Search results

1

Investigation of Quantum Effects in Carbonaceous Materials Near the Metal-Insulator Transition by Means of THz Photoconductivity

100%

Dorosinets V., Ksenevich V., Seliuta D., Martūnas Z., Valušis G.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 3

875-878

EN

A series of carbonaceous fibers with conductivity tuned to the metal-insulator transition were prepared by heat treatment of chemically modified polymer precursors. Peculiar behaviour of the resistivity versus temperature dependence R(T) at low temperatures suggests quantum corrections to the Drude conductivity due to weak localization and electron-electron interaction dominating in the conductivity. The THz conductivity method is employed to study the modification of the density of states and provides evidence for a strong change in density of states at the Fermi level caused by the quantum effects.

2

Terahertz Resonant Detection by Plasma Waves in Nanometric Transistors

86%

Teppe F., El Fatimy A., Boubanga S., Knap W., Seliuta D., Valusis G., Chenaud B.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 3

815-820

EN

The plasma waves in gated two-dimensional electron gas have a linear dispersion law, similar to the sound waves. The transistor channel is acting as a resonator cavity for the plasma waves, which can reach frequencies in the THz range for a sufficiently short gate length field effect transistors. A variety of possible applications of field effect transistor operating as a THz device were suggested. In particular, it was shown that the nonlinear properties of plasma oscillations can be utilized for THz tunable detectors. During the last few years THz detection related to plasma wave instabilities in nanometer size field effect transistors was demonstrated experimentally. In this work we review our recent experimental results on the resonant plasma wave detection at cryogenic and room temperatures.

3

Hot Electron Effect in Degenerate Semiconductor Tunnel Junction

86%

Ašmontas S., Gradauskas J., Petkun V., Seliuta D., Sužiedėlis A., Urbelis A.

Acta Physica Polonica A

|

2005

|

vol. 107

|

issue 1

198-202

EN

We report on the results of experimental study of free carrier heating in degenerate GaAs tunnel p-n diodes when the carriers are excited by pulsed microwave radiation. Free carrier heating is responsible for the electromotive force in the diode. The magnitude of the electromotive force linearly depends on pulsed microwave power and increases with the decrease in semiconductor lattice temperature. It is almost independent of the pulsed microwave frequency and of p-n junction plane orientation in respect to electric field direction. In the tunnelling regime the dark current in the diode is reduced, however, at high enough forward bias the diffusive current is stimulated due to hot carrier phenomenon.

4

Charge Carrier Transport Properties in Single-Walled Carbon Nanotube Fibers

73%

Ksenevich V., Seliuta D., Martūnas Z., Kašalynas I., Valušis G., Galibert J., Kozlov M., Samuilov V.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 3

1039-1042

EN

Transport properties via temperature dependences of sample resistance R(T) and influence of microwave field of 10 GHz on the conductivity of the single-walled carbon nanotubes fibers are investigated. The R(T) dependences studied within 4.2-300 K can be well approximated by the Mott law for 3D variable range hopping below T=80 K and by typical law for fluctuation-induced tunnelling model within the temperature range 80-300 K. We associate the observed increase in the conductivity with microwave power by increase in hopping probability of the charge carriers between single-walled carbon nanotubes.

5

Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices

73%

Subačius L., Venckevičius R., Kašalynas I., Seliuta D., Valušis G., Schmidt J., Lisauskas A., Roskos H., Alekseev K., Köhler K.

Acta Physica Polonica A

|

2011

|

vol. 119

|

issue 2

167-169

EN

Nanosecond pulsed technique was used to study and discriminate strong electric field induced effects in carrier transport in silicon doped GaAs/Al_{0.3}Ga_{0.7}As superlattices at room temperature. The experiment shows that the superlattice can serve as gain media to employ parametric phenomena for microwave amplification.

6

Terahertz Detection with δ-Doped GaAs/AlAs Multiple Quantum Wells

59%

Seliuta D., Čechavičius B., Kavaliauskas J., Krivaitė G., Grigelionis I., Balakauskas S., Valušis G., Sherliker B., Halsall M., Lachab M., Khanna S., Harrison P., Linfield E.

Acta Physica Polonica A

|

2008

|

vol. 113

|

issue 3

909-912

EN

The authors demonstrate selective detection of terahertz radiation employing berylliumδ-doped GaAs/AlAs multiple quantum wells. The sensitivity up to 1 V/W within 4.2-7.3 THz range at liquid helium temperatures is reached. The Franz-Keldysh oscillations observed in photo- and electroreflectance spectra allowed one to estimate built-in electric fields in the structures studied. It was found that the electric field strength in the cap layer region could vary from 10 kV/cm up to 26 kV/cm, depending on the structure design and temperature.

7

Optical and Terahertz Characterization of Be-Doped GaAs/AlAs Multiple Quantum Wells

59%

Čechavičius B., Kavaliauskas J., Krivaitė G., Seliuta D., Širmulis E., Devenson J., Valušis G., Sherliker B., Halsall M., Steer M., Harrison P.

Acta Physica Polonica A

|

2005

|

vol. 107

|

issue 2

328-332

EN

We report on optical, photoreflectance and surface photovoltage, as well as terahertz photocurrent investigation of Be-doped GaAs/AlAs multiple quantum wells at room and liquid helium temperatures, respectively. From the Franz-Keldysh oscillations observed in photoreflectance spectra we determine built-in electric fields within the structure. Interband transition energies calculated by the transfer matrix method are in qualitative agreement with experimentally determined values for the samples having various, from 2×10^{10} up to 2.5×10^{12} cm^{-2}, Be doping densities. The photocurrent observed in the range of 5.4-7.3 THz we associate with photoionization of Be-acceptor states.

8

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes

59%

Valušis G., Seliuta D., Tamošiūnas V., Širmulis E., Balakauskas S., Gradauskas J., Sužiedėlis A., Ašmontas S., Anbinderis T., Narkūnas A., Papsujeva I., Lisauskas A., Roskos H., Köhler K.

Acta Physica Polonica A

|

2005

|

vol. 107

|

issue 1

184-187

EN

We suggest a novel approach to detect broad band, 0.078-2.52 THz, electromagnetic radiation at room temperature using an asymmetrically-shaped bow-tie diode based on a modulation-doped GaAs/AlGaAs structure. We show that the voltage sensitivity in the range from 0.078 THz up to 0.8 THz has a plateau and its value is within 0.3-0.5 V/W. We consider the bow-tie diode design to increase the sensitivity of the device.

Refine search results

Investigation of Quantum Effects in Carbonaceous Materials Near the Metal-Insulator Transition by Means of THz Photoconductivity

Terahertz Resonant Detection by Plasma Waves in Nanometric Transistors

Hot Electron Effect in Degenerate Semiconductor Tunnel Junction

Charge Carrier Transport Properties in Single-Walled Carbon Nanotube Fibers

Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices

Terahertz Detection with δ-Doped GaAs/AlAs Multiple Quantum Wells

Optical and Terahertz Characterization of Be-Doped GaAs/AlAs Multiple Quantum Wells

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes