1.45 μm intersubband absorption in InGaAs/AlAsSb grown by molecular beam epitaxy

InGaAs/AlAsSb multi-quantum wells lattice matched to InP substrates have been grown by molecular beam epitaxy, and the intersubband transitions in doped quantum welts have been studied. By precisely controlling the As to Sb flux ratio and substrate temperature, fairly abrupt interfaces with 1-2 monolayers of compositionary varying layers in both heterointerfaces have been achieved as confirmed from the high-resolution transmission electron microscopy (HRTEM) lattice images. Polarization-resolved absorption spectra were measured either with a conventional optical absorption measurement system or a Fourier-transform infrared spectrometer. We have observed an intersubband transition as short as 1.45 mu m (0.85 eV) in 2.0-nm-thick InGaAs/AlAsSb quantum wells. This is the shortest quantum well intersubband transition ever reported in any materials system.