Control of Dislocations for Improved IR Sensors Using Epitaxial Necking

It is well established that in order to produce large-format LWIR HgCdTe FPAs for third-generation IR systems, Si substrates must be used. In the DoD Militarily Critical Technologies List (December 2005), HgCdTe/Si is listed as a critical material and achieving an etch pit density (EPD) < 1x106 cm-2 is identified as a critical technology parameter. Thus it is imperative that a manufacturable technique to control EPD in HgCdTe/Si be demonstrated. In this Army STTR program, Agiltron, Rensselaer Polytechnic Institute, and Raytheon Vision Systems will fabricate LWIR HgCdTe/Si FPAs by producing low-defectivity HgCdTe films on lattice-mismatched Si substrates. Employing the innovative epitaxial necking technique, the defect density of the HgCdTe/Si films will be lowered to levels found in HgCdTe/CdZnTe films. Building on the achievements of Phase I, the objectives for Phase II are (i) to produce CdTe/Si substrates with a threading dislocation density (TDD) of less than 2x105 cm-2 and (ii) to demonstrate LWIR HgCdTe FPAs on CdTe/Si substrates with performance comparably equivalent to HgCdTe FPAs on lattice-matched CdZnTe substrates. Agiltron will deliver to NVESD one packaged 256x256 LWIR HgCdTe/Si FPA at the end of Phase II.