A HIGH-STRAIN 2-STACK 2-COLOR QUANTUM-WELL INFRARED PHOTODETECTOR

A high strain two-stack, two-color, InGaAs/AlGaAs and AlGaAs/GaAs quan tum well infrared photodetector for midwavelength infrared (MWIR) and long wavelength infrared (LWIR) detection has been demonstrated. Each stack is designed to have detection in one of the two atmospheric wind ows, 3-5 mu m and 8-12 mu m, respectively. The MWIR stack has employed 35% of indium in the InGaAs well, which not only achieved peak wavele ngth at 4.3 mu m, but also obtained very high peak responsivity of R(p ) = 0.65 A/W, using 45 degrees light coupling. Normal incidence withou t grating coupling also has high responsivity with 40%-50% in the MWIR stack and 35%-45% in the LWIR stack, respectively, compared with the 45 degrees incidence, Despite the large in-plane compressive strain in duced by the high indium concentration, the device is highly uniform a nd has very low dark current in the MWIR stack. The background limited temperature is 125 K for the MWIR stack with a cutoff wavelength lamb da(c) = 4.6 mu m, and is 70 K for the LWIR stack with lambda(c) = 10 m u m. (C) 1997 American Institute of Physics.