Well-width and doping-density dependence of 1.35 μm intersubband transition in InGaAs/AlAsSb quantum wells

We report 1.35 μm intersubband absorption, in InGaAs/AlAsSb multiquantum wells, obtained by introducing a one monolayer AlAs layer at the well-barrier interface. The observed peak covers the useful communication wavelength range of 1.2–1.6 μm. Polarization-resolved, room-temperature absorption spectra and 77 K photoluminescence spectra measured on a series of samples reveal this short wavelength intersubband absorption peak (≈1.35 μm) in 7 and 9 monolayer wells that are doped in the well region to a density ⩽2×1018 cm−3. For heavier doping and in narrower wells, we do not observe this transition.