Commercial Schottky Research Articles

A DLTS analysis of alpha particle irradiated commercial 4H-SiC Schottky barrier diodes

4H-SiC Schottky barrier diodes (SBDs) were exposed to 5.4 MeV alpha particles with fluences of 2.55× 1011 cm−2, 5.11 × 1011 cm−2 and 7.67 × 1011 cm−2, respectively. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) was used to determine the structure and cross-sectional elemental composition of the device, while current–voltage and capacitance–voltage profiling were used to determine the primary electrical device-characteristics before and after irradiation. EDS revealed the presence of a <1 μm Ti layer, covered by 5 μm Al layer, in intimate contact with the SiC. Deep level transient spectroscopy (DLTS), performed in the temperature range 15–310 K, revealed one dominant peak around 50 K (Ec - 0.07 eV) in the unirradiated samples. This peak showed asymmetry suggesting that it may consist of more than one defect. Notably, Z1/2, the carbon vacancy-related (Vc) defect commonly observed in as-grown n-type 4H-SiC, was not detected in the unirradiated reference sample. After irradiation, a broad peak emerged around 280 K (at 80 Hz), most likely Z1/2, having a shoulder around 180 K, was detected. Increasing the fluence resulted in a corresponding decrease in the concentration of the electron trap observed around 50 K (Ec - 0.07 eV), while the concentration increases for the defect detected around 280 K. Notably, the concentration of Z1/2 was found to be strongly fluence dependent and linked to what we believe is a related to a silicon vacancy transition, labelled S1/2 in literature. Laplace DLTS confirmed that the peak observed around 50 K is composed of multiple defects.

SPICE Simulation Assisted-Dynamic Rds(on) Characterization in 200V Commercial Schottky p-GaN HEMTs Under Unstable Phases

Abstract This paper presents a comprehensive analysis of dynamic and static RDS(ON) in Schottky p-GaN High Electron Mobility Transistors (HEMTs), highlighting the impact of off-state and hot electron trapping on device performance. The authors observed significant hysteresis in the transfer characteristics of a 200V commercial Schottky p-GaN, attributing this to charge trapping effects. A novel experimental setup, employing a multi-pulse test synchronous buck converter circuit with additional gate control and a clamping circuit, enabled precise characterization of dynamic RDS(ON) under varying conditions, including unstable phases with overcurrent. This method effectively mimics solar PV input scenarios, exposing the device to high dv/dt and di/dt stresses, which are critical for evaluating GaN device stability under transient conditions. This research also reveals that increased gate resistance reduces energy losses, challenging traditional expectations by demonstrating the nuanced gate charge dynamics of GaN HEMTs. This study overall contributes to the understanding of GaN device behavior, offering a novel approach for accurately characterizing dynamic RDS(ON) under unstable stages, furtherly advances the GaN device in complex renewable energy power converter applications.

The effect of wafer thinning and thermal capacitance on chip temperature of SiC Schottky diodes during surge currents

Due to superior material properties of SiC for high-voltage devices, SiC Schottky diodes are used in energy-conversion systems such as solar-cell inverters, battery chargers, and power modules for electric cars and unmanned aerial vehicles. The reliable operation of these systems requires the chip temperature of SiC Schottky diodes to be maintained within the limit set by the device package. This is especially crucial during surge-current events that dissipate heat within the device. As a thermal-management method, manufactures of commercial SiC Schottky diodes have introduced wafer thinning practices to reduce the thickness of the SiC chip and, consequently, to reduce its thermal resistance. However, this also leads to a reduction in the thermal capacitance. In this paper, we present experimental data and theoretical analysis to demonstrate that the reduced thermal capacitance has a much larger adverse effect in comparison to the beneficial reduction of the thermal resistance. An implication of the presented results is that, contrary to the adopted wafer thinning practices, SiC Schottky diodes fabricated without wafer thinning have superior surge-current capability.

