Semiconductor Photonics: Nano-Structured Materials and Devices

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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.
Authors: V. Hongpinyo, Y.H. Ding, J. Anderson, Hery S. Djie, Boon S. Ooi, R.R. Du, A. Ganjoo, H. Jain
Abstract: We investigate the influence of sputtered silica as annealing cap on the enhancement of intermixing rate of semiconductor quantum nanostructures. After sputtered silica application and subsequent rapid thermal annealing, we observed bandgap shift of over 200 meV with respect to the bandgap of as-grown material from various GaAs-based quantum well (QW) heterostructures such as GaAs/AlGaAs, InAlGaP/GaAs, and GaAs/AlGaAs systems at significantly lower temperature than the conventional dielectric cap process with plasma enhanced chemical vapor deposition (PECVD). The results suggest that the sputtered silica process is a promising intermixing technique for the monolithic integration of multiple active/passive photonic components on GaAs-based material systems.
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.
Authors: Lee Siang Chuah, Hassan Zainuriah, Abu Hassan Haslan
Abstract: This paper presents the structural and optical studies of porous GaN sample compared to the corresponding as grown GaN. The samples were investigated by scanning electron microscopy (SEM), high resolution x-ray diffraction (HRXRD), and photoluminescence (PL). The porous area is very uniform, with pore diameter in the range of 80-110 nm. XRD measurements showed that the (0002) diffraction plane peak width of porous samples was slightly broader than the as-grown sample. PL measurements revealed that the near band edge peak of the porous samples were redshifted. Metal-semiconductor-metal (MSM) photodiode was fabricated on the samples. For as grown GaN sample, this detector shows a sharp cut-off wavelength at 362 nm. A maximum responsivity of 0.258 A/W was achieved at 360 nm. For the porous GaN sample, this detector shows a sharp cut-off wavelength at 364 nm. A maximum responsivity of 0.771 A/W was achieved at 363 nm.
Authors: V. Suresh Kumar, J. Kumar
Abstract: We report on the growth mechanism, structural and optical characterstics of Gallium nitride nanowires prepared on sapphire substrates (0001) by reacting metal gallium with Gallium nitride powder and ammonia in the temperature range of 800 to 1050°C. GaN nanowires samples were characterized by using X-ray diffraction technique which shows wurtzite structure of GaN nanowires and the lattice parameters are calculated. Scanning electron microscopy images reveals that the dimension of the nanowires are around 60 – 80 nm and the length of 1 - 2 millimeters. Three Raman modes of GaN have been observed at frequencies 530, 554 and 564 cm-1. Photoluminescence spectrum reveals the band edge at 3.4 eV and gives yellow luminescence.
Authors: C.M.J. Wijers, O. Voskoboynikov
Abstract: In a hybrid discrete-continuum description the optical response of a capped monolayer of nano-objects has been determined. The monolayer emits a summation of partial plane waves obeying traditional reflection and transmission, enabling solution of the monolayer dipole strength. For thick capping layers the resulting reflection coefficients could be approximated by analytical expressions. These results have been used to investigate the feasibility of experimental detection of the optical response of nano-object monolayers.
Authors: S.K. Mohanta, R.K. Soni, S. Tripathy, Soo Jin Chua
Abstract: The InP nanostructures have been fabricated by low-energy Ar+-ion of dose 1 × 1018 cm-2 and energy 50 keV, at normal incidence. The InP nanodot size varies from 50 to 90 nm. Photoluminescence spectra show blue shifted visible emission band at 1.98 eV, and quenching of the band edge emission from the nanopatterned surface. The blue-shifted emission band arises due to size convoluted band-to-band emission form the surface nanodots while the defects formation in the irradiated surface leads to the quenching of band edge emission. Thermal annealing results in clustering of the patterned surface and enhancement of the band edge emission accompanied with absence of visible band. Our results show that the origin of visible emission is from the surface nanodots and not from the nanocrystallites in the implanted surface region. This is corroborated by the wavelength dependence of photoluminescence measurement by probing different depth of the disordered region.
Authors: Subindu Kumar, Dipankar Biswas, Tapas Das
Abstract: In recent years there have been extensive studies on III-V semiconductor quantum dots (QDs). In this paper we have formulated the absorption spectra of a realistic QD system with dot size distribution described by a Gaussian function. The dots were approximated as cubic boxes having finite potentials at the boundaries. The effects of size non uniformity on the optical absorption spectra of a realistic QD system was analyzed and the results have been compared with ideal dots having infinite potentials at the boundaries.
Authors: Dipankar Biswas, Tapas Das, Sanjib Kabi, Subindu Kumar
Abstract: For successive annealing stages the photoluminescence (PL) peaks of InXGa1-XN/GaN quantum wells (QWs) shift initially towards red which is followed by a blue. This phenomenon contradicts the usual monotonic blueshift. We have found that the phenomena can be explained properly only if we consider recombinations from the higher sub-bands to be present in the PL of the InXGa1-XN/GaN QWs, which is not usual. When a strong piezoelectric field exists across a QW, as encountered in InXGa1-XN/GaN QWs, the probability of optical transitions from higher sub-bands of the QW become more probable. In this paper this theory has been established from experimental results.
Authors: Chao Yang Li, Yong Gang Wang
Abstract: We demonstrated an experiment of femtosecond-laser damage threshold on GaAs wafer, the damage threshold was measured from 50 to 400fs. The mechanism was discussed through injection power, pulse duration and ablation profile. The results showed that the damage threshold increased with the pulse duration, the relationship between diameter of ablation hole and laser power density was also analyzed. It was concluded that the main factor affecting the damage threshold was photon ionization and collision ionization.

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