摘要
AlGaN is the material of choice for high-efficiency deep UV light sources,which is the only alternative technology to replace mercury lamps for water purification and disinfection.At present,however,Al Ga N-based mid-and deep UV LEDs exhibit very low efficiency.Here,we report a detailed investigation of the epitaxy and characterization of LEDs utilizing an Al Ga N/Ga N/Al Ga N tunnel junction structure,operating at^265 nm,which have the potential to break the efficiency bottleneck of deep UV photonics.A thin Ga N layer was incorporated between p^+and n^+-Al Ga N to reduce the tunneling barrier.By optimizing the thickness of the Ga N layer and thickness of the top n-Al Ga N contact layer,we demonstrate Al Ga N deep UV LEDs with a maximum external quantum efficiency of 11%and wall-plug efficiency of 7.6%for direct on-wafer measurement.It is also observed that the devices exhibit severe efficiency droop under low current densities,which is explained by the low hole mobility,due to the hole hopping conduction in the Mg impurity band and the resulting electron overflow.
基金
Army Research Office(W911NF19P0025)
College of Engineering
University of Michigan
The devices were fabricated in theLurie Nanofabrication Facility at the University of Michigan.The authors acknowledge the Michigan Center for MaterialsCharacterization for electron microscopy。
