Abstract
High-resistivity (CdZn)Te is a very promising material for X-ray and gamma-ray detectors capable of work at room temperature due to optimal energy bang-gap and high density. One of the main problems of preparation of high performance detectors is formation of stable electrical contacts.
Contact preparation is a complex of methods including surface treatment, metallization and surface passivation. Each step has to be optimized to eliminate leakage current, detector polarization and formation of oxide layer under electrical contact resulting in surface recombination.
The alcohol-based gold contacts are very promising electrical contacts since they do not allow formation of surface oxide layer unlike aqueous based gold chloride contacts in which the oxide layer forms. Another advantage of alcohol-based gold contacts is their higher adhesion to detector which reflects lack of oxide layer as well as different chemistry involved in contact creation.
Transport properties of CdZnTe detectors with alcohol based gold contacts is compared to another types of electrical contacts such as aqueous based gold contacts and evaporation. Laser induced transient current technique (L-TCT) is used for investigation of internal electric field, drift mobility, surface recombination and the dynamics of charge trapping and detrapping for the detector with different electrical contacts.
The main advantage of alcohol-based contacts is their lower leakage current resulting in less noise and higher possible operating voltage. This allows for faster charge collection and thus faster operation of a detector.
Electrical contact configuration with guard ring is used for the characterization of the leakage current and theoretical model based on the two-opposite connected Schottky diodes with shunted resistance is used for evaluation of contact properties.