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InAlAs/InGaAs HFETs having very high indium content (80 and 100%) in the channel have been fabricated on GaAs and electrically characterized. The extrinsic transconductance were 310 mS/mm (560 mS/mm at 77 K), and the saturation current were 700 mA/mm (600 mA/mm at 77 K) for an InAs channel. The value of fT and fmax for this device were measured to be 80 GHz and 50 GHz, respectively. The In0.8Ga 0.2...
This paper reports on the use of Pd-Ge-Ag Au for ohmic contacts to InAlAs/InGaAs High Electron Mobility Transistors (HEMTs). After annealing onto a hot plate, specific contact resistance of 1 10-6??cm2 and 5 10-7 ??cm2 for structures having respectively a 5 nm undoped and a 50 nm n+ doped InGaAs cap layer were obtained in a wide temperature range (380??C-470??C). No thermal degradation was observed...
Current transient spectroscopy measurements have been applied to characterize deep levels lying in AlInAs/GaAlInAs/AlInAs heterojunction field effect transistors (HFET). The use of various bias conditions (gate to source voltage as well as drain to source voltage) allows the observation of deep levels lying in the different layers of the HFET. The trap characteristics are compared to the defects observed...
In this paper, the influence of the gate leakage current on the noise performance of MESFETs and MODFETs is investigated. The theoretical results are discussed and it is shown that the noise performance of FETs is strongly dependent on the gate leakage current value, especially at a few GHz.
In this work, we present the results of structural optimization of ??-doped pseudomorphic HEMTs. This study was performed using a 2D hydrodynamic energy model of high performance. The results indicate a limite for gate length reduction as well as rear plan doping. Also, we were able to show that an upper limit for the gate-edge of recess separation is to be respected.
Using two-and three dimensional analytical and numerical models, scaling limits derived from small-geometry degradation of subthreshold characteristics are compared for six different FET structures in bulk Si, SOI and GaAs technologies. For Si devices, the low impurity channel MOSFET can be scaled down to Lmin= 0.045??m and the dual gate SOI MOSFET to Lmin= 0.028??m. The GaAs MESFET can be scaled...
The analysis of high frequency parameters of pseudomorphic HEMTs (PM-HEMT) at cryogenic temperatures and different gate lengths 0.1??m to 0.7??m, compared to existing modeling data, points out the improvement of average carrier velocity transport at low temperatures, the larger relative importance of certain parasitic effects (lateral diffusion under the gate, fringe effects, electrostatic capacitances)...
Two types of HEMT transistors with 0.2 μm gatelength have been fabricated: pseudomorphic (PM) on GaAs and lattice matched (LM) on InP. An extensive study of the DC and HF-characteristics shows the higher potential of the InP-based devices: extrinsic fT-values up to 141 GHz were obtained. The monolithic integration of the InP LM HEMT's is illustrated by the performance of a coplanar distributed amplifier.
We present a comparative study, at 300 K and at low longitudinal field, of the DC characteristics and the low-frequency noise in the drain current of GaAs/AlGaAs MODFETs which, ideally, differ only by the doping mode of the AlGaAs layer. The higher l/f-like noise in the δ-doped structure is consistent with our previous suggestion that charge fluctuations under the gate contribute significantly to...
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