The III-nitride wide bandgap semiconductors have been widely recognized as technologically important materials. Photonic devices based on III-nitrides offer many benefits including UV/blue/green emission, large band offsets of InN/GaN/AlN heterostructures, and inherently high emission efficiencies. These unique features may allow the creation of optoelectronic and photonic devices with unprecedented properties and functions. Achieving device quality Al-rich AlGaN with high conductivities and high quantum efficiencies remains one of the foremost challenges for the nitride community. AIN and Al-rich AlGaN alloys-covering wavelengths from 300 to 200 nm-are ideal materials for the development of chip-scale UV light sources/sensors, because AlGaN is the only ultra-wide-bandgap semiconductor system by which the bandgap can be easily engineered through the use of alloying and heterostructure design. Efficient solid-state UV light sources/sensors are crucial in many fields of research and development. Availability of chip-scale UV light sources is expected to open up new opportunities for medical research and health care. Solid-state UV light sources also have applications in water purification, equipment/personnel decontamination, and white light generation. There is an urgent need for developing new approaches to further improve material quality with reduced dislocation density and unintentional impurities and improved surface morphologies in Al-rich AlGaN alloys, which would enhance the doping efficiency and device performance.