In this talk I will give a review of my previous research on stimulated emission and lasing of ZnO and recent development of optoelectronics based on ZnO. Semiconductor p-n junction photodetectors have advantages of high breakdown voltage, fast response speed, and low reverse currents. Most p-n junction UV photodetectors are based on III-V GaN semiconductor. ZnO is a direct wide band-gap II-VI semiconductor that exhibits excellent photosensitive properties at the UV wavelength. ZnO is more radiation-resistive than other semiconductors and is therefore a strong candidate for fabricating photonic devices that can operate in extreme environments and conditions such as space and nuclear reactors. Historically, fabrication of p-type ZnO has been a major challenge because ZnO is normally an intrinsic n-type semiconductor due to presence of oxygen vacancies and zinc interstitials. Based on our recent breakthroughs in growth of high quality p-type ZnO based on As doping, several ZnO-based devices have been fabricated. We report here spectral responsivity and I-V curve for a ZnO p-n junction UV detection detector. The photocurrent responsivity reached a maximum of 0.91 A/W near the band-gap of ZnO at 6.0 V reverse bias. The dark current is very small under a reverse bias from 0 to 4.0 V. These results demonstrate that ZnO p-n junction photodetector is very sensitive to UV photons and suitable for UV detection.
Dr. Ping Yu is an Associate Professor at the Department of Physics and Astronomy, University of Missouri. He graduated from Nankai University with B. Sc and M. Sc. degrees, and got his PhD degree from Hong Kong University of Science and Technology. He spent two years in Technical University of Denmark and Niels Bohr Institute at University of Copenhagen. He then had been a postdoctoral associate at Department of Physics, Purdue University. Dr. Ping Yu is a physicist whose research combines semiconductor optics, laser physics and biomedical optical imaging. He has spent his career exploring basic physical processes in optics and optical materials, and applying his acquired knowledge to the development of novel materials, devices, and biomedical imaging systems. The research contributions for which Dr. Ping Yu is best known are: (1) his pioneering work on room temperature stimulated emission, lasing and gain mechanism of ZnO epitaxial thin films and microstructures; (2) his contribution to understanding optical polarization and electronic states of vertically coupled semiconductor quantum dots; and (3) his innovation in holographic optical coherence imaging and fluorescence mediated tomographic imaging. His research has been supported by the National Science Foundation CAREER Award as well as funds from National Health Institute.