| 个人简介 | |
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 Prof. Shengjun Zhou Wuhan University, China |
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| 标题： Enhancing quantum efficiency of GaN-based LEDs | |
| 摘要： III-nitride light-emitting diodes (LEDs) have attracted considerable interest for applications in automotive front lighting, high-resolution full color displays, and visible light communication. However, the internal quantum efficiency of GaN-based LEDs is limited by high threading dislocation density in GaN film due to the lattice mismatch and difference in thermal expansion coefficients between the GaN and the substrate. In addition, the light extraction efficiency of GaN-based LEDs is relatively low due to total internal reflection of light at the GaN-air interface. We will outline the recent advances in improving crystalline quality and light extraction efficiency of III-nitride blue/green/ultraviolet LEDs. Recent work in our research group, including sputtered AlN nucleation layer, hybrid nucleation layer, patterned sapphire substrate (PSS), patterned substrate with silica array (PSSA), pre-well structure, staggered quantum wells, V-shaped pits, sidewalls nano-prism, thermally stable Ag mirror, and full-angle distributed Bragg reflector (DBR), will be discussed in this talk. We show that the sputtered AlN nucleation layer can enhance c-plane growth and suppress growth of GaN on cone region of PSS, which can effectively eliminate the undesirable GaN islands on the inclined sidewall of PSS and thus suppress the generation of TDs from coalescence of GaN islands. We find that the V-pit potential barrier height depends on the V-pit diameter, which plays an important role in determining the quantum efficiency, forward voltage and efficiency droop of green LEDs. We demonstrate efficient InGaN-based yellow (570 nm) LEDs with optimized three-layer staggered quantum wells (QWs) that are grown on patterned sapphire substrates. We observed a reduced threading dislocation density in the films grown on PSSA, attributing to the preferable vertical growth mode and reduced misfit at the coalescence boundary. Furthermore, a significant enhancement in light extraction efficiency can be achieved from InGaN/AlGaN-based ultraviolet LEDs built on PSSA owing to the large refractive index contrast between the epilayers and PSSA. We show that it is possible to improve both the light extraction efficiency and current spreading of flip-chip LED by incorporating a highly reflective metallic reflector made from Ag. Moreover, mini/micro-LEDs for high-definition displays will be introduced. | |
| 简介： Shengjun Zhou received the Ph.D. degree from Shanghai Jiao Tong University, Shanghai, China, in 2011. He is now a Professor at Wuhan University. His current research interests lie in the areas of GaN-based blue/green/ultraviolet LEDs, nitride semiconductors, nanoimprint lithography and direct laser writing with applications in electronic and photonic devices. He is well known as an industrial technologist. Prior to joining Wuhan University, he was a CTO at Quantum Wafer Inc. from 2011 to 2014, focusing on the development of high-brightness GaN-based high-power LEDs. He was a research fellow at University of Michigan, Ann Arbor, from 2014 to 2015. He received many academic awards including the National Youth Talent Support Program, IAAM Scientist Medal, IOP Publishing CHINA TOP CITED PAPER AWARD, distinguished Young Scholar of Hubei province, and Chutian Scholar of Hubei province. He has published more than 86 papers and holds over 26 patents. He is Co-chair of the Organizing Committee for IEEE ICEPT 2016 conference. He served as committee member for many conferences. | |
