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8 April 2019

BluGlass highlights R&D on RPCVD of tunnel junctions at lower temperatures than MOCVD

BluGlass Ltd of Silverwater, Australia – which was spun off from the III-nitride department of Macquarie University in 2005 – has recently been sharing more of the details behind its R&D into creating tunnel junctions using its patented remote-plasma chemical vapour deposition (RPCVD) technology. BluGlass’ RPCVD technology focuses on creating gallium nitride (GaN)-based epitaxial wafers, for applications in areas such as power electronics as well as high-performance LEDs and micro-LEDs.

The firm made its first announcements on using RPCVD to manufacture tunnel junctions in December, and chief technology officer Ian Mann presented the first technical paper on the subject at February’s SPIE Photonics West 2019 conference in San Francisco.

BluGlass believes that the breakthroughs are significant for two fundamental reasons: the team has demonstrated performance improvements in light output of LEDs that incorporate tunnel junctions; and, as a result, they can demonstrate a potential solution to the industry-wide phenomenon of efficiency droop in high-brightness LEDs - a long-time constraint to the performance of LEDs, and a significant challenge for the incumbent manufacturing technique of metal-organic chemical vapour deposition (MOCVD).

That BluGlass can now demonstrate that RPCVD technology can be used to make tunnel junctions is, in Mann’s view, significant because it addresses the industry’s continuing focus on improving light output at lower costs (the dollars-per-lumen ratio). The world’s top-10 LED makers are responsible for about 60% of LEDs manufactured, and they compete largely on LED efficiency, as summarized in the ratio of costs necessary to produce increased brightness.

BluGlass is targeting an improvement in LED light output of greater than 10%, translating to a reduction in the dollar-per-lumens ratio of 10% or more. The firm reckons that these recent R&D results represent significant steps towards these targets. For a general LED market worth up to US$96bn by 2024 (forecasts Applied Market Research), improvements in the dollars-per-lumens ratio of this order would be significant.

BluGlass says that its RPCVD technology has now demonstrated that it can be used to deposit tunnel junctions at lower temperatures than MOCVD. This is the first step to manufacturing cascade LEDs, which promise to increase light output in LED devices without having to increase the physical size of the LED devices while doing so at current densities much closer to the peak LED efficiency, mitigating or potentially solving the problem of efficiency droop, BluGlass reckons.

Furthermore, RPCVD can be used to grow tunnel junctions on existing LEDs and, in contrast to manufacturing using MOCVD, avoids additional fabrication steps and processes (assuming that these are practicable in real terms).

BluGlass says that other advantages to RPCVD include sharper profiles of the dopants magnesium and silicon when deposited at lower temperatures.

While the R&D remains a work in progress, the results show promise, believes Mann. A particular focus is now on reducing the device voltage while maintaining the demonstrated increase in light output.

Early discussions with a number of commercial manufacturers are under way, notes the firm.

See related items:

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

BluGlass demonstrates functioning tunnel junctions, enabling cascaded LEDs

Tags: BluGlass RPCVD

Visit:  www.bluglass.com.au

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