Peak response wavelengths of p- and n-type InxGa1-xAs-InP quantum well infrared photodetectors

p- and n-type InxGa1-xAs-InP quantum wells are suitable for multi-color infrared photodetector applications in atmospheric windows due to improved barrier quality and carrier-transport properties. We apply the k ·p method to study the energy band structures and optical transition properties, which show that the peak response wavelengths of p- and n-type InxGa1-xAs-InP quantum well infrared photodetectors (QWIPs) are determined not only by the energy distance from the ground sublevels in the quantum well to the energy band edges of extended states, but also by the characteristics of the extended states. The optical phonon scattering process converts the broad absorption spectrum of the p-QWIP from 0 to 16 μm into a short-wavelength spectrum centered at 4.5 μm. The transport of electrons in the extended states of the n-QWIP is characterized by running wave boundary conditions, resulting in a theoretically optimal absorption rate by a 8-nm-thick In0.53Ga0.47As quantum well. Moreover, a conduction-band offset of 0.5 for an InxGa1-xAs-InP (x=0.53) heterostructure gives the best data fitting of theoretical and experimental response peaks, whereas 0.55 is generally recommended in the literature.