MOS-HEMT Device Research Articles

Investigation of the Electrical Characteristics of AlGaN/AlN/GaN Heterostructure MOS-HEMTs with TiO2 High-k Gate Insulator

This paper investigates the impact of TiO2 high-k gate insulator on the electrical characteristics of AlGaN/AlN/GaN MOS-HEMT transistors using MATLAB and Atlas-TCAD simulation software. The physical analytical model of the MOS-HEMTs is used for simulation from Al2O3, HfO2, and TiO2 as the gate dielectric materials, which provide higher performance and reliability of the MOS-HEMT devices. The device shows a good improvement in its result of the DC and AC characteristics with different permittivity of insulator materials. Thus, the DC and AC performance of GaN MOS-HEMTs is higher than with other insulators, such as Al2O3 and HfO2 by using TiO2 as the gate dielectric. Moreover, the simulation results proved that TiO2 is the better gate dielectric material to enhance the electrical reliability of the power switching devices for high-temperature applications such as electric automobiles.

The study of N-polar GaN/InAlN MOS-HEMT and T-gate HEMT biosensors

The sensing performance of N-polar GaN/InAlN MOS-HEMT biosensors for neutral biomolecules was investigated and compared with the Ga-polar MOS-HEMT and N-polar T-gate HEMT by numerical simulation. The results indicate that the N-polar GaN/InAlN MOS-HEMT biosensor has higher sensing sensitivity than the Ga-polar MOS-HEMT and N-polar T-gate HEMT biosensors. Furtherly, to improve the sensing performance of N-polar MOS-HEMT, the influence of cavity dimensions, GaN channel layer thickness, and InAlN back barrier layer thickness on device performance was investigated. It is demonstrated that the sensitivity of the biosensor increases as the cavity height decreases and the cavity length increases. Therefore, the sensing performance of the N-polar MOS-HEMT device will be enhanced by thinning the GaN channel layer thickness or increasing the InAlN back barrier thickness, which can be mainly attributed to the variation of the energy band structure and two-dimensional electron gas concentration in the HEMT heterostructure. Finally, the highest sensitivity can be obtained for the N-polar MOS-HEMT with 6 nm-thick GaN channel layer, 30 nm-thick InAlN back barrier layer, and two 0.9 μm-long and 5 nm-high cavities. This work provides structural optimal design guidance for the N-polar HEMT biosensor.

Influence of the Passivation Layers on the Self-Heating Effect in the Double Channel AlGaN/GaN MOS-HEMT Device

Influence of the Passivation Layers on the Self-Heating Effect in the Double Channel AlGaN/GaN MOS-HEMT Device

Analog/RF and Power Performance Analysis of an Underlap DG AlGaN/GaN Based High-K Dielectric MOS-HEMT

This paper exemplifies an exhaustive, figurative and subjective study on the RF performance and DC characteristics analysis of an Underlapped Double-Gate (U-DG) AlGaN/GaN heterojunction-based MOS-HEMT device with Hafnium-based high-k dielectric gate material. This paper depicts the effect of gate length variations on the drain current (ID), the transconductance (gm), the transconductance generation factor (gm/ID) and the RF FOMs intrinsic capacitances (CGD, CGS and CGG), intrinsic resistances (RGD and RGS), cut-off frequency (fT) and maximum oscillation frequency (fMAX). This study reveals shortening of channel length leading to better gate controllability hence an overall superior analog and RF performance is achieved. The U-DG AlGaN/GaN based MOS-HEMT device of 100 nm channel length shows a better Power Output Efficiency (POE) of 33% in contrast to 31% and 23% for the 200 nm and 300 nm devices respectively.

A Physics-Based Compact Static and Dynamic Characteristics Model for Al2O3/InxAl1−xN/AlN/GaN MOS-HEMTs

This paper presents a physics-based compact of indium mole fraction dependent analytical model for static and dynamic characteristics of GaN-based MOS-HEMTs. The model covers all the different operating regimes of the MOS-HEMT devices. The model is evaluated step by step with excellent agreement compared with the simulated data obtained by Atlas-TCAD simulation and the experimental data have demonstrated the validity of the proposed model for different indium mole fractions (12, 15, 17, and 18)%. From static and dynamic characteristics, it is also observed that by careful setting of the indium mole fraction for GaN-based MOS-HEMTs can improve the performance of the device, and; hence, it is proper for high performance low loss applications. MOS-HEMTs produce high drain current of 1227 A/m at a positive gate bias $$V_{\rm{gs}}$$ of 3 V and with 15% of indium mole fraction, high transconductance of 268 S/m, and high cut-off frequency of 35 GHz at x = 18% indium mole fraction.

