Paul R Berger, Ph.D. - US grants

9624160 Berger This research project will examine and develop the Group IV alloy system (Si, Ge, C and Sn) studying material properties, fabrication techniques and electronic and photonic devices unique to the Si1-x-y-zGexCySnz system. Special attention will be focused on Si1-x-yGexCx alloys due to their inherent lattice matching ability to Si substrates, but not be limited to these alloys. Vegard's law predicts that an 8.2 to 1 ratio of Ge to C will be lattice matched to Si substrates. Among the benefits gained would be development of high performance Si-compatible heterostructure electronics as well as Si-based alloys and heterostructures with enhanced optical properties. The project commences with development of material issues related to these alloys by probing their optical, electronic and structural properties. Concurrently, the project will develop processing techniques such as etching and metalization, which could be unique to this material system. Optimized fabrication techniques will be applied to manufacture electronic and optoelectronic devices and circuits. High performance electronic devices such as heterojunction bipolar transistors (HBT) and modulation-doped field effect transistors (MODFET) would be ideally suited to the bandgap engineering possible with development of lattice matched heterstructure on Si substrates. Devices with enhanced photonic properties such as optical detectors and emitters will also be a primary focus. In addition to the research plan outlined above, and educational plan will involve four main thrusts. These four goals will be: 1. to attract women, under-represented minorities and persons with disabilities to get involved in research at the undergraduate level in order to promote future teachers from these groups; 2. to strengthen the undergraduate curriculum on semiconductor materials and devices by building lab demonstrations and competitive lab resources for the undergraduate teaching lab; 3. to develop a new M aster's degree in Electrical Engineering on Interconnect Technology; 4. to build a support structure for the retention engineering majors. ***

ECS-9906260
Berger

A team is being built amongst the University of Delaware, the Naval Research Laboratory, Raytheon Systems Company, and Delaware State University, a historically black university, to perform joint research and student training in industry and government laboratories. This proposal seeks support for the development of Si-based tunnel diodes which meet two criteria:

1. Peak-to-valley current ratios (PVCR) which exceed 4:1.

2. Process compatibility with standard CMOS or HBT integrated circuit processing.

Tunnel diodes which simultaneously meet these requirements will augment existing tran-sistor technologies by increasing bandwidth, lowering power consumption, and reducing the component count of standard circuits. It should be noted that while the prior work of this team has primarily dealt with resonant interband tunneling diodes (PJTD), this project will remain open to any Si-based tunneling device design which meets the above two require-ments. Achieving high PVCRs require tunnel diode designs which simultaneously maximize the tunnel current and minimize valley currents. As such, it is essential to develop a thor-ough knowledge base of the physics underlying tunneling phenomena. A low temperature study of the phonon structure will help to select an appropriate tunnel barrier. A simulta-neous study of the influence of gap states and deep levels will identify the media underlying excess current. The results of these experiments will serve to improve modelling software and will be essential to the engineering of high PVCR Si-based tunnel diodes. The role of Si1-x Gex tunnel barriers will be investigated as well.
All members of the team will help in the design of structures and experiments to be performed as well as the interpretation of the data. In addition, the University of Delaware will be the primary partner responsible for device fabrication and testing. The Naval Research Laboratory will focus on the molecular beam epitaxial growth of the tunnel diodes, while Raytheon Systems keys on modeling, modeling software, some unique device fabrica-tion, and low temperature electrical measurements. Delaware State University will focus on low temperature photoluminescence using UDelaware facilities. A free flow of information between these parties as well as student visitation to each other's facilities (2 days to 1 week every 3 months) for technical discussions and experimentation is envisioned. Some testing services (deep level transient spectroscopy) will be outsourced.

