| ZnO is regarded as a novel II-VI compound semiconductor with direct band gap.ZnO High-efficiency p-n homojunctions can be achieved realizing stable and excellent p-type ZnO films,which is important for application of sustainable development material in the field of optoelectronics.There are many reports about fabricating p-type ZnO films,but an important problem needs to be taken into consideration that obtained p-type ZnO films possess low mobility or hole concentration,attributing to low solubility of p-type dopants and native donor defects.It is the key problem to choose appropriate acceptor and doping method to obtain stable p-type ZnO films with high mobility and hole concentration and more attention should be paid to these kinds of acceptors and preparation methods,which are regarded as the most promising methods to overcome the difficulty hampering p-type conductivity.In our paper,molecular beam epitaxy,ion implantation,dynamic annealing and annealing with high pressure have been combined to obtain stable and excellent p-type ZnO films by doping with group IA and VA elements and to realize the aim of increasing the density of acceptor defects and restrain donor defects.The paper includes:1.ZnO films were grown by plasma-assisted molecular beam epitaxy(MBE)on c-plane sapphire substrates.The impacts of experimental parameters on the conductivity of ZnO films have been investigated,which includes MgO buffer layer,Zn temperature,oxygen flux,substrate temperature,and NaNO3 pressure.It reduces lattice mismatch between ZnO film and c-plane sapphire substrate and improve crystal quality of single-crystalline ZnO films to use MgO buffer layer.It improves the conductivity of ZnO films and reduce surface roughness of ZnO films to optimize appropriate Zn temperature and oxygen flux and it produces p-type ZnO films to choose appropriate substrate temperature,and NaNO3 pressure.2.ZnO films possess good crystal quality and conductivity,which attributes to using plasma-assisted MBE technique and c-plane sapphire substrate.It improves the density of acceptor defects and stability of p-type ZnO films to choose Li and N dual acceptor ion implantation with Na and N ion implantation.Crystal recovery and dopant activation through dynamic annealing are needed.ZnO films were were implanted with 80 keV N ions at a fluence of 1.7×1015 cm-2,30 keV Li ions at a fluence of 2.0×1015 cm-2,which possess good p-type characteristics with hole concentration of 2.3×1016cm-3,hole mobility of 0.8 cm2V-1s-1,and resistivity of 328.9Ω·cm.ZnO films were were implanted with 90 keV N ions at a fluence of 1.7×1015 cm-2,130 keV Na ions at a fluence of 2.0×1014 cm-2,which possess good p-type characteristics with hole concentration of 1.24×1016 cm-3,hole mobility of 8.37 cm2V-1s-1,and resistivity of 80.7 Ω·cm.3.ZnO films possess good crystal quality and conductivity,which devotes to combining plasma-assisted MBE technique and c-plane sapphire substrate.O ions were introduced by implantation to occupy the sites of oxugen vacancies to fabricate p-type ZnO films.Crystal recovery through rapid annealing are needed.ZnO films were were implanted with 100 keV O ions at a fluence of 2.0×1015 cm-2,which possess p-type characteristics with hole concentration of 1.4×1014 cm-3,hole mobility of 0.45 cm2V-1s-1,and resistivity of 10.43 Ω·cm.ZnO films and ZnO films with high resisitivity were grown by plasma-assisted molecular beam epitaxy(MBE)on c-plane sapphire substrates.Annealing with high pressure were performed to restrain the density of oxygen vacancies in ZnO films and ZnO films with high resisitivity in O2 atmosphere.4.ZnO films possess good crystal quality and conductivity by using plasma-assisted MBE technique and a-plane with c-plane sapphire substrate.It improves the density of acceptor defects choose N and P ion implantation,respectively.O ions were introduced by implantation to occupy the sites of oxugen vacancies to fabricate p-type ZnO films amd to improve stability of p-type ZnO films Crystal recovery and dopant activation through dynamic annealing are needed.ZnO films were were implanted with 120 keV N ions at a fluence of 2.0×1016cm-2,130 keV O ions at a fluence of 2.0×1016cm-2,which possess good p-type characteristics with hole concentration of 1.1×1019 cm-3,hole mobility of 1.6 cm2V-1s-1,and resistivity of 0.353 Ω·cm.ZnO films were were implanted with 180 keV P ions at a fluence of 1.7×1016cm-2,100 keV O ions at a fluence of 1.7×1016cm-2,which possess good p-type characteristics with hole concentration of 1.5×1018cm-3,hole mobility of 1.4 cm2V-1s-1,and resistivity of 0.672 Ω·cm. |
PDF Full Text Request