Interdigitated 구조 기반 Zn2SiO4:Mn 전계발광 및 광검출 기능 소자 개발

Abstract

A Zn2SiO4 has a wide band gap of 5.5 eV and excellent chemical and thermal stability was selected as a phosphor host and Mn2+ ions were selected as an activator for green light emission to realize a MOS-structured device that functions as electroluminescence and also plays a photodetection role through silicon. The phosphor emission layer formation method used the Sol-Gel method in which a ZnO:Mn precursor solution is spin-coated on a silicon wafer, and heat treated at a high temperature to form a Zn2SiO4:Mn2+ phosphor thin film. An ITO transparent electrode was formed through RF Magnetron sputtering on the phosphor thin film, and an Al electrode was formed through thermal evaporation under the substrate to complete a MOS-structured electroluminescent device. As a result of PL and PLE measurement using a fluorescent spectrophotometer, the main excitation band was observed at 258 nm, which was confirmed to be due to the charge transition of Mn2+ ions to the Zn2SiO4 host. EL spectrum was measured at 25 Vrms and 400 Hz, and compared to the PL spectrum, the wavelength peak shifted from 524 nm to 523 nm, and the half width also increased from 41 nm to 46 nm. As an electrical characteristic of electroluminescence, the light emission of the device started at the positive zero-crossing point of the AC voltage and showed a relatively high emission intensity at the cathode, which is analyzed to be due to the asymmetric charge injection characteristics and conduction band structure of Zn2SiO4:Mn2+. In addition, the horizontal AC power application method using the upper interdigitated electrode structure showed more uniform and less flicker light emission characteristics compared to the existing vertical MOS structure. The photoconductivity effect in silicon-based devices was also observed through the 632 nm laser irradiation experiment, which showed an increase in current during the transport of light-generated charges by the AC electric field. Under the zero bias condition, the dark current showed a very low value at the level of μA, and the photocurrent increased by more than 100 times when irradiated with light, showing excellent photodetection sensitivity. Through the additional response time measurement, it was confirmed that the time response characteristics according to the incident light wavelength clearly appeared. When irradiated with a 632 nm laser in the zero bias conditon, the rise time was measured to be about 0.04 seconds and the fall time was about 0.039 seconds, proving an excellent response speed of less than ms units.