Quaternary InAlGaN Research Articles

High Current Density and Low Ron Quaternary InAlGaN MIS-HEMT on Si for Power Applications

In this work, a quaternary In0.04Al0.63Ga0.33N/GaN metal-insulator-semiconductor (MIS)-high electron mobility transistor (HEMT) on Si substrate using a GaN:C back-barrier (BB) layer and an AlGaN/AlN superlattice (SL) buffer layer to achieve a high breakdown voltage and a high output current density was demonstrated. Compared to the conventional device adopting AlGaN as the barrier layer, the proposed device showed a better 2DEG carrier density up to 1.9 × 1013 cm−3, a higher output current density up to 1,070 mA mm−1 (improved by 47%), an on-resistance (Ron) as low as 7.64 Ω mm (decreased by 26%), an off-state breakdown voltage up to 2,070 V, and an improved dynamic Ron performance (dynamic to static ratio increased to just 1.2 times at an applied drain-to-source stress voltage (VDS,stress) of 400 V). These results indicated the great potential of the InAlGaN/GaN MIS-HEMTs on Si for high-power switching applications.

Highly Si‐Doped GaN Regrown by Metal–Organic Vapor‐Phase Epitaxy for Ohmic Contact Applied to Quaternary Barrier‐Based High‐Electron‐Mobility Transistors

The quaternary barrier InAlGaN is suitable for GaN high‐electron‐mobility transistors (HEMT) power microwave applications. High doping of the semiconductor under the drain and source is a known suitable solution to achieve low ohmic contact resistance. However, InAlGaN quaternary alloys require a low thermal budget to avoid indium desorption from the active layer during regrowth and thus deteriorating the barrier. Herein, a selective‐area growth technique at 850 °C by metal–organic vapor‐phase epitaxy (MOVPE) to achieve low contact resistance with respect to temperature constraint is presented. Regrowth temperature and mask geometry are investigated to achieve selectivity and control of the regrowth rate. The use of H2 as carrier gas decomposes the GaN buffer layer and damages the surface, creating material cluster during regrowth. Growth with N2 carrier gas shows nonselective epitaxy, as there are deposits on the entire surface of the dielectric mask. Switching from one carrier gas to another depending on the step in the MOVPE reactor helps to control both the morphology and selectivity. The resulting high doping levels of 8 × 1019 cm−3 lead to a low contact resistance of 0.26 Ω mm.

E-mode All-GaN-Integrated cascode MISHEMT with GaN/InAlGaN/GaN backbarrier for high power switching performance: Simulation study

In this work, simulation-based research work based on a novel All-GaN-Integrated Cascode (AGC) MISHEMT with quaternary layer InyAlxGa1-x-yN as backbarrier has been investigated. The AGC-MISHEMT device consists of series combination of enhancement mode (recessed gate MISHEMT) and depletion-mode (MIS-gate) GaN devices with GaN/InAlGaN/GaN sandwich back barrier (SW-BB). TCAD simulations indicate that AGC-MISHEMTs with sandwich back barrier (SW-BB) exhibits simultaneous improvement in terms of drain current density (267 ​mA/mm), high ION/IOFF ratio (108), transconductance-peak (191 ​mS/mm) and breakdown voltage (371 ​V) as compared to AGC-MISHEMT with GaN buffer. The impact of varying mole fractions (x, y), thickness and position of InyAlxGa1-x-yN layer on breakdown voltage has also been examined. Improvement in drain current density up to 40% has been accomplished with increased gate oxide thickness under gate 2 (depletion-mode device) for AGC-MISHEMT with SW-BB. Besides, power switching performance has been compared for AGC-MISHEMT with SW-BB to that of AGC-MISHEMT with GaN buffer and Recessed Single Gate (RSG) MISHEMT for inductive load circuit. Significant reduction in power switching losses (i.e. 43% during turn-ON time and 87% during turn-OFF time) has been observed for AGC-MISHEMT with SW-BB as compared to RSG-MISHEMT. In addition, introduction of quaternary InAlGaN layer in backbarrier for AGC-MISHEMT also results in considerable degradation (∼89%) in power loss when input gate is in OFF-state due to improved ION/IOFF ratio in contrast with recessed single gate device.