Drain Charactersitic Analysis of High Electron Mobility Transistor (Moshemt)

A High-electron-mobility transistor, otherwise called a field-effect transistor consolidating an intersection between two materials with various band holes as the channel rather than a doped region. While lately, gallium nitride HEMTs have pulled in consideration because of their powerful execution. In this paper a MOSHEMT device is designed and afterward break down the device DC characteristic. MOSHEMT is a modified structure of HEMT. In MOSHEMT an oxide layer (Hf02) is embedded to the device. Characteristic dissect of device include the breaking down of channel current, gate leakage current and furthermore the Ioff/Ion proportion of the device. HEMT transistors can work at higher frequencies.

Modeling and Simulation of AlGaN/GaN MOS-HEMT for Biosensor Applications

HEMT technology is being used for development of biosensors. Many floating gate HEMT-based biosensors have been experimentally developed but little work has been reported on modeling of MOSHEMT-based biosensors. Therefore in this paper an analytical model of AlGaN/GaN MOSHEMT-based biosensor has been developed for the first time to detect the biomolecule species, such as protein, streptavidin, ChOx, and uricase by using a dielectric modulation approach. In this paper, the cavity length and the dielectric constant of the MOSHEMT device are optimized to improve the sensitivity of the device. The proposed structure of the MOSHEMT has been simulated on an ATLAS TCAD device simulator and the simulated results show a significant change in drain current, shift in threshold voltage, change in channel potential below the cavity region, and the capacitance on introducing biomolecules in the nanogap cavity. The results of analytical model have been verified and they show good agreement with simulated results. The sensitivity of the device can be enhanced by optimizing the device parameters, such as nanogap cavity length and width, and also by varying the gate length of the device.

Effect of Barrier Layer Thickness on AlGaN/GaN Double Gate MOS-HEMT Device Performance for High-Frequency Application

Effect of Barrier Layer Thickness on AlGaN/GaN Double Gate MOS-HEMT Device Performance for High-Frequency Application

AlGaN/GaN MOS-HEMT Device Fabricated Using a High Quality PECVD Passivation Process

In this letter, an AlGaN/GaN MOS-HEMT was demonstrated using a 5-nm-thick SiOx dielectric layer deposited by plasma enhanced chemical vapor deposition (PECVD) as a gate insulator. The fabricated device exhibits a maximum ${I}_{{\text {DS}}}$ current of 570 mA/mm at ${V}_{{\text {GS}}} =+ {3}$ V, an ON-state resistance ( ${R}_{\mathrm {biosc{on}}}$ ) of $7.3~\Omega \cdot $ mm, a maximum transconductance peak of 180 mS/mm, and a gate leakage current below 1 nA/mm at a gate voltage of +/−3 V. Moreover, a very low pinchoff voltage ( ${V}_{p})$ shift was observed during the ${I}_{{\text {DS}}}$ – ${V}_{\text {GS}}$ hysteresis measurements giving an estimated interface state density ( ${D}_{\text {it}})$ as low as $3.9\times 10^{ {11}}$ cm $^{-2}$ eV $^{-1}$ . These results demonstrate the high quality of the SiO x /AlGaN interface and the efficiency of the passivation process. To the best of our knowledge, this is the lowest reported ${D}_{\text {it}}$ on an AlGaN/GaN MOS-HEMT device using a PECVD deposition technique.

