Er ions are implanted into the GaN thick films grown by hydride vapor phase epitaxy. The implantation energy is 200 keV and the implantation doses are 1 × 10^13, 1 × 10^14, 1 × 10^15, and 5 × 10^15 atom/cm2, respectively. The effects of the implantation dose and annealing temperature on the GaN band-edge luminescence are investigated. The cathodoluminescence spectra from 82 to 323 K are measured for 1 × 10^15 atom/cm2- implanted GaN annealed at 1100℃. Luminescence peaks at 356, 362, 376, 390, and 414 nm are observed on the 82 K cathodoluminescence spectrum. When the temperature is increased to 150 K, the intensities of the 356 and 414 nm peaks are nearly unchanged and the 362,376, and 390 nm peaks disappear. The intensity ratio of 538 nm （2H11/2 →4 4I15/2） and 559 nm （4A3/2 →4I15/2） is increased with the increase in temperature. We try to shed light on the above interesting phenomena.
We investigate the spectra and scintillation properties of Ce：YAlO3, Ce：Y3Al5O12, and Ce：LaAlO3. For Ce：YAlO3, the excitation spectrum is very similar with the absorption spectrum; for Ce： Y3Al5O12 and Ce：LaAlO3, the excitation spectra are different from the absorption spectra. Further, Ce：YAlO33 has better scintillation performance than Ce： Y3Al5O12; whereas Ce：LaAlO3 has not demonstrated scintillation performance to date. We also provide reasonable explanations for these experimental phenomena from the viewpoint of energy level structure.
Eu-doped GaN was prepared by solid-state reaction with Ga_2O_3,Eu_2O_3 and NH_3 applied as raw materials.The structural and optical properties were investigated.According to XRD results,wurtzite-type GaN powder without Eu_2O_3phase was obtained at 1000℃ and the grain size was about 20 run.Compared to the undoped GaN powder,all the Raman peaks of Eu-doped GaN powder were shifted towards lower phonon frequency about 2-6 cm^(-1),which may be resulted from the strain caused by the Eu^(3+) doping.The cathodo-luminescence(CL) spectra were measured from 80 to 293 K.Ultraviolet luminescence and Eu^(3+) luminescence were both observed when the temperature was below 200 K.When the temperature was increased to 293 K,the ultraviolet luminescence disappeared.However,the intensity of Eu^(3+) luminescence was nearly not influenced by temperature.A donor-acceptor pair(DAP) model based on O_N and Mg_(Ga) was pointed out for explaining the luminescence mechanism.The cathodo-luminescence spectra of nominal 1.0%,2.0%,3.0%and 5.0%(mole fraction) Eu-doped GaN at room temperature were summarized,which suggestes the 2.0%Eu-doped GaN has the highest Eu luminescent intensity.
WANG XiaodanMO YajuanSHI JianpingZENG XionghuiWANG JianfengXU Ke
In this work, Er-doped aluminum nitride(AlN), Pr-doped AlN, and Er, Pr co-doped AlN thin films were prepared by ion implantation. After annealing, the luminescence properties were investigated by cathodoluminescence. Some new and interesting phenomena were observed. The peak at 480 nm was observed only for Er-doped AlN. However, for Er, Pr co-doped AlN, it disappeared. At the same time, a new peak at 494 nm was observed,although it was not observed for Er-doped AlN or Pr-doped AlN before. Therefore, the energy transfer mechanism between Er^3+and Pr^3+in AlN thin films was investigated in detail. Through optimizing the dose ratio of Er^3+with respect to Pr^3+, white light emission with an International Commission on Illumination chromaticity coordinate(0.332, 0.332) was obtained. This work may provide a new strategy for realizing white light emission based on nitride semiconductors.
