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The authors report record DC characteristics and RF performance of a power double heterostructure (DH) pseudomorphic (PM) InGaAs quantum well HFET. The device, with a 0.3*70 mu m/sup 2/ gate, exhibits an intrinsic transconductance as high as 720 mS/mm, a maximum current density of approximately 1 A/mm and delivers a state-of-the-art output power density of 1 W/mm with 5.7 dB linear gain and 38% power added efficiency at 33 GHz. A detailed analysis of the technological aspects and electrical characteristics of the device is proposed to explain these excellent performances. >

A metal-semiconductor-metal detector with a InGaAs/GaAs superlattice active layer showing efficient photoresponse up to 1.35 mu m is discussed. The active layer with an In composition of approximately 64% is grown by molecular beam epitaxy on a GaAs substrate at 460 degrees C. The large size detector (200*200 mu m/sup 2/) shows bias-dependent DC gain, fast response speed (FWHM >

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.

We present two new and original HEMT structures. They have been designed and realized for gate mixer applications. The first HEMT has a decoupling capacitor between the drain and the source. The integrated capacitor acts as a low-pass filter. The second HEMT presents a very nonlinear transconductance profile. The IF signal is provided by the mixing of the RF signal and the second harmonic of the LO signal. Thus, the required LO frequency is divided by 2.

While the majority of research with terahertz radiation from large-aperture antennas used high-intensity femtosecond laser pulses with low repetition rates, we used a regenerative amplifier with a repetition rate up to 300 kHz. This high repetition rate allows us to combine a high-power large-aperture transmitter and dipole antenna detection. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 23–27, 1998.

The nonselective wet chemical etching of AlGaInP and GaAs in pure iodic (HIO3) acid and in hydrochloric acid (HCl) associated different oxidant agents has been evaluated. The pure iodic acid is nonselective between III–V phosphides and arsenides. Unfortunately, the etch of GaAs results in a very rough morphology and an etch rate 10 times greater than on AlGaInP. The mixing of HCl with different oxidants such as H2O2 gives a nonselective etchant. However H2O2 dissociates HC1 to form chlorine which produces a wide evolution of the etch rate with time incompatible with the reproducibility necessary for device technology. This phenomenon is easily explained and solved using oxidant agents such as KIO3, K2Cr2O7. Added to HCl, they give chemically stable solutions but unfortunately they give rise to a strong undercut of the AlGaInP under the GaAs. The iodic acid is also a strong oxidant. Therefore a diluted solution of (HCl, HIO3, H2O) is proposed which gives an evolution of the etch rate between 300 and 3000 A...

This paper presents the evolution with structural parameters of the linearity of the transconductance of multichannel HEMTs measured under low and microwave frequencies. Compared to theoretical calculations, the measured transconductance is in good agreement excepted at high doping levels. These discrepancies are attributed to parasitic effects. The discussion of the different possibilities brings us to conclude that the gate leakage current is most probably involved in the observed phenomena.

Low-temperature (LT) GaAs FETs have been realized for high I × V products. They have been extensively characterized under dc, rf, pulsed, and large-signal conditions. The results are analyzed and related to the device structure. The electrical passivant role of the LT GaAs has been demonstrated. Under dc conditions I × V products of 2.5 W/mm are obtained. Under microwave frequencies, only 0.4 W/mm were measured on this device. We discuss the relationship between the dielectric relaxation of LT GaAs and the low-power performance of the device. New device structures are proposed. © 1996 John Wiley & Sons, Inc.

The study of a multichannel HEMT mixer Is presented. We discuss the specific advantages offered by multi-channel AlGaAs/GaAs HEMT for millimeter wave mixer realization. In particular, tailoring of adequate transconductance profile is used to optimize mixer performances. We study also the effect of HEMT non linearities (gate to source capacitance and drain current) on mixer characteristics conversion gain and third order Intermodulation point.

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In this paper the study of the effects of illumination on the drain current of GaN MESFETs are presented with the aim of discriminating effects due to traps on the device sUiface from those related with epitaxial material substrate and its inteifaces. Illumination together with on-state stress are also used to investigate hot carrier degradation phenomena which consist in drain access resistance increase and consequently in drain CUfTent decrease: this can be attributed to the generation of deep levels andlor to increased trapped chilrge after hot-carrlertest on the device suiface access regions between the gate and the drain contacts. The degradation level is remarkably higher in un passivated devices with respect to . passivated ones. Hot carrier degradation can be recovered by thermal or R. T. storage without bias.

We report a comparison between Ti/Al and Ti/Al/Ni/Au ohmic contacts in terms of contact resistivity, thermal stability, depth profile, and surface morphology. The metals were deposited by conventional electron-beam evaporation, and then annealed at 900°C for 30 s in a N2 atmosphere. The lowest value for the specific contact resistivity was obtained using Ti/Al/Ni/Au metallization. Ti/Al/Ni/Au contacts showed no increase in contact resistivity after aging for five days at 600°C in an air atmosphere. Examination of the surface morphology using atomic force microscopy revealed that the surface roughness was clearly better in the case of Ti/Al/Ni/Au contacts. X-ray photoelectron spectroscopy was also employed and gave primary results of Ti/Al/Ni/Au contact formation.

Over the last years, there is an increasing need to know and characterize the non linear behaviour of most high frequency semiconductor devices. For that, a new and original automatic active load-pull system based on a large signal network analyzer is presented which allows to carry out an accurate non linear characterization with very high load reflection coefficient (more than 0.96) under microwaves probes. After describing the setup and the calibration procedure, a dedicated study has been performed in order to validate the active load-pull system and to know and evaluate the good accuracy of non linear measurements. At non linear model of AlGaN/GaN HEMT device has been established in order to compare measurements and simulations.