Metamorphic High Electron Mobility Transistor Research Articles

Effect of Trap Behavior on the Reliability Instability of Metamorphic Buffer in InAlAs/InGaAs MHEMT on GaAs.

Our investigation focused on assessing the influence of the metamorphic buffer in metamorphic high-electron-mobility transistors (MHEMT) that were grown on GaAs substrates. While an MHEMT exhibited elevated off-state current levels, its direct current (DC) and radio frequency (RF) traits were found to be comparable to those of InP-based lattice-matched high-electron-mobility transistors (LM-HEMTs). However, the Pulsed I-V measurement results confirmed the presence of the fast transient charging effect, leading to a more substantial degradation in drain current observed in MHEMT. In addition, through the low-frequency noise characteristics, it was confirmed that the dominant trapping location was located in the bulk site. The slope of the 1/f noise measurement indicated that the primary trapping site was in proximity to the bulk traps. The carrier-number-fluctuation (CNF) model was employed to extract the bulk trap density (Nt). For the LM-HEMTs, the value was at 3.27 × 1016 eV-1·cm-3, while for the MHEMT, it was 3.56 × 1017 eV-1·cm-3.

Optimized recess etching criteria for T‐gate fabrication achieving ft = 290 GHz at Lg = 124 nm in metamorphic high electron mobility transistor with In0.7Ga0.3As channel

AbstractThe authors propose criteria for recess etching to fabricate T‐gate used in InGaAs high electron mobility transistors (HEMTs). By patterning additional rectangular pads on the source and drain metals in the e‐beam lithography step, it is possible to measure the drain‐to‐source resistance (Rds) and current (Ids). The ratio (Γ) of before and after etching for each Rds and Ids can be used as criteria to determine the point in time to stop etching. By performing recess etching with Γ= 1.97 for Rds and Γ= 0.38 for Ids on an epiwafer having cap doping concentration of 2 × 1019 cm−3 and channel indium content of 0.7, the authors have fabricated InGaAs metamorphic high electron mobility transistor (mHEMT) device showing gm,max= 1603 mS/mm and ft= 290 GHz at Lg= 124 nm. The criteria presented can be applied to InGaAs HEMTs with various epitaxial structures.

Design and Investigation of a Metamorphic InAs Channel Inset InP HEMT for Cryogenic Low-Noise Amplifiers

Design and Investigation of a Metamorphic InAs Channel Inset InP HEMT for Cryogenic Low-Noise Amplifiers

Fabrication and Characterization of In0.53Ga0.47As/InAs/In0.53Ga0.47As Composite Channel Metamorphic HEMTs (mHEMTs) on a GaAs Substrate.

In this work, we successfully demonstrated In0.53Ga0.47As/InAs/In0.53Ga0.47As composite channel metamorphic high electron mobility transistors (mHEMTs) on a GaAs substrate. The fabricated mHEMTs with a 100 nm gate length exhibited excellent DC and logic characteristics such as VT = -0.13 V, gm,max = 949 mS/mm, subthreshold swing (SS) = 84 mV/dec, drain-induced barrier lowering (DIBL) = 89 mV/V, and Ion/Ioff ratio = 9.8 × 103 at a drain-source voltage (VDS) = 0.5 V. In addition, the device exhibited excellent high-frequency characteristics, such as fT/fmax = 261/304 GHz for the measured result and well-matched modeled fT/fmax = 258/309 GHz at VDS = 0.5 V, which is less power consumption compared to other material systems. These high-frequency characteristics are a well-balanced demonstration of fT and fmax in the mHEMT structure on a GaAs substrate.

