Single High Electron Mobility Transistor Research Articles

Numerical study on THz radiation of two-dimensional plasmon resonance of GaN HEMT array

The GaN high electron mobility transistor (HEMT) has been considered as a potential terahertz (THz) radiation source, yet the low radiation power level restricts their applications. The HEMT array is thought to improve the coupling efficiency between two-dimensional (2D) plasmons and THz radiation. In this work, we investigate the plasma oscillation, electromagnetic radiation, and the integration characteristics of GaN HEMT targeting at a high THz radiation power source. The quantitative radiation power and directivity are obtained for integrated GaN HEMT array with different array periods and element numbers. With the same initial plasma oscillation phase among the HEMT units, the radiation power of the two-element HEMT array can achieve 4 times as the single HEMT radiation power when the array period is shorter than 1/8 electromagnetic wavelength. In addition, the radiation power of the HEMT array varies almost linearly with the element number, the smaller array period can lead to the greater radiation power. It shows that increasing the array period could narrow the main radiated lobe width while weaken the radiation power. Increasing the element number can improve both the radiation directivity and power. We also synchronize the plasma wave phases in the HEMT array by adopting an external Gaussian plane wave with central frequency the same as the plasmon resonant frequency, which solves the problem of the radiation power reduction caused by the asynchronous plasma oscillation phases among the elements. The study of the radiation power amplification of the one-dimensional (1D) GaN HEMT array provides useful guidance for the research of compact high-power solid-state terahertz sources.

Model and Simulation of GaN-Based Pressure Sensors for High Temperature Applications—Part II: Sensor Design and Simulation

In this part, design and optimization guidelines are presented for an Aluminium Gallium Nitride (AlGaN)/GaN-on-Silicon (Si) High Electron Mobility Transistor (HEMT)-based pressure sensor, for high temperature applications. The work presented here is based on the compact model developed and presented in Part I. The nature of the developed model allows not only the simulation of the sensor behavior for the case of a single HEMT sensor, but also for the case of a Wheatstone bridge configuration. Both configurations are analyzed in terms of temperature compensation, pressure sensitivity, and mechanical failure limits. Based on the presented analysis, we propose an optimized design of a temperature compensated pressure sensor for a pressure operation range between −10 bar and 10 bar, and for temperatures up to 500 °C. The optimization includes the epitaxial design, HEMT placement on the sensor membrane, membrane thickness and geometry, and the optimal biasing points for a maximum sensitivity. Strong temperature compensation can be achieved with less than 0.3 % sensitivity deviation up to 500 °C. The maximum sensitivity of 2.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mV</sup> / <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">barV</sub> can be achieved by applying a gate voltage near the pinch-off voltage of the device or as proposed here, by recessing the barrier locally under the gate. In addition, design guidelines for other pressure ranges are given. The approach taken here can be applied to a different epitaxial design with different barrier composition and substrate using the same compact model.

A Low-Power Microwave HEMT $LC$ Oscillator Operating Down to 1.4 K

High-electron-mobility transistors (HEMTs) based on 2-D electron gases (2DEGs) in III–V heterostructures have superior mobility compared with the transistors of silicon-based complementary metal–oxide–semiconductor technologies. The large mobility makes them attractive not only for low-noise and high-power microwave applications but also for low-power applications down to deep cryogenic temperatures. Here, we report on the design and characterization of a low-power HEMT LC Colpitts oscillator operating at 11 GHz whose minimum power consumption is $90~\mu \text{W}$ at 300 K and $4~\mu \text{W}$ at 1.4 K. The fully integrated oscillator is based on a single HEMT transistor having a gate length of 70 nm and realized using a 2DEG in In0.7Ga0.3As. The power consumption of the realized oscillator is the lowest reported in the literature so far for an LC oscillator operating in the same frequency range. In order to investigate the behavior of the oscillator, we also performed a detailed characterization of a stand-alone HEMT transistor from 1.4 to 300 K with a static magnetic field from 0 to 8 T. From the extracted values of the transistor parameters, we estimate and compare the minimum power necessary to start-up oscillations for two different Colpitts topologies.

Space-Borne Electron Accelerator Design

Renewed interest in active experiments with relativistic particle beams in space has led to the development of solid-state radio-frequency (RF) linear accelerators (linac) that can deliver MeV electron beams but operate with low-voltage DC power supplies. The solid-state RF amplifiers used to drive the accelerator are known as high-electron mobility transistors (HEMTs), and at C-band (5-6 GHz) are capable of generating up to 500 watts of RF power at 10% duty factor in a small package, i.e., the size of a postage stamp. In operation, the HEMTs are powered with 50V DC as their bias voltage; they thus can tap into the spacecraft batteries or electrical bus as the primary power source. In this paper we describe the initial testing of a compact space-borne RF accelerator consisting of individual C-band cavities, each independently powered by a gallium nitride (GaN) HEMT. We show preliminary test results that demonstrate the beam acceleration in a single C-band cavity powered by a single HEMT operating at 10% duty factor. An example of active beam experiments in space that could benefit from the HEMT-powered accelerators is the proposed Magnetosphere-Ionosphere Connection (CONNEX) experiment [Dors et al., 2017].

