Michael Geis

Followers

Following

Public Views

Interests

Uploads

Papers by Michael Geis

Modeling and characterization of Mach-Zehnder silicon electro-optical modulators

2008 Conference on Lasers and Electro-Optics, 2008

Silicon electro-optic modulators are essential components for low-cost optoelectronic devices and... more

CMOS-Compatible High Frequency Infrared Photodiodes

2007 Conference on Lasers and Electro-Optics (CLEO), 2007

All-Si, CMOS-compatible, waveguide photodiodes were fabricated with a 10 to 20 GHz bandwidth, res... more

CMOS-compatible dual-output silicon modulator for analog signal processing

Optics Express, 2008

A broadband, Mach-Zehnder-interferometer based silicon optical modulator is demonstrated, with an... more A broadband, Mach-Zehnder-interferometer based silicon optical modulator is demonstrated, with an electrical bandwidth of 26 GHz and V π L of 4 V•cm. The design of this modulator does not require epitaxial overgrowth and is therefore simpler to fabricate than previous devices with similar performance.

format_quoteVoltage of ±4.5 V is necessary for 22% modulation depth in a 0.5 mm device, affected by impedance mismatch.format_quote

Download

An Etch Pit Technique for Analyzing Crystallographic Orientation in Si Films

Journal of The Electrochemical Society, 1982

In this paper we describe a simple technique for analyzing crystallographic orientations in large... more In this paper we describe a simple technique for analyzing crystallographic orientations in large-grain polycrystalline Si films. The technique consists of etching a grid-array of etch pits through the Si using an anisotropic chemical etch. The geometry of an etch pit is indicative of the local orientation. Thus texture (i.e., * Electrochemical Society Student Member.

Download

CMOS-Compatible All-Si High-Speed Waveguide Photodiodes With High Responsivity in Near-Infrared Communication Band

IEEE Photonics Technology Letters, 2007

We report the integration of a hybrid silicon evanescent waveguide photodetector with a hybrid si... more We report the integration of a hybrid silicon evanescent waveguide photodetector with a hybrid silicon evanescent optical amplifier. The device operates at 1550 nm with a responsivity of 5.7 A/W and a receiver sensitivity of-17.5 dBm at 2.5 Gb/s. The transition between the passive silicon waveguide and the hybrid waveguide of the amplifier is tapered to increase coupling efficiency and to minimize reflections.

Download

Effect of back contact impedance on frequency dependence of capacitance-voltage measurements on metal/diamond diodes

Applied Physics Letters, 1993

Differential capacitance-voltage (C-V) measurements were performed on Al and Pt rectifying contac... more Differential capacitance-voltage (C-V) measurements were performed on Al and Pt rectifying contacts fabricated on natural (type IIb) diamonds. The C-V data showed frequency dependence, which decreased significantly after reducing the back contact impedance. The frequency dependence seems primarily to be an effect of the contact capacitance, contact resistance, and bulk resistance of diamond. A model which includes these variables has been proposed to explain this frequency dependence using both large and small back contact impedances.

Ultraviolet photoresponse characteristics of diamond diodes

Applied Optics, 1991

The photoresponse of Schottky and np-diamond diodes has been measured from 120 to 600 nm. The ult... more

Download

Photonic ADC: overcoming the bottleneck of electronic jitter

Optics Express, 2012

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a ... more Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs-a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20channel silicon filter bank has been demonstrated.

Download

Nonreciprocal acoustoelectric interaction of surface waves and fluorine plasma-treated AlGan/GaN 2DEG

2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS)

This paper demonstrates acoustoelectric (AE) effects for surface acoustic waves (SAWs) propagatin... more This paper demonstrates acoustoelectric (AE) effects for surface acoustic waves (SAWs) propagating in an AlGaN/GaN 2DEG, where a fluorine based plasma has been used to tune the carrier concentration. Incorporation of fluorine ions in the AlGaN barrier is shown to reduce sheet carrier density in the 2D layer, which is required to prevent screening of piezoelectric fields. Tuning of the 2DEG channel is also observed with a progressive shift of the threshold voltage for co-fabricated HEMT structures. The monolithic gain devices exhibit nonreciprocal insertion losses under applied DC bias for higher-order Rayleigh modes in GaN on sapphire at 728 MHz and 1.48 GHz. This constitutes a first step in implementing the carrier control required for AE gain in 2D semiconductors with intrinsically high sheet density.

Optical physical unclonable function

2017 IEEE 60th International Midwest Symposium on Circuits and Systems (MWSCAS), 2017

Many military and commercial systems require a unique digital identification for authentication, ... more Many military and commercial systems require a unique digital identification for authentication, key derivation, and other purposes. Our approach uses an optical physical unclonable function (PUF) that can be implemented on printed circuit boards (PCB). Various environmental factors, such as physical stress, temperature, heat dissipation, and aging, affect the effectiveness of such a PUF. This paper will discuss our recent research in addressing these and other concerns by advancing in the areas of waveguide construction, system longevity, and PCB cooling. We will also discuss the enhanced capability of differentiating between intact and disturbed systems.

