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 Title: Distributed Feedback Ridge Waveguide and Step-Graded Separate Confinement Quantum Well Heterostructure Lasers Grown by Metalorganic Chemical Vapor Deposition Author(s): Miller, Linda Michelle Doctoral Committee Chair(s): Coleman, James J. Department / Program: Electrical Engineering Discipline: Electrical Engineering Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Engineering, Electronics and Electrical Abstract: With the advent of sophisticated epitaxial growth techniques such as metalorganic chemical vapor deposition (MOCVD), compound semiconductor device research has flourished. Advancements in device physics as well as the development of coherent optical sources and high speed electronic devices have been achieved in both lattice-matched systems such as the GaAs-AlGaAs heterostructure, and strained-layer material systems such as the InGaAs-GaAs-AlGaAs structure. Topics involving these material systems grown by atmospheric-pressure MOCVD, the device physics of step-graded separate confinement quantum well heterostructure lasers, and the development of novel strained-layer distributed feedback ridge waveguide (DFB RW) quantum well laser and laser array are presented in this work.Data are presented on the pulsed operation of GaAs-AlGaAs step-graded separate confinement quantum well lasers with direct and indirect inner barriers and outer confining layers of $\rm Al\sb{0.85}Ga\sb{0.15}As.$ By varying the waveguide and energy band characteristics in this way, it is shown that, given an adequate optical waveguide confinement factor and sufficient cavity length, (1) the collection of electrons in thin quantum wells with both direct and indirect barriers can be highly efficient, (2) transfer of electrons from indirect barriers to thin direct wells does not degrade laser performance, and (3) electron confinement in the separate confinement region plays no role in the operation of the laser.A relatively simple InGaAs-GaAs-AlGaAs distributed feedback laser ridge waveguide quantum well heterostructure laser is presented in which gratings are formed along the ridge by direct-write electron-beam lithography and reactive ion etching in a single post-growth processing step. The lateral grating on either side of the contact stripe serves as an effective index step to eliminate antiguiding effects and as a source of distributed feedback to produce single longitudinal mode emission. Laser emission at the DFB resonant wavelength, with competition from residual Fabry-Perot modes, is observed in the initial demonstration of this structure. By optimizing the design of the grating period and of the etch depth of the gratings, single longitudinal mode emission is measured with increasing drive current for devices coated with an anti-reflective film on one facet.By extending the concept of the strained-layer InGaAs-GaAs-AlGaAs quantum well heterostructure distributed feedback ridge laser to a parallel laser structure, high power laser arrays are also demonstrated which exhibit phase-locked emission in the highest-order supermode. Pulsed and continuous wave (cw) light-current, pear-field, far-field and spectral data are presented for fourteen element arrays with cavity lengths of 430 $\mu$m and uncoated facets. Issue Date: 1992 Type: Text Description: 108 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1992. URI: http://hdl.handle.net/2142/71983 Other Identifier(s): (UMI)AAI9305622 Date Available in IDEALS: 2014-12-16 Date Deposited: 1992
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