Atomic hydrogen induced step bunching and fabrication of quantum wire arrays on GaAs (311)A substrate by molecular beam epitaxy

Atomic hydrogen assisted molecular beam epitaxy (MBE) is a novel type of epitaxial growth of nanostructures. The GaAs (311)A surface naturally forms one-dimensional step arrays by step bunching along the direction of (-233) and the space period is around 40nm. The step arrays extend over several mum without displacement. The InGaAs quantum wire arrays are grown on the step arrays as the basis. Our results may prompt further development of more uniform quantum wire and quantum dot arrays.

Fabrication of novel double-hetero-epitaxial SOT structure Si/gamma-Al2O3/Si

In this paper, we report the fabrication of Si-based double-hetero-epitaxial silicon on insulator (SOI) structure Si/gamma-Al2O3/Si. Firstly, single crystalline gamma-Al2O3(100) insulator films were grown epitaxially on Si(100) using the sources of TMA (Al(CH3)(3)) and O-2 by very low-pressure chemical vapor deposition. Afterwards, Si(100) epitaxial films were grown on gamma-Al2O3 (100)/Si(100) epi-substrates using a chemical vapor deposition method similar to the silicon on sapphire epitaxial growth. The Si/gamma-Al2O3/Si SOL materials are characterized in detail by reflect high-energy electron diffraction, X-ray diffraction and Auger energy spectrum (AES) techniques. The insulator layer of gamma-Al2O3 has an excellent dielectric property. The leakage current is less than 1 x 10(-10) A/cm(2) when the electric field is below 1.3 MV/ cm. The Si film grown on gamma-Al2O3/Si epi-substrates was single crystalline. Meanwhile, the AES depth profile of the SOL structure shows that the composition of gamma-Al2O3 film is uniform, and the carbon contamination is not observed. Additionally, the gamma-Al2O3/Si epi-substrates are suitable candidates as a platform for a variety of active layers such as GaN, SiC and GeSi. It shows a bright future for microelectronic and optical electronics applications. (C) 2002 Elsevier Science B.V. All rights reserved.

Simulation and fabrication of thermo-optic variable optical attenuators based on multimode interference coupler

A type of thermo-optic variable optical attenuator based on multimode interference coupler is proposed. The optical field propagation properties of the devices are simulated using finite difference beam propagation method. The propagation loss of the fabricated device is 2-4.2 dB at the wavelength range 1510-1610 nm. The total power consumption is 370 mW and the maximum attenuation is more than 25 dB, which almost can meet the requirements of optical fiber communication systems.

Abatement of waste gases and water during the processes of semiconductor fabrication

The purpose of this article is to examine the methods and equipment for abating waste gases and water produced during the manufacture of semiconductor materials and devices. Three separating methods and equipment are used to control three different groups of electronic wastes. The first group includes arsine and phosphine emitted during the processes of semiconductor materials manufacture. The abatement procedure for this group of pollutants consists of adding iodates, cupric and manganese salts to a multiple shower tower (MST) structure. The second group includes pollutants containing arsenic, phosphorus, HF, HCl, NO2, and SO3 emitted during the manufacture of semiconductor materials and devices. The abatement procedure involves mixing oxidants and bases in an oval column with a separator in the middle. The third group consists of the ions of As, P and heavy metals contained in the waste water. The abatement procedure includes adding CaCO3 and ferric salts in a flocculation-sedimentation compact device equipment. Test results showed that all waste gases and water after the abatement procedures presented in this article passed the discharge standards set by the State Environmental Protection Administration of China.

Fabrication of 4 x 4 tapered MMI coupler with large cross section

MMI coupler with large cross section has low coupling loss between the device and fiber. However, large chip area is required. Recently proposed N x N tapered MMI coupler shows a substantial reduction in device geometry. No such kind of devices with N > 2 has yet been realized up to now. The authors have demonstrated a 4 x 4 parabolically tapered MMI coupler with large cross section that can match the SM fiber in silicon-on-insulator (SOI) technology. The device exhibits a minimum uniformity of 0.36 dB and excess loss of 3.7 dB, It represents a key component for realization of MMI-based silicon integrated optical circuit technology.

Fabrication of 2 x 2 tapered multimode interference coupler

The authors demonstrate a 3dB 2 x 2 parabolically tapered multimode interference (MMT) coupler with a large cross-section and space between the different ports using silicon-on-insulator technology. The device exhibits a uniformity of < 0.8dB and can be used in the realisation of an MMI-based optical switch with a high extinction ratio.

Fabrication and characterization of metal-semiconductor-metal (MSM) ultraviolet photodetectors on undoped GaN/sapphire grown by MBE

Interdigital metal-semiconductor-metal (MSM) ultraviolet photoconductive detectors have been fabricated on undoped GaN films grown by molecular beam epitaxy (MBE), Response dependence on wavelength, applied current, excitation powers and chopper frequency has been extensively investigated. It is shown that the photodetector's spectral response remained nearly constant for wavelengths above the band gap and dropped sharply by almost three orders of magnitude for wavelengths longer than the band gap. It increases linearly with the applied constant current, but very nonlinearly with illuminating power. The photodetectors showed high photoconductor gains resulting from trapping of minority carriers (holes) at acceptor impurities or defects. The results demonstrated the high quality of the GaN crystal used to fabricate these devices. (C) 2000 Elsevier Science B.V. All rights reserved.

