Active Semiconductor Devices Research Articles

Phase relaxation control in heterostructures featuring charge-transfer excitons

Type-II quantum well heterostructures are considered high-potential candidates for next-generation active semiconductor devices. They promise low fundamental transition energies and suppressed Auger scattering as well as temperature stability in device performance. Understanding their fundamental properties, such as scattering and diffusion, and revealing intricate differences from type-I quantum structures are important steps towards optimized structure design. Using degenerate four-wave mixing spectroscopy, we investigate the phase coherence of excitonic polarizations in a (Ga,In)As/GaAs/Ga(As,Sb) type-II double-quantum-well structure. It is designed to exhibit spectrally isolated resonances in its linear absorption spectrum including a well-resolved charge-transfer exciton resonance. This allows us to study the coherent dynamics of the unperturbed charge-transfer exciton polarization. In addition, the effects of many-body interactions with free charge carriers as well as excitons that are injected by an optical prepulse are revealed. Scattering of charge-transfer excitons with free charge carriers is three times more efficient than scattering of charge-transfer excitons with each other. The comparison with Wannier excitons in a type-I quantum well structure shows that the interaction strength between charge-transfer excitons is about twice as large as for excitons in a type-I quantum well structure.

Time-Varying Radiation Impedance of Microcontroller GPIO Ports and Their Dependence on Software Instructions

The coupling of short wavelength electromagnetic (EM) interference to critical electronic systems in highly reverberant enclosures is a growing concern in the EM interference/compatibility community. In such highly reverberant cavities, prior research has shown that the induced EM fields, voltages, or currents can be modeled using the wave-chaotic random coupling model (RCM). The RCM partitions the interaction within the cavity into a universally fluctuating part, derived from random matrix theory, and a system-specific part, defined by the radiation impedance of the ports of interest, where the voltages or currents are induced. Earlier researchers have treated the radiation impedance as a time-invariant, frequency-dependent complex quantity. This is true for passive structures but is not true for active semiconductor devices, such as microcontrollers, which can exhibit time-varying radiation properties depending on the instruction cycle being executed at a given instant of time. The estimate of such a time-varying radiation impedance and its correlation with instruction cycles in an elemental microcontroller is the focus of this work. Utilizing clustering algorithms, we observe that the measured radiation impedance, as well as radiative emissions, are correlated to the class of instruction cycles being executed. By clustering the radiation impedance and emissions of the general-purpose input/output ports utilizing the class of instructions being executed, predictive models for microcontroller susceptibility can be derived even when detailed knowledge of the specific instruction cycle being executed is unknown a priori. Such a predictive capability can find multiple applications in the EMI/EMC community.

Light-field-driven electronics in the mid-infrared regime: Schottky rectification.

The speed of an active electronic semiconductor device is limited by RC timescale, i.e., the time required for its charging and discharging. To circumvent this ubiquitous limitation of conventional electronics, we investigate diodes under intense mid-infrared light-field pulses. We choose epitaxial graphene on silicon carbide as a metal/semiconductor pair, acting as an ultrarobust and almost-transparent Schottky diode. The usually dominant forward direction is suppressed, but a characteristic signal occurs in reverse bias. For its theoretical description, we consider tunneling through the light-field–modulated Schottky barrier, complemented by a dynamical accumulation correction. On the basis only of the DC parametrization of the diode, the model provides a consistent and accurate description of the experimentally observed infrared phenomena. This allows the conclusion that cycle-by-cycle dynamics determines rectification. As the chosen materials have proven capabilities for transistors, circuits, and even a full logic, we see a way to establish light-field-driven electronics with rapidly increasing functionality.

Unidirectional medium voltage rectifier utilizing sinusoidal input currents

Due to recent advances in the field of wide bandgap semiconductors, medium voltage converters are starting to regain momentum. This is mainly facilitated as SiC MOSFETs with blocking voltages of up to 10 kV and switching frequencies in the 10th of kilohertz range are starting to become commercially available. Therefore, a unidirectional three-phase medium voltage rectifier based on a diode bridge rectifier and active current injection network is proposed which benefits from a relatively low number of active semiconductor devices compared to already existing medium voltage solutions. Furthermore, sinusoidal mains currents can be achieved due to third harmonic injection techniques.

