1. Laser Thermal Lab; Department of Mechanical Engineering; University of California; Berkeley CA 94720 USA
2. Department of Materials Science and Engineering; University of California; Berkeley CA 94720 USA
3. School of Mechanical Engineering; Sungkyunkwan University; Suwon 440-746 South Korea
4. School for Engineering of Matter; Transport and Energy; Arizona State University; Tempe AZ 85287 USA
5. Research Center for Light Emitting Diodes (LED); Zhejiang Normal University; Jinhua 321004 P. R. China
6. Division of Materials Sciences and Engineering; Lawrence Berkeley National Laboratory; Berkeley CA 94720 USA