SBIR Phase II: Direct Measurement of Wafer Temperature in White/UV LED Manufacture

This Small Business Innovation Research (SBIR) project will develop a highly accurate temperature measurement system that can be used in optimizing the growth of high brightness light emitting diodes for solid state lighting applications. This product does not currently exist due to technical difficulties in measuring the substrate or gallium nitride (GaN) epilayer in a region where they absorb energy. During Phase I of this program the company showed possible solutions to this problem that it can implement as the work progresses to Phase II. This SBIR Phase II program will address scientific and technical issues that has hindered the adoption of the Reflectivity Compensated Pyrometry (RCP) in the growth of GaN light emitting diodes (LEDs), the basis of solid state lighting sources. This program will result in a commercial instrument for directly measuring surface temperature during manufacture of visible and UV LEDs. Typical temperature variations during the growth of GaN-based LEDs results in a product which, even over a 2dimensional substrate, requires the LEDs to be separated into those with similar characteristics. Existing temperature measurements do not allow the accurate measurement of the substrate or the GaN epilayer because they are transparent at the measurement wavelength of ~1 micron. Commercially, this project will increase manufacturing productivity in wide-bandgap materials and LED manufacture by providing better process control data. The improved manufacturing yields of LED's enabled by this work will lead to more widespread adoption of LEDs for solid state lighting with the accompanying economic and environmental benefits. For example, the use of LEDs has already saved the US economy nearly 10 TWh per year (equivalent to one large power plant) of energy in the niche applications implemented so far.