Investigation of temperature and flux effects on heavy ion induced degradation in SiC Schottky diode

In this work, the effects of environmental temperature and ion flux on heavy-ion irradiation damage in commercial SiC Schottky diodes were experimentally characterized. The result shows that the room temperature (25 °C) irradiation is the worst setting than high temperatures. In particular, the reverse leakage current IR increment at the highest temperature (150 °C) is about one-fifth of that at room temperature. The damage is more serious under high flux irradiation, and the IR increment introduced by higher flux (∼10,000 ions/(cm2∙s)) is four times larger than that by lower flux (∼300 ions/(cm2∙s)). After room temperature annealing for more than one year, the DUTs still show the same damage characteristics, which indicates the degradation damage induced by heavy ions is permanent. The variation of power dissipation induced by the synergistic effect of heavy ion incident and the electric field is the root mechanism. The results would help estimate the feasibility of the usage of SiC power devices in space.

Comparison of the effects of continuous and intermittent electron irradiation on commercial 4H-SiC Schottky barrier diodes

The radiation hardness of commercial 4H-SiC Schottky barrier diodes (STPSC1006D) has been investigated in this study. Primarily, intermittent irradiation at 0.5 Hz and continuous irradiation were analyzed and compared. Current–voltage (I–V), capacitance–voltage transform deep-level transient spectroscopy (FT-DLTS) were used to characterize the devices before and after irradiation. The devices show stability in their I–V characteristics upon irradiation. The free carrier concentration of the devices obtained from the C–V results decreased with the increasing of electron fluence. Additionally, new defects were observed after irradiation, which was the reason for the degradation in the electrical properties of the devices. The comparison of the devices irradiated intermittently and those irradiated continuous reveals that intermittent irradiation causes greater changes in electrical properties than continuous irradiation. These characteristics show the impact of STPSC1006D in space applications.

A Harmonic Radar Tag With High Detection Range Utilizing Ge FinFETs CMOS Technology

This study fabricated and verified a germanium (Ge) fin field-effect transistor (FinFET) on developed GeSOI platform. The Ge FinFETs were demonstrated for radio-frequency (RF) applications with a harmonic radar tag. The relation between the detection range (Rd), received power (Pr), and threshold voltage (Vth) of a diode was qualitatively discussed. To meet the requirement of a low Vth, two kinds of Ge FinFETs with different metal gates were fabricated and compared. After the evaluation of electrical characteristics of n-type and p-type Ge FinFETs with different fin numbers, a tag for harmonic radar was designed by integrating diode-connected TiN gate 1-fin Ge FinFETs (Vth = 0.1 V) with a high impedance antenna. The RF performance was evaluated at 9.4 GHz and 18.8 GHz. The results indicated a 50 % improvement in the Rd as compared to the tag using a commercial Schottky diode. Therefore, the proposed low-Vth Ge FinFET on developed GeSOI platform for complementary metal–oxide–semiconductor (CMOS) is promising for high-sensitivity harmonic radar applications.

Non Ideal Schottky Barrier Diode’s Parameters Extraction and Materials Identification from Dark &amp;lt;i&amp;gt;I-V-T&amp;lt;/i&amp;gt; Characteristics

Several parameters of a commercial Si-based Schottky barrier diode (SBD) with unknown metal material and semiconductor-type have been investigated in this work from dark forward and reverse I-V characteristics in the temperature (T) range of [274.5 K - 366.5 K]. Those parameters include the reverse saturation current (Is), the ideality factor (n), the series and the shunt resistances (Rs and Rsh), the effective and the zero bias barrier heights (ΦB and ΦB0), the product of the electrical active area (A) and the effective Richardson constant (A**), the built-in potential (Vbi), together with the semiconductor doping concentration (NA or ND). Some of them have been extracted by using two or three different methods. The main features of each approach have been clearly stated. From one parameter to another, results have been discussed in terms of structure performance, comparison on one another when extracted from different methods, accordance or discordance with data from other works, and parameter’s temperature or voltage dependence. A comparison of results on ΦB, ΦB0, n and NA or ND parameters with some available data in literature for the same parameters, has especially led to clear propositions on the identity of the analyzed SBD’s metal and semiconductor-type.

(Invited) How to Achieve Low Thermal Resistance and High Electrothermal Ruggedness in Ga2O3 Devices?

