250 nm AlGaN light-emitting diodes

We report AlGaN deep ultraviolet light-emitting diodes (LEDs) at 250 and 255 nm that have short emission wavelengths. For an unpackaged 200x200 mum square geometry LED emitting at 255 nm, we measured a peak power of 0.57 mW at 1000 mA of pulsed pump current. For a similar device emitting at 250 nm the peak output power of 0.16 mW was measured at 300 mA of pulsed pump current. Progress is based on the development of high quality AlGaN cladding layers with an Al content up to 72%, which were grown over AlGaN/AlN superlattice buffer layers on sapphire substrates. These n-Al0.72Ga0.28N layers were doped with Si up to about 1x10(18) cm(-3) and electron mobilities up to 50 cm(2)/V.s were estimated. High resolution x-ray diffraction studies gave a narrow (002) rocking curve with full width at half maximum of only 133 arc sec. (C) 2004 American Institute of Physics.