Analysis of issues in gate recess etching in the InAlAs/InGaAs HEMT manufacturing process

AbstractWe have developed an InAlAs/InGaAs metamorphic high electron mobility transistor device fabrication process where the gate length can be tuned within the range of 0.13 μm–0.16 μm to suit the intended application. The core processes are a two‐step electron‐beam lithography process using a three‐layer resist and gate recess etching process using citric acid. An electron‐beam lithography process was developed to fabricate a T‐shaped gate electrode with a fine gate foot and a relatively large gate head. This was realized through the use of three‐layered resist and two‐step electron beam exposure and development. Citric acid‐based gate recess etching is a wet etching, so it is very important to secure etching uniformity and process reproducibility. The device layout was designed by considering the electrochemical reaction involved in recess etching, and a reproducible gate recess etching process was developed by finding optimized etching conditions. Using the developed gate electrode process technology, we were able to successfully manufacture various monolithic microwave integrated circuits, including low noise amplifiers that can be used in the 28 GHz to 94 GHz frequency range.

Self-heating of cryogenic high electron-mobility transistor amplifiers and the limits of microwave noise performance

The fundamental limits of the microwave noise performance of high electron-mobility transistors (HEMTs) are of scientific and practical interest for applications in radio astronomy and quantum computing. Self-heating at cryogenic temperatures has been reported to be a limiting mechanism for the noise, but cryogenic cooling strategies to mitigate it, for instance, using liquid cryogens, have not been evaluated. Here, we report microwave noise measurements of a packaged two-stage amplifier with GaAs metamorphic HEMTs immersed in normal and superfluid 4He baths and in vacuum from 1.6 to 80 K. We find that these liquid cryogens are unable to mitigate the thermal noise associated with self-heating. Considering this finding, we examine the implications for the lower bounds of cryogenic noise performance in HEMTs. Our analysis supports the general design principle for cryogenic HEMTs of maximizing gain at the lowest possible power.

A 50-nm Gate-Length Metamorphic HEMT Technology Optimized for Cryogenic Ultra-Low-Noise Operation

This article reports on the investigation and optimization of cryogenic noise mechanisms in InGaAs metamorphic high-electron-mobility transistors (mHEMTs). HEMT technologies with a gate length of 100, 50, and 35 nm are characterized both under room temperature and cryogenic conditions. Furthermore, two additional technology variations with 50-nm gate length are investigated to decompose different noise mechanisms in HEMTs. Therefore, cryogenic extended Ku-band low-noise amplifiers of the investigated technologies are presented to benchmark their noise performance. Technology C with a 50-nm gate length exhibits an average effective noise temperature of 4.2 K between 8 and 18 GHz with a minimum of 3.3 K when the amplifier is cooled to 10 K. The amplifier provides an average gain of 39.4 dB at optimal noise bias. The improved noise performance has been achieved by optimization of the epitaxial structure of the 50-nm technology, which leads to low gate leakage currents and high gain at low drain current bias. To the best of the authors' knowledge, this is the first time that an average noise temperature of 4.2 K has been demonstrated in the Ku-band.

A mHEMT Power-Reconfigurable Distributed Amplifier Using a Gain Cell Switching Technique

A power-reconfigurable distributed amplifier (DA) is implemented using a 130 nm metamorphic high-electron mobility transistor (mHEMT) process. Using a mHEMT process with excellent high-frequency characteristics, output power and efficiency at high frequencies are improved compared with the existing power-reconfigurable distributed amplifiers. In this article, a gain cell switching technique is proposed as the power reconfiguration method for the distributed amplifier. The gain cell switching technique expands the gain bandwidth and power reconfigurability more than the conventional bias control. The proposed power-reconfigurable DA obtains a measured linear gain of 10.0–13.6 dB from 0.5 to 62.5 GHz and a measured output power of 20.2–21.5 dBm from 10 to 40 GHz. A measured power added efficiency (PAE) is 11.6–20.0% from 10 to 40 GHz. Under a low power mode (LPM), it obtains a measured linear gain of 4.4–7.1 dB from 0.5 to 65 GHz and a measured output power of 14.7–15.9 dBm from 10 to 40 GHz. At 10 GHz, a drain efficiency (DE) is 11.4% at 5.6 dB power back-off. This is 6.5% higher than the conventional DA or more than twice as high.

