Reverse Biased Diode Research Articles

Enhanced Threshold Voltage and Improved Subthreshold Swing Using NiOX/ITO Reverse Bias Gated Diamond pMOS

An increase in the device performance of diamond‐based p‐type metal–oxide–semiconductor (pMOS) transistors using a combination of p‐type nickel oxide and n‐type indium tin oxide (NiOX/ITO) reverse bias diode as the gate dielectric is reported. Negative threshold voltage pMOS transistors are desirable for digital circuits and power applications for fail‐safe operation. A Schottky gate‐based conventional diamond pMOS transistor suffers from many limitations, including a positive threshold voltage (VT). Herein, it is experimentally demonstrated that NiOX/ITO gate dielectric with Al gate contact circumvents many critical limitations, providing a negative threshold voltage of −1.2 V, improved subthreshold slope of 145 mV dec−1, current ON/OFF ratio >107, and peak gate leakage current reduction >103. An Al/NiOX‐based control gate structure shifts the VTH negative with improvements in crucial device performances. Adding a reverse bias junction through the Al/ITO/NiOX heterointerface with the Al metal gate further improves performance. The measured device characteristics are explained in a common framework of energy band diagram for all the devices.

Near-infrared and mid-infrared light emission of boron-doped crystalline silicon.

The bottleneck in achieving fully integrated silicon photonics lies in silicon-based light-emitting devices that are compatible with standard CMOS technology. Dislocation loops created by implanting boron into silicon and annealing represent an enticing strategy to transform highly inefficient silicon into a luminescent material. However, the emission at telecommunication wavelength suffers from the strong thermal quenching effect, resulting in low efficiency at room temperature. Here, we applied a new deep cooling process to address this issue. Interestingly, we find that electrons and holes recombine through defects emitting two photons, one in near infrared (NIR, 1.3∼1.6 µm) and the other in mid-infrared band (MIR, around 3.5 µm). The photoluminescence intensity at NIR increases three fold when the temperature increases from 77 K to 300 K. Furthermore, the NIR light emission of reverse biased silicon diodes was significantly enhanced compared to forward bias, emitting the maximum output power of 42 nW at 60 mA. The results offer new opportunities for the development of infrared light sources in integrated circuits.

The Charging and Discharging of Reverse Biased Schottky Diode Voltage-Dependent Capacitor


 Transient analysis of RC circuit with voltage step source, constant resistor and nonlinear voltage-dependent capacitors with the capacitance given by C(vc) = Co/√(1+vc/Vbi), where Co and Vbi are constant and vc is the voltage across the capacitor, was carried out. The analysis was restricted to this class of nonlinear capacitors, because they represent with acceptable approximation the capacitances of reverse-biased Schottky diodes, which are very important and usually used in several static power converters practical applications. The charging and discharging are described by explicitly solvable nonlinear first-order differential equations. The theoretical analysis results are verified by numerical examples with computer simulation and also by experimentation in the laboratory.
 

Micro-Raman Spectroscopy Study of Vertical GaN Schottky Diode

In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, on the diode electrical performances. Evidence of dislocations in the diode epilayer was spotted thanks to the CL measurements. Then, using 2D mappings of the E2h and A1 (LO) Raman modes, dislocations and other peculiar structural defects were observed. The I-V measurements of the diodes revealed a significant increase in the leakage current with applied reverse bias up to 200 V. The combination of physical and electrical characterization methods indicated that the electrical leakage in the reverse biased diodes seems more correlated with short range non-uniformities of the effective doping than with strain fluctuation induced by dislocations.

Iontronic analog of synaptic plasticity: Hydrogel-based ionic diode with chemical precipitation and dissolution

In this study, an aqueous nonlinear synaptic element showing plasticity behavior is developed, which is based on the chemical processes in an ionic diode. The device is simple, fully ionic, and easily configurable, requiring only two terminals-for input and output-similar to biological synapses. The key processes realizing the plasticity features are chemical precipitation and dissolution, which occur at forward- or reverse-biased ionic diode junctions in appropriate reservoir electrolytes. Given that the precipitate acts as a physical barrier in the circuit, the above processes change the diode conductivity, which can be interpreted as adjusting "synaptic weight" of the system. By varying the operating conditions, we first demonstrate the four types of plasticity that can be found in biological system: long-term potentiation/depression and short-term potentiation/depression. The plasticity of the proposed iontronic device has characteristics similar to those of neural synapses. To demonstrate its potential use in comparatively complex information processing, we develop a precipitation-based iontronic synapse (PIS) capable of both potentiation and depression. Finally, we show that the postsynaptic signals from the multiple excitatory or inhibitory PISs can be integrated into the total "dendritic" current, which is a function of time and input history, as in actual hippocampal neural circuits.

