250 nm AlGaN light-emitting diodes

We report $\mathrm{AlGaN}$ deep ultraviolet light-emitting diodes (LEDs) at 250 and $255\mathrm{nm}$ that have short emission wavelengths. For an unpackaged $200\times 200\mu \mathrm{m}$ square geometry LED emitting at $255\mathrm{nm}$ , we measured a peak power of $0.57\mathrm{mW}$ at $1000\mathrm{mA}$ of pulsed pump current. For a similar device emitting at $250\mathrm{nm}$ the peak output power of $0.16\mathrm{mW}$ was measured at $300\mathrm{mA}$ of pulsed pump current. Progress is based on the development of high quality $\mathrm{AlGaN}$ cladding layers with an $\mathrm{Al}$ content up to 72%, which were grown over $\mathrm{AlGaN}∕\mathrm{AlN}$ superlattice buffer layers on sapphire substrates. These $n\text{-}{\mathrm{Al}}_{0.72}{\mathrm{Ga}}_{0.28}\mathrm{N}$ layers were doped with $\mathrm{Si}$ up to about $1\times {10}^{18}{\mathrm{cm}}^{-3}$ and electron mobilities up to $50{\mathrm{cm}}^2∕\mathrm{V}\bullet \mathrm{s}$ were estimated. High resolution x-ray diffraction studies gave a narrow (002) rocking curve with full width at half maximum of only $133\mathrm{arc}\sec$ .