Experimental and theoretical investigation of interband and intersubband transitions in type-II InAs/AlSb superlattices

Abstract

Both theoretical and experimental results on interband and photoinduced intersubband absorption in undoped type-II InAs/AlSb heterostructures are reported. The observation of the ${e}_{1}$ to ${e}_{2}$ intersubband transition without optical pumping enables us to evaluate the n residual doping in InAs around ${10}^{16}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}.$ A spatially direct transition is observed by interband absorption. Calculations using an 18-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ model indicate that this transition involves a confined electron and a quasibound hole state, both in the InAs layer. A good agreement with the calculations is observed on both the polarization and the energy at which interband and intersubband transitions occur.