Info
Info
News Article

Researchers Simplify Fabrication Of Nanowire UV-LEDs On Silicon

News

KAUST team demonstrates dislocation-free AlGaN nanowires that spontaneously coalesce to allow device fabrication without planarisation

Figure (a) Top-view SEM image of device structure, and tilted-angle SEM of the nanowires in the inset; (b) STEM-HAADF image of coalesced AlGaN nanowires with schematic showing LED layer structure and measured UVLED emitting ~300 nm.

There is a growing demand for mercury-free, environmentally friendly, compact UV LEDs for disinfection applications. Existing AlGaN-based planar UVLEDs, however, suffer from high dislocation densities, low light extraction efficiency and poor
p-doping efficiency, which limits the irmaximum output power to several mWs at 20 mA.


Dislocation-free AlGaN nanowires have shown better
p-doping and light extraction efficiency but the growth of self-assembled, vertically oriented and uniform nanowires has remained a challenge. Furthermore, the nanowire-based LEDs require a planarisation process to first fill the gap between nanowires and then to make ohmic contacts. Planarisation is expensive and significantly reduces the light extraction efficiency due to the extreme absorption of the filling materials in the UV wavelengths.

Now researchers at KAUST (King Abdullah University of Science and Technology), led by Bilal Janjua and Haiding Sun, have reported synthesising AlGaN nanowires that spontaneously coalesce with a high density of ~1 x 10
10 cm-2 (filling factor >95 percent) using plasma-assisted MBE on silicon.

They say that their approach, published in the journal
Nanoscale, offers a viable way to easily fabricate ultra-thin UV LEDs on low-cost and scalable silicon substrates, without the planarisation step.

In addition, they demonstrated AlGaN quantum disks (Qdisks are the nanowire equivalent of quantum wells) in the nanowires and showed segregation of Al/Ga locally within the Qdisk (nanoclusters) that enhanced luminescence, similar to that reported in InGaN-based quantum wells.

Al
xGa1-xN /AlyGa1-yN multiple quantum-disks should have superior carrier confinement and thus improve the optical performance of the device. Device simulation results showed a large overlap of the electrons and holes wave functions in the active region because of the quantum confinement effect.

LEDs emitting at ~303 nm with a narrow FWHM (~20 nm) of the EL spectrum were demonstrated by using a large active region ("˜active region/nanowire length-ratio' ~ 50 percent) embedded with 15 stacks of Al
xGa1-xN/AlyGa1-yN Qdisks.

According to the researchers, this is early work and more can be done to further improve the device performance. Nevertheless, they say their pendeo-epitaxy technique offers the possibility of simplifying the fabrication of a wide range of UV-nanowire devices such as lasers, photodetectors, modulators, and silicon integrated photonics.

"˜Self-planarized quantum-disks nanowires ultraviolet-B emitter utilizing pendeo-epitaxy'
by Bilal Janjua et al, Nanoscale, 2017, DOI: 10.1039/C7NR00006E.




AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS

Info
×
Search the news archive

To close this popup you can press escape or click the close icon.
×
Logo
×
Register - Step 1

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in:
 
X
Info
X
Info
{taasPodcastNotification}
Live Event