This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119). The project addresses the fabrication of quantum scale devices through the combined oxidation and etching of Si/SiGe/Si nanostructured pillars. The project aims to demonstrate the validity of nanoscale computing by developing a process technology to fashion quantum dots of a predictable size, shape and placement, suitable for mass production and simple electrical contact. The project includes specific strategies and processes to control the size and composition of the nanostructured pillars and the resulting quantum dots and oxide insulators to be formed. The research spans issues of materials science, circuits, and device fabrication and characterization; the structures to be fabricated are closely integrated with quantum level devices necessary for cellular automata circuits. Methods of high speed testing to characterize the devices as well as theoretical modeling to optimally design the structures are included. The project is highly collaborative between Ohio State, Illinois, Notre Dame, UC Riverside, the Naval Research Laboratory and Air Force Research Laboratory.
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The project addresses basic research issues in a topical area of materials science with high technological relevance. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project brings together electrical engineers, material scientists, physicists, computer scientists, experimentalists, and theoreticians for the purpose of realizing advanced nanostructured quantum dot devices. The project is designed to develop strong technical, communication, and organizational/management skills in students through unique educational experiences made possible by a forefront research environment. There will be active involvement of undergraduates in the program with an emphasis on developing effective oral and written communication skills. Cross-disciplinary research and site visits to each other will enhance the educational process. The project is co-supported by the DMR/EM and ECS/EPDT Divisions/Programs.
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To advance the state-of-the-art in conjugated polymeric transistors by examining ordered conjugated polymer systems and developing ways to engineer it for enhanced mobilities and improved current drive capability. This project will investigate polymeric thin film transistors (TFT) using oriented conjugated polymers to elevate mobility and polymers doped with low molecular weight compounds to enhance charge injection. Recipes and materials developed in Germany will be used to orient and dope the polyflourenes and apply them to polymeric field effect transistors (FET). Processing schemes will be developed to fabricate prototypes which reduce the source/drain resistance to the channel while maintaining compatibility with polymer processing.

This project team will design, fabricate and test polymeric field effect transistors to advance active matrix polymeric flat panel displays. Large area displays, which could be manufactured using cheap reel-to-reel batch technology, and which are ultra-thin and flexible could become a reality soon. Flexible displays and low production costs make light emitting polymers (LEP) a competitive option for the manufacture of flat panel display technology. Development of polymer electronics will fuel this revolution by their integration with LEPs into smart pixels for active matrix displays. This proposal addresses some of the key impediments to this realization.

This award from the Instrumentation for Materials Research program supports the acquisition of an inductively coupled reactive ion etching (ICP-RIE) system at The Ohio State University. This facility will immediately generate new materials and materials-allied research programs at Ohio State with substantial teaming amongst interdisciplinary partners. It will have enormous impact on a very wide range of existing electronic materials - based research programs in several academic departments, many of which are currently supported by NSF. The equipment is engineered for research level and pilot line plasma processing using corrosive processing gases such as Cl2, BCl3 or SiCl4. It has an automatic switch dual power range RF generator, which makes etching possible under very low ion energies. The formation of this facility will allow the coalescence of inter-university research programs across the state, that span fundamental studies on the effects of ICP-RIE processing on the properties of semiconductors to the development of novel device structures, heterostructures and nanostructures. The equipment chosen for this purpose is explicitly designed for such flexible utilization, so that the breadth of activities and wide ranging impact expected will be achieved.
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With this award from the Instrumentation for Materials Research program The Ohio State University will establish a state-of-the-art facility for the plasma processing of a wide range of electronic and photonics materials, with the acquisition of an inductively coupled reactive ion etching (ICP-RIE) system. This facility will immediately generate new materials and materials-allied research programs at Ohio State with substantial teaming amongst interdisciplinary partners. Once in place, the ICP-RIE will rapidly attract local and statewide industrial joint projects ranging from sensor technologies to photonics and energy conversion technologies. To ensure open access to multiple users, the ICP-RIE system will be placed into our well-established Semiconductor Processing Clean room structure to be employed in the research and education of dozens of undergraduate and graduate students and postdoctoral associates from both inside and outside Ohio State. Finally, the ICP-RIE system will allow us the ability to process a wide range of materials, a core capability that we are currently lacking. This system will complement existing facilities in the clean room, and thus its impact will be greatly enhanced by the leveraging obtained via almost all projects using the clean room facilities.

