Μm Gate Research Articles

Microwave Power Performance of AlGaN/GaN High‐Electron‐Mobility Transistor on Semi‐Insulating Mn‐Doped GaN Substrate

Herein, a DC and microwave performance of 2 μm gate length AlGaN/GaN high‐electron‐mobility transistor (HEMTs) on a Mn‐doped GaN substrate is demonstrated. The maximum drain current is 670 mA with a threshold voltage of 2.5 V and with good pinch‐off characteristics. The breakdown voltage of the HEMT is ≈80 V. The HEMT shows Δ8% current collapse while referenced HEMT on a SiC substrates which is fabricated simultaneously shows large Δ30% current collapse. When the HEMT with a gate width of 100 μm is tuned for the maximum output power at 2.4 GHz with a drain voltage of 30 V, it delivers 500 mW (5 W mm−1) with the maximum drain efficiency of 54%. These output performances are in good agreement with ideal class‐A operation performance. Therefore, it is concluded that the HEMT on Mn‐doped GaN substrates is promising for future microwave and millimeter‐wave high‐power transistors.

Developing Field Effect Transistor Sensors Based on DNA Probes to Detect Staphylococcus Lugdunensis Bacteria

The goal of this research is to work with an Electrical Double Layer (EDL)-gated Field Effect Transistor (FET) to detect the bacteria Staphylococcus lugdunensis, which can cause a variety of illnesses, including infections of the skin and soft tissues. In rare cases, Staphylococcus lugdunensis can be successfully identified using the combination of a positive catalase test, a negative tube coagulase test, a positive PYR test, and a positive ornithine decarboxylase test. We are employing an Electrical DoubleLayer (EDL)-gated Field Effect Transistor (FET) to speed up the procedure because this test is time consuming and requires a highly competent individual to perform. An ssDNA probe was developed, and effectively immobilized on a gold surface electrode sensor with a square surface, and due to hybridization with the cDNA at different concentrations, electrical signals were generated in the form of current.Our sensor was fabricated using photolithography where the gold electrode surface having 500 μm x 500 μm gate sensing area consisting of each individually addressable sensor arranged in a 1 x 8 array which is the extent gate was expose for immobilization purpose. The sensor was then subjectedto O2 plasma & HCl solution for surface cleaning and fluorescence image of baregold were taken Figure1(b).The Single-Stranded DNA comprising of fluorescent dye (FAM) at 3’ and thiol modifier at 5’ was drop-casted on the gold surface and was incubated for 24 hours at 24°C. After, it went through a washing process in order to remove the unbound ssDNA and fluorescence images were taken. We observed that intensity was higher than that of baregold which indicates that our probe has successfully immobilized on the gold surface Figure 1(b).Figure 1(a) represents the device that we designed. The system works with N-Channel Enhancement-Mode DMOS FET (VN10LP) in which a continuous drain voltage (3.5 V) was applied and the drain current which is the signal, were measured at two distinct gate bias voltage (2V and 3V). cDNA having quencher (BHQ1) at 5’ was diluted in different concentration namely 1fM, 10fM, 100fM and 1000fM. These cDNA with different concentrations were drop-casted on our sensor with Tris-EDTA (TE) buffer as the baseline and starting with lower concentration to higher concentration every after 12 seconds periodically where we record the change in signal as shown in Figure 1(c).After the electrical measurement, fluorescence image was taken and we can observe that it quenched which indicates that the cDNA and the immobilized ssDNA has successfully hybridized which give the signal change. Figure 1: (a) Surface Immobilization Principal Display in Extended Gate EDL BioFETs. (b)Fluorescence value comparison. (c) Plot showing the change in drain current over time for aptamersensors exposed to various cDNA concentrations. Figure 1

Impact of eliminating ungated access regions on DC and thermal performance of GaN-based MIS-HEMT

