Time-dependent dielectric breakdown (TDDB) is becoming a critical reliability issue in VLSI design, since the electric field across dielectrics barriers increases as technology scales downward. Moreover, dielectric reliability is aggravated when interconnect spacings vary due to misalignment between via and wire masks. Although dielectric reliability can be mitigated by a larger interconnect pitch, such a guardband leads to significant area overhead. (more...)

A novel method of enhancing the thermoelectric properties of materials used in thermoelectric power generation.  (more...)

Thermoelectric devices are made from rigid bulk or bulk like material which are inherently inflexible. Alternative thermoelectric device designs which incorporate semiconducting nanowires are able to be rigid and yet be flexible.   For example, despite the rigidity of semiconducting nanowires they can move independently from each other, enabling flexible thermoelectric device designs. The use of rigid or semi-rigid electrodes for flexible thermoelectric devices causes many difficulties including but not limited to stiffening the device, creating stresses in the active material contacts, and fracturing the active material and contacts. Flexible metallic materials are essential in developing thermoelectric device as envisioned by UCSC researchers.   (more...)

A novel technique for the integration of small complementary metal-oxide semiconductor (CMOS) chips into a large area substrate. (more...)

Unlike conventional FETs that operate on electric current, spin FETs utilize the application of an electron's two spin states. In order to compose a spin FET, a ferromagnetic material is placed between two semiconductors. A key advantage of using spin FETs over traditional FETs is that the spin state of an electron can be detected and altered without necessarily requiring the application of current. Today, FETs are the fundamental building block for electronic devices however the spin FET may eventually provide a viable alternative to Si CMOS technologies. The paramount challenge to constructing spin FETs is the process of electronically injecting spin-polarized electrons or holes into the semiconductor channel region at room temperature. The electrical conductivity mismatch between ferromagnetic materials and semiconductors make efficient spin injection fundamentally prohibitive for diffusion based current injection. Another approach to constructing spin FETs is to use a tunnel injection method but this procedure creates a high contact resistance which is detrimental to FET operations. Thus, a more efficient spin injection approach is needed for the realization of efficient spin FETs. (more...)

A process for creating a novel type of active current-blocking layer to allow the device current to only pass through the aperture. (more...)

Photolithography, an essential process in the fabrication of integrated circuits, has undergone continuous advancements that allow patterning of nanometer sized features. For example, features as small as 50 nm can be made by using excimer lasers with wavelengths of 248 nm and 193 nm (i.e., deep ultraviolet light). However, it is not always feasible for scientists to use the short wavelength lasers because they are expensive. A method that allows for high resolution photolithography without large capital expenses will be very useful. Researchers at the University of California, Irvine have developed a photolithography method that allows for high resolution patterning. By using this method, one can get a 20-fold improvement in the limit of resolution in comparison to the inherent resolution of “top-down” processing. In addition, the method is easy to use, inexpensive, and does not require sophisticated instrumentation. (more...)

A cantilever waveguide fabricated from laminate materials and integrated onto a printed circuit board (PCB). New fabrication and packaging methods were also developed in creating an electro-optical sensor device. (more...)

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A new avalanche photodiode that is low noise and provides a highly stable gain at small bias voltages. (more...)

Lighting is a major contributor to electricity consumption, accounting for 19 percent of global use and 34 percent in the U.S. The U.S. lighting market is currently dominated by the incandescent light bulb, which is only 5 percent efficient whereas the fluorescent lamp is 15 to 25 percent efficient. Solid-state luminaires, which are typically based on light-emitting diodes (LEDs), have the potential to revolutionize the industry with higher efficiency, better quality, and lower maintenance, possibly leading to a reduction of half the energy consumed by general illumination. For example, 30 percent efficiency has been achieved in a commercially available white LED and 50 percent in a laboratory white LED device. White light in such devices is produced either by combining light from different color LEDs or taking blue or near-UV light from an LED to “pump” a mixture of phosphors. The phosphor approach, when implemented with conventional phosphors, produces cold white light that is not color tunable and has non-optimal efficiency, but has the potential to overcome these shortcomings with the use of advances in materials.The appreciable energy savings derived by converting from incandescent to fluorescent lamps and solid-state lighting has spurred government measures towards phasing out incandescent light bulbs. The general lighting market is predicted to exceed $130 billion by 2011 with the LED-based share forecasted to grow to $1.4 billion by 2012. There is clearly an unmet need and great market opportunity for new energy-efficient lighting devices. (more...)

