Diluted potassium hydroxide is all what it takes to boost AlGaN nanowire UV LEDs

April 27, 2018 // By Julien Happich
In an article titled "Surface-Passivated AlGaN Nanowires for Enhanced Luminescence of Ultraviolet Light Emitting Diodes" published in ACS Photonics, researchers from the King Abdullah University of Science & Technology (KAUST) reported that a simple passivation step using diluted potassium hydroxide was enough to offer a nearly 50% performance boost to UV LEDs built from the spontaneously grown, self-aligned AlGaN Nanowires.

Although they represent an improvement over planar AlGaN-based UVLEDs, AlGaN nanowires ultraviolet light emitting diodes are known to suffer from low efficiency partially because of the strong surface recombination caused by surface states such as an oxidized surface. Doing away with complex surface passivation methods found in literature, often requiring the use of toxic chemicals, the researchers at KAUST achieved an effective passivation of the AlGaN nanowires surface through a simple immersion in a diluted potassium hydroxide (KOH) solution for up to 40 seconds.

Inspection via transmission electron microscopy shows the nanowire structures remained almost intact after the passivation process, their surface being slightly flattened, while ultraviolet light output from devices built using such passivated AlGaN nanowires increased their light output by nearly 50% (the paper reports 49.7%), at a wavelength of 338nm.

For the experiment, the AlGaN nanowires were grown on titanium-coated silicon substrates using an ebeam evaporator, and top/bottom metal contacts were applied after the passivation process using a standard UV contact lithography process to create a 300x300μm2 UV LED.