Papers by Author: Soo Jin Chua

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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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Authors: Lip Fah Chong, Jing Hua Teng, Ee Leong Lim, Norman Soo Seng Ang, J.R. Dong, Soo Jin Chua
Abstract: In this paper, we present the theoretical investigation of index-coupled distributed feedback (DFB) laser with tilted single mode ridge waveguides. By tilting part of the ridge waveguide in various degrees, DFB laser with manifold effective grating periods can be realized. The structure is analyzed using couple mode theory in matrix form based on threshold analysis. Important parameters of DFB laser like resonant frequency and threshold gains are obtained by solving the eigen-equation. The results indicate not only that the lasing frequency is modulated by the waveguide titling angle, but also large Gain Margin (GM) can be achieved at the threshold condition which enhance the stable single mode operation in index-coupled DFB laser.
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Authors: Jing Hua Teng, Lip Fah Chong, J.R. Dong, Soo Jin Chua, Norman Soo Seng Ang, Yan Jun Wang, Ee Leong Lim
Abstract: In this paper, we report a DFB laser diode with a buried SiO2 grating. Epitaxy lateral overgrowth by metalorganic chemical vapour deposition (MOCVD) is conducted to grow the p-type InP cladding layers in the nano-patterned dielectric grating template. The large refractive index difference between SiO2 and InP results an index coupling coefficient κ of about 250 cm-1. The fabricated DFB laser showed a side mode suppression ratio larger than 45 dB measured. The technology developed can also be used for other applications that require high efficiency grating structure.
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Authors: Hong Quang Le, Soo Jin Chua
Abstract: Single ZnO nanorods with diameters of 100nm were directly grown on GaN surface by using low-temperature hydrothermal synthesis. Individual nanorods were removed from the substrate and placed between the Au contact pads and the current voltage measurement was proceeded to characterize the electrical properties of the ZnO nanorods. By using thermionic field emission model of Padovani and Stratton , the resistivity, carrier concentration, electron mobility can be extracted with the values of 0.14 Ωcm, 9.2x1016/cm3,33.82cm2V-1s-1, respectively. The single ZnO nanorods also showed high sensitivity to the UV light (325nm). Under the UV illumination, the UV induced current increase nearly 10 times than the dark current. In addition, the nanorods also exhibited a slow UV response due to the effects of the oxygen ions on the surface of the nanorods.
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Authors: X.H. Zhang, Soo Jin Chua, A.M. Yong, S.Y. Chow, H.Y. Yang, S.P. Lau, S.F. Yu, X.W. Sun
Abstract: Using a simple process of the deposition of ZnO thin films on SiOx/Si substrates and subsequent thermal annealing, we fabricated ZnO quantum dots embedded in silicon oxide matrix. The ZnO quantum dots were characterized using transmission electron microscopy and timeintegrated photoluminescence. The photoluminescence of the quantum dots show a blue-shift of 47 meV due to the quantum confinement effect.
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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.
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Authors: Zhe Chuan Feng, Soo Jin Chua, Z.X. Shen, Kiyoshi Tone, Jian Hui Zhao
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Authors: Deny Sentosa, Xiao Hong Tang, Soo Jin Chua, Zong You Yin
Abstract: Photoluminescence (PL) measurement shows an additional peak with stronger and broader emission at lower photon energy besides the energy band gap transition emission from GaNAs epilayer grown by MOCVD. This emission is assigned as nitrogen-nitrogen interstitial defect related emission. Effect of V/III ratio during the MOCVD growth on this defect related emission peak has been investigated. The combination of optimum V/III ratio during the MOCVD growth and post-growth rapid thermal anneal (RTA) can eliminate this defect emission peak and at the same time the GaNAs’ band gap emission has been greatly improved. The PL spectra contain a single, narrow, and high intensity GaNAs’ band gap transition emission after the RTA annealing. The optimum V/III ratio for growing the GaNAs films with N content < 3.5% is around 20.
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Authors: Ee Leong Lim, Jing Hua Teng, Soo Jin Chua, J.R. Dong, Norman Soo Seng Ang, Lip Fah Chong
Abstract: One challenge for the realization of electrically drive nano-photonic devices is the formation of metal contacts and passivation. In this paper, we report a novel self-aligned method suitable for the formation of the metal contact and passivation for submicron photonic devices. Two different dielectric materials with high selectivity in wet chemical etching and a wet etching of semiconductor to create an undercut are involved. The whole process is completely compatible with existing compound semiconductor process. As a demonstration of this method, the fabrication and characterization of an InGaAsP/InP submicron-ridge waveguide lasers is presented. The method is extendable to high aspect ratio-submicron ridge waveguide and other device fabrication.
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Authors: Yi Hua Wang, Jian Yi Lin, Zhe Chuan Feng, Soo Jin Chua, Cheng Hon Huan Alfred
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