Metamorphic High Electron Mobility Transistor Research Articles

Fabrication of 0.3-μm T-gate metamorphic AlInAs/GaInAs HEMTs on silicon substrates using metal organic chemical vapor deposition

We present an InGaAs metamorphic high electron mobility transistor (mHEMT) grown using Metalorganic Chemical Vapor Deposition (MOCVD) on an n-type silicon substrate with the introduction of an effective multi-stage buffering scheme. Fabrication and performance of a high-frequency 0.3-μm gate-length depletion-mode Al0.50In0.50As/Ga0.47In0.53As mHEMT is reported for the first time. Using a combined optical and e-beam photolithography technology, submicron mHEMT devices on Si have been achieved. The non-alloyed ohmic contact resistance R c was as low as 0.065 Ω-mm. A maximum transconductance up to 761 mS/mm was measured. The unity current gain cut-off frequency (f T) and the maximum oscillation frequency (f max) were 72.8 and 74.5 GHz, respectively. This device has the highest f T yet reported for a 0.3-μm gate-length Si-based mHEMT grown using MOCVD. A high voltage gain, g m/g ds, of 40.6 is observed in the device.

Investigation on the thermal behavior of 0.15 μm gate-length In0.4Al0.6As/In0.4Ga0.6As MHEMT

In this study, we have successfully investigated the electrical performances of In0.4Al0.6As/In0.4Ga0.6As metamorphic high-electron-mobility transistor (MHEMT) at temperatures range from 275K to 500K comprehensively. By extracting the device S-parameters, the temperature dependent small signal model has been established. At room temperature, 0.15μm T-gate device with double δ-doping design exhibits fT and fMAX values of 103GHz and 204GHz at Vds=1V, an extrinsic transconductance of 678mS/mm, and a current density of 578mA/mm associated with a high breakdown voltage of −13V. Power measurements were evaluated at 40GHz and the measured output power, linear power gain, and maximum power-added efficiency, were 7.12dBm, 10.15dB, and 23.1%, respectively. The activation energy (Ea) extracted from Arrhenius plots is=0.34eV at 150≦T≦350K. The proposed device is promisingly suitable for millimeter-wave power application.

50-nm Asymmetrically Recessed Metamorphic High-Electron Mobility Transistors With Reduced Source–Drain Spacing: Performance Enhancement and Tradeoffs

Whereas gate-length reduction has served as the major driving force to enhance the performance of GaAs- and InP-based high-electron mobility transistors (HEMTs) over the past three decades, the limitation of this approach begins to emerge. In this paper, we present a systematic evaluation of the impact of greatly reduced source-drain spacing on the performance of 50-nm asymmetrically recessed metamorphic HEMTs (MHEMTs). Extremely high extrinsic transconductance has been achieved over a wide drain bias range starting from as low as 0.1 V by reducing source-drain spacing to 0.5 μm with a self-aligned (SAL) ohmic process. The measured maximum extrinsic transconductance of 3 S/mm is a new record for all HEMT devices on a GaAs substrate and is equal to the best results reported for InP-based HEMTs. With the use of an asymmetric recess, SAL MHEMTs also demonstrate remarkable improvement in other major figures of merit, including off-state breakdown, on-state breakdown, subthreshold characteristics, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ratio, and the voltage gain over the other SAL HEMTs reported so far. However, they still, in a few respects, under perform the conventional devices typically with 2-μm source-drain spacing. In particular, the on-state breakdown of the SAL devices has been capped at approximately 2 V, even with a very wide asymmetric recess. It appears that the uniqueness of the SAL technology would best fit applications that require low voltage and/or low DC power consumption, which can be fully tapped only when the parasitic capacitance is also properly controlled with, e.g., a high stem gate process.

Comprehensive Temperature-Dependent Studies of Metamorphic High Electron Mobility Transistors With Double and Single $\delta$-Doped Structures

The temperature-dependent characteristics of meta morphic high electron mobility transistors (MHEMTs) with double and single δ-doped structure are studied and demonstrated. Due to the use of double δ-doped sheets, the current density in the channel layer and two-dimensional electron gas could effectively be increased. The excellent turn-on voltage of 1.18 (0.80) V, max imum drain saturation current of 544 (524) mA/mm, maximum extrinsic transconductance of 361 (312) mS/mm, unity current gain cutoff frequency of 55.06 GHz, and maximum oscillation frequency of 129.17 GHz are obtained at 300 (510) K for a 0.6 × 100 μm2 gate dimension double δ-doped MHEMT. In addition, using wide-bandgap InAlAs Schottky, spacer, and buffer layers, the carrier confinement could significantly be improved at high temperature. Therefore, excellent thermal stability is achieved for double δ-doped MHEMT. The device with a double δ-doped structure exhibits a considerably low temperature coefficient on threshold voltage (∂Vth/∂T) of 0.06 mV/K when the temperature is increased from 330 to 510 K, which is superior to previous reports of related high electron mobility transistors.