Enhancement in Analog/RF and Power Performance of Underlapped Dual-Gate GaN-Based MOSHEMTs with Quaternary InAlGaN Barrier of Varying Widths

Enhancement in Analog/RF and Power Performance of Underlapped Dual-Gate GaN-Based MOSHEMTs with Quaternary InAlGaN Barrier of Varying Widths

Breakdown Voltage Analysis in Quaternary InAlGaN High Electron Mobility Transistor of High-K Passivation Layer for High Power Applications

The 2-Dimensional breakdown characteristics analysis in InAlGaN/GaN high electron mobility transistors (HEMTs) is implemented through including of donor and acceptor atoms inside the barrier layer. Thereby dependences of the relative permittivity εr and the thickness d of passivation layer on the breakdown voltage are related for the parametric analysis. When the relative permittivity εr increases duly affects the breakdown voltage by order of increases, owing to its electric field existence at the drain, there on resulting in εr upsurges. This occurs due to the properties of insulator with the applied voltage evenly drops uniformly. The inducing voltage drop alongside the heterostructure of materials InAlGaN/GaN develops flatter response on the drain terminal of the gate owing to its permittivity εr of higher order. The aforementioned breakdown voltage surges, since of the electric field nearby the drain has weakened as a owing to it thickness of passivating layer d, this resolute InAlGaN/GaN HEMTs of a high-k along with the thicker passivation layer has higher breakdown voltage.

An Over 20-W/mm S-Band InAlGaN/GaN HEMT With SiC/Diamond-Bonded Heat Spreader

This letter reports on an InAlGaN/GaN high-electron-mobility transistor (HEMT) employing a SiC/diamond-bonded heat spreader with a record high output power density of 22.3 W/mm. A quaternary In-added InAlGaN barrier enabled both the large current of over 1 A/mm and the high breakdown voltage of 257 V. The drain bias was increased as high as 100 V for the S-band load-pull measurement, leading to high power operation. Furthermore, the thermal resistance was reduced by 60%, from 18.8 to 7.2°C/W, by employing the SiC/diamond heat spreader. This large heat dissipation effect was clearly observed in the output power density for the load-pull measurement. Our results demonstrate that the GaN HEMT with an In-added barrier layer is promising not only for millimeter-wave applications but also for high output power microwave amplifiers.

Growth of quaternary InAlGaN barrier with ultrathin thickness for HEMT application

Quaternary InAlGaN barriers with thickness of 7 nm for HEMT application were grown on 3-inch semi-insulating 4H-SiC substrates by metal organic chemical vapor deposition (MOCVD). Focused on growth mechanism of the InAlGaN barrier, the surface morphology and characteristics of InAlGaN/AlN/GaN heterostructures were studied with different growth parameters, including the temperature, Al/Ga ratio and chamber pressure. Among the as-grown samples, high electron mobility is consistent with smooth surface morphology, while high crystalline quality of the quaternary barrier is confirmed by measurements of Photoluminescence (PL) and Mercury-probe Capacity-Voltage (C-V). The recommended heterostructures without SiN passivation is characterized by mobility of 1720 cm2/(V·s), 2DEG density of 1.71*1013 cm−2, sheet resistance of about 210 Ω/□ with a smooth surface morphology and moderate tensile state, specially applied for microwave devices.

