Molecular beam epitaxy growth of novel double-layer InAs quantum dot structures and their optical properties

We have designed and grown by molecular beam epitaxy (MBE) a novel sample with Schottky contact in which two sheets of InAs quantum dots (QDs) of different sizes are embedded at different positions of its depletion layer. Electronic states in these two respective QD layers are expected to be perturbed not only by the space-charge electric field but also by the carrier accumulation in QDs of both layers. We have investigated photoluminescence (PL) spectra of each dot layer under various bias conditions to clarify, in particular, how the local electric field is influenced by the accumulation of carriers in each dot layer, especially when two dot layers are closely spaced (25 nm). The ground state transition energy of large dots shows an anomalous blue shift, which is as large as 11 meV when a positive bias is applied. We show that the depopulation of charged dots is responsible for this anomaly. (c) 2005 American Vacuum Society.