Transistor Applications Research Articles

Impact of annealing temperature on the ferroelectric properties of W/Hf0.5Zr0.5O2/W capacitor

Crystallization annealing is a crucial process for the formation of the ferroelectric phase in HfO2-based ferroelectric thin films. Here, we systematically investigate the impact of the annealing process, with temperature varied from 350 °C to 550 °C, on the electricity, ferroelectricity and reliability of a Hf0.5Zr0.5O2 (HZO; 7.5 nm) film capacitor. It was found that HZO film annealed at a low temperature of 400 °C can effectively suppress the formation of the monoclinic phase and reduce the leakage current. HZO film annealed at 400 °C also exhibits better ferroelectric properties than those annealed at 350 °C and 550 °C. Specifically, the 400 °C-annealed HZO film shows an outstanding 2P r value of 54.6 μC⋅cm−2 at ± 3.0 MV⋅cm−1, which is relatively high compared with previously reported values for HZO film under the same electric field and annealing temperature. When the applied electric field increases to ± 5.0 MV⋅cm−1, the 2P r value can reach a maximum of 69.6 μC⋅cm−2. In addition, the HZO films annealed at 400 °C and 550 °C can endure up to bout 2.3 × 108 cycles under a cycling field of 2.0 MV⋅cm−1 before the occurrence of breakdown. In the 400 °C-annealed HZO film, 72.1% of the initial polarization is maintained while only 44.9% is maintained in the 550 °C-annealed HZO film. Our work demonstrates that HZO film with a low crystallization temperature (400 °C) has quite a high ferroelectric polarization, which is of significant importance in applications in ferroelectric memory and negative capacitance transistors.

Challenges and Opportunities for High-Power and High-Frequency AlGaN/GaN High-Electron-Mobility Transistor (HEMT) Applications: A Review.

The emergence of gallium nitride high-electron-mobility transistor (GaN HEMT) devices has the potential to deliver high power and high frequency with performances surpassing mainstream silicon and other advanced semiconductor field-effect transistor (FET) technologies. Nevertheless, HEMT devices suffer from certain parasitic and reliability concerns that limit their performance. This paper aims to review the latest experimental evidence regarding HEMT technologies on the parasitic issues that affect aluminum gallium nitride (AlGaN)/GaN HEMTs. The first part of this review provides a brief introduction to AlGaN/GaN HEMT technologies, and the second part outlines the challenges often faced during HEMT fabrication, such as normally-on operation, self-heating effects, current collapse, peak electric field distribution, gate leakages, and high ohmic contact resistance. Finally, a number of effective approaches to enhancing the device's performance are addressed.

Multimodal Encapsulation to Selectively Permeate Hydrogen and Engineer Channel Conduction for p-Type SnOx Thin-Film Transistor Applications.

It has been challenging to synthesize p-type SnOx (1 < x < 2) and engineer the electrical properties such as carrier density and mobility due to the narrow processing window and the localized oxygen 2p orbitals near the valence band. Herein, we report on the multifunctional encapsulation of p-SnOx to limit the surface adsorption of oxygen and selectively permeate hydrogen into the p-SnOx channel for thin-film transistor (TFT) applications. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements identified that ultrathin SiO2 as a multifunctional encapsulation layer effectively suppressed the oxygen adsorption on the back channel surface of p-SnOx and selectively diffused hydrogen across the entire thickness of the channel. Encapsulated p-SnOx-based TFTs demonstrated much enhanced channel conductance modulation in response to the gate bias applied, featuring higher on-state current and lower off-state current (on/off ratio > 103), field effect mobility of 3.41 cm2/(V s), and threshold voltages of ∼5-10 V. The fabricated devices show minimal deviations as small as ±6% in the TFT performance parameters, which demonstrates good reproducibility of the fabrication process. The relevance between the TFT performance and the effects of hydrogen permeation is discussed in regard to the intrinsic and extrinsic doping mechanisms. Density functional theory calculations reveal that hydrogen-related impurity complexes are in charge of the enhanced channel conductance with gate biases, which further supports the selective permeation of hydrogen through a thin SiO2 encapsulation.