Planarized Trench Isolation of In0.52Al0.48As/In0.8Ga0.2As Metamorphic High-Electron-Mobility Transistor by Liquid Phase Chemical Enhanced Oxidation

The liquid phase chemical enhanced oxidation (LPCEO) technique was applied to achieve planarized isolation of a high-indium-content In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.48</sub> As/In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> As metamorphic high-electron-mobility transistor (MHEMT). Through a simple, low-temperature process not requiring costly machinery, electrical isolation of components was accomplished. In addition, multiple advantages were gained, including the production of planarized surfaces, low pollution, and reduction in the subsequent disposal of wet etching solution and costs for dry etching or ion implantation. Because of the decrease in lateral defect density caused by wet or dry etching and the further decrease in gate leakage current owing to the isolated oxide film, the performance of devices, with improved DC characteristics, less flicker noise, and enhanced high-frequency performance, can be increased.

W‐Band MMIC chipset in 0.1‐μm mHEMT technology

We developed a 0.1-μm metamorphic high electron mobility transistor and fabricated a W-band monolithic microwave integrated circuit chipset with our in-house technology to verify the performance and usability of the developed technology. The DC characteristics were a drain current density of 747 mA/mm and a maximum transconductance of 1.354 S/mm; the RF characteristics were a cutoff frequency of 210 GHz and a maximum oscillation frequency of 252 GHz. A frequency multiplier was developed to increase the frequency of the input signal. The fabricated multiplier showed high output values (more than 0 dBm) in the 94 GHz–108 GHz band and achieved excellent spurious suppression. A low-noise amplifier (LNA) with a four-stage single-ended architecture using a common-source stage was also developed. This LNA achieved a gain of 20 dB in a band between 83 GHz and 110 GHz and a noise figure lower than 3.8 dB with a frequency of 94 GHz. A W-band image-rejection mixer (IRM) with an external off-chip coupler was also designed. The IRM provided a conversion gain of 13 dB–17 dB for RF frequencies of 80 GHz–110 GHz and image-rejection ratios of 17 dB–19 dB for RF frequencies of 93 GHz–100 GHz.

Special issue on SoC and AI processors

Special issue on SoC and AI processors

Photoluminescence of extended defects in heterostructures with InAlAs metamorphic buffer at different excitation wavelengths

We report the observation of photoluminescence (PL) of energy levels presumably associated with extended defects in metamorphic buffer InxAl1–xAs with x = 0.05 → 0.65 at photon energy range of 0.8–1.2 eV, while the quantum well PL was observed at 0.6–0.8 eV. The metamorphic HEMT heterostructures with In0.65Al0.35As/In0.70Ga0.30As/In0.65Al0.35As quantum well (QW) and with different defectiveness degree were studied. Interband excitation by lasers with a wavelength of 409, 450, 532 nm, and subband excitation by infrared (IR) laser with 1064 nm wavelength (with photons energy less than the bandgap of metamorphic buffer layer) both result in the appearance of “defect” PL. Compared to the visible excitation, the IR illumination with the same power density increases “defect” PL intensity in samples with high twins density by an order of magnitude, whereas in more perfect samples with stacking faults and threading dislocations it causes an increase in “defect-to-QW” PL intensities ratio. The study of PL intensity as a function of the pump power in the range of power density 10–3600 W/cm2 reveals that the non-radiative recombination plays an important role during the recombination of photoexcited charge carriers from “defect” levels because the “defect” PL intensity dependence on the pump power density is mainly sublinear while for the QW PL the power law with exponent 1.2–1.4 is observed.

A 300-GHz Wireless Link Employing a Photonic Transmitter and an Active Electronic Receiver With a Transmission Bandwidth of 54 GHz

In this article, we present a 300-GHz wireless link composed of a photonic uni-traveling-carrier diode transmitter and an active electronic receiver based on millimeter wave integrated circuits fabricated in an InGaAs metamorphic high electron mobility transistor technology. The input pseudorandom binary sequence is transmitted and analyzed offline using fast analog-to-digital converters. The data transmission reaches,100 Gb/s over a distance of 15 m. Complex modulation formats, such as 32-quadrature amplitude modulation and 64-quadrature amplitude modulation, are successfully transmitted up to a symbol rate of 8 GBd. The system presents not only high linearity but is also capable of transmitting high symbol rates, up to 40 GBd. To the best of the authors' knowledge, this represents the highest ever reported transmission bandwidth as well as the highest spectral density symbol rate product for transmissions with center frequency in the terahertz band. Thus, the usage of such links in future bandwidth-hungry applications, such as data centers, data showers, fronthaul, and backhaul, is proven feasible.

