Theoretical Study On Quantum Dots Semiconductor Optical Amplifier And MOCVD Growth Of InAs/GaAs Quantum Dots

Quantum dots (QDs) have gained considerable attentions over the recent years. The uniqueδ-like function density of states and strong carrier confinement indicates potential applications in optoelectronic devices. For QD semiconductor optical amplifier (SOA), they show good performance such as high material gain, good temperature stability, low chirp, high-speed operation. These enhanced performances bring SOA a bright prospect in next generation optical fiber communication systems.However, at present, there still remain problems during the growth of QDs, which lead to the ineffectiveness of its excellent performance. Particularly, some of these problems are, not enough high density of dots, a random statistical distribution of dot sizes and positions, and large polarization dependence.This thesis mainly focuses on solving present problems of QD SOA, both theoretical and experimental researching methods are taken.For theoretical study, a structure called QD-coupled-QW is proposed to improve the carrier capture efficiency and polarization dependence of SOA. Matlab tool is used to simulate the optical gain and polarization dependence.For experimental study, samples of self-assembled InAs QDs on GaAs substrates are grown by metal-organic chemical vapor deposition (MOCVD) with the Stranski–Krastanov growth mode. Atomic force microscope (AFM) and photoluminescence (PL) measurement are used to evaluate structural characteristics and emission wavelength. Firstly, the influence of growth parameters (temperature, generation time,Ⅴ-Ⅲgroup ratio, etc.) are explored. Afterwards, InAs QDs with In_xGa_1-xAs strained-reducing layer (SRL) are investigated, a structure of variant In composition in In_xGa_1-xAs SRL is introduced to improve the performance of QDs. And then, samples are grown on substrates with different surface misorientation, comparative study among 0°,2°,15°misoriented substrates is presented.