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Progress in Compound Semiconductor Materials IV - Electronic and Optoelectronic Applications

作者： Chua, Y.C. Liang, Jie Passmore, B.S. DeCuir, E.A. Manasreh, M.O. Wang, Zhiming Salamo, G.J. Department of Electrical Engineering Microelectronics-Photonics Program University of Arkansas Fayetteville AR 72701 United States Department of Physics University of Arkansas Fayetteville AR 72701 United States

The optical absorption spectra of intersubband transitions in In 0.3Ga0.7As/GaAs multiple quantum dots (MQDs) grown by molecular beam epitaxy were investigated. By varying the number of In 0.3Ga0.7As monolayers deposited, a series of samples with varying dot sizes ranging from 10-50 monolayers were obtained. The quantum dots grown with size less than 15 monolayers or more than 50 monolayers did not yield any observable measurements of intersubband transition. This suggests that there exist a critical upper and lower limit of In0.3Ga 0.7As quantum dots for infrared detectors. A wavelength range of 8.60-13.70 μm is achieved for structures grown with the above monolayers range. The theoretical line-shape of the intersubband transition absorption was compared to the experimental measurements. From the lineshape, it was deduced that bound-to-continuum transition is present in thick quantum dots and bound-to-bound transition is present in thinly grown quantum dots. © 2005 Materials Research Society.

关键词： Semiconducting indium gallium arsenide

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Longitudinal Modes in InAlGaAs/AlGaAs High-Power Laser Diodes

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MRS Online Proceedings Library 2005年第1期829卷 18-23页

作者： B. S. Passmore Y. C. Chua M. O. Manasreh J. W. Tomm Department of Electrical Engineering and Microelectronics and Photonics Program University of Arkansas Fayetteville USA Max-Born-Institute Berlin Berlin Germany

The emission from bias voltage driven In0.06Al0.08Ga0.86As/Al0.3Ga0.7As edge-emitting diode lasers with cavity lengths of 0.6 and 0.9 mm was measured at 290 K using a high resolution Fourier-transform infrared spectrometer. The light-current (L-I) characteristic curves showed that a threshold current of ~ 0.5 and 0.8 A was needed to reach the stimulated emission in laser diodes with cavity lengths of 0.6 and 0.9 mm, respectively. The laser diode longitudinal modes were observed in the stimulated emission spectrum for each of the devices. These spectra enabled us to calculate the refractive index, total loss, and gain of the active region. On the other hand, the cavity length was determined by utilizing the interferogram spectrum, longitudinal modes spacing, and direct measurements of the laser dimensions. A good agreement between the cavity length values obtained from the three methods was achieved.

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Control of sidewall slope in silicon vias using SF6∕O2 plasma etching in a conventional reactive ion etching tool

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 2005年第5期23卷 2226-2231页

作者： R. F. Figueroa S. Spiesshoefer S. L. Burkett L. Schaper Microelectronics–Photonics Program University of Arkansas Fayetteville Arkansas 72701 Department of Electrical Engineering University of Arkansas Fayetteville Arkansas 72701

The etching of anisotropic blind vias in silicon with diameters of 5–10μm and an aspect ratio ∼2–4 with controlled sidewall inclination is reported. The motivation for this work is the creation of a vertical, or three dimensional interconnect. Via formation by reactive ion etch (RIE) processing is the focus of this project. Arrays of vias have been etched in 125 mm diam silicon (100) wafers using a photoresist mask. A parallel plate RIE system with a SF6∕O2 gas mixture is used. The effects of O2∕(SF6+O2) gas flow ratio, electrode bias, and chamber pressure on etch rate and feature profile have been studied. Visualization of the via profiles using scanning electron microscopy is used to identify the key parameters that control the sidewall slope. This slope is important for the subsequent deposition of via lining materials before filling with Cu. Our results indicate that the O2∕(SF6+O2) ratio is a key parameter in determining the sidewall slope, however the electrode bias and chamber pressure are critical in determining the physical and chemical process balance that determine the anisotropy of the etch process.

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Intersubband Transitions in In 0.3 Ga 0.7 As/GaAs Multiple Quantum Dots of Varying Dot-Sizes

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MRS Online Proceedings Library 2005年第1期829卷 96-101页

作者： Y. C. Chua Jie Liang B. S. Passmore E. A. DeCuir M. O. Manasreh Zhiming Wang G. J. Salamo Department of Electrical Engineering and Microelectronics-Photonics Program University of Arkansas Fayetteville USA Department of Physics University of Arkansas Fayetteville USA

The optical absorption spectra of intersubband transitions in In0.3Ga0.7As/GaAs multiple quantum dots (MQDs) grown by molecular beam epitaxy were investigated. By varying the number of In0.3Ga0.7As monolayers deposited, a series of samples with varying dot sizes ranging from 10–50 monolayers were obtained. The quantum dots grown with size less than 15 monolayers or more than 50 monolayers did not yield any observable measurements of intersubband transition. This suggests that there exist a critical upper and lower limit of In0.3Ga0.7As quantum dots for infrared detectors. A wavelength range of 8.60–13.70 μm is achieved for structures grown with the above monolayers range. The theoretical line-shape of the intersubband transition absorption was compared to the experimental measurements. From the lineshape, it was deduced that bound-to-continuum transtition is present in thick quantum dots and bound-to-bound transition is present in thinly grown quantum dots.

