No abstract

AlGaN multi-quantum-well (MQW) deep-ultraviolet (DUV) light-emitting diodes (LEDs) fabricated on sapphire substrates with emission at 227 nm are demonstrated. A remarkable enhancement in the DUV LED output power was achieved by using a thin AlGaN quantum well only 1.3 nm in thickness, with atomically flat hetero-interfaces, together with an AlN buffer layer of reduced threading dislocation density. The AlGaN-MQW DUV LEDs exhibited single emission peaks. The output power was 0.15 mW with injection current of 30 mA and the maximum external quantum efficiency was 0.2%, under room temperature pulsed operation.

We observed remarkable enhancement of 254‐280 nm deep ultraviolet (UV) emission from AlGaN multi quantum wells (MQWs) by using low threading dislocation density (TDD) AlN templates on sapphire substrates. High‐quality AlN templates were fabricated using ammonia pulse‐flow multi‐layer (ML) AlN growth technique by metal‐organic chemical vapor deposition (MOCVD). The photoluminescence (PL) intensity of AlGaN‐QW with emission wavelength of 280 nm was increased by approximately 30 times by reducing the full width at half‐maximum (FWHM) of X‐ray diffraction (102) ω‐scan rocking curve (XRC) of AlGaN buffer on ML‐AlN from 1214 to 488 arcsec. We obtained similar emission enhancement for AlGaN QWs with emission wavelengths of 254, 260 and 270 nm. We found that PL intensity of the QWs were rapidly increased when FWHM of XRC (102) is reduced as narrow as 800‐1000 arcsec. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)