Broadband optical switch based on liquid crystal dynamic scattering

Optics Express, 2016

This work demonstrates a novel broadband optical switch, based on dynamic-scattering effect in li... more This work demonstrates a novel broadband optical switch, based on dynamic-scattering effect in liquid crystals (LCs). Dynamic-scatteringmode technology was developed for display applications over four decades ago, but was displaced in favor of the twisted-nematic LCs. However, we show that with the recent development of more stable LCs, dynamic scattering provides significant advantages over other technologies for optical switching. We demonstrate broadband polarization-insensitive rejection of incoming laser irradiation by 4 to 5 orders of magnitude with switching times from clear to blocking state of 150 s. Further improvements in the switching times are possible with device engineering. No degradation of devices is found after hundreds of switching cycles. The light-rejection mechanism is due to scattering, induced by disruption of LC director orientation with dopant ion motion in the applied electric field. Angular dependence of scattering is characterized as a function of bias voltage. The dynamic-scattering mode technology should enable novel applications for laser light rejection and fast optical switching with performance better than the capabilities of current devices based on electrochromic, photochromic or twisted-nematic technology.

Download

Stress-enhanced mobility in MOSFETs fabricated in zone-melting-recrystallized poly-Si films

1981 International Electron Devices Meeting

N-channel enhancement-mode MOSFETs have been fabricated in Si films prepared by zone-melting recr... more N-channel enhancement-mode MOSFETs have been fabricated in Si films prepared by zone-melting recrystallization of poly-Si deposited on SiO2- coated Si, fused quartz, and sapphire substrates. Because the films on fused quartz are under a large tensile stress, the devices in these films exhibit surface electron mobilities as high as 860 cm2/V-s, compared to 620 cm2/V-s reported for similar devices in bulk single-crystal Si.

A new surface electron-emission mechanism in diamond cathodes

Nature

An electron-emission mechanism for cold cathodes is described based on the enhancement of electri... more An electron-emission mechanism for cold cathodes is described based on the enhancement of electric fields at metaldiamond-vacuum triple junctions. Unlike conventional mechanisms, in which electrons tunnel from a metal or semiconductor directly into vacuum, the electrons here tunnel from a metal into diamond surface states, where they are accelerated to energies sufficient to be ejected into vacuum. Diamond cathodes designed to optimize this mechanism exhibit some of the lowest operational voltages achieved so far.

Download

A novel anisotropic dry etching technique

Journal of Vacuum Science and Technology

ABSTRACT

Nitrocellulose as a positive or negative self-developing resist

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Nitrocellulose as a self-developing resist with submicrometer resolution and processing stability

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Effects of dry etching on GaAs

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

A number of dry etching techniques have been developed and their ability to produce anisotropic e... more A number of dry etching techniques have been developed and their ability to produce anisotropic etch profiles has been demonstrated. In addition to etch anisotropy, an important consideration for device and circuit fabrication is whether a sample suffers radiation damage by exposure to ions, electrons, or ultraviolet light during etching. In this study we evaluate the degree of radiation damage

The focused ion beam as an integrated circuit restructuring tool

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

One of the capabilities of focused ion beam systems is ion milling. The purpose of this work is t... more One of the capabilities of focused ion beam systems is ion milling. The purpose of this work is to explore this capability as a tool for integrated circuit restructuring. Methods for cutting and joining conductors are needed. Two methods for joining conductors are demonstrated. The first consists of spinning nitrocellulose (a self-developing resist) on the circuit, ion exposing an area, say, 7 X 7 µm, then milling a smaller via with sloping sidewalls through the first metal layer down to the second, e-beam evaporating metal, and then dissolving the nitrocellulose to achieve liftoff. The resistance of these links between two metal levels varied from 1 to 7 n. The second, simpler method consists of milling a via with vertical sidewalls down to the lower metal layer, then reducing the milling scan to a smaller area in the center of this via, thereby redepositing the metal from the lower layer on the vertical sidewall. The short circuit thus achieved varied from 0.4 to 1.5 0 for vias of dimensions 3 X 3 µm to 1 X 1 µm, respectively. The time to mill a 1 X l µm via with a 68 keV Ga+ beam, of220 Pa current is 60 s. In a system optimized for this application, this milling time is expected to be reduced by a factor ofat least l 00. In addition, cuts have been made in 1-µmthick Al films covered by 0.65 µm of Si0 2 • These cuts have resistances in excess of 20 MO. This method of circuit restructuring can work at dimensions a factor of 10 smaller than laser zapping and requires no special sites to be fabricated.

Download

Ion-beam-assisted etching of diamond

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

ABSTRACT

Nanochannel fabrication for chemical sensors

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

Although biochemical analysis techniques such as ion mass spectrometry, gas and liquid chromatogr... more

Michael Geis

Uploads

Papers by Michael Geis

Log In