| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 98 === ZnO is II-VI compound semiconductor material which belongs to hexagonal structure. The large energy gap of 3.37eV and large exciton binding energy of 60meV makes ZnO a good candidate for many optoelectronic devices. Though ZnO is a well-studied material, lots of research is being done especially considering the possibility of making ZnO based Light emitting diodes (LED’s). One of the main challenges for ZnO based LED’s is the difficulty in making it a p-type ZnO. There are many groups who are attempting to pursue research to improve hole conductivity in this system.
In this thesis, ZnO thin films and Cu-doped ZnO thin films are grown on Corning 1737F glass by radio frequency magnetron sputtering. Both pure ZnO thin films and Cu-doped ZnO thin films only show ZnO(002) plane reflections in XRD result, indicating that the thin films have preferred orientation along c-axis, due to self-texture. For undoped ZnO samples, the results show that with increase in the growth temperature, PL intensity increases and sheet resistance decreases. This was attributed to enhancement of crystallinity and reduction in grain boundary density as the growth temperature is increased.
The PL peak position of Cu-doped ZnO thin films with heat-treatment in O2 ambiance at 700℃ samples shift from 443 nm to 433 nm. The emission at 433 nm is come from Cu+ state to T2 state intra-band transition, thus we consider that the Cu can replace Zn in O-rich condition. The electrical properties are measured by hall measurement and also using plasma frequency which obtain from FTIR spectrum to calculate carrier concentration. The result shows nopt. is higher than nHall, we infer that there is a band-tail in the bottom of conduction band, then the effective mass should be proportion with carrier concentration.
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