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Enhancement and Narrowing of Excitonic Lines in AlInN/GaN Heterostructures

100%
Kundrotas J., Čerškus A., Liberis J., Matulionis A., Leach J., Morkoç A.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
173-176
EN
A study of the photoluminescence properties of AlInN/GaN in comparison with the spectrum of the GaN active layer of the same heterostructure is presented. The strong intensity lines of the observed photoluminescence spectra are associated with the formation, enhancement and narrowing of the excitonic lines in the flat band region of the active GaN layer. The phenomena in the presence of electric field near the heterostructure interface with the two-dimensional electron system are associated with nonlinear behaviour of recombination processes.
2
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Peculiarities of Excitonic Photoluminescence in Si δ-Doped GaAs Structures

100%
Nargelienė V., Ašmontas S., Čerškus A., Gradauskas J., Kundrotas J., Sužiedėlis A.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
177-179
EN
We present investigation of photoluminescence properties of Si δ-doped GaAs structures at different temperatures and various laser excitation intensities. Strong excitonic emission was observed in the δ-doped structures. The photoluminescence in the infrared region, below excitonic emission, originates from a non-phonon free electron-acceptor e-A transitions and longitudinal optical phonon sidebands of e-A transitions. Possible mechanisms for recombination of photocarriers are discussed, with a particular focus on an enhanced excitonic photoluminescence emission in comparison with that from intrinsic GaAs layers of the same structures.
3
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Radiative Recombination Spectra of Heavily p-Type δ-Doped GaAs/AlAs MQWs

100%
Kundrotas J., Čerškus A., Valušis G., Lachab M., Khanna S., Harrison P., Linfield E.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
963-966
EN
We present a study of the photoluminescence properties of heavily Be δ-doped GaAs/AlAs multiple quantum wells measured at room and liquid nitrogen temperatures. Possible mechanisms for photocarriers recombination are discussed, with a particular focus on the peculiarities of the excitonic and free carriers-acceptors photoluminescence emissions occurring below and above the Mott metal-insulator transition. Moreover, based on a simple theoretical model, it is found that the critical impurities concentration to observe the Mott transition in the multiple quantum wells samples exhibiting 15 nm wells width and 5 nm thick barrier layers is ≈3×10^{12} cm^{-2}.
4
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Enhancement of the Excitonic Photoluminescence in n^{+}/i-GaAs by Controlling the Thickness and Impurity Concentration of the n^{+} Layer

84%
Čerškus A., Nargelienė V., Kundrotas J., Sužiedėlis A., Ašmontas S., Gradauskas J., Johannessen A., Johannessen E.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
154-157
EN
This communication presents the photoluminescence spectra of molecular beam epitaxially grown GaAs structures made from a 500 nm thick layer of intrinsic conductivity capped with a silicon doped layer with a film thickness ranging from 10 to 100 nm. Two different doping concentrations of the cap layer, N_{Si} = 10^{17} cm^{-3} and N_{Si} = 10^{18} cm^{-3}, was considered. The results showed the excitonic line of i-GaAs layer enhancement. The intensity of excitonic line was about 160 times higher for the homojunction compared to the intrinsic conductivity epitaxial layer at liquid helium temperature. Possible mechanisms of the observed intensity enhancement in the n^{+}/i-GaAs homojunction are discussed.
5
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Mesoscopic Structures for Microwave-THz Detection

84%
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.
6
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Experimental Study of Optical Transitions in Be-Doped GaAs/AlAs Multiple Quantum Wells

84%
Kundrotas J., Čerškus A., Ašmontas S., Valušis G., Sherliker B., Halsall M., Harrison P., Steer M.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
245-249
EN
We present a photoluminescence study of optical transitions in Be acceptor-doped GaAs/AlAs multiple quantum wells at room and liquid nitrogen temperatures. We investigate excitonic spectra and reveal acceptor-impurity induced effects in multiple quantum wells having different width.
7
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High Power Microwave Detection in Asymmetrically Shaped n-Al_xGa_{1-x}As Structures

84%
Ašmontas S., Čerškus A., Gradauskas J., Kundrotas J., Lučun A., Petkun V., Sužiedėlis A., Šilėnas A.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
315-318
EN
Investigations of detection of high power microwaves in planar asymmetrically shaped microwave diodes on the basis of Al_xGa_{1-x}As ternary semiconductors with various AlAs mole fraction are presented. The principle of operation of the microwave diodes is based on carrier heating phenomena in asymmetrically shaped homogeneous semiconductor structure due to different distribution of the electric field strength along the sample. Experimental results of microwave detection on the barrier-less asymmetrically shaped diodes are presented paying special attention to the homogeneity of Al_xGa_{1-x}As which was monitored by photoluminescence technique.
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