Low voltage AC electroluminescence in silicon MOS capacitors

Low power silicon based light source and detector are attractive for on-chip photonic circuits given their ease of process integration. However, conventional silicon light emitting diodes emit photons with energies near the band edge where the corresponding silicon photodetectors lack responsivity. On the other hand, previously reported hot carrier electroluminescent silicon devices utilizing a reverse biased diode require high operating voltages. Here, we investigate hot carrier electroluminescence in silicon metal–oxide–semiconductor capacitors operating under transient voltage conditions. During each voltage transient, large energy band bending is created at the edge of the source contact, much larger than what is achievable at a steady state. As a result, electrons and holes are injected efficiently from a single source contact into the silicon channel at the corresponding voltage transient, where they subsequently undergo impact ionization and phonon-assisted interband recombination. Notably, we show low voltage operation down to 2.8 V by using a 20 nm thick high-κ gate dielectric. We show further voltage scaling is possible by reducing the gate dielectric thickness, thus presenting a low voltage platform for silicon optoelectronic integrated circuits.

Analysis and Application of the Equivalent Circuit Model for Core Snubber

Core snubber is a surge suppression protection device installed between the high voltage power supply and the auxiliary heating load. When a breakdown occurs, the core snubber can limit the short-circuit current and consume fault energy, thus protecting the high-voltage power supply and auxiliary heating load. The existing snubber schemes have the problems of large volume, high price, complex integrated design, and large inductance affecting the normal working current of the power supply, so a new expression of equivalent magnetization inductance is established based on the saturated wave theory. The equivalent circuit model of core snubber is improved, and the surge suppression characteristics of core snubber and the attenuation process of breakdown arc current are studied. The circuit model consists of a magnetized inductor and an eddy current resistor in parallel. The expression can be expressed by the characteristic parameters of the alloy winding, the structural size of the core and the voltage integral at both ends of the snubber. In this article, a prototype of iron-based nanocrystalline snubber is made, and a dc high-voltage short-circuit experimental platform is built. By comparing the simulation and measured results of the prototype, the accuracy of the snubber equivalent parallel circuit model derived in this article and its practicability in core design are verified. There are other circuit components in the breakdown discharge circuit of the auxiliary heating system in addition to the distributed capacitance and snubber. In order to further analyze the surge suppression characteristics and breakdown arc current attenuation process of the core snubber including other circuit components, in this article, the extended discharge circuit with reverse bias diode and secondary winding is simulated and tested. The influence of the bridge arm in the reverse bias state on the arc current in the high voltage uncontrolled rectifier during breakdown is discussed. In view of the thickness limitation of core strip, the effectiveness of reasonable setting of secondary winding to avoid core saturation is demonstrated through simulation and measured analysis.

Simulation and Experimentation of Sawtooth Wave Generation using Diode-Capacitor Pair

A simple, inexpensive and efficient circuit for generating sawtooth waves is demonstrated in this paper. The novelty of this work lies in the fact that the voltage of a charging capacitor provides linear response when it is charged through a reverse-biased diode. A rectangular wave of extremely high duty cycle is used as a reference signal to drive the passive circuit consists of a diode–capacitor pair. During the on-time of the reference signal, the diode remains in reverse biased condition while charging the capacitor and during charging through the reverse-biased diode, the capacitor voltage produces the required ramp. During the off-time of the reference wave, the diode becomes forward biased and the capacitor discharges very fast through the forward-biased diode and thus a sawtooth wave has resulted. At high frequencies, the parasitic depletion capacitance of the diode cannot be ignored and it limits the frequency of operation. Laboratory experiments, as well as PSPICE circuit simulations, are performed to established our idea of generating sawtooth waveforms. The experiment is found to be repetitive and robust.