The uniformity of each droplets volume in a digital microfluidic system is useful and often critical to the overall functions. Digitization of liquids, e.g. generating droplets from liquid reservoirs, is a key step to determine the droplet volume. Reasonable level of accuracy can be achieved by simple signal switching during the digitizing processes. However, the performance is subject to random variations over the devices and operation conditions. The known feedback mechanisms to control droplet uniformity required external equipments (pumps and valves) in the system hardware and closed the loop once per droplet in the feedback algorithm (i.e., the feedback is droplet-to-droplet). (more...)

Because of nonlinear effects, it is virtually impossible to generate useable submillimeter waves of a frequency greater than 190GHz using CMOS oscillators. In conventional oscillator circuits, which are nonlinear systems, increases in frequency are accompanied by a corresponding loss in gain or efficiency and an increase in noise. (more...)

Micropumps are a critical element of microfluidics, as they are required to move small volumes of liquid in a controlled, energy-efficient manner. Several categories of micropumps have been reported, such as mechanical micropumps, electrokinetic micropumps, and valveless bubble-driven micropumps. The valveless bubble pumps are attractive for microfluidics because of their simplicity in fabrication over mechanical pumps and their flexibility in working liquids over electrokinetic pumps. The preferred method to date of generating bubbles in the valveless pump is by thermal generation (boiling). However, this method has several limitations. First, boiling requires high levels of energy to induce vapor formation. Second, the vapor condenses back to liquids much slower than they boiled, which limits the cycling speed of the pumping action. Another common bubble generation methods for the valveless pump is electrolysis, but they are not suitable for closed systems, such as fuel cells, because of the inability to eliminate the gas bubbles. (more...)

This invention is a part of a research effort that will enable a quantam leap in the performance of high bit rate optical communication systems. The research products of this effort will include femtosecond semiconductor lasers with high pulse energy.Monolithic mode-locked semiconductor lasers generating sub-picosecond optical pulses with high pulse energy play an important role for electro-optic sampling and high bit rate TDM systems. Though such short optical pulses have been demonstrated in semiconductor gain medium using external cavities and additional pulse compression, those lasers are very bulky and not suitable for practical applications. Monolithic mode-locked semiconductor lasers are compact, light weight, energy efficient and do not require optical alignment. Although very impressive performance (600 fs pulse width, 350 GHz repitition frequency) has been demonstrated, the pulse energy of this type of multiple-contact quantum well lasers is limited by the intra-cavity saturable absorber (approx.10 fJ). Such energy is insufficient for most all-optical switching/demultiplexing systems.The subject invention is a new integration scheme for realizing novel femtosecond semiconductor lasers with an integrated antiresonant Fabry-Perot saturable absorber (A-FPSA). Such lasers have several unique advantages: (1) ultrashort pulse generation that fully exploits the gain bandwidth of semiconductor quantam wells; (2) high power operation (average power > 50mW) because the saturable absorber is placed inside the antiresonant FP cavity; (3) it enables intra-cavity dispersion compensation for the first time in monolithic cavities, which could further shorten the pulse width (the gain bandwidth of semiconductor could support pulses as short as 50 fs). These performances represent one to two orders of magnitudes improvement over the conventional monolithic mode-locked lasers. In this scheme, the saturable absorber is decoupled from the gain medium and, therefore, can be separately optimized for shorter pulses. For example, it can be made into fast saturable absorber by employing low-temperature grown GaAs. (2) By placing the saturable absorber layer inside an antiresonant Fabry-Perot cavity, its saturation energy can be increased by 100 times (1 to 10 pJ). Thus much higher peak/average power can be obtained from the proposed femtosecond semiconductor laser. (more...)

