Metal Oxide Semiconductor High Electron Research Articles

GaN-HEMT Performance Enhancement

In this work, a simulation analysis and calibration are carried out to improve the performance of AlGaN/GaN- MOSHEMTs (Metal-Oxide Semiconductor High Electron Mobility Transistors). The effect of the AlGaN layer thickness, gate length, Al mole fraction, and the interface traps on the electrical performance of the device has been presented. Device simulations have been done using Sentaurus technology computer-aided design (TCAD). The simulations and analysis show better drain current, transconductance, and cut-off frequency performance. The maximum cut-off frequency shown by the proposed HEMT device is 45.7 GHz at 100-nm gate length. Good transcoductance has been obtained by scaling down the gate length of the device, which is ascribed to the present two-dimensional electron gas (2DEG) density that supports upgrading the output current. Higher drain current is achieved without using acceptor-like traps in the Al2O3/AlGaN interface. Results show that the Al2O3/AlGaN/GaN-based MOSHEMT is a promising device for high-frequency and power electronic applications.

Sensitivity estimation of biosensor in a tapered cavity MOSHEMT

The present research provides a comprehensive investigation of the structural modification at the cavity under the gate (CUG) on the metal oxide semiconductor high electron mobility transistor (MOSHEMT)-based biosensor by projecting its basic figures of merit (FOMs). The effect of a tapering dielectric on the sensitivity of the biosensor has not been extensively investigated in many research efforts. Therefore, to account for the larger binding surface, the current study considers a wide range of permittivity of the biomolecules from 1 to 10, using the dielectric modulation technique in the tapered cavity. Various cavities are analysed to enhance the sensitivity. The findings indicate that the presence of biomolecules causes a considerable fluctuation in the drain current, threshold voltage, on-current, off-current, channel potential, and oxide capacitance. It has also been estimated how various fill percentages and charged and neutral biomolecules affect the device’s sensitivity. The tapered dielectric MOSHEMT offered an on-current sensitivity and threshold voltage sensitivity of 1.25 and 0.889 for neutral biomolecule (k = 8) and 0.562 and 2.23 for positively charged biomolecule respectively. Thus, tapering of the oxide does offer better sensitivities that can be exploited for biosensing applications.

Device optimization and sensitivity analysis of a double-cavity graded MgZnO/ZnO MOSHEMT for biomolecule detection

The detailed analytical model of biosensing parameters was proposed for a double-cavity graded MgZnO/ZnO metal oxide semiconductor high electron mobility transistor (MOSHEMT) with cap layer-based biosensor including transfer characteristic, output characteristic, change in cut-off voltage ( ΔVoff ), transconductance ( gm ), sensitivity, and selectivity. A thorough investigation of dielectric modulation in a double nanogap cavity under the gate was conducted with a focus on improving the sensing characteristics of a MOSHEMT to indicate the presence of biomolecules like Uricase, Streptavidin, Protein, and ChOx. The dielectric modulation and the Poisson equation were used to determine the effective capacitance and cut-off voltage in the cavity region. Consequently, the changes in the cut-off voltage and the drain current of the device were used as the sensing metrics for the detection of biomolecules in the cavity regions. It was found that the proposed graded MgZnO/ZnO MOSHEMT-based biosensor demonstrates a higher change in cut-off voltage and drain current in comparison to the previous works, suggesting higher sensitivity for biomolecules.

Numerical study of T-Gate AlGaN/AlInGaN/GaN MOSHEMT with Single and Double Barrier for THz Frequency Applications

This paper presents a comprehensive investigation into the DC analog and AC microwave performance of a state-of-the-art T-gate double barrier AlGaN/AlInGaN/GaN MOSHEMT (Metal Oxide Semiconductor High Electron Mobility Transistor) implemented on a 4H-SiC substrate. The study involves meticulous numerical simulations and an extensive comparison with a single barrier design, utilizing the TCAD-Silvaco software. The observed disparity in performance can be attributed to the utilization of double barrier technology, which enhances electron confinement and current density by augmenting the polarization-induced charge during high-frequency operations. Remarkably, when compared to the single barrier design, the double barrier MOSHEMT exhibits a notable 15% increase in drain current, a 5% increase in transconductance, and an elevated breakdown voltage (VBR) of 140 V in E-mode operation. Furthermore, the radio frequency analysis of the double barrier device showcases exceptional performance, setting new records with a maximum oscillation frequency (fmax) of 1.148 THz and a gain cutoff frequency (ft) of 891 GHz. These impressive results obtained through deck-simulation affirm the immense potential of the proposed double barrier AlGaN/AlInGaN/GaN MOSHEMT for future applications in high-power and terahertz frequency domains.

