A nanoporous structure is laying the groundwork for a new type of photodetector. A team from the State Key Laboratory of Petroleum Resources and Prospecting at the China University of Petroleum has developed the new photodetector, made for application with an infrared pulsed laser. "In the present work, we propose a type of infrared photodetector based on a nanoporous … structure, which is synthesized by a simple sol-gel method," they said in the study. This chart shows the photoresponse of the nanoporous ZnO/ n-Si sample under the laser pulse illumination at varying energy levels. T1 and t2 represent the corresponding time of the transient voltage peaks. The inset shows the linear relationship between the time interval and the laser pulsed energy. Courtesy of Science China Press. The new device is based on zinc oxide (ZnO), an environmentally friendly semiconductor that absorbs UV light effectively due to its wide bandgap. When combined with n-type silicon (n-Si) in a nanoporous structure, it demonstrated a unique photoresponse under near-infrared pulsed light irradiation. In the study, the researchers initially exposed the nanoporous structure to a 1,064 nm wavelength laser pulse with energy of 0.072 mJ. This produced two peaks — a higher photovoltaic (HPV) peak with an amplitude of ~ 235 mV and a subsequent lower photovoltaic (LPV) peak with an amplitude of ~ 13 mV. The researchers later increased the laser pulse’s energy to 0.332 mJ, which also increased the HPV peaks to ~ 275 mV. The LPV peaks, however, remained the same. The time interval between these peaks was found to be highly sensitive to such changes in the laser pulse energy. “Under illumination of one infrared laser pulse, this porous structure exhibits a double peak on a millisecond time scale in the decay of transient photovoltage,” the researchers said. They added that the new ZnO/n-Si structure shows potential to produce a simpler, inexpensive detector for an infrared pulsed laser. Photodetectors are already used in optoelectronic devices including digital cameras and night vision goggles. The work was funded by the National Key Basic Research Program of China, the Program on National Key Scientific Instruments and Equipment Development, the Beijing National Science Foundation and the Science Foundation of the China University of Petroleum. The research was published in Science China: Physics, Mechanics & Astronomy (doi: 10.1007/s11433-014-5459-4). For more information, visit www.upc.edu.cn.