Research On Epitaxial Growth And Optical Properties Of InAs/GaAsSb Quantum Dot

InAs/GaAs quantum dot system has been studied thoroughly due to its lasing frequency located within the low-loss window of silicon fibers. Combined with GaAsSb substrate, InAs/GaAsSb quantum dot may have promising applications in solar cell due to the variability of the energy gap of GaAsSb alloy and also its distinct electronic structures. Fundamentals of the growth of InAs/GaAsSb quantum dot using molecular beam epitaxy were studied.Growth method of InAs/GaAs(100) quantum dot was optimized. An introspection into the process of growth of InAs quantum dots reveals that introduction of longer growth interruption rendered larger InAs quantum dots, and thus decreased the density of InAs dots. The optimization of other growth parameters showed that an appropriate As/In BEP (beam equivalent pressure) ratio, which is about 10, can suppress the emergence of giant incoherent nano-islands, which improves the unity of size distribution. For optimized growth, high crystal quality and mono-modal distribution of InAs quantum dots were verified by both surface introspection using AFM and photo-luminescence test results.GaAsSb preparation utilizing an'Sb-soak'method was studied. Samples of GaAs/GaAsSb super-lattice structure were grown under various temperature and Sb flux. A clear X-ray diffractionω/2θprofile signified high quality at the interface and good periodicity for optimized growth. A lower temperature or higher Sb flux during Sb-soak resulted in higher Sb content in the GaAsSb layer. Sharpness of interface and superiority of crystal quality was also verified by high resolution transmission eletron microscopy profile.InAs quantum dots were grown on GaAsSb epitaxial layer. Reflective high energy electron diffraction signal revealed that the critical thickness required for instable growth was larger than that in the case of InAs/GaAs quantum dot. Results of both AFM profile and photo-luminescence spectra suggested that the different kinetics of growth of InAs dots are attributed to the presence of antimony aggregated at the growth front.