The invention provides an electronic circuit that realistically mimics the function of a memory resistor. The memory resistor emulator may be used alone or as a part of an electronic circuit. The memory resistor emulator includes several intrinsic features of a memory resistor. First, from the point of view of an external circuit, the memory resistor emulator behaves as a passive electronic device. Second, the response of the memory resistor emulator to the applied voltage can be selected very close to the response of a real memory resistor. Third, the frequency behavior of the memory resistor emulator (in a certain frequency range) can also be selected very close to the frequency dependence of the real memory resistor. (more...)

For the first time in the history of the multi-billion-dollar data storage industry, the conventional technology cannot be further scaled because of the fundamental limits of the materials. Specifically, superparamagnetism limits memory density in conventional technology.   Heat assisted magnetic recording (HAMR) is believed to be one of the most promising alternative technologies  developed in order to pack more memory into less space. The success of HAMR and other optical storage technologies depends on having a means to focus light in nanoscale spots with adequate intensity to record data. Currently, methods exist to focus lasers on small spot sizes, but these techniques do not deliver adequate power.    Researchers at the University of California have developed a near field optical system capable of delivering light into a spot with a diameter of less than 30 nm and power values of above 100 nW. Furthermore, this technology is scalable down to a 5-nm diameter spot. The device is simple to manufacture using existing technology.      The images above depict the UC nanolaser focused on an aluminum coated probe and the corresponding near-field intensity distribution of the spot.    UC’s nanolaser could enable recording media with areal densities of greater than 10 terabits per square inch. With this technology the entire library of Congress could be carried in your wrist watch. The nanolaser could be used in various memory applications such as HAMR, protein based memory, and 3-dimensional multilevel recording. Additionally, the nanolaser could be used in future nanooptic or nanophotonics application such as optical interconnects to replace contacts and wires in future electronics, nanolasers for medical applications for ultra-precise diagnostics and surgery. (more...)

This batch-processed MEMS device features a large magnetically actuated force that is electrostatically addressed. It facilitates microstructures with high areal density and increased design flexibility. Also, its torsional flexure structure constrains motion to rotation about a single axis - which is ideal for various applications including micromirror systems as well as optical scanners, displays and switches. (more...)

Silicon-On-Insulator (SOI) technology has many advantages over its conventional bulk counterpart. However, SOI?s inherent floating body effect and high source/drain series resistance cause non-ideal behavior. Two new fabrication technologies developed by researchers at the University of California, Berkeley solve these SOI problems. The first technology is a low-barrier body-contact scheme that provides a substrate contact to the floating body for substrate current collection, thereby eliminating the floating-body effect. MOSFETs fabricated with this technology show bulk-like output resistance, high voltage gain, and low flicker noises. This design consumes a very small amount of area and is very effective in substrate current collection. The second technology is a recess channel MOSFET that consists of a thicker source/drain region and a thin channel, thereby resulting in a low source/drain series resistance without the use of a silicide. Furthermore, with this technique, ultra-thin film SOI MOSFETs can be fabricated without regard to the silicon consumption in the source/drain region when making contacts. (more...)

In microchip structures the spaces between the metal elements in an interconnect structure are filled with solid dielectrics that typically have dielectric constants greater than two. This design approach, while somewhat effective, severally limits efforts at miniaturization of electronic components, an important motivator for current consumer products. In response to these challenges, researchers at the University of California, Berkeley have developed a novel structure and method of fabrication of metal elements which are supported by thin dielectric walls and open corridors which separate the walls from each other. Using this approach, the metal elements are effectively separated by the open corridors and not by a solid dielectric material. The corridors may be filled with a vacuum, or a partial vacuum, or a gas such as air, which typically have a dielectric constant of one. As a result, the parasitic capacitances between the metal elements can be reduced by about one-half, leading to improved circuit performance such as faster speed, lower cross-talk, and lower power consumption. (more...)

