Observation of a complex Franz-Keldysh oscillation in InAs/GaAs quantum dots

In this research, complex Franz-Keldysh oscillations (FKOs) were observed from InAs/GaAs quantum dots (QDs) by using the low-temperature photoreflectance spectroscopy. The results suggested that the complex FKOs originated from various electric fields at the interfaces between GaAs and the InAs QD. Electric field strengths were evaluated by using a fast Fourier transform analysis. The fields had a broad range from similar to 5 x 10(3) to similar to 2 x 10(5) V/cm. In this paper, strain-induced interface electric fields are suggested on the origins of the FKOs. Moreover, the straininduced lattice deformation, the defect generation, and the quantum confinement effect are discussed as possible sources for the interface electric fields.