The Electroluminescence Property Of Silicon-based Rare Earth Oxide Semiconductor Eu₂o₃

As a kind of special semiconductor material,rare earth oxides semiconductors have distinct advantages over third generation wide band gap semiconductors represented by ZnO,GaN and so on.The band models of rare earth oxides semiconductors also include special extremely narrow 4f band besides conduction and valence bands.The relative position of 4f band has significant effect on the genesis of charge carriers of rare earth oxides semiconductors.The favoured energy process will be the excitation of electrons from the valence band to 4fn+1 band or from 4fn band to the conduction band,leading to an intra-atomic 4f-4f transition,instead of a broad interband transition.Hence,electroluminescence(EL)devices based on rare earth oxides films not only have these advantages of rare earth ions such as plentiful emission lines,high purity and luminous efficiency,but also solve the problem that rare earth ions have low solid solubility in host materials.Moreover,the devices can obtain a low operating voltage due to excellent semiconductor properties.More importantly,in terms of a type of semiconductor material,lattice parameter of Eu2O3 is 10.86A,and it has found almost zero crystal lattice mismatch with Si(lattice parameter is 5.43A).This makes silicon-based Eu2O3 film EL devices perfectly compatible with current increasingly mature metal-oxide-semiconductor(CMOS)technology.In this thesis,we deposited Eu2O3 films on Si substrates by the magnetron sputtering technology,prepared silicon-based Eu2O3 film EL devices and obtained the characteristic red EL of Eu3+ ion.This work not only helps alleviate the problem that silicon-based red light-emitting device(LED)has the general low efficiency,but also greatly extends applied realms of rare earth oxides material and provides a new approach and path for the research of silicon-based LED.The main results of this research work in this thesis are as follows:(1)Eu2O3/P+-Si devices were prepared and the characteristic red EL of Eu3+ ion was obtained by applying the forward bias to the devices:Eu2O3 films were deposited on P+-Si substrates by magnetron sputtering method.The luminescence properties and the crystal structure of the films at different annealing conditions were investigated by X-ray diffraction and PL spectrum measurement.The corresponding optical band gap values of these films were calculated.Eu2O3/P+-Si devices were also prepared and the characteristic red EL of Eu3+ ion was obtained.Meanwhile,the luminescence mechanism was discussed in detail.In addition,luminescence performance of devices has preliminary improved from such aspects as film thickness,annealing temperature and annealing flow rates.(2)Double layer structure Eu2O3/Tb2O3/P+-Si devices were prepared.The EL intensity and turn-on voltage of the devices were improved by introducing Tb2O3 film as hole injection layer:A layer of Tb2O3 film was first deposited on P+-Si substrates by magnetron sputtering method,and Eu2O3 film was deposited on an upper surface thereof afterward.Double layer structure Eu2O3/Tb2O3/P+-Si devices were prepared.The devices could achieve stronger red EL of Eu3+ ion by introducing Tb2O3 film as hole injection layer.The luminescence mechanism of the devices was discussed in detail and the impact of Tb2O3 layer on luminescence performance was studied.Besides,the devices also were further optimized from such aspects as Tb2O3 film thickness,annealing temperature,annealing flow rates and so on.(3)The co-sputtering Eu2O3:Tb3+ devices were prepared and the characteristic red EL of Eu3+ ion were obtained by applying the forward and reverse bias to the devices:Eu2O3:Tb3+ film was deposited on P+-Si substrates by co-sputtering of Eu2O3 target and Tb metal target,and Eu2O3:Tb3+/P+-Si EL device was prepared.The luminescence properties of the device at different bias conditions were investigated by applying the forward and reverse bias to the device,respectively.The luminescence mechanism of the devices was also discussed,and the roles of Tb3+ ions doped into Eu2O3 film via co-sputtering in red EL of Eu3+ ion were analyzed.Furthermore,luminescence performance of the devices has been improved by changing the type and resistivity of Si substrate.(4)The optimization of co-sputtering Eu2O3:Tb3+ device performance:Firstly,the effects of different W6+,In3+ and Ca2+ metal ions doping concentrations on device performance were investigated.Next,NiO,Y2O3 and Ga2O3 films were introduced to Eu2O3:Tb3+ device and the corresponding double layer EL devices were fabricated,respectively.The dependences of the film thickness of added layer on luminescence properties were studied.Meanwhile,the luminescence principle and conduction mechanism of the devices were performed in-depth analysis.Then the impacts of annealing atmosphere,annealing temperature and annealing time on the performance of Ga2O3/Eu2O3:Tb3+/N+-Si devices were also studied.It is worth noting that the device annealed for 1min could obtain intense red emission when 3 V was applied.The relationship between Ga2O3/Eu2O3:Tb3+/N+-Si device performance with luminescent layer thickness and Tb3+ ion doping concentration was finaly analyzed,and red/green color-tunable EL devices were achieved.