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Bluglass Demos Functioning Tunnel Junctions

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Breakthrough enables high-brightness cascaded LEDs - a world first for GaN semiconductors

Australian firm BluGlass has closed out the calendar year with market announcements that cover breakthrough technology development, expansion of its Silverwater facility, and an update on its continuing negotiations with global LED manufacturer Lumileds.

Giles Bourne, managing director and CEO of BluGlass, said: “This breakthrough development of our technology is very exciting. These results confirm the potential of our patented RPCVD technology to solve a number of the manufacturing challenges associated with the industry's incumbent processes, and importantly allows us to start discussions with a range of potential high-value partners in high-brightness LED and other semiconductor market segments.

“Having made significant and intensive investment and development over a number of years, and with 62 global patents to protect our IP, we now plan to take these results to market to capitalise on the broader applications for our technology, and deliver the best-possible return on shareholder investment.”

Technology breakthrough

BluGlass has announced that its manufacturing process, Remote Plasma Chemical Vapour Deposition (RPCVD) has successfully demonstrated functioning tunnel junctions to enable high-brightness, cascaded LEDs, in a world first for GaN semiconductors.

A cascaded LED is a device where two or more LEDs are grown in a continuous vertical stack using what's called a tunnel junction to interconnect the multiple LEDs in a single chip. Cascaded LEDs address a fundamental constraint inherent in high-brightness LEDs, called ‘efficiency droop', where the efficiency of the light output drops as the driving current increases.

A simple solution to combat efficiency droop is to replace a single LED chip with two or more LED chips side by side: light can then be generated by driving each LED at a lower current matched to their peak efficiency. However, the use of multiple LED chips in this way increases cost and the space required to accommodate multiple chips. In today's markets the demand for increasingly smaller devices is growing, including in the automotive industry, where there are strict limits on physical device dimensions.

A better solution is to use cascaded LEDs - a single chip that has two or more LEDs stacked vertically in a single chip. This enables more light output, but without efficiency droop. Efficiency droop is reduced because multiple LEDs are working together to create light output, and power is increased by stacking voltage, not current, with no additional space required. The vertical solution also increases the number of devices than can be made from a single wafer - further reducing manufacturing costs.

This is a significant breakthrough for BluGlass, as a successful cascaded LED is not yet commercially available, and is not easily achieved by the incumbent manufacturing technology, MOCVD. Cascaded LEDs could enable smaller, cheaper and higher performing LEDs.

The RPCVD process is uniquely able to produce these critical enabling tunnel junctions in the LED device by capitalising on its inherent competitive advantages. RPCVD operates at several hundred degrees cooler than the incumbent technology, and replaces expensive and toxic ammonia (which also introduces unwanted hydrogen into the process) with an inert nitrogen plasma. It is also able to achieve the required activation needed for a working cascaded LED during growth. MOCVD relies on complicated and time-consuming additional processing to achieve the required activation.

BluGlass manufacturing facility

BluGlass has taken delivery of the first of two new specialised manufacturing platforms, an Aixtron AIX 2800 G4 commercial scale MOCVD platform that BluGlass will retrofit with its RPCVD manufacturing technology. With the second platform expected in January 2019, these will add capacity for industry collaborations around the use of RPCVD for tunnel junction-enabled cascaded LEDs, microLEDs, and power electronics devices. The supporting clean-room build and fit out underwritten by its capital raise from mid-year is nearing completion.

Continuing commercial negotiations with Lumileds

Separately, BluGlass remains in active negotiations with global LED manufacturer Lumileds to extend the collaboration and to potentially enter a commercial agreement to licence BluGlass' RPCVD technology, as notified to the market at the BluGlass AGM held on 19 November 2018.



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