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226–273 nm AlGaN deep‐ultraviolet light‐emitting diodes fabricated on multilayer AlN buffers on sapphire

2008; Wiley; Volume: 5; Issue: 9 Linguagem: Inglês

10.1002/pssc.200779303

1862-6351

Hideki Hirayama, Tohru Yatabe, Norimichi Noguchi, Tomoaki Ohashi, Norihiko Kamata,

Photocathodes and Microchannel Plates

Abstract We demonstrated AlGaN multi‐quantum‐well (MQW) deep‐ultraviolet (UV) light‐emitting diodes (LEDs) with wavelengths in the range of 226–273 nm on sapphire substrates. We achieved low threading dislocation density (TDD) AlN templates, formed through an ammonia (NH 3 ) pulse‐flow multilayer (ML) growth technique, which were suitable for deep UV LEDs. The edge and screw‐type dislocation densities in these AlGaN buffer layers on ML‐AlN were 7.5×10 8 and 3.8×10 7 cm –2 , respectively, as observed from cross‐sectional transmission electron microscope (TEM) images. We obtained single‐peaked operations of the LEDs with emission wavelengths of between 227‐273 nm. The output powers of the 253 nm and 261 nm LEDs were 0.4 mW and 1.0 mW respectively with injection currents of 100 mA, while maximum powers of 1.04 mW and 1.65 mW respectively were obtained under room temperature (RT) CW operation. The output power of a 227.5 nm LED was 0.11 mW with an injection current of 10 mA, and a maximum power of 0.15 mW was obtained under RT pulsed operation. The maximum external quantum efficiencies of the 261 nm and 227.5 nm LEDs were 0.23 and 0.2%, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)