Normal incidence infrared photodetectors using intersubband transitions in GaSb L-valley quantum wells

We report on the demonstration of normal incidence (IR) detectors based on interconduction subband transitions in narrow GaSb/Ga0.6Al0.4Sb0.9As0.1 multiquantum wells in which L valley is the ground state. Strong IR absorption at 7.8 μm with an absorption coefficient of 9100 cm−1 and good photodetector response covering a wide spectrum region have been achieved. The orientation dependence of the absorption is also presented. Our results indicate the potential of this novel structure for use as normal incidence IR photodetectors.