HgCdTe infrared detectors and focal plane arrays

Abstract

Recent advances in the areas of Mercury Cadmium Telluride (HgCdTe) material growth, detector array fabrication and Read Out Integrated Circuit (ROIC) design and fabrication have led to the demonstration of high resolution, low noise and large format reliable hybrid Infrared Focal Plane Arrays (IRFPAs). MBE HgCdTe based p-on-n planar heterostructure device fabrication has emerged as a viable technology for manufacturing high performance IRFPAs. Device quality MBE material is being grown routinely for applications in the 1-16 /spl mu/m spectral region. Excellent control of the composition, growth rate, layer thickness, doping concentration, dislocation density and transport characteristics has been demonstrated with a significant database. Control and flexibility of the MBE process have been proven by growing low defect density HgCdTe layers with varying bandgaps (SWIR, MWIR, MLWIR, LWIR and VLWIR), double and multiple layers, and structures that incorporate in situ grown CdTe passivation. A wide variety of submicron CMOS-based multiplexers have been designed, enabling fabrication of high performance advanced focal plane arrays with ultra-low read noise. Hybrid focal plane arrays, formed by cold welding of indium columns deposited on the detector and the ROIC, have been fabricated to suit a broad range of military, civilian and scientific applications. High performance HgCdTe/CdZnTe 256/spl times/256 and 640/spl times/480 focal plane arrays operating over a broad range of wavelengths, temperatures, and background radiation flux, have been produced. To mitigate issues associated with the thermal expansion coefficient mismatch between Si ROIC and CdZnTe substrate, growth of HgCdTe on alternate substrates such as Si and sapphire has been developed. This led to the demonstration of large (1024/spl times/1024) SWIR and MWIR HgCdTe FPAs. 2048/spl times/2048 FPAs are under development. Simultaneous two-color IR imaging has been proven feasible, using MBE in situ grown multilayer structures. This paper provides an overview of the status of HgCdTe materials, detectors and FPA technologies at Rockwell Science Center.