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Magdeburg-rothensee, Germany

Dadgar A.,Otto Von Guericke University of Magdeburg | Groh L.,Otto Von Guericke University of Magdeburg | Groh L.,AZZURRO Semiconductors | Metzner S.,Otto Von Guericke University of Magdeburg | And 8 more authors.
Applied Physics Letters | Year: 2013

We report on an over 50% reduction in polarization field strength in c-axis oriented InGaN multi-quantum wells (MQW) by applying quaternary AlGaInN barrier layers with better polarization matching to InGaN than GaN barriers. With the reduction in polarization fields, a strong blue-shift in photoluminescence is observed in agreement with theoretical expectation and simulations. By gracing incidence x-ray diffraction measurements, we demonstrate that partial relaxation already occurs for GaN/InGaN MQWs. As a consequence, the requirement of higher In-content layers for green light emission is in conflict with increasing strain leading to lattice relaxation. © 2013 American Institute of Physics. Source

AZZURRO Semiconductors | Date: 2011-12-23

A group-III-nitride based layer sequence fabricated by means of an epitaxial process on a silicon substrate, the layer sequence comprising at least one doped first group-III-nitride layer (

AZZURRO Semiconductors | Date: 2012-03-02

A semiconductor light emitter device for emitting light having a photon energy, comprises a mechanical carrier made substantially of a material that is an absorbant of the light with the photon energy, and having a carrier bottom side and a carrier top side opposite to the carrier bottom side, a layer structure epitaxially deposited on the carrier bottom side of the mechanical carrier and comprising an active-layer stack with at least two semiconductor layers of opposite conductivity types, which is configured to emit light upon application of a voltage to the active-layer stack, and at least one opening in the mechanical carrier, the opening reaching from the carrier bottom side to the carrier top side and being arranged and shaped to allow a passage of light, which is emitted from the active-layer stack, through the opening in the mechanical carrier.

Dadgar A.,Otto Von Guericke University of Magdeburg | Hempel T.,Otto Von Guericke University of Magdeburg | Blasing J.,Otto Von Guericke University of Magdeburg | Schulz O.,AZZURRO Semiconductors | And 4 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2011

GaN growth on silicon has recently found its way into products as transistor devices for high frequencies and high-voltage applications as well as for light emitting diodes (LEDs). Here, we present the importance of high quality GaN layers for growing LED structures and high-voltage transistors on silicon. The major difference is that LED growth on silicon substrates suffers from edge type dislocations during silicon doping while FETs suffer from a lowered breakdown field. We will show that the latter is most likely originating in screw type dislocations. By optimizing GaN material quality the breakdown field strength can be doubled from less than 0.7×106 V/cm up to ∼ 1.5×106 V/cm. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Reiher F.,Otto Von Guericke University of Magdeburg | Dadgar A.,Otto Von Guericke University of Magdeburg | Dadgar A.,AZZURRO Semiconductors | Blasing J.,Otto Von Guericke University of Magdeburg | And 3 more authors.
Journal of Crystal Growth | Year: 2010

We report on the influence of different surface orientations of Si substrates on the properties of GaN-based layer structures grown by metalorganic vapor-phase epitaxy. By using a high-temperature AlN seed layer, a monocrystalline and c-axis-oriented GaN-layer can be obtained on all substrates with Si(1 1 0), Si(1 1 1), Si(1 1 5), Si(1 1 7), and Si(1 1 9) surface planes. In particular, the samples on Si(1 1 0) substrates exhibit a high quality of the GaN layer, which is comparable or even better than that of identically grown test structures on standard Si(1 1 1) substrates. This result can be explained by a more suited epitaxial relation between the c-plane of the high-temperature AlN seed layer and the Si(1 1 0) surface. The crystallographic structure of approximately 500-nm-thick GaN layers on Si(1 1 0) and Si(1 1 1) are analyzed by X-ray diffraction measurements, their surface morphologies by atomic force microscopy, and the optical properties are investigated by photoluminescence measurements. The improved crystallographic quality of GaN on Si(1 1 0) comes along with a more efficient effect of strain compensating interlayers in comparison to GaN layers on Si(1 1 1). © 2009 Elsevier B.V. All rights reserved. Source

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