Device Architecture and Fabrication

This chapter begins with a section explaining market segmentation of today’s white LED products. For deeper understanding of LED devices and products, the reader will encounter technologies used in LED devices from their earlier days to the most recent. Two major phase-changes of the LED industry will be emphasized: Semiconductor materials shifted entirely from indirect to direct bandgap materials for high luminescence efficiency, and emergence of the high-brightness blue LED paved a path to the white LED and consequently to today’s vast fields of LED applications. The reader will then realize that market demands towards high-power applications around 2000 drove the industry to introduce various chip architecture and packaging technologies. After surveying those chip architecture technologies in the second section, the rest of the chapter explains predominantly device fabrication processes and material ingredients in production order: Epitaxy, device fab, and phosphor integration, by product/application basis wherever applicable. The last section is to emphasizes the importance of tolerance analysis using a normal-distribution exercise related to a packaging process.