Semiconductor Photonics: Nano-Structured Materials and Devices

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Authors: C.B. Tay, Soo Jin Chua
Abstract: We show that the rod-like morphology of hydrothermally-grown ZnO nanorods can be obtained on any substrate, pre-coated with ZnO nanoparticles, when pH<7.3 or pH>10.1. When pH>10.1, three types of morphology, from uniform nanorods to large clustered rods, can be distinguished based on the solubility of zinc. In line with classical thermodynamics, the density of nanorods increases when the solubility of zinc decreases. We also report that the orange defect peak photoluminescence can be reduced, while the UV peak increased by decreasing the pH of the growth solution.
Authors: Shahrum Abdullah, Z. Endut, I. Ahmad, Azman Jalar, Suhaila M. Yusof
Abstract: Nowadays, die attach film (DAF) gaining popularity in microelectronic packaging as integral part in facilitating the growth of wafer level packaging and stacked die packaging. DAF applied to the backside of wafers prior to saw have many advantages, such as the elimination of the epoxy dispensed process step and the reduction of epoxy related failure mode. However, the dicing process for DAF wafer usually associated with sidewall chipping, DAF whiskering and crack that will affect reliability of Quad Flat Non-Leaded (QFN) stacked die. Blade properties and characteristics are the crucial factor in analyzing the DAF dicing results. In this paper, we evaluate the blade characteristics before and after DAF wafer dicing process for our stacked die packaging. The qualitative measure by means of the Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) analysis were performed in order to understand the lamination and dulling effect on blade surface. The obtained results showed that sawing polymeric material such as wafer laminated with DAF induces lamination of polymeric material onto the blade surface and reduce blade cutting edge. As a result, reduce the quality of DAF dicing process.
Authors: Tetsuya Mizumoto, Yoichi Akano, Kazuhiko Tamura, Masaki Yoshimura
Abstract: A pump-induced refractive index change was measured in a passive GaInAsP waveguide together with its temporal response. Also, the temporal response of distributed feedback (DFB) waveguide transmittance modulated by the pump-induced index change was experimentally investigated for an application to all-optical switching devices.
Authors: V. Dixit, H.F. Liu, N. Xiang
Abstract: Blueshifts of photoluminescence (PL) peak wavelength from GaInNAs/GaAs quantum well (QW) at various annealing temperatures have been studied. Our results indicate that as-grown GaInNAs/GaAs QW sample has N-Ga3In1 phase, which changes to a mixture of N-Ga3In1 and NGa2In2 after annealing. The activation energy characterized for short range order is 2.38 eV, which is smaller than that for the diffusion process (3.196 eV). This indicates that the short range order is the dominant mechanism for PL blueshift at relatively low annealing temperature and for short time annealing.
Authors: S. Anandan, Y. Ikuma, T. Kudoh, Y. Ogita, V. Murugesan
Abstract: In the present study, La-doped TiO2 and ZnO nano particles were synthesized and extensively characterized by various sophisticated techniques such as XRD, nitrogen adsorption, UV-Vis, AFM and XPS. Rough and highly porous surface of La-doped photocatalysts was observed by AFM, which is critical for enhancing the photocatalytic activity. Degradation and mineralization studies of monocrotophos (MCP) revealed that 1 wt% La-doped TiO2/ZnO exhibits high activity compared to that of pure TiO2/ZnO.
Authors: S. Kuntharin, S. Sanorpim, T. Nakamura, R. Katayama, Kentaro Onabe
Abstract: We have investigated effect of the In- and N-rich growth conditions on the structural modification of cubic-phase InN (c-InN) films grown on GaAs (001) substrates by rf-plasmaassisted molecular beam epitaxy (RF-MBE). High resolution x-ray diffraction (HRXRD) and Raman scattering measurements were performed to examine the hexagonal phase generation in the c-InN grown films. It is evident that higher crystal quality c-InN films with higher cubic phase purity (~82%) were achieved under the In-rich growth condition. On the other hand, for the N-rich growth condition, the c-InN films exhibited higher incorporation of hexagonal phase, which is generated in the cubic phase through the incidental stacking faults on the c-InN (111) planes. Our results demonstrate that the In-rich growth condition plays a critical role in the growth of high quality c-InN films with higher cubic phase purity.
