QUANTUM DOTS FORMED BY INTERFACE FLUCTUATIONS IN ALAS GAAS COUPLED-QUANTUM-WELL STRUCTURES/

We report about optical experiments on electric field tunable AlAs/GaA s coupled quantum well structures in the regime of the electric field induced GAMMA-X transition. Using the energetically tunable X-point st ate in the AlAs layer as an internal energy spectrometer and charge re servoir we are able to map out the electronic states in the neighborin g GaAs quantum well in great detail. In spatially resolved and bias vo ltage dependent photoluminescence experiments we find sets of extremel y narrow emission lines below the fundamental band gap energy of the G aAs quantum well. The new emission lines are shown to originate from n atural quantum dots which are formed by well width fluctuations of the GaAs quantum well.