The impacts of eliminating access regions (AR) on DC and thermal performance of GaN-based MIS-HEMT have been studied using a device of 4 µm gate length. Nominal absence of ARs was achieved by a metal-organic chemical vapor deposition-regrown heavily n-doped GaN contact region extended to the two-dimensional electron gas (2DEG) channel (with sheet resistance as low as 14 Ω/ ◻ and ohmic contact resistance of 0.20 Ω⋅ mm) and 22-nm-thick AlN/Al2O3/HfO2 insulator layers acting as both gate dielectrics and sidewall spacers. As a result, a low knee voltage (2.5 V @ VGS = +2 V) comparable to deeply-scaled devices was attained, revealing the dominant role of ARs in knee voltages. High linearity at lower supply voltages (gate voltage swing of 7.3 V @ VDS = 5 V) and a faster GVS saturation trend with V DS increasing were observed, benefiting from the improved utility of applied lateral voltage. Moreover, a much lower thermal resistance compared to that of the conventional MIS-HEMT structure (146 vs. 202 K W−1) was extracted by a static-pulsed I-V measurement method. Simplified TCAD simulations were conducted to explain the underlying mechanisms, demonstrating that the enhanced surface heat flow covered by the gate metal as well as the more uniform electric field along the 2DEG channel accounts for the better capability of heat management in the device free of ARs. Our results indicate the size of DC and thermal performance enhancements obtained by eliminating ARs in a GaN-based MIS-HEMT structure.

Performance of normally off hydrogen-terminated diamond field-effect transistor with Al2O3/CeB6 gate materials

In this work, we demonstrate a hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with Al2O3/CeB6 gate materials. The CeB6 and Al2O3 films have been deposited by electron beam evaporation technique, sequentially. For the 4/8/12/15 μm gate length (LG) devices, the whole devices demonstrate distinct p-type normally off characteristics, and all the threshold voltage are negative; all the absolute values of leakage current density are 10−4 A/cm2 at a VGS of −11 V, exhibiting a relatively low leakage current density compared with CeB6 FETs, and this further demonstrates the feasibility of the introduction of Al2O3 to reduce the leakage current density; the maximum drain–source current density is −114.6, −96.0, −80.9, and −73.7 mA/mm, which may be benefited from the well-protected channel. For the 12 μm LG devices, the saturation carrier mobility is 593.6 cm2/V s, demonstrating a good channel transport characteristic. This work may provide a promising strategy for the application of normally off H-diamond FETs significantly.

Improvement of AlGaN/GaN High-Electron-Mobility Transistor Radio Frequency Performance Using Ohmic Etching Patterns for Ka-Band Applications.

In this paper, AlGaN/GaN high-electron-mobility transistors (HEMTs) with ohmic etching patterns (OEPs) "fabricated to improve device radio frequency (RF) performance for Ka-band applications" are reported. The fabricated AlGaN/GaN HEMTs with OEP structures were used to reduce the source and drain resistances (Rs and Rd) for RF performance improvements. Within the proposed study using 1 μm hole, 3 μm hole, 1 μm line, and 3 μm line OEP HEMTs with 2 × 25 μm gate widths, the small signal performance, large signal performance, and minimum noise figure (NFmin) with optimized values were measured for 1 μm line OEP HEMTs. The cut-off frequency (fT) and maximum oscillation frequency (fmax) value of the 1 μm line OEP device exhibited optimized values of 36.4 GHz and 158.29 GHz, respectively. The load-pull results show that the 1 μm line OEP HEMTs exhibited an optimized maximum output power density (Pout, max) of 1.94 W/mm at 28 GHz. The 1 μm line OEP HEMTs also exhibited an optimized NFmin of 1.75 dB at 28 GHz. The increase in the contact area between the ohmic metal and the AlGaN barrier layer was used to reduce the contact resistance of the OEP HEMTs, and the results show that the 1 μm line OEP HEMT could be fabricated, producing the best improvement in RF performance for Ka-band applications.

