Quantum Computation with Ballistic Electrons

We describe a solid state implementation of a quantum computer using ballistic single electrons as flying qubits in 1D nanowires. We show how to implement all the steps required for universal quantum computation: preparation of the initial state, measurement of the final state and a universal set of quantum gates. An important advantage of this model is the fact that we do not need ultrafast optoelectronics for gate operations. We use cold programming (or pre-programming), i.e., the gates are set before launching the electrons; all programming can be done using static electric fields only.Comment: 5 pages, RevTeX4, 5 figures, uses epsf, latexsym, time

Towards Integrated Mid-Infrared Gas Sensors.

Optical gas sensors play an increasingly important role in many applications. Sensing techniques based on mid-infrared absorption spectroscopy offer excellent stability, selectivity and sensitivity, for numerous possibilities expected for sensors integrated into mobile and wearable devices. Here we review recent progress towards the miniaturization and integration of optical gas sensors, with a focus on low-cost and low-power consumption devices

Material selection for optimum design of MEMS pressure sensors

Abstract: Choice of the most suitable material out of the universe of engineering materials available to the designers is a complex task. It often requires a compromise, involving conflicts between different design objectives. Materials selection for optimum design of a Micro-Electro-Mechanical-Systems (MEMS) pressure sensor is one such case. For optimum performance, simultaneous maximization of deflection of a MEMS pressure sensor diaphragm and maximization of its resonance frequency are two key but totally conflicting requirements. Another limitation in material selection of MEMS/Microsystems is the lack of availability of data containing accurate micro-scale properties of MEMS materials. This paper therefore, presents a material selection case study addressing these two challenges in optimum design of MEMS pressure sensors, individually as well as simultaneously, using Ashby’s method. First, data pertaining to micro-scale properties of MEMS materials has been consolidated and then the Performance and Material Indices that address the MEMS pressure sensor’s conflicting design requirements are formulated. Subsequently, by using the micro-scale materials properties data, candidate materials for optimum performance of MEMS pressure sensors have been determined. Manufacturability of pressure sensor diaphragm using the candidate materials, pointed out by this study, has been discussed with reference to the reported devices. Supported by the previous literature, our analysis re-emphasizes that silicon with 110 crystal orientation [Si (110)], which has been extensively used in a number of micro-scale devices and applications, is also a promising material for MEMS pressure sensor diaphragm. This paper hence identifies an unexplored opportunity to use Si (110) diaphragm to improve the performance of diaphragm based MEMS pressure sensors

Operation of Ultra-High Voltage (>10kV) SiC IGBTs at Elevated Temperatures:Benefits & Constraints

State of the art TCAD simulation models are used to simulate the performance of ultra-high voltage (10-20 kV) SiC IGBTs in the temperature range 300-775 K. We show that unlike Si-based counterparts, ultra-high voltage SiC IGBTs stand to gain from the temperature rise if the limit is not exceeded. We show that whilst an operation at 375 K is highly promising to achieve the most optimum on-state characteristics from SiC IGBTs, no significant degradation in the on-state current and breakdown voltage alongside with negligible rise in leakage current is observed until 550 K. Therefore, ≥10 kV SiC IGBTs are highly promising for Smart Grid and HVDC