Ultra-wide bandgap gallium oxide (Ga2O3) devices have recently emerged as promising candidates for power and RF electronics. The low thermal conductivity of Ga2O3 has arguably been the most serious concern for these devices. Despite many simulation studies, there still lacks an experimental report on the thermal resistance and electrothermal ruggedness of a large-area, packaged Ga2O3 device. Recently, our team for the first time demonstrated large-area Ga2O3 devices with different packaging configurations and measured the thermal resistance and surge current capabilities of these packaged Ga2O3 devices. This paper reviews the key results in our efforts. It is shown that, contrary to some popular belief, Ga2O3 devices with proper packaging can achieve high thermal performance in both short transients and the steady state. The double-side-packaged Ga2O3 Schottky rectifiers show a junction-to-case thermal resistance lower than that of the similarly-rated commercial SiC Schottky rectifiers. In addition, these Ga2O3 rectifiers can survive a higher peak surge current as compared to SiC rectifiers. The critical enabler for these excellent performances is the direct junction cooling with minimal heat going through the Ga2O3 chip. Our work proves the viability of Ga2O3 devices for high power applications and manifests the significance of packaging for their die-level thermal management.

The impact of parasitic inductance on the dV/dt ruggedness of 4H-SiC Schottky diodes

In this study, the dV/dt ruggedness of commercial 4H-SiC Schottky diodes C3D02060A (Wolfspeed) with DC blocking voltage of 600 V and continuous forward current of 2 A was investigated. The quasi-static reverse current-voltage characteristics of the diodes were measured in the recoverable avalanche breakdown regime up to currents of about 7 A. The mature avalanche breakdown voltage was measured to be 1180 V which is almost twice the rated blocking voltage of 600 V. The dV/dt tests were performed with the use of a pulse current generator capable of generating short (3 ns), high-current (up to 80 A), high-voltage (up to 4 kV at 50-ohm load) pulses. The dV/dt limit was found to be 1260 V/ns, in combination with the value of diode terminal voltage of 750 V. Based on TCAD simulations, the impact of unavoidable lead inductance of TO-220A package on the dV/dt limit is pointed out. It is shown that a high voltage is induced on semiconductor structure being higher than the voltage on diode external terminals. As a result, diode failure occurs, although the diode terminal voltage is significantly lower than the mature avalanche breakdown voltage of semiconductor structure.

Magnetostatically Induced Easy-Cone Magnetic State Tuning by Perpendicular Magnetic Anisotropy in an Unbiased Spin-Torque Diode

We report the magnetostatically induced formation of an easy-cone magnetic state in free layers of magnetic tunneling junction (MTJ) with only first-order perpendicular magnetic anisotropy. By means of micromagnetic modeling, we study easy-cone angle dependence on the first-order anisotropy and its impact on the microwave sensitivity of the unbiased spin-torque diode. Considered magnetization tilt can be effectively engineered by choosing the ratio of the shape and first-order surface anisotropy, defined by the free layer's thickness, in-plane MTJ shape, and interlayer magnetostatic interactions. Through micromagnetic modeling over a broad range of input powers and free-layer thicknesses, we demonstrate a significant role of nonlinearity and inhomogeneous magnetization dynamics in achieving high sensitivity levels. Our modeling for typical state-of-the-art parameters of MTJ shows a possibility to reach a record-breaking unbiased sensitivity of 1100 mV/mW and 4650 mV/mW after impedance matching, which is far beyond the parameters of commercial Schottky diodes. These results will be very helpful for the development of efficient spintronic ambient energy harvesters.

Dual-Band Store-and-Use System for RF Energy Harvesting With Off-the-Shelf DC/DC Converters

RF energy harvesting (RFEH) has recently become part of the alternatives for powering wireless sensor networks. Our focus in this article was to introduce a design, MSwitch , able to use off-the-shelf dc/dc converters for running a real and self-powered Internet of Things (IoT) application. MSwitch is an RF dual-band energy harvesting stage employing the store-and-use principle that mixes efficiently and in a dynamic manner both inputs. We proved an increase on the performance with respect to the single-band case and to the most successful approaches found in the literature, achieving about 10 % better efficiency and around 35 % lower minimum power levels. Besides, we carried out an analysis of the commercial dc/dc converters, characterizing them for ultralow-power conditions. Likewise, we analyzed the state-of-the-art rectification circuits and commercial Schottky diodes, searching the best performance under our RFEH conditions. Finally, we manufactured our designs as a complete system and demonstrated its operation with an IoT concrete application.

