Pseudomorphic High Electron Mobility Transistor Research Articles

Frequency Selective Degeneration for 6–18 GHz GaAs pHEMT Broadband Power Amplifier Integrated Circuit

In this paper, a frequency selective degeneration technique using a parallel network with a resistor and capacitor is proposed for a 6–18 GHz GaAs pseudomorphic high electron mobility transistor (pHEMT) broadband power amplifier integrated circuit (PAIC). The proposed degeneration network is applied to the source of the transistor to flatten the frequency response of the transistor in conjunction with feedback and resistor biasing circuits. An almost uniform frequency response was achieved at the wide frequency band through optimizing the values of the capacitor and resistor for the degeneration circuit. Single-section matching networks for small chip sizes were adopted for the two-stage amplifier following the flat frequency characteristics of the degenerated transistor. The proposed broadband PAIC for the 6 to 18 GHz band was fabricated using a 0.15 μm GaAs pHEMT process and had a chip size of 1.03 × 0.87 mm2. The PAIC exhibited gain of 15 dB to 17.2 dB, output power of 20.5 dBm to 22.1 dBm, and linear output power of 11.9 dBm to 13.45 dBm, which satisfies the IMD3 of −30 dBc in the 6–18 GHz band. Flatness for the gain and output power was achieved as ±1.1 dB and ±0.8 dB, respectively.

A Ku-Band GaAs Multifunction Transmitter and Receiver Chipset

This paper presents a Ku-band monolithic multifunction transmitter and receiver chipset fabricated in 0.25-μm GaAs pseudomorphic high-electron mobility transistor technology. The chipset achieves a high level of integration, including a 4-bit 360° digital phase shifter, 5-bit 15.5-dB digital attenuator, amplifier and 9-bit digital serial-to-parallel converter for digital circuit control. Since the multifunction chipset includes a medium power amplifier and a low-noise amplifier, it features high P1dB and low noise figures over the full Ku-band frequencies. The multifunction transmitter shows a peak gain of 16.5 dB with output P1dB of 19.2 dBm at 15 GHz. The multifunction receiver shows a peak gain of 17.3 dB with noise figure of 2.5 dB at 15 GHz. The attenuation range is 15.5 dB with a step of 0.5 dB and the phase shift range is 360° with a step of 22.5°. Each chip area of the transmitter and receiver is 4.2 × 2.8 mm2.

Experimental insight into the temperature effects on DC and microwave characteristics for a GaAs pHEMT in multilayer 3‐D MMIC technology

This paper is focused on studying the behavior of a GaAs pseudomorphic high electron mobility transistors (pHEMT) with respect to the temperature. The tested pHEMT is realized using the multilayer three-dimensional (3-D) monolithic microwave integrated circuit (MMIC) technology. The analysis is based on temperature-dependent on-wafer measurements carried out from 298 K to 373 K. The experiments consist of DC characteristics and scattering parameters in the broad frequency range from 45 MHz to 40 GHz. The effect of the temperature on the measured transistor performance is analyzed in detail and then, to gain a better insight and understanding of the device behavior, the achieved measurements are used for extraction and validation of a small-signal equivalent-circuit model for different temperature conditions. This study shows that, by heating the studied device, the observed performance variations depend remarkably on the selected bias condition. In particular, the output current and transconductance are degraded at higher gate-source voltage and improved as the transistor is driven towards the pinch-off. This is due to the counterbalancing of temperature-dependent effects contributing in opposite ways to the resultant behavior of the transistor. Therefore, depending on the given application, an appropriate selection of the bias and temperature conditions is essential to guarantee adequate transistor performance.

8-12 GHz pHEMT MMIC Low-Noise Amplifier for 5G and Fiber-Integrated Satellite Applications

