Metamorphic High Electron Mobility Transistor Research Articles

A broadband low noise amplifier in 70nm GaAs MHEMT process

In this paper, a broadband low noise amplifier (LNA) is presented with 70nm GaAs metamorphic high electron mobility transistor (MHEMT) process. The feedback and input/output impedance match techniques for broadband amplifier are presented. The stability, noise figure, gain flatness, and S-parameter performance of this LNA are analyzed and discussed. The small signal gain of the LNA is 20dB±0.2dB and noise figure of 0.86dB~1.35dB among operating from almost DC to 15GHz. This LNA exhibits reflection below -10dB, power dissipation of 70mW and chip area of 1.0mm*0.6mm. This LNA finds its application in many wideband systems.

LG = 20 nm High Performance GaAs Substrate Based Metamorphic Metal Oxide Semiconductor High Electron Mobility Transistor for Next Generation High Speed Low Power Applications

<i>L</i>_G = 20 nm High Performance GaAs Substrate Based Metamorphic Metal Oxide Semiconductor High Electron Mobility Transistor for Next Generation High Speed Low Power Applications

Thermal degradation of metamorphic HEMT InAlAs/InGaAs/InAlAs grown on GaAs substrates

termal annealing effect on electron transport properties of MHEMT nanostructures is studied for inhert and atmospheric conditions. Iti is revealed that surface modification is mainly responsible for changes in electron properties rather than dislocation sliding and threading into active layers.

2단계 게이트 리세스 방법으로 제작한 100 nm mHEMT 소자의 DC 및 RF 특성

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current(Idss), an extrinsic transconductance(gm) of 1,090 mS/mm and a threshold voltage(Vth) of −0.65 V. The fT and fmax obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).

Electron-Quantum Transport in Pseudomorphic and Metamorphic In0.2Ga0.8As-Based Quantum Wells

Metamorphic high-electron-mobility transistor (HEMT) structures based on deep In0.2Ga0.8As/In0.2Al0.8As quantum wells (0.7 eV for Γ electrons) with different metamorphic buffer designs are implemented and investigated for the first time. The electronic properties of metamorphic and pseudomorphic HEMT structures with the same doping are compared. It is found that, over a temperature range of 4–300 K, both the electron mobility and concentration in the HEMT structure with a linear metamorphic buffer are higher than those in the pseudomorphic HEMT structure due to an increase in the depth of the quantum well. Low-temperature magnetotransport measurements demonstrate that the quantum momentum-relaxation time decreases considerably in metamorphic HEMT structures because of enhanced small-angle scattering resulting from structural defects and inhomogeneities, while the dominant scattering mechanism in structures of both types is still due to remote ionized impurities.

Электронный квантовый транспорт в псевдоморфных и метаморфных квантовых ямах на основе In-=SUB=-0.2-=/SUB=-Ga-=SUB=-0.8-=/SUB=-As

AbstractMetamorphic high-electron-mobility transistor (HEMT) structures based on deep In_0.2Ga_0.8As/In_0.2Al_0.8As quantum wells (0.7 eV for Γ electrons) with different metamorphic buffer designs are implemented and investigated for the first time. The electronic properties of metamorphic and pseudomorphic HEMT structures with the same doping are compared. It is found that, over a temperature range of 4–300 K, both the electron mobility and concentration in the HEMT structure with a linear metamorphic buffer are higher than those in the pseudomorphic HEMT structure due to an increase in the depth of the quantum well. Low-temperature magnetotransport measurements demonstrate that the quantum momentum-relaxation time decreases considerably in metamorphic HEMT structures because of enhanced small-angle scattering resulting from structural defects and inhomogeneities, while the dominant scattering mechanism in structures of both types is still due to remote ionized impurities.

A $G$ -Band Broadband Balanced Power Amplifier Module Based on Cascode mHEMTs

The first full $G$ -band power amplifier module demonstrated in GaAs metamorphic high electron mobility transistor (mHEMT) technology has been developed for use as a driver amplifier in instrumentation. The circuit integrated in this module uses a compact balanced cascode topology and is based on a 35-nm mHEMT technology in a grounded coplanar waveguide environment. High compactness is achieved due to the use of a small ground-to-ground spacing of $14~\mu {\mathrm{ m}}$ and an advanced process with three metallization layers. The millimeter-wave integrated circuit exhibits a linear gain higher than 15.3 dB and return losses better than 10 dB from 118 to 236 GHz, which represents an ultrabroad relative bandwidth (RBW) of 67%. A peak output power of 10 dBm is achieved at 200 GHz. The WR-5 module uses broadband transitions, which show insertion losses of less than 1.5 dB. It demonstrates a small-signal gain that exceeds 13.4 dB in the whole $G$ -band (RBW ≥ 54%). Large-signal characterization exhibits power levels higher than 3.6 dBm from 130 to 210 GHz (RBW = 47%). This module achieves the highest bandwidth in $G$ -band and the highest output power when comparing it with modules based on similar technologies.