A high isolation W-band MMIC drain type cascode single balanced mixer

We present a high isolation W-band MMIC drain type cascode single balanced mixer of high LO-to-RF isolation and wide band with conversion characteristic using the high directivity monolithic tandem couplers and 0.1 μm GaAs-based metamorphic high electron mobility transistors (MHEMTs). The fabricated mixer consists of two cascode MHEMT mixers and two tandem couplers using the air-bridge crossovers. We establish a drain type cascode mixer structure where the LO signal is applied to the drain port in the mixing component of common source MHEMT circuit. The tandem coupler exhibits good couplings (2.92–3.8 dB), low return losses (−32.7 dB), and isolations (15.4–39.2 dB) in a wide bandwidth of 75–110 GHz. The mixer shows a conversion loss of 9.8 dB at 94 GHz, an output P1dB of −14.8dBm at LO frequency of 94.542 GHz, and LO-to-RF isolations of 29.5–39.5 dB at 94–100 GHz.

Cryogenic Low-Noise mHEMT-Based MMIC Amplifiers for 4–12 GHz Band

Two broadband very low-noise amplifiers operating in the frequency range from 4 to 12 GHz at cryogenic temperature are presented. The amplifier circuits have been developed using a 100 nm gate length InAlAs/InGaAs metamorphic high electron mobility transistor (mHEMT) technology. The three-stage amplifiers are monolithic microwave integrated circuit (MMIC) chips manufactured in coplanar technology. At cryogenic temperature the first MMIC amplifier achieved a linear gain of 22 dB and an average noise temperature of 11.6 K with a power dissipation of 41 mW. The second MMIC amplifier, with external input matching network, exhibited a gain of 26 dB, and an excellent average noise temperature of 8.1 K with a power dissipation of 12 mW. Both LNA units demonstrate broad bandwidth, high gain, low noise temperature, and compact chip size. The results obtained prove that mHEMT technology is suitable for applications in large instantaneous bandwidth cryogenic receivers for radio astronomy applications.

A D-Band Subharmonically-Pumped Resistive Mixer Based on a 100 nm MHEMT Technology

A D-band subharmonically-pumped resistive mixer has been designed, processed, and experimentally tested. The circuit is based on a 180° power divider structure consisting of a Lange coupler followed by a λ/4 transmission line (at local oscillator (LO) frequency). This monolithic microwave integrated circuit (MMIC) has been realized in coplanar waveguide technology by using an InAlAs/InGaAs-based metamorphic high electron mobility transistor process with 100-nm gate length. The MMIC achieves a measured conversion loss between 12.5 dB and 16 dB in the radio frequency bandwidth from 120 GHz to 150 GHz with 4-dBm LO drive and an intermediate frequency of 100 MHz. The input 1-dB compression point and IIP3 were simulated to be 2 dBm and 13 dBm, respectively.

Metamorphic HEMT MMICs and Modules Operating Between 300 and 500 GHz

In this paper, we present the development of submillimeter-wave monolithic integrated circuits (S-MMICs) and modules for use in next-generation sensors and high-data-rate wireless communication systems, operating in the 300-500-GHz frequency regime. A four-stage 460-GHz amplifier MMIC and a 440-GHz class-B frequency doubler circuit have been successfully realized using our 35-nm InAlAs/InGaAs-based metamorphic high-electron mobility transistor (mHEMT) technology in combination with grounded coplanar circuit topology (GCPW). Additionally, a 500-GHz amplifier MMIC was fabricated using a more advanced 20-nm mHEMT technology. To package the submillimeter-wave circuits, a set of waveguide-to-microstrip transitions has been fabricated on both 50-μm-thick quartz and GaAs substrates, covering the frequency range between 220 and 500 GHz. The E-plane probes were integrated in a four-stage 20-nm cascode amplifier circuit to realize a full <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -band (220 to 325 GHz) S-MMIC amplifier module with monolithically integrated waveguide transitions.

