Exciton-free layer depth as a function of the excitonic energy and of band parameters

Abstract

We show how to compute the depth-dependent susceptibility in the region of excitonic resonances. From its shape the depth of the exciton-free layer (“dead layer” ) can be established as a function of the excitonic energy. Numerical examples appropriate to GaAs/Ga1-xAlxAs superlattices are given. We show that the dead-layer depth increases when the energy of the incoming photon approaches the excitonic resonances. Near the resonances an excitonic enhancement of the susceptibility is also found in the “dead layer” itself.