Dielectric-enhanced quantum-well intermixing in lambda = 1.55 micron indium gallium arsenic phosphide/indium phosphide laser structures

Abstract

<p>This thesis presents dielectric-enhanced quantum-well intermixing (QWI) studies of InGaAsP/InP-based λ = 1.55 μm laser structures for photonic integration. QWI is studied as a function of MBE growth, dielectric film (SiO x Ny ) composition and thickness, annealing temperature and time. The results suggest there are at least two processes that cause intermixing in samples without dielectric coatings, related to grown-in defects. It is found that plasma-enhanced chemical-vapor-deposited SiOx Ny films of refractive index 1.65 are best at enhancing the QWI process. Based on SIMS measurements of these films before and after anneal we observe the migration of Group III atoms into the dielectric film. Consequently we believe that Group V interstitials are injected into the laser structure and are responsible for the enhanced QWI. However, the amount of intermixing does not correlate with the amount of Group III that migrates into the dielectric film, suggesting that another factor, such as film stress, may affect the amount of injected interstitials. This postulated mechanism for InGaAsP/InP-based structures differs from the accepted belief that in the GaAs materials system the dielectric film injects Group III vacancies into material which promote the intermixing process, and that the number of injected vacancies is related to the film porosity. The thesis concludes with a presentation of materials properties and processing issues which are important for device fabrication. It is shown that although the electrical and optical properties of the intermixed material remain desirable, the process leads to difficulties in wet chemical etching and regrowth over material annealed with dielectric films.</p>