Investigation On The Fabrication And Properties Of P-type ZnCdO Thin Film Synthesized By Magnetron Sputtering

In recent years,the fabrication of ZnO barrier and quantum layer materials synthesized by band gap engineering were investigated extensively for the sake of obtaining ZnO-based light emitting diodes?LEDs?ultraviolet luminescence.Considering that CdO has the direct band gap of 2.3 eV and possesses the same valence with Zn.Furthermore,with the incorporation of Cd into ZnO,the substitution of Cd for Zn site takes place and the band gap of ZnCdO?ZCO?decreases with the increase of Cd concentration.Therefore,ZCO ternary alloy is the appropriate quantum layer material.In this work,we fabricated ZCO films and investigated its optical and electrical properties detailedly in order to lay the foundation of the development of ZnO-based LEDs and LD,and achieve the exciton recombination focused,efficient and stable,wavelength tunable electroluminescence.Theoretical research revealed that the valence band maximum of CdO is much higher than that of ZnO.Thus,alloying ZnO with CdO will narrow the band gap and shift the valence-band edge to higher energy,thus decreasing the activation energy of the defect acceptor states,which exhibits advantages to obtain low resistivity and high hole concentration p-type conduction ZCO films.In this work,we synthesized the Na-doped,N-doped and Na-N codoped ZCO films by RF magnetron sputtering followed by rapid annealing treatment.The conduction type of ZCO film converted from n-to p-type through regulating annealing conditions.The characterization methods include X-ray diffraction?XRD?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,ultraviolet absorption,photo luminescence?PL?and Hall-effect measurements.In the fabrication of ZCO:Na film,by changing the ratios of argon to oxygen gas flow?Ar:O₂?,we obtained the ZCO:Na film with different Na content.The best p-type conduction ZCO:Na film possesses a carrier concentration of 1.13×10¹⁶ cm^-3,and exhibited a band gap tunable range?3.37-3.04 eV?.Hall-effect measurements results underscore the importance of annealing temperature(T_ann)and annealing time(t_ann)in obtaining p-type ZCO:Na film.It is found that the recipe to acquiring p-type ZCO:Na film is drive out Na_i and H_i while preserving Na at the substitutional sites,which can be realized through managing the dissociation of Na-relevant neutral complexes under appropriate T_ann and t_ann.The optimal p-type ZCO:Na film was obtained when the T_ann and t_ann were set to 600°C and 30 min,respectively,which possesses a carrier concentration of 2.98×10¹⁷ cm^-3.In the synthesis ZCO:N films,by changing the ratios of nitrogen to aron gas flow?N₂:Ar?,we fabricated the hexagonal wurtzite structure ZCO:N film with highly?002?preferential orientation.As the N₂:Ar increases from0:1 to 4:1,the absorption edge for the samples exhibits blue shift,achieving the14.2%band gap regulative vague.It is found that ZCO:N film deposited at the N₂:Ar of 1:2 shows the optimal p-type behavior,which has a carrier concentration of1.10×10¹⁷ cm^-3.Base on the p-type conversion of ZCO:Na and ZCO:N films,we further investigated the fabrication of Na-N codoped ZCO film[ZCO:?Na,N?].It is demonstrated that the presence of Na_Zn and N_o acceptors are answerable for the p-type behavior in ZCO:?Na,N?film by the analysis of XPS results.When the Ar:N₂ was set to 1:2,ZCO:?Na,N?film possesses the optimal p-type conduction properties with carrier concentration of 7.84×10¹⁸ cm^-3 and the resistivity of 30.9?·cm,which is conducive to accelerating the development of quantum layer materials.