Investigation of a multistack voltage-tunable four-color quantum-well infrared photodetector for mid- and long-wavelength infrared detection

A four-color quantum-well infrared photodetector (QWIP) for mid- and long-w avelength infrared (MWIR and LWIR) detection has been demonstrated in this work. Four stacks of QW structures with four different detection wavelength s are sandwiched between three highly doped contact layers. Peak detection wavelengths of this device are centered at 4.7, 8.5, 9, and 12.3 mu m, resp ectively. The 4.7- and 8.5-mu m stacks are separated from the 9- and 12.3-m u m stacks by a middle contact layer, and the peak detection wavelength wit hin these two double-stack QWIP's can be tuned by the applied bias. Four di fferent combinations of two-color simultaneous readings can be achieved. By using a small number of QW's and balancing the impedance between the stack s, rye are able to use all four stacks for voltage-tunable multicolor detec tion with two terminals. The bias and temperature dependence of the dark cu rrent and peak responsivity as well as the dynamic impedance in this four-c olor QWIP were systematically studied over a wide range of bias and tempera ture. In spite of using four different stacks of strained InGaAs-AlGaAs and GaAs-AlGaAs materials, the device shows excellent material quality and per formance.