A Snapback Suppressed RC-IGBT With N-Si/n-Ge Heterojunction at Low Temperature

This article proposes an RC -IGBT structure with N-Si/n-Ge heterojunction (NNH-IGBT) to suppress snapback effect. Because the proposed N-Si/n-Ge heterojunction acts as a gradually reverse bias diode to suppress the electron flow into the N-short region, so the snapback effect can be suppressed. For the same ${\mathrm{\scriptstyle {ON}}}$ -state voltage drop ( ${V}_{\text {CE}}$ ), the turn-off loss ( ${E}_{\mathrm{\scriptstyle {OFF}}}$ ) of the NNH-IGBT is lower than the conventional RC -IGBT (Con- RC -IGBT). In addition, the reverse recovery speed of NNH-IGBT is nearly identical to the Con- RC -IGBT. Because of the use of heterojunction, the NNH-IGBT is suitable for operate to suppress the snapback effect, especially at low temperatures.

An SECE array of piezoelectric energy harvesting

The paper studies the electrical response of an array of piezoelectric oscillators attached to the synchronized electric charge extraction (SECE) interface circuit. The analytic estimate of output power is derived and presented through the matrix formulation of generalized Ohm’s law (charging on capacitance) for the case of parallel (series) connection of energy harvesters. These formulations mainly depend on the proposed equivalent load impedances which are independent of external resistive loads. It therefore offers an advantage of enabling harvested power independent of DC output voltage and making the harvester array desirable for broadband energy scavenging. The proposed framework is subsequently validated both numerically and experimentally. The results show that the power output and bandwidth of an SECE-based array are superior to that based on the standard energy harvesting circuit. Further, it is found that the behavior of an SECE array electrically arranged in parallel connection is different from that connected in series. The former demonstrates the output power higher than the latter, while the latter exhibits roughly uniform peak power in frequency response. However, the experiment indicates the unexpected power drop deviated significantly from the prediction in the array of harvesters connected in series. Such a discrepancy is explained as a result of comparatively serious leakage current in the reverse-biased diodes.

A Power MOSFET with P-base Schottky Diode and Built-in Channel Diode for Fast Reverse Recovery

A power MOSFET with P-base Schottky diode and built-in channel diode is proposed and numerically investigated in this article. The P-base Schottky diode formed by the P-base Schottky contact is in reverse series with the P-base/N-drift junction diode. Besides, by coupling the gate of the dummy MOSFET to the source, a built-in channel diode is introduced, which provides a unipolar reverse conduction current path and drastically reduces the gate-to-drain charge. When the proposed MOSFET serves as the freewheeling diode, the reverse-biased P-base Schottky diode inactivates the P-base/N-drift junction diode, so that the reverse current will be carried out by the built-in channel diode. As a result, in comparison with the planar gate power MOSFET, the reverse recovery charge and the gate-to-drain charge could be reduced by 96.9 % and 75.4%, respectively.

An analytical model for merged GaN heterojunction barrier Schottky diodes with inserting p-Si technology

A novel combined GaN/Si device based on compatible CMOS semiconductor, merged heterojunction barrier Schottky (MHBS) diode is put forward and its generalized analytical heterojunction model is further built and validated. The fully two-dimension (2D) analytical model is developed based on new structure of the MHBS diode, which replaces the conventional junction-based region with inserting p-type Si technology. It provides a novel expression of potential and electric field distribution. The results of the fully 2D analytical model are validated in comparison with the numerical simulations for various device parameters, such as junction spacing widths and junction depths as well as reverse biases. Based on the derived reverse surface electric filed, the reverse I-V characteristics are also calculated by using the reverse conduction mechanism. The conduction band energy diagram is applied to analyze the reverse characteristic. Furthermore, the concept of shielding effect factor ( ξ ) and electric field coefficient of α are proposed for trading off the shielding tolerance of reverse biased MHBS diode compared with Schottky diode. As a result, this device modeling would be easily used for device design and provides a comprehensive physical understanding for GaN based MHBS diode as well. • Proposing novel GaN/Si device, merged heterojunction barrier Schottky diode. • Replacing junction-based region with inserting p-Si by feasible, also develop the compatible GaN/CMOS process technology to solve the bottleneck of conventional GaN MPS or JBS device employing GaN with magnesium impurity as p-type. • Deriving and validating fully 2D analytical model with simulator. • Proposing new concepts of shielding effect factor. • Device modeling is useful for device design and physical understanding.

