i Abstract High density (4.5 x 1010 /cm2), uniform (std. < 10%) InAs quantum dots (QDs) were successfully grown on InP substrate by metalorganic chemical vapor deposition (MOCVD). In the temperature range of 500~550oC, contrary to the general trend in the InAs/GaAs QD system, there is a non-monotonous dependence of the QD size and density on the growth temperature. This can be attributed to the extra flux of InAs from the substrate induced by As/P exchange reaction. As the temperature is raised, the increased flux due to the excess InAs formation tends to increase the QD density, whereas the enhanced surface diffusivity with the temperature decrease the QD density. As a result, there is an optimal temperature (535oC), at which the QD density attains its maximum. Above 535oC, QD density decreased again, showing the general temperature dependence. The activation energy of 1.4 eV for the excess InAs formation was derived from the measurements of the total volume of QDs at several growth temperatures, and the value matches well with that for As/P exchange reaction (1.3 eV). It was shown that the in situ characterization by reflectance signal could be utilized to estimate the amount of InAs on the surface. With a capping at alternating temperature (CAAT) method, InAs/InP was successfully stacked up to 5 layers. PL result showed that this method improved the consistency in the properties of each stacked QD layer. The whole sequence was monitored in situ by the spectral reflectance (SR). In situ spectral reflectance (SR) signals were collected during the growth of InAs QDs and the capping layers, and the signal changes could be interpreted as the change of excess InAs amount formed at the surface. The SR subtraction spectrum is highly sensitive to surface chemical species and their dynamics. As-dimer related peaks were observed at around 2.4 eV, and it can be interpreted as surface dimer-structure change owing to the QD formation.