| Summary: | 博士 === 國立成功大學 === 光電科學與工程學系 === 101 === In this dissertation, zinc oxide-silicon dioxide (ZnO-SiO2) nanocomposite films were grown via a co-sputter system at room temperature (RT). High-resolution transmittance electron microscopy (HRTEM) results reveal that the diameter of ZnO nanoparticles in the ZnO-SiO2 nanocomposite was within 3 mm to 7 nm. In addition, the ZnO-SiO2 nanocomposite films have wide bandgap characteristics. Thus, they are used to fabricate a p-GaN/i-ZnO/n-ZnO:In (p-i-n) light-emitting diode (LED) and a flexible solar-blind photodetector (PD).
First, ZnO-SiO2 nanocomposite films were placed between p-GaN and n-ZnO:Ga (GZO) to obtain a p-i-n heterojunction structure LEDs. This device exhibited an emission peak at 376 nm in the electroluminescence (EL) spectrum while operating at a current injection of 9 mA. A flat-top nanosecond laser (FTNL) was used to anneal the ZnO-SiO2 nanocomposite layer simultaneously. The intensity of the EL emission peak of ZnO-SiO2 nanocomposite LEDs at 376 nm at a current of 9 mA with FTNL treatment was approximately 1.4 times greater than those of LEDs without FTNL treatment. Furthermore, the full-width at half maximum (FWHM) of the EL emission of FTNL-treated LEDs at 376 nm was narrower than those of LEDs without FTNL treatment. Thus, the FTNL treatment of ZnO-SiO2 nanocomposite LEDs could induce the recrystallization of distributed ZnO nanoclusters and reduce the defects in the ZnO-SiO2 nanocomposite layers.
Second, an organosilicon compound [SiOx(CH3)] was used as the buffer layer between the ZnO-SiO2 nanocomposite film and the substrate in fabricating a flexible solar-blind PD. The compound can reduce the internal stress of the ZnO-SiO2 nanocomposite film and improve the characteristics of the PD to produce a low-noise, flexible solar-blind PD with high detectivity. The maximum responsivity value and quantum efficiency of the device at -10 V were 0.75 A/W and 482% at 240 nm, respectively. This result indicates a high deep ultraviolet (DUV)-to-visible rejection ratio (R = 240 nm/R = 400 nm) of five orders of magnitude, which was due to the internal gain in the device. Finally, after bending measurements, the DUV-to-visible rejection and responsivity of flexible PDs slightly attenuated when the radius of the curvature decreased. However, all PDs retained their favorable photoelectric properties, especially the flexibility of the PD caused by the organosilicon compound thin film. These results indicate that the flexible ZnO-SiO2 nanocompsite solar-blind PD works when the bending radius is larger than 8.6 mm. The buffer layer [SiOx(CH3)] released the stress on the ZnO-SiO2 nanocomposite during bending, enhanced the characteristics of PDs, and suppressed the reduction of photoelectric properties.
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