Photoconductive Switches Research Articles

Low On-Resistance and Ultrafast Rise Time Based on Vertical Diamond Photoconductive Switch with NPN Structure

Low On-Resistance and Ultrafast Rise Time Based on Vertical Diamond Photoconductive Switch with NPN Structure

Energy-efficient picosecond spin-orbit torque magnetization switching in ferro- and ferrimagnetic films.

Electrical current pulses can be used to manipulate magnetization efficiently via spin-orbit torques. Pulse durations as short as a few picoseconds have been used to switch the magnetization of ferromagnetic films, reaching the terahertz regime. However, little is known about the reversal mechanisms and energy requirements in the ultrafast switching regime. In this work we quantify the energy cost for magnetization reversal over seven orders of magnitude in pulse duration, in both ferromagnetic and ferrimagnetic samples, bridging quasi-static spintronics and femtomagnetism. To this end, we develop a method to stretch picosecond pulses generated by a photoconductive switch by an order of magnitude. Thereby we can create current pulses from picoseconds to durations approaching the pulse width available with commercial instruments. We show that the energy cost for spin-orbit torque switching decreases by more than an order of magnitude in all samples when the pulse duration enters the picosecond range. We project an energy cost of 9 fJ for a 100 × 100 nm2 ferrimagnetic device. Micromagnetic and macrospin simulations unveil a transition from a non-coherent to a coherent magnetization reversal with a strong modification of the magnetization dynamical trajectories as pulse duration is reduced. Our results show the potential for high-speed magnetic spin-orbit torque memories and highlight alternative magnetization reversal pathways at fast timescales.

Properties Investigation and Damage Analysis of GaN Photoconductive Semiconductor Switch Based on SiC Substrate.

The GaN photoconductive semiconductor switches (PCSSs) with low leakage current and large on-state current are suitable for several applications, including fast switching and high-power electromagnetic pulse equipment. This paper demonstrates a high-power GaN lateral PCSS device. An output peak current of 142.2 A is reached with an input voltage of 10.28 kV when the GaN lateral PCSS is intrinsically triggered. In addition, the method of retaining the AlGaN/GaN heterostructure between electrodes on PCSSs is proposed, which results in increasing the output peak current of the PCSS. The damage mechanism of the PCSS caused by a high electric field and high excitation laser energy is analyzed. The obtained results show that the high heat generated by the large current leads to the decomposition of GaN, and thus, the Ga forms a metal conductive path, resulting in the failure of the device.

Analysis of carrier dynamics and thermal effect of the GaAs photoconductive semiconductor switch in lock-on mode

Abstract The lock-on effect of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) at repetition rate aggravates the current crowding and electric field distortion, which significantly increases the risk of switch damage or even failure. Therefore, it is of great significance to investigate the carrier transport and the heat generation mechanism for improving the performance and longevity of GaAs PCSS in lock-on mode. The internal physical process of an opposed-electrode GaAs PCSS at low optical energy and strong electric field is analysed and discussed by experiment and simulation. A device-circuit hybrid simulation is employed to investigate the transient electric field, carrier concentration, and lattice temperature distribution within the GaAs PCSS in lock-on mode. The device temperature exhibits a positive correlation with the applied bias electric field, resulting in a peak temperature of 1037.25 K at an electric field of 38 kV/cm. The temperature distribution within the GaAs PCSS indicates a greater possibility for thermal breakdown and damage near the electrodes.

Enhanced Durability of High-Power Avalanche GaAs Photoconductive Semiconductor Switch Utilizing Advanced Double-Sided Cooling Configuration

Enhanced Durability of High-Power Avalanche GaAs Photoconductive Semiconductor Switch Utilizing Advanced Double-Sided Cooling Configuration

Physics-Based Artificial Neural Network Assisting in Extracting Transient Properties of Extrinsically Triggering Photoconductive Semiconductor Switches.