0323657
Berger

The drive to develop advanced semiconductor devices and circuits is fueled by
the wealth of electronic and optical properties of heterostructures made possible by band structure engineering. Tunnel diodes (TD) can be integrated with transistors to create novel quantum nonlinear functional devices and circuits due to the unique property of a tunnel diode's negative differential resistance (NDR). Such integrated circuits have demonstrated enhanced performances in circuit speed, reduce component count and lower power consumption. Previous circuit work incorporating TDs, at places like Motorola Laboratories, has been limited to III-V compound semiconductors only. However, until recently, it was not practical to translate this to the low-cost and high production volume Si world. But recent developments in Si-based TD technology by the PI and other researchers are challenging this roadblock. One aim of this proposal is to seek ways to integrate Si-based resonant interband tunnel diodes (RITD) with Si/SiGe transistors to meet the challenges in the wireless communications by transferring
this III-V-based TD circuit technology to Si. The PI seeks to capitalize upon recent DC performance milestones achieved within his laboratory on Si-based RITDs, namely peak-to-valley current ratio (PVCR) up to 3.8 at room temperature or peak current densities Jp exceeding 150 kA/cm 2 .

This project aims to boost Si wireless capabilities that could eventually lead to an
entire radio on a single Si chip or other interesting fusions of digital and analog circuits. Further, tunnel diodes have been shown to be very radiation hard and were used extensively in some of the first communication satellites in the 1960's, thus lending their introduction into military and non-terrestrial applications as well. Partnering with Motorola Laboratories in the form of a Grant Opportunities of Academia in Liaison with Industry (GOALI) is testimony to the level of interest and curiosity of industry to explore this technological pathway further, before embracing it. Motorola is willing to share their circuit and system experience as well as apply their in-house analog modeling of these nonlinear Si/SiGe TDs.

This project will provide an environment where students can be trained in a broader
perspective of the research process, from device physics, material and device processing, to device and circuit testing and modeling. Collaborative efforts required in this project will allow graduate and undergraduate students not only to have natural exchange and supervision with PIs, but also to have strong interactions with scientists in government and industry research laboratories, which will facilitate their acquisition of knowledge and provide an initial research experience that promotes the notion of teaming in their future careers. At Ohio State (Berger), undergraduate research is expected to play a large component in the proposed research. Discussions have already commenced with the EE Honors Program representative and the PI to ramp up towards a collective REU Site submission in Fall 2003. In lieu of this, the PI will submit requests for REU supplements as well as the REU Site request. The PI has a long and established history of using undergraduate researchers through REU supplements. Recruitment of underrepresented peoples has been and will be a facet in the PIs research projects.

The technical merits of this project derive from its impact on (i) increase circuit speed
due to shortened path lengths and increased functionality, (ii) reduce component count (more computational power per unit area), (iii) lower power consumption (fewer components per logic function), (iv) compact the layout using 3-D integration of tunnel diodes above/below transistors, and (v) extend RF wireless technology.

The objective of this research is to advance polymer tunnel diodes and circuits for ultra-low power self-powered computing. Advances by this team for the first conjugated polymer based tunnel diode circuitry using room temperature negative differential resistance (NDR) enable new opportunities for low-power consumption circuitry (logic, memory and mixed-signal). NDR circuitry can provide (i) component count reduction (more computational power per unit area), (ii) lower power consumption (fewer devices per logic function). This extends beyond the functionality and on-board intelligence of organic RFIDs while operating autonomously powered. The approach will use a systematic exploration and development of polymer tunnel diodes in three vertically integrated research thrusts: (i) novel materials, (ii) device technology, and (iii) system applications and impact.

