Gas source molecular-beam epitaxial growth of normal incidence GaAs/AlGaAs quantum well infrared photodetectors

Normal incidence illumination of long wavelength quantum well infrared photodetectors is demonstrated for the first time by using hole intersubband absorption in the GaAs valence band without diffraction gratings. The strong mixing between the heavy and light holes at k≠0 allows the desirable normal incidence illumination geometry to be used. Grown by gas source molecular beam epitaxy, a normal incidence quantum efficiency of η=28% and detectivity of D*λ = 3.1 × 1010 cm√Hz/W at 77 K for a cutoff wavelength λc = 7.9 μm have been achieved.