In this paper, a physics-based ANN assisting method for extracting transient properties of extrinsically triggering photoconductive semiconductor switches (ET-PCSSs) is proposed. It exploits the nonlinear mapping of ANN between transient current (input) and doping concentration (output). According to the basic laws of photoelectric device operating, two types of ANN models are constructed by gaussian and polynomial fitting. The mean absolute error (MAE) of forecasting transient photocurrent can be less than 10 A under low triggering optical powers, which verifies the feasibility of ANN assisting TCAD applied to PCSSs. The results are comparable to computation by Mixed-Mode simulation, yet even thousands of seconds of CPU runtime cost are saved in every period. To improve the robustness of the Poly-ANN predictor, Bayesian optimization (BO) is implemented for minimizing the curl deviation of photocurrent-time curves.

Asynchronous optical sampling of on-chip terahertz devices for real-time sensing and imaging applications

We demonstrate that asynchronous optical sampling (ASOPS) can be used to measure the propagation of terahertz (THz) bandwidth pulses in a coplanar waveguide device with integrated photoconductive switches used for signal excitation and detection. We assess the performance of the ASOPS technique as a function of measurement duration, showing the ability to acquire full THz time-domain traces at rates up to 100 Hz. We observe a peak dynamic range of 40 dB for the shortest measurement duration of 10 ms, increasing to 88 dB with a measurement time of 500 s. Our work opens a route to real-time video-rate imaging via modalities using scanned THz waveguides, as well as real-time THz sensing of small volume analytes; we benchmark our on-chip ASOPS measurements against previously published simulations of scanning THz sensor devices, demonstrating sufficient dynamic range to underpin future video-rate THz spectroscopy measurements with these devices.

High-voltage AlGaN/GaN heterojunction lateral photoconductive semiconductor switch based on semi-insulating 4H-SiC substrate

A novel high-power AlGaN/GaN heterojunction lateral photoconductive semiconductor switch (PCSS) based on the SiC substrate is proposed, which achieves high dark-state resistance characteristics by groove etching. Under the action of biased electric field and incident laser, a high concentration of two-dimensional electron gas is formed at the heterojunction interface. The photo-generated free carriers transport along the heterojunction interface, which improves the utilization efficiency of photo-generated carriers. Moreover, the simulation of the current density distribution of the PCSS provides theoretical support for this phenomenon. Compared with the conventional GaN PCSS, the power capacity and conduction characteristics are further improved. The test results show that the output current of the device increases significantly after the introduction of the AlGaN/GaN heterojunction. At the biased voltage of ∼34 kV, the maximum output current of the AlGaN/GaN PCSS reaches 205 A.

Reducing Dark-State Current for GaAs Photoconductive Semiconductor Switch by Ultrafine Grinding Process

Reducing Dark-State Current for GaAs Photoconductive Semiconductor Switch by Ultrafine Grinding Process

Dual-Stacked SiC Vertical Photoconductive Switch for Modulation Bandwidth Extension of Frequency-Agile Power Microwave

Dual-Stacked SiC Vertical Photoconductive Switch for Modulation Bandwidth Extension of Frequency-Agile Power Microwave

Fermi-Level Pinning in ErAs Nanoparticles Embedded in III-V Semiconductors.

Embedding rare-earth monopnictide nanoparticles into III-V semiconductors enables unique optical, electrical, and thermal properties for THz photoconductive switches, tunnel junctions, and thermoelectric devices. Despite the high structural quality and control over growth, particle size (<3 nm), and density, the underlying electronic structure of these nanocomposite materials has only been hypothesized. Structural and electronic properties of ErAs nanoparticles with different shapes and sizes (cubic to spherical, 1.14, 1.71, and 2.28 nm) in AlAs, GaAs, InAs, and their alloys are investigated using first-principles calculations, revealing that spherical nanoparticles have lower formation energies. For the lowest-energy nanoparticles, the Fermi level is pinned near midgap in GaAs and AlAs but resonant in the conduction band in InAs. The Fermi level is shifted down as the particle size increases and is pinned on an absolute energy scale considering the band alignment at AlAs/GaAs/InAs interfaces, offering insights into the rational design of these nanomaterials.

