| Summary: | 碩士 === 南臺科技大學 === 光電工程系 === 104 === Carbon (C), currently one of the most mature wide-bandgap semiconductors due to its many excellently properties, including a wide bandgap , high electron mobility , high breakdown electric field , high thermal conductivity , as well as good mechanical and chemical stability. In this project , Carbon thin films were prepared on Si substrates with nano-porous Si (NPS) buffer layers. C-based photodetectors were fabricated to explore the potential applications of developed technologies.
NPS thin films with uniformly distributed Si nano-crystallites were prepared on heavily doped p+type(100) Si wafers by anodic etching processes with low etching current density of 20mA/cm2. Secondly , the passivation layer of Carbon films were prepared by sputtering on NPS layers. To improve the devices’ performance, Carbon films were also prepared upon oxidized NPS (ONPS) layers that were formed by rapid-thermal oxidizing (RTO) processes from the NPS layers. Finally, inter-digitated nickel (Ni) electrodes were deposited on the front sides of the devices to complete the MSM photodiode structures.
The results showed that Carbon films on Si with NPS and ONPS buffer layers had quite good crystallinity and high UV responses. The deposited Carbon films on ONPS exhibited high photo-responsivity for incident wavelengths between 300nm and 500nm, corresponding to the near UV ranges. The developed C/ONPS photodiodes achieved high photo-to-dark current ratio up to about 443 at 350-nm incident light. Although the photo-to-dark current ratio fell to 42.1 when temperature raised to 250℃, but still better than the device that without carbon films. Those results demonstrated that Carbon-on-ONPS photo detectors had high UV sensitivity, thus indicating their high potential in UV-sensing applications.
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