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Carrier recombination in sonochemically synthesized ZnO powders

Zakirov M. I., Korotchenkov O. A.

Materials Science Poland

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2017

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Vol. 35, No. 1

211--216

EN

ZnO powders with particle size in the nm to μm range have been fabricated by sonochemical method, utilizing zinc acetate and sodium hydroxide as starting materials. Carrier recombination processes in the powders have been investigated using the photoluminescence, FT-IR and surface photovoltage techniques. It has been shown that the photoluminescence spectra exhibit a number of defect-related emission bands which are typically observed in ZnO lattice and which depend on the sonication time. It has been found that the increase of the stirring time results in a faster decay of the photovoltage transients for times shorter than approximately 5 ms. From the obtained data it has been concluded that the sonication modifies the complicated trapping dynamics from volume to surface defects, whereas the fabrication method itself offers a remarkably convenient means of modifying the relative content of the surface-to-volume defect ratio in powder grains and altering the dynamics of photoexcited carriers.

2

Two-dimensional modeling of surface photovoltage in metal/insulator/n-GaN structure with cylindrical symmetry

Matys M, Powroznik P, Powroznik P, Kupka D, Adamowicz B

Optica Applicata

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2013

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Vol. 43, nr 1

47--52

EN

The rigorous numerical analysis of the surface photovoltage (SPV) versus excitation UV-light intensity (Φ), from 104 to 1020 photon/(cm2s) in a metal/insulator/n-GaN structure with a negative gate voltage (VG = –2 V) was performed using a finite element method. In the simulations we assumed a continuous U-shape density distribution function Dit(E) of the interface states and n-type doping concentration ND = 1016 cm–3. The SPV signal was calculated and compared in three different characteristic regions at the interface, namely i) under the gate centre, ii) near the gate edge and iii) between the gate and ohmic contact. We attributed the differences in SPV(Φ) dependences to the influence of the interface states in terms of the initial band bending and interface recombination controlled by the gate bias. The obtained results are useful for the design of GaN-based UV-radiation photodetectors.

3

Modelowanie zjawisk fotoelektrycznych w zakresie ultrafioletu w strukturach metal/izolator/GaN

Adamowicz B., Bidziński P., Miczek M., Matys M.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 9

43-45

PL

W pracy przedstawiono teoretyczną analizę wpływu stanów elektronowych na granicy izolator/GaN oraz jakości objętości GaN (czasu życia nośników nadmiarowych) na fotopojemność i fotonapięcie powierzchniowe w spolaryzowanej elektrycznie strukturze metal/izolator/GaN oświetlonej promieniowaniem ultrafioletowym. Obliczenia wykonano korzystając z równań modelu dryftowo-dyfuzyjnego rozwiązywanych metodą elementów skończonych w pakiecie COMSOL Multiphysics. Analizę przeprowadzono pod kątem zastosowania struktury w detekcji ultrafioletu.

EN

The paper contains the theoretical analysis of the influence of electron states at an insulator/GaN mterface and of GaN bulk quality (in terms of carrier lifetime) on photocapacitance and surface photovoltage in the metal/insulator/n-GaN structure under ultraviolet light illumination and under the metal gate bias. The calculations have been done using the equations of the drift-diffusion model solved utilizing finite element method in COMSOL Multiphysics package The results have been analyzed from the viewpoint of the application of the structure for ultraviolet detection.