Diamond power devices: State of the art, modelling and figures of merit

With its remarkable electro-thermal properties such as the highest known thermal conductivity (~22W/cmbold dotK at room temperature) of any material, high hole mobility (> 2000cm2/Vbold dots), high critical electric field (>10MV/cm), and large bandgap (5.47eV), diamond has overwhelming advantages over silicon and other wide bandgap semiconductors (WBG) for ultra-high- voltage and high temperature applications (>3kV and >450 K, respectively). However, despite their tremendous potential, fabricated devices based on this material have not delivered yet the expected high-performance. The main reason behind this is the absence of shallow donor and acceptor species. The second reason is the lack of consistent physical models and design approaches specific to diamond-based devices that could significantly accelerate their development. The third reason is that the best performances of diamond devices are expected only when the highest electric field in reverse bias can be achieved, something that has not been widely obtained yet. In this context, high temperature operation and unique device structures based on the 2DHG formation represent two alternatives which could alleviate the issue of the incomplete ionization of dopant species. Nevertheless, ultra-high temperature operations and device parallelization could result in severe thermal management issues and affect the overall stability and long-term reliability. Additionally, problems connected to the reproducibility and the long-term stability of 2DHG based-devices still need to be resolved. This review paper aims at addressing these issues by providing the power device research community with a detailed set of physical models, device designs and challenges associated to all the aspects of the diamond power device value chain, from the definition of figures of merits, the material growth and processing conditions, to packaging solutions and targeted applications. Finally, the paper will conclude with suggestions on how to design power converters with diamond devices and will provide the roadmap of diamond devices development for power electronics.This work was supported by the U.K. Engineering and Physical Sciences Research Council for the University of Cambridge Centre for Doctoral Training under Grant EP/M506485/1 and by the French ANR Research Agency under grant ANR-16-CE05-0023 #Diamond-HVDC. The research leading to these results has been performed within the GREENDIAMOND project and received funding from the European Community's Horizon 2020 Programme (H2020/2014–2020) under grant agreement no. 640947

Smart CMOS mid-infrared sensor array.

We present a novel single-chip thermopile sensor array for mid-infrared room temperature imaging. The array is fabricated on a single complementary metal-oxide-semiconductor (CMOS) dielectric membrane, composed of single-crystal silicon (Si) p+ and n+ elements, and standard CMOS tungsten metal layers for thermopile cold junction heatsinking, significantly reducing the chip size and simplifying its processing. We demonstrate a 16×16 pixel device with 34 V/W responsivity and enhanced optical absorption in the 8-14 μm waveband, with a suitable performance for gesture recognition and people-counting applications. Our simple, low-cost sensor is an attractive on-chip array for a variety of applications in the mid-infrared spectral region

Retrograde p-well for 10kV-class SiC IGBTs

In this paper, we propose the use of a retrograde doping profile for the p-well for ultrahigh voltage (>10 kV) SiC IGBTs. We show that the retrograde p-well effectively addresses the punchthrough issue, whereas offering a robust control over the gate threshold voltage. Both the punchthrough elimination and the gate threshold voltage control are crucial to high-voltage vertical IGBT architectures and are determined by the limits on the doping concentration and the depth that a conventional p-well implant can have. Without any punchthrough, a 10-kV SiC IGBT consisting of retrograde p-well yields gate threshold voltages in the range of 6-7 V with a gate oxide thickness of 100 nm. Gate oxide thickness is typically restricted to 50-60 nm in SiC IGBTs if a conventional p-well with 1×10 17 cm -3 is utilized. We further show that the optimized retrograde p-well offers the most optimum switching performance. We propose that such an effective retrograde p-well, which requires low-energy shallow implants and thus key to minimize processing challenges and device development cost, is highly promising for the ultrahigh-voltage (>10 kV) SiC IGBT technology

A low-power, low-cost infra-red emitter in CMOS technology

In this paper, 1 we present the design and characterization of a low-power low-cost infra-red emitter based on a tungsten micro-hotplate fabricated in a commercial 1-μm SOI-CMOS technology. The device has a 250-μm diameter resistive heater inside a 600-μm diameter thin dielectric membrane. We first present electro-thermal and optical device characterization, long term stability measurements, and then demonstrate its application as a gas sensor for a domestic boiler. The emitter has a dc power consumption of only 70 mW, a total emission of 0.8 mW across the 2.5–15-μm wavelength range, a 50% frequency modulation depth of 70 Hz, and excellent uniformity from device-to-device. We also compare two larger emitters (heater size of 600 and 1800 μm) made in the same technology that have a much higher infra-red emission, but at the detriment of higher power consumption. Finally, we demonstrate that carbon nanotubes can be used to significantly enhance the thermo-optical transduction efficiency of the emitter