Trap Levels Research Articles

Reliability study of nano ribbon FET with temperature variation including interface trap charges

The nano ribbon FET (NR-FET) is an emerging device as multigate structure can be designed on a single substrate, which leads to improvement in device performance. However, the presence of multiple gate oxide and semiconductor interface creates a number of interface trap charges (ITCs), which leads to variation in device performance. In this paper, the assessment of reliability for NR-FET is performed under the impact of ITCs for different polarity. We have incorporated the ITCs along with wide variations in temperature from 200 to 500 K to study the DC, RF/analog, and linearity performance of NR-FET. It is seen that the increase in amount of positive ITCs (PITCs) leads to improvement in ON state current and less gate voltage is required to turn on the device. Also, the cut-off frequency and speed of the device can be improved through increasing the PITCs in NR-FET. The degradation in OFF state current and device efficiency (gm/ID) is observed with increased in temperature from 200 to 500 K. However, the linearity characteristics is improved at high temperature for different polarity in ITCs. This device provides ION = 9.77 × 10−4 A, IOFF = 6.23 × 10−13 A, maximum transconductance of 1.4 mS, maximum transconductance generation factor of 36.56 V−1, maximum cut-off frequency of 4.36 × 1012 Hz, delay of 39.6 ps, threshold voltage of 0.4301 V at trap level concentration of 1012 Ccm−2. It is also seen that NR-FET outperforms in terms of DC and RF/analog characteristics with the variation in temperature from 200 to 500 K. The temperature sensitivity is 150 (80) under PITC (NITC) for this NRFET. Due to its improved behaviour in wide range of temperature 200–500 K, this NR-FET can be applicable for defense and space applications.

Dangling Bonds as Possible Contributors to Charge Noise in Silicon and Silicon-Germanium Quantum Dot Qubits.

Spin qubits based on Si and Si1-xGex quantum dot architectures exhibit among the best coherence times of competing quantum computing technologies, yet they still suffer from charge noise that limit their qubit gate fidelities. Identifying the origins of these charge fluctuations is therefore a critical step toward improving Si quantum-dot-based qubits. Here, we use hybrid functional calculations to investigate possible atomistic sources of charge noise, focusing on charge trapping at Si and Ge dangling bonds (DBs). We evaluate the role of global and local environment in the defect levels associated with DBs in Si, Ge, and Si1-xGex alloys, and consider their trapping and excitation energies within the framework of configuration coordinate diagrams. We additionally consider the influence of strain and oxidation in charge-trapping energetics by analyzing Si and GeSi DBs in SiO2 and strained Si layers in typical Si1-xGex quantum dot heterostructures. Our results identify that Ge dangling bonds are more problematic charge-trapping centers both in typical Si1-xGex alloys and associated oxidation layers, and they may be exacerbated by compositional inhomogeneities. These results suggest the importance of alloy homogeneity and possible passivation schemes for DBs in Si-based quantum dot qubits and are of general relevance to mitigating possible trap levels in other Si, Ge, and Si1-xGex-based metal-oxide-semiconductor stacks and related devices.

(Invited) Extraction of Trap Level in GaN Hemt from Transient Current upon Back Gate Voltage Application