Effects of spot size on the operation mode of GaAs photoconductive semiconductor switch employing extrinsic photoconductivity

To guide the illuminating design to improve the on-state performances of gallium arsenide (GaAs) photoconductive semiconductor switch (PCSS), the effect of spot size on the operation mode of GaAs PCSS based on a semi-insulating wafer with a thickness of 1 mm, triggered by a 1064-nm extrinsic laser beam with the rectangular spot, has been investigated experimentally. It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes, and then significantly boosts the PCSS toward different operation modes. On this basis, a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms. Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching, while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching, which have been proved by comparing the domain evolutions under different spot sizes.

Capacitance Dependence of Carrier Transport in Nonlinear GaAs Photoconductive Semiconductor Switch at nJ Optical Excitation

Capacitance Dependence of Carrier Transport in Nonlinear GaAs Photoconductive Semiconductor Switch at nJ Optical Excitation

Low ON-Resistance and High Peak Voltage Transmission Efficiency Based on High-Purity 4H-SiC Photoconductive Semiconductor Switch

Low ON-Resistance and High Peak Voltage Transmission Efficiency Based on High-Purity 4H-SiC Photoconductive Semiconductor Switch

Carrier Transport and Pulse Compression of an Opposed-Contact GaAs Photoconductive Switch at Low-Energy Optical Excitation

Carrier Transport and Pulse Compression of an Opposed-Contact GaAs Photoconductive Switch at Low-Energy Optical Excitation

Influence of optical grating on the triggering efficiency of VCSI silicon carbide photoconductive semiconductor switch

In this article, we present a new configuration of opposed-contact vanadium-compensation semi-insulating (VCSI) 4H–SiC photoconductive semiconductor switch (PCSS) to reduce the input laser energy for operation. The configuration is made up of three parts: the PCSS with optical grating, the convex lens in front of PCSS, and the additional reflector behind PCSS. Periodic surface structures were fabricated on the VCSI 4H–SiC substrate by ultrafine femtosecond laser direct writing to etch optical gratings. The microstructure on the lower surface plays the role of reflection grating, so that the laser forms a specific distribution pattern and enhances the laser absorption. Experiments and simulations show that the triggering efficiency increased 3.7 times compared to PCSS without grating at 532 nm laser. And output voltage can reach 90 % of the input bias voltage. This SiC PCSS optical system significantly reduces the laser energy without reducing the electrodes spacing.

Comparison of photoconductive semiconductor switch parameters with selected switch devices in power systems

Comparison of photoconductive semiconductor switch parameters with selected switch devices in power systems

Switching jitter of avalanche gallium arsenide photoconductive semiconductor switch influenced by multiple avalanche domains.

The stability of synchronous operation is directly related to the time jitter of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS). In this work, a numerical model for the switching jitter of avalanche GaAs PCSS is established, and the impacts of triggering optical energy and bias electric field on the switching jitter are investigated numerically based on an equivalent bulk current channel. The proposed numerical model predicts well the changing characteristics of switching time as well as switching jitter, which has been demonstrated by the experimental results. On this basis, the theory of multiple avalanche domains is introduced to compare the domain evolutions influenced by the bias electric field and triggering optical energy. The results indicate that the reduction of switching jitter is significantly determined by the accelerated formation and evolution of avalanche domains, which provides a good explanation of the jitter mechanism of switching time.

Fiber-Induced Optical Reflective Cavity in a High-Voltage SiC Photoconductive Switch to Improve Photoelectric Responsivity

Fiber-Induced Optical Reflective Cavity in a High-Voltage SiC Photoconductive Switch to Improve Photoelectric Responsivity

Investigating the Performance of a Lateral 4H-SiC Photoconductive Switch With a Sinking-Electrode Structure

Investigating the Performance of a Lateral 4H-SiC Photoconductive Switch With a Sinking-Electrode Structure