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Solid state amplifiers are often fitted with an isolator component on the output to protect them from impedance mismatch. GaN based HFET's could offer the potential to remove the isolator due to their high breakdown voltages and high channel temperature operation. However the absence of an isolator would mean that the transistor would have to be able to withstand any load impedance that could be presented...
Two-dimensional transient analysis of gate-field-plate AlGaN/GaN HEMTs with a backside electrode is performed by considering a deep donor and a deep acceptor in a buffer layer. It is shown that the introduction of gate field plate is effective in reducing buffer-related lag and current collapse when the acceptor density in the buffer layer is high. On the other hand, the introduction of backside electrode...
In this paper, an X-band internally-matched GaN HEMT high efficiency amplifier is presented, which is equipped with second harmonic control circuits to enhance the efficiency of the GaN HEMT. The internal matching circuit was designed so that the 2nd harmonics are tuned to obtain maximum power added efficiency (PAE). PAE of 57% was successfully obtained with 12.5W output power at X-band. This is the...
A 200 Watts GaN high electron mobility transistor (HEMT) has been developed for X-band applications. The device consists of four dies of 0.35 um-gate GaN HEMT of 16 mm gate periphery together with input and output 2-stage impedance transformers assembled into a low thermal resistance package. The developed GaN HEMT provides 204W output power and 12dB small signal gain at 9.3 GHz with power added efficiency...
Wideband amplifiers for the next generation of T/R modules in future active array antennas are realized as monolithically integrated circuits (MMICs) on the basis of novel InAlGaN/GaN high electron mobility transistor (HEMT) structures. All designs are realized in microstrip transmission line technology. The wideband amplifier MMICs operate up to a frequency of 18GHz. A number of measurements have...
This work presents an experimental study of the low-frequency dispersion which impairs the performance of microwave active solid state devices. By exploiting low-frequency large-signal excitations (< 10 MHz), the dynamic behaviour of the drain-source current generator is highlighted as function of the operating bias condition and frequency. In order to assess the capability of the proposed investigation...
High-resistivity Silicon substrates, thanks to their low cost and large wafer diameter, could represent a viable solution for the high power GaN-based transistors realization, even if device thermal management optimization is necessary because of thermal conductivity limitations of Silicon. In this work, a comparison between LG=0.5μm GaN on Silicon HEMT devices fabricated in Coplanar Waveguide (CPW)...
This paper reports on DC and RF performances of an In0.15Al0.85N/AlN/GaN high electron mobility transistor (HEMT) on sapphire substrate with a 75-nm-T-shaped-gate. A maximum DC current density of 1.27 A/mm and a peak extrinsic and intrinsic transconductances of 452 mS/mm and 680 mS/mm respectively are obtained. The device exhibits a current gain cutoff frequency (FT) and a power gain cutoff frequency...
InAlN/AlN/GaN high electron mobility transistors (HEMT) show interesting performances at level of static characteristics as well as at level of the behavior at microwave frequencies. This article presents an analysis of the impact of the variation of the topology of 2×100 μm devices on static I-V measurements and small signal parameters. Variations of the gate-drain distance and of the extension of...
In this paper, an S-band internally harmonic matched GaN FET is presented, which is designed so that up to third harmonic impedance is tuned to high efficiency condition. Harmonic load pull measurements were done for a small transistor cell at first. It was found that power added efficiency (PAE) of 78% together with 6W output power can be obtained by tuning impedances up to 3rd harmonic for both...
The classical Doherty configuration suffers from a lack of accurate control of the load impedance performed by the peaking stage. The result is a reduction in the maximum obtainable efficiency and linearity performance for a given input power level. By driving the carrier and peaking power amplifiers independently, it is possible to present the optimum load to the carrier stage for either maximum...
In this paper, we reported evaluation results of our L/S-band GaN HEMT, especially focusing on ruggedness and reliability. In terms of ruggedness, we demonstrated GaN HEMT had 3-terminal breakdown voltage of 250 V and sufficiently wide area of safe operation (ASO) at 200 degC. Simulated peak drain-source voltage of an inverse class-F operation reached 160 V, and 3-terminal breakdown voltage was good...
An empirical large-signal model for high power AlGaN/GaN metal-insulator-semiconductor HEMT (GaN MISHEMT) utilizing improved drain current (Ids) and gate charge (Qg) formulation is presented. The proposed modeling equations accurately model the asymmetric bell-shaped transconductance (Gm) characteristics and the peaking behaviors of gate capacitance (C11) over a wide bias range of operation. All the...
Manga is a five Nation (Germany, France, Italy, Sweden and United Kingdom) joint project realized by the European Defence Agency (EDA) which focuses on SiC substrates and a GaN epi wafers supply chain. The main objective of the project, started in March 2010, is to sustain the industrial development of semi-insulating silicon carbide substrates (SI SiC) and prove the industrial capability of Europe...
AlN/GaN HEMT technology has made rapid progress over the past decade with problems such as high contact resistance and leakage currents being overcome to a certain degree. This paper presents DC and RF results for a short gate length, in-house fabricated AlN/GaN MOS-HEMT. The results indicate that problems with growth and passivation still exist. An extraction technique for small signal equivalent...
In this work an innovative GaN HEMT technology based on a scalable Gate Length (80nm, 150nm and 250nm) process with complementary integration of a Schottky Field Plate (FP) is presented. The characterization results are compared between different Gate Lengths and FP topologies configurations, fabricated on the same wafer. In particular, remarkable low noise performances (NFmin=0.87dB, GASS=10.5dB...
Key GaN HEMT front-end circuits for next generation AESA radar/EW applications are presented. The circuits are an S-band 20 W MMIC HPA reaching 50 % measured PAE, a two-stage S-band MMIC LNA showing a measured NF of 1.3 dB, and a DC-18 GHz SPDTs showing a measured insertion loss of less than 2 dB at 18 GHz. Furthermore, a 2–18 GHz front-end circuit with a co-integrated two-stage LNA and a T/R-switch...
In this paper the intrinsic transconductance, output current, output power and their nonlinear derivatives are analyzed for double and single channel HEMTs. It is shown that the distortion products weakly depend on device's gate width dimension. Conversely, it is strongly affected by the 2DEG sheets in the quantum wells. The more the number of device's active channels, the higher the current and subsequently...
A HEMT model is proposed that correctly isolates the access metallization from the intrinsic device to give linear scalability. The model uses a distributed network of intrinsic unit cells composed of lumped elements. The topology of these networks is determined such that a scalable set of parameters is obtained. The parameters for the intrinsic and extrinsic parts of the transistor have been extracted...
In this paper we present the design and realization of a high-power amplifier in grounded coplanar transmission line technology using 100 nm AlGaN/GaN dual-gate HEMTs. For the fabricated dual-stage amplifier a continuous wave saturated output power of up to 24.8 dBm (0.84 W/mm) at 63 GHz for 20 V drain bias was measured. A small-signal gain of more than 20 dB was achieved between 56 and 65 GHz.
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