Semiconductor Photonics: Nano-Structured Materials and Devices

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Authors: Jong Bin Yeo, Hyun Yong Lee
Abstract: In this study, we found out the new fabrication process condition for Photonic crystals(PCs). PCs were fabricated by holographic lithography(HL), instead of commonly used electron beam lithography(EBL). HL process enable periodic large area fabrication of PCs. Also this method can easily control the pitch of periodic patterns. We set up holographic lithography system by laser and some optical components. The source of light used laser of 442 nm wavelength. Photo-resist(PR) used DMI-150 model. The viscosity of PR is diluted with propylene glycol monomethyl ether acetate(PGMEA) which is solvent for DMI-150. This experiment is holographic lithography of rotated double exposure method for PCs pattern. The method use only one beam. Result data is shown by atomic force microscope(AFM), scanning electron microscope(SEM) and 3D contour image. At the this study, we conclude conditions which we need periodic structure for PCs. It is some factor. For example, incident angle, exposure time, rotation angle, etc. And we show incident angle calculation recipe for needed size of periodic patterns. We already manufacture PCs structure design and simulation tool. Nano structure of this paper’s result is applied to designed PCs patterns.
Authors: M.Z.A. Malik, M.T. Zainuddin, A.M. Abdullah, A. Isnin
Abstract: SiO2-TiO2 systems were extensively investigated in sol-gel process to fabricate passive optical planar waveguides, channel waveguides, interference filters and weather resistant optical memory discs. A high quality, crack free optical thick layer and low processing cost are key success factor for optical applications. Two formulated SiO2-TiO2 systems with 1% and 10% TiO2 were deposited on 20mm x 20mm Si-wafer using multi-spin coating process was investigated on refractive index (n), build-up layer until crack appeared on film. The structure analysis of multi spin was investigated using FTIR. The value of refractive index (n) and thickness of thin films (d) were taken every deposited layer using spectroscopic reflectance and surface morphology of crack thick film by FESEM. SiO2-TiO2 thin film appeared peak ~950cm-1 associated with the Si-O stretching vibrations of Si-OH and Si-O-Ti groups by multi spin coating processes. SiO2-TiO2 system with 10% TiO2 in siloxane structure was found capable on building thick layer up to 2.4 μm at 17 time cycles spins and heat treatments at 680 oC. The value of n was reduced with increasing of number of cycles and believes to form nanoporous zones between interfacial layers during hydrolysis and condensation process of each layer by multi spin coating process.
Authors: D.S. Li, W.J. Fan, Y.X. Dang, B.S. Ma, D.H. Zhang, S.F. Yoon
Abstract: We report the design, characterization and fabrication of GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) to achieve intersubband transitions at expected long wavelengths. With eight-band k·p model, we calculated the E2-E1 transition energies of GaAs/Al0.25Ga0.75As QWs with the different well widths. According to the calculation, we designed a QWIP with the estimated detection wavelength around 9 μm. The actual device structure parameters, such as well width and Al composition, were confirmed by the XRD measurements. The absorption peak at 9.46 μm and the peak responsivity at 8.7 μm are obtained, which are very close to the simulation results.
Authors: Jae Chul Song, D.H. Kang, Seon Ho Lee, Eun Su Jang, Dong Wook Kim, Kannappan Santhakumar, Cheul Ro Lee
Abstract: Vertical GaN nano-columns arrays were grown on Au-coated silicon (111) substrate by Au+Ga alloy seeding method and pulsed flow of Gallium and ammonia using metalorganic chemical vapor deposition (MOCVD). A gold thin film was deposited on Si using an ion coating system. The Au coated Si substrate was annealed at 800 oC under hydrogen ambient for 5 min. The pre-deposition of gallium and nitrogen was performed for 60 sec to form Au+Ga and nitrogen solid solution, which acts as the initial nucleation islands. Then Gallium and ammonia were let in pulse method. Scanning electron microscopy (SEM) image reveals a vertical growth and cylindrical in shape GaN nano-column. From the sharp PL peak intensity it is clearly seen that the dislocation density is reduced considerably and the optical quality of the nano-column is improved.