Drain current sensitivity analysis using a surface potential-based analytical model for AlGaN/GaN double gate MOS-HEMT

In this research, a surface potential-based drain current model for an AlGaN/GaN symmetrical double-gate metal oxide semiconductor high electron mobility transistor (DG-MOSHEMT) is proposed and used to detect label-free biomolecules for the first time. The model is applied for a nanocavity-based DG-MOSHEMT and works on the concept of dielectric modulation to detect biomolecules like uricase, urease, streptavidin, protein, biotin, ChOx, and APTES(3-aminopropyltriethoxysilane). The performance indicators, such as a change in drain ON current (ΔION), drain current sensitivity (SION), transconductance sensitivity (Sgm), and output conductance sensitivity (Δgd), are used to assess the device's efficacy. Numerical simulations are conducted to verify the model's accuracy and quantify its sensitivity. The DG-MOSHEMT device elicited exceptional sensitivity towards the uricase biomolecule, surpassing all other analytes tested, with SION = 0.328, Sgm = 0.197, and Δgd = 28.1 mS/mm. Furthermore, the model considers the contribution of the first two sub-bands of the quantum well and competently captures the fluctuation in drain ON current and sensitivity. A comprehensive sensitivity analysis of the drain current is conducted by altering physical parameters such as cavity length, thickness, gate length and barrier layer thickness. Notably, the sensitivity SION is significantly improved with cavity length and thickness for the optimized AlGaN barrier layer.

Threshold and surface potential-based sensitivity analysis of symmetrical double gate AlGaN/GaN MOS-HEMT including capacitance effects for label-free biosensing

This paper presents an analytical framework, based on the surface potential for a symmetrical double-gate AlGaN/GaN Metal oxide semiconductor high electron mobility transistor (DG-MOSHEMT) equipped with an embedded nanocavity tailored for biomedical sensing applications. The proposed model operates on the dielectric modulation principle and meticulously scrutinizes the device’s performance using critical sensing metrics such as threshold voltage shift (ΔVth), threshold voltage sensitivity (SVth), surface potential shift (ΔΨs,0), and surface potential sensitivity (SΨs,0). The model demonstrates remarkable sensitivity in detecting minute biomolecule variations, explicitly focusing on streptavidin, uricase, protein, and ChOx as the target biomolecules. Additionally, analytical equations based on surface potential are established to accurately determine gate charges (QG), gate-to-drain capacitance (CGD), and gate-to-source capacitance (CGS). The thorough investigation of biomolecule effects on gate capacitance holds paramount significance as it plays a vital and profound role in dictating device performance. Furthermore, variations in nanocavity length, AlGaN layer thickness, and oxide layer thickness are explored to understand their influence on ΔVth and SVth. The proposed model exhibits a remarkable improvement in both threshold voltage shift and sensitivity compared to the single MOS-HEMT. Notably, it demonstrates substantial enhancements of 2.06, 1.72, 1.49, and 1.5 times for the uricase, streptavidin, protein, and ChOx biomolecules, in terms of threshold voltage shift, and impressive improvements of 10.7%, 14.5%, 18.2%, and 50% for the same biomolecules, respectively, in terms of threshold voltage sensitivity, surpassing the previous findings. Uricase exhibited the most significant shift in surface potential (ΔΨs,0) among the analyzed biomolecules, with a value of 100 mV mm−1 and a sensitivity (SΨs,0) of 0.44. In contrast, ChOx showed a modest (ΔΨs,0) of 24 mV mm−1 with a relative sensitivity (SΨs,0) value of 0.108. Increasing nanocavity length and oxide layer thickness positively contribute to ΔVth and SVth. Moreover, while an increase in AlGaN layer thickness enhances ΔVth performance, its impact on SVth is minimal.

AlGaN/GaN Metal Oxide Semiconductor High-Electron Mobility Transistors with Annealed TiO2 as Passivation and Dielectric Layers.

