Relaxation phenomena in TlGa0.99Fe0.01Se2 single crystals

Abstract

The relaxation electronic phenomena occurring in TlGa0.99Fe0.01Se2 single crystals in an external dc electric field are investigated. It is established that these phenomena are caused by electric charges accumulated in the single crystals. The charge relaxation at different electric field strengths and temperatures, the hysteresis of the current-voltage characteristic, and the electric charge accumulated in the TlGa0.99Fe0.01Se2 single crystals are consistent with the relay-race mechanism of transfer of a charge generated at deep-lying energy levels in the band gap due to the injection of charge carriers from the electric contact into the crystal. The parameters characterizing the electronic phenomena observed in the TlGa0.99Fe0.01Se2 single crystals are determined to be as follows: the effective mobility of charge carriers transferred by deep-lying centers μf=5.6×10−2 cm2/(V s) at 300 K and the activation energy of charge transfer ΔE=0.54 eV, the contact capacitance of the sample C c =5×10−8 F, the localization length of charge carriers in the crystal d c =1.17×10−6 cm, the electric charge time constant of the contact τ=15 s, the time a charge carrier takes to travel through the sample t t =1.8×10−3 s, and the activation energy of traps responsible for charge relaxation ΔE σ = ΔE Q = 0.58 eV.