Synthesis of thieno[3,4-c] pyrrole-4,6-dione-based small molecules for application in organic thin-film transistors

The synthesis of two alternating donor-acceptor (D-A) small molecules revolving around thieno[3,4-c]pyrrole-4,6-dione (TPD) as the main acceptor building block is reported herein. The materials are synthesized using a robust Stille coupling to attach the TPD core with thiophene donors on either of its side, and completed with an aldol condensation under mild conditions for the addition of terminal secondary acceptor building blocks, representing a sought out A2-D-A1-D-A2 structure. The two newly synthesized materials are set to be used as organic semiconductors in organic thin-film transistor (OTFT) devices. Comparative optical, computational, and electrochemical studies were carried out on these new materials to investigate their ability to act as potential n-type organic semiconductors. The materials were then incorporated into bottom-gate bottom-contact OTFT devices, and subsequent thin-film engineering studies were done to probe the effects that solvent and post-deposition annealing conditions had on device performance. From these conditions, the rhodanine-derived D-A material exhibited the greatest electron field-effect mobility (0.011 cm2 V−1 s−1), and a threshold voltage of 20.1 V under vacuum.

Interface Engineering and Device Applications of 2D Ultrathin Film/Ferroelectric Copolymer P(VDF‐TrFE)

AbstractFerroelectric materials with switchable electrical polarization have been widely used in tunnel junctions, non‐volatile memories, and field‐effect transistors. Large‐area organic ferroelectric polymers compatible with silicon or flexible substrates have played a crucial role in nanoelectronics. Poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE) as a representative, different from traditional bulk oxide ferroelectrics in terms of atom arrangements and fabrication methods, has frequently been used as the ferroelectric gate for high‐performance electronic, optical, and synaptic transistors. Ferroelectric copolymers have gradually become a promising and versatile alternative for inorganic ferroelectrics. This review will focus on the interface engineering and device applications of 2D materials/ferroelectric P(VDF‐TrFE) hybrid structures. The intrinsic ferroelectric properties and unique features of P(VDF‐TrFE) are first elucidated. Next, typical device structures with ferroelectric gating effect followed by its physical working mechanisms will be discussed. In the next section, diverse nanoelectronics applications of ferroelectric field effect transistors based on P(VDF‐TrFE), including optoelectronic devices, non‐volatile memories, neuromorphic computing, and negative capacitance transistors, are clarified. Moreover, existing challenges and further development for ferroelectric polymer will be discussed. With an emphasis on the ferroelectric polymer gate and related issues, this review provides a timely summary of current physical understanding and progresses.

Functionalized MXene Nanosheets and Al-Doped ZnO Nanoparticles for Flexible Transparent Electrodes

Transparent, flexible, and chemically stable conducting electrodes are the most important key components for fabricating optoelectronic devices. However, in conventional bulk metal–semiconductor (MS) junctions, Fermi-level pinning is a major concern that limits the charge transport properties of the devices. In this work, we have designed MS junctions using two-dimensional (2D) MXene nanosheets and Al-doped ZnO nanoparticles as a metal and an n-type semiconductor, respectively. The heterojunction was formed by layer-by-layer self-assembly on an indium tin oxide (ITO) substrate and probed by the Pt/Ir scanning tunneling microscopy (STM) tip at room temperature. By recording the tunneling current of the components that in turn yielded the density of states of the materials, we could identify their energy positions to determine the band alignments. We then proceeded to form heterojunctions and characterized their current–voltage characteristics through scanning tunneling spectroscopy. The junctions showed rectification, and the rectification ratio varied with the semiconductor doping concentrations. However, the shift of the Fermi level toward the conduction band edge of the semiconductor reduces the Schottky barrier width and consequently lowers the rectification ratio. Additionally, the MS junction with the poly-allylamine (PAH)-functionalized MXene nanosheets and the ZnO layer show a nonrectifying nature with low contact resistance at the interface. This work shows how a functionalized 2D-metal MXene and doped ZnO nanoparticle can tune the MS junction properties, used for implementing various flexible optoelectronic devices and transistor applications.

Crystal Growth and Thermal Properties of Quasi-One-Dimensional van der Waals Material ZrSe3.

