Device performance of AlGaN-based 240 - 300 nm deep UV LEDs

Deep ultraviolet light emitting diodes (LEDs) with emission wavelengths shorter than 300 nm have been grown by metalorganic vapor phase epitaxy. A bottom emitting LED design is used which requires a high-Al content Al xGa 1.xN (x = 0.5 - 0.8) buffer layer which has sufficient conductivity and is transparent to the quantum well emission wavelength. LEDs were flip chip mounted to a silicon submount which provides for good thermal performance as well as improved light extraction. For large area 1 mm × 1 mm LEDs emitting at 297 nm, an output power as high as 2.25 mW under direct current operation has been demonstrated at 500 mA with a forward voltage of 12.5 volts. For shorter wavelength LEDs emitting at 276 nm, an output power as high as 1.3 mW has been demonstrated under direct current operation at 300 mA with a forward voltage of 9.2 volts. Recent improvements in heterostructure design have resulted in quantum well emission at 276 nm with a peak intensity that is 330 times stronger than the largest sub-bandgap peak. LEDs with emission wavelengths as short as 237 nm have also been demonstrated.