This paper reports on improved AlGaN/GaN metal oxide semiconductor high-electron mobility transistors (MOS-HEMTs). TiO2 is used to form the dielectric and passivation layers. The TiO2 film is characterized using X-ray photoemission spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). The quality of the gate oxide is improved by annealing at 300 °C in N2. Experimental results indicate that the annealed MOS structure effectively reduces the gate leakage current. The high performance of the annealed MOS-HEMTs and their stable operation at elevated temperatures up to 450 K is demonstrated. Furthermore, annealing improves their output power characteristics.

Impact of InGaN notch on sensitivity in dielectric modulated dual channel GaN MOSHEMT for label-free biosensing

The effect of InGaN notch on sensitivity and Dielectric Modulated (DM) Double Heterojunction (DH) dual channel AlGaN/GaN/InGaN/GaN MOSHEMT (Metal Oxide Semiconductor High Electron Mobility Transistor) for detecting the label-free biomolecules has been investigated in this paper. Biomolecules can be inserted into the nanocavity formed by etching the insulating layer under the gate electrode. The insulator (Al2O3) as a dielectric improves the drive current and device sensitivity because of low leakage and high scalability. In this proposed structure, the presence of InGaN notch increases the carrier confinement in the channel, thereby improving the device sensitivity. The device is simulated using Sentaurus TCAD, and the results show a significant increase in drain current (IDS), up to 335 mA/mm. The optimization of the device parameters exhibits a high sensitivity (∼74%), making it suitable for precise label-free biosensing.

Plasma induced damage on AlGaN/GaN heterostructure during gate opening for power devices

During the fabrication of metal oxide semiconductor high electron mobility transistor based on AlGaN/GaN heterostructure, gate patterning is recognized as the most critical step that can lead to electrical degradation of the transistor. In this work, we performed the SiN cap layer plasma etching processes by two fluorine-based plasma processes (SF6/Ar and CHF3/CF4/Ar) with low (≈15 eV) and high (≈260 eV) ion energies. Moreover, we investigate the postetching treatment using a KOH solution in order to restore the quality of the AlGaN barrier surface after etching. The objective of this article is to evaluate the AlGaN barrier surface damage after the listed plasma etching processes and postetching strategies by using quasi-in situ angle-resolved x-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscope. Accordingly, it is found that both high ion energy plasma processes lead to a significant stoichiometric change and modification of the AlGaN barrier layer into a 1.5 nm F-rich AlGaNFx subsurface reactive layer. The decrease in ionic energy leads to a decrease in the SiN etch rate and a significant improvement in the SiN/AlGaN etch selectivity (which becomes infinite) for both plasma chemistries. Moreover, the decrease in ion energy decreases the depth of the modification (about 0.5 nm) and reduces the stochiometric change of the AlGaN barrier layer. However, both low and high ion energy SF6/Ar plasma lead to 0.8 eV Fermi level shift toward the valence band. Furthermore, the KOH postetching treatment demonstrates complete and effective removal of the AlGaNFx subsurface reactive layer and restoration of the surface properties of the AlGaN layer. However, this removal leads to AlGaN recesses that are correlated to the thickness of the reactive layer formed during the etching.

Gate dielectric layer mitigated device degradation of AlGaN/GaN-based devices under proton irradiation

In this study, the simulations of AlGaN/GaN-based devices, including AlGaN/GaN high electron mobility transistor (HEMT), Al2O3 metal–oxide–semiconductor high electron mobility transistor (MOSHEMT), and SiNx metal–insulator–semiconductor high electron mobility transistor (MISHEMT), were studied to investigate the degradation mechanism after proton irradiation. The vacancies produced by proton irradiation, especially Ga vacancy (VGa), are found to be responsible for the device degradation by carrier removal and mobility degradation, which directly influence the saturation drain current and maximum transconductance of AlGaN/GaN-based devices. Furthermore, AlGaN/GaN HEMTs with gate dielectrics (Al2O3, SiNx) exhibit better irradiation resistance than traditional AlGaN/GaN HEMTs, which produce fewer vacancies at the channel after proton irradiation. Al2O3 MOSHEMTs also show better performance than SiNx MISHEMTs in resisting proton damage. Therefore, a high-quality dielectric layer is a key factor to improve the reliability of AlGaN/GaN-based devices after proton irradiation.