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Analysis of nanoscale deformation in GaAs(100): Towards patterned growth of quantum dots

Analysis of nanoscale deformation in GaAs(100): Towards patt...

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2005 materials Research Society Spring Meeting

作者： Taylor, Curtis R. Stach, Eric A. Malshe, Ajay P. Salamo, Gregory Department of Physics Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 United States National Center for Electron Microscopy Materials Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 United States Department of Mechanical Engineering Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 United States Department of Physics University of Arkansas Fayetteville AR 72703 United States School of Materials Engineering Purdue University West Lafayette IN 47907 United States

Nanoindentations were created in the GaAs(100) surface to act as strain centers for the controlled nucleation and patterning of InAs quantum dots. A systematic approach is taken to understand the indent deformation processes that may lead to precision patterning capabilities for a broad range of nanostructures. Indents were generated using loads below 450 μN with a sharp cube corner indenter. Site-specific cross-sectional thinning of nanoindents (down to 100 nm in size) has been achieved using the in-situ 'lift-out' technique. This allowed for observation of subsurface deformation by transmission electron microscopy (TEM). The crystal was observed to deform solely by dislocation activity with no evidence of amorphization, twinning, fracture, or phase transformation. It is shown that the single phase deformation of GaAs can be well characterized and controlled, which should allow for exploitation of the dislocation strain field to bias nucleation of self-assembled quantum dots. © 2005 Materials Research Society.

关键词： Nanostructured materials

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A wafer-level packaging approach for MEMS & related microsystems using selective Laser-Assisted Bonding (LAB)

A wafer-level packaging approach for MEMS & related microsys...

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55th Electronic Components and Technology Conference, ECTC

作者： Mohan, Ashwin O'Neal, Chad B. Malshe, Ajay P. Foster, Ron B. Department of Mechanical Engineering University of Arkansas Fayetteville AR 72701 United States Institute for Micromanufacturing Louisiana Tech University Ruston LA 71272 United States Microelectronics-Photonics Program University of Arkanasas Fayetteville AR 72701 United States

A wafer-level bonding technique for hermetic, near-hermetic & vacuum packaging of MEMS is proposed. Silicon wafers are metallized with an intermediate layer of gold on which a low temperature solder such as Pb37/Sn63 having a thickness of 50-100 μm is deposited. The bonding layer is deposited either by screen printing or eutectic preforms. Two identical wafers are aligned at the intermediate layer and a continuous wave CO2 laser in combination with an X-Y translation stage is employed for selective heating of the silicon wafer to reflow the solder, bonding the wafers. The laser used had a wavelength of 10.6 μm with a spot size of 0.2-1.0 mm. The bonding temperature at the intermediate layer exceeded the reflow temperature of the eutectic Pb-Sn solder due to local laser heating effects, but the global average temperature was much lower (about 100°C). For a vacuum packaging approach the wafers were mounted on a custombuilt wafer-mating fixture housed in a vacuum chamber maintained at a pressure of 10-3 Torr. Optical, x-ray and acoustic microscopy were performed on the bonded wafer and pull tests on the diced packages to assess the quality of the solder bonds. © 2005 IEEE.

关键词： Electronics packaging

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Interfacing micro-/nano-scale biological and abiological materials for bio/abio hybrid systems

Interfacing micro-/nano-scale biological and abiological mat...

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Nanoscale Devices, Materials, and Biological Systems: Fundamental and Applications - Proceedings of the International Symposium

作者： Kim, Jin-Woo Tung, Steve Deaton, Russell Department of Biological and Agricultural Engineering University of Arkansas Fayetteville AR 72701 Department of Computer Science and Computer Engineering University of Arkansas Fayetteville AR 72701 Department of Mechanical Engineering University of Arkansas Fayetteville AR 72701 Cell and Molecular Biology Program University of Arkansas Fayetteville AR 72701 Microelectronics-Photonics Program University of Arkansas Fayetteville AR 72701

The emergence of a micro- and nano-scale bio/abio hybrid technology that makes use of the advantages of both micro-/nano-scale biological and abiological materials is evident, owing to the unique properties of biological micro-/nano-materials, such as DNA, proteins and cells, as well as those of abiological materials, such as carbon nanotubes (CNTs) and nanoparticles. However, the major challenges for making this merger feasible are integration and interfacing of the bio- and abio-materials. We are investigating the realization of the bio/abio hybrid systems to address this issue through developing (a) a micro flagellar motor based self-powered micro-actuator (μFMA), (b) a micro flagellar motor based AC dynamo (μFMD), and (c) a DNA-based CNT wire (DNA/NTW) nanosensor. This paper discusses our efforts to understand and develop the nanoscale interfaces of bio- and abio-components, i.e. flagellum-substrate and DNA-CNT, to achieve the next generation bio/abio hybrid engineered systems.

