High-voltage Diodes Research Articles

Исследование зависимости электрической мощности высоковольтного плазменного термоэмиссионного диода от теплофизических параметров итипа рабочего тела

Design and development of high-temperature current conversion systems based on the plasma power engineering devices, such as, for example, grid key elements and high-voltage plasma thermionic diodes (HPTD), is an urgent task and is connected to development of the high-power nuclear propulsion systems for spacecraft. The paper presents results of studying the HPTD specific electric power dependence on the thermophysical parameters of the interelectrode gap filler, i.e. on its temperature and pressure. Besides, dependence of the HPTD power was demonstrated on the materials used in the electrodes manufacture. HPTD specific electrical power dependences were obtained, as a function of temperature (anode and emitter) and vapor pressure of cesium and binary mixture. Expediency of using the HPTD binary filler with the tungsten emitter to increase its specific electric power was shown.

Modeling of High-Voltage Nonpunch-Through PIN Diode Snappy Reverse Recovery and Its Optimal Suppression Method Based on RC Snubber Circuit

The snappy reverse recovery (SRR) and failure of high-voltage nonpunch-through (NPT) PIN diodes under extreme working conditions are of great significance to the reliability evaluation of operating diodes in actual power electronic devices. In this article, the analysis of the physical mechanism of the diode SRR and the restrictions of the traditional PT-PIN diode model are made. Then, the traditional model for soft recovery is improved in order to accurately describe the diode SRR characteristics. Simulations of key dynamic performances of the established model agree well with the experimental results. Furthermore, a suppression method for diode SRR based on the optimal RC snubber circuit is proposed. A high-voltage NPT-PIN diode used in the dc−dc converter with different RC snubber circuits is simulated using the proposed diode snappy model and tested. The comparison results show good consistency between the simulated and measured voltage and current peaks and the diode SRR are suppressed effectively. The developed model and results are of much importance to the prediction of the safe operation area of the diode and to the reliability improvement of power electronic device.

On the breakdown voltage temperature dependence of high-voltage power diodes passivated with diamond-like carbon

Diamond-Like Carbon (DLC) is well established material for the passivation of high voltage negative bevelled power diode. In our previous works, the conduction mechanism of the DLC has been carefully described through the characterization and the physical modelling of Metal-Insulator-Semiconductor (MIS) structures. In addition, the effects on the breakdown voltage and leakage current have been clarified comparing the available experiments with numerical simulations. However, the role played by the DLC on the breakdown voltage temperature dependence is still lacking. In this work, we addressed the latter issue and found out an anomalous reduction of the temperature dependence which is clearly ascribed to the DLC behaviour. The temperature dependencies of carrier transport in the DLC have been further investigated in order to explain the experimental results. The observed effect might be related to the release of the trapped charges with increasing temperatures or to a different temperature dependence of the DLC mobility which is function of the distance from the Si/DLC interface. TCAD simulations are used to corroborate such assumptions.

Annealing High-Voltage 4H-SiC Schottky Diodes Irradiated with Electrons at a High Temperature

Annealing High-Voltage 4H-SiC Schottky Diodes Irradiated with Electrons at a High Temperature

Design and Performance of Ultraviolet 368-nm AlGaN-Based Flip-Chip High-Voltage LEDs with Epitaxial Indium Tin Oxide/Al Reflective Mirror and Symmetry Electrode Arrangement

In this letter, we describe the design and fabrication of high-power AlGaN-based ultraviolet (UV) flip-chip high-voltage light-emitting diodes (LEDs) operating at 368 nm with an epitaxial indium tin oxide (ITO)/Al reflecting mirror and symmetry electrode layout. Metal-organic chemical vapor deposition (MOCVD) was used to grow an ITO thin film as a transparent electrode on the LED surface. At 365 nm, epitaxial ITO thin films exhibited a transmittance of up to 93.6%. Additionally, the epitaxial ITO/Al reflective mirror has a reflectance of 81.2% at 365-nm. To investigate the electrical characteristics, four types of HV-LED micro-cells were constructed with varying n-type mesa structures and p-type interconnect electrodes. We demonstrated a forward voltage (Vf) of 7.86 V at 350 mA with a 2 × 2 mico-cells high-voltage ultraviolet 368-nm flip-chip LED after optimising electrode structure and device process.

