Electrical properties of CdTe:Br single crystals at high temperature
|Petro Fochuk 1, Yevheniya Verzhak 1, Roman Grill 2, Oleg Panchuk 1|
1. Chernivtsi National University (ChNU), 2 Kotsubinsky Str., Chernivtsi 58012, Ukraine
The crystals were grown by the Bridgman method and contained 3*1019 at/cm3 of Bromine in the melt. Hall effect measurements were performed under well-defined Cd/Te vapor pressure at ~600-1200 K using the 6 contacts method. Temperature, component vapor pressure and temporal dependencies of specific conductivity, charge carrier density and their mobility were studied.
The electron density ([e-]) at RT in as-grown samples varied from 1010 till 1017 cm-3 but after heating above 800 K it became essentially higher than in undoped CdTe, sometimes exceeding 1018 cm-3 at T>1100 K. It didn’t depend on the Cd vapor pressure (PCd) till 1000 K and increased at higher temperature with PCd increasing. In heavily doped samples after heating above 900 K the [e-] was above 1017 cm-3 and constant in a wide temperature range (500-1100 K). The electron mobility in CdTe:Br crystals usually was lower comparing with undoped CdTe due to the high concentration of dopants atoms. It was impossible to reduce the [e-] sufficiently by PCd reducing or quenching. Only the treatment at Te saturation allowed decreasing the [e-] more than 6 orders of magnitude (at RT). The observed strong self-compensation phenomena are discussed in the framework of the Krogers’ quasichemical point defect theory assuming the presence in the samples of a large quantity of dopant acceptors (Bromine associates with Cd vacancies) and dopant donors (BrTe).
Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Petro Fochuk
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-11 13:52 Revised: 2009-06-07 00:48
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