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-wavelength infrared (MWIR and LWIR) detection has been demonstrated in this work. Four stacks of QW structures with four different detection wavelengths 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 /spl mu/m, respectively. The 4.7- and 8.5-/spl mu/m stacks are separated from the 9- and 12.3-/spl mu/m stacks by a middle contact layer, and the peak detection wavelength within these two double-stack QWIP's can be tuned by the applied bias. Four different combinations of two-color simultaneous readings can be achieved. By using a small number of QW's and balancing the impedance between the stacks, we are able to use all four stacks for voltage-tunable multicolor detection with two terminals. The bias and temperature dependence of the dark current and peak responsivity as well as the dynamic impedance in this four-color QWIP were systematically studied over a wide range of bias and temperature. In spite of using four different stacks of strained InGaAs-AlGaAs and GaAs-AlGaAs materials, the device shows excellent material quality and performance.