Normal incidence intersubband absorption in InGaAs quantum wells

Multiple quantum well (MQW) C₁-to-C₂ intersubband transitions between quantized states in the QW conduction band are discussed. The Si-doped InAlAs/InGaAs MQW samples used in this study were grown by molecular beam epitaxy. The polarization activity of intersubband transitions is considered. The interest of this work is to (i) experimentally retrieve the correct polarization selection rules for intersubband transitions by devising polarization-resolved and angle-resolved IR measurement techniques, and (ii) theoretically develop a new model that fully explains the features of selection rules, absorption strength, and the splitting of the experimental observations