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1

Transport Phenomena in Two-Dimensional Structures with Quantum Dots

100%

Požela J.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

118-127

EN

A model that explains the unusual characteristics of the AlGaAs/GaAs modulation-doped field-effect transistor (MODFET) with InAs quantum dots incorporated in the GaAs channel is presented. It is shown that the negative charge of electrons confined in quantum dots decreases the threshold gate-drain voltage at which the channel is fully depleted. This provides an impact ionization of quantum dots at a low drain voltage. Because of the quantum dot ionization, the quantum dot MODFET transconductance becomes large and negative. The increased transconductance, due to the additional doping of the GaAs and InAs channels by impurities, exceeds 10^3 mS/mm. It is shown that the insertion of InAs quantum well with quantum dots into the GaAs quantum well increases the electron maximum drift velocity up to 10^8 cm/s, and consequently, quantum dot MODFET current gain cut-off frequency up to few hundred gigahertz.

2

Microplasma Noise Stimulated by Microwave Electric Field

45%

Namajūnas A., Tamaševičius A., Mykolaitis G., Bumelienė S., Požela J.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

369-372

EN

Si and GaAs avalanche diodes containing microplasmas are investigated. Microwave field applied to the diode in addition to reverse dc bias results in considerable spread of noise spectrum and in the increase of noise power. The microplasma noise spectra cover very high (30 to 300 MHz) and ultrahigh (300 to 1000 MHz) frequency bands, while the effective noise temperature is about 10^8 K.

3

Enhanced Electron Saturated Drift Velocity in AlGaAs/GaAs/AlGaAs Heterostructures

45%

Požela J., Požela K., Sužiedėlis A., Jucienė V., Petkun V.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

989-992

EN

A new approach for reduction of scattering rate of electrons by polar optical phonons in the double barrier heterojunction quantum well is proposed. This approach is based on the phonon localization in narrow phonon wells. The enhancement of the electron saturated drift velocity in the Al_{0.2}Ga_{0.8}As/GaAs/Al_{0.2}Ga_{0.8}As high electron mobility transistor channel is envisaged theoretically and observed experimentally. The drift velocity in the channel in high electric fields (E >10 kV/cm) exceeded the maximal drift velocity in bulk GaAs (v_{max}=10^7 cm/s) and achieved the value of 4×10^7 cm/s.

4

Mesoscopic Structures for Microwave-THz Detection

33%

Sužied.elis A., Ašmontas S., Požela J., Kundrotas J., Širmulis E., Gradauskas J., Kozič A., Kazlauskaité V., Anbinderis T.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

803-809

EN

Properties of microwave detectors of various design on the base of MBE grown GaAs and AlGaAs structures are discussed in this paper: simple asymmetrically shaped structures with heavily doped GaAs and AlGaAs layers of nanometric thickness as well as diodes with two-dimensional electron gas layers. Novel models of the detectors with partially gated two-dimensional electron gas layer as well as with small area GaAs/AlGaAs heterojuction are discussed to demonstrate different ways to increase the voltage sensitivity of the detectors of electromagnetic radiation in GHz-THz frequency range.

5

Electron Transport in Modulation-Doped InAlAs/InGaAs/InAlAs Heterostructures in High Electric Fields

27%

Požela K., Požela J., Jucienė V., Vasil'evskii I., Galiev G., Klimov E., Sužiedėlis A., Žurauskienė N., Stankevič V., Keršulis S., Paškevič Č.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

170-172

EN

The following peculiarities of electron transport in In_{0.53}Ga_{0.47}As/In_{0.52}Al_{0.48}As quantum wells with δ-Si-doped In_{0.52}Al_{0.48}As barriers at high electric fields are discovered: (1) an enhancement of electron mobility by inserting the InAs phonon wall into the In_{0.53}Ga_{0.47}As/In_{0.52}Al_{0.48}As quantum well, as well as increasing the InAs content in the modulation-doped In_{0.8}Ga_{0.2}As/In_{0.7}Al_{0.3}As heterostructure; (2) a large decrease in electron mobility and a change of electron density with increasing electric field in the range of 1-4 kV/cm; (3) a magnetic field dependence of the threshold electric field for intervalley scattering of electrons; and (4) microwave current oscillations in high electric fields.

6

Influence of Magnetic Field on Detection Properties of Planar Microwave Diodes

27%

Sužiedėlis A., Ašmontas S., Požela J., Gradauskas J., Nargelienė V., Paškevič Č., Derkach V., Golovashchenko R., Goroshko E., Korzh V., Anbinderis T.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

218-221

EN

The results of experimental investigation of detection properties of the planar microwave diodes of various configuration on DC magnetic field are presented in this paper. The detection of microwave radiation was measured at 51 GHz, 72 GHz and 144 GHz frequencies. The magnetic field was applied in plane and perpendicularly to the plane of the diodes. The experiment was performed at room temperature. Dependence of the detected voltage of the diodes on the magnetic field had asymmetric character with respect to the polarity of the magnetic field. This fact allowed us to suspect the magnetic rectification influencing the detected voltage. Therefore, average value of the detected voltage with respect to the polarity of the applied magnetic field gives its dependence on the applied magnetic field.

Refine search results

Transport Phenomena in Two-Dimensional Structures with Quantum Dots

Microplasma Noise Stimulated by Microwave Electric Field

Enhanced Electron Saturated Drift Velocity in AlGaAs/GaAs/AlGaAs Heterostructures

Mesoscopic Structures for Microwave-THz Detection

Electron Transport in Modulation-Doped InAlAs/InGaAs/InAlAs Heterostructures in High Electric Fields

Influence of Magnetic Field on Detection Properties of Planar Microwave Diodes