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1

Zero Field Spin Splitting in GaN/AlGaN Heterostructures Probed by the Weak Antilocalization

100%

Dybko K., Siekacz M., Skierbiszewski C.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1109-1113

EN

We present the magnetoconductivity measurements of a high mobility two-dimensional electron gas confined at GaN/AlGaN interface. The sensitive measurements of low field conductivity revealed both quantum corrections, the weak localization and antilocalization effects. It indicates the importance of the spin-orbit coupling in this wide band gap material. The analysis of the data provided the information about the temperature dependence of the dephasing time and total spin-orbit relaxation time. The conduction band spin splitting energy amounts to 0.23 meV and 0.35 meV at electron densities 2.2×10¹² cm¯² and 5.7×10¹² cm¯², respectively.

2

Electron-Electron Interaction Effects in Quantum Hall Regime of GaN/AlGaN Heterostructures

76%

Siekacz M., Dybko K., Maude D., Potemski M., Knap W., Skierbiszewski C.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

269-273

EN

We measured the activation of resistivity at quantum Hall minima in high mobility two-dimensional electron gas confined at AlGaN/GaN interface. The effective g-factor and effective mass was deduced. The electron-electron interactions modify both quantities compared to their bare band values. It is found that the influence of interactions is much more pronounced onto g-factor than effective mass. The relative spin susceptibility was also calculated and compared with available theories. The best agreement was found with the ideal two-dimensional gas model in random phase approximation.

3

Waveguide Design for Long Wavelength InGaN Based Laser Diodes

64%

Muzioł G., Turski H., Siekacz M., Sawicka M., Wolny P., Cheze C., Cywiński G., Perlin P., Skierbiszewski C.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1031-1033

EN

One-dimensional optical waveguide calculations were performed to study the dependence of waveguide design on confinement factor (Γp) and optical losses (α_i) of nitride laser diodes for emission wavelength ranging from 405 nm to 520 nm. We found that the conventional waveguide design containing GaN waveguide and AlGaN cladding layers known from violet laser diode does not support sufficient confinement of the optical mode for long wavelength devices (λ > 450 nm). We proposed a new design consisting of a thick InGaN waveguide which enhances the confinement. We compared the theoretical predictions with laser diodes grown by plasma assisted molecular beam epitaxy.

4

Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

64%

Czapkiewicz M., Cywiński G., Dybko K., Siekacz M., Wolny P., Gierałtowska S., Guziewicz E., Skierbiszewski C., Wróbel J.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1026-1028

EN

We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of HfO_2 or Al_2O_3/HfO_2 composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current I_g< 10^{-11} A at gate voltages |V_g| < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-off voltage at V_g = - 3.5 V at a cost of I_g ≈ 10^{-6} A, which has been identified as a bulk leakage current.

5

Stimulated Emission from the MBE Grown Homoepitaxial InGaN Based Multiple Quantum Wells Structures

52%

Ivanov V., Godlewski M., Miasojedovas S., Juršėnas S., Kazlauskas K., Žukauskas A., Skierbiszewski C., Siekacz M., Leszczyński M., Perlin P., Suski T., Grzegory I.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

225-229

EN

We report on photoluminescence characterization of InGaN based laser structures grown by homoepitaxial radio frequency plasma-assisted molecular beam epitaxy. Owing to Si doped barriers, the structures show a negligible impact of the built-in electric field, which was proved by excitation intensity dependent and quantum well width dependent luminescence experiments. Relatively low variation in band potential due to inhomogeneous distribution of In was quantitatively estimated from the photoluminescence temperature behavior using Monte Carlo simulation of in-plane carrier hopping and optically detected cyclotron resonance experiments. Efficient stimulated emission with a low threshold for optically pumped laser structures was observed.

6

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

52%

Teisseyre H., Szymański M., Khachapuridze A., Skierbiszewski C., Feduniewicz-Żmuda A., Siekacz M., Łucznik B., Kamler G., Kryśko M., Suski T., Perlin P., Grzegory I.

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EN

The intention of this work is to discuss and report on our research on nonpolar laser structures grown on bulk GaN crystal substrates along the (11¯20) nonpolar direction. The main advantages of such nonpolar structures are related to the elimination of the built-in electric fields present in commonly used systems grown along the polar (0001) axis of nitride crystals. We demonstrated the optically pumped laser action on separate confinement heterostructures. Laser action is clearly shown by spontaneous emission saturation, abrupt line narrowing, and strong transversal electric polarization of output light. The lasing threshold was reached at an excitation power density of 260 kW/cm^2 for a 700μm long cavity (at room temperature).