Analysis and Development of Submillimeter-Wave Stacked-FET Power Amplifier MMICs in 35-nm mHEMT Technology

This paper reports on the first stacked field-effect transistor (stacked-FET) submillimeter-wave monolithic integrated circuit (S-MMIC) power amplifier cell operating at 0.3 THz and the first stacked-FET medium power amplifier (MPA) at 240 GHz. Both circuits are fabricated using a 35-nm InGaAs-on-GaAs metamorphic high electron mobility transistor (mHEMT) technology with grounded coplanar waveguide lines. In both cases, compactness and performance are enhanced thanks to the use of an in-house process, based on three-metallization layers, instead of the usual two-layer process. The single-stacked cell exhibits an ultrawide small-signal 3-dB relative bandwidth (RBW) of $\hbox{47.3}{\%}$ , with output power levels higher than 4.3 dBm from 280 to 308 GHz (9.5%). The MPA MMIC combining four triple-stacked mHEMT cells in parallel achieves a small-signal 3-dB RBW of 24.2%, 10.8 dBm of output power, and a power-added efficiency of 5.02%. These values outperform the state-of-the-art results of MPAs published within a comparable technology.

Bandwidth Optimization Method for Reflective-Type Phase Shifters

This paper discusses a novel optimization technique for broadband reflective-type phase shifters (RTPS). The performance characteristics of an RTPS, including its achievable maximum phase shift and the corresponding average loss, are calculated on the basis of simulated or measured varactor data. In addition, the root-mean-square (rms) errors are evaluated to determine the broadband performance of the device. To extract the characteristics, a reciprocal, lossless matching network with arbitrary output impedance is connected in series to the varactor. The results are plotted on Smith charts, which yield an intuitive representation of the matching network area to achieve the design goals. The technique is verified by realizing a WR-3 band (220–325 GHz) RTPS microwave monolithic integrated circuit realized in a 50-nm metamorphic high electron mobility transistor InGaAs technology. The measured phase shift is 118° at the center frequency of 240 GHz with a bandwidth of 62 GHz. The rms phase and amplitude errors are lower than 5.6° and 0.67 dB, respectively.

Threading Dislocations in InGaAs/GaAs (001) Buffer Layers for Metamorphic High Electron Mobility Transistors

In order to evaluate various buffer layers for metamorphic devices, threading dislocation densities have been calculated for uniform composition In x Ga1−xAs device layers deposited on GaAs (001) substrates with an intermediate graded buffer layer using the LMD model, where LMD is the average length of misfit dislocations. On this basis, we compare the relative effectiveness of buffer layers with linear, exponential, and S-graded compositional profiles. In the case of a 2 μm thick buffer layer linear grading results in higher threading dislocation densities in the device layer compared to either exponential or S-grading. When exponential grading is used, lower threading dislocation densities are obtained with a smaller length constant. In the S-graded case, lower threading dislocation densities result when a smaller standard deviation parameter is used. As the buffer layer thickness is decreased from 2 μm to 0.1 μm all of the above effects are diminished, and the absolute threading dislocation densities increase.

Investigation of DC-RF and breakdown behaviour in Lg = 20 nm novel asymmetric GaAs MHEMTs for future submillimetre wave applications

In this work, we systematically investigated the DC-RF and breakdown voltage characteristics of Lg = 20 nm novel asymmetric GaAs metamorphic high electron mobility transistor (MHEMT) using Sentaurus-TCAD tool. The highlights of the novel asymmetric GaAs MHEMT are the cavity in the asymmetric Γ-gate region, n+-type In0.52Al0.48As/In0.53Ga0.47As/In0.75Ga0.25As cap layers and n+-type In0.52Ga0.48As vertical source/drain (S/D) regions. The influence of asymmetric gate recess width on DC-RF and ON and OFF-state breakdown voltage characteristics of the novel asymmetric GaAs MHEMT has been systematically investigated using hydrodynamic (HD) charge transport model. The physical models such as impact ionization model, high electric field electron mobility model, Shockley-Read-Hall and recombination models and density gradient model are also included during room temperature Sentaurus-TCAD simulation in order to accurately obtain the DC-RF and breakdown performance parameters. The 20 nm gate length novel asymmetric GaAs MHEMT obtained a maximum transconductance (gm_max) and drain current IDS_max of 3350 mS/mm and 1230 mA/mm respectively. The transit frequiencies fT and fmax obtained by the proposed 20 nm gate length GaAs MHEMT are 643 GHz and 1230 GHz respectively. The 20 nm gate length novel asymmetric GaAs MHEMT also exhibited an ON-state (BVON) and OFF-state (BVOFF) breakdown voltages of 3.1 V and 7.2 V respectively. To the best knowledge of authors, this is the record combination of DC–RF and breakdown performance parameter values obtained for GaAs MHEMT which makes them highly suitable for next generation high power high speed applications.

