Persistent photoconductivity and DX centers in Cd0.8Zn0.2Te:Cl

Abstract

Transport measurements on large single crystals of Cd0.8Zn0.2Te:Cl indicate that Cl donors form DX centers in CdZnTe. We have observed persistent photoconductivity (PPC) with an annealing temperature Ta≊130 K. Hall-effect experiments indicate that the PPC arises from a persistent increase in the density of charge carriers; the saturation density is Nsat=6×1016 cm−3. The deep binding energy of the DX center is Ed=0.22 eV.

Deep donors inCd1−xZnThio1, Bennett2, Becla3 1996Phys. Rev. BSelf Cite

“…It is annealed in a wide transition, centered around T a ϭ130 K. 8 The temperature dependence of N(T) follows that of (T), indicating that the PPC is the result of a persistent increase in the carrier concentration. Below T a , the density is N sat ϭ(6Ϯ1)ϫ10 16 cm Ϫ3 , independent of T.…”

“…4, rises rapidly at low T, indicative of the presence of localized states near the band edge; at high T it reaches a saturation value ϭ500 cm 2 /V s. Its temperature dependence is similar to that of the xϭ0.20 sample. 8 Note that (T) is independent of temperature in the range 100ϽTϽ190 K; the temperature dependence of (T) in this range is therefore entirely due to the temperature variation of N(T). However, neither (T) nor FIG.…”

Study of DX center in Cd0.8Zn0.2Te:Cl by positron annihilation

“…The results we obtained using positron annihilation techniques in this study are in good agreement with those from Hall effect measurements and thermoelectric effect current measurements. 10,11,16 In these measurements, the DX center concentration of ϳ6.0ϫ10 16 cm Ϫ3 was deduced indirectly by measuring the free electron concentration in the conduction band when the DX centers were photoexcited to their metastable d ϩ states.…”

“…However, in II-VI semiconductor compounds, where DX centers show properties similar to those in AlGaAs, 8,9 much higher annealing temperatures of DX centers can be obtained. 10,11 Although some optical, electrical, and microscopic structure properties of DX centers have been studied extensively, not many direct observations giving information about the concentration, charge states, and microstructures of DX centers in Cd 0.8 Zn 0.2 Te:Cl have been reported.…”

“…We also show that, in comparison to the Hall effect or thermo-electrical effect measurements, the concentration of DX centers can be more directly determined, where free carrier concentrations were measured to deduce the DX center concentration after they had been excited to d ϩ states. 10,11,16…”