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Apr 24th, 2014
GaN-on-Silicon devices is now entering the volume production for power devices and LED
Yole Développement interviewed David Williams, VP of Business Development at Translucent, a provider of GaN on Si epiwafer, on the business, technology trends and IP…
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According to Yole Développement data (available in the report “GaN-on-Si Substrate Technology and Market for LED and Power Electronics”), GaN on Si epiwafer will be a market of around $ 320 million in 2020 for the production of LED and power devices. Just counting the open market ($133 million in 2020) the forecast CAGR through the period 2015 to 2020 is ~42% - which we agree will see strong growth in the latter part of the decade. Translucent is targeting this market; let’s discover how it will happen…

Yole Développement: Can you give us an overview of Translucent?
David Williams: Translucent Inc. was founded as an advanced semiconductor materials company in 2001. Australian listed public company Silex Systems Limited (ASX:SLX) (OTCQX:SILXY) has been the sole investor in Translucent, which remains a subsidiary of Silex. The initial market focus was the rapidly growing photonics/optical communications market, but this evaporated in the early 2000’s after the telecoms downturn.  Translucent quickly adapted and continued to develop its core materials technology with a shift in focus to other markets. Today, Translucent has two product offerings, mainly GaN-on-Si epiwafers and Ge-on-Si epiwafers.
These products are aimed at the Power Electronics and Concentrating Photovoltaics (CPV) markets, respectively.

YD: What is original in Translucent activities related to Gan on Si?
DW: Translucent’s GaN-on-Si epiwafers are more precisely described as an advanced GaN-on-insulator product. The intermediary between the GaN and the silicon is a single crystal Rare Earth Oxide (REO) transition layer. The composition of the REO is chosen so that it is lattice matched to the silicon on its lower surface. The upper surface is engineered to be compatible with standard GaN MOCVD processes. As well as providing a transition layer from the silicon wafer to the GaN epi layer, the REO provides functionality that may be useful to III-N device manufacturers: just to name a few, like bow control, chemical and electrical barrier between the substrate and the GaN device layer.

YD: What is Translucent's business model and what is the commercialization status?
DW: Translucent is offering epiwafers to its customers. Translucent is presently developing its manufacturing process and production equipment in preparation for full commercialization. Demonstration of 2DEG HEMT structures on GaN deposited on the single crystal REO layer (in turn deposited on silicon wafer) has been completed and validated. REO-on-silicon production has recently been scaled to 200mm, whilst MOCVD deposition of GaN-0n-REO is currently being optimized on our 150mm platform. The final step on the path to commercialization - transferring the GaN-on-REO process to 200mm is expected to be completed in the near future. Additional potential commercial applications beyond power electronics (eg. advanced LED/photonics substrates) will be investigated in the future.

YD: How do you see the growth of GaN epiwafer?
DW: The more attractive market for Translucent is power devices. LED has a lower value at processed wafer level and has difficulties to support the added value and cost structure of engineered wafers.

For power devices, this is totally different: based on Yole Développement data (available in the report “Gan on Si technology and market” report) GaN on Si epiwafer will be a market worth around M$ 320 million in 2020 for the production of LED and power devices. Looking at just the open market component (around $133 million by 2020), the CAGR from 2015 to 2020 is approximately 42%, which obviously indicates a very strong growth trend in the latter half of this decade and beyond. We at Translucent agree with this forecast – there is already very strong industry interest building for GaN-on-silicon epiwafer products.

YD: What has been Translucent's patent strategy up to now for GaN on Si technology?
DW: Importantly, in addition to the noted technical and performance benefits, we believe that Translucent’s unique REO-based approach underpins a very strong IP position. The company’s extensive patent portfolio provides comprehensive protection of the silicon/REO and the REO/GaN interface material technology. We believe this has considerable merit in a climate of very public patent disputes in the GaN-on-silicon field.

At the beginning, we patented REO buffer layers. We believe that Translucent’s unique REO-based approach underpins a very strong IP position. We then extend our patent portfolio to silicon/REO, the REO/GaN interface and GaN nucleation layer. We are presently developing 2DEG HEMT structures for power application. Since REO is also a high-k dielectric (relative permittivity 12 to 15), we can use it at the top of a device structure as for in-situ passivation and the gate dielectric. We have been active in protecting the materials-based IP. We now have comprehensive protection of the entire GaN-on-si epiwafer using the REO technology. 

Transistor IP (see picture below):
1.    Interface between silicon and REO material.  - pre-straining silicon, bow engineering
2.    Bulk Oxide – breakdown voltage, bow engineering
3.    Oxide termination – MOCVD nucleation, GaN interface properties
4.    Nucleation layer – transfer of bow from oxide, GaN parameters such as FWHM
5.    Gate dielectric – in situ passivation, 2DEG performance

YD: When do you think the patent battle will start?
DW: Just one case has been made public, between IR and EPC. Nothing else seems to have started until now. The market is just starting at the moment, so it is too early for such patent case. We thing that translucent is providing an original solution for the bow management of GaN on Si epiwafers and the patent portfolio of Translucent is here to support the company growth.

YD: What will be the next step of the industry according to you?

DW: Well, I think that we are about to see a consolidation of the involvement of the power electronic companies in GaN on Si. M&A will happen within 18 months so that the big companies get access to the GaN on Si technology when it will be ready for mass production. This day is approaching rapidly…


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