29 February 2016 New directions in GaN photonics
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Abstract
We have developed a novel conductivity based selective electrochemical etching to introduce nanometer sized pores into GaN. By controlling the doping and electrochemical etching bias, we are able to control the pore morphology. The nanoporous (NP) GaN can be considered a new form of GaN with an unprecedented tunability in optical index We show the potential of this NPGaN to overcome the optical and epitaxial limitations of AlGaN, which has been the bottleneck for GaN-based laser diodes for decades. The advantages of NP-GaN for both vertical surfaceemitting laser diodes (VCSEL) and edge-emitting laser diodes are exhibited in subsequent sections. We first demonstrate the record high reflectances (R > 99.5 %) from epitaxial NP-GaN mirrors, which are used in a low threshold optically pumped VCSEL. We then show a two-fold increase of modal gain in an edge-emitting waveguide geometry with optical confinement Γ engineering. The increase of the Γ also leads to a two-fold reduction in the threshold power density under optical pumping with a threshold material gain of 400 cm-1, which is more than two times lower than previously reported (> 1,000 cm-1).
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Ge Yuan, Ge Yuan, Cheng Zhang, Cheng Zhang, Kanglin Xiong, Kanglin Xiong, Sunghyun Park, Sunghyun Park, Jung Han, Jung Han, "New directions in GaN photonics", Proc. SPIE 9748, Gallium Nitride Materials and Devices XI, 97480Q (29 February 2016); doi: 10.1117/12.2214365; https://doi.org/10.1117/12.2214365
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