ZrSe3 with a quasi-one-dimensional (quasi-1D) crystal structure belongs to the transition metal trichalcogenides (TMTCs) family. Owing to its unique optical, electrical, and optoelectrical properties, ZrSe3 is promising for applications in field effect transistors, photodetectors, and thermoelectrics. Compared with extensive studies of the above-mentioned physical properties, the thermal properties of ZrSe3 have not been experimentally investigated. Here, we report the crystal growth and thermal and optical properties of ZrSe3. Millimeter-sized single crystalline ZrSe3 flakes were prepared using a chemical vapor transport method. These flakes could be exfoliated into microribbons by liquid-phase exfoliation. The transmission electron microscope studies suggested that the obtained microribbons were single crystals along the chain axis. ZrSe3 exhibited a specific heat of 0.311 J g-1 K-1 at 300 K, close to the calculated value of the Dulong-Petit limit. The fitting of low-temperature specific heat led to a Debye temperature of 110 K and an average sound velocity of 2122 m s-1. The thermal conductivity of a polycrystalline ZrSe3 sample exhibited a maximum value of 10.4 ± 1.9 W m-1 K-1 at 40 K. The thermal conductivity decreased above 40 K and reached a room-temperature value of 5.4 ± 1.3 W m-1 K-1. The Debye model fitting of the solid thermal conductivity agreed well with the experimental data below 200 K but showed a deviation at high temperatures, indicating that optical phonons could substantially contribute to thermal transport at high temperatures. The calculated phonon mean free path decreased with temperatures between 2 and 21 K. The mean free path at 2 K approached 3 μm, which was similar to the grain size of the polycrystalline sample. This work provides useful insights into the preparation and thermal properties of quasi-1D ZrSe3.

The Mechanism of the Photostability Enhancement of Thin-Film Transistors Based on Solution-Processed Oxide Semiconductors Doped with Tetravalent Lanthanides.

The applications of thin-film transistors (TFTs) based on oxide semiconductors are limited due to instability under negative bias illumination stress (NBIS). Here, we report TFTs based on solution-processed In2O3 semiconductors doped with Pr4+ or Tb4+, which can effectively improve the NBIS stability. The differences between the Pr4+-doped In2O3 (Pr:In2O3) and Tb4+-doped In2O3 (Tb:In2O3) are investigated in detail. The undoped In2O3 TFTs with different annealing temperatures exhibit poor NBIS stability with serious turn-on voltage shift (ΔVon). After doping with Pr4+/Tb4+, the TFTs show greatly improved NBIS stability. As the annealing temperature increases, the Pr:In2O3 TFTs have poorer NBIS stability (ΔVon are -3.2, -4.8, and -4.8 V for annealing temperature of 300, 350, and 400 °C, respectively), while the Tb:In2O3 TFTs have better NBIS stability (ΔVon are -3.6, -3.6, and -1.2 V for annealing temperature of 300, 350, and 400 ℃, respectively). Further studies reveal that the improvement of the NBIS stability of the Pr4+/Tb4+:In2O3 TFTs is attributed to the absorption of the illuminated light by the Pr/Tb4fn-O2p6 to Pr/Tb 4fn+1-O2p5 charge transfer (CT) transition and downconversion of the light to nonradiative transition with a relatively short relaxation time compared to the ionization process of the oxygen vacancies. The higher NBIS stability of Tb:In2O3 TFTs compared to Pr:In2O3 TFTs is ascribed to the smaller ion radius of Tb4+ and the lower energy level of Tb 4f7 with a isotropic half-full configuration compared to that of Pr 4f1, which would make it easier for the Tb4+ to absorb the visible light than the Pr4+.

