Shen Rensheng

A Study of GaN Grown on SiH4 Pre-Treated 6H-SiC Substrates

GaN thin films are grown on Si-terminated (0001) 6H-SiC substrates pre-treated with SiH4 in a metal organic chemical vapor deposition system. The influence of the SiH4 pre-treatment conditions on the SiC surface is carefully investigated. It is found that SiH4 could react with the SiC surface oxide, which will change the surface termination. Moreover, our experiments demonstrate that SiH4 pre-treatment can distinctly influence the AlGaN nucleation layer and the basic characteristics of GaN.

Photoluminescence and X-Ray Photoelectron Spectroscopy of p-Type Phosphorus-Doped ZnO Films Prepared by MOCVD

Reproducible p-type phosphorus-doped ZnO (p-ZnO:P) films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02 × 10 17 cm−3, a mobility of 1.05 cm2/Vs, and a resistivity of 6.6 Ω · cm. Obvious acceptor-bound-exciton-related emission and P-induced zinc vacancy (VZn) emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125 meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that PZn–2VZn shallow acceptor complex most likely contributes to the p-type conductivity of ZnO:P films.

On the fluorescence enhancement mechanism of Er3+ in germanate glass containing silver particles

The spectral properties of trivalent erbium ions (Er3+) are systematically studied in a melt-quenched germanate glass (60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O) containing silver (Ag) particles. Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles. The fluorescence from Er3+ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar+ laser. A comparison is made between a spectral study performed on the unannealed Er3+-doped sample and the one annealed for 20 min. The data of absorption cross section and Judd—Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles, indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er3+ ions. The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.

Enhanced Output Power of Near-Ultraviolet Light-Emitting Diodes by p-GaN Micro-Rods

Near-ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) are grown by low-pressure metal-organic chemical vapor deposition. The scanning electronic microscope image shows that the p-GaN micro-rods are formed above the interface of p-AlGaN/p-GaN due to the rapid growth rate of p-GaN in the vertical direction. The p-GaN micro-rods greatly increase the escape probability of photons inside the LED structure. Electroluminescence intensities of the 372 nm UV LED lamps with p-GaN micro rods are 88% higher than those of the flat surface LED samples.

Photoluminescence and Electroluminescence of the Novel Soluble Zinc Phthalocyanine

α(β)-tetra-(methoxy-phenoxy)-zinc phthalocyanine are synthesized by employing 3(4)- nitrobenzene-1,2-dicarbonitrile as precursors. They are characterized by spectrum methods and elemental analysis. The UV-Vis spectrum, photoluminescence spectra of spin-coated film and solid pellet are compared. The electroluminescent devices are fabricated by using spin coating. The results indicate that the fluorescence of solid phthalocyanine has a red-shift of more than 145 nm compared to that in solution. The fluorescences are broader in solid state than that in solution. The fluorescence of β-substituted phthalcyanines has a more red-shift than α-substituted phthalcyanines. The electroluminescent spectra around 856 and 862 nm are consisted with the photoluminescence spectra of spin-coated film. The shorter inter-molecule space leads to the large red-shift of the fluorescence.