Dissertation Defense

High-Efficiency Al(Ga)N Ultraviolet Optoelectronics and Integrated Photonics

Walter Shin

Passcode: wff38n

High Al composition Al(Ga)N semiconductors attract tremendous research interest as a promising photonic integrated circuits (PICs) platform due to its wide bandgap, nonlinear optical properties, and the possibility of passive/active functionalities on the same platform. In this dissertation, we focus on the design and development of optoelectronic and photonic devices based on high Al composition Al(Ga)N on sapphire substrate, including deep UV light-emitting diodes (LEDs) and microring resonators (MRRs).

First, we investigate the epitaxy, design, fabrication of high-efficiency deep UV LEDs emitting at ~265nm, which can be utilized to sterilize pathogens. To overcome the inefficient hole injection and light-emitting efficiency, polarization-engineered tunnel junction and photonic crystal are investigated, significantly improving the external quantum efficiency.

Next, we optimize the fabrication process to demonstrate ultra-high Q AlN-based MRRs. In addition, we suggest new techniques to characterize demonstrated MRR using thermo-optic tuning. Finally, we achieve an enhanced Pockels coefficient of AlN by utilizing AlGaN/AlN multiple quantum wells and demonstrate enhanced modulation efficiency AlN-based microring modulator.

This work provides a viable and unique path to realize high-efficiency deep UV LEDs extended to other wavelengths. In addition, based on the demonstrated high-Q MRRs along with the enhanced Pockels effect, our studies show a new opportunity to achieve a high-performance monolithic PIC platform.

Chair: Professor Zetian Mi