Fabrication and Switching Performance of 8 A–500 V D‐Mode GaN MISHEMTs

In this work, the design, fabrication, static device testing, and double‐pulse switching performance of multi‐finger D‐mode GaN metal–insulator–semiconductor high‐electron‐mobility transistors (MISHEMTs) on silicon are discussed. Utilizing an metal‐organic chemical vapor deposition‐grown GaN high‐electron‐mobility transistors stack with a superlattice buffer, field‐plated devices with a meandering gate geometry and a total gate width of 30 mm are fabricated. Plasma enhanced chemical vapor deposition SiNx is used as the gate dielectric, followed by an optimized bilayer SiNx passivation scheme. Devices with 100 μm gate width have an ON/OFF ratio of ≈108. They are analyzed for dynamic Ron (normalized Ron = 3 at 100 μs) and time‐dependent dielectric breakdown for gate reliability, resulting in a β value of 2.65 from the Weibull plot. Devices with a 30 mm gate width exhibit a maximum ON current of 8 A at zero gate voltage and a three‐terminal breakdown of ≈500 V. The devices are diced, wire‐bonded to a printed circuit board, and a double‐pulsed test is performed for switching transient characterization under clamped inductive load. The OFF‐state and ON‐state energy loss are estimated to be Eon = 14 μJ and EOFF = 27 μJ, respectively, when switched at 5 A, 50 V. In this study, the potential of GaN MISHEMTs with bilayer SiNx passivation for low‐power D‐mode switching applications (5 A, 50 V) is demonstrated.

Fabrication of Aptamer-based Field Effect Transistor Sensors for Detecting Mercury Ions

With the rapid development of industry, the pollution of the environment is becoming more and more serious. Among them, water pollution is one of the most serious problems, and polluted water sources often contain heavy metal ions such as mercury, chromium, lead, chromium, arsenic, etc. Which in turn affect our irrigation, breeding, food, and drinking, and finally cause physical harm. Mercury is still widely used today. For example, mercury and mercury compounds are used as catalysts in the plastics industry. Mercury is still widely used today. For example, mercury and mercury compounds are used as catalysts in the plastics industry. Some toxic pesticides also contain mercury. Mercury is used in daily life in fluorescent lamps, batteries, thermometers, medical amalgams, etc.Mercury pollution can be divided into two categories: organic mercury and inorganic mercury. Prolonged exposure to mercury can cause paralysis and a progressive loss of sense of touch, sight, hearing, or taste. Other more common neurological symptoms include memory and balance impairment, insomnia, hand tremors, and behavioral disturbances. Detecting the mercury content in water usually requires large-scale laboratory instruments for measurement, costing a lot of money and time.In this study, a specific aptamer is combined with a field-effect transistor to form an aptamer field-effect transistor by utilizing the properties of thymine-Hg(II)-thymine (T-Hg(II)-T) coordination chemical bonds. A highly selective and sensitive mercury ion sensor was achieved by using N-channel depletion-mode MOSFETs with APTAMER-modified gates. For the Aptamer-modified FET sensor, a detection limit of 0.2 PPM was achieved using a 500 μM × 500 μM gate sensing area. Biosensors realize reduced size, shorter detection speeds, cost savings, and high detection of limit sensors. Therefore, the determination of heavy metal ions in the environment by simple and easy-to-use instruments is of great significance for disease prevention. Figure 1

Исследование тепловых характеристик беспроволочной интеграции мощных СВЧ кристаллов

This paper presents the results of thermal analysis evaluation of two assembly techniques for high power microwave applications: conventional integration on metal carrier using solder preform and flip-chip mounting using Au-Sn system for SLID bonding as an interconnect layer to dielectric substrate. A high power GaN HEMT on SiC substrate with fabrication technology of 0.15 μm and total gate width 1.2 mm are used. The results of the flip-chip approach showed a 7.2% reduction in the overall thermal resistance of the assembly compared to conventional integration approach. Dependences of individual circuit elements on thermal parameters are determinated. Electrical equivalent circuit of thermal models of investigated constructions are obtained.