MHEMT 소자의 DC/RF 특성에 대한 시뮬레이션 연구

GaAs나 InP 기반의 high electron mobility transistor (HEMT) 소자들은 우수한 마이크로파 및 밀리미터파 주파수 특성 및 이에 따른 우수한 저잡음 특성을 가지고 있다. GaAs 기판 위에 점진적으로 성장된 메타몰픽(Metamorphic) HEMTs (MHEMTs)는 InP 기판 위에 성정한 HEMT에 비해 비용 측면에서 커다란 장점을 가지고 있다. 본 논문에서는 이러한 MHEMT의 DC/RF 소신호 특성을 예측하기 위하여 InAlAs/InGaAs/GaAs MHEMT 소자들의 DC/RF 소신호 주파수 특성을 시뮬레이션하였다. 2차원 소자 시뮬레이터의 hydrodynamic 전송 모델을 사용하여 <TEX>$In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As$</TEX> 이종접합 구조를 갖는 제작된 0.1-<TEX>${\mu}m$</TEX> <TEX>${\Gamma}$</TEX>-게이트 MHEMT 소자에 대하여 파라미터 보정 작업을 수행한 후, MHEMT 소자들에 대해 DC 특성 및 RF 소신호 주파수 특성을 시뮬레이션하고 실험 데이터와 비교 분석하였다. 또한, 게이트 리세스 구조에 따른 MHEMT 소자들의 DC/RF 특성을 시뮬레이션하고 비교 분석하였다. GaAs-based metamorphic high electron mobility transistors (MHEMTs) and InP-based high electron mobility transistors (HEMTs) have good microwave and millimeter-wave frequency performance with lower minimum noise figure. MHEMTs have some advantages, especially for cost, compared with InP-based ones. In this paper, InAlAs/InxGa1-xAs/GaAs MHEMTs are simulated for DC/RF small-signal analysis. The hydrodynamic simulation parameters are calibrated to a fabricated 0.1-<TEX>${\mu}m$</TEX> <TEX>${\Gamma}$</TEX>-gate MHEMT device having the modulation-doped <TEX>$In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As$</TEX> heterostructure on the GaAs substrate, and the simulations for RF small-signal characteristics are performed, compared with the measured data, and analyzed for the devices. In addition, the simulations for the DC/RF characteristics of the MHEMTs with different gate-recess structures are performed, compared and analyzed.

Flip-Chip Packaging of Low-Noise Metamorphic High Electron Mobility Transistors on Low-Cost Organic Substrate

The rapid growth of high-frequency wireless communication demands high-performance packaging structures at low cost. A flip-chip interconnect is one of the most promising technologies owing to its low parasitic effect and high performance at high frequencies. In this study, the in-house fabricated In0.6Ga0.4As metamorphic high electron mobility transistor (mHEMT) device was flip-chip-assembled using a commercially available low-cost organic substrate. The packaged device with the optimal flip-chip structure exhibited almost similar DC and RF results to the bare die. An exopy-based underfill was applied to the improvement of reliability with almost no degradation of the electrical characteristics. Measurement results revealed that the proposed packaging structure maintained a low minimum noise figure of 3 dB with 6 dB associated gain at 62 GHz. Such a superior performance after flip-chip packaging demonstrates the feasibility of the proposed low-cost organic substrate for commercial high-frequency applications up to the W-band.

Flip-Chip Packaging of Low-Noise Metamorphic High Electron Mobility Transistors on Low-Cost Organic Substrate

Flip-Chip Packaging of Low-Noise Metamorphic High Electron Mobility Transistors on Low-Cost Organic Substrate

An Overview of Solid-State Integrated Circuit Amplifiers in the Submillimeter-Wave and THz Regime

We present an overview of solid-state integrated circuit amplifiers approaching terahertz frequencies based on the latest device technologies which have emerged in the past several years. Highlights include the best reported data from heterojunction bipolar transistor (HBT) circuits, high electron mobility transistor (HEMT) circuits, and metamorphic HEMT (mHEMT) amplifier circuits. We discuss packaging techniques for the various technologies in waveguide modules and describe the best reported noise figures measured in these technologies. A consequence of THz transistors, namely ultra-low-noise at cryogenic temperatures, will be explored and results presented. We also present a short review of power amplifier technologies for the THz regime. Finally, we discuss emerging materials for THz amplifiers into the next decade.