Heavy ion radiation and temperature effects on SiC schottky barrier diode

The function of a commercial Schottky Barrier Diode (SBD) based on 4H-SiC in an environment of extreme temperature and radiation was assessed. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the devices were measured by heavy ions (HIs) irradiation at 3 different fluences and 15 different nodes of temperature. From these measurements, the effective carrier concentration (ND), reverse current (IR), series resistance (RS), ideal factor (n), and Schottky barrier height (SBH) were calculated and analyzed. Obvious increases of ND and IR were found and some changes of the electronic characteristics with temperature were enhanced by HIs. After the highest fluence of irradiation, the IR at low temperature (20 K) was even larger than the IR at room temperature, which was subjected to lower fluence of irradiation, suggesting risks for aerospace applications. These changes were attributed to defects both at the interface and in the body-substrate induced by irradiation.

Broadband Millimeter-Wave Textile-Based Flexible Rectenna for Wearable Energy Harvesting

Millimeter-wave (mmWave) bands, a key part of future 5G networks, represent a potential channel for RF energy harvesting, where the high-gain antenna arrays offer improved end-to-end efficiency compared with sub-6-GHz networks. This article presents a broadband mmWave rectenna, the first rectenna realized on a flexible textile substrate for wearable applications. The proposed novel antenna’s bandwidth extends from 23 to 40 GHz, with a minimum radiation efficiency of 67% up to 30 GHz, over 3-dB improvement compared with a standard patch. A stable gain of more than 8 dB is achieved based on a textile reflector plane. The antenna is directly connected to a textile-based microstrip voltage doubler rectifier utilizing commercial Schottky diodes. The rectifier is matched to the antenna using a tapered line feed for high-impedance matching, achieving broadband high voltage sensitivity. The rectifier has a peak RF–dc efficiency of 12% and a 9.5-dBm 1-V sensitivity from 23 to 24.25 GHz. The integrated rectenna is demonstrated with more than 1.3-V dc output from 12 dBm of mmWave wireless power across a 28% fractional bandwidth from 20 to 26.5 GHz, a 15% half-power fractional bandwidth, and a peak output of 6.5 V from 20 dBm at 24 GHz.

The evaluation of the current–voltage and capacitance–voltage-frequency measurements of Yb/p-Si Schottky diodes with a high zero-bias barrier height

The rare-earth metal Yb (Ytterbium) which has a very low work function of 2.60 eV has been shown to high quality Schottky contacts to p-Si. Two distinct linear regions in the semi-logarithmic current density–voltage plot are observed for Yb/p-Si Schottky diodes. From the linear regions, the very high zero-bias barrier height values are determined as 0.83 and 0.88 eV. The value of rectification ratio is in order of ~ 106 which is close to the commercial Schottky diodes. From Cheung functions, the value of series resistance is found to be 12.60 Ω. Furthermore, the important contact parameters of the diodes are calculated by using modified Norde method. The contact parameters obtained from reverse bias capacitance–voltage-frequency measurements do not show an important dependence on frequency. The calculated values of acceptor concentration are in close agreement with the value of doping concentration of the p-Si wafer used in this study.

The Correct Equation for the Current Through Voltage-Dependent Capacitors

Two different equations for the current through voltage-dependent capacitances are used in the literature. One equation is obtained from the time derivative of charge that is considered as capacitance–voltage product: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it dQ/dt=d[C(V)V]/dt=C(V)[dV/dt]+V[dC(V)/dt].}$ </tex-math></inline-formula> In the second equation, the term <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it V[dC(V)/dt]}$ </tex-math></inline-formula> does not exist: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it dQ/dt=} {\it C(V)[dV/dt]}$ </tex-math></inline-formula> . This paper clears the ongoing confusion caused by the difference between these two equations. We use the voltage-dependent parasitic capacitance of a commercial Schottky diode in reverse bias mode to test experimentally both equations. The result is that it is incorrect to add the term <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it V[dC(V)/dt]}$ </tex-math></inline-formula> in the first equation with the measured capacitance. We also perform a theoretical analysis, which shows that the differential capacitance, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it C(V)=dQ/dV}$ </tex-math></inline-formula> , in the correct current equation corresponds to the physical parameters of the diode capacitance.

Characterization of CdTe diode detector with depletion layer modulation for energy discrimination X-ray imaging

A new method of pseudo-energy discrimination X-ray imaging with conventional integration-type CdTe flat panel detectors is proposed. The energy selectivity of the detector can be controlled by modulating the thickness of the depletion layer with bias voltage. The analysis, considering the charge collection efficiency in the conventional commercial CdTe-based Schottky diode detector, was done to characterize the energy discrimination capability obtained by the developed method. The result has implied that the two energy bands as 30-60 keV and over 80 keV can be discriminated using two bias voltages. The Monte-Carlo simulation and the energy spectrum measurements with single pixel In/CdTe/Pt Schottky diode detectors were carried out to verify the pseudo-energy discrimination capability.

