Thermoelectrically Cooled MWIR Avalanche Photodiodes on Silicon Substrates

MWIR avalanche photodetectors (APDs) are required in modern Air Force weapons systems to detect, recognize and track stationary and mobile targets under various atmospheric conditions against complex backgrounds. Theoretical and experimental results point toward HgCdTe as the material of choice for fabricating these devices, due to its low ratio of impact ionization coefficients. In Phase I we performed optical and electrical measurements to demonstrate the operation of MWIR HgCdTe PnN APDs up to 120K. Both absorption and multiplication took place in the low-doped n-type layer. For improved gain-bandwidth, lower excess noise properties and higher operating temperatures, separate absorption and multiplication (SAM) structures are necessary. Recent developments in molecular beam epitaxial (MBE) growth and monitoring techniques allow the growth of such HgCdTe multilayer heterostructures. We propose in this Phase II program to use our extensive experience in MBE growth and device processing to fabricate SAM thermoelectrically cooled MWIR HgCdTe APDs. Based on the success of the Phase I effort we plan to use silicon as the substrate material. EPIR Technologies would lead this effort with the responsibility for the optimization and growth of HgCdTe heterostructures with the desired properties for APD fabrication. The University of Illinois at Chicago will perform the device fabrication and characterization.