Fabrication and Characterization of Ultraviolet Light Emitting Diodes with Nanometer Scale Compositionally Inhomogeneous Active Regions

In this paper we report on the growth and fabrication of ultraviolet light emitting diodes that employ a novel AlGaN active region containing nanometer scale compositionally inhomogeneous (NCI) regions. These plasma-assisted molecular beam epitaxy grown NCI-AlGaN films exhibit enhanced photoluminescence intensity due to carrier localization and concentration in nanoscale regions of smaller bandgap that suppresses non-radiative recombination and improves radiative efficiency. We observe that the formation, density and size of these NCI regions are modified strongly by growth conditions. The emission wavelength of these alloys may be controllably tuned from 275 to 340 nm by varying growth conditions. Double heterostructure ultraviolet light emitting diodes were fabricated that emit at peak wavelengths of 310nm and 324 nm with output power of 0.11 mW and 0.42 mW for a 100 mA DC drive current. These results demonstrate the potential for NCI-AlGaN active regions to improve the efficiency of III-Nitride based ultraviolet emitters.