Illuminating Tomorrow

Guangyu Liu and Jing Zhang, Ph.D. candidates in electrical engineering, whose research aims to improve lighting technologies and reduce energy consumption, received the 2012 Scholarship in Optics and Photonics from the International Society for Optics and Photonics.

Their research focuses on improving the light-generating efficiency of solid-state LEDs (light-emitting diodes), which use much less energy than incandescent lighting and promise to exceed the efficiency of fluorescent lighting.

In addition to theoretical and computational work, the students use the state-of-the-art facilities in Lehigh’s Center for Photonics and Nanoelectronics to design, grow, characterize, fabricate and test devices.

Each has several research projects. Zhang works to identify important structures based on wide bandgap semiconductor alloys to address the difficulty in achieving high optical gain (light amplification) for deep (low-wavelength) ultraviolet lasers. She also seeks to boost the efficiency and device performance in visible-light LEDs by using new substrate and nanophotonics structures.

Zhang also studies the use of nanostructures based on III-Nitride semiconductors for developing thermoelectric materials that enable the active removal of heat from high-power devices such as lasers, transistors and solar cells.

Liu studies current leakage caused by “efficiency droop” in LEDs. The light-generating efficiency of LEDs peaks at low current but begins to diminish significantly at the high current at which low-cost LEDs operate. (Low-cost LEDs require the devices to operate at high current level.) Liu works with other Ph.D. students to solve “efficiency droop” by using new types of barrier designs in LEDs.

Liu is also developing new types of quantum wells to improve the efficiency of green LED diodes. She fabricates quantum-dot structures on a new material that shows potential for ultra-high, uniform dot densities.

Liu and Zhang both earned bachelor's degrees from Huazhong University of Science and Technology in Wuhan, China. Since enrolling at Lehigh, each has published more than 40 articles in journals and conference proceedings. They are both advised by Nelson Tansu, the Class of 1961 Associate Professor of Electrical and Computer Engineering.

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