Authors: D.H. Kang, Jae Chul Song, H. Song, Dong Wook Kim, I.H. Lee, Kannappan Santhakumar, Cheul Ro Lee
Abstract: Structural and optical properties of gallium nitride (GaN) epilayers grown on lens shape patterned sapphire substrate (PSS) using metalorganic chemical vapor deposition (MOCVD) for various growth times were evaluated. From Raman spectra, a blue shift and reduction in the FWHM of Raman modes of GaN grown on PSS were observed when compared to GaN grown on unpatterend sapphire substrate (UPSS). From the DCXRD spectra, full width at half maximum (FWHM) value was decreased with increasing growth time. FWHM of the sample grown at 80 min was 473.5 arc sec. This indicates that there is an improvement in crystalline quality of the GaN grown on PSS as the growth time increases. From photoluminescence (PL) spectra, an increase in band edge emission intensity and a decrease in defect related yellow luminescence were observed for GaN on PSS as the growth time increased.
Authors: N.D. Chien, H.V. Chung, P.T. Huy, Do Jin Kim, Maurizio Ferrari
Abstract: Manganese (Mn) and copper (Cu) doping of ZnS nanowires was achieved by thermal evaporation of Mn, Cu doped ZnS nanopowders. Field emission scanning electron microscopy, and X-ray diffraction studies of the obtained ZnS nanowires demonstrate that the nanowires are single crystal structures and have diameters about 30-200 nm and lengths up to 1 millimeter. Room temperature photoluminescence (PL) measurements show a common PL peak around 520 nm for all ZnS nanowires samples, while impurity-related emission band are observed in doped ZnS nanowires. The dependence of the PL intensity on Mn doping concentration has also been investigated. It is shown that for high Mn doping concentration (10%) in the starting ZnS nanopowders, new emission bands (orange-red and red bands) are observed from the ZnS:Mn nanowires products. The origins of these new emission bands are discussed and brought up for further discussion.
Authors: Li Gao, Qing Feng Yan, C.C. Wong, Yet Ming Chiang
Abstract: Convective self-assembly of colloidal spheres provides a simple method for fabricating two and three dimensional colloidal crystals. In this work, we investigated the layer transitions phenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up. The effects of surface charge, colloidal concentration, and surfactant additions were examined. The results show that the chemical environment plays an important role in colloidal self-assembly. In the case of ordered growth, different layer transition phenomena were observed when the colloidal concentration is different.
Authors: Kannappan Santhakumar, D.H. Kang, Jae Chul Song, Dong Wook Kim, J.S. Kim, M.D. Kim, Cheul Ro Lee
Abstract: Vertically aligned GaN nanocolumn arrays were grown by molecular beam epitaxy on Gallium coated silicon substrate. The dense packing of the NCs gives them the appearance of a continuous film in surface view, but cross-sectional analysis shows them to be isolated nanostructures. The GaN nanocolumns have uniform diameters of 85 nm, lengths up to 720 nm and possess a pyramid like tip. Photoluminescence measurements of NCs show excitonic emission with a dominant, narrow peak centered at 363 nm and FWHM of 68 meV. From the Raman spectrum, peaks at 566.9 and 730 cm-1 are assigned to the E2 and A1(LO) GaN phonons modes which clearly indicates that the grown nanocolumns are highly crystalline. The grown nanocolumns are highly oriented and perpendicular to the growth surface.
Authors: N. Pankaow, S. Panyakeow, S. Ratanathammaphan
Abstract: We have demonstrated the fabrication of InGaAs ring-like nanostructures by dropletepitaxy technique using molecular-beam epitaxy. Dependence on the substrate temperature and the amount of indium and gallium of the nanostructural properties was investigated. It was found that increasing substrate temperature resulted in larger InGaAs ring size but with lower density and that increasing In0.5Ga0.5 amount resulted in larger InGaAs ring size but with oscillating density. Photoluminescence results confirmed the high quality of the nanocrystal.
Authors: Shi Zhen Huang, Wei Lin, Wen Zhe Chen
Abstract: By thermal decomposition, WO3 nanosized material was prepared as sensitive material and doped SiO2 nanosized material has been prepared using Sol-Gel process. NO2 gas-sensing elements have been manufactured with prepared material. The element is sensitive to NO2 with fairly good selectivity. Micro-structure of the material was analyzed by SEM, and the sensing mechanism was discussed.

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