The proposed project will establish a world-class program in polymer tunnel diodes that will advance low-power autonomous powered electronics, low-temperature processing of high-k dielectrics, understanding of role of defects in tunneling through ultra-thin high-k dielectrics, biosensors and polymer solar cells.

The integrated research, education and technology transfer will advance SmartCard technology (credit cards and identification cards) with greater on-board intelligence, permitting enhanced data manipulation, distributed computing, radio frequency (RF) input/output (I/O) datalinks, and possibly even hardwired encryption algorithms to protect personal data better than traditional magnetic strips. The proposed research project will create a unique and focused program that incorporates a wide-range of external collaborations with industry, government labs and academia.

The objective of this research is to develop highly sensitive silicon-based sensor elements, monolithically integrated with silicon microelectronics, for passive millimeter-wave camera systems. The research is based on the development of a silicon backward diode by this group, providing new opportunities for a fully silicon-based front-end solution. The research approach includes miniaturization of the backward diodes, characterization of their radio frequency performance, and modification of the tunneling junction design and epitaxial growth to achieve high sensitivity concurrently with low resistance. Guidance towards system-level integration will be provided through close collaboration with Traycer Diagnostic Systems.

Intellectual Merit: Silicon-based sensor technology at the materials and device levels will be studied for their viability in millimeter-wave imaging systems. Specific advances targeted in this research include: (i) cost-effective sensing through lower-cost devices, increased packaging yield and reduced assembly cost; (ii) improved imager performance and reduced imager weight through reduced number of packages and simplified packaging needs; (iii) larger imager pixel counts for improved resolution; (iv) improved uniformity of imaging array for enhanced image quality; (v) operation at room temperature; and (vi) operation at zero bias, virtually eliminating 1/f noise.

Broader Impacts: The research is expected to significantly advance millimeter-wave imaging technology for a range of security and safety applications including detecting concealed weapons hidden on a person below clothing and pilot vision through obscuring media (e.g., rain, fog, smoke), such as for an aircraft landing in a fog-bound airport. This project includes domestic and international collaborations with Traycer Diagnostic Systems, Inc., the Naval Research Laboratory and the Intra-University Microelectronics Center (IMEC) in Leuven, Belgium. The project will train both graduate and undergraduate students including students from underrepresented groups.

Research Objectives and Approaches:
The objective of this research is to advance organic solar cells using tailored chemistries of metallic nanoparticles that when assembled into a thin film act like tiny lenses across the film surface to focus sunlight onto the light absorption region. When metal nanoparticles are aligned into a perfect periodic checker-board array, they can create a plasmonic resonance leading to a high augmented absorption. There will be a significant leveraging through an alliance with the local company, MetaMateria. Also, collaborations with Prof. Terry Bigioni will further expand the scope of study. Metamateria will fashion nanoparticles to be placed adjacent the active collection region and Bigioni will create nanoparticles to be placed inside the active region. The addition of Prof. James Coe from Ohio State's Chemistry provides an experienced background with modeling plasmonic optical effects.

Intellectual Merit:
The proposed project will establish a world-class program in polymer solar cells that will advance low-cost polymer solar cells using plasmonics. The development of unique and tailored nanoparticles chemistries with MetaMateria will be a platform technology for other applications, such as fuel cells and water purification, which are key commercialization thrusts for Metamateria

Broader Impacts:
Through collaborations with industry, we will increase the competitiveness and position of US industry and advance the efficiency and functionality of solar cells. Participation of industry will broaden the culture of innovation and focus the research output towards strategic commercialization. Undergraduate researchers will provide valuable and substantive contributions to the proposed work.

