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Dissertation Defense

III-Nitride Nanocrystal Based Green and Ultraviolet Optoelectronics

Yuanpeng Wu


Al(Ga)N-based ultraviolet (UV) light emitting diodes (LEDs) are of key importance for a broad range of applications including sterilization, water purification, medical treatment and Raman spectroscopy. The versatility of Al(Ga)N nanostructures allows them to be epitaxially grown on cost-effective foreign substrate despite of large lattice mismatch. In this work, efficient p-type conduction of AlN, which was previously difficult to achieve, has been made possible by exploiting N-rich epitaxy of AlN nanostructures. Monolayer GaN in AlN nanowire was grown and characterized and excitonic deep UV LEDs based on monolayer GaN were achieved. Epitaxy of AlGaN UV LEDs on Al film was demonstrated wherein Al functions as a UV light reflective layer to enhance the light emission efficiency.

Green LEDs, which emit light at the wavelength that is most sensitive to human eye, are required in a variety of applications such as screen- and projection-based displays. Micrometer scale InGaN photonic nanocrystal green LEDs with ~4 nm linewidth were achieved, wherein the emission peak and spectral linewidth are nearly invariant with injection current. A unique strategy to achieve planar p-GaN contact through nanowire coalescence was demonstrated, which significantly reduces the fabrication complexity of green-emitting nanowire-based LEDs on Si substrate.

Chair: Professor Zetian Mi

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