60 GHz Low-Noise Amplifier for Detection Systems

This paper presents a 60 GHz low-noise amplifier (LNA) to improve detection systems performance. The considered system is based on impulse radar technology. The LNA is designed in GaAs metamorphic High Electron Mobility Transistor (m-HEMT) technology. Three stages common source transistors are used with inductive degeneration for a good tradeoff between gain and noise. The post-layout simulation results show a noise factor of 2.06 dB and a gain of 14.5 dB at 60.2 GHz, for a power consumption of 13.5 mW. The simulated nonlinear characteristics show an IP 1dB (Input 1 dB compression Point) of -10 dBm and an IIP3 (Input third-order Intercept Point) of -4.4 dBm. The LNA occupies an area of 1.56 × 1.29 mm2.

Low-Loss Millimeter-Wave SPDT Switch MMICs in a Metamorphic HEMT Technology

This letter presents the design and performance of two single-pole double-throw (SPDT) switches operating in $V$ -band (50–75 GHz) and $W$ -band (75–110 GHz). The millimeter-wave (mmW) integrated circuits (MMICs) are fabricated in a 50-nm gate-length metamorphic high-electron-mobility transistor technology. Special attention was paid to the reduction of the insertion loss (IL). Thus, both switch MMICs achieve an IL of 1–1.6 dB (average 1.2 dB), covering the entire $V$ -band and $W$ -band, respectively. The isolation (ISO) of the switches is better than 31.6 and 28.5 dB, respectively. The input power for 1 dB of IL compression is at least 22 and 19 dBm, respectively. A wafer mapping of both circuits exhibits a high yield and low spread of IL and ISO. Based on the given results, the presented SPDT switch MMICs demonstrates state-of-the-art performance.

Frequency Multiplier and Mixer MMICs Based on a Metamorphic HEMT Technology Including Schottky Diodes

This paper reports on the monolithic integration of layout-optimized Schottky diodes realized in an established 50-nm gate-length metamorphic high-electron-mobility transistor technology for use in multifunctional nonlinear circuits. The suitability of the realized Schottky diodes is demonstrated by a broadband millimeter-wave I/Q-mixer (In-phase/Quadrature) and local oscillator (LO) chain comprising two power amplifiers and a frequency tripler, fabricated on monolithic microwave integrated circuits (MMICs). Both circuits are based on an anti-parallel Schottky diode topology. The subharmonically-pumped I/Q-mixer covers an RF (radio frequency) and IF (intermediate frequency) range of at least 75 GHz to 110 GHz and 0.5 GHz to 15 GHz, respectively. The single-sideband conversion loss is between 14 dB and 16 dB across most of the entire RF and IF bands. The core of the LO chain consists of a frequency tripler (multiplier by three) and features a bias-adjustable output power with almost constant conversion efficiency and a control range of more than 8 dB. The fully-integrated LO chain MMIC matches the needs of the presented I/Q-mixer and exhibits an average output power of 16.3 dBm with a covered frequency range of 38 GHz to 60 GHz. The unwanted harmonics are suppressed by at least -25.9 dBc below the third harmonic for the entire frequency range and better than -32.1 dBc for most part of the band. Thus, the mixer and tripler MMICs demonstrate state-of-the-art performance with regards to, e.g., covered bandwidth, output power, harmonic suppression, or 1 dB compression point.