Gallium nitride (GaN) have attracted attention as a high frequency and high voltage power device material because they have wide bandgap and high mobility [1]. However, large number of defects exists in the epitaxial layer. Current collapse originated from the traps at the surface and in the buffer layer is one of the results of the defects [2]. To distinguish the bulk traps from the whole current collapse, back-gate voltage application is commonly used [3]. In this study, we measured the bulk traps by measuring the drain transient current by back gate voltage application.TLM pattern (L/W=120/100 mm) was fabricated on an epitaxial wafer; GaN(2nm)/AlGaN(26nm)/ GaN(150/350nm)/C-GaN/buffer/Si sub. Fig. 1 shows the I d-V B characteristic of the TLM, where a threshold voltage (V th) of -300/-450 V can be extracted. A large clock-wise hysteresis suggests large amount of electron trapping in the epitaxial layer. Fig. 2(a) shows the voltage application sequence for measuring the transient I d 2DEG current. A negatively high V B below the V th was applied to clear all the traps initially exists in the epitaxial layers. Then, a step voltage was applied to a certain voltage, and the transient I d was monitored until the value saturates. Fig. 2(b) shows typical transient I d on V B. To analyze the time constant (t) of the transient, the differential of the I d on logarithm time was used, as the time at the peak signal corresponds to the time constant. Fig. 3(a) shows analysis result, and the peak of this graph correspond to t. On the other hand, the amplitude is related to trap density. Fig. 3(b) shows the Alenius plot of the extracted t, and activation energy from 0.2 to 0.3 eV was detected.In conclusion, we have measured the transient I d of GaN-HEMT device with a step voltage application to the substrate back gate. From analysis, we extracted defect levels with activation energy of 0.2 to 0.3 eV. The method is useful for characterizing the trap density in the epitaxial layers.[1] T. Mizutani, et al., IEEE Trans Electron Devices, 50, 10, 2015 (2003).[2] G. Meneghesso, et al., IEEE Trans Electron Devices, 53, 12, 2932 (2006).[3] X. Chen, et al., Appl. Phys. Lett., 117, 26, 263501 (2020). Figure 1

Charge transfer mechanism through S-scheme heterojunction in in-situ synthesized TiO2/Fe-doped hydroxyapatite for improved photodegradation of xanthate

The heterojunction structure of the photocatalyst composite, which necessitates a robust interface and sufficient contact areas, holds the key to obtaining high charge carrier migration efficiency. Here, a novel composite, TiO2 nanoparticles/Fe-doped hydroxyapatite (TONPs/FH_CS), is fabricated using a two-step synthetic technique, in which FH_CS is synthesized from artificial converter slag enriched with Fe and Ca. The unique nanorod@plate structure of FH_CS enables the uniform immobilization of TONPs onto FH_CS. Thereby, an n-n type heterojunction exhibits a highly intimate Ti-O-Fe heterointerface. Kelvin probe testing demonstrates the formation of an interfacial electric field oriented from FH_CS to TONPs, which serves as the driving force for interfacial electron transfer through the Ti-O-Fe channels. The photoacoustic signals provide information on electron trap levels and densities, indicating the formation of the electron transfer channels. •O2– and •OH species are responsible for being the active species in this system. A photoexcited carrier transfer pathway exhibiting an S-scheme mechanism with high separation efficiency significantly enhances the utilization of charge carriers in each phase. Thus, improved xanthate degradation has been achieved using a heterojunction containing a photocatalyst derived from industrial solid waste. This work demonstrates the significant potential of steel-making byproduct utilization in industrial wastewater treatment.

The effect of (In, Cu) doping and co-doping on physical properties and organic pollutant photodegradation efficiency of ZnO nanoparticles for wastewater remediation

In the present work, undoped, (Cu, In) doped and co-doped ZnO nanoparticles are successfully prepared by co‐precipitation technique. The molar concentrations of dopant elements are 2% for both Cu and In doping, and 1%–1% for the Cu/In co-doping. Energy dispersive X-ray (EDX) analysis confirms the chemical composition of the prepared nanoparticles, and proves the effective introduction of dopant elements into the ZnO host lattice. The X-ray diffraction (XRD) analysis indicates the formation of single-phase hexagonal wurtzite structure for the all synthesized samples. The morphological investigation shows change of ZnO nanoparticles from nanotubes to spherical shape under the effect of doping and co-doping. The reflectance spectra show red shift of the absorption edge as a result of Cu doping and Cu/In co-doping effect. The PL spectra confirm emission bands in the visible rage related to the presence of defects, such as oxygen vacancies, as well as shallow trap levels near the conduction band edge. These oxygen deficiencies have an important effect on the charge carrier transport, resulting in the enhancement of electrical conductivity in doped and co-doped ZnO. In addition, photocatalytic performance experiments prove that the photocatalytic activity of ZnO, in the degradation of amido black 10B dye, is significantly enhanced via (Cu, In) doping and co-doping.

