UV-Laser Induced Quantum Well Intermixing Technique And Its Aplications For Photonic Integrated Devices

Demand for bandwidth continues to increase for the twenty-first century’s telecommunication industry. The advent of wavelength division multiplexing (WDM) technique has greatly increased the quantity of data transported within each optical fiber. Several key technologies are poised to revolutionize the communication industry. The introduction of widely-tunable lasers that are capable of tuning to any channel on the international telecommunications union (ITU) grid will dramatically reduce the cost of running system through sparing functions, allowing system operators to reduce laser inventory and replacing fixed wavelength lasers with tunable lasers. Another key technology is the photonic integrated circuit (PIC), which can allow the cost reduction through monolithic integration. These devices are considered ideal building blocks for the development of next generation, efficient, high bandwidth fiber optic networks.Integration of discrete components into a single system is similar to that of electronic integration. It enhances the performance, reliability and increases the functionality while lowering the cost of manufacturing. Fabrication of photonic integrated circuits requires the integration of multiple bandgap structures within a single semiconductor chip. Quantum well intermixing (QWI), among others is a promising technique for realizing multifunctional monolithic integrated components. QWI is much simpler, reproducible and effective to modify the band-gap of quantum well structure as compared to the selective-area-epitaxy or etch-and-re-growth techniques.Among other potential techniques to achieve monolithic photonic integrated circuits, post-growth quantum well intermixing in selected regions increases the effective band gap energy of a semiconductor QW structures. Thermally activated intermixing process is accelerated by the diffusion of impurities and of point defects such as free vacancies and interstitials. For this thesis work, we investigate and demonstrate experimentally ultra-violet laser based post-growth QWI technique and then develop a novel wafer processing technique using UV-laser QWI. The QWI process allows the formation of multiple quantum well band edges, ideally one specific to each integrated component. We investigate how UV irradiation creates point defect and how the thermal diffusion of these point defects in InP based QW structures controls the quantum well intermixing in specific regions. We further investigated two other QWI techniques using the sputtering of SiO2and AI2O3as an alternative to UV-laser QWI.This thesis presents my contribution to post-growth UV-laser, SiO2and Al2O3based quantum well intermixing techniques and demonstrates the applications of UV-laser QWI for photonic devices that can lead to photonic integrated circuits. The main innovations are as follows:1. Developed experimentally UV-laser induced quantum well intermixing and applied it to strained multiple quantum well (MQW) structure. Obtained larger blue shift (over142nm) as compared to unstrained MQW, while the PL peak intensity becomes even higher with narrower full width at half maximum (FWHM).2. Fabricated passive optical waveguides using UV-laser induced quantum well intermixing in InGaAsP/InP quantum well structure. The loss of the waveguide for1545nm light drops from11OdB/cm to20dB/cm.3. Fabricated Fabry-Perot cavity lasers with blue-shifted lasing wavelength of1435nm using UV-laser induced quantum well intermixing in InGaAsP/InP strained quantum well structure and obtained a lower threshold current and a large output power.4. Implemented the Argon plasma induced QWI during the sputtering of SiO2in standard InGaAsP/InP compressively strained multiple quantum well structure and systematically studied the relations of RF power, annealing temperature to the altered quantum well PL peak blue-shift and PL intensity. 5. Proposed and investigated sputtering of Al2O3induced quantum well intermixing technique in InGaAsP/InP multiple quantum well structure with and without sacrificial layer for the first time, and obtained over110nm blue-shift.