Numerical simulation models and stress measurements for mercury-cadium-telluride infrared detectors

Since first synthesized, Mercury-Cadmium-Telluride (HgCdTe) has facilitated the development of state of the art detectors in the short and mid infrared region of the infrared spectrum. As development of the material system continues to achieve high detection performance also in the long region of the infrared spectrum, new technological issues must be addressed and solved. One fundamental challenge arises in the formation of metal contacts for the interconnection of the focal plane array with Silicon based read-out circuits. Metal contacts have an intrinsic stress that will be transferred in the underlying semiconductor and potentially lead to the nucleation of dislocations. As a result, the reliability of the entire system can be jeopardized. To overcome this issue, it is imperative to develop stress characterization techniques that are currently lacking and develop a low stress metal contact.;HgCdTe represents a niche market within the global semiconductor industry and as a consequence little effort has been devoted to the development of numerical simulation models. Most of the device optimization is still performed using a trial and error approach or at most with rudimental one-dimensional simulations. On the contrary, more widely used material systems are enjoying the full benefits of a mature numerical simulation capability that allows a deeper understanding of current devices and the design of new and optimized ones. Such state of the art simulations enable considerable development cycle time and costs savings, leading to a more efficient utilization of available resources.;In this work a new stress measurement technique has been developed for the characterization of stress transferred in HgCdTe semiconductors due to metal contact layers. Using thin (<20 mum) HgCdTe cantilevers, the new measurement technique will allow the fabrication of new low stress contact for HgCdTe detectors in the long (8-14 mum) and very long region (14-30 mum) of the infrared spectrum.;Additionally, a new comprehensive three-dimensional modeling capability for HgCdTe infrared detectors has been developed for the design of optimized detectors and the prediction of device performance prior to fabrication. The material model and the simulation technology are currently being used by BAE Systems Inc. to design their focal plane arrays at their Lexington, MA, facility.