Reinforcing Synaptic Plasticity of Defect-Tolerant States in Alloyed 2D Artificial Transistors.

While two-dimensional (2D) materials possess the desirable future of neuromorphic computing platforms, unstable charging and de-trapping processes, which are inherited from uncontrollable states, such as the interface trap between nanocrystals and dielectric layers, can deteriorate the synaptic plasticity in field-effect transistors. Here, we report a facile and effective strategy to promote artificial synaptic devices by providing physical doping in 2D transition-metal dichalcogenide nanomaterials. Our experiments demonstrate that the introduction of niobium (Nb) into 2D WSe2 nanomaterials produces charge trap levels in the band gap and retards the decay of the trapped charges, thereby accelerating the artificial synaptic plasticity by encouraging improved short-/long-term plasticity, increased multilevel states, lower power consumption, and better symmetry and asymmetry ratios. Density functional theory calculations also proved that the addition of Nb to 2D WSe2 generates defect tolerance levels, thereby governing the charging and de-trapping mechanisms of the synaptic devices. Physically doped electronic synapses are expected to be a promising strategy for the development of bioinspired artificial electronic devices.

Unusual heating rates, dose responses and kinetic parameters detected on thermoluminescence from YAl3(BO3)4:Sm3+ phosphors

This study focused on the thermoluminescence (TL) characteristics of YAl3(BO3)4 (YAB) phosphors modified with various contents of Sm3+ ions. The TL response of the YAB: Sm3+ phosphors exposed to beta irradiation was measured across the temperature range of 25–500 °C, exhibiting three TL maxima at 70, 235, and 408 °C. Preheating protocol was also carried out to remove the low temperature TL peak followed by further experiments with the two-remaining high-temperature peaks. In the TL measurements conducted with variable heating rates (HR) between 0.1 and 5 °Cs-1, an anomalous heating rate behaviour was observed. A semi-localized transition model was used to address this feature. There was a standard deviation of less than 5% in the reusability measurements. The results of the kinetic parameters obtained by initial rise (IR) and various heating rate (VHR) methods were compared with those obtained by glow curve deconvolution (GCD) method. Tm-Tstop analysis revealed a continuous distribution of trap levels with a trap depth ranging from 1.35 to 2.20 eV. Through the use of GCD, the glow curve was found to demonstrate general order kinetics and consist of seven superimposed traps. The values of the kinetic parameters obtained for the glow curve agreed with those obtained by other methods excluding the VHR method encountering an anomalous impact. The results obtained from these tests showed that the sample could be successfully used for TL dosimetry applications.

Endowing smart self-reporting epoxy composites with superior electrical properties from ultralow-content electron-donating encapsulated microsensors

Smart self-reporting dielectrics (SRDs) have been extensively utilized for intelligentizing and miniaturizing next-generation advanced electrical and electronic devices. However, switchable structures towards the self-reporting function commonly damage electrical properties, severely undermining the reliability and practicality of SRDs. Herein, the smart self-reporting function and superior electrical properties are simultaneously achieved by incorporating ultralow content microsensors with electron-donating encapsulation into the epoxy matrix. The microsensor is a leuco dye system for self-reporting temperature anomalies through thermochromism. The strong electron-donating melamine–formaldehyde encapsulation of microsensors serves to confine the switchable structures and enhance electrical properties by constructing the interfacial barrier effect through triboelectrification. Under an ultralow doping content of 0.5 phr, the electrical conductivity of SRDs is considerably reduced by about 80% at the elevated temperature of 80 °C compared to that of the widely recognized epoxy insulation. The reduction efficiency is far superior to those of numerous micro- and nanofillers. The interfacial barrier effect can be supported by the significantly reduced trapped charge density and trap levels in SRDs based on thermal stimulated depolarization current results. Consequently, the charge injection and transport in SRDs can be distinctly inhibited, realizing the enhancement of electrical properties. The results of this study could provide a facile and efficient strategy for achieving high-performance SRDs, which is appealing and vital for widespread applications of SRDs.

