Leakage Current Research Articles

Damage Effects and Mechanisms of High-Power Microwaves on Double Heterojunction GaN HEMT

In this paper, simulation modeling was carried out using Sentaurus Technology Computer-Aided Design. Two types of high electron mobility transistors (HEMT), an AlGaN/GaN/AlGaN double heterojunction and AlGaN/GaN single heterojunction, were designed and compared. The breakdown characteristics and damage mechanisms of the two devices under the injection of high-power microwaves (HPM) were studied. The variation in current density and peak temperature inside the device was analyzed. The effect of Al components at different layers of the device on the breakdown of HEMTs is discussed. The effect and law of the power damage threshold versus pulse width when the device was subjected to HPM signals was verified. It was shown that the GaN HEMT was prone to thermal breakdown below the gate, near the carrier channels. A moderate increase in the Al component can effectively increased the breakdown voltage of the device. Compared with the single heterojunction, the double heterojunction HEMT devices were more sensitive to Al components. The high domain-limiting characteristics effectively inhibited the overflow of channel electrons into the buffer layer, which in turn regulated the current density inside the device and improved the temperature distribution. The leakage current was reduced and the device switching characteristics and breakdown voltage were improved. Moreover, the double heterojunction device had little effect on HPM power damage and high damage resistance. Therefore, a theoretical foundation is proposed in this paper, indicating that double heterojunction devices are more stable compared to single heterojunction devices and are more suitable for applications in aviation equipment operating in high-frequency and high-voltage environments. In addition, double heterojunction GaN devices have higher radiation resistance than SiC devices of the same generation.

Effect of GaN Cap Thickness on the DC Performance of AlGaN/GaN HEMTs.

We prepared AlGaN/GaN high electron mobility transistors (HEMTs) with GaN cap thicknesses of 0, 1, 3, and 5 nm and compared the material characteristics and device performances. It was found that the surface morphology of the epitaxial layer was effectively improved after the introduction of the GaN cap layer. With the increase of the GaN cap thickness, the carrier concentration (ns) decreased and the carrier mobility (μH) increased. Although the drain saturation current (IdSat) of the device decreased with the increasing GaN cap thickness, the excessively thin GaN layer was not suitable for the cap layer. The thicker GaN layer not only improved the surface topography of the epitaxial layer but also effectively improved the off-state characteristics of the device. The optimal cap thickness was determined to be 3 nm. With the introduction of the 3 nm GaN cap, the IdSat was not significantly reduced. However, both the off-state gate leakage current (IgLeak) and the off-state leakage current (IdLeak) decreased by about two orders of magnitude, and the breakdown voltage (BV) increased by about 70 V.

Comparative Study on Schottky Contact Behaviors between Ga- and N-Polar GaN with SiNx Interlayer

We conducted a comparative study on the characterization of Ga-polar and N-polar GaN metal–insulator–semiconductor (MIS) Schottky contact with a SiNx gate dielectric. The correlation between the surface morphology and the current–voltage (I–V) characteristics of the Ga- and N-polar GaN Schottky contact with and without SiNx was established. The insertion of SiNx helps in reducing the reverse leakage current for both structures, even though the leakage is still higher for N-polar GaN, consistent with the Schottky barrier height calculated using X-ray photoelectron spectroscopy. To optimize the electric property of the N-polar device, various substrate misorientation angles were adopted. Among the different misorientation angles of the sapphire substrate, the GaN MIS Schottky barrier diode grown on 1° sapphire shows the lowest reverse leakage current, the smoothest surface morphology, and the best crystalline quality compared to N-polar GaN grown on 0.2° and 2° sapphire substrates. Furthermore, the mechanism of the reverse leakage current of the MIS-type N-polar GaN Schottky contact was investigated by temperature-dependent I–V characterization. FP emissions are thought to be the dominant reverse conduction mechanism for the N-polar GaN MIS diode. This work provides a promising approach towards the optimization of N-polar electronic devices with low levels of leakage and a favorable ideality factor.

