LEDs ♦ news digest
was deposited using an e-beam evaporator. A high electron mobility light-emitting transistor (HEM-LET) with ohmic source and semitransparent Schottky drain was made simultaneously.
Ni/Au (20/200 nm) was used as the gate metal and a SiN x/AlO (15/8 nm) stack insulator used as the gate dielectric for the HEM-LET, in order to single out the Schottky drain. Finally, the device was annealed at 400degC for 10 minutes in N2 ambience.
EL emission at room temperature
The team measured the current- voltage characteristics, and the EL and photoluminescence (PL) spectra. (A 266nm laser was used to excite the AlGaN/GaN heterostructure for the PL measurement).
and PL spectra
The team also experimented with another Schottky metal, Pt/Au and found similar results concluding this is a general property of metal-AlGaN/GaN Schottky diodes.
From these results, the researchers think it would be possible to realise synchronous radio-frequency/ optical communications using an AlGaN/GaN HEM- LET, and an all-on-chip opto-coupler for III-nitride power electronics.
They also suggest that the metal-AlGaN/GaN light- emitting Schottky diode provides an alternative for micro-display with unique advantages. The back electrode is served by a high-mobility 2DEG channel, and the pixel is defined by the top Schottky contact, eliminating th mesa etching process and current spreading design and allowing for a higher resolution and smaller pixel size.
Plessey expands its
distribution network for GaN- on-Si LEDs
Solid State Supplies appointed for the UK and Ireland
With semi-transparent Ni/Au (5/6 nm) Schottky metal, the team reported clearly seeing EL emission from the Ni/Au-Al 0.25Ga 0.75 N/GaN Schottky diode at room temperature when the forward bias is higher than 2.2V. The EL intensity becomes stronger at a higher bias.
They found that the EL spectra consisted of not only yellow and blue luminescence but also a narrow GaN band-edge UV component at 3.4eV, similar to the PL spectra of the AlGaN/GaN heterostructure as shown in graph c) above.
Both the EL and PL spectra are from the GaN layer; no emission from the thin AlGaN barrier layer was detected. The yellow/blue is due to radiative transition of electronics from conduction band of a shallow donor to a deep acceptor in the GaN layer. Its relative intensity, compared with GaN band- edge UV emissions decreased with increasing bias/ current or laser excitation intensity in both the LE
Plessey announced that it has entered into a distribution agreement with Solid State Supplies Ltd, an electronics distributor headquartered in Redditch, UK, to expand its European network with coverage in the UK and Ireland market for its GaN- on-Si LED products.
John Macmichael, managing director of Solid State Supplies said: “Plessey’s GaN-on-Si technology looks set to cause major disruption in the LED lighting market. Our in-house lighting division is already geared up to support lighting and luminaire designers with these new LEDs. We look forward to a very bright future in partnership with Plessey.”
David Owen, Plessey’s regional sales director, added: “Plessey is very pleased to join forces with a distributor that has a focused lighting division already up and running, helping the significant number of lighting and luminaire makers in the UK. Solid State Supplies has a strong portfolio of products to support the lighting eco system which is
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www.compoundsemiconductor.net 79
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