Normally-Off AlGaN/GaN Mos-Hemts Using ZrO2 Gate Dielectric with Tuneable Charge

GaN-based high electron mobility transistors (HEMTs) are of significant interest for next-generation RF power amplifiers and monolithic microwave integrated circuits (MMICs). The integration of a gate dielectric in a MOS-HEMT device has been shown to offer significantly reduced gate leakage, resulting in improved reliability and reduced off-state power consumption. ZrO2 has attracted increasing attention as a candidate gate insulator for GaN-based HEMTs, due to a high dielectric constant (25), large bandgap (5.9 eV), and high breakdown voltage (15-20 MV/cm). We have previously reported high positive threshold voltage in unpassivated HEMT structures with recessed barrier layers and ZrO2 gate dielectrics deposited using zirconium (IV) tert-butoxide (ZTB) as the Zr precursor [1]. In this work, we compare these devices to structures incorporating the more common tetrakis(dimethylamino)zirconium (TDMA-Zr) precursor, which is expected to exhibit less fixed oxide charge. Combined with the optional barrier recess step, we demonstrate threshold voltage control over a range of 7V for a given HEMT layer structure. We also report the integration of SiNX passivation layers and an evaluation of the dynamic switching performance of the devices. AlGaN/GaN HEMT devices structures were grown on Si substrates by MOCVD, and devices were fabricated following standard GaN device process steps described elsewhere [1]. ZrO2 layers were deposited by atomic layer deposition using both ZTB and TDMA-Zr precursors and deionized water. Ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to verify thickness and identify film stoichiometry. Capacitance-voltage measurements were initially used to characterize the oxide. A dielectric constant of 25 was extracted, and interface trap density was on the order of ~1x1012, dependent upon the nature of the oxide and the surface upon which it was deposited (HEMT structure vs GaN MOS capacitor). Gated Hall measurements were used to characterize the 2DEG mobility and sheet carrier density, both in the HEMT structure and in the recessed region under the gate. The non-recessed devices exhibit comparable current density, transconductance, and ON-resistance. The threshold voltage is shifted positive for device structures incorporating the ZTB-derived ZrO2 film, approaching enhancement mode even without the barrier recess and demonstrating an exceptionally high +4V with a barrier recess. The mechanism for this is proposed to be the presence of negative charge in the oxide film, potentially due to excess oxygen in the film. The presence of such charge was verified on GaN capacitor structures. In contrast, the TDMA-Zr-derived ZrO2 films exhibit a negative VT shift due to the thicker effective barrier, just reaching enhancement mode operation even with a full barrier recess. The breakdown voltage was comparable among all device structures both with and without recess. As expected, the gate leakage was suppressed over 5 orders of magnitude compared to the reference Schottky gated HEMT. Pulsed I-V measurements indicate a degraded current collapse behavior in the ZTB-based devices, which is expected as the negative charge from the oxide would be expected to enhance the charge trapping effect. In contrast, the TDMA-Zr-based device structures exhibit comparable current collapse to the reference device, and possibly even represent an improvement due to reduced trapping under the gate in the MOS structure. Similar behavior in the recessed gate structure indicates minimal permanent damage from the plasma recess etch. In conclusion, we have demonstrated enhancement mode AlGaN/GaN MOS-HEMTs with a thin ALD-ZrO2 gate oxide and barrier recess. The integration of this particular high-k dielectric in the device structure results in a positive threshold voltage shift due to negative charge in the oxide film and at the interface, which when integrated with a barrier recess enables a VT ~+4V while suppressing gate leakage by 4 orders of magnitude compared to a reference Schottky-gated HEMT. 1. T.J. Anderson, et. al. Appl. Phys. Express 9, 071003 (2016)

Model Development for Current–Voltage and Transconductance Characteristics of Normally-off AlN/GaN MOSHEMT

In this paper, an AlN/GaN-based MOSHEMT is proposed, in accordance to this, a charge control model has been developed analytically and simulated with MATLAB to predict the characteristics of threshold voltage, drain currents and transconductance. The physics based models for 2DEG density, threshold voltage and quantum capacitance in the channel has been put forward. By using these developed models, the drain current for both linear and saturation models is derived. The predicted threshold voltage with the variation of barrier thickness has been plotted. A positive threshold voltage can be obtained by decreasing the barrier thickness which builds up the foundation for enhancement mode MOSHEMT devices. The predicted Id–Vgs, Id–Vds and transconductance characteristics show an excellent agreement with the experimental results and hence validate the model.

Characterization of top barrier thickness from gate capacitance of high mobility III-V semiconductor MOS-HEMT devices

We investigate the effect of varying the top barrier thickness on the gate C–V characteristics of InGaAs and InSb MOS-HEMT devices. The gate capacitance of these devices exhibits a sharp increase at certain gate voltages under both accumulation and inversion bias. The gate voltages at which some of these sharp changes occur depend on the thickness of the top barrier layer. The sharp rise in gate capacitance appears as a peak in the derivative of the capacitance with respect to the gate voltage. The positions of certain peaks of the derivative as a function of the gate voltage give information on the thickness of the top barrier layer. By exploiting this trend it is possible to extract the barrier thickness from the gate C–V characteristics.