Improvement of Power Performance of GaN HEMT by Using Quaternary InAlGaN Barrier

High power performance InAlGaN/GaN high electron mobility transistor (HEMT) as a candidate for high power and high frequency amplifiers has been demonstrated versus the conventional AlGaN/GaN HEMT by using the same device processes. Comparing with its conventional AlGaN/GaN counterpart, the InAlGaN/GaN device exhibits a much larger output current density of 1.94 A/mm due to its higher 2-D electron gas density of $2.0\times 10^{13}$ cm $^{-2}$ by using a thin quaternary InAlGaN barrier layer, and almost twice as large as ${f} _{\mathrm{ T}}$ of 142 GHz and ${f} _{\mathrm{ max}}$ of 203 GHz. Through measurements of large-signal characteristics at frequency of 34 GHz and biased at 10 V, the InAlGaN/GaN device shows a high output power density of 2.75 W/mm, which is about 87% increase in comparison with that of its AlGaN/GaN counterpart with an output power density of 1.47 W/mm.

Quaternary InAlGaN barrier high-electron-mobility transistors with fmax > 400 GHz

We report a high-frequency GaN high-electron-mobility transistor based on the InAlGaN/AlN/GaN heterostructure. A device with an 8-nm-ultrathin barrier layer and a 50-nm-long gate exhibits a maximum current density of 2.22 A/mm, a peak extrinsic transconductance of 0.97 S/mm, and a low on-resistance Ron of 0.94 Ω·mm. Furthermore, an excellent small-signal RF performance is acquired. The device after de-embedding reveals a high current-gain cutoff frequency (fT) of 182 GHz and a high power-gain cutoff frequency (fmax) of 402 GHz simultaneously. To the best of our knowledge, the fmax reported in this work is the highest achieved to date in GaN-based HEMTs fabricated by a conventional process. These outstanding performances clearly demonstrate the great potential of an ultrathin quaternary barrier for millimeter-wave power applications.

The structure of InAlGaN layers grown by metal organic vapour phase epitaxy: effects of threading dislocations and inversion domains from the GaN template.

Defects in quaternary InAlGaN barriers and their effects on crystalline quality and surface morphology have been studied. In addition to growth conditions, the quality of the GaN template may play an important role in the formation of defects in the barrier. Therefore, this work is focused on effects caused by threading dislocations (TDs) and inversion domains (IDs) originating from the underlying GaN. The effects are observed on the crystalline quality of the barrier and characteristic surface morphologies. Each type of TDs is shown to affect the surface morphology in a different way. Depending on the size of the corresponding hillock for a given pinhole, it was possible to determine the dislocation type. It is pointed out that the smallest pinholes are not connected to TDs whereas the large ones terminate either mixed type or edge type TDs. At sufficiently large layer thickness, the IDs originating from the GaN template lead to the formation of concentric trenches at the layer surface, and this is related to the change in growth kinetics on top and at the immediate surroundings of the ID.

High-performance enhancement-mode Al2O3/InAlGaN/GaN MOS high-electron mobility transistors with a self-aligned gate recessing technology

The paper reports high-performance enhancement-mode MOS high-electron mobility transistors (MOS-HEMTs) based on a quaternary InAlGaN barrier. Self-aligned gate technology is used for gate recessing, dielectric deposition, and gate electrode formation. An improved digital recessing process is developed, and an Al2O3 gate dielectric grown with O2 plasma is used. Compared to results with AlGaN barrier, the fabricated E-mode MOS-HEMT with InAlGaN barrier delivers a record output current density of 1.7 A/mm with a threshold voltage (VTH) of 1.5 V, and a small on-resistance (Ron) of 2.0 Ω·mm. Excellent VTH hysteresis and greatly improved gate leakage characteristics are also demonstrated.

Growth of InAlGaN Quaternary Alloys by Pulsed Metalorganic Chemical Vapor Deposition**Supported by the National Science and Technology Major Project of China under Grant No 2013ZX02308-002, and the National Natural Science Foundation of China under Grant Nos 11435010, 61474086 and 61334002.