Organic-inorganic hybrids of BiI3-polymers with embedded conductive carbon fillers displaying high SNR for direct X-ray imaging detectors

Organic polymers are light weight, low toxic and environmentally stable candidates of interest in X-ray detection application. But low attenuation and high recombination rate of charge carriers cause low sensitivity is major limitation of these detectors. In this work, organic polymers (PS/PMMA) composites were prepared with high-Z inorganic BiI3 by simple dry mixing technique. The organic-inorganic hybrid further embedded with conductive carbon filler (MWCNT, CB, GP) to improve the charge collection of the samples. Resistivity and mobility of the samples were studied with help of Hall measurements and mobility-lifetime was calculated by Hecth equation and found (2.1 ± 0.2) × 10−3 cm2V−1. The elemental analysis of the samples had been done by XPS analysis. The X-ray investigations done by using dental X-ray source and the sensitivity of the samples increases from 3.4 to 200 μGy−1 cm−3 by incorporating CB filler with a low leakage current of order of 33.3 pA/cm2.

Leakage current as a probe into the mechanics of carrier transport in insulating composite polymers

Amorphous composite polymers are widely used as insulators in microelectronics due to their high dielectric strength, mechanical robustness, and thermal stability. However, organic–inorganic composite systems suffer from undesirable performance and accelerated degradation due to leakage current (JTot). Unfortunately, the underlying mechanism of JTot and its components (e.g., ionic and electronic constituents) are inadequately understood, particularly in extreme use conditions (e.g., high humidity and temperature). In this study, we use numerical simulation and experimental JTot data (in amorphous epoxy polymer with silica fillers) to (i) unify the electrostatic model for JTot in composite polymers, (ii) illustrate that the early part of JTot (i.e., external current) is primarily due to the image charge associated with ion transport/ localization (Jion) near the metallic contacts, (iii) demonstrate that the accumulated counter-ions reduce the barrier for electronic charge injection (by band bending) and facilitate electronic injection from the metals (Jelec), and (iv) provide an algorithm for the in situ ion transport characterization of composite insulators by exploiting Jion. This work provides new insights regarding the leakage current mechanism and how it can be used as a probe into the complex transport mechanisms of the composite material.

A fault-tolerant QCA-based convolution encoder for robust data transmission

Metal oxide semiconductor (MOS) technology has reached its maximum profitable limits due to increase in leakage current, static power dissipation, limited switching frequency. One of the better solutions to overcome these problems is the quantum-dot cellular automata (QCA) technology, it boasts the absence of physical transportation charges, relying solely on Coulombic force for interaction between the cells also it is a transistor less technology does not require any external voltage bias. In the current integrated circuits, the data being transferred more than ever, the error correction and coding techniques find significance in reliable data communication. Recognizing the increasing importance of error correction in data communication, particularly with the widespread data transfer, this research specifically focuses on the implementation of an enhanced convolutional encoder using QCA for error correction in data transmission. Comparative study with the state-of-art is also carried out to examine performance of proposed design. As a result of our study, we were able to reduce the cell count by 33.34% and power dissipation is reduced by 77% with the proposed 1/2 rate encoder and the proposed 1/3 rate encoder has 15.9% less cell count and power dissipation is reduced by 72% as compared to existing design.

Tunable EOT Scaling Down to 0. 55 nm for HfO2-Based Gate-Stacks on Ge Substrate by In Situ H2 Plasma Treatment

Abstract We propose a continuous fabrication method for HfO2-based gate stacks on a Ge bulk p-type metal–oxide–semiconductor capacitor (pMOSCAP) with HfGeOx interfacial layer by H2 plasma treatment through in situ plasma-enhanced atomic layer deposition. The electrical characteristics showed that the proper hydrogen plasma treatment could obtain an aggressively scaled equivalent oxide thickness of approximately 0.55 nm and a relatively low gate leakage current of 8 × 10-4 A/cm2 under PMA 500C.

In situ electrical characterization of the Au/n-Si Schottky barrier structure under 1.2 MeV Ar ion irradiation

Understanding the impact of energetic ion irradiation on semiconductor materials and devices is essential for optimizing their electronic applications. This knowledge contributes to the broader goal of tailoring material properties to enhance the overall performance and reliability of semiconductor devices. In this study, we investigate the impact of 1.2 MeV Ar8+ irradiation on Au/n-Si Schottky barrier structures in-situ, as a function of ion irradiation fluence. Electrical characterization was performed in-situ on a single sample to mitigate any variability in device parameters between samples. It is observed that ion irradiation results in an increased Schottky barrier height with a reduction in reverse leakage current. The behavior is attributed to dopant deactivation by the energetic ion irradiation-induced defects near the interface. These results underscore the importance of understanding ion irradiation impacts on semiconductor devices, providing valuable insights for optimizing Schottky diodes in electronic applications.

