Study On Al-N Co-doped ZnO Films Deposited By High Power Pulsed Magnetron Sputtering

Zinc oxide?ZnO?has attracted much attention due to its unique physical properties,such as a wide straight band gap?3.37 eV?,high exciton binding energy?60 meV?.These properties make ZnO widespread applications in solar cells,laser diodes and light detectors and so on.However,due to many intrinsic defects,such as V_O?Zn_i?Zn_O and O_Zn,the p-type ZnO is particularly difficult in fabrication and stabilization,which has become the bottleneck in the development and application of ZnO-based optoelectronic devices.High power pulsed magnetron sputtering?HiPIMS?is a novel plasma source,which has the characteristics of a high plasma density and a high ionization rate.During depositions,it is ions to participate mainly in the reaction rathan than neutral particles in normal magnetron sputtering.As a result,the films prepared by HiPIMS demonstrate different properties.Therefore,in view of the poor stability of nitrogen doped p-ZnO,this thesis research the the influence of experimental process parameters on the properties of Al-N co-doped ZnO films in HiPIMS where N₂ is used as the nitrogen source.The plasma characteristics are diagnosed by a time-resolved emission spectroscopy for the proposal of deep understanding the growth machanism.The main research contents and conclusions are as followings:?1?The effects of N₂ flow on the crystal structure,surface morphology and electrical properties of Al-N co-doped ZnO films are studied.As the nitrogen flux is increasing,the carrier concentration is increased,and the film switchs from n-type to p-type and then back to n-type.At 20 sccm N₂ flow rate,the Al-N co-doped ZnO film exhibits a stable p-type conductivity with the resistivity of 4.51 ?cm,a carrier concentration of 5.47 × 10¹⁷cm^-3and a hall mobility of 2.7 cm²/Vs.?2?It is obtained that the deposition rate,the surface morphology and the electrical properties of ZnO films are closely corelated to the deposition temperature.The highest deposition rate of 64.50 nm/min is obtain at 220 ? which is slightly decreased at 350 ?.The results of Seebeck effect and Hall effect test indicate that the ZnO thin film prepared at 280 ? exhibits a p-type conductivity with the resistivity of 0.35 ?cm,a carrier concentration of 5.34 × 10¹⁸cm^-3and a hall mobility of 3.41 cm²/Vs.?3?The role of working pressure.When the working pressure is less than 0.6 Pa,the structure of the grown ZnO film is wurtzite with only the?002?facet.When the working pressure is 1 Pa,the composite is grown with Zn₃N₂ but preferential in?002?facet with.At 0.3 Pa working pressure,p-type ZnO exhibits the resistivity of 10.36 ?cm,a carrier concentration of 1.84 × 10¹⁷cm^-3and a hall mobility of 4.11 cm²/Vs.OES result shows that N⁺/N₂⁺reaches a maximum of 0.75,which is beneficial to the No acceptor formation.?4?The effect of pulse width.When the pulse width is 50 ?s,a good crystal quality is grown with the minimum FWHM of ZnO?002?lattices is 0.48.The reason is that the energy of the sputtered particles are suitable for nucleation and growth of ZnO.OES results show that as the pulse width is increasing,the ratio of N⁺/N₂⁺ is firstly increased and then decreased.