P-type Doping And Analysis Of ZnO Thin Films By L-MBE Dissertation For Doctoral Degree

ZnO has attracted much attention during recent years, due to its strong excitonic luminescence properties even at very high temperature (550K～850K), which make it an ideal material for the fabrication of UV lighting devices operated at RT and even higher temperature, with much lower excitation threshold than that of GaN and ZnSe. Till now, the main obstacle for the fabrication of ZnO based LEDs and LDs is its unipolarity, which means that it is very difficult to realize reliable and stable p-type ZnO films with high concentration. To solve this problem, one must firstly achieve high-quality undoped ZnO films with low background electron concentration, to eliminate the self-compensation effects of intrinsic point defects (IPD). At the same time, it is indispensable to grow ZnO films with high structural and luminescent qualities, in order to realize ZnO based LEDs and LDs with high performance. Along this vein, much effort was put on the realization of high quality intrinsic ZnO single crystalline films, with relatively lower defect density and electron concentration. And then various attempts were made on the p-type doping of ZnO films, including codoping method, using NH₃ as a dopant and N ion implantation. The reliable and reproducible p type ZnO films were achieved by N ion implantation eventually, the p-ZnMgO/n-ZnO p-n junction diode was also fabricated. The main innovative results are listed as below:1) Single crystalline ZnO films were achieved by laser molecular beam epitaxy (L-MBE), with a typical background electron concentration of 4.72×10¹⁶cm^-3. The FWHM of (0002) plane ω rocking curve was 213", and the RT excitation threshold of N-band stimulated emission was 200kW/cm². All the results are stable and reproducible.2) Glancing-incidence X-ray analysis (GIXA) was used in ZnO films and ZnMgO/ZnO hetero-structures. X-ray reflectivity (XRR) was exploited to provide quantitive evaluation of the surfaces and interfaces of ZnO films before and after annealing process.3) ZnO epilayers with ZnMgO/ZnO Superlattice(SL)-buffers were proposed and...