Direct observation of radio-frequency negative differential resistance in GaN-based single drift region IMPATT diodes

We report the direct observation of radio-frequency negative differential resistance, via on-wafer S-parameter measurements, in GaN-based impact ionization avalanche transit time (IMPATT) diodes. Clear signatures of reflection gain are observed from 18.7 to 30.6 GHz. These observations have been made possible by suppressing the reverse leakage current (and thereby parasitic shunt conductance) by optimization of the fabrication process, in conjunction with the use of pulsed measurements to suppress device self-heating. Consistent with avalanche-dominated behavior, the measured DC reverse bias current–voltage measurements show a positive temperature coefficient of breakdown. For the high-frequency on-wafer characterization, pulsed-bias S-parameter measurements with low (0.0067%) duty cycle were used to mitigate thermal effects. The measured avalanche frequency aligns closely with theoretical predictions based on Gilden and Hines' small signal model [Gilden and Hines, IEEE Trans. Electron Devices ED-13(1), 169–175 (1966)], measured impact ionization coefficients [Cao et al., Appl. Phys. Lett. 112(26), 262103 (2018)], and experimental saturation velocity measurements [Bajaj et al., Appl. Phys. Lett. 107(15), 153504 (2015)]; this excellent agreement confirms IMPATT operation and provides insights needed to further optimize device performance.

Investigation of Interlayer Dielectric in BaTiO3/III‐Nitride Transistors

In this study, the impact of varying the thickness of the Al2O3 interlayer dielectric on the electrical characteristics of BaTiO3/III‐nitride transistors is investigated. In the findings, it is revealed that a minimum thickness of 8 nm for the Al2O3 layer is crucial to maintain high device performance and protect against sputtering‐induced damage during BaTiO3 deposition. The fabricated BaTiO3/Al2O3/AlGaN/GaN high electron mobility transistors exhibit exceptional electrical properties, including a maximum current density of 700 mA mm−1, an on‐resistance of 5 Ω mm, an ION/IOFF ratio of 107, a subthreshold slope of 119 mV dec−1, and significantly reduced gate leakage current. The devices with the optimal 8 nm Al2O3 thickness demonstrates excellent agreement between theoretical and experimental values for effective mobility, achieving a value of 1188 cm2 V−1·s at a 2D electron gas density of 1013 cm−2. Furthermore, in the study, it is confirmed that increasing the Al2O3 thickness also improves the quality of interface charge density, as evidenced by the results obtained from capacitance–voltage measurements. In these findings, the critical role of controlling the Al2O3 thickness in optimizing the electrical characteristics and overall performance of BaTiO3/III‐nitride transistors are highlighted.

Forward leakage currents in GaN p-i-n diodes

Excessive forward leakage currents in GaN p-i-n diodes were investigated. Traditional diffusion mechanism dominates at VF > 2 V. The effective band gap is derived to be ∼2.21 eV, which is much lower than 3.4 eV and attributed to a band fluctuation caused by dislocations; At 1.35 V < VF < 2 V, a trap-assisted tunneling process becomes important, whose ideality factor is still larger than 4.1 at T = 400 K; Two distinct power-law relationships were observed at lower biases, separated at VF = 0.8 V, whose exponents are extracted to be ∼8 and ∼4, respectively. The behavior is in a good agreement with the space-charge-limited model, featuring an exponentially decaying distribution of trap states below the conduction band.

Impact of Carbon Doping on Vertical Leakage Current in AlGaN‐Based Buffer Layer Grown on Silicon Substrate

The buffer leakage phenomena have a large effect on high‐power and fast‐switching GaN high electron mobility transistor devices. Herein, the buffer leakage mechanism in a GaN‐on‐Si substrate with AlGaN buffer layers is investigated by using samples with various carbon concentrations. Comparing the leakage current with crystallinity and impurity concentration, it is found that the vertical leakage current is dominated by both threading dislocations and bulk impurities. Increasing the carbon concentration of buffer layers suppresses leakage current in the bulk conducting regime in high electric fields but increases it in the dislocation conducting regime in low electric fields. These results indicate that the optimal carbon concentration of buffer layers depends on the target electric field.