Enhanced exciton binding energy, Zeeman splitting and spin polarization in hybrid layered nanosheets comprised of (Cd, Mn)Se and nitrogen-doped graphene oxide: implication for semiconductor devices

The exciton properties of (Cd,Mn)Se-NrGO (nitrogen doped reduced graphene oxide) hybrid layered nanosheets have been studied in a magnetic field up to 10 T and compared to those of (Cd,Mn)Se nanosheets. The temperature dependent photoluminescence reveals the hybridization of inter-band exciton and intra-center Mn transition with enhancement of the binding energy of exciton-Mn hybridized state (80 meV with respect to 60 meV in (Cd,Mn)Se nanosheets) and increase of exciton—phonon coupling strength to 90 meV (with respect to 55 meV in (Cd,Mn)Se nanosheets). The circularly polarized magneto—photoluminescence at 2 K provides evidence for magnetic field induced exciton spin polarization and the realization of excitonic giant Zeeman splitting with g eff as high as 165.4 ± 10.3, much larger than in the case of (Cd,Mn)Se nanosheets (63.9 ± 6.6), promising for implementation in spin active semiconductor devices.

Analysis and Comparison of Hybrid-Resonant Switched-Capacitor DC–DC Converters With Passive Component Size Constraints

This article explores the merits of a variety of hybrid-resonant switched-capacitor (SC) dc–dc converters under strict size constraints on passive components (flying capacitors and inductors). Topologies are compared using a “minimum power loss” figure of merit (FOM) that captures conduction- and frequency-dependent losses in active semiconductor devices and losses related to passive components as they scale with size and relative voltage rating. Similar to past work on pure SC converters, the method leverages a charge-multiplier approach and is used to show the impact of area or volume constraints on inductors and capacitors. Building on past work, considerations for treating both “direct-” and “indirect-” conversion architectures are provided, as well as treatment of converters that require multiple inductors. Common topologies are compared using the generalized FOM under different scaling scenarios; general trends are validated using an experimental prototype.

Physics-Based Device Models and Progress Review for Active Piezoelectric Semiconductor Devices.

Piezoelectric devices transduce mechanical energy to electrical energy by elastic deformation, which distorts local dipoles in crystalline materials. Amongst electromechanical sensors, piezoelectric devices are advantageous because of their scalability, light weight, low power consumption, and readily built-in amplification and ability for multiplexing, which are essential for wearables, medical devices, and robotics. This paper reviews recent progress in active piezoelectric devices. We classify these piezoelectric devices according to the material dimensionality and present physics-based device models to describe and quantify the piezoelectric response for one-dimensional nanowires, emerging two-dimensional materials, and three-dimensional thin films. Different transduction mechanisms and state-of-the-art devices for each type of material are reviewed. Perspectives on the future applications of active piezoelectric devices are discussed.

Low-loss tunable dielectrics for millimeter-wave phase shifter: from material modelling to device prototyping

Passively controllable millimeter-wave phase shifters based on continuously tunable dielectrics offer promising alternatives to conventional switch-based topologies (e.g. active semiconductor devices and MEMS) with digital resolution. However, only a handful of tunable dielectrics have thus far been identified with high tunability and low loss, among them, liquid crystal (LC) in the nematic phase is of research and development interest. This work presents the modelling of LC materials at 66 GHz based on a novel shielded coplanar device structure in place of traditional waveguides. Phase shifters of 0-π tunability are fabricated and measured, with an insertion loss of -4 dB and return loss lower than -15 dB demonstrated.

Simple Interface Modification of Electroactive Polymer Film Electrodes.

Understanding the role of interface properties is crucial in the search for alternative design strategies to optimize the efficiency, performance, and lifetime of both solid-state and redox active organic semiconductor devices. Recent advances have focused on controlling and tailoring interfacial effects on the morphology and molecular structure of the active film in multilayer devices triggering new developments in the area of interface engineering. Here, we demonstrate that an inorganic electrode/organic semiconductor interface modification using PEDOT:PSS as an interfacial material influences the charge and ion transport, capacitive, morphological, and color switching properties of a solution processed purple-to-clear switching electrochromic PProDOT-(CH2OEtHx)2 polymer film. We find that the barrier to charge transport from electrode to active material is lowered when adding this PEDOT:PSS film, allowing us to present a fully roll-to-roll compatible, simple, and versatile battery-type electrochromic device (ECD) design without the need for oxidizing the charge storage film, in combination with improved processing reproducibility. In addition to producing ECDs with minimal color differences compared to devices prepared in the more traditional and complicated manner, this new ECD design strategy provides competitive performance showing a consistent optical contrast of 50-55% and switching times of 2-4 s.

