Near infrared electroluminescence of ZnMgO/InN core-shell nanorod heterostructures grown on Si substrate.

This paper presents a systematic investigation of a ZnMgO/InN core-shell nanorods heterojunction device on a p-Si substrate. Here we demonstrated the heteroepitaxial growth of the well-aligned ZnMgO/InN core-shell nanorods structure, which enabled an increased heterojunction area to improve the carrier injection efficiency of nanodevices by plasma-assisted molecular beam epitaxy combined with metal-organic chemical vapor deposition. In situ X-ray photoelectron spectroscopy measurements were performed on the ZnMgO nanorods, the interface of ZnMgO/InN and the InN core-shell nanorods to fully understand the structure and working mechanism of the heterojunction device. The current transport mechanism has been discussed in terms of the characteristics of current-voltage and the energy band diagram of the n-InN/ZnMgO/p-Si heterojunction. At a low forward voltage, the current transport followed the dependence of I ∼ V(1.47), which was attributed to the deep-level assisted tunneling. When the forward voltage was larger than 10 V, the current followed the relation of I ∼ V(2) because of the radiative recombination process. In accordance with the above conclusion, the near-infrared electroluminescence of the diode could be observed after the forward bias voltage up to 11.6 V at room temperature. In addition, the size quantization effect and the intrinsic electron accumulation of the InN core-shell nanorods were investigated to explain the blueshift and broadened bandwidth. Furthermore, the light output power of about 0.6 microwatt at a fixed wavelength of 1500 nm indicated that our study will further provide a useful route for realizing the near-infrared electroluminescence of InN on Si substrate.

[Photolumimescence character of novel phthalocyanine].

In the present paper, the authors study the photolumimescence spectra of the novel 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine casting film and vacuum-deposited film. Photolumimescence spectras of casting film on the quartz substrate were measured at 10, 77, 177 and 300 K, and the photolumimescence spectra of vacuum-deposited film with a thickness of about 200 nm on the silicon substrate was studied at room temperature (300 K). For 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine, the casting films all show fluorescence peaks at 942, 937, 942 and 942 nm and phosphorescence peaks at 1114, 1057, 1114 and 1114 nm in the photolumimescence spectra at 10, 77, 177 and 300 K, respectively. In the cases of 2,3-tetra-(2-isopropyl-5-methyl -benzoyl) hydrogen phthalocyanine, the peaks of excimers, which are related with the resistance ability of molecular aggregation, were found around 1673 nm as observed from photolumimescence spectra of the novel phthalocyanine casting films at 177 and 300 K. And the peak of excimers at 300 K is stronger than at 177 K also as can be seen from photolumimescence spectra of its casting films. With the increase in the temperature, the fluorescence peak was weakened and the peaks of excimers became stronger from the photoluminescence spectra of 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine casting films at 10, 77, 177 and 300 K. At the same time, the authors discussed the reason for coming into being 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine excimers as can be concluded from the structure of 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine molecules through the parameters of Chem 3D Ultra 9.0 MM2 calculation and simulated diagram of C4h isomer of 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine. The peaks of casting film and vacuum-deposited film of 2,3-tetra-(2-isopropyl-5-methyl -benzoyl) hydrogen phthalocyanine presented different maximum emission wavelength and full width at half maximum. The peak of 2,3-tetra-(2-isopropyl-5-methyl-benzoyl) hydrogen phthalocyanine vacuum-deposited films displays the maximum emission wavelengths around 1140 nm, while the maximum emission wavelengths of casting films show obvious differences compared with the vacuum-deposited films. The usual full width at half maximum is approximately 300 nm for casting film, which is in contrasts with that the full width at half maximum is about 100 nm for the vacuum-deposited film as can be seen from photolumimescence spectra of 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine casting film and photolumimescence spectra of 2,3-tetra-(2-isopropyl-5-methylbenzoyl) hydrogen phthalocyanine vacuum-deposited film.