Enhancing the Forward Gate Bias Robustness in p‐GaN Gate High‐Electron‐Mobility Transistors through Doping Profile Engineering

This article presents a study on the improvement of the gate robustness and reliability of p‐GaN gate high‐electron‐mobility transistors (HEMTs) by doping profile engineering and by performing a thermal treatment. The reduction of the p‐doping concentration at the Schottky interface using a graded magnesium (Mg) profile in the p‐GaN layer and introducing a top Si‐GaN cap layer is proposed, combined with a high‐temperature anneal step after the gate patterning. The results show that the proposed approach enhances the gate breakdown voltage, reduces the gate leakage current, and increases the time to failure under constant voltage stress, while ensuring stable dynamic behavior and off‐state leakage performance under high‐voltage stress.

Failure analysis of heavy ion-irradiated silicon carbide junction barrier Schottky diodes

An analysis of damage, including single event burnout (SEB) and single event leakage current (SELC) caused by heavy ion irradiation in silicon carbide (SiC) junction barrier Schottky diodes (JBSDs), was performed using Auger electron spectroscopy (AES), emission microscope (EMMI), focused ion beam (FIB), transmission electron microscopy (TEM) and other methods. The damage of SEB extending from the Schottky contact through the epitaxial layer to the SiC substrate was observed. The damage causing SELC was related to the micro-burnout of the Schottky contact. It was concluded that the damage of Schottky contact was induced by incident high-energy particles under a large electric field, forming a leakage current path, resulting in SEB and SELC in the SiC device.

Ultralow-power optoelectronic synaptic transistors based on polyzwitterion dielectrics for in-sensor reservoir computing.

Bio-inspired transistor synapses use solid electrolytes to achieve low-power operation and rich synaptic behaviors via ion diffusion and trapping. While these neuromorphic devices hold great promise, they still suffer from challenges such as high leakage currents and power consumption, electrolysis risk, and irreversible conductance changes due to long-range ion migrations and permanent ion trapping. In addition, their response to light is generally limited because of "exciton-polaron quenching", which restricts their potential in in-sensor neuromorphic visions. To address these issues, we propose replacing solid electrolytes with polyzwitterions, where the cation and anion are covalently concatenated via a flexible alkyl chain, thus preventing long-range ion migrations while inducing good photoresponses to the transistors via interfacial charge trapping. Our detailed studies reveal that polyzwitterion-based transistors exhibit optoelectronic synaptic behavior with ultralow-power consumption (~250 aJ per spike) and enable high-performance in-sensor reservoir computing, achieving 95.56% accuracy in perceiving the trajectory of moving basketballs.

Cobalt-Ion Superhygroscopic Hydrogels Serve as Chip Heat Sinks Achieving a 5°C Temperature Reduction via Evaporative Cooling.

In the rapidly advancing semiconductor sector, thermal management of chips remains a pivotal concern. Inherent heat generation during their operation can lead to a range of issues such as potential thermal runaway, diminished lifespan, and current leakage. To mitigate these challenges, the study introduces a superhygroscopic hydrogel embedded with metal ions. Capitalizing on intrinsic coordination chemistry, the metallic ions in the hydrogel form robust coordination structures with non-metallic nitrogen and oxygen through empty electron orbitals and lone electron pairs. This unique structure serves as an active site for water adsorption, beginning with a primary layer of chemisorbed water molecules and subsequently facilitating multi-layer physisorption via Van der Waals forces. Remarkably, the cobalt-integrated hydrogel demonstrates the capability to harvest over 1 and 5g g-1 atmospheric water at 60% RH and 95% RH, respectively. Furthermore, the hydrogel efficiently releases the entirety of its absorbed water at a modest 40°C, enabling its recyclability. Owing to its significant water absorption capacity and minimal dehydration temperature, the hydrogel can reduce chip temperatures by 5°C during the dehydration process, offering a sustainable solution to thermal management in electronics.

Study of optical float-zone grown gallium oxide Schottky barrier diode

β−Ga2O3 based lateral Schottky barrier diodes are fabricated using Ni/Au as Schottky contact and Ti/Au as Ohmic contact. The Sn-doped β−Ga2O3 sample is grown by the optical float-zone technique. The effect of trenches, which are used for mesa isolation, on breakdown voltage is investigated. The device shows near-ideal characteristics in terms of built-in potential. The parasitic series and shunt resistances are extracted, and their dependency on temperature is established. Modeling of temperature-dependent reverse leakage current is demonstrated using the thermionic emission model, Poole–Frenkel emission model, and Fowler-Nordheim tunneling mechanism. The procedure to extract relevant parameters is explained in terms of bias and temperature dependency. The combined model shows excellent agreement with experimental data over a wide range of bias and temperature. The maximum electric field of 2.3 MV cm−1 is achieved.