Hydrothermal crystal growth of tetralithium octafluoridozirconate (Li4ZrF8) and its physicochemical properties

A single crystal of tetralithium octafluridozirconate (Li4ZrF8) has been obtained by using a hydrothermal process. The crystal phase was analyzed using a powder X-ray diffraction pattern and matched with standard reference data. The high-resolution X-ray diffraction curve indicates that the crystal has good crystalline perfection. The thermal behavior of the crystal sample was investigated by TGA/DSC analysis. The optical bandgap of the crystal sample was calculated from the Tauc plot and found to be 5.8 eV. The crystal sample exhibits intrinsic X-ray excited luminescence with a peak maximum of 265 nm. The thermoluminescence measurement shows two peaks, one is at the high-temperature region of 545 K and another one is at the low-temperature region at 383 K. TL kinetic parameters such as activation energy (E) and frequency factor (s) for the peak at 545 K was estimated as 1.20 eV and 2.06 × 10−10 respectively. The sample has good TL sensitivity to the neutron dose in the order of µsv. The low-temperature thermoluminescence measurements were carried out to study the trap levels and found two major glow peaks at 108 and 130 K. Scintillation properties were analyzed under α-rays from a 241Am source. The decay time profile was well fitted with three components and the fitted values show the fast component of 500 ns (9 %), the medium component of 2.4 μs (24 %), and a slow component of 12.8 μs (67 %).

Improvement of electrical insulating properties for defective metal/epoxy resin interface in power modules by micro-plasma jet

High-voltage power modules inevitably face the critical problem of electric field distortion at triple-junction point (Cu/insulation substrate/potting material) and accidental introduction of unexpected micro-metal defects on insulation substrate, which damages electrical insulating properties and induces breakdown. In this study, a novel precise surface treatment method based on atmospheric pressure micro-plasma jet (μ-APPJ) is proposed for rejuvenating and improving electrical insulating properties of defective Cu/epoxy resin (EP) substrate in power modules. Results show that a typical μ-APPJ with a diameter of about 200 μm is developed to precisely treat the micro-level metal defect in Cu/EP interface, and a spherical-clustered Si-containing functional film (∼Si-O4) can be fabricated on EP substrate by optimized Ar/Hexamethyldisiloxane (HMDSO)/μ-APPJ, which significantly enhances the hydrophobicity of EP surface. Moreover, the plasma-assisted film deposition around μm-defect improves interface electrical properties of defective Cu/EP samples, evidenced by higher flashover voltages and suppressed partial discharge. Further analysis based on simulations reveals that the deposited typical film not only promotes charge mobility and creepage distance on EP, but also introduces additional trap levels that capture electrons and inhibit electric field around metal defects, thereby suppressing partial discharge failure and improving electrical insulating properties.

Defect Induced MgO: Li, Sm nanophosphor as a new highly sensitive material for thermoluminescence dosimetry

MgO is drawing considerable attention owing mainly due to its tissue equivalency (Zeff = 10.8) and excellent luminescence response. In this work, we report the synthesis and investigation of a highly sensitive MgO: Li, Sm phosphor in nanocrystalline form for TL dosimetry application. The structural and morphological study has been done using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). TL intensity of gamma irradiated MgO nanophosphor increases with doping of Li and further improves by co-doping with Sm. The MgO: Li, Sm nanophosphor exhibit TL glow curve structure having isolated single peak at 169 °C and linearity in the low dose (13 mGy-5 Gy) as well as high dose range (10–1000 Gy). The TL structure and peak position remains stable at all doses. The phosphor shows excellent stability (low fading rate) and repeatability. TL intensity of MgO: Li, Sm is 12 times higher than that of commercially available LiF: Mg, Ti (TLD 100) and almost equivalent to LiF: Mg, Cu, P (TLD-700 H). This may be attributed to the formation of greater number of density of traps and suitable trapping levels with optimum dopant selection in MgO nanophosphor. The incorporation of the Sm3+ has improved the TL intensity manifold with appearance of desired isolated single peak. The photoluminescence (PL) spectra confirm the Sm3+ emission at 566, 603, 651 and 708 nm with an excitation wavelength of 315 nm. Further the role of dopants has been discussed on the basis of charge transfer mechanism and corelated with associated kinetic parameters for better understanding of TL process. The newly explored MgO: Li, Sm nanophosphor has shown attractive TL dosimetry properties owing to its high sensitivity, stable glow curve structure, dose linearity, low fading and repeatability which meet all the requirement to establish this as a next generation TL phosphor for medical and personal dosimetry application.

