Investigation On The Optical And Structural Properties Of GaN:Er And Related Materials

Er-doped GaN is a hot research topic because of its excellent properties in optics,electricity,and magnetics.The 1540 nm infrared luminescence observed in Er doped GaN（GaN: Er）is of great interest for optical fiber communications because of minimum light absorption at this wavelength in silica fiber.The strong green light emission from GaN: Er can also be observed.Consequently,the optical properties of GaN:Er have attracted wide interest.In this thesis,Er,Pr,Tm single doped and co-doped GaN thin films were prepared by ion implantation and their structural and optical properties were investigated.The main results are shown as follows:1.Er-doped GaN films with different Er dose were prepared by ion implantation and annealed at different temperature and atmosphere.The effect mechanism of annealing parameters on cathodoluminescence spectra were investigated,and the optimal annealing parameters were obtained.When the Er ions dose was 1×10¹⁵atom/cm²,the luminescence intensity of Er ions was the strongest.When the Er ions dose was increased to 5×10¹⁵atom/cm²,the luminescence quenching of Er ions was observed.2.The effects of accelerating voltage and temperature on the CL spectra of Er-implanted GaN were investigated.In the near band-edge emission region,the competition mechanism between DAP and D⁰ X was disclosed.A slight blue shift of the DAP emission peak with the increase of accelerating voltage was observed.Temperature dependence of the CL intensity of FX emission reveals a binding energy of ³2 meV in Er implanted GaN.Below 182 K,the ²H_11/2 state of Er³⁺ is not thermally populated and the yellow band luminescence（YL）related to the defects was observed.At higher temperature,the thermal coupling between the two excited state levels of ²H_11/2 and ⁴S_3/2 of Er³⁺ is obvious and the YL is nearly invisible.Even at 373 K,a strong green emission at 538 nm can be observed,which indicates the Er-doped GaN is promising to be applied in high-temperatrure environment.3.The GaN films were implanted separately with Er,Pr,Tm ions.We applied the cathodoluminescence（CL）spectroscopy to investigate the luminescent properties of GaN thin films implanted with different rare earth ions.Light emission from GaN thin films doped by RE-ions is colorful: red light emission of GaN: Pr,green light emission of GaN:Er,and blue and infrared light emission of GaN: Tm.We also found that rare earth ions can suppress the defect luminescence and improve the luminescence quality.4.Pr/Tm,Er/Pr,Er/Tm and Tm/Er/Pr co-doped GaN thin films were prepared by ion implantation.After thermal annealing treatment for the lattice recovery and ions activation,temperature-dependent cathodoluminescence（CL）spectroscopy was applied to investigate the luminescent properties.Multi-color emission was obtained and the energy transfer processes between two ions were also discussed for the two kinds of rare earth ions co-implanted GaN thin films.In addition,red,green,and blue emissions were observed in one GaN thin film.5.The structural properties of Tm,Er,Pr-doped GaN were studied.We presented an X-ray diffraction and Raman investigation to probe the evolution of the implantation-induced strain.It was shown that the damage evolution of GaN with different rare earth ions implantation is similar.The concentration of these defect and damage increases with the implantation dose of rare earth ions.In order to reduce the defect density of the ion implantation,post-implantation annealing was carried out.The change of stress,strain and crystal quality of GaN epitaxial films was investigated prior to and after annealing.It was discovered that there is a close relationship between the luminescence intensity and the structural properties.