Advanced Multi-Mode Seeker Technologies

"Avalanche photodetectors (APD) focal plane arrays (FPAs), with high sensitivity and large dynamic range are the most promising photodetectors for three dimensional imaging LADAR systems due to their low detectable powers and high performance. However, manypresent-day devices have poor bandwidths and noise properties because they exhibit comparable electron and hole impact ionization coefficients. We propose to fabricate two color APD FPA arrays for the detection of infrared wavelengths in the MWIR and LWIRranges (3-5, 8-14 microns).The device architecture proposed here could easily be adapted for other wavelength combinations by adjusting the composition of the absorber layers. Planar device structures are used to assure full resolution. The improveddetector properties result from the use of the semiconductor alloy Hg1-xCdxTe, which has substantially different electron and hole impact ionization coefficients and hence is uniquely suited to the task. The proposed work involves the use of the molecularbeam epitaxy (MBE) technique to grow high quality HgCdTe layers on silicon substrates. Innovative separate absorption and multiplication APD device architectures will be optimized to increase the speed and reduce the noise. APD devices will be fabricatedand tested to demonstrate their benefits. This effort will lay the groundwork for the production of multi-color APD FPAs suitable for enhanced target detection, on-board discrimination, an