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Obliczanie współczynnika absorbcji supersieci InAs/GaSb

Machowska-Podsiadło E., Bugajski M.

Elektronika : konstrukcje, technologie, zastosowania

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2014

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Vol. 55, nr 11

60-62

PL

W pracy przedstawiono wyniki obliczeń dla supersieci (InAs)10 ML / (GaSb)10 ML z asymetrycznymi powierzchniami międzyfazowymi. Symulacje zrealizowano z zastosowaniem zmodyfikowanej 3-pasmowej metody k•p, która uwzględnia mieszanie się stanów ciężkich oraz lekkich dziur na powierzchniach międzyfazowych w strukturze. Wyznaczono strukturę pasmową oraz współczynnik absorpcji supersieci, w temperaturze T=300K. Obliczenia wykonano dla światła padającego na strukturę prostopadle do płaszczyzny warstw supersieci (tj. w kierunku z) i spolaryzowanego w kierunku x (polaryzacja TE). Symulacje zrealizowano dla dwóch dyskretyzacji w przestrzeni wektora falowego kt=(kx, ky), tj. z krokiem Δkx=Δky=0,01π/a oraz Δkx=Δky=0,005π/a, gdzie a jest stałą sieci.

EN

The paper presents results of calculations of band structure of (InAs)10 ML / (GaSb)10 ML superlattice with asymetric interfaces. Simulations have been performed using modified k•p method which takes into account valence band mixing at the interfaces. The absorption coefficient of the superlattice has been determined at T=300K. The calculation has been done for normal incidence and TM polarization of incoming light. Two different discredizations in the wavevector space kt=(kx, ky) have been considered; with Δkx=Δky=0,01π/a step and Δkx=Δky=0,005π/a, where a is lattice constant.

2

Struktura pasmowa i optyczne właściwości supersieci InAs/GaSb

Machowska-Podsiadło E., Jasik A., Pierściński K., Bugajski M.

Elektronika : konstrukcje, technologie, zastosowania

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2010

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Vol. 51, nr 10

30-32

PL

W pracy przedstawiono wyniki obliczeń stanów elektronowych w supersieciach II rodzaju wykonane dla trzech próbek, złożonych z 30 sekwencji warstw o grubości nominalnej 8 ML InAs/8 ML GaSb oraz zmierzone dla nich widma luminescencji (PL). Badane supersieci zostały wykonane metodą epitaksji z wiązki molekularnej na podłożu GaSb. Prezentowane widma PL są zgodne z wynikami przedstawionymi w pracy [1]. Krawędź absorpcji badanych supersieci otrzymano na poziomie 4,26 µm. Wyniki eksperymentu porównano z wynikami obliczeń numerycznych, wykonanych metodą opisaną, w pracy [2]. Stany elektronowe supersieci wyznaczono z uwzględnieniem mieszania się stanów dziur ciężkich (HH) oraz dziur lekkich (LH) na powierzchniach międzyfazowych pomiędzy warstwami supersieci. W obliczeniach uwzględniono zjawisko nieparaboliczności pasm, związane z wąską, przerwą energetyczną arsenku indu. Wyniki przeprowadzonych symulacji korespondują z wynikami otrzymanymi na podstawie eksperymentu.

EN

In the work we present the results of the electron states calculation in the type-II superlattices. Calculations were performed for the three samples with the 30 layer sequence with the nominal thickness 8 ML InAs/8 ML GaSb. We also present the photoluminescence (PL) spectra measured for the investigated structures. The superlattices were grown on GaSb substrate with the use of molecular beam epitaxy. The measured PL spectra are in a good agreement with the results presented in the work [1]. The cutt-off wavelength of the investigated superlattices was obtained on the level of 4,26 µm. The experimental results were compared with the results of the numerical calculations which were performed with the use of the method presented in the work [2]. The electron states in the superlattice were calculated taking into account the effect of heavy hole and light hole mixing at the interfaces between InAs and GaSb layers. In the calculations we considered the effect of the nonparabolicity which is the consequence of the narrow InAs band gap. The results of calculation correspond with the results obtained from the experiment.

3

3D self-consistent solution of Poisson and Schrödinger equations for electrostatically formed quantum dot

Machowska-Podsiadło E., Mączka M., Bugajski M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2007

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Vol. 55, nr 2

245-249

EN

In this work we discuss 3D selfconsistent solution of Poisson and Schrodinger equations for electrostatically formed quantum dot. 3D simulations give detailed insight into the energy spectrum of the device and allow us to find values of respective voltages ensuring given number of electrons in the dot. We performed calculations for fully 3D potential and apart from that calculations for the same potential separated into two independent parts, i.e. re-garding to the plane of 2DEG and to the direction perpendicular to the meant plane. We found that calculations done for the two independent parts of the potential give good information about quantum dat properties and they are much faster compared to fully 3D simulations.

4

Numerical simulation of coupled quantum dots

Machowska-Podsiadło E., Mączka M.

Electron Technology : Internet Journal

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2005/2006

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Vol.37/38, nr 13

1-4

EN

In the work we present self-consistent solutions of Poisson and Schrödinger equations which describe electron states in coupled quantum dots. Results for two neighbouring quantum dots formed in an electrostatic way are discussed. Zero-dimensional electron gas is investigated in the structure proposed by Kastner [1] and presented in our earlier works [2-4]. In the work results of simulations performed in three- and two-dimensional space are shown. We included Hartree potential for modeling Coulomb interactions among electrons in the system. We also considered the exchange and correlation potentials which ensured that each discrete energy level was occupied by only one electron. The exchange and correlation potentials were taken into account with the help of the Local Density Approximation (LDA).

5

Optical gain saturation effects in InAs/GaAs self-assembled quantum dots

Wasiak M., Bugajski M., Machowska-Podsiadło E., Ochalski T., Kątcki J., Sarzała R.P., Maćkowiak P., Czyszanowski T., Nakwaski W., Chen J. X., Oesterle U., Fiore A., Ilegems M.

Optica Applicata

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2002

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Vol. 32, nr 3

291-299

EN

An attempt has been made to understand electronic structure and optical (lasing) properties of self-assembled InAs/GaAs quantum dots (QD) and to describe saturation effects in QD levels population. The new, improved rate equation model has been developed. The impact of carrier relaxation and level depopulation inside quantum dots on lasing properties, in particular on gain depressing, is discusse.