Diamond semiconductor and elastic strain engineering

Diamond, as an ultra-wide bandgap semiconductor, has become a promising candidate for next-generation microelectronics and optoelectronics due to its numerous advantages over conventional semiconductors, including ultrahigh carrier mobility and thermal conductivity, low thermal expansion coefficient, and ultra-high breakdown voltage, etc. Despite these extraordinary properties, diamond also faces various challenges before being practically used in the semiconductor industry. This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes, high-power/high-frequency field-effect transistors, MEMS/NEMS, and devices operating at high temperatures. Following that, we will discuss recent developments to address scalable diamond device applications, emphasizing the synthesis of large-area, high-quality CVD diamond films and difficulties in diamond doping. Lastly, we show potential solutions to modulate diamond’s electronic properties by the “elastic strain engineering” strategy, which sheds light on the future development of diamond-based electronics, photonics and quantum systems.

Picosecond-range switching of high-voltage Si diode due to the delayed impact-ionization breakdown: Experiments vs simulations

The effect of delayed impact ionization breakdown initiated in a high-voltage Si or GaAs p+nn+ diode by a steep voltage ramp leads to 100 ps avalanche transient from the blocking to conducting state. Here, measurements of the voltage and current dependences in the Si diode exhibiting 100-ps kilovolt switching are presented together with simulations with focus on comparison. Device voltage and current are measured simultaneously and independently in a high-quality matched coaxial circuit. In simulations, we account for wave propagation and reflection processes in the coaxial driving/measuring circuit and for the inhomogeneity of the avalanche switching over the device cross section. This makes quantitative comparison with measurements possible. An agreement in switching time and transient characteristics can be achieved only under the assumption that a smaller part of the cross section is avalanching. The 100-ps switching time is formed not during the passage of superfast ionizing front in the “active” part of the device, as it is widely believed, but by the discharge time of the “passive part” over the conducting “active” part. The inner circuital current that flows within the device along the closed loop plays a dominant role in this process. Sources of initial carriers, the temperature dependence of the effect, and the limits of drift-diffusion transport model in describing the phenomenon of delayed breakdown are discussed.

The effect of maintaining a high conductivity state in high-voltage GaAs diodes switched-on in the delayed avalanche breakdown mode

It is experimentally established that high-voltage GaAs diodes maintain conducting state with low residual voltage after switching to the conducting state in the delayed impact-ionization mode. The duration of the constant current in the reversely-biased structure is determined by the duration of the applied rectangular voltage pulse (up to 100 ns) and significantly exceeds drift extraction and recombination times. The discovered effect of self-supporting conducting state resembles the "lock-on" effect in optically activated GaAs semiconductor switches and S-diodes with deep centers. The effect can be explained by shock ionization in narrow collapsing Gann domains. Keywords: high-voltage GaAs diodes, "lock-on" effect.

Коллапсирующие домены Ганна как механизм самоподдержания проводящего состояния в обратносмещенных высоковольтных GaAs-диодах

Switching of a high-voltage GaAs diode to the conducting state in the delayed impact-ionization mode is simulated and the results are compared with experimental data. It is shown that the effect of long-term (up to 100 ns) sustaining of the conducting state of the diode after switching is due to the appearance of narrow (of the order of a micrometer) ionizing Gunn domains, the so-called collapsing domains, in the electron-hole plasma. Impact ionization in collapsing domains and in the edge (cathode and anode) domains of a strong electric field (~300 kV/cm) maintains a high concentration of nonequilibrium carriers (≥1017 cm-3) during the entire duration of the applied reverse polarity voltage pulse.

Electron irradiation hardness of high-voltage 4H-SiC Schottky diodes in the operating temperature range

Effect of irradiation with 0.9 MeV electrons on the parameters of 4H-SiC Schottky diodes with a limiting blocking voltage Ub=600 and 1700 V was studied for the first time in the range of operating temperatures Ti (23 and 175oC). The range of fluences Phi was 1·1016-2·1016 cm-2 for devices with Ub=600 V and 5·1015-1.5·1016 cm-2 for devices with Ub=1700 V. Irradiation at room temperature increases significantly the differential resistance of the base of the diodes. Irradiation with the same doses at Ti=175oC --- i.e. at limiting operating temperature of devices, does not affect practically the parameters of current-voltage characteristics. Nevertheless, the DLTS spectra demonstrate a significant increase in the concentration of deep levels in the upper half of the band gap not only after irradiation at room temperature, but also after irradiation at Ti=175oC. Keywords: silicon carbide, Schottky diodes, electron irradiation, current-voltage characteristics, DLTS spectra.

Эффект самоподдержания проводящего состояния в обратносмещенных GaAs-диодах, переключаемых в режиме задержанного лавинного пробоя

It is experimentally established that high-voltage GaAs diodes maintain conducting state with low residual voltage after switching to the conducting state in the delayed impact-ionization mode. The duration of the constant current in the reversely-biased structure is determined by the duration of the applied rectangular voltage pulse (up to 100 ns) and significantly exceeds drift extraction and recombination times. The discovered effect of self-supporting conducting state resembles the lock-on effect in optically activated GaAs semiconductor switches and S-diodes with deep centers. The effect can be explained by shock ionization in narrow collapsing Gann domains.