Performance improvement in NiO x -based GaN MOS-HEMTs

We have illustrated the thermal oxidation of Ni as gate dielectrics to improve the characteristics of GaN-based metal oxide semiconductor high electron mobility transistors (HEMTs). The oxide is formed by a pre-deposition of a thin film followed by oxidation in pure O2 ambient. The formation and thickness of the oxides are confirmed through x-ray photoelectron spectroscopy and transmission electron microscopy. NiO x is found to have an energy band gap of 3.7 eV determined using O 1s energy loss spectra. NiO x is found to provide negative (1.7 eV) valence band offsets with AlGaN. The potential use of the oxides has been confirmed by the significant improvement in drive current, transconductance, subthreshold swing, unity current gain frequency, and gate current leakage over the Schottky barrier HEMTs (SB-HEMTs). We have observed a positive shift in threshold voltage for NiO x -based gate dielectric devices compared to that of the SB-HEMTs.

Performance Comparison of Lattice-Matched AlInN/GaN/AlGaN/GaN Double-Channel Metal–Oxide–Semiconductor High-Electron Mobility Transistors with Planar Channel and Multiple-Mesa-Fin-Channel Array

In this work, Al0.83In0.17N/GaN/Al0.18Ga0.82N/GaN epitaxial layers used for the fabrication of double-channel metal–oxide–semiconductor high-electron mobility transistors (MOSHEMTs) were grown on silicon substrates using a metalorganic chemical vapor deposition system (MOCVD). A sheet electron density of 1.11 × 1013 cm−2 and an electron mobility of 1770 cm2/V-s were obtained. Using a vapor cooling condensation system to deposit high insulating 30-nm-thick Ga2O3 film as a gate oxide layer, double-hump transconductance behaviors with associated double-hump maximum extrinsic transconductances (gmmax) of 89.8 and 100.1 mS/mm were obtained in the double-channel planar MOSHEMTs. However, the double-channel devices with multiple-mesa-fin-channel array with a gmmax of 148.9 mS/mm exhibited single-hump transconductance behaviors owing to the better gate control capability. Moreover, the extrinsic unit gain cutoff frequency and maximum oscillation frequency of the devices with planar channel and multiple-mesa-fin-channel array were 5.7 GHz and 10.5 GHz, and 6.5 GHz and 12.6 GHz, respectively. Hooge’s coefficients of 7.50 × 10−5 and 6.25 × 10−6 were obtained for the devices with planar channel and multiple-mesa-fin-channel array operating at a frequency of 10 Hz, drain–source voltage of 1 V, and gate–source voltage of 5 V, respectively.

Influence of back barrier layer thickness on device performance of AlGaN/GaN MOS-HEMT

In this work, we have performed the influence of back barrier layer thickness variation on AlGaN/GaN Metal Oxide Semiconductor High Electron Mobility Transistor (MOS-HEMT) device with 0.5 µm Schottky gate length. The AlGaN back barrier layer presented increases the conduction band with respect to GaN channel layer so that more no of electron confinement into the GaN channel layer and improve the high-frequency performance. The effect of the back-barrier layer thickness is performed by using 2-D TCAD Atlas Silvaco numerical simulation tool by taking Hydrodynamic mobility model. Due to a large amount of two-dimensional electron gas (2-DEG) density at the AlGaN/GaN heterointerface of the MOS-HEMT device higher drain current density is obtained. The 2-D simulation is carried out with a variation of back barrier layer thickness for various device parameter such as transfer characteristics (Id-Vg), drain current with a drain voltage (Id-Vd), transconductance (gm), drain induced barrier lowering (DIBL), conduction band energy and electron concentration into the channel. In this simulation, we have also performed the RF performance like a gate to source capacitance (Cgs) and current gain cut-off frequency of AlGaN/GaN MOS-HEMT device. The results obtained by variation of AlGaN back barrier layer thickness can be a better solution in future analog and RF device application. Copyright © 2018 VBRI Press.

Modified Small Signal Circuit of AlGaN/GaN MOS-HEMTs Using Rational Functions

Conventional lumped small signal circuit (SSC) models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are derived from the low frequency portion of the experimentally measured Y-parameters. Consequently, these models cannot faithfully capture the high frequency behavior of the device. In this work, modified SSC models of AlGaN/GaN MOS-HEMTs are developed by fitting the entire broadband measured Y-parameters of the device with rational functions. These rational functions are then physically realized using additional passive circuit elements added to the conventional SSC model. The accuracy of the proposed SSC models can be improved by increasing the order of the rational functions. The proposed models are demonstrably more accurate than the conventional SSC models in estimating the higher order poles and zeroes present in the experimentally measured Y-parameters of AlGaN/GaN MOS-HEMTs.

