Investigation of Al-doped ZnO for UV Photosensing Application

• Main Authors: YANG, YAO-WEI, 楊曜維
• Other Authors: YOUNG, SAN-LIN
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/n4zbcn

碩士 === 修平科技大學 === 電機工程碩士班 === 106 === Zinc oxide (ZnO), a semiconductor material with a wide energy gap and high exciton binding energy, has been widely used in photovoltaic elements such as photo sensors, solar cells, and light-emitting diodes. The content of this thesis is to investigate the application of doping effect of Al to ZnO on the photosensing application. The thesis is divided into two parts. The first part focus on the Zn1-xAlxO films which is prepared by spin-coat method on p-type heavily doped Si wafers and Corning glasses, respectively, by changing the Al doping concentration and heat treatment temperature. The second part focus on Zn1-xAlxO nanorod array fabricated by chemical bath deposition (CBD) to grow nanorod array on ZnO seeded p-type heavily doped Si wafer by changing nanorod growth time and ZnO seed layer heating temperature for comparison. For Al doped ZnO films, the crystal structure is examined by XRD measurement. The XRD spectra show the strong c-axis preferred orientation with (002) diffraction peak and highly crystalline wurtzite structure. Comparing XRD with SEM, the results both show that the higher doping concentration obtains the smaller grain size. In terms of optical transmission spectrum analysis, it is found that the energy gap value increases as the Al doping amount increasing due to the generation of the BM effect as the Al doping concentration increasing caused by the blue-shifted phenomenon of the ultraviolet absorption edge. For electrical measurement analysis, the doping of Al increases the energy gap, decreases the grain size and distorts the crystal lattice, which all results the increase in resistivity. For Al doped ZnO nanorod array, it can be found that, the intensity of the main (002) diffraction peak increases with the increase of growth time indicating the prepared nanorod array has an enhanced degree of regularity. As for the SEM observation, the length of the nanorod is positively correlated with the growth time of the nanorod and the annealing temperature of the ZnO seed layer. For optical property analysis, the main peak intensity of the ultraviolet emission can be found by photoluminescent spectroscopy. With increasing the annealing temperature, the intensity of the ultraviolet radiation peak becomes larger and the green light emission peak in the visible light region becomes smaller. In terms of electrical analysis, an increase in the light-receiving area will facilitate light sensing capability due the increasing surface area of nanorods.