Intrinsic carrier multiplication in layered Bi2O2Se avalanche photodiodes with gain bandwidth product exceeding 1 GHz

Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities, strong light-matter interactions, and tunable optical absorption and emission. Here, metal-semiconductor-metal avalanche photodiodes (APDs) are fabricated from Bi2O2Se crystals, which consist of electrostatically bound [Bi2O2]2+ and [Se]2− layers. The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of ~ 400 kHz at a visible wavelength of 515.6 nm, ultimately resulting in a gain bandwidth product exceeding 1 GHz. Due to exceptionally low dark currents, Bi2O2Se APDs also yield high detectivities up to 4.6 × 1014 Jones. A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi2O2Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of ~ 44 meV, in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors. In this manner, layered Bi2O2Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.

Optimized Substrate for Improved Performance of Stacked Nanosheet Field-Effect Transistor

The recently proposed stacked nanosheet-field-effect transistor (SNSH-FET) is considered as a promising candidate for continued scaling with silicon. While using punchthrough-stopper-doped (or) ground-plane-doped silicon substrate (PTS-Si substrate) in which the top part of the substrate is doped heavily with the p-type (for nMOS) impurity to avoid punchthrough leakage between the source and the drain. The heavily doped p–n junction formed at the drain–substrate junction acts as a reverse-biased tunnel diode during ${V}_{{\text {DS}}}$ biasing, which leads to large substrate leakage current. We presented SuperSteep-Retrograde silicon substrate (SSR-Si substrate) configuration which reduces the tunneling current by increasing the tunnel barrier width and diminishing the peak electric field at the drain–substrate junction. The SSR-Si substrate is achieved by growing a lightly doped or undoped layer of silicon (SSR-buffer layer) on the PTS-doped substrate. The impact of SSR-buffer layer thickness is studied and the optimal thickness (12 nm) is presented. The vertically stacked channels’ configuration leads to position-dependent current densities in different channels due to position-dependent series resistance. Herein, we present nanosheet width optimization as a solution to achieve homogeneous current ratio between all the channels thereby resulting in better linearity performance. The self-heating and RF performance of the presented SSR-Si substrate is compared with the silicon-on-insulator (SOI) substrate. The results show that SSR-Si substrate can be a better substrate for SNSH-FET because of better self-heating performance.

Commercialization of Highly Rugged 4H-SiC 3300 V Schottky Diodes and Power MOSFETs

In this paper, we present a new family of 3300 V silicon carbide (SiC) Schottky barrier diodes (SBDs) and power MOSFETs. The main design requirements are discussed with an emphasis on the design rules to improve the long-term reliability. Basic static and dynamic performance demonstrates low conduction and switching losses. Long-term tests such as high-temperature reverse bias (HTRB) and body diode forward bias stress were performed to evaluate the devices’ reliability. An emission microscopy (EMMI) study was conducted to assess the quality of the gate oxide. Outstanding surge and avalanche capabilities are reported with UIS ruggedness of 11.4 and 20.8 J.cm-2 for SBDs and MOSFETs, respectively.

Mid-Infrared InAs/GaSb Superlattice Planar Photodiodes Fabricated by Metal–Organic Chemical Vapor Deposition**Supported by the National Natural Science Foundation of China (Grant Nos. 61874179, 61804161, and 61605236).

Mid-wavelength infrared planar photodiodes were demonstrated, in which both the epitaxy growth of InAs/GaSb superlattices and the thermal diffusion of p-type dopant were performed in production-scale metal–organic chemical vapor deposition reactors. The formation of a planar homojunction was confirmed by secondary ion mass spectroscopy and its I–V characteristics. A cut-off wavelength around 5 μm was determined in 77 K optical characterization, and photo-current as high as 600 nA was collected from a reverse-biased planar diode of 640 μm diameter. These preliminary results were obtained despite the structural degradation revealed by x-ray diffraction, and we attribute the degradation to the concert of thermal annealing and high Zn concentration behind the diffusion front.