Low Subthreshold Slope AlGaN/GaN MOS-HEMT with Spike-Annealed HfO2 Gate Dielectric.

AlGaN/GaN metal-oxide semiconductor high electron mobility transistors (MOS-HEMTs) with undoped ferroelectric HfO2 have been investigated. Annealing is often a critical step for improving the quality of as-deposited amorphous gate oxides. Thermal treatment of HfO2 gate dielectric, however, is known to degrade the oxide/nitride interface due to the formation of Ga-containing oxide. In this work, the undoped HfO2 gate dielectric was spike-annealed at 600 °C after the film was deposited by atomic layer deposition to improve the ferroelectricity without degrading the interface. As a result, the subthreshold slope of AlGaN/GaN MOS-HEMTs close to 60 mV/dec and on/off ratio>109 were achieved. These results suggest optimizing the HfO2/nitride interface can be a critical step towards a low-loss high-power switching device.

Influence of Graded AlGaN sub-channel over the DC and Breakdown characteristics of a T-gated AlGaN/GaN/AlInN MOS-HEMT

The impact of graded Al0.05Ga0.95N sub-channel over the DC characteristics of AlGaN/GaN/AlInN Metal Oxide Semiconductor-High Electron Mobility Transistor (MOS-HEMT) has been investigated here. By placing a field plate over the gate region and forming a T-gated structure, the breakdown characteristics are examined using Sentaurus Technology Computer-Aided Design (TCAD) simulation tool. An analytical study is carried out into the evaluation of various device parameters like drain current, transconductance and threshold voltage. RF parameters like cut-off frequency and gain has also been examined. Various physical models such as hydrodynamic, thermodynamic, piezoelectric polarization, impact ionization models are considered. HfO2 as an oxide layer directly influences the charge confinement near the Two-Dimensional Electron Gas (2DEG), thereby causing a positive shift in the threshold voltage of the device. T-gated formation of the gate helped in enhancing the breakdown voltage of the device to nearly 750 V. A maximum current drive of 1.79 A/mm mm was obtained for the proposed device, nearly 24% improvement from the conventional Composite-channel (CC) HEMT. The current outcomes and the produced frequency characteristics determines the linearity enhancement occurred in the device, caused due to the graded AlGaN sub-channel below the GaN channel layer. The trade-off between specific on-resistance and breakdown voltage is well preserved by employing a T-gated structure with low normal gate length. The outcomes prove the device to be a prime contender for high power switching as well as large signal applications.

Observations regarding deep-level states causing p-type doping in AlTiO gate and positive threshold voltage shift in AlGaN/GaN high electron mobility transistors

Application of ternary oxides has emerged as a potential enabler to achieve enhancement mode (normally-OFF) operation in AlGaN/GaN high electron mobility transistors (HEMTs). However, it is not well understood what leads to the 2-Dimensional Electron Gas depletion or positive threshold voltage shift by the integration of these oxides in the gate stack. In this work, an electro-optical experiment-based method is used to probe the underlying mechanism. For experiments, AlGaN/GaN metal–oxide–semiconductor high electron mobility transistors with gate stack consisting of AlTiO (ternary p-type oxide), Al2O3, TiO2 (undoped binary oxides), and NiO (conventional p-type oxide) are used. Optical exposure with wavelengths falling in the UV regime (365 nm) was found to induce a negative threshold voltage shift in AlTiO based devices. Experimentation on different GaN buffer stacks, different gate oxides, and selective UV exposure only to the gate region established the phenomenon to be governed by properties of the ternary oxide. This was further confirmed by the fact that the negative threshold voltage shift with UV exposure was proportional to the positive shift achieved as a function of Al% in AlTiO. The negative shift was found to be due to de-ionization of deep-level negative states in AlTiO, which resulted from the presence of Al at Ti sites ([Al]Ti′). These negatively ionized deep-level states at room temperature result in p-type doping of the oxide, leading to the positive threshold voltage shift in AlTiO gate based HEMTs when compared with HEMTs with Al2O3 or TiO2 as gate oxide.