Side chain engineering enhances the high-temperature resilience and ambient stability of organic synaptic transistors for neuromorphic applications

Organic synaptic transistors are considered to be one of the most promising device concepts for neuromorphic systems. However, repressively low memory retention and high-temperature instability greatly preclude the development and real-world application of organic synaptic transistors. Herein, we reported three conjugated polymers based on a bithiophene-thienothiophene backbone and the traditional ethylene glycol (EG) chains substituted by more hydrophobic propylene glycol (PG) and butylene glycol (BG) counterparts for three-terminal organic neuromorphic memory devices (TONMD). The resulting TONMD exhibits superior viability in ambient and high-temperature environments. BG chain-based p(b2T-TT) show ultra-long memory retention of over 103 s and large analog switching range (>10 ×) at 180 °C, which represents the record-high high-temperature resilience for reported TONMD to date. They also demonstrated excellent endurance of over 105 write-read operations and ultra-high ambient stability with 96 % of its original conductance after 3 months. Data of molecular dynamic simulations and microstructure show that the superior high-temperature resilience and ambient stability originate from more rigid conformation and stable morphology with the increased hydrophobicity of the PG and BG functionalities. Overall, rational design of oligoether side-chains will boost the device's dual high-temperature and ambient stability without compromising synaptic function and provide promising strategies for high-temperature neuromorphic applications.

Wettability Patternable Hybrid Polymer Films Based on TiO2 and Fluorinated Polymer for Bioelectronics Applications

AbstractOrganic–inorganic hybrid films based on TiO2 and a fluorinated polymer are fabricated, and their properties are investigated for bioelectronic applications. The analysis revealed that the preparation process requires (1) aging the blend solution before spin coating and (2) spin coating under humid conditions to obtain hydrophobic honeycomb‐like surfaces. Ultraviolet (UV) irradiation changed the surface wettability to hydrophilic, and patterned irradiation resulted in hydrophobic‐hydrophilic surface patterns. Patterned hybrid films have been used as substrates in both open microfluidics and organic electrochemical transistor applications. This multimodal application will open up an integrated biosensing device that collects body fluids and analyzes them on a single platform.

Modeling optical energy gap of thin film cuprous oxide semiconductor using swarm intelligent computational method

Cuprous oxide (Cu2O) is a p-type metal oxide semiconducting material with potential in photovoltaic and photocatalysis applications due to its excellent absorption capacity in visible region and tunable energy gap. Experimental synthesis and energy gap characterization of thin film cuprous oxide semiconductor with desired dopants and varying experimental conditions for enhanced photocatalytic as well as photovoltaic activities are laborious and consume appreciable precious resources. This work hybridizes particle swarm optimization method with support vector regression algorithm for computing energy gap of thin film cuprous oxide semiconductor using the thickness of thin film and distorted lattice parameter as descriptors. The predictions of swarm-based support vector regression (S-SVR) model are compared with estimates of stepwise regression (SR) model while S-SVR shows superior performance of 39.47 %, 36.20 % and 114.41 % on testing data samples over SR model using root mean square error (RMSE), mean absolute error (MAE) and correlation coefficient (CC), respectively. The developed S-SVR model is characterized with 0.9559 CC, 0.0586 MAE and 0.028 RMSE on the basis of training samples. The developed S-SVR and SR models were further validated using external data samples while the developed S-SVR demonstrates excellent agreement with the measured values. The convincing precision demonstrated by S-SVR model would be of indispensable significance in determining energy gap of cuprous oxide semiconductor (for photocatalytic applications in pollutant removal, solar cell, gas sensors and thin film transistors) with appreciable quickness and reduced cost coupled with experimental difficulty circumvention.

Newly Synthesized High‐k Polymeric Dielectrics with Cyclic Carbonate Functionality for Highly Stability Organic Field‐Effect Transistor Applications

AbstractOrganic field‐effect transistors (OFETs) with low‐voltage‐operating high‐stability are regarded as one of the key components of future electronics. However, it remains a challenge to enhance bias–stress stability, mechanical durability and environmental adaptability while reducing the operating voltage of the flexible OFETs. In this study, a new strategy of introducing high‐dipole‐moment groups into polymer side chains to enhance the intensity of polarization was proposed. This strategy can redirect cyclic carbonate side chains of high‐dipole groups under the action of electric fields and realize stable operation and efficient charge transfer. The experiments showed that high‐performance flexible OFETs were mainly attributed to the synthesized polymers through molecular structure designing which not only have high dielectric constant (k &gt; 5) and high electrical insulating property but also favor the growth of organic semiconductor films. The flexible OFETs still showed excellent mechanical flexibility, high electrical, thermal and humidity stability. In addition, highly OFETs were applied into a floating‐gate memory with fullerene (C60) embedded charge memory layer and an integrated one‐transistor‐one‐transistor memory cell. They exhibited excellent memory performance with a large memory window (8.5 V), current ratio (103), stable retention (2 × 104 s), cyclic endurance (200 cycles), multi‐level memory (over 4 levels) and non‐destructivity.

