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1

A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

100%

Dróżdż P., Korona K., Sarzyński M., Czernecki R., Skierbiszewski C., Muzioł G., Suski T.

Acta Physica Polonica A

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2016

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vol. 130

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issue 5

1209-1212

EN

The potential fluctuations in III-nitride quantum wells lead to many effects like emission broadening and S-shape energy vs. temperature dependence. The best description of the energy dependence comes from calculations based on Gaussian density of states. However, in most of the published reports, changes of carrier lifetime with energy and temperature are not taken into account. Since experimental evidence shows that lifetime significantly depends on energy and temperature, here we propose a model that describes two basic parameters of luminescence: lifetime of carries and emission energy as a function of temperature in the case of quantum wells and layers that are characterized by potential fluctuations. Comparison of the measured energy and lifetime dependences on temperature in specially grown InGaN/GaN quantum wells and InAlGaN layer shows very good agreement with the proposed theoretical approach.

2

Interplay between Internal and External Electric Field Studied by Photoluminescence in InGaN/GaN Light Emitting Diodes

100%

Staszczak G., Khachapuridze A., Grzanka S., Czernecki R., Piotrzkowski R., Perlin P., Suski T.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

891-893

EN

We have studied a series of polar InGaN/GaN light emitting diodes, consisting of either a blue (440-450 nm) quantum well, or combination of blue and violet (410 nm) quantum wells (with indium content 18% and 10%, respectively). The blue quantum well was always placed close to p-type region of the particular LED. We found that the electroluminescence induced by low current is characterized by light emission from the blue quantum well only. In comparison, optical excitation of our LEDs leads to light emission with energies characteristic either for blue and/or violet quantum wells. The corresponding microphotoluminescence spectra evolve depending on external polarization and variable light intensity of excitation supplied by He-Cd laser. Interplay between built-in electric field and externally applied polarization/screening decides about the band structure profiles and thus radiative recombination mechanisms.

3

Impact of Thin LT-GaN Cap Layers on the Structural and Compositional Quality of MOVPE Grown InGaN Quantum Wells Investigated by TEM

100%

Ivaldi F., Kret S., Szczepańska A., Czernecki R., Kryśko M., Grzanka S., Leszczyński M.

Acta Physica Polonica A

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2011

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vol. 119

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issue 5

660-662

EN

Two samples containing InGaN quantum wells have been grown by metal-organic vapor phase epitaxy on high pressure grown monocrystalline GaN (0001). Different growth temperatures have been used to grow the wells and the barriers. In one of the samples, a low temperature GaN layer (730°C) has been grown on every quantum well before rising the temperature to standard values (900°C). The samples have been investigated by transmission electron microscopy and X-ray diffraction. Photoluminescence spectra have been measured as well. The influence of the LT-GaN has been investigated in regard to its influence on the structural and compositional quality of the sample.

4

Deep Levels in GaN p-n Junctions Studied by Deep Level Transient Spectroscopy and Laplace Transform Deep-Level Spectroscopy

100%

Dyba P., Placzek-Popko E., Zielony E., Gumienny Z., Grzanka S., Czernecki R., Suski T.

Acta Physica Polonica A

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2011

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vol. 119

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issue 5

669-671

EN

p^+-n GaN diodes were studied by means of conventional deep level transient spectroscopy and Laplace transform deep-level spectroscopy methods within the temperature range of 77-350 K. Deep level transient signal spectra revealed the presence of a majority and minority trap of indistinguishable signatures. The Laplace transform deep-level spectroscopy technique due to its superior resolution allows us to unambiguously identify and characterize the traps. The apparent activation energy and capture cross-section for the majority trap were found to be equal to 0.63 eV and 2 × 10^{-16} cm^2 and for the minority trap 0.66 eV and 1.6 × 10^{-15} cm^2. It has been confirmed that the Laplace transform deep-level spectroscopy technique is a powerful tool in characterization of the traps of close signatures.

