NORMAL INCIDENCE HOLE INTERSUBBAND QUANTUM-WELL INFRARED PHOTODETECTORS IN PSEUDOMORPHIC GEXSI1-X/SI

The physics underlying normal incidence hole intersubband absorption in p-type semiconductor quantum wells is briefly reviewed. The fabrication and performance characteristics of a pseudomorphic Ge0.25Si0.75/Si p-type quantum well infrared photodetector on (001)Si are described. These devices show broadband response (8-14 mum) which is attributed to strain and quantum confinement induced mixing of heavy, light and split-off hole bands. Typical responsivity at lambda = 10.8 mum is 0.04 A/W over the 20-77 K temperature range. A detectivity D(lambda)* = 3.3 x 10(9) cm square-root Hz Watt-1, was measured at bias voltage of -2.4 V, for a temperature of 77 K, lambda = 10.8 mum and no cold-shield (i.e. T(cavity) = 300 K and an angular field of view theta = 180-degrees). Room temperature FTIR absorption measurements yield a peak absorption coefficient alpha(p) = 3914 cm-1 at lambda(p) = 8 mum, corresponding to a quantum efficiency eta = 3.1% at 300 K.