Development of Deep UV LEDs and Current Problems in Material and Device Technology

Abstract We review progress in development of deep ultraviolet light-emitting diodes and discuss key factors currently affecting device performance. Heteroepitaxial growth of AlN and AlGaN by high-temperature epitaxy has resulted in significant improvement of LED efficiency through reduction of density of nonradiative defects. Importance of alloy composition fluctuations is discussed based on results of time-resolved temperature-dependent photoluminescence and light-induced grating measurements of Al 0.6 Ga 0.4 N layers with different density of dislocations. Improvement of LED performance achieved by suppression of the nonradiative recombination in epitaxial structures with dislocation density reduced to below 5 × 10 8  cm − 2 , transparent LED structure design, and optimized UV-reflective contacts. Aspects of the LED chip design are discussed for further improvements of light extraction and LED output power. Research is now under way to use these devices for numerous applications including water and air purification, sterilization, biological threat identification, applications in medicine, biology, industrial processes, defense, and homeland security.