Epi-Gd₂O₃-MOSHEMT: A Potential Solution Toward Leveraging the Application of AlGaN/GaN/Si HEMT With Improved I ON/I OFF Operating at 473 K

In this article, we report the temperature-dependent transistor characteristic of Epi-Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /AlGaN/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT) and compare its properties with that of AlGaN/GaN metal-Schottky high electron mobility transistor (HEMT) grown on 150 mm Si (111) substrate. Introducing an epitaxial single crystalline Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> between the metal gate and AlGaN barrier not only improves the gate leakage current significantly but also enhances its thermal stability. We observe that there is no significant change in the gate leakage current even at 473 K compared to that measured at room temperature (RT) (298 K), and this is also evident in the transistor's subthreshold behavior at 473 K. We have determined the electric field within the Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as well as AlGaN and investigated the leakage conduction mechanism through Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . The I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> OFF</sub> of the transistor was measured as high as ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> even at 473 K with the lowest V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> shift (91.4 mV) with temperature. Our measurements also confirm the presence of polar optical phonon scattering, which directly affects the 2-D electron gas (2DEG) mobility at high temperatures and thus the electrical characteristics of HEMT and MOSHEMT.

Study of Effective Graded Oxide Capacitance and Length Variation on Analog, RF and Power Performances of Dual Gate Underlap MOS-HEMT

Comparative analysis of a Symmetric Heterojunction Underlap Double Gate (U-DG) GaN/AlGaN Metal Oxide Semiconductor High Electron Mobility Transistor (MOS-HEMT) on varying the effective capacitance by using different oxide materials on source and drain sides, and determination of optimum length of oxides for the superior device performance has been presented in this work. This paper shows a detailed performance analysis of the Analog Figure of Merits (FoMs) like variation of Drain Current (IDS), Transconductance (gm), Output Resistance (R0), Intrinsic Gain (gmR0), RF FoMs like cut-off frequency (fT), maximum frequency of oscillation (fMAX), gate to source resistance (RGS), gate to drain resistance (RGD), gate to drain capacitance(CGD), gate to source capacitance (CGS) and total gate capacitance (CGG) using Non-Quasi-Static (NQS) approach. Power analysis includes Output power (Pout), Gain in dBm and power output efficiency (POE) have been studied. Studies reveal that the device with higher dielectric material towards source side shows superior performance. On subsequently changing the proportion of two oxides in a layer by varying length, it is observed that as the proportion of oxide increases the device demonstrates more desirable Analog and RF characteristics while best power performance is obtained from device with equal lengths of HfO2 and SiO2.

Performance Enhancement in N2 Plasma Modified AlGaN/AlN/GaN MOS-HEMT Using HfAlOX Gate Dielectric with Γ-Shaped Gate Engineering.

In this paper, we have demonstrated the optimized device performance in the Γ-shaped gate AlGaN/AlN/GaN metal oxide semiconductor high electron mobility transistor (MOS-HEMT) by incorporating aluminum into atomic layer deposited (ALD) HfO2 and comparing it with the commonly used HfO2 gate dielectric with the N2 surface plasma treatment. The inclusion of Al in the HfO2 increased the crystalline temperature (~1000 °C) of hafnium aluminate (HfAlOX) and kept the material in the amorphous stage even at very high annealing temperature (>800 °C), which subsequently improved the device performance. The gate leakage current (IG) was significantly reduced with the increasing post deposition annealing (PDA) temperature from 300 to 600 °C in HfAlOX-based MOS-HEMT, compared to the HfO2-based device. In comparison with HfO2 gate dielectric, the interface state density (Dit) can be reduced significantly using HfAlOX due to the effective passivation of the dangling bond. The greater band offset of the HfAlOX than HfO2 reduces the tunneling current through the gate dielectric at room temperature (RT), which resulted in the lower IG in Γ-gate HfAlOX MOS-HEMT. Moreover, IG was reduced more than one order of magnitude in HfAlOX MOS-HEMT by the N2 surface plasma treatment, due to reduction of N2 vacancies which were created by ICP dry etching. The N2 plasma treated Γ-shaped gate HfAlOX-based MOS-HEMT exhibited a decent performance with IDMAX of 870 mA/mm, GMMAX of 118 mS/mm, threshold voltage (VTH) of −3.55 V, higher ION/IOFF ratio of approximately 1.8 × 109, subthreshold slope (SS) of 90 mV/dec, and a high VBR of 195 V with reduced gate leakage current of 1.3 × 10−10 A/mm.