Search

International audience; The aim of this article is to detect electron traps in AlInN/GaN transistors operating at room temperature by combining pulsed electrical measurement with photoionization techniques to rapidly assess their activation energies and time constants. In addition, this technique can also reveal the presence of electron traps that cannot be observed by using pulsed measurements alone. Thus, two electron traps were identified including a deep level whose origin could be related to dislocations in the GaN buffer existing in the devices. At the same time, this study has shown that the time constants of these electron traps are inferior to 400 ns and that the electrical behavior of the components is also degraded by the presence of surface states with a time constant of 4 μ s. Moreover, these two traps are at the origin of the gate lag effects observed during the pulsed electrical characterization of the AlInN/GaN high electron mobility transistors (HEMTs). Likewise, a negative output conductance induced by a trapping effect has been put forward.

International audience; This paper presents an innovative impedance tuner architecture aiming at on-wafer characterization. The proposed impedance tuner is composed of an integrated attenuator, which can be tuned in an analog manner, and a transmission line. Thanks to the use of an external short-circuited probe, the effective length of the transmission line can be modified, leading to a phase shift of the reflection coefficient while the attenuator controls its magnitude. Measurement-based results are presented to prove the precision obtained using the external short-circuited probe, while simulation-based results show the performance of the overall system. The system allows complete coverage of the 140-220 GHz band with 2. 5-4.2dB maximum reflection coefficients and minimum reflection coefficients greater than 20 dB, which can be continuously tuned. On the other hand, thanks to the short-circuited probe, virtually, continuous tuning of the phase is also achievable.

International audience; In this paper, an assessment up to 220 GHz of industrial organic laminate substrate technology to integrate millimeter-wave (mmW) waveguide to suspended stripline (SSL) transition is proposed. A WR5 waveguide transition has been manufactured and insertion loss (IL) of 1.4 dB @ 140 GHz and 4.2 dB @ 220 GHz has been achieved, competing with standard approach using a quartz substrate solution with III-V technology. This promising performance paves the way of cost effective mmW and sub-THz module manufacturing leveraging high volume manufacturing packaging processes developed for Si based technologies.

Session EuMIC01 - Large Signal and Non-linear Charaterization Techniques; International audience; In this paper, we report high power performances at 185 GHz on single ended heterojunction bipolar transistors in the BiCMOS055 technology. Three device sizes were designed and characterized up to their saturation region. This was possible thanks to a power setup which offers an available input power up to 13.9 dBm at 185 GHz. An innovative integrated tuner was also designed with each transistor to vary the load at the on-wafer output DUT plane. The output power, power gain and power added efficiency are finally extracted under different load conditions. An output power of 11.3 dBm ± 0.5 dB is reached for the larger effective emitter area that is 1.112μm 2 .

This article is an expanded version from the 2020 International Workshop on Integrated Nonlinear Microwave and Millimeter-Wave Circuits, Cardiff, 16-17 July 2020.; International audience; This article aims to discuss challenges and performances of a passive load-pull test bench dedicated to the G-band frequencies. The first task of this work is the development of the setup to perform high power generation, impedance generation, and high-power dynamic of measurement. The solution proposed is the association of an external power system of source and detectors, with an integrated synthesizer of impedance. The proposed system requires several analysis steps in order to be validated. On the other hand, special care is dedicated to the calibration of the scalar measurement in the millimeter-wave frequency range. Then, due to the unknown phase at the input and output of the device under test (DUT), scalar measurement can lead to high inaccuracy. Hence, an adaptive calibration is proposed and applied to the measurement of a bipolar transistor at 185 GHz. We highlight the effect of the missing phase information on the accuracy of measurement. Results of the measurement are discussed.

International audience; This paper aims to compare the performance of HBT-based and MOSFET-based mm-Wave SPDT switches in a single BiCMOS technology. To the best of authors' knowledge, a direct comparison of this function in the same integrated process has never been reported before. Measurement results on two 50-GHz integrated SPDTs reveal that the HBT-based SPDT switch yields 1.7 dB of insertion loss and 14 dB of isolation in its central frequency, with a bandwidth covering the 30-80 GHz frequency range when considering a return loss greater than 10 dB. On the other hand, the MOSFET-based SPDT switch yields 2.1 dB of insertion loss and 12 dB of isolation at center frequency and a bandwidth covering the 33-80 GHz frequency range.

