Plasma induced type conversion in mercury cadmium telluride

Abstract

The tunable bandgap semiconductor mercury cadmium telluride (MCT) is by far the most efficient detector in the 3-5 mum mid-wave infrared (MWIR) and 8-14 mum long-wave infrared (LWIR) wave bands. It is the current material of choice for high-performance, low-cost infrared focal plane arrays. The present research effort in MCT is aimed at improving materials and device fabrication technology, to achieve high-temperature operation and multi-colour capability for MCT detectors. Plasma induced type conversion in MCT, as an alternative to ion implantation junction formation technology, has received considerable attention during the past few years. In this review, we discuss the salient features of this technology and we give a comparison of plasma and ion implantation junction formation technologies. The post-implant annealing, necessary in implantation technology to produce high-quality photodiodes, is not needed in plasma technology. The results on MWIR detectors demonstrate a state-of-the-art performance with a zero-bias dynamic resistance-junction area product R(0)A greater than 10(7) Omega cm(2) at 80 K. LWIR diodes have been successfully fabricated by using a hydrogenation process for vacancy doped wafers. An average R(0)A of 50 Omega cm(2) has been reported for these devices. The devices have been found to be stable when baked at 80 degreesC for ten days.