The fifth-generation (5G) radio access technology promises to revolutionise integrated earth-space communications applications for ubiquitous, seamless and broadband services. The assigned sub-6 GHz and millimetre-wave 5G frequencies require the sensitivity of the receiver front-end subsystem(s) to detect and amplify the desired signal at a noise floor of less than -90 dBm for a cost-effective infrastructure deployment. This paper presents a broadband monolithic microwave integrated circuit (MMIC) low-noise amplifier (LNA) design based on a 0.15 µm gate length Indium Gallium Arsenide (InGaAs) pseudomorphic high electron mobility transistor (pHEMT) technology for 5G and fiber-integrated satellite communications applications. The designed three-stage 8-12 GHz LNA implements a common-source topology. The MMIC LNA subsystem performance demonstrates an industry-leading in-band gain response of 40 dB; a noise figure of 1.0 dB; and a power dissipation of 43 mW. For a constant bandwidth receiver, the sensitivity changes by approximately 1.5 dB over the operating satellite signal frequency. Similarly, for a variable bandwidth receiver, the sensitivity changes by approximately 1.5 dB over the channel bandwidth. Moreover, the sensitivity margin of the designed LNA is 40 dB and this holds a great promise for real-time radio access component-level reconfiguration applications.

VCSEL Array-Based Gigabit Free-Space Optical Femtocell Communication

We present an indoor free-space optical communication system to augment traditional short-range radio frequency wireless links. In this system, we integrated a high-frequency, high-current laser driver with an 850 nm wavelength, 500 mW vertical cavity surface emitting laser (VCSEL) array to transmit high speed optical signals with a large spatial coverage. The large current-bandwidth capability of the laser driver is enabled by a distributed current driver design utilizing three enhanced-mode pseudomorphic high electron mobility transistors. At the optical receiver end, a high-sensitivity avalanche photodiode is used to achieve high speed optical signal detection without any light concentrating optical device and is tolerant to angular deviation up to 27°. The communication link described in this article forms an optical femtocell with an area of 100 cm2 at a distance of three meters from the transmitter. A bit error rate of less than 10−4 is achieved throughout the optical femtocell in a normal in-door environment. On-off-keying and four-level pulse amplitude modulation schemes are both implemented with 1.25 Gb/s and 2 Gb/s data rate respectively, using the hardware described in this article. Additionally, the overall performance of this free-space optical link is evaluated in terms of viewing angle, distance range, and bit error rate.

Analysis and design of a stacked power amplifier with 196% fractional bandwidth using equivalent circuit model

Stacked structure is a good solution to overcome the low output voltage swing provided by a single device. When several devices are stacked, the bandwidth and output power are multiple times higher. This article analyzes the small-signal voltage gain of the stacked structure, deriving the gain expression of the high-frequency model and simplified model. Based on the specific device parameter, the different small-signal voltage gains between the two models are compared and the designed stacked structure is proved to obtain a flat gain at low frequencies below about 3 GHz. To our best knowledge, this is the first article to analyze the gain flatness of stacked structure with two equivalent circuit models. To verify the stacked theory, a pseudomorphic high-electron-mobility transistor（PHEMT） power amplifier (PA) is implemented using 0.25 μm Gallium arsenide (GaAs) technology. The PA achieves an ultra-high bandwidth of 30 MHz to 3 GHz and a linear gain of 21 dB ± 1.5 dB. At a 16-V drain bias voltage, a saturated output power of higher than 2 W and a peak power-added efficiency (PAE) of 44.1% are attained.

Temperature-Dependent Study of AlGaAs/InGaAs Integrated Depletion/Enhancement-Mode High Electron Mobility Transistors with Virtual Channel Layers

Recently, we have implemented the direct-coupled FET logic inverters by the AlGaAs/InGaAs co-integrated depletion-mode (D-mode) and enhancement-mode (E-mode) pseudomorphic high electron mobility transistors (PHEMTs) with virtual channel layers in this journal. In this article, the temperature-dependent characteristics of the above integrated PHEMTs will be demonstrated. Due to the two-dimensional electron gas (2DEG) located in the undoped In0.22Ga0.78As layer between two large energy-gap Al0.24Ga0.76As barrier layers, the integrated devices exhibit excellent thermal stability for the good confinement effect in the 2DEG channel. Experimental results exhibit that the maximum transconductance decreases from 162.2 (174.4) to 125.0 (105.8) mS mm−1 for the studied D-mode (E-mode) device as the temperature increases from 300 to 450 K. In addition, the maximum drain current reduces from 366.4 (379.6) at 300 K to 286.4 (254.6) mA mm−1 at 450 K. Significantly, a considerably low temperature coefficient on threshold voltage (∂Vth/∂T) of −0.266 (−0.866) mV K−1 for the D-mode (E-mode) PHEMT is measured, which is superior to the previous reports of the related GaAs-substrate transistors.