&amp;lt;italic&amp;gt;&amp;kappa;&amp;lt;/italic&amp;gt;-Ga&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;/GaN ferroelectric/polar semiconductor heterojunction for high electron mobility transistors

<p indent="0mm">Polar semiconductor heterostructures offer an alternative strategy to manipulate polarization towards advanced devices with engineered functionality and improved performance. Recently, Prof. Jiandong Ye’s group from Nanjing University reported on a novel <italic>κ</italic>-Ga₂O₃/GaN ferroelectric/polar heterojunction with switchable polarization under external electric field. A type-II band alignment is determined at the <italic>κ</italic>-Ga₂O₃/GaN polar hetero-interface, with charge dipoles induced by spontaneous polarization leading to the observed band bending. Benefiting from the large band discontinuity and ferroelectric manipulation, it is expected to realize the switching of the interfacial two-dimensional electron gas between accumulation and depletion states, which allows the rational design of <italic>κ</italic>-Ga₂O₃ ferroelectric/polar heterojunctions for the application of high electron mobility transistors, ferroelectric non-volatile memories and even ultra-low loss negative capacitance transistors.

Stretchable diketopyrrolopyrrole-based conjugated polymers with asymmetric sidechain designs for field-effect transistor applications

BackgroundThe asymmetric sidechain design has been recently proposed as a potential strategy to improve the mobility-stretchability property of conjugated polymers. In this study, the influences of the asymmetric sidechain designs on the mobility-stretchability properties of DPP-based conjugated polymers are investigated. Three asymmetric sidechain combinations based on a linear alkyl chain (C12), a carbosilane chain (Si), and a siloxane-terminated chain (SiO) are designed to synthesize three polymers, P(SiO-C12), P(Si-C12), and P(SiO-Si). MethodsAll polymers are synthesized via Stille coupling in a microwave reactor. Their basic properties including size exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) are analyzed. Their optical and electrochemical properties are characterized using UV-vis absorption and cyclic voltammetry (CV). The morphology of the polymer films is analyzed through optical microscopy (OM), atomic force microscopy (AFM), and grazing-incidence X-ray diffraction (GIXD). Lastly, the transistor characteristics are measured using a Keithley 4200-SCS semiconductor parameter analyzer (Keithley Instruments Inc.) inside a N2-filled glove box. Significant findingsThe asymmetric SiO/Si sidechain combination enables P(SiO-Si) possess the highest degree of bimodal packing orientation because their branched geometries impose a large steric hindrance to disrupt the chain packing. As benefitting from such bimodal packing orientation, P(SiO-Si) is shown to deliver the highest hole mobility value and the best mobility-stretchability property among these three polymers. It can persist 56.7% of the initial μh value after 800 cycles of 60% strain while P(SiO-C12) and P(Si-C12) can only maintain 2.4% and 4.1% of the initial value. Our results clearly highlight the advantage of the asymmetric SiO/Si sidechain combination on improving the mobility-stretchability property of the derived polymer.

High-Performance Thin-Film Transistor with Atomic Layer Deposition (ALD)-Derived Indium-Gallium Oxide Channel for Back-End-of-Line Compatible Transistor Applications: Cation Combinatorial Approach.

In this paper, the feasibility of an indium-gallium oxide (In2(1-x)Ga2xOy) film through combinatorial atomic layer deposition (ALD) as an alternative channel material for back-end-of-line (BEOL) compatible transistor applications is studied. The microstructure of random polycrystalline In2Oy with a bixbyite structure was converted to the amorphous phase of In2(1-x)Ga2xOy film under thermal annealing at 400 °C when the fraction of Ga is ≥29 at. %. In contrast, the enhancement in the orientation of the (222) face and subsequent grain size was observed for the In1.60Ga0.40Oy film with the intermediate Ga fraction of 20 at. %. The suitability as a channel layer was tested on the 10-nm-thick HfO2 gate oxide where the natural length was designed to meet the requirement of short channel devices with a smaller gate length (<100 nm). The In1.60Ga0.40Oy thin-film transistors (TFTs) exhibited the high field-effect mobility (μFE) of 71.27 ± 0.98 cm2/(V s), low subthreshold gate swing (SS) of 74.4 mV/decade, threshold voltage (VTH) of -0.3 V, and ION/OFF ratio of >108, which would be applicable to the logic devices such as peripheral circuit of heterogeneous DRAM. The in-depth origin for this promising performance was discussed in detail, based on physical, optical, and chemical analysis.

