Non-Polar Wurtzite (1120) GaN/AlN Quantum Dots for Highly Efficient Opto-Electronic Devices

In III-nitride quantum dots (QDs), optical transition rate is very low because of the large built-in electrostatic field caused by the spontaneous polarization (SP) and piezoelectric (PZ) effects. In this work, we study the screening potential which is a solution of the self-consistent Hartree equation taking into account the built-in electrostatic field and its effect on light emission characteristics of non-polar wurtzite (WZ) (112¯0) GaN/AlN QD. It is found that the light emission intensity of the non-polar (112¯0) GaN/AlN QD structure is expected to be about four times larger than that of the c-plane (0001) GaN/AlN QD structure because the y-polarized matrix elements in the non-polar QD are larger than that in the c-plane QD. These predictions indicate that non-polar GaN/AlN QD structure have strong potential for highly efficient opto-electronic devices.

Controllable photoinduced scattering and optimized light emission intensity in Nd3+ doped (Pb,La)(Zr,Ti)O3 perovskite ceramics

Controllable photoinduced scatterers were investigated in Nd3+-doped lead lanthanum zirconate titanate (PLZT) perovskite ceramics, the total number of which will increase dramatically with the induction of light intensity.

Analytical Study of the Thermal Activation of Tb Doped Amorphous SiC:H Thin Films

ABSTRACTThe luminescence of Tb-doped a-SiC:H thin films with different Tb concentrations under sub-bandgap photon excitation was investigated. Two independent processes were identified. The annealing induced activation of the Tb3+ and the inhibition of host-mediated non-radiative recombination paths. The integrated emission intensity is described by a rate equation model, considering these two. In this study, the luminescence enhancement with increasing annealing temperature is shown. The optimal Tb concentration and annealing temperature for the highest Tb-related light emission intensity is determined. Finally, a parameter proportional to the number of optically active ions is found through the aforementioned model.

GaP Homojunction LEDs Fabricated by Dressed-Photon-Phonon-Assisted Annealing

By using a homojunction-structured GaP single crystal, we generated a photon energy higher than the bandgap energy (2.26 eV). The device was fabricated by performing dressed-photon-phonon- (DPP-) assisted annealing, while applying a forward-bias current, on a p-n homojunction structure formed by implanting a dopant (Zn) into an n-type GaP substrate. The DPP-assisted annealing increased the light emission intensity in an energy band above 2.32 eV by at least 550% compared with that before annealing.

The Luminescence Properties and Energy Transfer from Ce3+to Pr3+for YAG:Ce3+Pr3+Phosphors

Y2.94−xAl5O12(YAG):Ce0.06Prxphosphors with various Pr3+concentrations (x=0, 0.006, 0.01, 0.03, 0.06, and 0.09) were synthesized by using a coprecipitation method. The phases, luminescent properties, and energy transfer phenomenon from Ce3+to Pr3+were investigated. The results indicated that the doping of Pr3+ (x≤0.09)did not produce any new phases but caused a slight lattice parameters increase. After Pr3+doping, the YAG:CePr phosphor emits red light at 610 nm, which was regarded helpful for improving the colour rendering index of the phosphor. With Pr3+concentration increase from 0.006 to 0.01 mol, the intensity of red light emission increased slightly; further increasing Pr3+concentration from 0.01 to 0.09, the red light emission intensity decreased gradually. Excitation at 340, and 460 nm could not lead to the direct electronic excitation of Pr3+ions; however, when YAG:CePr was excited at 340 nm a red light emission at 610 nm appeared, which implied the energy transfer phenomenon from Ce3+to Pr3+.

Strong enhancement of 420∼425nm optical wavelength of blue LED by using CaF2 scintillating crystals as a cap

ABSTRACTIt has been found that the blue light emission of LED is remarkably enhanced by using optical window of CaF2 disk doped with Eu2O3. The CaF2 crystals doped with Eu2O3 strongly absorb UV light with 330~420nm optical wavelength as a cutting filter. Instead, CaF2 crystals emit 420~425nm wavelength visible light. As a result, the UV light shifts to a light of around 420nm wavelength, and the LED light emission intensity markedly increases. In our experiments, the UV components were absorbed, while, around 420nm emitting light has been strengthened by more than 30%. The FWHM value is improved by around 30%.