Coherent light matter interactions in nanostructure based active semiconductor waveguides operating at room temperature

Light matter coherent interactions require that the coherent state induced in the matter be maintained for the duration of the observation. The only way to induce and observe such interactions in room temperature semiconductors, where the coherence time is of the order of a few hundred femtoseconds, is to use ultrashort pulse excitations and an ultrafast characterization technique. For media comprising an ensemble of nanostructure semiconductors such as self-assembled quantum dots, the gain broadening inhomogeneity also affects the interaction. Moreover, when gain media in the form of an active waveguide, such as optical amplifiers, are used, the interaction is distributed and includes nonresonant incoherent phenomena that occur simultaneously with the coherent effects. Such a complex system can exhibit, nevertheless, clear coherent interactions even at room temperature. Using InAs/InP quantum dot and wirelike quantum dash amplifiers, Rabi oscillations, self-induced transparency, coherent control using spectral pulse shaping, Ramsey interference, and photon echo have been demonstrated. The characterization employed cross frequency resolved optical gating, and the experiments were accompanied by a comprehensive finite difference time domain model that solves the Maxwell and Lindblad equations. This work has major implications on the understanding of the details of dynamical processes in active semiconductor devices, on short pulse generation from semiconductor lasers, and on various future quantum devices.

Auxiliary Power Supply for Medium-Voltage Power Converters: Topology and Control

This paper presents an isolated auxiliary power supply for medium-voltage power electronics systems. The proposed converter comprises two stages: a non-isolated ac/dc stage that connects directly to the medium-voltage line, and an isolated dc/dc stage that provides 100-W output power at 24 V, with 10 kV isolation. The proposed modular ac/dc stage uses just one active semiconductor device per module, features an internal capacitor voltage balancing, and achieves power factor correction by employing predictive current control. High switching frequency operation of both converter stages enable a reduction in system size and weight when compared to traditional low-frequency transformer-based approach. The proposed converter is simulated and its operation is validated experimentally on a 100-W prototype.

3-D Printed Parts for a Multilayer Phased Array Antenna System

In this work, a three-dimensional printable multilayer phased array system was designed to demonstrate the applicability of additive manufacturing for radio frequency (RF) systems. A hybrid process incorporating a thermal wire-mesh embedding method for conductors and thermoplastic material extrusion for dielectrics is employed. The designed phased array, operating at 3.5 GHz, consists of three functional layers: a 1-to-4 Wilkinson divider at the bottom, embedded voltage-controlled phase shifters at the center, and patch antennas on the top. Standalone parts of the proposed multilayer phased array were printed to verify the integrated dielectric-conductor printing process as well as the incorporation of active semiconductor devices at room temperature.

Design of reconfigurable frequency‐selective surfaces including the PIN diode threshold region

Reconfigurable frequency-selective surfaces (RFSSs) are of significant interest in applications, such as secure communication systems or tunable radomes, to improve indoor communication and smart antennas. In order to change the frequency-selective surface (FSS) characteristics, and therefore its frequency response, conventional methods include loading with active semiconductor devices such as varactors, PIN diodes, Schottky diodes and radio-frequency microelectromechanical system. Another possibility is the use of mechanical adjusts, such as spring resonators or mechanical rotation. When PIN diodes are used, commonly only the reverse and forward regions, OFF and ON states, respectively, are considered. In this study, the implementation of an RFSS is described, using PIN diodes as active components. The RFSS is based on the four-arms star geometry, and initial design equations and procedures are presented. Numerical and measured results are shown for different project stages, with a very good agreement. In addition to obtaining two distinct resonant frequencies, due to the OFF and ON states, a third situation is included, considering the PIN diode threshold region when the FSS becomes practically transparent, which is an interesting feature with potential applications.

High-performance near-field electroluminescent refrigeration device consisting of a GaAs light emitting diode and a Si photovoltaic cell

We consider a near-field electroluminescent refrigeration device. The device uses a GaAs light emitting diode as the cold side, and a Si photovoltaic cell as the hot side. The two sides are brought in close proximity to each other across a vacuum gap. The cooling is achieved by applying a positive bias on the GaAs light emitting diode. We show that the choice of GaAs and Si here can suppress the non-idealities for electroluminescent cooling purposes: GaAs has a wide bandgap with low Auger recombination, and Si is a non-polar semiconductor which leads to significantly reduced sub-bandgap heat transfer. We show that by using this configuration in the near-field regime, the cooling power density can reach 105 W/m2 even in the presence of realistic Auger recombination and Shockley-Read-Hall recombination. In addition, with photovoltaic power recovery from the Si cell, the efficiency of the device can be further improved. Our work points to the significant potential of combining near-field heat transfer with active semiconductor devices for the control of heat flow.

