Modulation of Excitonic Quenching in a Selectively Doped Single Quantum Well

Recently the characteristic optical absorption of quantum well structures under the influence of an electron (or electron-hole) plasma has attracted much attention in both modulation doped structures1,2 and optically non-linear devices3. We present here the first direct experimental evidence of room temperature excitonic recovery in a depletion mode selectively doped GaAs single quantum well. Quenching of the excitonic resonance is achieved in this type of structure when the electron Fermi level in the quantum well exceeds the energy of the nz=1 sub-band, as the states normally available for absorption are filled3. The carrier concentration in the quantum well is varied by a pn junction, effectively enabling the transition from a doped to an undoped quantum well to be observed. Mesa etched photodiodes and slab waveguide structures are considered in this work and both reveal the recovery of an excitonic peak. The modulation of absorption achieved is Δα ≈8000cm−1.