The fabrication of thick SiO2 layer by anodization

Silicon-based silica waveguide (SiO2/Si) devices have huge applications in optical telecommunication. SiO2 up to 25-mu m thick is necessary for some passive SiO2/Si waveguide devices. Oxidizing porous silicon to obtain thick SiO2 as cladding layer is presented. The experimental results of porous layer and oxidized porous layer formation were given. The relationship between cracking of SiO2 and temperature varying rate was given experimentally. Such conclusions are drawn: oxidation rate of porous silicon is several orders faster than that of bulk silicon; appropriate temperature variation rate during oxidation can prevent SiO2 on silicon substrates from cracking, and 25 mu m thick silicon dioxide layer has been obtained. (C) 2000 Elsevier Science B.V. All rights reserved.

Fabrication of InGaAs quantum dots with an underlying InGaAlAs layer on GaAs(100) and high index substrates by molecular beam epitaxy

In this paper, InGaAs quantum dots with an adjusting InGaAlAs layer underneath are grown on (n 1 1)A/B (n = 2-5) and the reference (1 0 0) substrates by molecular beam epitaxy. Small and dense InGaAs quantum dots are formed on (1 0 0) and (n 1 1)B substrates. A comparative study by atomic force microscopy shows that the alignment and uniformity for InGaAs quantum dots are greatly improved on(5 1 1)B but deteriorated on (3 1 1)B surface, demonstrating the great influence of the buried InGaAlAs layer. There is an increase in photoluminescence intensity and a decrease in the full-width at half-maximum when n varies from 2 to 5. Quantum dots formed on (3 1 1)A and (5 1 1)A surfaces are large and random in distribution, and no emission from these dots can be detected. (C) 1999 Elsevier Science B.V. All rights reserved.

Fabrication of luminescent Ge nanocrystals started from unlayered hydrogenated amorphous SiGe films or hydrogenated amorphous Si hydrogenated amorphous Ge multilayers

Nanocrystalline Ge embedded in SiOx matrix is fabricated by oxidizing hydrogenated amorphous Sice alloys or hydrogenated amorphous Si/hydrogenated amorphous Ge multilayers. The structures before and after oxidation are systematically investigated. Visible light emission was observed from both samples. The luminescence peak is located at 2.2 eV which is independent of the starting materials. Compared to the luminescence from unlayered samples, the photoluminescence spectrum from multilayered samples has a narrower band width, which can be attributed to the uniform size distribution. The light emission origin is also discussed briefly and a mechanism different from the quantum size effect is suggested.

Stability improvement of selective oxidation during the fabrication of InGaAs/GaAs vertical cavity surface emitting laser

The effects of the carrier gas flow and water temperature on the oxidation rate for different reaction temperatures were investigated. The optimum conditions for stable oxidation were obtained. Two mechanisms of the oxidation process are revealed. One is the flow-controlling process, which is unstable. The other is the temperature-controlling process, which is stable. The stable region decreases for higher reaction temperatures. The simulation results for the stable oxidation region are also given. With optimum oxidation conditions, the stability and precision of the oxidation can be dramatically improved.

Fabrication of GaN epitaxial films on Al2O3/Si (001) substrates

Single crystal GaN films of hexagonal modification have been fabricated on Al2O3/Si (001) substrates via a low pressure metalorganic chemical deposition (LP-MOCVD) method. The full width at half-maximum of (0002) X-ray diffraction peak for the GaN film 1.1 mu m thick was 72 arcmin. and the mosaic structure of the film was the main cause of broadening to the X-ray diffraction peak. Al room temperature, the photoluminescence (PL) spectrum of GaN exhibited near band edge emission peaking at 365 nm.

Fabrication of Nano-structured VOx Film by Low Temperature Ion Beam Sputtering and Reductive Annealing

VOx thin films have been fabricated by low temperature ion beam sputtering and post reductive annealing process. Semiconductor-metal phase transition is observed for the film annealed at 400 degrees C for 2 hours. The film also shows a polycrystal structure with grain size from 50nm to 150nm. The VOx thin films fabricated by this process have a TCR up to -2.7% at room temperature. Our results indicate a promising fabrication method of the nano-structured VOx film with relatively high TCR and semiconductor-metal phase transition.

Fabrication and characterization of TO packaged high-speed laser modules - art. no. 682407

Various high-speed laser modules are fabricated by TO-Packaged processes, such as FP laser modules, DFB laser modules, and VCSEL modules. Furthermore,, the resonance among the circuit elements provides an approach to compensating the TO packaging parasitics, and improving the frequency response of the devices. The detailed equivalent circuit model is established to investigate both the laser diode and packaging comprehensively. The small-signal modulation bandwidths of the TO packaged FP laser, DFB laser and the VCSEL modules are more than 10, 9.7 and 8 GHz, respectively.

Fabrication and Investigation of High Efficiency Evanescently Coupled Uni-Traveling Carrier Photodiodes

In this paper, an evanescently coupled uni-traveling carrier photodiodes (EC-UTC-PDs) have been fabricated and investigated, which can benefit from the incorporation of a multimode diluted waveguide of appropriate length with experiment-simulation comparison. A high responsibvity of 0.68 A/W at 1.55-mu m without an anti-reflection coating, -1 dB compression current of more than 19 mA, and a large -1 dB vertical alignment tolerance of 2.2 mu m were achieved.