7

High Power Continuous Wave Blue InAlGaN Laser Diodes Made by Plasma Assisted MBE

52%

Skierbiszewski C., Siekacz M., Wiśniewski P., Perlin P., Feduniewicz-Żmuda A., Cywiński G., Smalc J., Grzanka S., Grzegory I., Leszczyński M., Porowski S.

Acta Physica Polonica A

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2006

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vol. 110

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issue 3

345-351

EN

Room temperature, continuous wave operation of InGaN multi-quantum wells laser diodes made by rf plasma assisted molecular beam epitaxy at 411 nm wavelength is demonstrated. The threshold current density and voltage were 4.2 kA/cm^2 and 5.3 V, respectively. High optical power output of 60 mW was achieved. The lifetime of these laser diodes exceeds 5 h with 2 mW of optical output power. The laser diodes are fabricated on low dislocation density bulk GaN substrates, at growth conditions which resembles liquid phase epitaxy. We demonstrate that relatively low growth temperatures (600-700°C) pose no intrinsic limitations for fabrication of nitride optoelectronic components by plasma assisted molecular beam epitaxy.

8

Crack Free GaInN/AlInN Multiple Quantum Wells Grown on GaN with Strong Intersubband Absorption at 1.55μm

52%

Cywiński G., Skierbiszewski C., Feduniewicz-Żmuda A., Siekacz M., Nevou L., Doyennette L., Julien F., Prystawko P., Kryśko M., Grzanka S., Grzegory I., Porowski S.

Acta Physica Polonica A

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2006

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vol. 110

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issue 2

175-181

EN

Crack free GaInN/AlInN multiple quantum wells were grown by rf plasma-assisted molecular beam epitaxy on (0001) GaN/sapphire substrates. The strain-engineering concept was applied to eliminate cracking effect for growth of intersubband structures on GaN. Indium contained ternary compounds of barrier and well layers are contrary strained to the substrate material. A series of crack free GaInN/AlInN intersubband structures on (0001) GaN was fabricated and investigated. The assumed composition and layered structure were confirmed by room temperature photoluminescence and X-ray diffraction measurements. The intersubband measurements were done in multipass waveguide geometry by applying direct intersubband absorption and photoinduced intersubband absorption measurements. The optimized structure design contains forty periods of Si-doped GaInN/AlInN quantum wells and exhibits strong intersubband absorption.

9

Enhancement of Intersubband Absorption in GaInN/AlInN Quantum Wells

52%

Cywiński G., Skierbiszewski C., Siekacz M., Kryśko M., Feduniewicz-Żmuda A., Gladysiewicz M., Kudrawiec R., Misiewicz J., Nevou L., Kheirodin N., Julien F.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1093-1099

EN

GaInN/AlInN multiple quantum wells were grown by RF plasma-assisted molecular beam epitaxy on (0001) GaN/sapphire substrates. The strain-engineering concept was applied to eliminate cracking effect and to improve optical parameters of intersubband structures grown on GaN substrates. The high quality intersubband structures were fabricated and investigated as an active region for applications in high-speed devices at telecommunication wavelengths. We observed the significant enhancement of intersubband absorption with an increase in the barrier thickness. We attribute this effect to the better localization of the second electron level in the quantum well. The strong absorption is very important on the way to intersubband devices designed for high-speed operation. The experimental results were compared with theoretical calculations which were performed within the electron effective mass approximation. A good agreement between experimental data and theoretical calculations was observed for the investigated samples.

Refine search results

Zero Field Spin Splitting in GaN/AlGaN Heterostructures Probed by the Weak Antilocalization

Electron-Electron Interaction Effects in Quantum Hall Regime of GaN/AlGaN Heterostructures

Waveguide Design for Long Wavelength InGaN Based Laser Diodes

Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

Stimulated Emission from the MBE Grown Homoepitaxial InGaN Based Multiple Quantum Wells Structures

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

High Power Continuous Wave Blue InAlGaN Laser Diodes Made by Plasma Assisted MBE

Crack Free GaInN/AlInN Multiple Quantum Wells Grown on GaN with Strong Intersubband Absorption at 1.55μm

Enhancement of Intersubband Absorption in GaInN/AlInN Quantum Wells