InGaAsP/InP (100) grown by metal organic vapor-phase epitaxy is achieved by controlling the As/P surface exchange reaction during InAs deposition. The As/P exchange reaction is suppressed for decreased QD growth temperature and group V-III flow ratio, reducing the QD size and photoluminescence (PL) emission wavelength. The As/P exchange reaction and QD PL wavelength are then reproducibly controlled by the thickness of an ultrathin (0-2 ML) GaAs interlayer underneath the QDs. Submonolayer GaAs coverages result in a shape transition from QDs to quantum dashes at low group V-III flow ratio. Temperature dependent PL measurements reveal excellent optical properties of the QDs up to room temperature with PL peak wavelengths in the technologically important 1.55 mu m region for telecom applications. Widely stacked QD layers are reproduced with identical PL emission to increase the active volume, while closely stacked QD layers reveal a systematic PL redshift and linewidth reduction due to vertical electronic coupling which is proven by the linear polarization of the cleaved-side PL changing from in plane to isotropic. (c) 2006 American Vacuum Society.