A simultaneous area, delay and leakage current reduction method for Linear Feedback Shift Register (LFSR) using pulsed latches and DTMOS transistors

In digital circuits, the shift registers are the significant elements having the ability of storing and transmitting the data in sequential manner.The linear feedback shift register (LFSR) uses large number of flips-flops that consumes maximum amount of power. To overcome this issue, this research work concentrates on the design of LFSR for the area efficient, power reduction, minimization of delay and leakage current. By replacing the d-flip-flop with the bi-enabled pulsed latch to reduce the power consumption and delay of the proposed LFSR design. For the minimization of area, leakage current and delay, the hybrid body bias generator with dynamic threshold MOS (BBG-DTMOS) is used. Moreover, the pulsed clock signal is generated in the digital circuit with the aid of hybrid BBG-DTMOS technique. The proposed LFSR design is implemented in the tanner EDA tool with the available CMOS model libraries. Based on the implementation result, the proposed LFSR area is 1824 μm2and its power consumption is 172μW at a 100 MHz clock frequency withVDD=5V. Furthermore, having the better performance in different corners of the method, reduces the propagation delay and leakage current in the digital circuit. The proposed LFSR design is compared with some of the shift registers such as unidirectional and bidirectional shift registers. The existing clock pulse generator such as conventional, delayed clock pulse, TIMBER logic, PTL-AND logic and multiplexer based clock pulse generator (MCPG) are compared with the proposed BBG-DTMOS technique.

An integrated common ground‐based grid‐connected current‐fed switched inverter

AbstractA current‐fed switched inverter and its derivatives are gaining more attention in solar PV grid‐connected applications. In these inverters, the absence of galvanic isolation generates the leakage current, leading to the injection of harmonics and the degradation of solar PV panel life span. This paper proposes an integrated common ground‐based grid‐connected current‐fed switched inverter. The common ground between the input DC source and output AC grid eliminates the leakage current and makes the inverter immune to high‐frequency common‐mode voltage variations. It utilizes the shoot‐through state to boost the input DC voltage and obtain the rated AC output voltage. Moreover, as compared to the contemporary common ground‐based inverter topologies, the number of passive reactive elements and active switches is less. Thereby, the size, cost of the system, and associated power loss are reduced. The proposed inverter's continuous input current and buck–boost nature make it suitable for applications like solar PV systems. The steady‐state analysis of the proposed inverter is validated using the MATLAB Simulink tool, and furthermore, the simulation results during grid‐tied mode have been cross‐verified with the help of real‐time simulator OPAL‐RT. Further, the power loss and thermal loss analysis are carried out using the PLECS software. Finally, the performance of the inverter and simulation results are verified with the experimental results.

X-ray Induced Electric Currents in Anodized Ta2O5: Towards a Large-Area Thin-Film Sensor.

We investigated the characteristics of radiation-induced current in nano-porous pellet and thin-film anodized tantalum exposed to kVp X-ray beams. We aim at developing a large area (≫cm2) thin-film radiation sensor for medical, national security and space applications. Large area (few cm2) micro-thin Ta foils were anodized and coated with a counter electrode made of conductive polymer. In addition, several types of commercial electrolytic porous tantalum capacitors were assembled and prepared for irradiation with kVp X-rays. We measured dark current (leakage) as well as transient radiation-induced currents as a function of external voltage bias. Large transient currents (up to 50 nA) under X-ray irradiation (dose rate of about 3 cGy/s) were measured in Ta2O5 capacitors. Small nano-porous Ta and large-area flat Ta foil capacitors show similar current-voltage characteristic curve after accounting for different X-ray attenuation in capacitor geometry. The signal is larger for thicker capacitor oxide. A non-negligible signal for null external voltage bias is observed, which is explained by fast electron production in Ta foils. Anodized tantalum is a promising material for use in large-area, self-powered radiation sensors for X-ray detection and for energy harvesting.