The influence of metamorphic-buffer layer design on the retention of characteristics of InGaAs/GaAs metamorphic HEMT

We have studied the influence of metamorphic-buffer layer design on the temporal (storage) stability of electrical characteristics of InGaAs/GaAs metamorphic high-electron-mobility transistors (MHEMTs). Using measurements of the Hall effect, it is established that transistor heterostructures with a metamorphic buffer based on In(Al)GaAs/InAlAs superlattices possess maximum values of the concentration and mobility of electrons in the MHEMT channel and show minimum susceptibility to temporal degradation.

22 nm InAs channel-based HEMTs on InP/GaAs substrates for future THz applications

In this work, the performance of nm InAs channel-based high electron mobility transistor (HEMT) on InP substrate is compared with metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. The devices features heavily doped InAs source/drain (S/D) regions, Si double δ-doping planar sheets on either side of the InAs channel layer to enhance the transconductance, and buried Pt metal gate technology for reducing short channel effects. The TCAD simulation results show that the InP HEMT performance is superior to GaAs MHEMT in terms of , and transconductance (). The 22 nm InP HEMT shows an of 733 GHz and an of 1340 GHz where as in GaAs MHEMT it is 644 GHz and 924 GHz, respectively. InGaAs channel-based HEMTs on InP/GaAs substrates are suitable for future sub-millimeter and millimeter wave applications.

Efficient EM Simulation of GCPW Structures Applied to a 200-GHz mHEMT Power Amplifier MMIC

The behaviour of grounded coplanar waveguide (GCPW) structures in the upper millimeter-wave range is analyzed by using full-wave electromagnetic (EM) simulations. A methodological approach to develop reliable and time-efficient simulations is proposed by investigating the impact of different simplifications in the EM modelling and simulation conditions. After experimental validation with measurements on test structures, this approach has been used to model the most critical passive structures involved in the layout of a state-of-the-art 200-GHz power amplifier based on metamorphic high electron mobility transistors (mHEMTs). This millimeter-wave monolithic integrated circuit (MMIC) has demonstrated a measured output power of 8.7 dBm for an input power of 0 dBm at 200 GHz. The measured output power density and power-added efficiency (PAE) are 46.3 mW/mm and 4.5 %, respectively. The peak measured small-signal gain is 12.7 dB (obtained at 196 GHz). A good agreement has been obtained between measurements and simulation results.

Stability Investigation of Large Gate-Width Metamorphic High Electron-Mobility Transistors at Cryogenic Temperature

An investigation of metamorphic high electron mobility transistor stability at cryogenic temperature is presented in this paper. Unlike in the case of two-finger transistors, the measurements of cooled four-finger devices with large gate widths exhibit unstable behavior in the form of steps in the current–voltage characteristics, discontinuities in the transconductance, and reduced gain. This unstable behavior has hampered the reliable realization of low-noise amplifiers for cryogenic applications. We study different gate-width devices with a multiport transistor model, allowing the separation of gate and drain feeder structures from the active part of the transistor. The simulation reveals the presence of resonances in the frequency region of several hundreds of gigahertz. We demonstrate that the resonances disappear when an air bridge is placed across the fingers of the drain feeder structure, and confirm the stabilizing effect of the air bridge both on device and circuit level by cryogenic measurements.

20-nm enhancement-mode metamorphic GaAs HEMT with highly doped InGaAs source/drain regions for high-frequency applications

ABSTRACTIn this article, the DC and RF performance of a SiN passivated 20-nm gate length metamorphic high electron mobility transistor (MHEMT) on GaAs substrate with highly doped InGaAs source/drain (S/D) regions have investigated using the Synopsys TCAD tool. The 20-nm enhancement-mode (E-mode) MHEMT device also features δ-doped sheets on either side of the In0.53Ga0.47As/InAs/In0.53Ga0.47As channel which exhibits a transconductance of 3100 mS/mm, cut-off frequency (fT) of 740 GHz and a maximum oscillation frequency (fmax) of 1040 GHz. The threshold voltage of the device is found to be 0.07 V. The room temperature Hall mobilities of the 2-dimensional sheet charge density are measured to be over 12,600 cm2/Vs with a sheet charge density larger than 3.6 × 1012 cm−2. These high-performance E-mode MHEMTs are attractive candidates for sub-millimetre wave applications such as high-resolution radars for space research, remote atmospheric sensing, imaging systems and also for low noise wide bandwidth amplifier for future communication systems.

