ULTRALOW DARK CURRENT P-TYPE STRAINED-LAYER INGAAS/INALAS QUANTUM-WELL INFRARED PHOTODETECTOR WITH BACKGROUND LIMITED PERFORMANCE FOR T-LESS-THAN-OR-EQUAL-TO-100 K

An ultralow dark current normal incidence p-type strained-layer In0.3Ga0.7Al/In0.52Al0.48As quantum well infrared photodetector (PSL-QWIP) grown on (100) semi-insulating InP substrate by molecular beam epitaxy technique for 8-12 mu m infrared detection was demonstrated for the first time. This PSL-QWIP shows background limited performance (BLIP) for T less than or equal to 100 K, which is the highest BLIP temperature ever reported for a QWIP. Due to a 1.5% lattice mismatch between the substrate and quantum well, a biaxial tensile strain was created in the In0.3Ga0.7As well layers. As a result, the light-hole state becomes the ground state for the free hole with small effective mass. The dramatic increase of optical absorption can be attributed to the large in-plane density of states and the small light-hole effective mass as a result of heavy- and light-hole state inversion. The dark current density and BLIP detectivity for this PSL-QWIP were found to be 7 x 10(-8) A/cm(2) and 5.9 x 10(10) cm-root Hz/W, respectively, at lambda(p)=8.1 mu m, V-b=2 V, and T=77 K.