Professor Kei May Lau received the B.S. and M.S. degrees in physics from the University of Minnesota, Minneapolis, and the Ph.D. degree in Electrical Engineering from Rice University, Houston, Texas. She was on the ECE faculty at the University of Massachusetts/Amherst and initiated MOCVD, compound semiconductor materials and devices programs. Since the fall of 2000, she has been with the ECE Department at the Hong Kong University of Science and Technology (HKUST). She established the Photonics Technology Center for R&D effort in III-V materials, optoelectronic, high power, and high-speed devices. Professor Lau is a Fellow of the IEEE, and a recipient of the US National Science Foundation (NSF) Faculty Awards for Women (FAW) Scientists and Engineers (1991) and Croucher Senior Research Fellowship (2008).
Nitride-based visible light emitting diodes (LEDs) with high external efficiency are widely used for a variety of applications including display backlights and general lighting. Many believe that volume production of GaN-based LEDs on large diameter silicon substrates is the key to realize competitive cost of solid state lighting, similar to the evolution of integrated circuits. Alternative solutions of integration using other well-developed technologies such as flip-chip bonding are interesting and practical. LEDoS projection technology will be presented as an example.
LED micro-displays offer diverse applications with their superior characteristics and unique performance, particularly in high light utilization efficiency (LUE), design simplicity (Backlight Unit (BLU)-free), long lifetime, and excellent visibility under bright day-light. Several LED based displays have been developed in recent years using both passive matrix (PM) and active matrix (AM) programming methods that can also be used as a novel source for projection display. With the light output power and efficiency of LEDs ever increasing, LED based projection displays are attracting more attention. However, no full-color projection has been reported to date.
In this talk, I will discuss the design and fabrication of GaN based light emitting diode on silicon (LEDoS) micro-displays with red, green, blue and UV colors by integrating monolithic LED micro-arrays and active matrix substrates using flip-chip technology. A silicon complementary metal-oxide-semiconductor (CMOS) active matrix driving scheme was designed to provide sufficient drive capability and individual controllability of each LED pixel. LEDoS micro-displays with 30×30 and 60×60 pixels on each single chip and pixel size down to 50 ?m will be presented. LEDoS micro-displays with emission wavelengths of 630nm, 535nm, 445nm and 380nm were fabricated. Combination of the red, green and blue LEDoS chips using a trichroic prism and a projection lens, the world’s first full-color 3-LEDoS projector prototype has been demonstrated.