Study of nonmonotonic electron mobility due to influence of asymmetric structure parameters in pseudomorphic heterojunction field effect transistors

Nonmonotonic electron mobility is obtained in InxGa1-xAs/GaAs double quantum well pseudomorphic heterostructure field effect transistor by changing the structure parameters. We show that a rapid drop in mobility occurs at the point of resonance of sub-band states due to asymmetric variation of doping concentrations. The sub-band wave function distributions change significantly near the resonance and influence the sub-band mobilities through the scattering potentials, there by causing the dip in μ. The depth of nonlinearity in μ enhances by increasing the central barrier width and the difference between the well widths. On the other hand, variation of μ as a function of asymmetric change of well widths leads to a hump like raise in μ under unequal doping concentrations. Our results of nonlinear mobility can be utilized in low temperature transistor applications.

Direct Arylation: A Greener Synthesis of Anthraquinone-Naphthalene diimide-Based Small Chromophores for Applications in Organic Thin Film Transistors.

In this paper, we report the design and synthesis of three naphthalene diimide- (NDI) and anthraquinone- (AQ) based organic chromophores derived from direct arylation reactions; NDI-AQ, AQ-NDI-AQ and NDI-AQ-NDI. Compared to classic cross-coupling reactions, this method reduced the number of synthetic and purification steps. The chemical structures, photophysical and electrochemical properties of these molecules were characterized using UV-vis spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry (CV). The optoelectronic properties of the three dyes enabled the fabrication of organic thin film transistors (OTFTs). The fabricated OTFTs displayed good n-type semiconducting properties, with electron mobilities ( ) of 1.5-4.2×10-4 cm2 V-1 s-1 .

Highly-sensitive organic field effect transistor sensors for dual detection of humidity and NO2

Sensors based on organic field effect transistors have attracted extensive interests, but most sensors are applied to a single analyte detection. Herein, a facile strategy was proposed to optimize the growth of active layers by regulating the thickness of vanadyl-phthalocyanine (VOPc) films and carrying out the thermal annealing. Thanks to the improved film morphology and crystal properties, the carrier mobility of transistors reached 0.15 cm2V−1s−1, humidity and nitrogen dioxide (NO2) induced multi-parameter response of transistors could be considered as an efficient sensing approach. The sensitivity of threshold voltage reached 0.59 V/% RH ranging from 42%−82% RH. In addition, the gas sensing performance was systematically studied. Sensors based on 10 nm VOPc films achieved a 4710% response to 10 ppm NO2 gas, with a theoretical limit of detection down to 125.2 ppb, and the response current was improved by two orders of magnitude under the amplification effect of transistor. The obtained gas sensors also exhibited high repeatability after being stored at 90% ambient humidity. It was concluded that different charge carrier transfer mechanism in moisture and NO2 gas provided a simple idea for tunable applications of phthalocyanine-based transistors.

(Digital Presentation) Multimodal Encapsulation of p-SnOx to Engineer the Carrier Density for Thin Film Transistor Applications

