Research On Photoelectric Properties Of ITO Thin Films In GaN-based LED

At present,ITO film is more and more widely used,and it has an irreplaceable position in high-tech fields such as displays and solar cells.In addition,China is a large country in the storage and production of indium resources,but the products produced on this basis are single.Less value-added.However,developed countries such as Europe and the United States have mastered the relevant technologies and patents of photoelectric thin film materials such as indium oxide.How to further enhance the competitiveness of China’s indium oxide field that is very important to further research on ITO.It has very important theoretical and practical significance,which not only can better enrich the theoretical research level of ITO film preparation and rapid annealing treatment in China,but also provide theoretical support for further solving the development of ITO film DC magnetron sputtering preparation and heat treatment.The research on ITO film mainly focuses on the coating process,doping process and microstructure,semiconductor photoelectric performance and mechanism.It is well known that due to the low degree of undercooling in the coating process,an amorphous structure is easily obtained by using many film preparation techniques including magnetron sputtering.If the film is not post-treated,the performance of the film is far from the needs of practical applications,so proper post-treatment of the prepared film becomes the key to improve the film properties.Previous studies and preliminary work of this thesis prove that heat treatment is an effective means to improve the photoelectric properties of ITO films.Many scholars at home and abroad have studied the effects of heat treatment on the crystal structure and photoelectric properties of ITO films,and have obtained many useful research results,but at present,there are few theoretical studies on the structure and photoelectric properties of thin films by annealing.Therefore,this thesis focuses on the effects of annealing and annealing temperature,annealing time on the structure and photoelectric properties of ITO films,and discusses the effects of substrate temperature and 02 flow control on the structure and photoelectric properties of ITO films under different atmospheres.The application in optoelectronic devices provides experimental basis and theoretical basis.Through research,the main conclusions are as follows:When the thickness is thinner,the film is polycrystalline,the crystallinity is high,and the grain size is larger,but the surface of the film is deteriorated,the surface is rough,and the defects are many.As the film thickness increases,the surface forms gradually a continuous structure and its density is also improved greatly,the growth is more uniform,the defects are reduced,and the crystal grains are increased significantly.As the film thickness increases,the resistivity of the film decreases accordingly.The larger the thickness of the ITO transparent film,the smaller the forward voltage and meanwhile the lower the luminous power.The increase of the thickness of the ITO film leads to a great influence on the light absorption,the thickness increases and the luminous power decreases significantly.When the thickness of ITO is 300 A,the ITO film has good ohmic contact with P-GaN,the crystallization degree is good,the current expansion is optimal,the brightness is the highest,, which is the preferable condition in the LED chip production process.After annealing by RTA,the ITO resistance is significantly reduced and the transmittance is rapidly increased.Annealing treatment can improve the crystal quality of the ITO film layer and the ohmic contact between ITO and P-GaN,which improve the transmittance and reduce the contact voltage.It is verified by different annealing temperatures,different annealing oxygen flow rates and different annealing time,forward voltage and luminous power just have little change within the annealing temperature range of 560℃-600℃;when the annealing temperature is between 580℃,the brightness is the maximum;when the oxygen flow rate varies from 0-5 sccm,the electrical conductivity of the film shows an increasing trend,indicating that the increase of oxygen flow has a promoting effect on the electrical conductivity of the film.The experiment verified that the brightness is the maximum when the oxygen flow rate is 3sccm.Under the heat treatment condition,the resistivity of the ITO transparent conductive film increases with the prolongation of the heat treatment time.When the annealing time is 250s,the brightness is the maximum,which can be used as an optimized condition for LED production.