Study on the Point‐Contact Gate AlGaN/GaN High Electron Mobility Transistor with 0.1 μm Gate Length

The current collapse has been one of the most challenging problems in AlGaN/GaN high electron mobility transistors (HEMTs). In recent years, the virtual gate effect has been the most widely accepted cause of the current collapse effect. To effectively improve the current collapse effect and reduce the influence of the virtual gate effect on the device, a point‐contact gate AlGaN/GaN HEMT structure is proposed in this article. Tests show that the device has high transconductance, high cut‐off frequency, and good transfer, output, and breakdown characteristics. The maximum saturation drain current is 18 mA mm−1, the maximum transconductance is 200 mS mm−1, the breakdown voltage is 994 V, the maximum current gain is about 190 dB, and the cut‐off frequency is up to 206 GHz when the gate length and width are 0.1 μm × 0.001 μm. The experimental analysis shows that the point‐contact gate AlGaN/GaN HEMT structure shortens the gate length, thereby improving the virtual gate effect and effectively suppressing the current collapse effect, increasing the breakdown voltage of the device, and further improving the device performance, which lays the foundation for the future research of AlGaN/GaN HEMT.

Systematic characterization for RF small-signal parameter extraction of 28 nm FDSOI MOSFETs up to 110 GHz

A systematic RF characterization and small-signal parameter extraction for 28 nm fully depleted silicon on insulator (FDSOI) MOSFETs is presented in this paper. Two-step and hybrid de-embedding methodologies have been applied and compared for the accurate de-embedding of the on-chip RF test pads and access interconnect line elements. To avoid the accumulated error from the de-embedding for the small signal model of the FDSOI MOSFET, an error check criterion is adopted and utilized. Then, the complete extrinsic and intrinsic small-signal parameters of the device were extracted at multi-bias points based on the combination of direct extraction and linear regression approaches. For the extrinsic parameter extraction, the substrate-related parasitic elements and the extrinsic resistance components have been extracted. For the intrinsic small-signal parameter extraction, a complete model is presented and applied for direct extraction of the small-signal parameters. To verify the validity of the proposed modeling approach and the employed small-signal model, the S-parameters of a 28 nm FDSOI NMOS device with a 16 × 1 μm gate width were measured and characterized. From the comparison of the measured and modeled data, it is found that the proposed de-embedding and small-signal model provide an accurate characterization of RF parameter extraction for the FDSOI MOSFETs up to 110 GHz.

Fabrication of Aptamer-based Field Effect Transistor Sensors for Detecting Mercury Ions

This study presents an extended gate aptamer-based FET sensor for the detection of mercury ions in water. Heavy metal contamination in water can pose a severe threat to human health, and mercury ions are particularly dangerous as they can accumulate in the human body and cause serious health problems. The sensor provides high selectivity and sensitivity, even in the presence of other heavy metals, and achieves a detection limit of 0.2 ppm using a 500 μm x 500 μm gate sensing area. This cost-effective and efficient method can contribute to the mitigation of environmental pollution and the protection of public health.

Effects of GaN channel downscaling in AlGaN–GaN high electron mobility transistor structures grown on AlN bulk substrate

In this work, two series of AlGaN/GaN/AlN high electron mobility transistor (HEMT) heterostructures have been grown by molecular beam epitaxy on AlN bulk substrates. The effects of reduction in the GaN channel thickness as well as the AlGaN barrier thickness and composition on structural and electrical properties of the heterostructures have been studied. The material analysis involved high-resolution x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. In a first series of HEMT structures grown with an aluminum content of 30% in the AlGaN barrier, the channel downscaling results in a reduction in the GaN strain relaxation rate but at the expense of degradation in the mean crystal quality and in the electron mobility with a noticeable increase in the sheet resistance. An opposite trend is noticed for the three-terminal breakdown voltage of transistors, so that a trade-off is obtained for a 50 nm width GaN channel HEMT, which exhibits a sheet resistance of 1700 Ω/sq. with transistors demonstrating three-terminal breakdown voltage up to 1400 V for 40 μm gate to drain spacing with static on resistance Ron = 32 mΩ cm2. On the other hand, a second series of HEMT structures with high aluminum content AlGaN barriers and sub-10 nm GaN channels have been grown perfectly strained with high sheet carrier densities allowing to preserve sheet resistances in the range of 880–1050 Ω/sq.