High-efficiency upconversion process in cobalt and neodymium doped graphene QDs for biomedical applications

Multiphoton absorbing upconversion nanoparticles are emerging as bioimaging materials but are limited by the low quantum yield of their visible fluorescence. This article contains colloids of graphene quantum dots (GQDs), Neodymium, and Cobalt doped Graphene Quantum dots (Co-GQDs and Nd-GQDs) surrounded by carboxylic acids are synthesized which especially are suitable for bio applications; in this way, carboxylic acid groups exchanged by Amoxicillin as an antibiotic with bactericidal activity. The XRD diffraction method, TEM microscope, UV–Vis, and photoluminescence spectroscopies characterize the synthesized materials. The synthesized Quantum dots (QDs) exhibit upconversion properties and their emission is centered at 480 nm, but a red shift was observed with the increase of the excitation wavelength. In the emission spectra of synthesized QDs that can be related to the defect levels introduced by passivation of the QDs in the structure, the results show that with the interaction of the surface QDs with more carboxylic groups, the redshift is not observed. As the results indicate an increase in the intensity of upconversion emission is recorded for Co-GQDs and Nd-GQDs. The absolute quantum efficiency (QY) for Co-GQDs and Nd-GQDs were determined to be 41% and 100% more than GQDs respectively. DFT calculations indicate a strong bond between graphene and cobalt and Neodymium atoms. In doped materials, there are trap levels between the band gap of the GQDs which are responsible for increasing the intensity of the upconversion phenomenon.

Investigations of defect levels in different sized HgTe nanocrystals based photovoltaic devices using thermal admittance spectroscopy

HgTe nanocrystals (NCs) have unique properties that make them suitable for optoelectronic devices in the mid-wave infrared (MWIR) and short-wave infrared regions. However, electrically active defects can trap charge carriers, reducing their mobility and diffusion length, which degrades the NCs’ optical and electrical properties. In this study, we used the thermal admittance spectroscopic (TAS) method to analyze defects in HgTe NC-based photovoltaic devices. The ITO/HgTe/Al device structure was used to study the defect levels in HgTe nanocrystals and the effect of these traps on transport properties. Using low-temperature I–V measurements, we calculated the trap activation energy as 0.14 eV, and the transport was found to occur mainly through these trap states. From the TAS measurements, the trap activation energy obtained was 0.14 eV, and the concentration of trap level was 3.16×1016cm−3eV−1. We have also fabricated ITO/TiO2/HgTe/Au and fluorine doped tin oxide/TiO2/HgTe/MoO3/Au devices and did TAS measurements to understand the effect of adding electron and hole extraction layer on the formation of defect levels. Intriguingly, a distinct reversal in the capacitance–frequency (C–F) behavior is observed at different temperatures, leading to positive slopes in the Arrhenius plot. This peculiar phenomenon is attributed to the size-dependent doping effects within the HgTe nanocrystals. The outcomes of this study shed light on the significance of understanding and quantifying electrically active defects in HgTe nanocrystals for the advancement of NC-based optoelectronic devices.

High-Throughput Analysis of Neutrophil Extracellular Trap Levels in Subtypes of People with Type 1 Diabetes.

