Hall effect, space-charge limited current and photoconductivity measurements on TlGaSe₂layered crystals

Abstract

TlGaSe 2 layered crystals are studied through dark electrical conductivity, Hall mobility, space-charge limited current and illumination-and temperature-dependent photoconductivity in the temperature ranges 120-350 K, 220-350 K, 260-350 K and 120-350 K, respectively. The Hall effect measurements revealed the extrinsic p-type conduction. The Hall mobility increase with decreasing temperature is limited by the thermal lattice scattering. The space-charge limited current and dark conductivity measurements predicted the existence of a single discrete trapping level located at 330 meV with a trap concentration of (1.4-2.2) × 10 13 cm −3 . The dark electrical conductivity and photoconductivity measurements reflect the existence of three other energy levels located at 95, 46 and 26 meV at high, moderate and low temperatures, respectively. The photocurrent is observed to increase with increasing temperature up to a maximum temperature of 320 K. The illumination dependence of photoconductivity is found to exhibit sublinear, linear and supralinear recombinations at high, moderate and low temperatures, respectively. The change in recombination mechanism is attributed to the exchange in the behaviour of sensitizing and recombination centres.

Phase diagram of the TlGaS2–CdS system and optical properties of a TlGaS2:Cd2+ crystal

“…Both parameters, the steepness and Urbach energy, increase with the sample temperature in the range 100-300 K (Table 1). These results are consistent with data reported in the literature [28,[35][36][37][38].…”

“…To estimate the bandgap energy for indirect (E gi ) and direct (E gd ) allowed transitions, the lines (αhν) 1/2 = f(hν) and (αhν) 2 = f(hν) were extrapolated to (αhν) 1/2 = 0 and (αhν) 2 = 0 (Figs. 5,6) [33][34][35].…”

Photovoltaic Effect and Space Charge Limited Current Analysis in TlGaTe2Crystals

“…The existence of this trap level may be attributed to the vacancies of Tl, Ga or Te atoms in the crystals. Similar behavior of J−V characteristics at similar temperatures (260340 K) with E t = 0.33 eV and N t = (1.4−2.2) × 10 13 cm −3 was also reported for TlGaSe 2 layered crystals [17].…”

Optoelectronic and electrical properties of TlGaS2 single crystal

“…Paper centers. On the other hand, when sensitizing centers change their behavior from recombination centers to traps at fixed illumination intensity thermal activation of photocurrent is observed [23,24].…”