Epitaxial growth of InAlGaN/GaN structures are performed on the c-plane sapphire by pulsed metal organic chemical vapor deposition with different triethylgallium (TEGa) flows in the growth process of InAlGaN quaternary alloys. X-ray photoelectron spectroscopy results show that the Al/In ratio of the samples increases as the TEGa flows increase in the InAlGaN quaternary growth process. High-resolution x-ray diffraction results show that the crystal quality is improved with increasing TEGa flows. Morphology of the InAlGaN/GaN heterostructures is characterized by an atomic force microscopy, and the growth mode of the InAlGaN quaternary shows a 2D island growth mode. The minimum surface roughness is 0.20 nm with the TEGa flows equaling to 3.6 μmol/min in rms. Hall effect measurement results show that the highest electron mobility μ is 1005.49 cm2 /Vs and the maximal two-dimensional electron gas is 1.63 × 1013 cm−2.

GaN HEMTs with quaternary In0.05Al0.75Ga0.2N Schottky barrier layer

A quaternary InAlGaN Schottky barrier layer is used in GaN high electron mobility transistors (HEMTs) in this study. For potential application to high speed electronic devices, GaN HEMTs with a quaternary InAlGaN Schottky barrier layer are fabricated and characterized. The fabricated device shows a maximum drain current density of 1.8 A mm−1, a maximum trans-conductance of 557 mS mm−1, on/off current ratio higher than 105, a subthreshold swing (S.S.) of 140 mV/decade, and a gate-diode leakage current of 1.2 mA mm−1. For the device with a 100-nm-long gate footprint, a current gain cut-off frequency (fT) of 102 GHz and a maximum oscillation frequency (fmax) of 130 GHz are extracted at the same bias condition (VDS = 8 V and VGS = −2.2 V) whose Lg · fT product is evaluated to be 10.2 GHz · µm.

Novel high-current density GaN-based normally off transistor with tensile-strained quaternary InAlGaN barrier

A GaN-based normally off heterostructure field effect transistor (HFET) with high current density and with a quaternary InAlGaN barrier instead of an AlGaN barrier is investigated. It is difficult to obtain both high-current operation and normally off operation in the GaN-based HFET because of the need to control the polarization-induced charge. In order to obtain a normally off operation using quaternary InAlGaN barrier, the InAlGaN barrier is selectively removed and the p-AlGaN layer is formed as the gate electrode. The obtained threshold voltage of the InAlGaN-based HFET is +1.1 V. The maximum drain current reaches as high as 0.73 A/mm, which is almost twice that of a conventional AlGaN-based normally off gate injection transistor (GIT).

Experimental and simulation study on ultraviolet light emission from quaternary InAlGaN quantum wells with localized carriers

Different-indium-content quaternary InAlGaN multi-quantum-well (MQW) structures with emission wavelength around 290–310 nm were grown by metalorganic chemical vapor deposition, and their emission characteristics including the indium-segregation effect were investigated by using not only experimental evaluation but also applying simulation technique, on the basis of the weakly localized exciton model. The value of an effective localized level in the quaternary InAlGaN MQWs was estimated to be around 70 meV from the relationship between photoluminescence lifetimes and photon energies. The simulation study, which was conducted by fitting the emission spectra, also derived the value of around 50 meV. The present study also indicated that the quaternary InAlGaN MQW structures with the indium segregation have clear advantages over ternary AlGaN MQW ones especially in the range of dislocation density larger than approximately 1 × 108 cm−2.

