Photocurrent spectroscopy of InAs/GaAs self-assembled quantum dots

A photocurrent spectroscopic study of InAs/GaAs sell-assembled quantum dots is reported. Under an applied electric field an asymmetry of the quantum confined Stark effect is observed, implying that the dots possess a permanent dipole moment. For zero field the sign of this dipole requires the hole wavefunction to lie above that of the electron, contrary to the predictions of all recent calculations. Comparison with a theoretical model shows that the correct dipole sign can only be reproduced if the dots are of a non-pyramidal shape and contain a non-zero and non-uniform Ga content. Photocurrent spectroscopy is used to determine the absorption and modal gain of dots incorporated into a laser structure.