Neutrophils might play an important role in the pathogenesis of autoimmune diseases, including type 1 diabetes (T1D), by contributing to immune dysregulation via a highly inflammatory program called neutrophil extracellular trap (NET) formation or NETosis, involving the extrusion of chromatin entangled with anti-microbial proteins. However, numerous studies reported contradictory data on NET formation in T1D. This might in part be due to the inherent heterogeneity of the disease and the influence of the disease developmental stage on neutrophil behavior. Moreover, there is a lack of a standardized method to measure NETosis in an unbiased and robust manner. In this study, we employed the Incucyte® ZOOM live-cell imaging platform to study NETosis levels in various subtypes of adult and pediatric T1D donors compared to healthy controls (HC) at baseline and in response to phorbol-myristate acetate (PMA) and ionomycin. Firstly, we determined that the technique allows for an operator-independent and automated quantification of NET formation across multiple time points, which showed that PMA and ionomycin induced NETosis with distinct kinetic characteristics, confirmed by high-resolution microscopy. NETosis levels also showed a clear dose-response curve to increasing concentrations of both stimuli. Overall, using Incucyte® ZOOM, no aberrant NET formation was observed over time in the different subtypes of T1D populations, irrespective of age, compared to HC. These data were corroborated by the levels of peripheral NET markers in all study participants. The current study showed that live-cell imaging allows for a robust and unbiased analysis and quantification of NET formation in real-time. Peripheral neutrophil measures should be complemented with dynamic quantification of NETing neutrophils to make robust conclusions on NET formation in health and disease.

Minority Carrier Traps Induced by Neutron Reactions with 4H-SiC

This work presents the characterization of minority carrier traps in epitaxial n-type 4H-SiC after high fluence neutron irradiation using minority carrier transient spectroscopy (MCTS) in a temperature range of 20 K to 660 K. Three minority carrier trap levels are reported, labelled as X, B and Y, whose activation energies were estimated by Arrhenius analysis and where the B level is assigned to substitutional boron (BSi). The dynamic behaviour of the trap levels was studied by consecutive temperature scans.

Electroluminescence Spectra of a Gate Switched MOSFET at Cryogenic and Room Temperatures Agree with Ab Initio Calculations of 4H-SiC/SiO<sub>2</sub>-Interface Defects

To reach the theoretical performance limit of 4HSiCMOSFETs the SiC/SiO2interfacedefects along the inversion channel need to be fully identified in order to be avoided. We employa measurement technique that allows to observe energetically resolved trap states at the SiC/SiO2 interface by measuring the electrolumiscence of a gate pulsed MOSFET. The spectra are recorded at room and cryogenic temperatures with a spectrometer and two different amplitudes of the gate pulse. Comparison of the results to literature allows for identification of the L1 line of the D1 center with an energy of 2.9 eV and suggests donoracceptorpair recombination or Z1/2 to be responsible for the emission around 2.5 eV. Ionization energies of PbC and related vacancy centers determined via ab initio calculations show similar results as the experimental data and provide a possible classification of the trap level around 1.8 eV.

Preparation and optoelectronic performance of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine-CuS films for photovoltaic applications

This work intends to study the effect of the additional inorganic CuS layer between the ITO-contact and the organic 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TTBTP). Two junctions of ITO/TTBTP and ITO/CuS/TTBTP were accomplished by the thermal vacuum evaporating technique. The capacitance-voltage characteristics of these two junctions were investigated. It was found that the built-in voltage was reduced from 0.62 to 0.35 V by the additional inorganic CuS layer. Further, the investigation of the dark current density versus the applied voltage at various temperatures emphasizes the influence of the adding inorganic CuS layer in the lowering of Rs , Rsh and n values. Moreover, getting the same value of the diode quality factor (n) at different temperatures for the two junctions suggested that thermionic emission is the adopted theory. Regarding the power-law (J ∼ Vm) relation, the charge transport mechanism is described by the space charge limited current controlled by a distribution of trap levels. The photoelectric study confirms that the additional inorganic layer plays a key role in the increasing of many parameters such as photosensitivity, short-circuit current density, open-circuit voltage, and power conversion efficiency. Increasing the conversion efficiency ten times by the additional inorganic CuS layer will open the doors for developing the fabrication solar cell with low cost, easily synthesized, and high conversion efficiency.