Design of X-Band Low Noise Amplifier For Radar Applications

This paper presents an analysis for a single stage Low Noise Amplifier (LNA) for X-band radar application. The LNA is designed using commercially Pseudomorphic High Electron Mobility Transistor (P-HEMT). The LNA is designed to achieve low noise figure, high gain and a better matching to 50 Ω at both input and output terminals. Cascaded and cascoded circuit topologies were implied to achieve the targeted requirements. In addition, negative feedback technique is utilized to increase the operating bandwidth. The circuit is designed and simulated using Advanced Design System (ADS) tools. The design showed good dynamic range with moderate gain. The cascode LNA resulted in better noise figure (NF).

Doping-Dependent Nonlinear Electron Mobility in GaAs|In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-As Coupled Quantum-Well Pseudo-Morphic MODFET Structure

We analyze the asymmetric delta-doping dependence of nonlinear electron mobility μ of GaAs|InxGa1-xAs double quantum-well pseudo-morphic modulation doped field-effect transistor structure. We solve the Schrodinger and Poisson's equations self-consistently to obtain the sub-band energy levels and wave functions. We consider scatterings due to the ionized impurities (IMP), alloy disorder (AL), and interface roughness (IR) to calculate μ for a system having double sub-band occupancy, in which the inter-sub-band effects play an important role. Considering the doping concentrations in the barriers towards the substrate and surface sides as Nd1 and Nd2, respectively, we show that variation of Nd1 leads to a dip in μ near Nd1=Nd2, at which the resonance of the sub-band states occurs. A similar dip in μ as a function of Nd1 is also obtained at Nd1=Nd2 by keeping (Nd1+Nd2) unchanged. By increasing the central barrier width and well width, the dip in μ becomes sharp. We note that even though the overall μ is governed by the IMP- and AL-scatterings, the dip in μ is mostly affected through substantial variation of the sub-band mobilities due to IR-scattering near the resonance. Our results of nonlinear electron mobility near the resonance of sub-band states can be utilized for the performance analysis of GaAs|InGaAs pseudo-morphic quantum-well field-effect transistors. Keywords: asymmetric double quantum wells, GaAs|InxGa1-xAs structures, nonlinear electron mobility, pseudo-morphic HEMT structures, resonance of sub-band states.

Microwave Linear Characterization Procedures of On-Wafer Scaled GaAs pHEMTs for Low-Noise Applications

This contribution deals with the microwave linear characterization and noise figure measurement of four on-wafer GaAs pseudomorphic high-electron mobility transistors having scaled gate widths. The proposed measurement campaign has been fulfilled in two different laboratories: The University of Messina, Italy and US Naval Research Laboratory, Washington, DC, USA. Two equivalent approaches have been straightforwardly employed: a standard tuner-based technique and a novel tuner-less technique. The effectiveness of the novel technique has been confirmed as carried out independently by the two laboratories, evidencing the benefits of both techniques. The proposed experimental activity highlights the applicability of the tunerless technique for the noise characterization of advanced on-wafer devices without the constraint imposed by the addition of a source tuner to the standard measurement setup.

Uniformity investigation of pHEMTs in 3-D MMICs for pre and post multilayer fabrication

This study deals with the uniformity investigation and comparison on the typical behaviour of pseudomorphic high electron mobility transistors (pHEMTs) before and after the 3-D multilayer fabrication. There are seven multilayer fabricated pHEMTs compared with the seven virgin pHEMTs based on drain-source input current, output current, transconductance, off state leakage behaviour, threshold voltage, knee voltage, on-resistance, Schottky barrier height, ideality factor, reverse saturation current, small signal gain and current gain. Below 10% changes in performance can be seen after multilayer fabrication compare to virgin samples and apart from these exceptions, the discrepancies are well within the tolerance and less than 3% in terms of Schottky behaviour. We show that, the application of the 3D-MMIC technology does not cause any visible destruction of pHEMTs performance using seven different samples before and after the multilayer fabrication.

Fabrication and application of GaAs-on-insulator structure prepared through liquid-phase chemical-enhanced oxidation

This paper details the fabrication and characteristics of Schottky-gate InGaP/InGaAs pseudomorphic high-electron-mobility transistors (PHEMTs) with GaAs-on-insulator (GOI) structure obtained using liquid-phase chemical-enhanced oxidation (LPCEO). Two oxidation times were investigated, and the PHEMT with GOI structure prepared through 15 min of LPCEO was discovered to have improved subthreshold characteristics, suppressed gate leakage current density, larger breakdown voltage, and less low-frequency noise owing to the isolated oxide film. Therefore, the proposed PHEMT with GOI structure prepared through LPCEO is promising for group III-V compound device applications.