关键词： Nanostructured materials

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A Wafer-Level Packaging Approach for MEMS and Related Microsystems using Selective Laser-Assisted Bonding (LAB)

A Wafer-Level Packaging Approach for MEMS and Related Micros...

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Electronic Components and Technology Conference (ECTC)

作者： Ashwin Mohan Chad B. O'Neal Ajay P. Malshe Ron B. Foster Department of Mechanical Engineering University of Arkansas Fayetteville AR USA Department of Mechanical Engineering University of Arkansas Fayetteville AR Institute for Micromanufacturing Louisiana Tech University Ruston LA USA Microelectronics-Photonics Program University of Arkanasas Fayetteville AR USA

A wafer-level bonding technique for hermetic, near-hermetic & vacuum packaging of MEMS is proposed. Silicon wafers are metallized with an intermediate layer of gold on which a low temperature solder such as Pb37/Sn63 having a thickness of 50-100 mum is deposited. The bonding layer is deposited either by screen printing or eutectic preforms. Two identical wafers are aligned at the intermediate layer and a continuous wave CO 2 laser in combination with an X-Y translation stage is employed for selective heating of the silicon wafer to reflow the solder, bonding the wafers. The laser used had a wavelength of 10.6 mum with a spot size of 0.2-1.0 mm. The bonding temperature at the intermediate layer exceeded the reflow temperature of the eutectic Pb-Sn solder due to local laser heating effects, but the global average temperature was much lower (about 100degC). For a vacuum packaging approach the wafers were mounted on a custom-built wafer-mating fixture housed in a vacuum chamber maintained at a pressure of 10 -3 Torr. Optical, X-ray and acoustic microscopy were performed on the bonded wafer and pull tests on the diced packages to assess the quality of the solder bonds

关键词： Wafer scale integration Micromechanical devices Wafer bonding Temperature Packaging Silicon Heating Optical microscopy Vacuum technology Metallization

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Application of aligned carbon nanotubes in micro shear stress sensing

Application of aligned carbon nanotubes in micro shear stres...

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2004 ASME International Mechanical Engineering Congress and Exposition, IMECE 2004

作者： Clendenin, Jason Rokadia, Husein Tung, Steve Ogburia, Konye Microelectronics-Photonics Program University of Arkansas Department of Mechanical Engineering University of Arkansas Department of Electrical Engineering Alabama A and M University

This paper reports the development of a MEMS based aligned carbon nanotube, thermal surface shear stress sensor for micro shear stress sensing applications. This paper is focused on the theory of alignment of CNTs during sensing element fabrication as well as experimental and calibration results from sensor testing. It is found that CNTs can be routinely aligned between surface micromachined gold electrodes using AC dielectrophoresis to form shear stress sensing elements. In order to fabricate the sensing element, a 25 V p-p electric field at 3 MHz was used to form a ∼150 μm wide line of aligned CNTs. The measured resistance of the sensing element was 580 Ω. The fabricated CNT shear stress sensor has been tested by bonding a Plexiglas channel to the electrode chip in order to create a 2D internal flow. The CNT shear stress sensor was found to have an average TCR of -0.0112 %/ °C or -0.0691Ω/°C and a current to voltage ratio of 0.07 mA/V. Copyright © 2004 by ASME.

关键词： Carbon nanotubes

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Bacterial flagellar motors as microfluidic actuators

Bacterial flagellar motors as microfluidic actuators

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2004 ASME International Mechanical Engineering Congress and Exposition, IMECE 2004

作者： Pooran, Ryan Al-Fandi, Mohamed Tung, Steve Kotagi, Nalini Kim, Jin-Woo Lee, Ju-Seok Microelectronics - Photonics Program University of Arkansas Department of Mechanical Engineering University of Arkansas Dept. of Biological and Agricultural Engineering University of Arkansas

Microfluidic actuators are extremely important components of microfluidic systems used in biological, chemical and biochemical analyses. We are in the process of developing hybrid microsystem devices that utilize flagellar motors in tethered Escherichia coli (***) cells as actuators. In this study we describe the robustness of the flagellar motor actuators. To examine the robustness of the actuators we observe the behavior of the cells when exposed to a hydrodynamic load. With this method we are able to determine the torque generated by the flagellar motor and the adhesion force of the flagellar filament to the substrate. Using hydrodynamic loading we are also able to synchronize the rotation of multiple cells. Finally, we present data which represents the lifetime of the flagellar motor actuators. Copyright © 2004 by ASME.

关键词： Actuators

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