Improved area density and luminescence properties of InP quantum dots grown on In0.5Al0.5P by metal-organic chemical vapor deposition

We report on the growth of InP self-assembled quantum dots (QDs) on In_0.5Al_0.5P matrices by metal-organic chemical vapor deposition (MOCVD) on (001) GaAs substrates. The effects of the growth temperature and V/III-precursor flow ratio on the areal density and the cathodoluminescence (CL) properties of the grown QDs were systematically studied. We found that, when the growth temperature is ≤630°C, coherent QDs as well as large dislocated InP islands can be observed on the matrix surface. However, by using a two-step growth method, i.e., by growing the InAlP matrix layer at higher temperatures and growing InP QDs at lower temperatures, the formation of large dislocated islands can be effectively suppressed. Moreover, the areal density of the InP QDs is increased as the QD growth temperature is reduced. Furthermore, we found that the V/III ratio used in growing QDs and in growing the InAlP matrix layers has a quite different effect. In growing QDs, decreasing the V/III ratio results in an increase in the CL intensity and a decrease in CL line width; while in growing the InAlP matrix layers, increasing the V/III ratio results in an increase in the CL intensity of the InP QDs.