Ultraviolet light-emitting diodes operating in the 340nm wavelength range and application to time-resolved fluorescence spectroscopy

Abstract

We report on the development of UV light-emitting diodes in the 340nm wavelength range, based on quaternary AlGaInN quantum-well active media. Output powers up to 1mW from small area devices (<100μm diameter) directly off a planar chip have been achieved. The devices have been operated as subnanosecond pulsed sources to demonstrate their applicability to compact time-resolved fluorescence spectroscopy.

340 nm pulsed UV LED system for europium-based time-resolved fluorescence detection of immunoassays

“…3, right. Similar results were also reported in [12], thus indicating that UV LEDs are spectrally stable. The inset figure shows the normalized LED irradiance in a logarithmic scale.…”

“…340 nm LED has until now been hampered by limited power [11]. Closest prior art has been LEDs at 340 nm with output power up to 1 mW and dimension <100 μm in diameter which were employed in fluorescence lifetime measurements [12].…”

Semiconductor ultra-violet light-emitting diodes for flash photolysis

“…Epitaxial growth of the active material was on sapphire substrates, which are transparent at this wavelength and hence light emission was extracted from the polished backside through the 500 m thick substrate. Mesa-type devices were etched using chlorine-based RIE, and a high-temperature annealed multilayer Ti/Pd/Al/Ti/Au metallization served as the contact to n-type AlGaN (Peng et al, 2004). An opaque Ni/Au p-electrode 50 m in diameter defined the optical aperture, as illustrated in the inset to Fig.…”

“…High efficiency longer wavelength blue (460 nm) and green (530 nm) Indium Gallium Nitride (InGaN)-based LEDs have been recently successfully used in biological applications including voltage-sensitive dye imaging (Venkataramani et al, 2005). Recent developments in the material and device science of the more challenging AlGaN and AlGaInN-based LEDs emitting in the 280 and 340 nm wavelength ranges, with relatively high output power and operating speeds, has seen these devices being tested for a number of applications ranging from bioaerosol detection to water purification (Davitt et al, 2005a;Peng et al, 2004). In this paper we demonstrate the use of custom-designed and fabricated compact UV light-emitting diodes (LEDs), based on the quaternary AlGaInN semiconductors, as a flexible means to perform flash photolysis of caged neurotransmitters.…”

340nm UV LED excitation in time-resolved fluorescence system for europium-based immunoassays detection

“…Until recently, 340 nm LEDs could provide only a few milliwatts and were only employed for some special applications 12,13 , but lower power levels prevented the employment in immunoassays. Now improvements of 340 nm UV LEDs have made them applicable with numerous lanthanide based chelates having excitation peaks in this wavelength range.…”