Collapsing Gunn Domains as a Mechanism of Self-Supporting Conducting State in Reversely Biased High-Voltage GaAs Diodes

Switching of a high-voltage GaAs diode to the conducting state in the delayed impact-ionization mode is simulated and the results are compared with experimental data. It is shown that the effect of long-term (up to 100 ns) sustaining of the conducting state of the diode after switching is due to the appearance of narrow (of the order of a micrometer) ionizing Gunn domains, the so-called collapsing domains, in the electron-hole plasma. Impact ionization in collapsing domains and in the edge (cathode and anode) domains of a strong electric field (~ 300 kV/cm) maintains a high concentration of nonequilibrium carriers (≥ 1017 cm-3) during the entire duration of the applied reverse polarity voltage pulse. Keywords: high-voltage GaAs diodes, impact ionization, subnanosecond switches, Gunn effect, lock-on effect.

P-GaN field plate for low leakage current in lateral GaN Schottky barrier diodes

High-voltage gallium nitride Schottky barrier diodes (SBDs) suffer from large off-state leakage current, which further degrades during operation at high temperatures and limits the device blocking capabilities. The key to achieving low off-state leakage is to protect the Schottky barrier from the high electric field, which is challenging by employing conventional field plate structures due to their large pinch-off voltage. In this work, we propose a simple AlGaN/GaN SBD architecture based on a p-GaN cap layer to achieve excellent off-state performance with a very low leakage current. By properly designing the AlGaN barrier and p-GaN cap, the pinch off-voltage of the p-GaN field plate is carefully controlled and the voltage drop over the Schottky junction is effectively reduced. In addition, a large carrier concentration in the access region is achieved, leading to a reduced sheet resistance. This results in good on-state performance along with a very low leakage current of ∼1 nA/mm at 400 V, which is maintained well below 100 nA/mm up to elevated temperatures of 150 °C. Moreover, the proposed architecture shares the well-established fabrication process of commercial p-GaN HEMTs and, thus, represents a promising and viable solution for future GaN diodes.

Application of electro-hydraulic shock in concrete technology

The aspects, related to the influence of the electrohydraulic shock method use in a water-cement slurry passing in a closed chamber (activation reactor) with a pre-applied pressure to the system under various processing modes are highlighted in the article. In order to test the effect of this method on water-cement slurry, an installation was developed, consisting of: a high-voltage source, a high-voltage diode, capacitor banks, a closing element and an activation reactor. The necessary experiments were carried out on the completed installation. The procedure for conducting experiments is described in the work, shows a schematic diagram of the installation for performing activation, a diagram of the reactor, and the processing modes. Several activation modes were considered, depending on: the number of pulses (1-4), pulse energy (0.5-8 kJ), water-cement ratio (0.2-0.35), time intervals for starting treatment from the moment the cement was mixed with water (0 -120 minutes), volume and shape of the container (activation reactor), holding temperature (20-60°C), etc. According to the results of the data obtained, it was experimentally established that the use of electric pulse treatment of water-cement suspension has a positive effect on strength (cup compressive strength) indicators, obtained as a result of processing cement stone samples at different times of hardening (1-3 days). The compressive strength of the treated specimens’ increases in comparison with the untreated specimens, increase in strength reaches up to 45%, depending on the activation mode. The resulting effect was achieved due to many factors (high pressure, magnetic, temperature, energy, ultrasonic and other influences), which were applied in the most optimal period of time (stage) of the cement grain hydration process.

Metallization Reliability of GaN-Based High-Voltage Light-Emitting Diodes

Metallization Reliability of GaN-Based High-Voltage Light-Emitting Diodes

A High-Voltage High-Frequency Subnanosecond Pulse Generator Based on Gallium Arsenide Drift Step-Recovery Diodes

The prospect of using high-voltage GaAs drift step-recovery diodes for the formation of subnanosecond pulses is shown. The electrical circuit of a generator is described, which provides (with a total efficiency of at least 25%) the formation of pulses at a load of 50 Ω with an amplitude of up to 550 V, a voltage rise time of 0.43 ns, a full width at half maximum of 0.73 ns, and a repetition frequency of up to 200 kHz.