Transmit power consumption often governs the ultimate battery lifetime of portable wireless communications devices, and therefore transmit power amplifiers used in these devises are important to their commercial success. The efficiencies of these power amplifiers are set by the capabilities of the semiconductor transistor devices that drive them. The most efficient power amplifier configurations operate their semiconductor transistors as switches that, if ideal, would not dissipate any power, making these amplifiers theoretically capable of achieving 100% drain efficiency. However, semiconductor transistor switches are not sufficiently ideal to allow these power amplifiers to achieve their efficiency potential. Instead, their finite series resistance, large input capacitance, nonlinear drain capacitance, substrate losses, voltage limitations, and temperature dependencies all contribute to lower effective efficiency. To achieve a more ideal efficiency for power amplification configurations, researchers at UC Berkeley have developed a switch design that reduces or eliminates many of the efficiencies of semiconductor transistor switches. In overcoming the long-standing impasse in power amplifier advancement, this innovative switch has the potential to open many new opportunities that include not only an increase in the talk-time of portable battery-powered wireless transceivers, but also a significant increase in the range of high power transmitters. The higher efficiency enabled by this Berkeley switch reduces the power dissipated in the amplifier itself, thereby lowering its temperature and allowing a further increase in output power -- that is further accommodated by the large voltage handling capability and better temperature resilience of the switch. The net result is a high power transmitter in a smaller and lower weight package. (more...)

Millimeter-wave systems can be used in many security and sensing applications including weather monitoring, vehicle crash avoidance, and aircraft landing guidance. These systems could significantly benefit from advanced tunable filters, especially for multi-channel communication systems. State-of-art tunable filters use solid-state varactors, but this design approach incurs high insertion loss, unacceptable signal-to-noise ratio, and rendered linearity. Tunable filters can also be designed using RF MEMS technology, however most of the existing designs of this type are discrete, lack the required resolution to continuously cover the desired operating band, and also suffer from high insertion loss. To address this problem, researchers at UC Berkeley have developed, demonstrated and characterized a new approach to designing W-band tunable filters. Prototypes of this Berkeley filter exhibited a 4.05 GHz bandwidth centered at 94.79 GHz with a minimum insertion loss of 2.37 dB, a return loss better than 15 dB, and a center frequency shift of 2.59 GHz. This novel type of tunable filter can also function in a dual role as a phase shifter. Prototypes achieved a phase shift of 110 degrees at 95 GHz. (more...)

Technological advances have allowed computer microprocessors to handle data at an extraordinary rate. However, the electrical interconnects within and between microprocessor chips introduce a severe bottle-neck to the flow of data. A promising architecture for next generation interconnects is high-speed and high-bandwidth optical interconnects, which will require heterogeneous integration of compound semiconductors with Si technologies. Some previously-explored methods for creating the optoelectronic circuitry include epitaxial growth, heteroepitaxial growth, and wafer-bonding. However, epitaxial growth of interconnections can produce large physical mismatches between desirable compound semiconductors and silicon; heteroepitaxial growth is complicated, expensive, and requires high processing temperatures that damage silicon-based circuitry; and wafer bonding is extremely susceptible to misalignments. Researchers at the University of California, Berkeley are developing advanced structures and methods for integration of compound semiconductors with conventional integrated circuit components to produce various active and passive optoelectronic components for optical interconnects, sensors, semiconductor lasers and other devices. The structures can accommodate quantum wells or quantum dots. The method under development at Berkeley will eliminate problems with alignment and processing temperature that constrain the application of conventional methods for fabricating optoelectronic circuitry. (more...)

