Quantum-confined Stark effect and built-in dipole moment in self-assembled InAs∕GaAs quantum dots

Quantum-confined Stark effect and built-in dipole moment in self-assembled InAs∕GaAs quantum dots (QDs), which are grown at relative low temperature (460°C) and embedded in GaAs p–i–n structure, have been studied by dc-biased electroreflectance. Franz–Keldysh oscillations from the undoped GaAs layer are used to determine the electric field under various bias voltages. Stark shift of −34meV for the ground-state interband transition of the QDs is observed when the electric field increases from 105 to 308kV∕cm. The separation of the electron and hole states in the growth direction of 0.4nm, corresponding to the built-in dipole moment of 6.4×10−29Cm, is determined. It is found that the electron state lies above that of the hole, which is the same as that predicted by theoretical calculations for ideal pyramidal InAs QDs.