Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 35: II-VI semiconductors III

HL 35.7: Vortrag

Mittwoch, 29. März 2006, 16:00–16:15, POT 151

DX-Centers in Indium doped CdTe: Electrical characterization and PAC study — •M. Türker, J. Kronenberg, M. Deicher, H. Wolf, and Th. Wichert — Technische Physik, Universität des Saarlandes, D-66041 Saarbrücken

In CdTe, donors like Indium can be electrically compensated by vacancies present in the Cd sublattice (V_Cd) either by the formation of A-centers (In-V_Cd pairs, [1]) or DX centers. For In concentrations exceeding 10¹⁸ cm⁻³, DX centers are created by the relaxation of the In donor towards an interstitial lattice site thereby generating a neighboring Cd vacancy [2]. This relaxation should create an electric field gradient (EFG) observable by perturbed γγ angular correlation (PAC) using ¹¹¹In/¹¹¹Cd. An EFG assigned to the DX defect (ν_Q=21 MHz, η=0) has been observed earlier [3]. Characteristic for DX centers is a metastable state formed by illumination at low temperatures, where the In donor relaxes back to a substitutional site leading to an increased persistent photoconductivity (PPC) [2]. We performed PAC and conductivity measurements as a function of temperature with and without illumination. Below 150 K, the samples show a PPC effect with about 20% increase of the carrier concentration. This effect is not accompanied by any changes of the PAC spectra recorded with the same samples. Possible explanations of the observed EFG will be discussed.

Supported by BMBF under contract no. 05KK1TSB/5.

[1] Th. Wichert, T. Krings and H. Wolf, Physica B 185 (1993) 297

[2] C.H. Park and D.J. Chadi, Phys. Rev. B 52 (1995) 11884

[3] S.Lany, H.Wolf and Th. Wichert, Phys. Rev. Lett 92 (2004) 225504