Abstract

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 structures^1,2 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 n_z=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.

© 1989 Optical Society of America