Extended High-Temperature Operation of Silicon Carbide CMOS Circuits for Venus Surface Application

In the last decade, significant effort has been expended toward the development of reliable, high-temperature integrated circuits. Designs based on a variety of active semiconductor devices including junction field-effect transistors and metal-oxide-semiconductor (MOS) field-effect transistors have been pursued and demonstrated. More recently, advances in low-power complementary MOS (CMOS) devices have enabled the development of highly integrated digital, analog, and mixed-signal integrated circuits. The results of elevated temperature testing (as high as 500°C) of several building block circuits for extended periods (up to 100 h) are presented. These designs, created using the Raytheon UK's HiTSiC® CMOS process, present the densest, lowest-power integrated circuit technology capable of operating at extreme temperatures for any period. Based on these results, Venus nominal temperature (470°C) transistor models and gate-level timing models were created using parasitic extracted simulations. The complete CMOS digital gate library is suitable for logic synthesis and lays the foundation for complex integrated circuits, such as a microcontroller. A 16-bit microcontroller, based on the OpenMSP 16-bit core, is demonstrated through physical design and simulation in SiC-CMOS, with an eye for Venus as well as terrestrial applications.

(Invited) Methods for Dynamic Analysis and Stability Assurance of Power Modules with Wide Bandgap Devices

This paper addresses the problems that have been widely reported with the dynamic behavior of application circuits using wide bandgap devices of both common semiconductor types, i.e., silicon carbide and gallium nitride. It is now common to see recommendations to the effect that advanced wide bandgap transistors need advanced packaging to realize reliable operation and expected benefits. This thinking is so prevalent that at least one manufacturer of GaN transistors does not supply their devices in packaging. While this is hardly the view of most manufacturers, it does highlight that wide bandgap transistors have succeeded so well in demonstrating new capabilities in high voltage, high current, and/or high frequency that the design methodology for integrating these devices into power electronics applications needs to be rethought. But what should this thinking be? Since fast switching is an essential part of the value of wide bandgap devices, it is imperative that the designers of high-power modules using these devices have modeling and simulation tools to manage the near RF dynamic behavior of the system in order to preclude instability and to manage electromagnetic emission. Fortunately, the well established rules of stability in electronic circuits should apply, but during analysis of power electronic applications they need to be augmented with model features omitted with silicon power semiconductors. But as a practical matter, the additions to the model need to be as simple as possible while achieving a level of confidence that a power module design containing SiC or GaN transistors integrated with a particular gate drive will perform with assurance of stability and with acceptable dynamics. An example of acceptable dynamics is compliance with electromagnetic interference certification requirements. But what are the means available? The current literature primarily addresses the issue quantitatively with what might be called the finite element method. This involves trying to experimentally measure or estimate through simulation the lumped element parasitics connecting all devices to each other and to drain, source, and gate buses leading to the external contacts of the power package and continuing to the gate drive. These parasitics are usually lumped series inductances and resistances, and shunt capacitances to surfaces of common potential so that common-mode interference can also be understood. This method has been shown to be successful in identifying the impedance-based mode changes from parasitic “ringing” to periodic oscillations. The former is considered to be a relatively unavoidable nuisance that dissipates the energy stored in parasitic components during ­one switching cycle of a commutated power pole. The latter is unacceptable as it converts energy from a main energy supply, such as the DC bus feeding a half-bridge circuit, into recurring oscillations. An impedance based method known as the concept of negative resistance oscillators is shown to be quantitatively successful at predicting the mode change from stable to unstable in a circuit with a single discrete device. But for the case of a multi-chip power package, with much greater complexity in the number of active semiconductor devices and the number of interconnections and shunt paths defining the parasitic degrees of freedom, a more systematic method is needed that is still behavioral in nature to keep the methodology computationally tractable. This paper describes a novel blend of the approaches used by two engineering communities that integrate power devices into application specific packaging. The impedance method of the lumped-element negative resistance oscillator representing the method of the power electronics engineering community is extended to the power package containing wide bandgap devices with the use of the S-parameter approach that dominates the microwave engineering community. A commercial simulation tool, such as ADS by Agilent, is shown to easily extract S-parameters of arbitrary package design using physics based modeling and simulation. The resulting comprehensive description of the parasitic properties of the power package captured by the multi-port S-parameter behavioral model is combined with the channel-modulation model of the transistors to form a negative resistance description of the root cause of poor dynamics and instability. The result is a new approach for specifying acceptable dynamic performance and stability assurance of multi-chip integrated power modules containing wide bandgap semiconductors.

