Bridgelux Inc. of Livermore, California USA, announced today its first major lab-based development, a demonstration of 135 Lumens per Watt GaN-on-silicon-based LED technology.
GaN-on-silicon LEDs, widely seen as the holy grail of LED production efficiency, have been an illusive goal for the many companies that have pursued them. Bridgelux says that its demonstration represents the industry’s first commercial grade performance for a silicon substrate-based LED. The LED had a 350mA operating current and it required just 2.9 volts and under 3.25 volts at 1 amp. The 4730K CCT LED measures 1.5mm by 1.5mm.
The LED was produced on a standard 8-inch silicon wafer. Bridgelux contends that growing GaN on larger, low-cost silicon wafers that are compatible with modern semiconductor manufacturing can deliver a 75% improvement in cost over current approaches, which commonly use 2- to 4-inch sapphire wafers. Bridgelux points out that when scaling up production, large diameter sapphire and silicon carbide substrates are costly, difficult to process, and sometimes not widely available. This has kept production costs high, inhibiting widespread adoption of LED lighting in homes and commercial buildings.
Additionally, the Bridgelux devices are demonstrating a low forward voltage and superior thermal resistance which make them ideally suited for high-performance, illumination-grade applications. Optimization of the epitaxy process on 8-inch Si wafers will make LED manufacturing more compatible with existing automated semiconductor lines. Bridgelux notes however that "A number of the processes [used to produce conventional LEDs] ... would need to be modified to eliminate some materials that are currently used, and which are incompatible with silicon substrate manufacturing."
Bridgelux sees the move to silicon substrates as a revolutionary step for the LED industry. Over the past 5 years, Bridgelux CTO Dr. Steve Lester has shepherded a quietly-dedicated GaN-on-Silicon R&D team. Concurrently, industry-wide research and development of GaN growth on silicon has increased, both for production electronic devices and in the labs for optical technology. Bridgelux says that its GaN on silicon performance levels today are comparable to state-of-the-art sapphire-based LEDs available 12-24 months ago. Over the course of the next two to three years, the company anticipates the delivery of its first commercially viable GaN-on-Silicon products that meet performance requirements of LED lighting. “Bridgelux’s achievement is a significant reflection of the strength of our leadership in Silicon materials and epitaxial process technology," said Bill Watkins, Bridgelux CEO. “The significantly reduced cost-structures enabled by Silicon-based LED technology will continue to deliver dramatic reductions in the up-front capital investment required for solid state lighting. In as little as two to three years, even the most price-sensitive markets, such as commercial and office lighting, residential applications, and retrofit lamps will seamlessly and rapidly convert to solid state lighting.”