The layout of electrodes in the design of modern MEMS resonators has been one of the crucial aspects in ensuring a small feed-through capacitance. Consequently, complicated design are neccessary that usually require vacuum packaging to make sure that the parasitic feed-through capacitance does not render the resonator unusable. This vacuum must be maintained for the lifetime of the resonator. Approaches used to ensure correct resonator operation include: reduction of the minimum gap in the MEMS mechanical structure; the addition of CMOS transistors on the same substrate as the MEMS mechanical structure also known as integration with electronics; and vacuum encapsulation of the MEMS during the resonator fabrication instead of package level vacuum packaging. To address this complexity, researchers at the University of California, Berkeley have developed a simpler oscillator circuit that eliminates the effects of parasitic feed-through capacitance on resonators. This new circuit allows the operation of resonators with values of feed-through capacitance much larger than previously possible. As a result the new design enables simplification of the overall oscillator and resonator design and allows more freedom in the resonator architecture. The packaging of the MEMS resonator is simplified thereby reducing cost and increasing reliability. Vacuum packaging is no longer needed and minimization of feed-through capacitance can be less stringent with the new oscillator design. The new oscillator circuit supports MEMS fabrication processes with large gaps, and no integrated electronics or vacuum packaging (chip or package level). (more...)

Multiple resonators with different frequencies are essential in the design of micromechanical filters, oscillators and mixers. Lateral-mode resonators with a variety of resonant frequencies can be fabricated in the same lithography step using surface micromachining technology. However, these lateral-mode resonators have inefficient air-gap capacitive transducers that cause high motional impedance. To address this problem, researchers at the University of California, Berkeley have developed an electrostatic transducer for lateral-mode resonators in which the electrode gaps are filled with a dielectric material that has much higher permittivity than air. Previous dielectric transduction mechanisms rely on Poisson coupling between the SiN and silicon. However, this internal electrostatic transducer is directly coupled to the bulk acoustic mode of the lateral silicon resonator. As a result, the Berkeley design enables more efficient coupling between the transducer and resonator, and offers the potential to make an FBAR device entirely out of TiO2 instead of AiN. This internal electrostatic transducer has several advantages over both air-gap electrostatic and piezoelectric transduction including: lower motional impedance, compatibility with advanced scaled CMOS device technology, and extended dynamic range. Moreover, energy losses are minimized in the Berkeley transducer by matching the acoustic velocity of the dielectric material to the acoustic velocity of the resonator material. (more...)

The integration of various CMOS-based technologies and structures on a single, batch-processed wafer has great commercial potential. However these technologies and structures frequently have incompatible material as well as thermal or wafer-size fabrication characteristics that lead to application constraints, performance trade-offs and higher costs. To address these problems, researchers at the University of California, Berkeley have developed a fabrication technique that efficiently merges incompatible technologies, processes or structures on a common wafer platform resulting in a high level of integration with low parasitics. In comparison to other assembly techniques such as printed circuit boards, wire-bonding, flip-chip and interlaced processes, this Berkeley method is superior in that it: - Broadens the number of dissociated technologies that can be modularly integrated; - Minimizes parasitics through the use of integrated interconnects; - Offers higher throughput based on the batch process approach; - Saves on substrate area usage due to stacked high density integration; - Enables each modular fabrication to be dissociated and run in parallel. (more...)

Micromirror arrays represent a huge market opportunity in a variety of sectors from optical displays, scanners and communication switches, to maskless lithography and optical spectroscopy. In the conventional design of these arrays, mirrors are mounted on tiltable cantilevers. However, in high frequency and analog applications a phased-mirror approach would be more useful. In this design, mirrors are shifted perpendicular to plane of the array to produce an image by interference effects. Unfortunately, no practical solution has been proposed to fabricate an electrostatically actuated dense array of phase micromirrors of micrometer size. To address this problem, researchers at the University of California at Berkeley have developed a MEMS-based microactuator for phase micromirror arrays. This electrostatic microactuator supports a rigid micromirror that is compliant only in the vertical direction. The fundamental advantage of this Berkeley microactator is that it can be manufactured by conventional MEMS fabrication techniques using standard semiconductor patterning and thin-film deposition processes. This low voltage actuator is conducive to fabricating flat and dense mirror arrays -- which is highly desirable in optical systems. Moreover, the device limits the range of actuation to prevent snap-down, and also provides damping to suppress mirror vibration. (more...)