AlGaN-based deep UV light emitting diodes with peak emission below 255 nm

We report on the growth and fabrication of AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with peak emission of below 255 nm. In order to achieve such short wavelength UV LEDs, the Al mole fractions in the device layers should be greater than similar to 60 %. This introdues serious challenges on the growth and doping of Al(x)Gal(1-x)N epilayers. However, with the aid of a high-quality AlN template layer and refinement of the growth conditions we have been able to demonstrate UV LEDs emitting below 255 nm. The ratio of the intensity of the electroluminescence primary peak to that of the secondary peak (related to Mg deep levels) is similar to 18:1 at moderate injection current levels. Milliwatt level output powers have been achieved for these deep UV LEDs.