Electrical and Optical Properties of TlGaSe₂ and TlGaSe₂:Co Single Crystals

Abstract

Optical absorption and dielectric properties have been investigated for TlGaSe2 and TlGaSe2: Co single crystals grown by Bridgman method. The temperature dependence of the exciton peak position in TlGaSe2 showed the anomalies at 50 K, 90 K, 107 K and 120 K. The dielectric anomalies of TlGaSe2 are found which exhibit structural phase transitions (PT) at T 2=107 K and T 1=120 K corresponding to first-order and second-order PT, respectively. It is found that an increase in concentration of Co impurity leads to shift of two phase transition points (T 1 and T 2) towards the lower temperature and changes the dielectric properties for TlGaSe2: Co. The impurity absorption bands observed in TlGaSe2: Co are attributed to the electronic transitions between the split energy levels of Co2+ ions with tetrahedral (T d) symmetry in TlGaSe2 host lattice.

Excitation intensity and temperature‐dependent photoluminescence and optical absorption in Tl4Ga3InSe8 layered crystals

“…[2][3][4][5][6]. It was established that the fundamental absorption edge is formed by indirect and direct transitions with E gi = 1.96 and 2.07 eV, E gd = 2.11 and 2.19 eV at T = 300 and 10 K, respectively.…”

Low-temperature visible photoluminescence spectra of TlGaSe2 layered crystal

“…Recently, we have studied the photoluminescence (PL) of TlGaS and TlInS single crystals [6,7], and observed broad emission bands, which we have attributed to donor}acceptor pair recombination. In the present paper, we report the results of the PL investigation of single crystals of TlGaSe , which has a band gap of E "2.187 eV at ¹"8.5 K and dE /d¹"!2;10\ eV/K [8,9]. The PL investigation is conducted within the 600}700 nm wavelength, 0.2}15.2 W cm\ excitation laser intensity, and in the 8.5}35 K temperature range.…”

Thermally stimulated current observation of trapping centers in an undoped Tl4Ga3InSe8 layered single crystal

“…At this point, it is worthwhile to compare the present results with those obtained in our previous study of Tl 4 Ga 3 InSe 8 crystal using PL spectroscopy, which yielded a level at 30 meV [8]. This energy level was obtained from the temperature dependence of the PL intensity.…”

“…Optical and photoelectrical properties of TlGaSe 2 crystal were studied in Ref. [2][3][4][5][6]. A high photosensitivity in the visible range of spectra, high birefringence in conjunction with a wide transparency range of 0.6-16 µm make this crystal useful for optoelectronic applications [7].…”