A single chip electron spin resonance detector based on a single high electron mobility transistor

Single-chip microwave oscillators are promising devices for inductive electron spin resonance spectroscopy (ESR) experiments on nanoliter and subnanoliter samples. Two major problems of the previously reported designs were the large minimum microwave magnetic field (0.1–0.7 mT) and large power consumption (0.5–200 mW), severely limiting their use for the investigation of samples having long relaxation times and for operation at low temperatures. Here we report on the design and characterization of a single-chip ESR detector operating with a microwave magnetic field and a power consumption orders of magnitude lower compared with previous designs. These significant improvements are mainly due to the use of a high electron mobility transistor (HEMT) technology instead of a complementary metal-oxide semiconductor (CMOS) technology. The realized single-chip ESR detector, which operates at 11.2 GHz, consists of an LC Colpitts oscillator realized with a single high-electron mobility transistor and a co-integrated single turn planar coil having a diameter of 440 μm. The realized detector operates from 300 K down to 1.4 K, at least. Its minimum microwave magnetic field is 0.4 μT at 300 K and 0.06 μT at 1.4 K, whereas its power consumption is 90 μW at 300 K and 4 μW at 1.4 K, respectively. The experimental spin sensitivity on a sensitive volume of about 30 nL, as measured with a single crystal of α,γ-bisdiphenylene-β-phenylallyl (BDPA)/benzene complex, is of 8 × 1010 spins/Hz1/2 at 300 K and 2 × 109 spins/Hz1/2 at 10 K, respectively. In a volume of about 100 pL, located in proximity to the coil wire, the spin sensitivity improves by two orders of magnitude.

CIRCUITS AND ACTIVE ANTENNAS FOR ULTRA-WIDE BAND PULSE GENERATION AND TRANSMISSION

In this paper, the design and development of a novel active antenna including circuits for Ultra-wide band (UWB) pulse generation and transmission have been described. In this design a pulse with pulse-width approximately 150ps and amplitude 500mV (peak-to- peak) was generated using a single high electron mobility transistor (HEMT) as the active device (and an optional Schottky diode for enhanced performance), this being the simplest circuit for generating UWB pulses as far as we know. This circuit was integrated with a newly designed UWB planar microstrip-fed slot antenna, which is an active antenna in the sense that in addition to radiating the signal, it also acts as a fllter, which tailors the spectrum of the transmitted pulse to a shape close to that recommended for UWB communications. We have also given a quantitative analysis, which explains the operation of the circuit.

Analysis of the Survivability of GaN Low-Noise Amplifiers

This paper presents a detailed analysis of the stressing mechanisms for highly rugged low-noise GaN monolithic-microwave integrated-circuit amplifiers operated at extremely high input powers. As an example, a low-noise amplifier (LNA) operating in the 3-7-GHz frequency band is used. A noise figure (NF) below 2.3 dB is measured from 3.5 to 7 GHz with NF<1.8 dB between 5-7 GHz. This device survived 33 dBm of available RF input power for 16 h without any change in low-noise performance. The stress mechanisms at high input powers are identified by systematic measurements of an LNA and a single high electron-mobility transistor in the frequency and time domains. It is shown that the gate dc current, which occurs due to self-biasing, is the most critical factor regarding survivability. A series resistance in the gate dc feed can reduce this gate current by feedback, and may be used to improve LNA ruggedness

A monolithic HEMT passive switch with integrated HBT standard logic compatible driver for phased-array applications

We have achieved the first demonstration of a monolithically integrated high electron mobility transistor (HEMT) passive switch with a heterojunction bipolar transistor (HBT) switch-driver circuit that represents key integrated mixed-signal functions. The HEMT-HBT monolithic microwave integrated circuit (MMIC) is fabricated using selective molecular beam epitaxy (MBE). The single HEMT series switch is driven by an HBT circuit that provides both level shifting and wide voltage drive swing to adequately turn the passive HEMT switch device on and off. The MMIC can be made compatible for operation from either standard TTL or CMOS control signals. The series 0.2×200 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> passive HEMT switch achieves 1.6-2.9 dB insertion loss over a 50 MHz to 12 GHz band when the HEMT is turned on. The corresponding return-losses are >10 dB across the band. When the switch is turned off, the isolation ranges from >40 dB at 1 GHz and decreases to 15 dB at 12 GHz. This integrated HEMT switch and HBT switch driver MMIC represents a basic building block that can be applied to programmable phase shifters used in phased-array antenna applications and can result in a dramatic reduction in size and improvement in performance of these systems.