Abstract:
The effect of GaP and InGaP insertion layers on self-assembled InP quantum dots are presented and discussed, together with their growth, structural and optical properties. In the growth of InP/InGaP/GaAs self-assembled quantum dots (SAQDs), eventhough the bimodal size distribution for the coherent islands can be overcome by using GaP and InGaP insertion layers, the island size is still large and the areal density of dots is low. Since large dots may introduce dislocations and low density leads to poor optical efficiency, growth of small size, high density and uniformity of InP dots becomes imperative. Under the proper growth conditions, formation of InP QDs via the Stranski-Krastanow mechanism is observed. The critical InP coverage for insertion of GaP layer is found to be 3 ML for the InP/ In0.48Ga0.52P/GaAs system in MBE growth system and 4 ML for the InP/ In0.49Ga0.51P/GaAs system in MOVPE system. The structural characterization from atomic force microscopy (AFM) measurements indicates that the MBE growth of InP/ In0.48Ga0.52P QDs are larger and, consequently, more dense compared to the MOVPE growth of InP/ In0.49Ga0.51P QDs. By observing photoluminescence (PL) from InP quantum, the PL peak wavelength is continuously reduced between 770 and 810 nm with increase of the GaP and InGaP insertion layers thickness. This red spectral range is also preferable to generate highest photon detection efficiency for single-photon detectors. Additionally, the InP QDs with GaP and InGaP ILs must influence the optical properties of possible quantum optic devices which have to be carried out in future work.
