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1

Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

100%

Binder J., Korona K., Borysiuk J., Wysmołek A., Baeumler M., Köhler K., Kirste L.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

918-920

EN

In this work we present measurements of GaInN/GaN light emitting diodes (LEDs) with an active layer consisting of three quantum wells made of Ga_{0.9}In_{0.10}N that have different widths (1.8 nm, 2.7 nm, 3.7 nm). A comparison of emission and absorption (photocurrent) on the same sample revealed a shift in energy, with the emission energy being significantly lower. The shifts are about 0.02 eV, 0.03 eV, and 0.04 eV for the quantum wells having the widths of 1.8 nm, 2.7 nm, and 3.7 nm, respectively. This can be explained by a shift of the ground state energy caused by the quantum confined Stark effect. Calculations show that due to the spontaneous polarization and the piezoelectric effect a strong electric field of the order of 1 MV/cm was present in the GaInN quantum wells. Simulations of ground-state energies in the model of an infinite square well under the influence of an electric field with a matched effective well width were performed and used to interpret the experimental results.

2

Dynamics of the Electric Field in a GaAs/AlGaAs Superlattice after Femtosecond Optical Excitation: Application of Time-Resolved Spectroscopic Techniques

100%

Lisauskas A., Blöser C., Sachs R., Roskos H., Juozapavičius A., Valušis G., Köhler K.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

250-255

EN

We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/AlGaAs superlattice after pulsed optical excitation at low temperature. The electric field dynamics is investigated by tracing the spectral position of the Wannier-Stark transitions as a function of delay time. We determine the electron sweep-out time, extract detailed information about the picosecond-time-scale drift of the charge carriers by comparing the measured data with the results of semi-classical self-consistent model calculations, and evaluate the two experimental techniques with respect to their ability to provide information about the carrier and field dynamics.

3

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

84%

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

Acta Physica Polonica A

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2011

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vol. 119

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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.

4

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

68%

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

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2005

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vol. 107

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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.

5

Terahertz Detection by the Entire Channel of High Electron Mobility Transistors

68%

Sakowicz M., Łusakowski J., Karpierz K., Knap W., Grynberg M., Köhler K., Valusis G., Gołaszewska K., Kamińska E., Piotrowska A., Caban P., Strupiński W.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1343-1348

EN

GaAs/AlGaAs and GaN/AlGaN high electron mobility transistors were used as detectors of THz electromagnetic radiation at liquid helium temperatures. Application of high magnetic fields led to the Shubnikov-de Haas oscillations of the detection signal. Measurements carried out with a simultaneous modulation of the intensity of the incident THz beam and the transistor gate voltage showed that the detection signal is determined by the electron plasma both in the gated and ungated parts of the transistor channel. This result is of importance for understanding the physical mechanism of the detection in high electron mobility transistors and for development of a proper theoretical description of this process.

Refine search results

Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

Dynamics of the Electric Field in a GaAs/AlGaAs Superlattice after Femtosecond Optical Excitation: Application of Time-Resolved Spectroscopic Techniques

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

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

Terahertz Detection by the Entire Channel of High Electron Mobility Transistors