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Evaluation of deep-impurity governed photoelectrical properties in differently doped CdTe

Arunas Kadys 1Markas Sudzius 1Kestutis Jarasiunas 1Petro Fochuk 2Petro Feychuk 2Marie L. Hellin 3David Verstraeten 3

1. Institute of Material Science and Applied Research, Sauletekio 9, III bld., Vilnius LT-10222, Lithuania
2. Department of Inorganic Chemistry, Chernivtsi National University, Kotziubynskoho str. 2, Chernivtsi 58012, Ukraine
3. Centre Spatial de Liège, Université de Liège, Avenue du Pré Aily, Angleurs 4031, Belgium


Fast response and high sensitivity in the near-IR region makes II-VI compounds the promising semiconductor materials for telecommunication, adaptive optics, and real time holographic devices. Defect engineering efforts are ongoing for selection of an appropriate deep midgap dopant, optimization of its density, electrical activity, and to achieve technological reproducibility.

We investigated nonequilibrium carrier generation, transport, and recombination processes in differently doped CdTe crystals. Doping by Ge, Pb, Sb, Se, Si, or Sn was reached by Bridgman-growth, whereas vanadium doped CdTe ingots were grown by the vertical Bridgman-Stockbarger method. The samples were excited by 23 ps laser pulses at 1064 nm wavelength to ensure nonequilibrium carriers generation from deep levels. Time-resolved four-wave mixing technique enabled us to study peculiarities of carrier generation, trapping, and transport in light-created space charge (SC) field, and to determine the photoelectric parameters such as photo-generated carrier lifetime, diffusion coefficient. We measured the SC-field dependent diffusion coefficient values at various excitation energies and determined the sign of the photogenerated excess carriers. The experiments revealed that in samples doped with V, Sb, Si, or Ge, the majority carriers are electrons, while in Pb, Se, Sb, Ge (cut from the different place of an ingot), or Sn-doped crystals - the holes. Very strong feed-back effect of the internal electric SC field to subnanosecond free carrier dynamics was observed in the crystals doped with Ge, Pb, Sb, or Sn. The crystals doped with Ge, Sb, or Sn revealed longer than 40 ns carrier lifetimes together with long living SC field component, what makes them very promising photorefractive media for real time holographic devices.


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

Submitted: 2006-05-15 11:40
Revised:   2009-06-07 00:44