Effect Of InGaAs Layer On The Properties Of (B)InAs/GaAs Quantum Dots

During the past few decades, quantum dot(QD) heterostructures have attracted increasing attention of the researchers in the whole world owing to their unique optoelectronic properties. In particular, semiconductor lasers with InAs/GaAs self-assembled quantum dots as active area have become an important research area in the field of QD optoelectronic devices. How to extend emission wavelength of QDs has also become a problem to be solved. The emission wavelength of InAs QDs with GaAs overgrown layer is difficult to reach 1.3μm, and several reports have shown that the emission wavelength of InAs QDs shifts towards a longer wavelength by capping InAs QDs with an InxGa1-xAs strain-reducing layer. However, the main factors that influence the peak wavelength have not been investigated comprehensively.This thesis focuses on the research of InGaAs layer on the morphology and optical properties of InAs/GaAs self-assembled quantum dots. Research results are listed as below:1. Surface morphologies of QD samples with different growth temperature, growth rate, V/III ratio and deposition thickness have been investigated. The effects of growth parameters on the morphology properties of QDs have been studied.2. Effects of InxGa1-xAs strain reducing layer on the optical properties of quantum dots have been studied in detail. The InAs/GaAs QDs grown at 530℃, with Gr of 0.06ML/s,Ⅴ/Ⅲratio of 10, capped by InxGa1-xAs strain reducing layer, have been obtained with peak wavelength at 1328nm and linewidth at 44meV.3. InGaAs underlayer was grown between GaAs buffer layer and InAs QDs. It was found that InGaAs underlayer could reduce the strain between the bottom of InAs QDs and GaAs buffer layer. At InAs thickness of 3.0ML, compared with the InAs QDs on a single GaAs buffer layer, the average height of InAs QDs using an InGaAs underlayer decreased by 0.9nm, the average diameter increased by 6nm and the density was slightly increased.4. InAs/GaAs self-assembled quantum dots with boron incorporation were studied. Morphology and optical properties of quantum dots with and without boron incorporation have been characterized by AFM and photoluminescence measurements. It was found that introducing boron changed the strain distribution. When capped by the same GaAs overgrown layer, compared with InAs QDs, the peak wavelength of BInAs QDs was red-shifted with 15meV, and the emission intensity was greatly enhanced. When capped by the same InxGa1-xAs strain reducing layer, the incorporation of boron atoms within the InAs QDs caused a blue shift of emission wavelength and a decrease in FHWM. The 3.6ML BInAs QDs capped by InxGa1-xAs strain reducing layer have been obtained with peak wavelength at 1323nm and linewidth at 40meV.