Optical studies of Ga_xIn1_-xP/Ga_0.5In _0.5P quantum dots

Self-assembled type A Ga_xIn_1-xP/Ga _0.5In_0.5P quantum dots (QDs) have been investigated using continuous wave and time-resolved photoluminescence (PL) techniques. The QDs were grown by low-pressure metalorganic vapour phase epitaxy using the Stranski-Krastanow growth mode. A substrate misorientation of 15° towards the (111)B plane leads to the formation of type A dots with a height of approximately 5 nm. The novel effect of varying the Ga content of the QDs has been examined and the PL emission energy of the dots is observed to increase from 1.71 eV to 1.90 eV as the Ga content is varied from 0% to 30%. Temperature dependent (5 K to 260 K) time-resolved PL measurements have also been performed in order to study the dot carrier dynamics in more detail. These measurements indicate that the Type II InP/GaInP QDs either become smaller or that the band structure changes to a Type I alignment with the addition of Ga. Both effects, if present, could be attributed to a decrease in the dot strain as Ga is added.