Influence of Proton Irradiation Energy on Gate–Channel Low-Field Electron Mobility in AlGaN/GaN HEMTs

AlGaN/GaN high-electron-mobility transistors (HEMTs) with two different gate–drain distances (30 μm and 10 μm) were exposed to 1 MeV, 0.6 MeV, and 0.4 MeV protons at a fluence of 2.16 × 1012 cm−2. The gate–channel electron density and low-field mobility were obtained by measuring the capacitance–voltage characteristics and current–voltage characteristics. After proton irradiation, the gate–channel low-field electron mobility of the AlGaN/GaN HEMT with a 30 μm gate–drain distance increases and that with a 10 μm gate–drain distance decreases. It is studied and found that the mobility behavior is related to the polarization Coulomb field scattering, and the proton irradiation influences the intensity of the polarization Coulomb field scattering by changing the polarization/strain distribution in the barrier layer. The different gate–drain distances correspond to different variation trends of scattering intensity. The effect of 1 MeV protons on the barrier layer is smaller compared with 0.6 MeV and 0.4 MeV protons, so the mobility variation is smaller.

The effect of post-metal annealing on DC and RF performance of AlGaN/GaN HEMT

The effects of gate post-metal annealing (PMA) on the DC and RF characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The unannealed and post gate-metal annealed AlGaN/GaN HEMTs were fully fabricated using NANOTAM’s 0.5 μm gate length technology. PMA was performed at 450 °C for 10 min in nitrogen ambient for one of the wafers. The main focus was the effect of PMA on the electrical performance of HEMTs, including gate resistivity, transconductance, small-signal gain, output power (Pout), and threshold voltage (Vth) shift. It is achieved that HEMT with PMA has a gain of 18.5 dB, while HEMT without PMA shows a small-signal gain of 21.8 dB, as the PMA process increases the gate resistance (Rg) and decreases the transconductance (gm). The large-signal performance of the sample with PMA is better than the one without PMA, having an increase of 1.4 W/mm in Po ut from 20.9 W to 24.4 W. The transistor with PMA also demonstrates a reliable gate performance and stable Vth, and the wafer exhibits better uniformity.

Electrical properties of cerium hexaboride gate hydrogen-terminated diamond field effect transistor with normally-off characteristics

Fabrication of hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with low work function cerium hexaboride (CeB6) gate material has been successfully performed. For the 8 μm gate length device, the threshold voltage (VTH) is extracted to be −0.46 V, demonstrating a normally-off characteristics. The maximum drain source current density (IDmax) is −83.8 mA/mm, and the competitive IDmax may be ascribed to the undamaged two-dimensional hole gas channel. The interface state density (Dit) is evaluated to be 1.93 × 1012 cm−2·eV−1, and the relatively low value may be attributed to the uncontaminated interface in gate material. This work provides a promising strategy to realize normally-off H-terminated diamond FET for fail-safety and energy-efficient power electronic devices.

RF performance enhancement in sub-μm scaled β-Ga2O3 tri-gate FinFETs

In this Letter, we report on the enhanced radio frequency (RF) performance in sub-micrometer scaled β-Ga2O3 tri-gate FinFETs. With a 200-nm-thick β-Ga2O3 bulk channel and a 0.35 μm gate length, the FinFETs exhibit an improved current-gain cutoff frequency of 5.4 GHz and a maximum oscillation frequency of 11.4 GHz, which are 20% and 58% improved with respect to the planar counterpart, respectively. The improved RF performance results from the enhanced gate control capability and the suppressed short-channel effects, as evidenced by the improved pinch-off characteristics, the improved transconductance, and the suppressed output conductance. It suggests that the tri-gate multi-fin architecture is a promising strategy to break the scaling limitation of the gate-channel aspect ratio toward high-performance β-Ga2O3 RF MOSFETs.

