| Zn O has always been considered as a potential material for highly efficient ultraviolet optoelectronic devices and has many applications such as light-emitting diodes, laser diodes and ultraviolet photodetectors. Zn O has a direct wide bandgap with 3.37 e V. Compared with Ga N(25 me V) and Zn S(38 me V), it has a larger exciton binding energy of 60 me V, which is far higher than the thermal energy. This can lead to exciton recombination emission at room temperature. Therefore, Zn O is more suitable for ultraviolet optoelectronics than other wide-band gap semiconductors. Moreover, Zn O has a variety of micro/nano structures, which exhibit different optical characteristics. However,The electroluminescence of the Zn O/p-Ga N heterojunction LEDs emits mainly from the interface between Zn O and Ga N and the red-shift of Zn O near band edge emission are often found in the devices. In our work, we prepared Zn O micro/nano structures and fabricated Zn O nano/micro photoelectric devices according to the problem of the research on Zn O. The innovative research works of this article are:1. Zn O quantum dots with the diameter of 5 nm were fabricated on ITO glass by using a simple spin-coating method. Zn O quantum dots/p-Ga N heterojunction ultraviolet light-emitting diodes were made by using Zn O quantum dots as the emission layer and p-Ga N as the hole injection layer. The quantum confinement effect of QDs led the LED to emit light mainly from the QDs layer. As the result, a LED with pure ultraviolet electroluminescence has been achieved. The emission peak was located at 382 nm and the full width at half maximum was narrow. Compared with the other devices, Zn O quantum dots/p-Ga N has excellent characteristics of high intensity and good monochromaticity.2. Zn O microwire clusters with great green emission had been fabricated by chemical vapor deposition method. Heterojunction light emitting diodes were prepared based on Zn O microwires and p-Ga N. When the forward bias was applied on p-Ga N, ultraviolet emission with 395 nm was obtained. When the forward was applied on Zn O, orange emission from 450 nm to 700 nm was observed. Heterojunction light emitting diodes were prepared based on Zn O microwires and n-Ga N. When forward was applied on Zn O, green emission located at 490 nm was obtained. At last, we discussed the mechanism of electroluminescence.3. We carried out a new method to realize the nitrogen doping of Zn O single crystal by N-plasma treatment. The acceptor-related bound exciton(A0X) emission was observed in the low temperature photoluminescence. The NO acceptor level was formed. We found the vibrational mode of oxygen lattice shift to the large wave number from Raman scattering spectra. The surface work function of Zn O with nitrogen plasma treatment became larger, the Fermi level moved to valence band, the hole concentration increased. It could be confirmed that the N atom was successfully doped into Zn O. The doping mechanism was discussed. We constructed a Zn O-based homojunction device, which I-V curve displayed perfect rectification performance. This indicated that the p-Zn O with nitrogen doped was obtained.4. We had fabricated Ag nanoparticles modified Zn O film based UV photodetector by magnetron sputtering and metal ion sputtering method. The Zn O/Ag NPs/Zn O sandwich structure presented an absorbance gain from 385 nm to 356 nm and a blue shift of photoluminescence. It was demonstrated that Ag nanoparticles improved the performance of the Zn O films. The photo responsivity of Ag modified Zn O film photodetector increased one order of magnitude and the rise and fall time significantly reduced. |
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