Thermal Burnout Effect of a GaAs PHEMT LNA Caused by Repetitive Microwave Pulses

The thermal burnout effect of a gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (PHEMT) low-noise amplifier (LNA) caused by repetitive microwave pulses is studied by theoretical analyses, simulations, and experiments. The theoretical model for thermal burnout under a single microwave pulse injection is first acquired by analyzing the power absorption in the electrical procedure and the heat distribution in the thermal procedure. By adopting two new assumptions and using the linear superposition theorem, the theoretical model for thermal burnout under a repetitive microwave pulse injection is acquired by further extension. Through derivation, the analytical relationship among the thermal burnout power threshold, the pulsewidth in a cycle, the pulse repetition frequency (PRF) and the pulse number is acquired. Because some assumptions and approximations are adopted, both the pulsewidth in a cycle and the total repetitive microwave pulselength must be between 10-ns scale and 1-μs scale. It shows that the theoretical results agree well with the simulation and experimental results. A minimum of two sets of data by experiment or simulation are needed to fit the analytical relationship. Therefore, experimental or simulation costs can be substantially reduced, and a helpful reference for

Second-Harmonic Injection Linearization of Millimeter-Wave FET Resistive Mixers

This letter demonstrates the application of the second-harmonic injection linearization technique in a field-effect transistor (FET) resistive mixer operating at $Ka$ -band. The single-ended mixer uses a 0.15- $\mu \text{m}$ gallium arsenide (GaAs) pseudomorphic high electron-mobility transistor (pHEMT) at its core. Compared to the same mixer without the second-harmonic injection, the linearized mixer achieves an improvement of up to 8 dB in the third-order intermodulation (IM3) levels while leaving the fundamental output power and noise figure unaffected. To the best of authors’ knowledge, this is the first demonstration of the technique with a mixer operating at millimeter-wave frequencies.

Analysis and Design of a 0.1–23 GHz LNA MMIC Using Frequency-Dependent Feedback

In this brief, a 0.1 to 23 GHz low-noise amplifier (LNA) employing a frequency-dependent feedback loop (FDFL) is presented. As predicted theoretically, the optimized FDFL enhances the bandwidth and the gain flatness in desired frequency band through purposely designing the feedback characteristics from negative to positive corresponding to the frequency. Based on the theoretical analysis of bandwidth enhancement, noise characteristic, and linearity of FDFL, an ultra-broadband LNA, utilizing the proposed technique, is designed and verified experimentally by a three-stage LNA chip implemented using a 0.15- $ {\mu }\text{m}$ GaAs pseudomorphic high electron-mobility transistor process. Measurement results show that the LNA obtains an average gain of 27.4 dB and noise figure of 2.7 to 4 dB in a frequency band from 0.1 to 23 GHz, with a compact chip area of only 1.36 mm2, including input/output testing pads.

A Compact 40-GHz Doherty Power Amplifier With 21% PAE at 6-dB Power Back Off in 0.1-$\mu$ m GaAs pHEMT Process

This letter presents a monolithic 40-GHz Doherty power amplifier (PA) fabricated in 0.1- $\mu \text{m}$ depletion mode (D-mode) gallium arsenide (GaAs) pseudomorphic high electron mobility transistor process. Different from most Doherty PAs, this PA occupies a compact chip size of 2.25 mm2 because of the power-combining techniques. The measured results show a small signal gain of 12.7 dB, an output 1-dB compression point ( $\text{OP}_{\mathrm {1\,dB}}$ ) of 19.2 dBm and saturated output power ( $P_{\mathrm {sat}}$ ) of 23.1 dBm at 40 GHz. Meanwhile, this PA achieves peak power added efficiency (PAE) of 28.5% and PAE of 21.1% at 6-dB power back off (PBO) from $P_{\mathrm {sat}}$ . Finally, the bandwidth of this well-improved backed-off efficiency is obtained from 39 to 41 GHz with an output third-order intercept point (OIP3) of 20 dBm. Among published Ka -band GaAs Doherty PAs, this work exhibits the best 6-dB backed-off efficiency around 38 GHz, supporting the upper-frequency band for 5G wireless systems.

