Electroless Gold Contact Deposition on CdZnTe Detectors by Scanning Pipette Technique

CdZnTe is one of the most exploited materials for the realization of room temperature X- and gamma- ray detectors. However the final cost of the devices remains a limiting factor for large-scale applications. One of the problems is connected with the realization of contacts. Due to the difficulty to obtain large single wafers, usually photolithography is carried out for each single device, strongly increasing the cost of detector fabrication. On the other side because of the important role played by the metal-CZT interface on the functioning of the final device, a special attention should be paid to the technology employed in the realization of metal contacts. Recently, a novel, reproducible and low-cost method for gold deposition on CZT surface has been developed [1] combining two different technologies: scanning pipette technique and electroless deposition. With this technique it is possible to avoid the photolithography process and still obtain complex contact patterns with a good spatial resolution and high reproducibility. In this work, it is shown that contacts with dimensions down to a few tenths of microns can be obtained. The contacts show good mechanical stability and optimal current-voltage characteristics. High-resolution CZT detectors have also been demonstrated by the use of this technology. Moreover, the technology is shown to be easily adapted to the deposition of other metals than gold, for example platinum or palladium, by simply changing the deposited solution.