Widely Separate Spectral Sensitivity Quantum Well Infrared Photodetector Using Interband and Intersubband Transitions

Recent commercial and military infrared sensors have demanded multispectral capabilities, high sensitivity and high selectivity, usually found in quantum well infrared photodetectors (QWIPs). This paper presents the design and characterization of a three-band QWIP capable to detect simultaneously near infrared (NIR), mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR), using interband and intersubband transitions. Separate readouts provide the flexibility to optimize each band detection by allowing the application of different bias voltages. The quantum well structure was designed using a computational tool developed to solve self-consistently the Schrodinger-Poisson equation with the help of the shooting method. The detector comprises of three different stacks of uncoupled (wide barriers) quantum wells that combine AlGaAs, GaAs, and InGaAs, separated by contact layers, grown by molecular beam epitaxy (MBE) on a GaAs substrate. The spectral responses in all three bands were measured using a standard photocurrent spectroscopy setup with light coupling via a 45 facet. The measured photoresponse showed peaks at 0.84, 5.0, and 8.5 wavelengths with approximately 0.8, 0.03, and 0.12 A/W peak responsivities for NIR, MWIR, and LWIR bands, respectively. A good agreement between the measured and simulated figures of merit shows the possibility to improve and tailor the detector for several applications with low computational effort. Finally, this work has demonstrated the possibility of detection of widely separated wavelength bands using interband and intersubband transitions in quantum wells.