Formation of electrical contacts on CdTe crystals for x-ray detectors performance

Volodymyr A. Gnatyuk; Toru Aoki; Yoshinori Hatanaka; Olexandr I. Vlasenko

doi:10.1117/12.622637

21 September 2005 Formation of electrical contacts on CdTe crystals for x-ray detectors performance

Volodymyr A. Gnatyuk, Toru Aoki, Yoshinori Hatanaka, Olexandr I. Vlasenko

Proceedings Volume 5922, Hard X-Ray and Gamma-Ray Detector Physics VII; 59220I (2005) https://doi.org/10.1117/12.622637
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

The procedures of fabrication of electrical contacts and modification of their properties in high-resistivity CdTe:Cl crystals have been investigated to obtain diodes for nuclear radiation detectors. Excimer laser annealing was utilized to attain heavy In doping of the CdTe surface region. Using various preliminary treatments of the CdTe crystal surface and studying electrode vacuum deposition procedures and laser processing of CdTe crystals pre-coated with an In dopant film, the optimal conditions of fabrication of In/CdTe/Au diode structures were elaborated. It was considered that a Schottky barrier at the Au-CdTe contact was formed and a shallow built-in p-n junction at the In-CdTe interface arose as a result of both thermal In diffusion and effect of laser-induced shock waves under irradiation of the samples from the In-contact side. The In/CdTe/Au diodes had sharp I-V characteristics. Laser irradiation remarkably decreased the leakage current and increased the forward current. Moreover, the electrical properties of laser-formed p-n junctions were being improved after storage of the samples. The detectors showed a low leakage current (1-8 nA/cm² at 100 V and 300 K), optimal electrical barrier (0.72 eV) and high energy resolution (3.1 keV FWHM at 122 keV at γ-ray peak of Co-57). Variations in leakage currents and radiation detection properties of fabricated CdTe wafers and pixels diced from the wafers were associated with laser stimulated defect formation in the bulk of CdTe and generation of extended defects during the pixels performance. The regimes of injection and recombination in fabricated CdTe diodes have been analyzed.

Citation Download Citation

Volodymyr A. Gnatyuk, Toru Aoki, Yoshinori Hatanaka, and Olexandr I. Vlasenko "Formation of electrical contacts on CdTe crystals for x-ray detectors performance", Proc. SPIE 5922, Hard X-Ray and Gamma-Ray Detector Physics VII, 59220I (21 September 2005); https://doi.org/10.1117/12.622637

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