Jae-Hyun Ryou

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ZnO-based light emitting diodes (LEDs) have been considered as a potential candidate for the next generation of blue/ near-UV light sources, [ 1 ] due to a direct wide bandgap energy of 3.37 eV, a large exciton binding energy of 60 meV at room temperature, and several other manufacturing advantages of ZnO. [ 2 ] While the pursuit of stable and reproducible(More)
We demonstrate a three-section, electrically pulsed quantum cascade laser which consists of a Fabry-Pérot section placed between two sampled grating distributed Bragg reflectors. The device is current-tuned between ten single modes spanning a range of 0.46 μm (63 cm(-1)), from 8.32 to 8.78 μm. The peak optical output power exceeds 280 mW for nine of the(More)
Resonance energy transfer (RET) has been employed for interpreting the energy interaction of graphene combined with semiconductor materials such as nanoparticles and quantum-well (QW) heterostructures. Especially, for the application of graphene as a transparent electrode for semiconductor light emitting diodes, the mechanism of exciton recombination(More)
A novel type of nanolasers, which combines the advantages of photonic crystal lasers and microdisk lasers, has been demonstrated based on InAlGaAs/InGaAs quantum wells using pulsed optical pumping at room temperature. It incorporates the properties of small footprint, small mode volume, and submilliwatt threshold, and favors vertical emission. We believe(More)
We report high performance GaN-based npn heterojunction bipolar transistors (HBTs) grown by metalorganic chemical vapor deposition (MOCVD) with state-of-the-art high collector current density (JC) and low knee voltage (V<sub>knee</sub>). For HBTs grown on sapphire, the common-emitter I-V characteristics show high J<sub>C</sub> &gt; 16 kA/cm<sup>2</sup> with(More)
iii ACKNOWLEDGEMENTS I would like to express my sincere gratitude to all those who provide me with the opportunity to complete this thesis. First, I would like to thank my advisor, Professor Shyh-Chiang Shen, for leading me into this fantastic world of III-nitride electronics, for providing me the intelligence and inspiration during my research, and for(More)
We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations.(More)