Neutron irradiation defects in gallium sulfide: Optical absorption measurements

Gallium sulfide single crystals have been irradiated with different thermal neutron doses. Defects introduced by neutron irradiation turn out to be optically active, giving rise to absorption bands with energies ranging from 1.2 to 3.2 eV. Bands lying in the band-gap exhibit Gaussian shape. Their energies and widths are independent of the irradiation dose, but their intensities are proportional to it. Thermal annealing is completed in two stages, ending at around 500 and 720 K, respectively. Centers responsible for the absorption bands are proposed to be gallium-vacancy-galliuminterstitial complexes in which the distance between the vacancy (acceptor) and the interstitial (donor) determines the energy and intensity of the absorption band, as well as the annealing temperature.

Investigation of electronic properties of gallium sulfide single crystals grown by iodine chemical transport

Photoinduced-current-transient-spectroscopy and space-charge-limited-current measurements have been performed on n-type GaS single crystals grown from vapor by iodine chemical transport. Three electron traps located at 0.17, 0.45, and 0.56 eV from the conduction band have been detected, with a thermal capture cross section of 2×10−19, 5×10−14, and 8×10−13 cm2, respectively. Moreover, by Hall-effect measurements, an impurity hopping conduction with an activation energy of 0.12 eV has been evidenced in the range of temperatures between 220 and 320 K.

Intrashell Yb3+ Transitions in Gallium Sulphide Single Crystals

physica status solidi (b)Volume 118, Issue 1 p. K13-K16 Short Note Intrashell Yb3+ Transitions in Gallium Sulphide Single Crystals B. G. Tagiev, B. G. Tagiev Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this authorG. M. Niftiev, G. M. Niftiev Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this authorS. A. Abushov, S. A. Abushov Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this author B. G. Tagiev, B. G. Tagiev Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this authorG. M. Niftiev, G. M. Niftiev Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this authorS. A. Abushov, S. A. Abushov Institute of Physics, Academy of Sciences of the AzerbaidzhanSSR, Baku Search for more papers by this author First published: 1 July 1983 https://doi.org/10.1002/pssb.2221180157Citations: 8 pr. Narimanova 33, Baku 370143, USSR. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume118, Issue11 July 1983Pages K13-K16 RelatedInformation

Hopping conduction in gallium sulphide single crystals

The electrical conductivity of n-type GaS single crystals has been measured along the perpendicular to the c direction of the crystals. An excess of thermal activation energy and a frequency dependent conductivity in the direction parallel to the c axis of the crystal was observed. These effects were not observed in the p-type crystals. A hopping conduction in the n-type crystals along the c direction is inferred.

Hall-effect measurements on gallium-sulphide single crystals

Onn- andp-type GaS, Hall-effect measurements were carried out in a temperature range of (80÷600) °K, at the higher temperatures in the dark as well as under illumination. At the lower temperatures only photo-Hall effect could be measured because of the high dark resistance of the samples. The Hall mobility (magnetic field perpendicular to the layers) can be expressed asμH=12(T/T0)−2.4 cm2 V−1 s−1 for holes andμH=16(T/T0)−2.4 cm2 V−1 s−1 for electrons,T0=300 °K. An interpretation of these results with a scattering theory of Fivaz and Mooser yields a phonon energy of 0.05 eV. From infra-red-absorption measurements a fundamental peak is found at 0.04 eV; according to theoretical expectations this i.r. value should be smaller than 0.05 eV. Weak coupling of the carriers with the lattice as required by theory leads tome* > 1.5m0 andmh* > 2m. Thermoelectric power measurements carried out onn-type crystals by Kipperman and Sliepenbeek indicatedme* = 5m0.

Thermoelectric-power measurements on gallium-sulphide single crystals. Effective density of states

Thermoelectric-power measurements were carried out onn- andp-type samples GaS.n-type samples were measured in the range from room temperature to 550 °K,p-type samples only at 550 °K because of the high resistivity of thep-type samples. From the resultsNc was found to be of 1021 cm−3 at room temperature. This value is in disagreement with the theory of Fischer because when using this model an effective massme*=0.01m0 is found. The model of Fivaz yields a mass ofme*=5m0. Since the existence of a heavy effective mass of the electrons is also supported by the results of Hall measurements, the model of Fivaz seems to be the most appropriate.

Preparation, purity and electrical conductivity of gallium sulphide single crystals

Attempts to prepare polycrystalline gallium sulphide with a minimum impurity content are described. Spectrographic analyses of this material and the single crystals prepared from it by different techniques are presented. Dark conductivity measurements as functions of temperature up to 400 °C are carried out on various crystals. The measurements show differences in conductivity which depend on sample purity. For n-type samples an increase in the conductivity results from a diminished impurity concentration, while in the case of p-type crystals there is a decrease in conductivity. It is suggested that these changes are primarily due to a lower sodium content in the polycrystalline GaS used as starting material.

Photo-conductivity and photo Hall-effect measurements on gallium sulphide single crystals

Four-point photo-conductivity and Hall-effect measurements were carried out on n- and p-type gallium sulphide single crystals at room temperature. Some of the n-type samples show a superlinear region in the conductivity-lightintensity curve. The Hall-mobilities of n- and p-type samples under illumination were found to be 25 and 5 cm 2 V -1 s -1 respectively. Measurements of the anisotropy in conductivity yielded an order of magnitude of the ratio of the conductivities in the ab-plane and in the direction of the c-axis of 100.

Dark injection of holes into crystals of orthorhombic sulfur and of gallium sulfide

Oleum forms an injecting contact for holes with sulfur and gallium sulfide single crystals. Charge injection is preceded by the formation of sulfur radical ions in the surface of these crystals.