The effect of strain in InP/InGaAs quantum-well infrared photodetectors on the operating wavelength

We report on InP/InGaAs quantum-well infrared photodetectors (QWIPs) that cover the spectral range from 8 to 11 μm. The only previously reported operating wavelength for QWIPs of the same material system was around 8 μm. The higher operating wavelengths were achieved by including the strain as an additional band gap engineering parameter. According to our calculations, the InP/InGaAs lattice-mismatched multiple quantum well structures are suitable for design QWIPs covering the 5.5–11 μm range. We demonstrate five different QWIP structures with bound-to-bound and bound-to-continuum transitions for photodetection in the 8–12 μm atmospheric window. The calculations are in very good agreement with the experimental data. We found that the InP/InGaAs material system is more flexible than GaAs/AlGaAs because it has an additional degree of freedom—the strain for band gap engineering design.