Electronic properties of InAs/GaAs self-assembled quantum dots studied by photocurrent spectroscopy

The power of photocurrent spectroscopy to study the electronic properties of InAs/GaAs self-assembled quantum dots is described. From comparison of results from different samples it is shown that photocurrent provides a direct means to measure absorption spectra of quantum dots. Studies in high-electric field enable the electron-hole vertical alignment to be determined. Most surprisingly this is found to be: opposite to that predicted by all recent predictions. Comparison with theory shows that this can only be explained if the dots contain significant amounts of gallium, and have a severely truncated shape. The nature of the ground and excited state transitions, carrier escape mechanisms from dots and in-plane anisotropies are also determined. (C) 2001 Elsevier Science B.V. All rights reserved.