5

Light Emission Properties of GaN-Based Laser Diode Structures

84%

Godlewski M., Phillips M., Czernecki R., Targowski G., Perlin P., Leszczyński M., Figge S., Hommel D.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

675-680

EN

Cathodoluminescence is applied for evaluation of in-depth and in-plane variations of light emission from two types of GaN-based laser diode structures. We evaluate in-depth properties of the laser diode emission and demonstrate that potential fluctuations still affect emission of laser diodes for e-beam currents above thresholds for a stimulated emission.

6

Cathodoluminescence Profiling of InGaN-Based Quantum Well Structures and Laser Diodes - In-Plane Instabilities of Light Emission

68%

Godlewski M., Ivanov V., Goldys E., Phillips M., Böttcher T., Figge S., Hommel D., Czernecki R., Prystawko P., Leszczynski M., Perlin P., Grzegory I., Porowski S.

Acta Physica Polonica A

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2003

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vol. 103

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issue 6

689-694

EN

Instabilities of light emission and also of stimulated emission in series of GaN epilayers and InGaN quantum well structures, including laser diode structures, are studied. A stimulated emission is observed under electron beam pumping. This enabled us to study light emission properties from laser structures and their relation to microstructure details. We demonstrate large in-plane fluctuations of light emission and that these fluctuations are also present for excitation densities larger than the threshold densities for the stimulated emission.

7

Relationship between Sample Morphology and Carrier Diffusion Length in GaN Thin Films

68%

Godlewski M., Goldys E., Phillips M., Böttcher T., Figge S., Hommel D., Czernecki R., Prystawko P., Leszczynski M., Perlin P., Wisniewski P., Suski T., Bockowski M., Grzegory I., Porowski S.

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issue 4-5

627-632

EN

Scanning and spot-mode cathodoluminescence investigations of homo- and hetero-epitaxial GaN films indicate a surprisingly small influence of their microstructure on overall intensity of a light emission. This we explain by a correlation between structural quality of these films and diffusion length of free carriers and excitons. Diffusion length increases with improving structural quality of the samples, which, in turn, enhances the rate of nonradiative recombination on structural defects, such as dislocations.

8

Blue Laser on High N_2 Pressure-Grown Bulk GaN

53%

Grzegory I., Boćkowski M., Krukowski S., Łucznik B., Wróblewski M., Weyher J., Leszczyński M., Prystawko P., Czernecki R., Lehnert J., Nowak G., Perlin P., Teisseyre H., Purgał W., Krupczyński W., Suski T., Dmowski L., Litwin-Staszewska E., Skierbiszewski C., Łepkowski S., Porowski S.

Acta Physica Polonica A

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2001

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vol. 100

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issue Supplement

229-232

EN

In this note we report briefly on the details of pulsed-current operated "blue" laser diode, constructed in our laboratories, which utilizes bulk GaN substrate. As described in Ref. [1] the substrate GaN crystal was grown by HNPSG method, and the laser structure was deposited on the conducting substrate by MOCVD techniques (for the details see Sec. 2 and Sec. 4 of Ref.~[1], respectively).

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A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

Interplay between Internal and External Electric Field Studied by Photoluminescence in InGaN/GaN Light Emitting Diodes

Impact of Thin LT-GaN Cap Layers on the Structural and Compositional Quality of MOVPE Grown InGaN Quantum Wells Investigated by TEM

Deep Levels in GaN p-n Junctions Studied by Deep Level Transient Spectroscopy and Laplace Transform Deep-Level Spectroscopy

Light Emission Properties of GaN-Based Laser Diode Structures

Cathodoluminescence Profiling of InGaN-Based Quantum Well Structures and Laser Diodes - In-Plane Instabilities of Light Emission

Relationship between Sample Morphology and Carrier Diffusion Length in GaN Thin Films

Blue Laser on High N_2 Pressure-Grown Bulk GaN