Near-infrared intersubband transitions in InGaAs/AlAsSb coupled double quantum wells grown by molecular beam epitaxy

InGaAs/AlAsSb multiple-quantum wells (MQWs) lattice matched to InP substrate have been grown by molecular beam epitaxy. By precisely controlling the As to Sb flux ratio and substrate temperature, fairly abrupt interfaces with 1similar to2 monolayers of compositionary varying layers in both heterointerfaces confirmed from high-resolution transmission electron microscopy (HRTEM) lattice images have been achieved. We have observed intersubband transitions (ISBTs) at 1.23 W (1.01 eV) and 1.45 mum (0.82 eV) from a InGaAs/AlAsSb coupled double-quantum well (C-DQW) structure with 2.1 nm InGaAs wells and 2 nm center barrier layer. This is the first observation of the intersubband absorption in C-DQWs that exhibit two different transition wavelengths shorter than 1.5 mum ever reported in any materials system.