Piezoelectric effects on the electron-hole dipole in In0.5Ga0.5As/GaAs self-assembled quantum dots

Photocurrent spectroscopy is used to investigate the quantum-confined Stark shift, QCSS, of In0.5Ga0.5As/GaAs self-assembled quantum dots (QDs) grown on (100) and (311)B planes. An asymmetric dependence of the QCSS with respe ct to the direction of the electric field is observed in both cases, We sho w that the (100) dots have an almost zero permanent electron-hole dipole mo ment. This result indicates that the recently reported "inverted electron-h ole alignment" [Phys. Rev. Lett. 84, 733 (2000)] is not a general property of QDs. By comparing the QCSS for the (100) and (311)B dots, we propose tha t in the dots grown on the high index plane, the electron and hole wavefunc tions are displaced by a strain-induced piezoelectric field.