ZnO Based Material And Nano Device Research

As the rapid development of silicon based semiconductor industry during the past decades, silicon itself can no longer satisfy the ever growing demands for semiconductor devices in some novel applications, such as high power electronics, high frequency circuits, optoelectronics, flexible displays, solar cells, etc. While silicon surely remains and will be dominant in semiconductor device family, researchers have already noticed the bottom neck of silicon before the real coming of the end of the Moore’s Law.Actually, by broadening scientific views on the period table of elements, there are more options beyond silicon, such as III-V, II-VI,2-dimensional crystals, etc. Zinc oxide (ZnO) is one of those emerging materials for future devices. With the assistance of quantum mechanics, one can understand and engineer the nano size world. This opens myriad opportunities and challenges in scientific researches and technology applications. Just like the exploration into silicon, the study of ZnO has gone deep into atomic level and has expanded widely to its counterparts. This transparent wide-bandgap binary oxide semiconductor, along with its resemblance have found a lot of advantages in applications such as thin film transistors, ultra-violet detectors, diluted magnetic semiconductors, gas sensors and even as chemical catalysts. This thesis focuses not only on ZnO and its doped versions, but also includes some counterparts, like ternary oxides (Zn2GeO4) and complex compounds (InGaZnO4). First principles calculation reveal the nature of band structure, density of states, and the relation to electrical, optoelectronic, magnetic, chemical properties. By virtue of X-ray photoelectron spectrometry, direct measurement of heteroj unction band offset is available, which is a good experimental means of studying semiconductor and understanding energy band theory. Finally, a novel light emitting device, denoted as ZnO/AAO, incorporating anodization and atomic layer deposition is proposed, which could possibly be useful in many occasions. The luminescence mechanism is studied by various characterization methods.