A Modular SiC-Based Step-Up Converter With Soft-Switching-Assisted Networks and Internally Coupled High-Voltage-Gain Modules for Wind Energy System With a Medium-Voltage DC-Grid

In this paper, a fully soft-switched silicon carbide (SiC)-based modular step-up resonant converter with magnetically integrated zero current switching voltage doublers is proposed for medium-voltage (MV) dc conversion in wind energy systems. Conventional step-up resonant dc/dc converters employ either high turns-ratio step-up transformer or step-up resonant circuits to achieve step-up voltage conversion. As a result, they require either complicated expensive transformer structure due to high-voltage electrical isolation requirement or highly voltage-gain sensitive step-up resonant circuits, which are not ideal for designing MV converters for wind energy application. In order to solve the aforementioned drawbacks, the proposed converter configuration utilizes both modular step-up resonant circuits and magnetically integrated voltage doublers to achieve the step-up voltage conversion function. The output voltage of each module of the dc/dc step-up converter is regulated through variable frequency control, whereas asymmetrical pulsewidth modulation (APWM) control is utilized to balance all the resonant currents in all the resonant circuit modules in each converter module. Since APWM control is used, a simple passive auxiliary circuit is included in each converter module to extend soft-switching operation over a wide range of operating conditions. Simulation results on a 1-kV/28-kV, 5-MW converter system with commercial 1.2-kV SiC MOSFET modules and experimental results on a laboratory-scale 300-V/4.8-kV, 5.6-kW proof-of-concept prototype with commercial SiC MOSFET and SiC Schottky diodes are provided to validate the theoretical analysis and to highlight the merits of the proposed work.

Experiment with Schottky junction: estimation of metal–semiconductor interface parameters

As far as diodes are concerned, a major breakthrough was achieved when Walter H. Schottky formed a metal–semiconductor junction, which is typically known as a Schottky diode. Its fast switching speed and low forward voltage, as well as its importance in direct current and microwave applications make the Schottky diode a more interesting electronic device. Due to its fundamental importance, study of the Schottky diode is essential for students at graduate/postgraduate levels. In the present work, a simple experiment is suggested to measure temperature-dependent current–voltage characteristics of the commercial Cu-Si Schottky diode. This enables the estimation of several fundamental parameters such as the (e/kB) ratio, Schottky barrier height (SBH) and the Richardson constant as well as the effective mass of electrons in a semiconductor.

A Physics-Based Compact Model of SiC Junction Barrier Schottky Diode for Circuit Simulation

A physics-based compact model of silicon carbide (SiC) junction barrier Schottky diode for circuit simulation is developed in this paper. The semiconductor physics mechanism in SiC, such as temperature-dependent mobility and incomplete ionization, are considered. The detailed device parameters, including drift region concentration, drift thickness, active area, and Schottky barrier height, are modeled. Then, a datasheet-oriented parameter extraction procedure for the device parameters is presented for three kinds of commercial SiC Schottky diodes with junction barrier structure. The model is implemented in the circuit simulator PSpice. In order to verify this model, the Technology Computer-Aided Design Sentaurus simulation is conducted with the device parameters and physical models, which shows a good agreement with the PSpice simulation.

Single Events Induced By Heavy Ions and Laser Pulses in Silicon Schottky Diodes

This paper is dedicated to the investigation of single-event effects (SEEs) in different types of silicon Schottky diodes using heavy ions and laser pulses. The objectives are both to progress in heavy ions and laser correlations using simple devices and to further understand the impact of optical and electrical parameters on photogeneration in Schottky diodes to contribute to the use of pulsed lasers for single-event sensitivity studies. Heavy ion test results on planar and trenched commercial Schottky diodes are presented. Based on these results, pulsed laser tests and transient measurements were performed on the sensitive devices. Destructive single events were evidenced with both techniques. Significant parameters of the laser tests, such as backside aperture of the device, electrical and optical configuration are discussed. These investigations show the potential of laser testing for Schottky diode SEE sensitivity study.