Wave Effects in a Coaxial Transmission Line under Subnanosecond Switching of a High-Voltage Diode in the Delayed Impact-Ionization Breakdown Mode

Wave Effects in a Coaxial Transmission Line under Subnanosecond Switching of a High-Voltage Diode in the Delayed Impact-Ionization Breakdown Mode

Simulation of High-Voltage Ion Diode with Wire Cathode at Atmospheric Pressure of Nitrogen

Physic-topological simulation of a high-voltage coaxial ion diode with a wire metal cathode at atmospheric nitrogen pressure in the hydrodynamic drift-diffusion approximation is performed. The reactions of nitrogen ionization by electrons, attachment of electrons to nitrogen molecules with the formation of negative ions, recombination of charged particles with opposite signs of charge, secondary ion-electron emission of the cathode were taken into account. The distribution of potential and density (concentration) of charged particles in the interelectrode gap, the density of ionic and electron currents at the electrodes were calculated within the self-consistent problem with the following parameters: diameter of wire metal cathode 0.01-0.16 mm, diameter of tubular anode 6 or 20 cm, voltage 20-40 kV, gas temperature 300 or 600K. The influence of geometry, voltage and gas temperature on the discharge parameters has been determined. The obtained calculated data on the discharge current are consistent with the experiment. It is shown that two zones are formed in the discharge between the electrode gap – one is with a width of about 1 mm with a strong and rapidly changing electric field near the cathode and the second long zone with the drift of charged particles towards the anode with a smaller but constant field strength. This is a characteristic feature of negative corona discharges. In the cathode zone there is an intensive ionization of nitrogen with the generation of positive ions and electrons. In the second zone, the density of positive ions decreases sharply due to recombination and weak ionization. The reaction of attachment of electrons to nitrogen molecules begins almost near the cathode surface and continues throughout the cathode zone, in the drift zone the concentration of negative ions gradually decreases. Moreover, the role of electronic conductivity is greatly reduced as we approach the anode. Due to the low mobility of negative ions and, accordingly, the high electrical resistance of the drift zone, the voltage drop on this space part represents a significant portion of the discharge voltage (~1.5 kV on the cathode zone and 18.5 kV on the drift space, at the total voltage of 20 kV). The fact that the highest concentration of positive ions is formed near the cathode, and negative – along the entire interelectrode gap, it can be used, respectively, in the processes of ionic nitriding of wire cathode metal materials and for processing materials and biological substances (bacteria, viruses, fungi), sensitive to negative ions, at the location of the carriers of these substances near the anode. To implement the latter, it is advisable to modify the design of the external anode for efficient extraction of nitrogen ions into the environment. It is also advisable to continue research in the direction of increasing the energy efficiency of ion generation by determining the method of the maximum allowable reduction of the voltage drop on the space of drift of charged particles.

Effect of high temperature irradiation with 15 MeV protons on characteristics of power SiC Schottky diodes

The effect of high-temperature irradiation with 15 MeV protons on the parameters of high-voltage 4H-SiC Schottky diodes has been studied at irradiation temperatures of 23–500 °C and doses in the range from 7 × 1013 to 2 × 1014 cm−2. After the irradiation with a dose of 1014 cm−2 at room temperature, the forward current at a forward voltage U = 2 V decreases by ~10 orders of magnitude. In this case, the cutoff voltage Uc, equal to ~0.6 V in unirradiated devices, decreases to Uc ≈ 0.35 V. By contrast, irradiation with the same dose at a temperature of 500 °C leads to an increase in Uc up to Uc ≈ 0.8 V. At the same reference value of the forward voltage U = 2 V, the decrease in current, compared to the value in unirradiated devices, was smaller by ~4 orders of magnitude. In the entire range of doses and irradiation temperatures under study, the forward current–voltage characteristic of diodes at U > Uc is linear up to U ≤ 2 V.

TCAD Investigation of Differently Doped DLC Passivation for Large-Area High-Power Diodes

An electroactive passivation for high-voltage diodes with bevel termination has been investigated based on diamondlike carbon (DLC) films. Variations of the DLC properties, i.e., conductivity and geometry, have been investigated by experiments and numerical simulations to the purpose of gaining an insight on their influence on the diode leakage current and breakdown voltage. The role played by the DLC/Si interface has been investigated by characterizing metal–DLC–Si devices. Both boron and nitrogen doping have been investigated, and a TCAD setup has been provided accounting for the main transport features of the DLC material with different doping configurations. A significant polarization effect has been observed in the DLC material, which improves the DLC performance as a passivation material. High-voltage diodes have been characterized and simulated with different DLC layers on top of the bevel termination in order to identify the role played by conductivity and polarization on the blocking state. The correlation of leakage current and voltage breakdown with the DLC doping and thickness is provided and explained by the TCAD simulation results.