Abstract:

Non-technical: The team at Ohio State University, through an accidental discovery under NSF, is undergraduate research funding, developed and advanced a new organic tunnel diode using a hybrid junction incorporating a thin metal oxide and a solution-based organic semiconductor atop. This patented device is the first such structure to genuinely exhibit selective tunneling at room temperature using a scalable printable process. The current versus voltage characteristics are unique amongst semiconductor devices, looking like a capital letter (N). So, unlike most devices, a line drawn through this (N) provides three intersections. The middle is unstable and unusable, but the first and third provide for a simple way to store 1-bit, a (0) or a (1), using a single tunnel diode with another circuit element, such as a second tunnel diode or transistor, as the load. This project builds upon previous advances by building a multi-institutional team (Wayne State University, Tampere University of Technology, Aalto University and Picosun) spanning two countries (USA and Finland). The properties of this thin metal oxide tunneling barrier are key to the discovered operation. This project seeks a new way to deposit this layer that would permit large area deposition across flexible substrates, reaching a meter wide. Through collaborations with Finnish industry, we will increase the competitiveness and position of US industry and advance the intelligence and functionality of organic electronics, solar cells, electronic printing and atomic layer deposition technology. Participation of industry and international collaborators will broaden the culture of innovation and focus the research output towards strategic commercialization.

Technical: Ohio State University (OSU) proposes a 3-year bi-national (USA, Finland) project to advance printed organic electronics, particularly using organic tunnel diodes (OTD) and circuits integrated with organic field effect transistors (OFET). Their unique negative differential resistance (NDR) will reduce OFET device count, while concurrently reducing power consumption. Energy thrifty circuits will be key for autonomously powered sensor nodes for a dense network of trillions of objects for the Internet of Things (IoT). International teaming with Tampere Univ. of Technology (TUT-Finland) and Picosun (Finland), an atomic layer deposition (ALD) tool manufacturer, will provide collaborative opportunities for large-area rapid roll-to-roll (R2R) technologies to prototypical scale-up of the existing fundamental studies while enhancing materials discovery and understanding. A key aim of this project is working with Wayne State University (WSU) for novel ALD precursor and oxidizer discovery and process development to explore non-stoichiometric ALD for metal oxide tunnel barriers with engineering oxygen vacancies (energy level of defects, density-of-states, etc.) that critically control OTD defect related tunneling processes and therefore device performance based on NDR. Advances by this team for the first conjugated polymer based tunnel diode circuitry using room temperature NDR enable new opportunities for low-power consumption portable circuitry (logic, memory and mixed-signal). NDR circuitry can provide (i) component count reduction (more computational power per unit area), (ii) lower power consumption (fewer devices per logic function). Tremendous benefits to society and humankind: 1) Low-cost, ultra-low power autonomous plastic electronic memory, logic and wireless systems; 2) Advanced high-K dielectrics compatible with the limited thermal budget of organics; 3) Understanding of defects and their role in tunneling transport through thin high-K dielectrics; 4) Large-area, R2R electronic printing for high volume production. Students and international exchange: A full-time graduate student will be directly supported here. REU supplements will supplement this team with 1-2 undergraduates, along with international scientific visitations.

A 3-year tri-university (Ohio State, Wright State and Texas State) project is proposed to advance a new class of efficient and stable oscillator circuits based upon quantum tunneling. It will explore a class of tunnel diode based relaxation oscillators and extend this to a novel domino effect pulse amplifier design. Past stability issues of tunnel diode based oscillators are addressed by oscillating beyond the negative differential resistance region. This larger voltage swing also provides for significantly larger output powers. Effort will be made to extend their operational frequency beyond the state-of-the-art through electromagnetic modeling simulations. Their simplicity and low-power consumption could also make them a candidate for Internet-of-Things objects. Tunnel diode based electronics provides a pathway for energy thrifty "green" circuitry with concurrently high output power and with unprecedented stability. A full-time graduate student will be directly supported at both Ohio State and Wright State. The shortlist candidate graduate student for each group are both female undergraduates who began their research career as undergraduates in Berger's lab. Supplemental funding requests will be applied for to support 1-2 undergraduates additionally, along with scientific visitations, to perpetuate this legacy. This project provides tremendous benefits to society and humankind by advancing low-cost, ultra-low power consumption radio frequency sources, and stable radio frequency sources for new advances in compact clock signal generation.

