Miniband formation in InGaAs quantum dot superlattice with InGaP matrix for application to intermediate-band solar cells

We report the formation of vertically coupled states in a 20-stack InGaAs QD superlattice with GaAs spacer layers in an InGaP matrix for an application to optimal intermediate-band solar cells. The InGaAs QD superlattices in the InGaP matrix have good optical properties even though the interdot spacing is reduced to 4.5 nm. We confirmed the formation of vertically coupled states by the excitation power dependence in photoluminescence (PL) measurements. The PL peak of a QD superlattice shifts to a shorter wavelength as the excitation power is increased. The blue-shifted energy of the PL peak is 11 meV for a QD superlattice with an interdot spacing of 4.5 nm, whereas the blue shift is not observed for a multistacked QD structure with an interdot spacing of 17 nm. The InGaAs QD superlattices in an InGaP matrix are very attractive for use in realizing the optimal intermediate-band solar cells.