Electrical Homo-Junction Delineation Techniques: A Comparative Study

In active semiconductor devices, the junction characteristics are critical for the electrical performance. As an alternative of the atomic force microscopy (AFM)-based electrical techniques which provide unique junction characterization, other methods are dedicated for the delineation of the electrical junction such as the wet chemical etching, the electrochemical plating method, the Seebeck effect imaging (SEI) method, the electron-beam induced current (EBIC) technique and the secondary electron potential contrast (SEPC) method. The aim of this paper is in the one hand to compare these five techniques in term of sample preparation, spatial application range, spatial resolution, simplicity and information displayed. In the other hand, this review aims to provide some guidelines for the appropriate delineation method(s) selection. It was confirmed that chemical based techniques are the simplest junction delineation methods but exhibit some drawbacks in term of spatial resolution and reproducibility. Despite of a limited spatial resolution, it was evidenced that EBIC can provide accurate electrical characterization of the junction. Finally, it was demonstrated that SEPC is the most promising technique providing the higher spatial resolution. The effect of the sample preparation method has been described. Even if the comparison was mainly based on homo-micro-Silicon junctions (n-p and n-p-n-p), the results were also discussed for short SiC junctions. The importance of the analysis context was considered in this paper and analysis flow was suggested for specific analysis cases.

High-Temperature Operation of Silicon Carbide CMOS Circuits for Venus Surface Application

Abstract In the last decade, significant effort has been expended towards the development of reliable, high-temperature integrated circuits. Designs based on a variety of active semiconductor devices including junction field effect transistors and metal-oxide-semiconductor field effect transistors have been pursued and demonstrated. More recently1,2, advances in low-power complementary MOS devices have enabled the development of highly-integrated digital, analog and mixed-signal integrated circuits. The results of elevated temperature testing (as high as 500°C) for extended periods (up to 100 hours) of several building block circuits will be presented. These designs, created using the Raytheon UK's HiTSiC® CMOS process, present the densest, lowest-power integrated circuit technology capable of operating at these extreme temperatures for any period of time. Based on these results, Venus nominal temperature (470°C) SPICE m°dels and gate-level timing models were created using parasitic extracted simulations. The complete CMOS digital gate library is suitable for logic synthesis and lays the foundation for complex integrated circuits, such as a microcontroller in SiC-CMOS, with an eye for Venus as well as terrestrial applications.

A Three Phase Based Four Switch Inverter for Renewable Energy Sources in Micro grid

Inverters designed using reduced active semiconductor devices can be of interest to the industry because of their lower cost and enhanced reliability linked to their less complex gating and control circuitries. In this paper a four switch three phase b-4 topology for the grid connected application in an effort to reduce the cost of the inverter is investigated. Admittedly, this topology warrants higher voltage ratings of the semiconductor devices used and the dc-link split capacitors used with respect to a conventional six-switch three-phase b-6 topology inverter for a specific set of grid voltages. In this paper, application of four power semiconductor switch based three phase inverter has been proposed for renewable energy based generalized three phase micro grid interconnection. The b-4 of three phase inverter topology is investigated to make the commercial micro grid system to be cost effective and hardware optimized. A simple sinusoidal pulse width modulation (SPWM) is used to control the switching of the four switches. Main advantage of this converter is that it needs only four switches. As a result the system is less costly and also the complexity in associated with gating and control circuitry is very much reduced

Towards 3D Integration of Monolithic X or Γ Ray Detectors Under Possible Electromagnetic Perturbations or Malfunctions

In this paper, X/Γ rays photodetectors are designed using a proposed set of CAD oriented tools. These tools are handled to study not only the device behavior, but also its possible drawbacks. First of all, we develop an efficient time-domain electromagnetic wave simulator for modeling a PiN diode in a micro-wave circuit. In fact, both the active semiconductor devices and passive interconnection domains are introduced. They combine accurate modeling of the transport phenomena in the diode and electromagnetic wave effects present around the device. A "leapfrog" algorithm of a 3-D FDTD method, the spurious waves coming from any direction, is used for the simulation of Si-PiN and CCD cells. This physical method is powerful as it can give, starting from microscopic phenomena, the scattering parameters, after some FFT’s, tools very useful for the engineers. The obtained results are in agreement with those from other commercial simulators and also in agreement with theoretical concepts. A 2D numerical simulation of space charge under X-ray irradiation, in a CdTe phodetector, is investigated. It provides important information on the distribution and the dynamics of the electric phenomena of the detector; it is the first time, up to our knowledge, that an electrical field-induced parasitic space charge is described with simulations. We think that some experiment, based on some linear electro-optic effect - Pockels effect - could confirm these results. This local charge collection properties can be also accessed by performing IR pulsed laser experiments. Finally, some fast transimpedance amplifier has been designed in a quarter micron technology. The architecture has been adapted to the characteristics of the technology through a careful optimization of the design, resulting in an extremely fast amplifier, with fall time near 1 ns at room temperature.