BluGlass presents latest data on development of RPCVD-grown tunnel junctions for LEDs

At the SPIE Photonics West 2019 conference in San Francisco (5-7 February), BluGlass Ltd of Silverwater, Australia – which was spun off from the III-nitride department of Macquarie University in 2005 – has presented its latest remote-plasma chemical vapor deposition (RPCVD) technical data on its recent development of RPCVD-grown tunnel junctions for LED applications.

As an invited speaker, chief technology officer Dr Ian Mann presented the paper ‘RPCVD of Group III Nitride Tunnel Junctions for LED Applications’ outlining the technical detail and competitive advantages of the firm’s patented RPCVD technology for manufacturing GaN-based tunnel junctions (which are a key building block for cascade LEDs). RPCVD-enabled cascade LEDs could address the industry challenge of efficiency droop in LEDs, it is claimed.

A cascade LED is where two or more LEDs are grown in a continuous vertical stack using a tunnel junction to interconnect multiple LEDs in a single chip. This is highly desirable as it could prevent the fundamental challenge of efficiency droop in high-performance LEDs, by decreasing the required current while increasing the light output. Cascade LEDs are expected to enable smaller, cheaper and higher-performing LEDs – the three key areas of interest of the LED industry. To date, functioning tunnel junctions, and hence cascade LEDs, have been prohibitively difficult to produce.

In December, BluGlass announced that it had capitalized on the unique low-temperature advantages of RPCVD to demonstrate functioning tunnel junctions.

“These exciting results help validate the strong commercial potential of our RPCVD technology to solve a number of the manufacturing challenges associated with the industry’s incumbent processes,” says managing director Giles Bourne. “Importantly this allows us to further discussions with a range of potential high-value partners in the LED and other semiconductor market segments, as we seek to capitalise on the broader commercial applications for our technology.”

There is significant interest in the potential of cascade LEDs and tunnel junctions, as efficiency droop is a well-known problem associated with high-performance GaN-based LEDs. It is a fundamental property of LEDs where the efficiency of the light-output drops as the driving current increases, which means that the majority of today’s high-powered LEDs are being operated outside of their peak efficiency.

BluGlass reckons that RPCVD-grown tunnel junctions could be commercially compelling for high-performance nitride devices, including for high-value applications such as LEDs for automotive lighting, UV LEDs for water purification, high-power laser diodes for industrial machining applications and high-efficiency multi-junction concentrated solar cells.

The LED market is predicted to reach US$96bn by 2024, with the high-brightness automotive segment (a potential first adopter of cascade LEDs due to strict performance and size requirements) expected to comprise $22bn by 2024 (23% of the total market).

BluGlass says that the RPCVD process can produce these critical enabling tunnel junctions in the LED device by capitalizing on its inherent competitive advantages. RPCVD operates at hundreds of degrees cooler than incumbent metal-organic chemical vapor deposition (MOCVD) technology and replaces expensive and toxic ammonia with an inert nitrogen plasma. It is also able to achieve the required activation needed for a working tunnel junction during growth. MOCVD relies on complicated and time-consuming ex-situ processing to achieve the required activation. This unique ‘as-grown and activated p-GaN’ (or AAG) technology is a fundamental advantage of RPCVD, says BluGlass.

The firm says that, since December’s announcement of its tunnel-junction capabilities, it has received strong industry interest and looks forward to progressing those discussions with these latest technical details.

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BluGlass demonstrates functioning tunnel junctions, enabling cascaded LEDs

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Visit: www.bluglass.com.au