Schottky Barrier and Aging Effect studies in Au(Cu)/p-CdTe Contacts

Yevgen O. Bilevych 1Andriy V. Sukach 1Volodymyr V. Tetyorkin 1Volodymyr M. Popov 2

1. Institute of Semiconductor Physics NAS Ukraine, Kyiv, Ukraine
2. Physical and Technological Research and Certification Centre "Microanalitics" (PTRCCM), 3 Severo-Siretskaya, Kyiv 04136, Ukraine

Abstract

CdTe is regarded as a promising material for X-ray detectors. Knowledge of the Schottky barrier formation in p-CdTe is insufficient. Partly it can be explained by such intrinsic physical properties of p-CdTe as low temperature conductivity, instable surface and poor mechanical characteristics.
In order to clarify possible mechanisms of the Schottky barrier formation the influence of the surface treatment on physical properties of Au(Cu)/p-CdTe contacts were investigated. The contacts to p-CdTe were prepared on (110) CdTe single crystals with hole concentration p=(6-10)*1015 cm-3 and Hall mobility 80-120 cm2/Vs. The surfaces were prepared by wet chemical etching prior to metallization using etchants composed from three components. In sum, seven etchants were investigated. The barrier height was determined from the photoemission current measurements. SIMS and SEM measurements have been carried out to characterize compositional structure at the interface before and after aging.
In freshly prepared contacts SIMS measurements demonstrate pronounced deviation from the stoichiometry at the interfaces caused by wet chemical etching. The multi-level pinning of the Fermi level at the metal-CdTe interface was experimentally observed in these contacts. It has been found that the barrier height can be regulated in a wide range of energies for surfaces treated in different etchants (from approximately 0.2 eV up to 0.8 eV when measured from the valence band maximum).
Photoemission current and SIMS profile measurements were performed in freshly prepared, six-month and one-year old contacts in order to study aging effects. The barrier height has been found to change substantially during the storage of contacts under normal laboratory condition. In one-year old contacts only two barriers close to 0.6 eV and 0.8 eV were observed in investigated contacts. Experimental results are discussed in terms of formation of native defects at the interface caused by surface treatment.

 

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Presentation: poster at E-MRS Fall Meeting 2003, Symposium A, by Yevgen O. Bilevych
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-10 13:50
Revised:   2009-06-08 12:55