50-NM SELF-ALIGNED HIGH ELECTRON-MOBILITY TRANSISTORS ON GaAs SUBSTRATES WITH EXTREMELY HIGH EXTRINSIC TRANSCONDUCTANCE AND HIGH GAIN

We report the design, fabrication and characterization of metamorphic high electron-mobility transistors (MHEMTs) with self-aligned ohmic electrodes. In this work, asymmetrically recessed 50-nm Γ-gates have been successfully used as the shadow mask for ohmic metal deposition. Extremely high extrinsic transconductance over a wide drain bias from 0.1 to 1.25 V can be made possible by fabricating devices with small gate-source spacing, small source-drain spacing, and the non-alloyed ohmic. Measured maximum extrinsic transconductance of 3 S/mm is a new record for all HEMT devices on GaAs and equals the best results from InP -based HEMTs. The same devices also show a voltage gain of 22, maximum stable gain of 10.8 dB at 110 GHz, and breakdown voltage of 4.3 V, which all are the highest among any self-aligned HEMTs based on InGaAs channel. The outstanding performance is the result of the seamless integration of the asymmetric gate recess and Γ-gate-based self-aligned ohmic process.

Performance of Metamorphic Transistors with δ-Doped Structures

The interesting dc, microwave, and power performance of double and single δ-doped metamorphic high electron mobility transistors (MHEMTs), grown by molecular beam epitaxy, are studied. Because of the use of a double δ-doped structure, the increase of carrier density and uniform distribution of carriers within the channel are found. Therefore, the superior characteristics in the drain saturation current of 544.4 (523.9) mA/mm, extrinsic transconductance of 361.2 (312.4) mS/mm, drain current operation region of 236.9 (227.4) mA/mm, unity current gain cutoff frequency of 55.1 GHz, maximum oscillation frequency of 129.17 GHz, output power of 15.35 dBm, power gain of 24.65 dB, and power added efficiency of 39.4% could be achieved for a 0.6 × 100 μm2 gate dimension MHEMT at 300 (510) K. With increasing the temperature from 300 to 510 K, the slight temperature variation rates are also found for the studied device with a double δ-doped structure. On the other hand, the kink effect and impact ionization for the st...

A 60 GHz Broadband Stacked FET Power Amplifier Using 130 nm Metamorphic HEMTs

A V-band monolithic microwave integrated circuit power amplifier (PA) using metamorphic high electron mobility transistors (mHEMTs) is developed using a stacked-FET structure. Design methodology to optimize the series power combining power amplifiers at millimeter-waves is also presented. The fabricated PA using triple-stacked 130 nm mHEMTs shows a gain of 16 dB and a saturated output power of 20 dBm with a power added efficiency of 19% at 59 GHz. The 3 dB output power bandwidth is as wide as 15 GHz.

Development of Monolithic Microwave Integrated Amplifiers as Readout for Detectors at 4.2 K

Readout amplifiers with high bandwidth and extremely low power dissipation at liquid helium temperature for various superconducting detectors (e.g. SNSPD, HEB and MKID) are necessary to increase the small detector output signals. Different types of cryogenic amplifiers were developed for these applications. The required combination of low noise, large bandwidth, high voltage gain and low power consumption is a driving force for an on-going process of improvements. In this paper, the developments of cryogenic low power hybrid amplifiers, which are based on commercial p-HEMT transistors, will be reported and discussed. In addition, simulation and measurement results of the first developed monolithic microwave integrated circuit (MMIC) amplifier for low power operation will be presented. The MMICs are based on a metamorphic HEMT technology and are realized on a 3×1.5 mm2 area. First measurements at room temperature showed a bandwidth of 0.3 GHz up to 9 GHz with a gain of 23 dB at 90 mW and 1.3 GHz up to 8 GHz with 20 dB of gain at 42 mW, respectively. The power consumption could be reduced by cooling the devices down to 7.2 K. At almost identical bandwidths, the measured gain decreased to 10 dB at 22 mW and 15 dB at 9.5 mW.

