Fabrication, Physical Character And Device Research Of ZnO Nanostructure

Semiconductor one-dimentional (1D) nanostructures have attracted much attention due to their novel properties. ZnO has a wide and direct band gap of 3.37 eV at room temperature with the large exciton binding energy (60 meV), which makes it promising application potential in optoelectronics. Based on the remarkable physical properties and the versatile applications of the ZnO material, ZnO nanostructures have been extensively studied.Pure ZnO of wurtzite mostly show n tape conductivity. This is mainly because many donor type defects exist in ZnO materials, these defects include oxygen vacancy (VO), zinc interstitial (Zni) and so on. In addition, unintentionally doped H is easy to form shallow donor (30 meV)in ZnO. Because of the existence of these donors, it can conpensate the shallow accepter, which is the socalled self-conpensation effect. So if you want to obtain the low resistant of p type ZnO, self-conpensation effect must be overcome, also accepter type impurity is incorporation into ZnO in order to realize the transformation from n type to p type. Moreover, the severe self-conpensation effect in ZnO makes the growth of repeatable and low resistant of P type ZnO material become a great obstacle that ZnO apply in Optoelectronic Devices. Therefore, fabrication and characteristics research of p type ZnO become the crucial factor of realizing application in Optoelectronic DevicesAt present, though the research to ZnO has already gained definite achievement, there are more work to work deeply because of complexity of ZnO, such as:1. The control of size and morphology in ZnO nano-material is far behind the nonoxide semiconductor nano-material. The main reason is that the synthesis difficulty of oxide semiconductor nano-material greater than nonoxide semiconductor. Furthermore, the exciton radius of ZnO is very small, which is only about 2nm. The majority of ZnO nano-materials fabricated are more than several ten nanometers, so it goes against displaying character change caused by quantum confinement in ZnO material. Whereas fine biological security and biological compatibility,excellent photoelectron characteristic determines that controllable and uniform small size of ZnO nano-material is still one of challenging great subject now.2. The research of P type ZnO material is still the key at the present time. For dopant of ZnO nano-material mainly fasten on V group element (As, P and Sb), also obtain P type and gain room electroluminescence. The preparation conditions is complex and hard to control, low repeatability, poor stability, some physical problems in photoelectric properties and doping process are not well solved yet, so there is a long distance to practicality of devices. The improvement of devices performance relay on the enhanced quality of P type, so how to obtain high, good stable and repeatable of P type ZnO nanostructure is still difficulty.3. Electrode contact characteristics of P type ZnO is still an obstacle to obtain high efficient ultraviolet luminescence. Excellent ohmic contact can effectively reduce contact resistance, also can improve injected current and efficiency of device. Though electroluminescence has been observed, the luminescence intensity is relatively weak. So choosing the proper metal, obtaining contact electrode that meet device requirement is the important problem that ZnO device research faces.This thesis is focused on fabricating and doping ZnO nanostructures and microstructure using a simple physical vapor deposition method. We also make the LED and UV detector devices based on the ZnO microwire.The following is the major results:(1) Well quality ZnO nanoflowers were fabricated by physical vapor deposition.The samples were characterized by scanning electron microscope, X-ray diffraction. From PL spectra, the ZnO nanostructures have good optical properties.(2) Arsenic doped ZnO nanobolts were fabricated by diffusion technique. GaAs wafer is chosen the As source. The measurement results suggest arsenic diffused into the crystal of ZnO and exsit in AsZn-2VZn form. PL spectra suggests that the emission peaks attributed to a conduction band to the arsenic -related acceptor transition and a donor to the acceptor pair transition were found.(3) Based on the ZnO microwire, ZnO microwire/SiO₂/GaN p-i-n heterjunctions LEDs were prepared. The LEDs can even emit intensive electroluminescence in blue-violet region at temperature 350 K; photoconductivity detector based on single ZnO microwire is studied, then the detector is treated using thermal diffusion method, investigate the change of response wavelength and responsibility, also analyse the reasons of these changes.