ORCID Profile
0000-0002-8797-3993
Current Organisation
University Of Strathclyde
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Publisher: AIP Publishing
Date: 2010
DOI: 10.1063/1.3276156
Abstract: We have systematically investigated the impact of device size scaling on the light output, spectral shift, and self-heating of 400 nm InGaN light-emitting diodes (LEDs). Devices with diameters in the range 20–300 μm have been studied. It is shown that smaller LED pixels can deliver higher power densities (despite the lower absolute output powers) and sustain higher current densities. Investigations of the electroluminescence characteristics of differently sized pixels against current density reveal that the spectral shift is dominated by blueshift at the low current density level and then by redshift at the high current density level, owing to the competition between the bandgap shrinkage caused by self-heating and band-filling effects. The redshift of the emission wavelength with increasing current density is much faster and larger for the bigger pixels, suggesting that the self-heating effect is also size dependent. This is further confirmed by the junction-temperature rise measured by the established spectral shift method. It is shown that the junction-temperature rise in smaller pixels is slower, which in turn explains why the smaller redshift of the emission wavelength with current density is present in smaller pixels. The measured size-dependent junction temperature is in reasonable agreement with finite element method simulation results.
Publisher: AIP Publishing
Date: 16-12-2013
DOI: 10.1063/1.4851875
Abstract: The transfer printing of 2 μm-thick aluminum indium gallium nitride (AlInGaN) micron-size light-emitting diodes with 150 nm (±14 nm) minimum spacing is reported. The thin AlInGaN structures were assembled onto mechanically flexible polyethyleneterephthalate olydimethylsiloxane substrates in a representative 16 × 16 array format using a modified dip-pen nano-patterning system. Devices in the array were positioned using a pre-calculated set of coordinates to demonstrate an automated transfer printing process. In idual printed array elements showed blue emission centered at 486 nm with a forward-directed optical output power up to 80 μW (355 mW/cm2) when operated at a current density of 20 A/cm2.
Publisher: SPIE
Date: 30-04-2010
DOI: 10.1117/12.853796
Publisher: Elsevier BV
Date: 11-2010
Publisher: IOP Publishing
Date: 28-04-2017
Publisher: IOP Publishing
Date: 29-11-2011
Publisher: The Optical Society
Date: 24-06-2011
DOI: 10.1364/AO.50.003233
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Publisher: IEEE
Date: 10-2009
Publisher: IOP Publishing
Date: 04-04-2008
Publisher: IEEE
Date: 09-2012
Publisher: IEEE
Date: 09-2013
Publisher: IEEE
Date: 11-2010
Publisher: IOP Publishing
Date: 03-12-2013
Publisher: Springer Science and Business Media LLC
Date: 24-04-2009
Publisher: IEEE
Date: 11-2010
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Ian Watson.