A Low-Reverse-Recovery-Charge Superjunction MOSFET With P-Base and N-Pillar Schottky Contacts

A superjunction metal-oxide-semiconductor field-effect transistor (SJ-MOSFET) with P-base and N-pillar Schottky contacts is proposed and investigated in this article. The dual Schottky contacts form a p-type Schottky diode and an n-type Schottky diode on the surface of the device, respectively. During the reverse conduction stage, the operation of the body p-n junction diode is suppressed by the reverse-biased p-type Schottky diode, and the reverse current is fully conducted by the n-type Schottky diode. Therefore, the minority carrier injection is completely suppressed, leading to an ultralow reverse recovery charge. TCAD simulation results show that, in comparison with the conventional SJ-MOSFET, up to 95.7% reduction in reverse recovery charge could be achieved.

An efficient hybrid solar and electromagnetic harvesting system for autonomous operation of small sensors

In this study, we propose a combination of solar cells and a rectenna to realize a solar and electromagnetic energy harvesting system. The proposed harvester consists of a circular slot antenna, a rectifier circuit which is designed with a reverse-biased Schottky diode, and SHJ solar cells with a combination of AZO/TiO2 as antireflection coating and a diffraction grating morphology. Each designed component has been characterized through simulations and measurements. First, the solar cells are designed and investigated separately. Then, they are carefully placed near the slot loop antenna, which is attached to the rectifier circuit, to realize the combined harvesting system. The heterojunction solar cells with an intrinsic thin layer (SHJ) have been designed based on light trapping mechanism, which reduces the reflection of solar radiation and interfacial traps effects significantly. Solar cells’ simulations are obtained using an analytical model. The parameters of light trapping, as well as the effects of the position of the solar cells on board of the patch, are studied carefully. Simulation and experimental results validate that the combined harvesting system is a promising candidate for autonomous operation of some sensors and small devices. Indeed, the efficiency of the rectenna is enhanced greatly from 21to 74 % when combined with the solar cells.

Electroluminescence of Cr3+ and pseudo-Stark effect in β-Ga2O3 Schottky barrier diodes

Bright, red electroluminescence is generated in reverse biased Schottky barrier diodes (SBDs) based on β-Ga2O3 single crystals codoped with chromium and silicon. It is due to intracenter transitions of octahedrally coordinated Cr3+ ions excited by electron impact in the depletion layer of the diodes. The electroluminescence spectrum around 700 nm in wavelength is nearly identical to the spectrum of the well-known photoluminescence of Cr3+ in β-Ga2O3, which is featured by the two lines R1 and R2. In contrast to the photoluminescence, however, in the electroluminescence, each of the R1 and R2 lines is additionally split by 1.5–3 meV. Since the R1/R2 lines correspond to transitions from two Kramers-degenerate states (split 2E excited state) to the ground state 4A2, this splitting cannot be ascribed to the normal Stark effect in the strong electric field of the Schottky barrier diode's depletion layer. Instead, we explain the splitting by the pseudo-Stark effect that occurs because the Cr3+ ions replace Ga3+ at two kinds of energetically equivalent octahedral sites that differ crystallographically by an inversion at the Cr ion. Superposition of the dominating R1 doublet radiation would result in a tunable beat frequency of about 0.4–0.7 THz and might be utilized for a terahertz light source. Moreover, the electroluminescence of chromium is representative of the ability to excite the luminescent states of other transition metals. Hence, high temperature light-emitting SBDs in different colors are a potential application for β-Ga2O3.

Experimental determination of proton hardness factors at several irradiation facilities

The scheduled High Luminosity upgrade of the CERN Large Hadron Collider presents new challenges in terms of radiation hardness. As a consequence, campaigns to qualify the radiation hardness of detector sensors and components are undertaken worldwide. The effects of irradiation with beams of different particle species and energy, aiming to assess displacement damage in semiconductor devices, are communicated in terms of the equivalent 1 MeV neutron fluence, using the hardness factor for the conversion. In this work, the hardness factors for protons at three different kinetic energies have been measured by analysing the I–V and C–V characteristics of reverse biased diodes, pre- and post-irradiation. The sensors were irradiated at the MC40 Cyclotron of the University of Birmingham, the cyclotron at the Karlsruhe Institute of Technology, and the IRRAD proton facility at CERN, with the respective measured proton hardness factors being: 2.1± 0.5 for 24 MeV, 2.2 ± 0.4 for 23 MeV, and 0.62± 0.04 for 23 GeV. The hardness factors currently used in these three facilities are in agreement with the presented measurements.