Authors: S. Sanorpim, F. Nakajima, R. Katayama, Kentaro Onabe
Abstract: The high quality GaAsN epitaxial films with the typical thickness of 150-200 nm and the N contents up to 5.5% were grown by MOVPE. The maximum N content of 2.75% at the growth temperature of 550 oC was enhanced to 5.1% at 500 oC and 5.5% at 450 oC. The lower growth temperature may efficiently suppress desorption of N atoms from the growing surface. The narrow high-resolution X-ray diffraction peaks and the clear Pendellösung fringes indicate that the GaAsN films with high uniformity and fairly flat interface were obtained. The 6K-photoluminescence (PL) peak energy of the GaAsN films was varied from 1.38 eV to 1.01 eV with increasing N content up to 2.75%, but no near-band-edge emission was observed in the higher-N-content films, indicating the increase of nonradiative recombination centers caused by the N-related lattice imperfections. Besides, after post growth thermal annealing at 650 oC for 2 min, PL spectrum shows that the near-band-edge emission as low as 0.97 eV (1.3 μm) have been achieved with the film of 5.1% N.
Authors: S. Sanorpim, P. Kongjaeng, R. Katayama, Kentaro Onabe
Abstract: The use of an InGaAs buffer layer was applied to the growth of thick InxGa1-xAs1-yNy layers with higher In contents (x > 30%). In order to obtain the lattice-matched InGaAsN layer having the bandgap of 1.0 eV, the In0.2Ga0.8As was chosen. In this work, the In0.3Ga0.7As0.98N0.02 layers were successfully grown on closely lattice-matched In0.2Ga0.8As buffer layers (InGaAsN/InGaAs). Structural quality of such layers is discussed in comparison with those of the In0.3Ga0.7As0.98N0.02 layers grown directly on the GaAs substrate (InGaAsN/GaAs). Based on the results of transmission electron microscopy, the misfit dislocations (MDs), which are located near the InGaAsN/GaAs heteroepitaxial interface, are visible by their strain contrast. On the other hand, no generation of the MDs is evidenced in the InGaAsN layer grown on the In0.2Ga0.8As pseudosubstrate. Our results demonstrate that a reduction of misfit strain though the use of the pseudosubstrate made possible the growth of high In-content InGaAsN layers with higher crystal quality to extend the wavelength of InGaAsN material.
Authors: S. Sanorpim, D. Kaewket, Sukkaneste Tungasmita, R. Katayama, Kentaro Onabe
Abstract: Optical transitions in the In0.050Ga0.950P0.975N0.025/GaP lattice-matched single quantum wells (SQWs) with different well widths (LZ = 1.6 - 6.4 nm) have been investigated by low-temperature photoluminescence (PL) and PL-excitation (PLE). PL spectra showed the strong visible emission from the samples which attracted to a variety of optoelectronic device applications such as light emitting and laser diodes. Comparing to the bulk film, the PL peak position and the fundamental absorption edge of PLE spectra exhibit blue-shift, which is corresponded to the quantum confinement effect by the well. Comparison between the absorption edge of PLE spectra and the finite square well calculation demonstrate that the effective bandgap energy of the InGaPN/GaP system is might be originated mainly from the N-related localized states.
Authors: C.B. Soh, H. Hartono, S.Y. Chow, Soo Jin Chua
Abstract: Nanoporous GaN template has been fabricated by electrochemical etching to give hexagonal pits with nano-scale pores of size 20-50 nm in the underlying grains. Electrochemical etching at The effect of GaN buffer layer grown at various temperatures from 650°C to 1015°C on these as-fabricated nano-pores templates are investigated by transmission electron microscopy. The buffer layer grown at the optimized temperature of 850°C partially fill up the pores and voids with annihilation of threading dislocations, serving as an excellent template for high-quality GaN growth. This phenomenon is, however not observed for the samples grown with other temperature buffer layers. The PL spectrum for the regrowth GaN on nanoporous GaN template also shows an enhancement of PL intensity for GaN peak compared to as-grown GaN template, which is indicative of its higher crystal quality. This makes it as a suitable template for subsequent device fabrication.

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