Vertical quantum confinement effect on optical properties of strain-induced quantum dots self-formed in GaP/InP short-period superlattices

Optical properties of multilayer quantum dots (MQDs) self-formed in the GaP/InP short period superlattice (SL)/InGaP multilayer structures are investigated by changing the SL period (P) and InGaP barrier thickness (B). By decreasing P, photoluminescence (PL) peak energy is shifted toward higher energy due to the quantum size effect along the growth direction (vertical direction). PL linewidth broadening with temperature is reduced by decreasing P and B. This improvement is attributed to the reduction of potential distribution among quantum dots (QDs) and the enhancement of quantum confinement along the vertical direction; and to the enhancement of quantum confinement due to the vertical coupling effect between QDs. Stokes shift for the MQDs structure is observed to be small. Very small temperature variation of PL peak energy is observed in these MQDs, which originates from the existence of the multiaxial strains among the MQDs. Electroluminescence (Et) spectra show split peaks corresponding to the subbands of QDs on increasing injection current.