Temperature- and photo-excitation effects on the electrical properties of Tl₄Se₃S crystals

Abstract

The extrinsic energy states and the recombination mechanism in the Tl(4)Se(3)S chain crystals are being investigated by means of electrical and photoelectrical measurements for the first time. The electrical resistivity is observed to decrease exponentially with increasing temperature. The analysis of this dependence revealed three impurity levels located at 280, 68 and 48 meV. The photocurrent is observed to increase as temperature decreases down to a minimum temperature T(m) = 200 K. Below this temperature the photocurrent decreases upon temperature lowering. Two photoconductivity activation energies of 10 and 100 meV were determined for the temperature ranges below and above T(m), respectively. The photocurrent (I(ph)) versus illumination intensity (F) dependence follows the [Formula: see text] law. The value of γ decreases from ∼1.0 at 300 K to ∼0.34 at 160 K. The change in the value of γ with temperature is attributed to the exchange of roles between the monomolecular recombination at the surface near room temperature and trapping centers in the crystal, which become dominant as temperature decreases.

Recombination mechanisms in hydrogenated silicon nanocrystalline thin films

“…Figure 3b shows the variation of photocurrent with temperature at various light intensities in the range of 1.8-46.6 mW/cm 2 . For a given light intensity, the photocurrent appears to decrease with increasing temperature and follows the relation I ph ∝ e Ea/kT , where E a is the photoconductivity activation energy [4,5]. This result is commonly observed in amorphous silicon films at temperatures above 100 K and has been explained in terms of a thermal-quenching effect in which valence band tail traps are converted to dangling bond recombination centers induced by temperature or light [6,7].…”

“…As shown in Figure 6, the exponent (γ) starts at 0.83 at 290 K, falls to 0.50 at 340 K, and reaches 0.35 at about 380 K. The variation in gamma with temperature between 0.36 and 0.83 may be explained in terms of an exponential distribution of traps [4,[8][9][10] into the band gap. Rose [11] modeled the exponent γ to follow γ = T * / (T * + T ) , where T is the measurement temperature and T* is a characteristic temperature that represents the distribution of states in the gap.…”

“…While the photocurrent generally increases with increasing temperature over a wide temperature range, a photocurrent decrease with increasing temperature is reported for some temperature regions. These results were explained in terms of a thermal quenching effect, in which valence band traps are converted to recombination centers under light illumination at some temperatures [4][5][6][7]. Metal contacts and the formation of metal silicide regions at the contact interfaces play an important role in determining these properties.…”

Charge Transport Mechanisms in a Pb2P2Se6 Semiconductor

“…The presence of midgap states impacts the electrical properties of semi-insulating crystals. − Pb 2 P 2 Se 6 crystals with secondary phase inclusions exhibited nonlinear dark current–voltage ( I – V ) characteristics, consistent with an electrical breakdown behavior under an applied bias. In contrast, crystals without secondary precipitates exhibited a higher breakdown voltage.…”