Thermal effect on intermodulation distortion (IMD) behavior of GaN based high-electron mobility transistor (HEMT) have been researched over input power and frequency using a two-tone technique. A significant modification was observed in terms of magnitude on the linear component and the magnitude as well as the position and appearance of the nulls/notches of the nonlinear components was changed conspicuously. The parasitic resistances and as well as the output current were affected when applied input power increases. As a result, an increase in the output IMDs found and the device threshold voltage VT moves towards more negative of Vgs trace which in turn shifts the notch points of the nonlinear IMDs towards lower values of applied bias Vgs. The values of the output IMDs degrades with the increment of temperature and frequency. The output IMD products also reduced following the transconductances response to temperature. On the other hand, the notch/null's position of the nonlinear IMDs also moves following the thermal response of threshold voltage. This authentic and exhaustive study is crucial to figure out the minimum distortion, maximum gain bias option for active devices.

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al/sub 0.66/In/sub 0.34/As/Ga/sub 0.67/In/sub 0.33/As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 /spl mu/m /spl times/3 mm devices exhibited 30 mW/mm at 850 MHz.

In this letter, successful operation at 10 GHz of T-gate HEMTs on epitaxial structures grown by metal-organic chemical vapor deposition (MOCVD) or MBE on composite substrates is demonstrated. The used device fabrication process is very similar to the process used on monocrystalline SiC substrate. High power density was measured on both epimaterials at 10 GHz. The best value is an output power density of 5.06 W/mm associated to a power-added efficiency (PAE) of 34.7% and a linear gain of 11.8 dB at VDS = 30 V for the components based on MOCVD-grown material. The output power density is 3.58 W/mm with a maximum PAE of 25% and a linear gain around 15 dB at VDS = 40 V for the MBE-grown material.

AlGaN-GaN high electron mobility transistors (HEMTs) on silicon substrate are fabricated. The device with a gate length of 0.3-/spl mu/m and a total gate periphery of 300 /spl mu/m, exhibits a maximum drain current density of 925 mA/mm at V/sub GS/=0 V and V/sub DS/=5 V with an extrinsic transconductance (g/sub m/) of about 250 mS/mm. At 10 GHz, an output power density of 1.9 W/mm associated to a power-added efficiency of 18% and a linear gain of 16 dB are achieved at a drain bias of 30 V. To our knowledge, these power results represent the highest output power density ever reported at this frequency on GaN HEMT grown on silicon substrates.

A measurement system allowing one to put in evidence the trap effects on the power performance of Al/sub 0.1/Ga/sub 0.9/N/GaN high electron mobility transistors (HEMTs) made on sapphire substrate is presented in this paper. This setup permits simultaneous measurements of the output power supplied by the device under test (DUT) and the I/sub D/(V/sub DS/) characteristic in large signal regime at 4 GHz for different load impedances. It shows the traps influence on the maximum drain-current at 4 GHz for different load impedances under large signal operating conditions. The measurements carried out on a device (2/spl times/50/spl times/1 /spl mu/m/sup 2/) have shown a linear decrease of the maximum drain-current when the load impedance increases. These observations make it possible to determine the origin of the power performances difference obtained at microwave frequencies opposite to the static regime.

Design considerations and performance of n(++) GaN/InAlN/AlN/GaN normally off high-electron mobility transistors (HEMTs) are analyzed. Selective and damage-free dry etching of the gate recess through the GaN cap down to a 1-nm-thick InAlN barrier secures positive threshold voltage, while the thickness and the doping of the GaN cap influence the HEMT direct current and microwave performance. The cap doping density was suggested to be 2 x 10(20) cm(-3). To screen the channel from the surface traps, the needed cap thickness was estimated to be only 6 nm. Design is proved by an experiment showing a constant value of the HEMT dynamical access resistance, while a single-pulse experiment indicated almost collapse-free performance. On the other hand, it is found that the n(++) GaN cap does not contribute to the HEMT drain current conduction, nor does it provide a path for the OFF-state breakdown. HEMTs with a gate length of 0.25 mu m and a 4-mu m source-to-drain distance show a drain-to-source current of 0.8 A/mm, a transconductance of 440 mS/mm, a threshold voltage of similar to 0.4 V, and a cutoff frequency of 50 GHz. A thin and highly doped GaN cap is also found to be suitable for the processing of normally on HEMTs by adopting the nonrecessed gate separated from the cap by insulation.

Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the THz range for nanometer size devices. Nonlinear properties of the electron plasma in the transistor channel can lead to the detection and emission of THz radiation. The excitation of plasma waves by sub-THz and THz radiation was experimentally demonstrated at cryogenic as well as at room temperatures. We present an overview of experimental results on THz detection by FETs discussing possibilities of improvement of their performance and application for THz room temperature imaging. We present also recent results on THz emission from GaN/AlGaN-based FETs.

We investigated a 2 nm thin InAlN/AlN barrier after recessing of a GaN cap on top of it and Ir gate metallization. Detailed analysis of the recess process revealed practically no damage until the formation of an etch‐resistant barrier layer producing nitrogen vacancies and hence defect assisted tunneling through the thin barrier. Annealing of the Ir‐based gate stack showed a reduction of the electrical distance between the gate and the channel. The effect was linked to an oxygen‐containing interface layer between the Ir metal and the InAlN layer where oxygen diffused into Ir at elevated temperatures. Resulting devices showed state‐of‐the‐art normally‐off performance.

GaN/AlN/AlGaN/GaN nanowire metal-insulator-semiconductor field-effect transistors (MISFETs) have been fabricated for the first time with submicrometer gate lengths. Their microwave performances were investigated. An intrinsic current-gain cutoff frequency (F T) of 5 GHz as well as an intrinsic maximum available gain (F MAX) cutoff frequency of 12 GHz have been obtained for the first time and associated with a gate length of 0.5 mum. These results show the great potentiality of GaN-based nanowire FETs for microwave applications.

International audience; In this work, we report on room temperature terahertz radiation from sub-micron size GaN/AlGaN based high electron mobility transistors (HEMTs). They could successfully replace the standard Fourier Transform spectrometer source and were investigated with a standard Si-bolometer as a detector. The relatively broad (~1THz) emission line was observed. The maxima were found to be tunable by the gate voltage between 0.75 and 2.1 THz. The observed emission was interpreted as due to the current driven plasma waves instability in the two-dimensional electron gas. The emitted power from a single device reached 150 nW, showing possible application of these transistors as compact sources for terahertz spectroscopy and imaging.

In this work we present experimental results on room temperature terahertz (THz) detection/emission from nanotransistors as well as double grating gates structures. It shows that the emission spectra from GaN/AlGaN HEMT transistor can be successfully interpreted in the frame of the Dyakonov-Shur model which predicts that by heating/accelerating the electrons up to velocities comparable with plasma wave velocity can lead to instability and generation of plasma waves in the transistor channel. Studies of the current dependence of THz detection by InGaAs based HEMT is also presented. It is shown that in realistic transistor structures the room temperature resonant THz detection can be observed only upon applying a current high enough to produce fast/hot electrons. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study we have investigated heterojunctions on sapphire with barrier thicknesses between 13 nm and 5 nm maintaining a high output current. The results indicate that InAlN/GaN HEMT device structures can be reliably designed and fabricated with barrier layer thicknesses approaching the tunnelling thickness and approaching enhancement mode characteristics. Using Al2O3 as high-k gate dielectric also high aspect ratio MOSHEMTs could be designed with comparable characteristics to MESHEMTs of the same barrier thickness. This is an ongoing study and results on further barrier downscaling experiments will be presented.

