Deep ultraviolet light-emitting diodes (DUV-LEDs) and laser diodes (LDs) with emission wavelengths in the range of 220-350 nm are expected for a wide variety of applications, such as sterilization, water purification, medicine and biochemistry, light sources for high-density optical recording, white light illumination, fluorescence analytical systems and related information sensing fields, air purification equipment, and zero-emission automobiles.