Simulation-based study of current gain peaks h 21 at low gate bias in AlGaN/GaN HEMTs * *This work was supported by Defence Research and Development Organization (DRDO), Government of India under Grant JATC-EMDTERA-06.

In this article, we have presented the effect of low gate bias on short circuit current gain h 21 beyond cutoff frequency in AlGaN/GaN HEMT. A small-signal model, based on its intrinsic and extrinsic parameter values, is simulated beyond the cutoff frequency to analyze its peak. From the study, it has been observed that the first peak of short circuit current gain has the resonance frequency as well as magnitude variation with respect to low gate voltages. Whereas, the second peak of the current gain h 21 has only magnitude dependency on low gate voltage with fixed resonance frequency. The relevance of this study is to provide a comprehensive insight to the circuit designer to efficiently consider these windows of current gain peak beyond the cutoff frequency into their design. For this analysis, we have taken AlGaN/GaN HEMT device with a channel length of 0.8 μm and 2 × 200 μm2 gate width. A measured S-parameter data up to 40 GHz at low gate bias is used to extract the model parameters.

DC Modeling of 4H-SiC nJFET Gate Length Reduction at 500°C

The development of robust, high-performance integrated circuits (ICs) will enable numerous potential NASA missions of current interest, including long-duration robotic missions exploring the 460°C surface of Venus. Currently, NASA is looking towards SiC-based devices to provide such a solution. However, the current NASA silicon carbide (SiC) JFET device with a channel length of 6 μm (recently fabricated Gen. 11 ICs) limits mission-relevant circuit capabilities. In this study, we combined experiments with simulations to explore two straightforward fabrication strategies (shallow n−and extended n+) to reduce the SiC JFET channel length while maintaining the turn-off behavior needed to realize 500°C circuit operation. COMSOL Multiphysics was used to simulate the transfer characteristics and maximum potential below the gate of a 4H-SiC nJFET at 500°C, and a 1 μm gate length nJFET with turn-off performance comparable to the state-of-the-art is suggested.

Small‐signal modeling of microwave transistors using radial basis function artificial neural network‐comparison of different methods for spread constant determined

This article presents a high-precision modeling method to build a small signal model of GaAs pseudomorphic high electron mobility transistor (pHEMT) by using a radial basis function artificial neural network (RBF ANN). Both the RBF ANN Method 1 that uniformly distributed spread constant (SC) in the given range and Method 2 that increasingly changed SC with a chosen step have been modeled in this work. Compared with the l RBF ANN Method 1, the RBF ANN method 2 can automatically obtain the optimal ANN corresponding to the SC. The RBF ANN method 2 is developed for S-parameters model and equivalent circuit parameters (ECPs) model of HEMTs. S-parameters model establishes S-parameters versus bias, temperature and frequency, while the ECPs model establishes ECPs versus bias and temperature. To validate the capability of the RBF ANN in small signal modeling of GaAs pHEMTs, measured and modeled data of S-parameters model and ECPs model of a 4 × 75 μm gate width, 0.15 μm gate length GaAs pHEMT are compared, and very good agreement is achieved up to 50 GHz. For the S-parameters model, the average error of the method 2 is improved by about 20% at the temperature of −20°C, 25°C, and 85°C. For the ECPs model, the average error of the method 2 is 80% higher than that of the method 1.

Diamond MOSFET with MoO3/Si3N4 doubly stacked gate dielectric

A hydrogen terminated diamond MOSFET with MoO3/Si3N4 doubly stacked gate dielectrics was fabricated on a single crystalline diamond sample. Compared to a device with single MoO3 layer gate dielectrics, the device performance was improved due to the improvement in the gate voltage, which benefited from the doubly stacked gate dielectric. The device with 4 μm gate length shows a maximum output current of 118.67 mA/mm and an ultra-low resistance of 36.15 Ω mm at the gate voltage of −5 V. In addition, the device shows a maximum transconductance of 35 mS/mm. These results indicate that the dielectric with high work function has high potential to achieve a high-performance diamond MOSFET.