A Terahertz Wireless Communication Link Using a Superheterodyne Approach

This article presents a wireless communication point-to-point link operated in the low terahertz (THz) range, at a center frequency of 300 GHz. The link is composed of all-electronic components based on monolithic millimeter wave integrated circuits fabricated in an InGaAs metamorphic high electron mobility transistor technology. Different configurations and architectures are compared and analyzed. The superheterodyne approach proves to be the most promising of all, being compliant with the new IEEE standard for 100 Gb/s wireless transmissions and showing compatibility to accessible, already available modems. The first option of realizing the superheterodyne configuration is by combining the 300-GHz transmitter and receiver with of-the-shelf up and down converters operating at a center frequency of 10 GHz. In this case, data rates of up to 24 Gb/s are achieved. The second option employs a fast arbitrary waveform generator that uses a carrier frequency to up-convert the baseband data. In this case, data rates of up to 60 Gb/s and transmission distances of up to 10 m are achieved with complex modulated signals like 16-QAM and 32-QAM. The baseband signal is composed of pseudo-random binary sequences and is analyzed offline using fast analog to digital converters. In superheterodyne configuration, multichannel transmission is demonstrated. Channel data rates of 10.2 Gb/s using 64-QAM are achieved. The successful transmission of aggregated channels in this configuration shows the potential of THz communication for future high data rate applications.

Broadband 240-GHz Radar for Non-Destructive Testing of Composite Materials

A broadband frequency-modulated continuous-wave radar that operates at a center frequency of 240 GHz is being presented. The main focus of this paper is on the monolithic integration of the millimeter wave transceiver front end circuit and its validation at the wafer level, module level, and system level. The transceiver front end chip was developed using a 35-nm InAlAs/InGaAs-based metamorphic high electron mobility transistor technology with an advanced back-end-of-line (BEOL) process. The key functional building blocks were developed as part of a broadband integrated circuit library for millimeter wave, and THz phased array applications. The transmit path (TX) of the transceiver has a 3-dB defined bandwidth of 60 GHz, and output power of 8 dBm was measured at the chip level and 6 dBm at the waveguide module level, respectively. The receive path (RX) exhibited a conversion gain of 10 dB and an average noise figure (NF) of 7 dB, which were measured over a 3-dB defined bandwidth of 40 GHz, or a 10-dB defined bandwidth of 60 GHz. The flatness of the TX and RX was 1 dB for the transmit power and NF between 220 and 260 GHz. The radar was evaluated for its application in nondestructive tomographic imaging of multilayer glass fiber-reinforced materials. A focusing scanning system was used to determine the characteristic features of material samples at different bandwidths up to 65 GHz.

InAlAs/InGaAs/GaAs metamorphic high-electron mobility transistors with selective and nonselective recess gate processes

InAlAs/InGaAs metamorphic high-electron-mobility transistors (MHEMTs) on GaAs substrates are fabricated. Two kinds of gate-recess schemes—nonselective and selective etching—are investigated. The selective-etch recessed-gate process appears to be well-suited to fabricating high-performance MHEMTs. The temperature-dependent dc characteristics of MHEMTs are also investigated. The maximum extrinsic transconductance (gm,max) of the MHEMT with nonselective recess gate is 303 mS/mm, while the gm,max of the MHEMT with nonselective recess gate is 347 mS/mm. The application of the developed selective-etch recessed-gate process to MHEMTs produces the reduced leakage currents, increased reverse breakdown voltage, reduced high-frequency noise, and increased high-frequency and increased power characteristics.

GaAs metamorphic high electron mobility transistors for future deep space-biomedical-millitary and communication system applications: A review

Following the introduction of metamorphic high electron mobility transistors (MHEMTs) 30 years back, there has been a rapid growth in their use in advanced MMIC (monolithic microwave integrated circuit) and TMIC (Terahertz monolithic integrated circuit) applications in sub-millimetre wave (S-MMW) and terahertz (THz) frequency regime. Undoubtedly, they are capable of making a great impact in applications such as deep space, cryogenic, biomedical instrumentation, military, high speed communication networks etc, in the years to come. This review article not only studies the progress of depletion mode (D-Mode), enhancement mode (E-Mode) type MHEMTs in the last 30 years, extensively but also critically and systematically analyzes the fabrication challenges, reliability issues and their use in cryogenic fields. Yet another highlight is that the work also carefully examines the utility of MHEMTs in deep space, biomedical, scientific, military, communication areas and so forth.