Optimized doping and contact scheme for low-voltage 275-nm deep ultraviolet LEDs

Deep ultraviolet light-emitting diode structures with a peak wavelength of 275 nm, as well as individual AlGaN:Mg layers, were grown by metalorganic chemical vapor deposition on (0001) silicon carbide. Control of the Mg profile in the devices reduced unwanted Mg-related emission at 320 nm to 1/224th of that emitted at the peak wavelength. An additional peak at 410 nm was observed to be related to oxygen incorporation in the film and confirmed with secondary ion mass spectroscopy (SIMS). Also investigated in an effort to improve hole injection were aluminum content, layer thickness, V/III ratio, activation temperature, and properties of the GaN:Mg contact layer and transparent contact metal stack. By optimizing this and other layers of the device, output powers of 0.84 mW at 1.3 A were obtained from packaged devices, with forward voltages as low as 4.9 V at 20 mA.