Study On The Influence Of Copper Doping On The Properties Of β-Ga₂O₃ Thin Film Material

As one of the representatives of ultra-wide band gap semiconductor materials,β-Ga₂O₃is widely used in light emitting devices,transparent conductive films,high-power devices,solar-blind ultraviolet detectors and other fields because of its good thermal stability,high breakdown field,excellent physicochemical and photoelectric properties.Doping can regulate the internal crystal structure and physical properties ofβ-Ga₂O₃.N-type doping technology has been relatively mature,but P-type doping has not been broken through.In this paper,based on the magnetron sputtering,Cu-doped Ga₂O₃thin films（"Ga₂O₃/Cu/Ga₂O₃/Cu/Ga₂O₃"）with different sputtering time of Cu(t_m-Cu)were prepared on sapphire（Al₂O₃）substrate.The effects of Cu doping on crystallization,surface morphology,optical and electrical properties ofβ-Ga₂O₃thin films under high temperature annealing and laser annealing were investigated.The main research contents and conclusions of this paper are as follows:1.β-Ga₂O₃thin films were prepared on Al₂O₃substrate.β-Ga₂O₃thin films with different thickness were prepared on Al₂O₃substrate by RF magnetron sputtering.XRD,AFM and other characterization results show that the thickness ofβ-Ga₂O₃films obtained by RF magnetron sputtering for 30 min is about 466 nm,which is favorable for the Cu doping experiments.2.Preparation and characterization of"Ga₂O₃/Cu/Ga₂O₃/Cu/Ga₂O₃"composite structures.Ga₂O₃films and Cu films were prepared by RF and DC magnetron sputtering alternately,and then the composite structures were annealed at high temperature and laser respectively.XRD,AFM and other characterization results show that Cu doping can disturb the lattice arrangement of the originalβ-Ga₂O₃thin films and affect the crystal quality of the films.With the increase of t_m-Cu,the surface ofβ-Ga₂O₃thin films becomes rougher,more Ga ions in the films are replaced by Cu ions,the optical absorption peak intensity basically increases with the increase of t_m-Cu,and the change trend of band gap decreases with the increase of t_m-Cu.Laser annealing can make the internal grains ofβ-Ga₂O₃thin films obtain more energy and move to the appropriate site,so as to improve the absorption characteristics of the films.3.Effect of Cu doping on the electrical properties ofβ-Ga₂O₃thin films.When there is no ohmic contact on the surface of Cu-dopedβ-Ga₂O₃thin films,the resistivity and Hall mobility of different t_m-Cuthin films fluctuate in a wide range,and the carrier concentration has no obvious regularity,so the conclusion is not of reference significance.After Ti and Ti/Au electrodes were fabricated on the surface of the thin film samples,the effective values ofβ-Ga₂O₃thin films with different Cu doping were easier to be measured.With the increase of t_m-Cu,the average resistivity ofβ-Ga₂O₃thin films decreases first and then increases.The lowest resistivity of the sample prepared with Ti/Au electrode is 5.65Ω·cm,which is 5～10 times lower than that of the sample prepared with Ti electrode only,indicating that the ohmic contact effect formed by Ti/Au electrode is good,and the electrical properties of Cu-dopedβ-Ga₂O₃are better.