Direct ${E}$ -Field Measurement and Imaging of Oscillations Within Power Amplifiers

We present, for the first time, a measurement system that is capable of directly detecting and identifying the physical location of an oscillation within radio frequency (RF) and microwave power amplifiers (PAs). The method uses a combined external electrooptic, nonlinear vector network analyzer, and vector load-pull measurement system, which allows the measurement of cross-frequency phase-coherent multiharmonic vector electric fields ( ${E}$ -fields) above the transistor with an 8- $\mu \text{m}$ spatial resolution and 20 MHz–40 GHz bandwidth. Raster scans above the amplifier allow the time-domain ${E}$ -fields to be animated and superimposed on top of the amplifier image, enabling immediate identification of any oscillations by direct inspection. The method is first demonstrated on a low-power PA composed of two parallel 0.1-W pseudomorphic high electron mobility transistors that is intentionally designed to have an odd-mode oscillation. The applicability of the method is further demonstrated by measuring and animating in-package parametric odd-mode oscillations within a 260-W laterally diffused metal–oxide–semiconductor transistor operating at 2.2 GHz under pulsed RF conditions with 10- $\mu \text{s}$ pulses and 10% duty cycle. The measurement and identification technique are applicable to all semiconductor devices as the external ${E}$ -field is noninvasively measured above the amplifier.

A 0.1–52-GHz Triple Cascode Amplifier With Resistive Feedback

In this letter, a 0.1–52-GHz amplifier is designed and fabricated using a 0.15- $\mu \text{m}~{E}$ -mode GaAs pseudomorphic high electron-mobility transistor (pHEMT) process. To extend the gain bandwidth, a triple cascode amplifier with resistive feedback is employed. Moreover, by introducing several inductors between the transistors, the gain flatness and the noise figure are significantly enhanced. The measurement results indicate that the designed amplifier shows a 20.5-dB average gain, 3.9–6.2-dB noise figure, 5–12-dBm OP1 dB, and 14–22.5-dBm OIP3 in the frequency range from 0.1 to 52 GHz, respectively. The fabricated amplifier occupies a chip area of 1.6 mm $\times \,\, 0.89$ mm including the testing pads.

A 4–20 GHz, multi‐watt level, fully integrated push–pull distributed power amplifier with wideband even‐order harmonic suppression

This study presents the first fully integrated, push–pull, high power distributed amplifier (DA) for wideband applications in 0.25 µm Gallium arsenide (GaAs) pseudomorphic high electron mobility transistor process. A triple-stacked field-effect transistor cell is employed for each stage of the DA along with the non-uniform distributed power amplifier topology to maximise the output power. The experimental results show that the amplifier exhibits from 7 to 10 dB gain with vi30–32 dBm output power at 1 dB compression (P1 dB) and 32–35.4 dBm saturated output power (Psat) covering a frequency bandwidth from 4 to 20 GHz. The measured second harmonic suppression is >33 dBc from 8 to 40 GHz at the P1 dB operating condition.

Characterization of InP-based pseudomorphic HEMT with T-gate

This paper proposes two structures of InAlAs/InGaAs-based pseudomorphic high electron mobility transistor (PHEMT): one with rectangular-gate and another with T-gate. Both the proposed PHEMTs consist of an In0.52Al0.48As supply/barrier layer and In0.53Ga0.47As channel layer built on an InP substrate. The proposed InAlAs/InGaAs-based PHEMT with rectangular-gate exhibits 1.32 × increment in drain current and 0.55 × decrement in threshold voltage compared to those of AlGaAs/GaAs-based previously proposed HEMT on GaAs substrate. This is because of the role of indium in the new materials used for the proposed device layers. The proposed InAlAs/InGaAs-based PHEMT with T-gate exhibits further improvements in DC and RF characteristics. The PHEMT with T-gate shows 1.42 ×/1.14 ×/1.4 × increment in drain current/cut-off frequency/maximum oscillation frequency respectively compared to the PHEMT with rectangular-gate. It also exhibits 0.67 × decrement in noise figure compared to that of PHEMT with rectangular-gate. All the theoretical results are verified with the simulation results obtained while analyzing the structures considered in this work. The simulation results were recorded while simulating the devices using Silvaco Atlas.