Fabrication And Electrical Properties Of ZnSnN₂

ZnSnN₂ is a new ternary compound semiconductor with direct bandgap.It has the advantages of low cost,Earth-abundance of constituent elements,a forbidden bandgap of 1.4-2.0 eV,nontoxicity and thermal stability.With these properties and advantages,ZnSnN₂ has the potential to be applied in photocatalytic,photovoltaic and light-emitting applications.However,ZnSnN₂ still has the problems of low mobility and high electron concentration,which hinders its device applications.How to increase the mobility and reduce the electron concentration has become the focus of studying ZnSnN₂.The main content of this paper is to fabricate phase-pure ZnSnN₂ thin films,and investigate the effect of the conduction mechanism and scattering mechanism on the electron density and mobility.In this thesis,ZnSnN₂ thin films were prepared by reactive magnetron sputtering under different conditions.The effect of sputtering pressure,substrate temperature,gas flowrates of Ar and N₂,etc.on the structure?electron concentration and mobility was studied.The mobility and electron density were tuned by varying the sputtering pressure and the temperature dependence of electron density and mobility was analyzed and fitted.The detail is as follows:Firstly,ZnSnN₂ was deposited on K9 glass with DC and RF magnetron co-sputtering.By changing the substrate temperatures,the flow rates of N₂ and Ar,and bias voltage,etc.,a series of samples were made.The conditions to fabricate phase-pure ZnSnN₂ were found.Secondly,an alloy target made of Zn and Sn with the atomic ratio of Zn to Sn to be 3:1was used to fabricate ZnSnN₂ on K9 glass substrates.The effect of sputtering on the deposition was studied and the conditions to obtain phase-pure ZnSnN₂ were found.The effect of sputtering power was also studied and the highest mobility obtained is 28.1 cm²V^-1s^-1.Thirdly,why the mobility increases and the electron density decreases with an increase in the sputtering pressure was studied.The X-ray photoelectron spectroscopy and temperature-dependent Hall effect measurement were studied.The results show that lower sputtering pressure favors substitution of nitrogen with oxygen which is from vacuum residual.This further leads to higher electron density,impurity band conduction and low mobility;high sputtering pressure can reduce substitution of nitrogen with oxygen.This results in lower electron density,conduction band conduction,and high mobility limited by ionized impurity scattering.