Ultra‐thin barrier quaternary InAlGaN HEMTs with state of the art sheet resistance

AbstractWe report transport properties measured from quaternary barrier InAlGaN high electron mobility transistor wafers on SiC substrates. With similar barrier thicknesses, higher mobility and sheet charge density were both demonstrated by a strained barrier quaternary In0.07Al0.75Ga0.18N HEMT comparing to a ternary In0.17Al0.83N HEMT with lattice matched barrier to the GaN buffer. With 1 nm AlN interlayer, sheet resistances of 218 Ω/□ and 228 Ω/□ were obtained from 4.8 nm and 4.4 nm barrier structures, respectively. Both structures also show excellent electron motilities. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

GaN‐based high‐frequency devices and circuits: A Fraunhofer perspective

AbstractWe present the current status of our technology for GaN‐based HEMTs and MMICs as well as results ranging from the L‐band up to the W‐band. Epitaxial growth is carried out on 4H‐SiC(0001) substrates by both MOCVD and MBE. Processing is done using standard III–V equipment including both frontside and backside processing. For L‐band power bars we arrive at output powers, efficiencies and gains beyond 100 W, 60% and 17 dB, all measured under cw conditions at 50 V drain bias. The X‐band MMICs are characterized by a high efficiency above 40% for two‐stage amplifiers. Towards mm‐wave applications we have fabricated HEMTs with transit frequencies above 100 GHz and W‐band MMICs delivering 0.5 W/mm at 94 GHz with 7% PAE. First quaternary InAlGaN barriers show promising results for this new materials system. Reliability tests return a very good long‐term stability of our devices even at an elevated channel temperature of 200 °C with an extrapolated lifetime of 5 × 105. Initial space capability tests including total ion dose radiation insensitivity, radiation displacement damage, hydrogen poisoning and single event effect are successfully passed.

Improved Structural and Chemical Properties of Nearly Lattice-Matched Ternary and Quaternary Barriers for GaN-Based HEMTs

A complete structural and compositional study was carried out for a series of GaN-based lattice-matched HEMT structures. As barrier materials pseudomorphic to GaN, both ternary InAlN and quaternary InAlGaN were investigated. Growths were performed using molecular beam epitaxy on GaN/sapphire or GaN/SiC templates. An abrupt triple-layer AlN/GaN/AlN nanothin spacer at the interface is crucial to improve the structural and electrical properties of the heterostructures. In all cases, this resulted in single-crystalline and single-phase barrier layers.

InGaN-based true green laser diodes on novel semi-polar [formula omitted] GaN substrates

The crystal quality and emission characteristics of InGaN-based laser diodes (LDs) with lattice-matched quaternary InAlGaN cladding layers on novel semi-polar { 2 0 2 ¯ 1 } plane GaN substrates were investigated. Highly homogeneous InGaN quantum wells (QWs) with a suppressed piezoelectric field can be realized on the { 2 0 2 ¯ 1 } plane even in the green spectral region. Optical polarization measurements revealed that [ 1 ¯ 0 1 4 ] oriented stripes are advantageous for LDs on { 2 0 2 ¯ 1 } planes. Gain-guided LDs on the novel { 2 0 2 ¯ 1 } plane exhibited the longest lasing wavelength at 533.6 nm under pulsed operation. Continuous-wave (cw) operation at the lasing wavelength of 523.3 nm at 115 mA was also demonstrated. The I th , J th , V th , and the slope efficiency were 110 mA, 9.2 kA/cm 2, 7.4 V, and 0.04 W/A, respectively. These results indicate that the green LDs on semi-polar { 2 0 2 ¯ 1 } plane GaN substrates are promising candidates for laser display applications.

Compositional variation of nearly lattice-matched InAlGaN alloys for high electron mobility transistors

Quaternary InAlGaN semiconductors with AlN mole fractions between 40% and 81% and respective InN contents of 7% and 19% including InAlN as a ternary border case have been grown by plasma-assisted molecular beam epitaxy. The electron mobility in InAlGaN-based heterostructures increases with Ga concentration in the barrier up to 1460 cm2/V s at a sheet electron density of 1.9×1013 cm−2. An advanced spacer comprising an AlN/GaN/AlN triple-layer sequence is inserted between the GaN-buffer and the InAlGaN-barrier. Transistors with thin quaternary barrier show a large current density of 2.3 A/mm and an excellent transconductance of 675 mS/mm.