Investigation of deep defects and their effects on the properties of NiO/β-Ga2O3 heterojuncion diodes

In this study, the effect of rapid thermal annealing (RTA) on the electrical and optical properties of NiO/ β-Ga2O3 heterojunction diodes was investigated using capacitance-voltage, current-voltage, Deep Level Transient Spectroscopy (DLTS), Laplace DLTS, photoluminescence and micro-Raman spectroscopy techniques, and SILVACO-TCAD numerical simulator. The NiO is designed to be lowly-doped, allowing for the NiO full depletion at zero bias and the study of properties of β-Ga2O3 and its interface with NiO. Micro-Raman results revealed good agreement with the theoretical and experimental results reported in the literature. The photoluminescence intensity of the sample after RTA is five times higher than the fresh sample due to a rise in the density of gallium and oxygen vacancies (VGa + VO) in the annealed β-Ga2O3 samples. The current-voltage characteristics showed that annealed devices exhibited a lower ideality factor at room temperature and higher barrier height compared with fresh samples. The DLTS measurements demonstrated that the number of electrically active traps were different for the two samples. In particular, three and one electron traps were detected in fresh samples and annealed samples, respectively. SILVACO-TCAD was used to understand the distribution of the detected electron E2 trap (Ec-0.15 eV) in the fresh sample and the dominant transport mechanisms. A fairly good agreement between simulation and measurements was achieved considering a surface NiO acceptor density of about 1 × 1019 cm−3 and E2 trap depth into the surface of β-Ga2O3 layer of about 0.220 µm and the effect of the most observed Ec-0.75 eV trap level in β-Ga2O3. These results unveil comprehensive physics in NiO/β-Ga2O3heterojunction and suggest that RTA is an essential process for realizing high-performance NiO/β-Ga2O3devices.

Single thermal scan digital system for deep level transient spectroscopy.

We have developed a micro-controller based Deep Level Transient Spectroscopy (DLTS) system to identify the deep-level defects in semiconductors. It consists of Arduino-Due, a capacitance meter, and interface circuits. In addition, we have also developed the algorithms needed for the entire signal processing. It is not limited to Arduino-Due but can be implemented using other micro-controllers also. We have used Arduino-Due to generate the filling pulse and monitor the capacitance, temperature, data acquisition, timing control, and signal processing. The sequence of generating the filling pulse, reading the data, and signal processing is controlled digitally rather than by analog sampling circuits and timers. The minimum pulse width generated using Arduino-Due is 50ns; the pulse width generation depends on various hardware and software parameters and their integration. The resolution in reading the data is 0.8 mV/unit. The time delays in reading the data are appropriately taken care of in the system. The whole experiment can be completed in a single temperature cycle within 2-3h. The system is simple, inexpensive, in an easy-to-use platform, and less time-consuming; minimizes possible errors; and improves accuracy. The measurements using the "micro-controller based DLTS system" are verified by fabricating (Au) gold-doped silicon (Si) p-n junction samples (Au is a well-understood defect in Si). Using the Arduino-Due based DLTS system, we calculated the energy, the capture cross section, and the concentration of trap levels. The results are in good agreement with the literature, indicating the versatility of the system.

Oxide and Interface Defect Analysis of lateral 4H-SiC MOSFETs through CV Characterization and TCAD Simulations

We investigated oxide and interface defects of lateral 4H-SiC MOSFETs through capacitance-voltage (C-V) and conductance-voltage (G-V) characterization at various frequencies and temperatures. By employing consecutive up and down sweeps of the gate voltage at three different temperatures, we experimentally characterized the hysteresis width as the difference between up and down sweeps in the depletion to accumulation (d-a) and depletion to inversion (d-i) regions. We observed an increase in the hysteresis width with decreasing temperature. Although the hysteresis width is not affected by the small-signal frequency, at the same time, increasing the frequency leads to a strong stretch-out effect, especially in the d-i region.Our measurement results indicate that the hysteresis deformation of the C-V curves is dominated by three different trap types. First, interface acceptor-like defects located close to the conduction band can follow the small-signal frequency. Slower acceptor-like border traps with trap levels both close to the conduction band and in the middle of the band gap are however responsible for the increase of trapped negative charge with increasing gate voltage. Finally, we assume the presence of a fixed positive charge.