Structure characterization of MHEMT heterostructure elements with In0.4Ga0.6As quantum well grown by molecular beam epitaxy on GaAs substrate using reciprocal space mapping

The crystallographic parameters of elements of a metamorphic high-electron-mobility transistor (MHEMT) heterostructure with In0.4Ga0.6As quantum well are determined using reciprocal space mapping. The heterostructure has been grown by molecular-beam epitaxy (MBE) on the vicinal surface of a GaAs substrate with a deviation angle of 2° from the (001) plane. The structure consists of a metamorphic step-graded buffer (composed of six layers, including an inverse step), a high-temperature buffer of constant composition, and active high-electron-mobility transistor (HEMT) layers. The InAs content in the metamorphic buffer layers varies from 0.1 to 0.48. Reciprocal space mapping has been performed for the 004 and 224 reflections (the latter in glancing exit geometry). Based on map processing, the lateral and vertical lattice parameters of InxGa1–xAs ternary solid solutions of variable composition have been determined. The degree of layer lattice relaxation and the compressive stress are found within the linear elasticity theory. The high-temperature buffer layer of constant composition (on which active MHEMT layers are directly formed) is shown to have the highest (close to 100%) degree of relaxation in comparison with all other heterostructure layers and a minimum compressive stress.

Prospects and Limitations of Stacked-FET Approaches for Enhanced Output Power in Voltage-Controlled Oscillators

This paper reports on the emerging potential of a stacked field-effect transistor (FET) approach with respect to maximum achievable RF output power with special remarks on high electron-mobility transistor (HEMT) based series feedback oscillator monolithic microwave integrated circuits (MMICs). A stacked-FET oscillator can provide benefit in several ways—in the form of an improved RF output power, a high drain efficiency, or a stabilized oscillation behavior, even for changing load impedances. The limitation of the maximum number of transistors is analyzed with reference to the maximum achievable output power of stacked devices. This is done by describing the compromise between an increased voltage swing and a decreased RF output current. The output current is decreased since the current gain of a common gate device is smaller than unity. Based on the proposed theory a W-band stacked-FET voltage-controlled oscillator MMIC with an output power of 15 dBm and a drain efficiency of 23.3% was realized. The MMIC is based on the Fraunhofer IAF 50-nm gate-length metamorphic HEMT process. For an advanced evaluation of the power capability and the optimum target load of the utilized technology, an active W-band on-wafer load–pull system was implemented.

Fabrication of 80-nm T-gate high indium In0.7Ga0.3As/In0.6Ga0.4As composite channels mHEMT on GaAs substrate with simple technological process**Project supported by the Key Laboratory of Nano-Devices and Applications, Nano-Fabrication Facility of SINANO, Chinese Academy of Sciences, the National Natural Science Foundation of China (Nos. 61274077, 61474031, 61464003), the Guangxi Natural Science Foundation (Nos. 2013GXNSFGA019003, 2013GXNSFAA019335), the National Basic Research Program of China

An 80-nm gate length metamorphic high electron mobility transistor (mHEMT) on a GaAs substrate with high indium composite compound-channels In0.7Ga0.3 As/In0.6Ga0.4 As and an optimized grade buffer scheme is presented. High 2-DEG Hall mobility values of 10200 cm2/(V·s) and a sheet density of 3.5 × 1012 cm−2 at 300 K have been achieved. The device's T-shaped gate was made by utilizing a simple three layers electron beam resist, instead of employing a passivation layer for the T-share gate, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate and simplifying the device manufacturing process. The ohmic contact resistance Rc is 0.2 ω·mm when using the same metal system with the gate (Pt/Ti/Pt/Au), which reduces the manufacturing cycle of the device. The mHEMT device demonstrates excellent DC and RF characteristics. The peak extrinsic transconductance of 1.1 S/mm and the maximum drain current density of 0.86 A/mm are obtained. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 246 and 301 GHz, respectively.

Accuracy improvement of small‐signal model minimising parameter sensitivity based on de‐embedded sub‐model method at W‐band

A highly reliable small-signal parameter extraction method for parasitic elements of the 0.1-µm GaAs metamorphic high electron mobility transistors is presented. De-embedding scheme for the coplanar waveguide (CPW) feeding structure is utilised in this method in a frequency range of 0.5–110 GHz with an enhancement approach to the correction of source inductance parameter sensitivity derived from oscillating measurements. The parasitic extrinsic capacitances are determined by modelling an ∏ equivalent circuit including the interaction between the sub-model and the CPW feedings. From this method, the authors achieved the most accurate parameter prediction with an effective fitting error of 10.83% among the small-signal models reported to date.