High Efficiency Mid and Deep Ultraviolet Optoelectronic Devices

Ultraviolet light is a critical component of future technological products, having several applications, the most crucial of which is the sterilization of pathogens – a need which is of prime importance to curtail the spread of diseases and possibly a future pandemic. In this dissertation we discuss the growth, fabrication and characterization of AlGaN-based UV light emitting diodes (LEDs).

Firstly, we used molecular beam epitaxy to address the critical challenge of p-doping wide bandgap AlGaN alloys through a unique metal-semiconductor junction assisted process. We then optimized carrier injection in UV LEDs by investigating different electron-blocking structures. Next, we optimized the design of polarization-engineered tunnel junction LEDs to realize and investigate the characteristics of high efficiency devices with emission at 265 nm and 255 nm. Finally, we discuss the performance of tunnel junction LEDs emitting at 245 nm, as well as the primary obstacles limiting efficiency. Solutions to these challenges are also discussed.

This work provides a path for achieving high efficiency mid and deep UV LEDs that were not previously possible. The techniques mentioned here can be extended to even shorter wavelengths to maximize the efficiency of UV-C AlGaN light sources.

Chair: Professors Zetian Mi and Pallab Bhattacharya