Plasma Immersion Ion Implantation Modification Of The P-type Zno Thin Films

Energy. materials and information are the leader of new technology revolution and the backbone of modern civilization. Semiconductor materials is the cornerstone of the modern information society, and it's also the important foundation of the new energy development and utilization. Germanium (Ge) is the first semiconductor material which was studied and used of. In the next few decades, semiconductor material has been developed rapidly, from narrow gap to wide band, from infrared to ultraviolet. Silicon(Si) is the most widely used semiconductor material. Zinc Oxide (ZnO) is a new type of semiconductor material with a direct band gap of 3.37 eV and a large exciton binding energy of 60 meV, which is gradual rising in recent years. Since the recent discovery of its ultraviolet (UV) excitonic emission at room temperature, ZnO has been expected for a material of light emitting diode (LED) and laser diode (LD) in UV or blue spectral region, and has attracted extensive attention of the world-wide scientists and research groups. However, due to its asymmetric doping limitations, p-type ZnO is very difficult to obtain. The main challenge during the research of ZnO now is to fabricate excellent,repeated and steady p-type ZnO. In this paper, we introduce a new technique to fabricate p-type ZnO film, which is plasma immersion ion implantation (PⅢ) method. We have managed to fabricate p-type ZnO by using this method. The main content of this thesis as follows:(ⅰ) Al doped ZnO (AZO) films are grown by radio-frequency magnetron sputtering and later laid into the vacuum PⅢchamber. The input gas (N source) is discharged by a 600W radio-frequency power supply and uniform inductively coupled bulk plasma is generated. The parameters of the generated plasma are diagnosed by Langmuir double probe and multi-channel optical emission spectroscopy (OES). The substrate holder connects to a negative high-voltage pulsed power supply with a rise time is10-6s. The pulse duration and frequency are adjustable and the maximum amplitude of the bias is 60kV. The high voltage bias can effectively enable N element incorporate into AZO films, which forms N-Al co-doped ZnO. After the implantation, implanted N can be activated by controlling the annealing process, which improves the crystallinity and makes p-type conversion of ZnO achieved,(ⅱ) When the ZnO films have been fabricated, characterization of prepared ZnO films is carried out, such as electrical, optical and morphological properties. We used the X-ray diffraction instrument (XRD), Hall effect measurement, X-ray photoelectron spectroscopy (XPS), Photoluminescence (PL) etc. to do the measurement. The properties of the ZnO films can be known after characterization, and it will help our future work.(ⅲ) The key of p-type conversion of ZnO films is the control of defects and impurities in ZnO films. When acceptors are dominant, ZnO shows p-type property. On the contrary, ZnO shows n-type. We can control the forms of N defects in ZnO films by changing the implantation gas. The plasma generated need to provide abundant N+ rather than N2+ to form much more acceptors in the films because No are acceptor-like defects but (N2)o are donor-like defects. Such plasma with abundant N+ can be obtained when the implantation gas is composed of 25% NO and 75% O2. By the post-implant annealing, implanted N can occupy O vacancies and provide holes concentration, and that is contributing to p-type conduction. In other cases, such as pure NO or pure N2, the number of N2+ in the plasma largely exceeds that of N+, therefore not good for and inhibiting the p-type conversion of ZnO films.