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1

Monte Carlo Analysis of the Dynamic Behavior οf InAlAs/InGaAs Velocity Modulation Transistors: A Geometrical Optimization

100%

Vasallo B., González T., Pardo D., Mateos J.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

193-195

EN

The influence of the geometry on the dynamic behavior of InAlAs/InGaAs velocity modulation transistors is analyzed by means of a Monte Carlo simulator in order to optimize the performance of this new type of transistor. In velocity modulation transistors, based on the topology of a double-gate high electron mobility transistor, the source and drain electrodes are connected by two channels with different mobilities, and electrons are transferred between both of them by changing the gate voltages in differential mode. Consequently, the drain current is modulated while keeping the total carrier density constant, thus in principle avoiding capacitance charging/discharging delays. However, the low values taken by the transconductance, as well as the high capacitance between the two gates in differential-mode operation, lead to a deficient dynamic performance. This behavior can be geometrically optimized by increasing the mobility difference between the two channels, by increasing the channel width and, mainly, by reducing the gate length, with a higher immunity to short channel effects than the traditional architectures.

2

Submillimeter-Wave Oscillations in Recessed InGaAs/InAlAs Heterostructures: Origin and Tunability

100%

Pérez S., Mateos J., González T.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

111-113

EN

By means of an ensemble Monte Carlo simulator, the appeareance of THz oscillations in InAlAs/InGaAs slot diodes is predicted when the applied bias exceeds the threshold for intervalley transfer. Such high frequency is attained by the presence of a Gunn-like effect in the recess-to-drain region of the device channel whose dynamics is controlled by ballistic Γp valley electrons. In this work we explain the mechanism at the origin of this effect and also the influence of the bias conditions, δ-doping, recess-to-drain distance and recess length on the frequency of the ultrafast Gunn-like oscillations. The simulations show that a minimum value for the δ-doping is necessary to have enough carrier concentration under the recess and allow the oscillations to emerge. Finally, we show that shortening the devices (small recess and recess-to-drain lengths) increases the oscillation frequency, so provides an interesting frequency tunability of this THz source.

3

Monte Carlo Analysis of Impact Ionization in Isolated-Gate InAs/AlSb High Electron Mobility Transistors

76%

Vasallo B., Rodilla H., González T., Lefebvre E., Moschetti G., Grahn J., Mateos J.

Acta Physica Polonica A

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2011

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vol. 119

|

issue 2

222-224

EN

We perform a physical analysis of the kink effect in InAs/AlSb high electron mobility transistors by means of a semiclassical 2D ensemble Monte Carlo simulator. Due to the small bandgap of InAs, InAs/AlSb high electron mobility transistors are very susceptible to suffer from impact ionization processes, with the subsequent hole transport through the structure, both implicated in the kink effect. When the drain-to-source voltage V_{DS} is high enough for the onset of impact ionization, holes generated tend to pile up at the gate-drain side of the buffer. This occurs due to the valence-band energy barrier between the buffer and the channel. Because of this accumulation of positive charge, the channel is further opened and the drain current I_{D} increases, leading to the kink effect in the I-V characteristics.

4

Theoretical Investigation of Large-Signal Noise in Nanometric Schottky-Barrier Diodes Operating in External Resonant Circuits

64%

Shiktorov P., Starikov E., Gružinskis V., Varani L., Vaissière J., Reggiani L., Pérez S., González T.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

396-399

EN

We report Monte Carlo simulations of electronic noise in heavily doped nanometric GaAs Schottky-barrier diodes operating in series with a parallel resonant circuit when a high-frequency large-signal voltage is applied to the whole system. Significant modifications of the noise spectrum with respect to the unloaded diode are found to occur in the THz-region.

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Monte Carlo Analysis of the Dynamic Behavior οf InAlAs/InGaAs Velocity Modulation Transistors: A Geometrical Optimization

Submillimeter-Wave Oscillations in Recessed InGaAs/InAlAs Heterostructures: Origin and Tunability

Monte Carlo Analysis of Impact Ionization in Isolated-Gate InAs/AlSb High Electron Mobility Transistors

Theoretical Investigation of Large-Signal Noise in Nanometric Schottky-Barrier Diodes Operating in External Resonant Circuits