We measured the DC and RF impedance characteristics of micrometric metal-oxide-semiconductor (MOS) capacitors and Schottky diodes using scanning microwave microscopy (SMM). The SMM consisting of an atomic force microscopy (AFM) interfaced with a vector network analyser (VNA) was used to measure the reflection S11 coefficient of the metallic MOS and Schottky contact pads at 18 GHz as a function of the tip bias voltage. By controlling the SMM biasing conditions, the AFM tip was used to bias the Schottky contacts between reverse and forward mode. In reverse bias direction, the Schottky contacts showed mostly a change in the imaginary part of the admittance while in forward bias direction the change was mostly in the real part of the admittance. Reference MOS capacitors which are next to the Schottky diodes on the same sample were used to calibrate the SMM S11 data and convert it into capacitance values. Calibrated capacitance between 1–10 fF and 1/C2 spectroscopy curves were acquired on the different Schottky diodes as a function of the DC bias voltage following a linear behavior. Additionally, measurements were done directly with the AFM-tip in contact with the silicon substrate forming a nanoscale Schottky contact. Similar capacitance-voltage curves were obtained but with smaller values (30–300 aF) due to the corresponding smaller AFM-tip diameter. Calibrated capacitance images of both the MOS and Schottky contacts were acquired with nanoscale resolution at different tip-bias voltages.

In this paper, we present static measurements and defect analysis performed on AlGaN/GaN/Si or Al/sub 2/O/sub 3/ HEMTs. I/sub d/-V/sub ds/-T, I/sub d/-V/sub gs/-T and I/sub g/-V/sub gs/-T characteristics show anomalies (leakage current, degradation in saturation current, Kink effect, distortions on I/sub d/-V/sub d/ characteristics in saturation region,... etc). These anomalies on output characteristics changes when we vary measurement conditions (temperature, polarisation, stress...). Deep defects analysis performed by capacitance transient spectroscopy (C-DLTS), frequency dispersion of the output conductance (G/sub ds/(f)) and random telegraph signal (RTS) prove the presence of deep defects with activations energies ranging from 0.05 eV to 1.8 eV. The presence of G-R centers acting like traps at the interface GaN/AlGaN is confirmed by I/sub g/-V/sub gs/ and RTS measurements. The localization and the identification of these defects are presented. Finally, the correlation between the anomalies observed on output characteristics and defects is discussed and a little comparison between Al/sub 2/O/sub 3/ and Si HEMTs is presented.

The authors report on the effects of plasma pre-treatment before SiN x passivation on the electrical traps of undoped AlGaN/GaN HFETs. Different plasmas were tested with O 2 or CF 4 or (O 2 + CF 4 ) gas. The maximum drain current decreased when an O 2 plasma was used before SiN x passivation, and increased up to 35% in the other cases. The best results were obtained using an (O 2 + CF 4 ) plasma. In that case, an important decrease of the knee voltage was observed in the I ds ( V ds , V gs ) characteristic which becomes independent of the bias variation. The influence of the lighting on the electrical characteristics of AlGaN/GaN HFETs was also studied. We have deduced that a part of the electrical traps is located at the surface of the structure and that another part is present under the gate, in the volume of the AlGaN layer, and/or at the interface AlGaN/GaN.

International audience; The electrical effects of SiNx deposition on GaN MESFETs have been investigated. Significant effects induced from the dielectric coating have been observed depending on the temperature deposition used in the technological process. A power density increase of 30% has been observed after the device passivation performed at 200°C.

We study the behavior of low temperature (LT) GaAs FETs at 300 and 77 K. The dependence with frequency of their transconductance is measured and a decrease is observed in the MHz range at room temperature and in the kHz range at liquid nitrogen temperature. This phenomenon is related to the dielectric relaxation of the LT GaAs which is due to the residual conductivity of this material. The behavior of the transconductance is also correlated to the large signal characterization. From the results, we propose improvements of the device structure by recessing the gate into the LT GaAs. The transconductance measurements show a strong improvement in the device characteristics.

International audience; Room-temperature generation of terahertz radiation in nanometer gate length InAlAs/InGaAs and AlGaN/GaN high-mobility transistors is reported. A well-defined source-drain voltage threshold for the emission exists, which depends on the gate bias. Spectral analysis of the emitted radiation is presented. The highest emission power emitted from a single device reached 0.1 µW.

International audience; A new empirical nonlinear model of GaN-based electron devices is presented in the article. The model takes into account low-frequency dispersion due to self-heating and charge-trapping phenomena and provides accurate predictions at frequencies where nonquasi-static effects are important. The model is based on the application of a recently proposed equivalent-voltage approach and is identified by using pulsed measurements of drain current characteristics and pulsed S-parameter sets. Full experimental validation on a GaN on SiC PHEMT is provided at both small- and large-signal operating conditions