This project addresses materials science research on InGaNAs/GaAs, a technologically relevant material to the telecommunications(1.3um) industry. The performance(characteristic temperature, To) of InGaNAs lasers is considerably higher than that of equivalent InP-based lasers, in part due to the increased electron confinement resulting from the larger conduction band offsets in this material compared to InGaAsP/InP. InGaNAs vertical-cavity surface-emitting lasers (VCSELs) have been demonstrated, and the epitaxial structure of InGaNAs VCSELs overcomes one of the largest problems in developing high-performance VCSELs at a reasonable cost, since high quality AlGaAs/GaAs distributed Bragg reflectors are easily incorporated with the InGaNAs active region. The two primary materials issues that this project will address are the extension of the emission region to longer wavelengths and the elimination of nonradiative defects, which cause a high internal absorption coefficient and high current threshold, through the incorporation of pseudomorphically strained InGaNAs quantum wells in the laser epitaxial structure. Specifically, the bandgap of the epitaxial material will be tailored through deliberate modification of growth kinetics to optimise nitrogen incorporation and adjust lattice strain across the InGaNAs active region. The approach is to alter the amount of nitrogen that can be incorporated while two-dimensional (2D) growth is sustained by varying the substrate orientation, growth temperature, and lattice strain. The effect of bandgap tailoring will be evaluated by characterizing the epitaxial structures via photoluminescence (PL) studies as well as by characterizing the optical and electrical performance of InGaNAs Fabry-Perot laser diodes. The results from both PL and device characterization studies will be coupled in order to achieve a more complete understanding of the InGaNAs heterostructures. In particular, the relationship between bandgap tailoring techniques and emission wavelength and radiative and nonradiative properties will be determined. The application of standard AlGaAs processing techniques, such as impurity-induced disordering and native oxidation, to fabricate planar index-guided emitters will also be explored. Following a materials characterization study to verify that these processes have not degraded any material properties, an index-guided edge-emitting laser will be fabricated. The basic goal of the proposed project is to gain greater understanding of InGaNAs/GaAs growth and processing, and achievement of significant enhancements in the performance of single-mode planar InGaNAs laser diodes through improved growth and processing techniques. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. These studies will improve fundamental understanding of basic materials properties limiting the efficiency and performance of telecommunications light sources. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project is designed to develop strong technical, communication, and organizational skills in students through unique educational experiences made possible by a forefront research environment. ***

National Science Foundation (NSF)
Division of Materials Research (DMR)
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LaVerne D. Hess
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West Virginia University Research Corporation
United States
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