It has been challenging to synthesize p-type SnOx (1≤x<2) and engineer the electrical properties such as carrier density and mobility due to the narrow processing window and the localized oxygen 2p orbitals near the valence band.We recently reported on the processing of p-type SnOx and an oxide-based p-n heterostructures, demonstrating high on/off rectification ratio (>103), small turn-on voltage (<0.5 V), and low saturation current (~1×10-10 A)1. In order to further understand the p-type oxide and engineer the properties for various electronic device applications, it is important to identify (or establish) the dominating doping and transport mechanisms. The low dopability in p-type SnOx, of which the causation is also closely related to the narrow processing window, needs to be mitigated so that the electrical properties of the material are to be adequately engineered 2, 3.Herein, we report on the multifunctional encapsulation of p-SnOx to limit the surface adsorption of oxygen and selectively permeate hydrogen into the p-SnOx channel for thin film transistor (TFT) applications. Time-of-flight secondary ion mass spectrometry measurements identified that ultra-thin SiO2 as a multifunctional encapsulation layer effectively suppressed the oxygen adsorption on the back channel surface of p-SnOx and augmented hydrogen density across the entire thickness of the channel. Encapsulated p-SnOx-based TFTs demonstrated much-enhanced channel conductance modulation in response to the gate bias applied, featuring higher on-state current and lower off-state current. The relevance between the TFT performance and the effects of oxygen suppression and hydrogen permeation is discussed in regard to the intrinsic and extrinsic doping mechanisms. These results are supported by density-functional-theory calculations. Acknowledgement This work was supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 20011028) by KRISS. K.N. was supported by Basic Science Research Program (NRF-2021R11A1A01051246) through the NRF Korea funded by the Ministry of Education. References Lee, D. H.; Park, H.; Clevenger, M.; Kim, H.; Kim, C. S.; Liu, M.; Kim, G.; Song, H. W.; No, K.; Kim, S. Y.; Ko, D.-K.; Lucietto, A.; Park, H.; Lee, S., High-Performance Oxide-Based p–n Heterojunctions Integrating p-SnOx and n-InGaZnO. ACS Applied Materials & Interfaces 2021, 13 (46), 55676-55686.Hautier, G.; Miglio, A.; Ceder, G.; Rignanese, G.-M.; Gonze, X., Identification and design principles of low hole effective mass p-type transparent conducting oxides. Nat Commun 2013, 4.Yim, K.; Youn, Y.; Lee, M.; Yoo, D.; Lee, J.; Cho, S. H.; Han, S., Computational discovery of p-type transparent oxide semiconductors using hydrogen descriptor. npj Computational Materials 2018, 4 (1), 17. Figure 1

High-Permittivity Dielectric for High-Performance Wide Bandgap Electronic Devices

In this presentation, we will review recent work on the integration of high permittivity dielectrics with wide and and ultra-wide bandgap semiconductor devices to obtain improved high power and high frequency applications. We will first discuss the use of such structures for vertical power devices. The high permittivity dielectrics help to reduce surface fields and therefore prevent tunnel leakage from Schottky barriers [1]. Insertion of high permittivity dielectrics can also enable better field termination in high voltage vertical devices [2]. We will discuss recent results using such high permittivity dielectrics in vertical device structures based on Gallium Oxide, leading to high vertical electric fields up to 5.7 MV/cm being sustained in the structure.We will discuss the application of these high permittivity dielectrics for three-terminal high frequency [3] and high voltage [4,5] wide bandgap transistor applications. In lateral transistors built from wide and ultra-wide bandgap semiconductors, gate breakdown and non-uniform electric fields lead to average device breakdown fields that are significantly lower than material limits. We will show how high permittivity dielectrics inserted between the gate and drain can prevent gate breakdown, and also create much more uniform electric field profiles. An analytical model to explain this will be presented and compared with 2-dimensional device simulations.Finally, we will show experimental results for lateral devices from the high Al-composition AlGaN [6], -Ga2O3[7], and AlGaN/GaN [8] material systems, where in each case, we are able to achieve state-of-art breakdown performance for devices such as lateral Schottky diodes and transistors. For example, we have achieved up to 8.3 MV/cm field in high Al-content AlGaN devices, >5.5 MV/cm in -Ga2O3-based transistors, and >3 MV/cm lateral electric field in AlGaN/GaN HEMTs. The high breakdown fields also enable us to achieve state-of-art switching figures of merit in these devices.The authors acknowledge funding from NNSA ETI Consortium, AFOSR GAME MURI Program (Program Manager Dr. Ali Sayir), AFOSR (Program Manager Dr. Kenneth Goretta) NSF ECCS- and the DARPA DREAM program (Program Manger Dr. YK Chen), managed by ONR (Program Manager Dr. Paul Maki) for support of the work.