We have developed a monolithic 512x512 element GeSi/Si heterojunction infrared focal plane array (FPA). The operation mechanism of the GeSi/Si heterojunction detector is the same as that of the PtSi/Si Schottky- barrier detector. We have fabricated the GeSi/Si heterojunction using molecular beam epitaxy (MBE) technology, and have confirmed that ideal strained GeSi films are grown on Si substrates. We have evaluated the dependencies of spectral responsivity on the Ge composition, impurity concentration and GeSi thickness, and have optimized them for 8-12 um infrared detection. The 512x512 element FPA has a pixel size of 34 x 34 um2 and a fill factor of 59%. A low noise equivalent temperature difference of 0.08 K ( f/2.0 ) was obtained with a 300 K background with a very small responsivity dispersion of 2.2%.