Small-signal modeling approach to 0.1-μm metamorphic HEMTs for W-band coplanar MMIC amplifier design

We present an accurate and reliable modeling method for designing the W-band (75–110 GHz) small-signal millimeter-wave monolithic integrated circuit (MMIC) amplifiers with the GaAs-based 0.1-μm metamorphic high electron-mobility transistors (MHEMTs). For this, we propose an improved process control monitoring (PCM) pattern layout for the MHEMT modeling and a small-signal equivalent circuit model of 17 elements accounting for the feedback capacitance ( C pgd) and output conductance time delay ( τ ds). The modeling technique adopts a gradient optimizer with the initial values of the extrinsic parameter set determined from the cold-FET measurement avoiding the forward gate-biasing in a frequency range of 0.5–65 GHz and the intrinsic parameter set obtained at an operating hot-FET condition in our W-band design frequency range. On the basis of the proposed small-signal equivalent circuit model, we design and fabricate 1- and 2-stage W-band MMIC amplifiers using the MHEMTs (30-μm gate width, 2 gate fingers) and a coplanar waveguide-based MMIC process. The measurements of the fabricated MMIC amplifiers show an excellent agreement with simulation data in the design frequency range.

Gate-Length Scaling of Ultrashort Metamorphic High-Electron Mobility Transistors With Asymmetrically Recessed Gate Contacts for Millimeter- and Submillimeter-Wave Applications

We have fabricated and characterized ultrashort gate-length metamorphic high-electron mobility transistors (HEMTs) optimized for high gain performance for millimeter- and submillimeter-wave applications. In this paper, we have systematically evaluated the impact of gate length in the range of 25-50 nm on the device performance by exploring epitaxial layer designs, gate-to-channel distances, and recess widths. The study shows the 25-nm devices underperform their 50-nm counterparts in most of the key figures of merit including output conductance, voltage gain, off-state breakdown, on-state breakdown, and, most importantly, the maximum stable gain. This observation is actually in good agreement with the state-of-the-art results published so far, which indicate that the best overall performance of HEMTs for millimeter- and submillimeter-wave applications comes from devices with gate lengths ranging from 35 to 50 nm. The 25-nm devices, on the other hand, appear to have difficulty in achieving the proper vertical scaling for optimum gain, which is limited by the minimum gate layer thickness necessary to retain good Schottky characteristics. This limitation may eventually be overcome with the adoption of new materials used as the gate layer that can be integrated into the HEMT fabrication process.

Design and model studies for solid-state power amplification at 210 GHz

The high millimeter-wave (mmW) frequency range offers new possibilities for high-resolution imaging and sensing as well as for high data rate wireless communication systems. The use of power amplifiers of such systems boosts the performance in terms of operating range and/or data rate. To date, however, the design of solid-state power amplifiers at frequencies about 210 GHz suffers from limited transistor model accuracy, resulting in significant deviation of simulation and measurement. This causes cost and time consuming re-design iterations, and it obstructs the possibility of design optimization ultimately leading to moderate results. For verification of the small-signal behavior of our in-house large-signal transistor model, S-parameter measurements were taken from DC to 220 GHz on pre-matched transistors. The large-signal behavior of the transistor models was verified by power measurements at 210 GHz. After model modification, based on process control monitor (PCM) measurement data, the large-signal model was found to match the measurements well. A transistor model was designed containing the statistical information of the PCM data. This allows for non-linear spread analysis and reliable load-pull simulations for obtaining the highest available circuit performance. An experimental determination of the most suitable transistor geometry (i.e. number of gate fingers and gate width) and transistor bias was taken on 100 nm gate length metamorphic high electron mobility transistor (mHEMT) transistors. The most suitable combination of number of fingers, gate width and bias for obtaining maximum gain, maximum output power, and maximum power added efficiency (PAE) at a given frequency was determined.

A W-Band $\times$12 Multiplier MMIC With Excellent Spurious Suppression

This letter presents a single chip × 12 frequency multiplier MMIC for the W-band that is realized in a 100 nm metamorphic HEMT technology. To obtain the × 12 multiplication factor a multiplier chain of a doubler, a tripler and a doubler has been cascaded. The circuit has a 3 dB bandwidth of 15 GHz from 85 to 100 GHz. At 94 GHz, the multiplier achieves a saturated output power of more than 1 dBm and a conversion gain of 0 dB. The suppression of unwanted harmonics is better than 30 dBc at 94 GHz and better than 24 dBc within the entire bandwidth.