High-temperature electrical properties of CdTe<Pb> crystals under Te saturation

Petro Fochuk 1Roman Grill 2Arunas Kadys 3Orest Parfenyuk 1Oleg Panchuk 1Kestutis Jarasiunas 3Peter Feychuk 1David Verstraeten 4

1. Chernivtsi National University (ChNU), 2 Kotsubinsky Str., Chernivtsi 58012, Ukraine
2. Charles University, Institute of Physics (FU UK), Ke Karlovu 5, Prague 121 16, Czech Republic
3. Vilnius University, Institute of Materials Science and Applied Research (IMSAR, VU), Sauletekio 9, building III, Vilnius LT-2040, Lithuania
4. Centre Spatial de Liège, Université de Liège, Avenue du Pré Aily,Angleurs, Liège 4031, Belgium

Abstract

CdTe is a very promising material for photorefractive devices, such as optical memory, holographic real time cameras, optical communication. Usually CdTe, doped by Ge or V, are used for these purposes. CdTe single crystals, grown in Chernivtsi University, ensure the largest gain factors known till now in all semiconductor photorefractives without applied electric field. Similar properties - conductivity of p-type and high resistivity - reveal CdTe<Pb> crystals and they can find an application in non-linear optics devices. But such material was investigated at low temperatures only. It is important to study the CdTe properties at high temperatures, where the point defect structure of semiconductor is formed.

The single crystals were grown by Bridgman technique. Pb concentration in the melt was 5×1018-5×1019 at/cm3. Hall effect measurements at 600-1100 K under well defined Te vapor pressure were performed. At 300 K all samples were of p-type conductivity with 40-70 cm2/Vs hole mobility. The dominant charge carriers were controlled by the EV+0.43 eV level. Under Cd saturation the samples gained n-type conductivity with lower electron concentration comparing to undoped CdTe. Measurements under Te vapour pressure demonstrated hole conductivity up to 600 K. After 900 K the conductivity became electronic. During heating-cooling cycles the p-n transition temperature shifts to higher values. The obtained results are explained using Kröger's quasichemical defect formation theory.

 

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium F, by Petro Fochuk
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-04-30 15:12
Revised:   2009-06-07 00:44