A key aim of this project oscillator design, transmission line modeling and radio frequency measurements to develop and mature a new type of stable tunnel diode based oscillator that addresses the tunnel diode stability issues by oscillating beyond the negative differential resistance region. This larger voltage swing also provides for significantly larger output powers. Advances by this team, leveraging their first report of the experimental determination of the quantum-well lifetime influence upon the large-signal resonant tunneling diode switching time, this team now is poised to advance compact oscillator circuits with high conversion efficiencies, generating large and stable output powers. The tunnel diode based circuitry will provide (i) for the significant advancement of relaxation oscillators that address the tunnel diode stability issues which thwarted resonant tunneling diode adoption, and (ii) creation of a wholly new "domino amplifier" that daisy chains each relaxation oscillator stage to the next using progressively larger tunnel diode sizes with concurrently increasing output powers. Without the stability afforded by the relaxation oscillator design, large tunnel diode based oscillators would be too unstable, and thus prevent this novel approach. The relaxation oscillators have been studied in the past and shown to produce radio frequency output power exceeding 1 mW, as expected, but their maximum (repetition) frequency of oscillation has only been 50 GHz], well below the expectation. This will be an early topic of the proposed study where full- wave electromagnetics and nonlinear-device/circuit interactions will be simulated, especially examining the effect of planar-transmission line dispersion and short-circuit reflectance. This knowledge will then be used to demonstrate a totally new and potentially revolutionary tunnel diode switching component - the "domino" pulse amplifier. The domino amplifier has the ability to utilize inherently fast tunnel diode switching to create unilateral, large-signal gain. All of the materials for the proposed effort will be InP based. These materials have produced some of the best resonant tunneling diodes to date as measured by peak-to-valley current ratio, peak current density, maximum frequency of oscillation, and switching time. A systematic exploration and development of resonant tunneling diode technology in three vertically integrated research thrusts: (i) advanced epitaxial control and quantum-based device physics design using non-equilibrium Green's function, (ii) compact high-power resonant tunneling diode based relaxation oscillators, (iii) novel domino amplifiers, and (iv) nonlinear-device, integrated-circuit interaction and electromagnetics.

The goal of this project is to explore a new class of ultra-fast optical emitters. Those optical emitters will provide (i) for the significant advancement of direct modulation optical emitters, and (ii) creation of a wholly new optical emission pathway which is expected to exceed previous designs, while mitigating efficiency losses. Applications of such devices include fast clocks, and systems such as optical communication and LIDAR.
Through a collaboration between the Ohio State University and the Wright State University, a significant exposure to research, particularly under-represented groups, will help to advance the field of RTD-based emitters while providing for a haven of educational nurturing. The team will also focus appropriate results of this the research output towards strategic commercialization.
The collaborative team will explore this new class of resonant-tunneling-diode (RTD)-based emitters as a source of ultra-fast direct modulation emitters. It is believed that, since the slow holes are generated without highly resistive p-type doping and are created by Zener tunneling exactly at the point of carrier recombination and optical emission, these optical emitters will bypass many of the slow mechanisms that have prohibited fast direct optical emitters in the past. A key focus of this project is working on cavity design, balancing of hole and electron currents using the PIs own hybrid combined analytical-numerical physics models, design and modeling of thermal management and heat extraction, fabrication and testing of ultra-fast direct modulation light emitters. The aim is to achieve the first demonstration of ultra-fast direct modulation using quantum co-tunneling. The expected impact of the research includes: 1) Low-cost, ultra-fast optical sources, and (2) self-clocking optical emitters for compact clock signal generation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.