Browsing by Author "Chern, Kevin Tsun-Jen"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Fabrication and Characterization of Narrow-Stripe Quantum Well Laser Diodes
    Chern, Kevin Tsun-Jen (Virginia Tech, 2009-06-25)
    More efficient semiconductor lasers will be needed in tomorrow's applications. These lasers can only be realized through the application of new device processing techniques, designed to restrict current, carrier, and/or photon flow through the lasing cavity. This work aims to evaluate a non-conventional stripe laser processing technique which has the potential for effective current and possibly carrier confinement at low cost. This technique, referred to as hydrogen passivation, involves exposing laser material to a low energy hydrogen plasma, causing hydrogen ions to bind to charged acceptor and donor atoms. Such binding compensates the electrical activity of these dopant atoms and thereby increases the resistance of the exposed material. Optical confinement can also be achieved (subsequent to hydrogenation) by using a simple wet-etching process to form a lateral waveguide. Stripe lasers fabricated via hydrogen passivation have been demonstrated previously; however, the benefits of this method have not been fully explored or characterized. Our work aims to quantify the degree of current and carrier confinement provided by this technique. The cleaved cavity method of analysis is used to extract laser parameters via direct measurement. These parameters are then compared against those obtained from more conventional stripe lasers to identify improvements that have accrued from using hydrogen passivation.
  • Thumbnail Image
    GaInN/GaN Schottky Barrier Solar Cells
    Chern, Kevin Tsun-Jen (Virginia Tech, 2015-06-02)
    GaInN has the potential to revolutionize the solar cell industry, enabling higher efficiency solar cells with its wide bandgap range spanning the entire solar spectrum. However, material quality issues stemming from the large lattice mismatch between its binary endpoints and questionable range of p-type doping has thus far prevented realization of high efficiency solar cells. Nonetheless, amorphous and multi-crystalline forms of GaInN have been theorized to exhibit a defect-free bandgap, enabling GaInN alloys at any indium composition to be realized. But the range of possible p-type doping has not yet been determined and no device quality material has been demonstrated thus far. Nonetheless, a Schottky barrier design (to bypass the p-type doping issue) on single-crystal GaInN can be used to provide some insight into the future of amorphous and micro-crystalline GaInN Schottky barrier solar cells. Through demonstration of a functional single crystalline GaInN Schottky barrier solar cell and comparison of the results to the best published reports for more conventional p-i-n GaInN solar cells, this work aims to establish the feasibility of amorphous and multi-crystalline GaInN solar cells.