Physical and electrical characteristics of AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors with rare earth Er2O3 as a gate dielectric

In this study, the rare earth erbium oxide (Er2O3) was deposited using an electron beam onto an AlGaN/GaN heterostructure to fabricate metal-oxide-semiconductor high-electron-mobility transistors (MOS–HEMTs) that exhibited device performance superior to that of a conventional HEMT. Under similar bias conditions, the gate leakage currents of these MOS–HEMT devices were four orders of magnitude lower than those of conventional Schottky gate HEMTs. The measured sub-threshold swing (SS) and the effective trap state density (Nt) of the MOS–HEMT were 125mV/decade and 4.3×1012cm−2, respectively. The dielectric constant of the Er2O3 layer in this study was 14, as determined through capacitance–voltage measurements. In addition, the gate–source reverse breakdown voltage increased from –166V for the conventional HEMT to –196V for the Er2O3 MOS–HEMT.

Influence of processing and annealing steps on electrical properties of InAlN/GaN high electron mobility transistor with Al 2O 3 gate insulation and passivation

We report on preparation and electrical characterization of InAlN/AlN/GaN metal–oxide–semiconductor high electron mobility transistors (MOS HEMTs) with Al 2O 3 gate insulation and surface passivation. About 12 nm thin high- κ dielectric film was deposited by MOCVD. Before and after the dielectric deposition, the samples were treated by different processing steps. We monitored and analyzed the steps by sequential device testing. It was found that both intentional (ex situ) and unintentional (in situ before Al 2O 3 growth) InAlN surface oxidation increases the channel sheet resistance and causes a current collapse. Post deposition annealing decreases the sheet resistance of the MOS HEMT devices and effectively suppresses the current collapse. Transistors dimensions were source-to-drain distance 8 μm and gate width 2 μm. A maximum transconductance of 110 mS/mm, a drain current of ∼0.6 A/mm ( V GS = 1 V) and a gate leakage current reduction from 4 to 6 orders of magnitude compared to Schottky barrier (SB) HEMTs was achieved for MOS HEMT with 1 h annealing at 700 °C in forming gas ambient. Moreover, InAlN/GaN MOS HEMTs with deposited Al 2O 3 dielectric film were found highly thermally stable by resisting 5 h 700 °C annealing.

Study of AlGaN/GaN MOSHEMT device with Al2O3 insulating film

On the basis of AlGaN/GaN HEMT，the AlGaN/GaN MOSHEMT device was fabricated with Al2O3 insulating film for the first time, which was deposited by ALD.The X-ray photoelectron spectroscopy measurements showed successful deposition of Al2O3 layer on the AlGaN/GaN film. The results of Schottky capacitance，I-V characteristics and DC transfer characteristics measurement showed that the interface state density between the AlGaN film and the Al2O3 insulating film was fairly low and the MOSHEMT device showed successful gate control of drain current up to VGS=+3V and achieved drain saturation current of 800mA/mm，which was much larger than that of the HEMT device. Furthermore，the gate leakage current of MOSHEMT is two orders lower in the reverse bias condition as compared with the Schottky gate structure，which increased the device breakdown voltage，while the leakage current was governed by the Fowler-Nordheim tunneling mechanism.

Studies on electron beam evaporated ZrO2/AlGaN/GaN metal–oxide–semiconductor high‐electron‐mobility transistors

AbstractMetal–oxide–semiconductor high‐electron‐mobility transistors were demonstrated on AlGaN/GaN with electron beam (EB) evaporated ZrO2. The composition of the EB deposited ZrO2 thin films was confirmed using X‐ray photoelectron spectroscopy (XPS). The fabricated ZrO2‐based MOSHEMTs exhibited high positive gate voltage of operation up to +7 V with low gate leakage current. For a comparison, conventional high‐electron‐mobility transistors (HEMTs) were also fabricated with identical device dimensions. The maximum drain current densities of 1168 and 538 mA/mm were observed on MOSHEMTs and HEMTs, respectively. Low gate leakage current density of four orders of magnitude was observed on ZrO2‐based MOSHEMTs when compared with the conventional HEMTs. The observation of high forward on‐voltage with low gate leakage current density and high positive operational voltage reveals the importance of ZrO2 dielectric films for MOSHEMT devices. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)