Growth Of ZnMgO/ZnO Multi-layer Structure On Si(111) Substrate And Preparation Of P-type Zn_1-xMg_xO By Using Pulsed Laser Deposition

ZnO is a direct wide band-gap semiconductor with E_g = 3.37 eV, and has large exciton binding energy of 60 meV, which assures efficient exciton emission even at high temperatures above room temperature. In addition, ZnO has also advantages involving low epitaxial growth temperature, more resistant to radiation damage, and relatively low cost. Owing to these merits, ZnO has attracted considerable attention as a promising material for optoelectronic devices such as UV light- emitting diodes (LEDs), Laser diodes (LDs) and photodetectors. To realize the potential applications of ZnO based optoelectronic devices, a key issue is the availability of device quality p-type ZnO. Meanwhile, it is necessary for the research of band-gap engineering of ZnO. Zn_1-xMg_xO alloy films can tune the band gap from 3.3 eV to 4.5 eV via substituting Mg on the Zn site in the ZnO films, while maintaining the wurtzite structure. Moreover, it is well matched to ZnO lattice. ZnMgO/ZnO heterosystem allows to realize quantum well (QW) structure with type-I band alignment, which can improve the emission efficiency of devices and modulate the working waveband. With a p-type Zn_1-xMg_xO layer, the p-n junction can achieve a wider bandgap. Therefore, it is very important to study the growth of high-quality ZnMgO/ZnO multi- layer structure and the fabrication of p-type Zn_1-xMg_xO.In this thesis, based on the introduction of past and current research on Zn_1-xMg_xO alloy films and ZnMgO -based devices, we deposit Zn_1-xMg_xO thin films on Si (111) substrates, and attempt to grow ZnMgO/ZnO multi- layer structure with low temperature ( LT ) ZnO buffer layer introduced. We also fabricate p- type Zn_1-xMg_xO films via monodoping of Li acceptor.The main results are obtained as follows:1. We have prepared high- quality C-axis oriented Zn_1-xMg_xO films on Si (111) substrate by pulsed laser deposition ( PLD ), and systematically analyze the influence of experimental parameters on the films quality. The optimal growth conditions are obtained.2. The crystallinity and surface morphology of Zn_1-xMg_xO film are improved byusing LT ZnO buffer layer. X- ray diffraction ( XRD ) pattern indicates the full-width at half- maximum ( FWHM ) of Zn,.xMgx0 ( 002 ) peak is 0.183°, and atomic force microscopy ( AFM ) image shows the film surface becomes more flat with a root mean square (rms) roughness of 3.68 nm.3. PLD technique is employed to fabricate ZnMgO/ZnO multi- layer structure on Si (111) substrate with an introduction of LT ZnO buffer layer, which is the first attempt in China. Second ion mass spectrum (SIMS) result indicates that Mg content oscillate periodically and forms steep distribution.4. P-type Zn0.9Mg0.jO thin films have been firstly realized via doping Li as the acceptor by using PLD. Hall-effect measurements indicate that the Li (0.4%)-doped p-type Zno.9Mgo.1O film grown at 550°C shows the lowest resistivity of 10.1 ftcm. Photoluminescence ( PL ) measurements show a blue shift of emission peak for the p-type Zno.9Mgo.1O film, which confirms the effective incorporation of Mg.Zn_1-xMg_xO film, ZnMgO/ZnO multi-layer structure, P-type Zn_0.9Mg_0.1O thin films, Pulsed laser deposition, Li doping.