A. Dadgar

Otto-von-Guericke University Magdeburg

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A. Krost

Otto-von-Guericke University Magdeburg

203

J. Bläsing

Otto-von-Guericke University Magdeburg

118

J. Christen

Otto-von-Guericke University Magdeburg

F. Bertram

Otto-von-Guericke University Magdeburg

A. Diez

Universidad Carlos III de Madrid

A. Strittmatter

Otto-von-Guericke University Magdeburg

Thomas Hempel

Westsächsische Hochschule Zwickau

H. De Witte

KU Leuven

Peter Veit

Otto-von-Guericke University Magdeburg

A. Krtschil

Otto-von-Guericke University Magdeburg

Cooperative Institutions

Otto-von-Guericke University Magdeburg

123

Technische Universität Berlin

Centre National de la Recherche Scientifique

RWTH Aachen University

University Hospital Magdeburg

Technische Universität Ilmenau

Universität Ulm

University of Freiburg

Aixtron (Germany)

Technical University of Darmstadt

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Time-delayed indium incorporation in ultrathin (InxGa1−xN/GaN) multiple quantum wells grown by metalorganic vapor phase epitaxy

Applied Physics Letters (2003)

F. Schulze J. Bläsing A. Dadgar A. Krost

In x Ga 1−x N/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy were investigated by x-ray reflectometry and high-resolution x-ray diffractometry. The combination of both analysis methods allows a very precise determination of the structural parameters of the layer systems. From a systematic variation of the growth temperature from 760 to 840 °C and deposition times from 15 to 200 s, a temperature-dependent time delay of the indium incorporation was observed. Preferentially, at lower growth temperatures, indium seems to be accumulated at the GaN surface before the onset of the InGaN quantum well growth. The growth delay increases with decreasing growth temperature.

Reflectometry

Vapor phase

10.1063/1.1586472

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Citations (16)

P-Channel InGaN-HFET Structure Based on Polarization Doping

IEEE Electron Device Letters (2004)

Tom Zimmermann Martin Neuburger M. Kunze I. Daumiller Andrej Denisenko

A p-channel GaN-based heterostructure field-effect transistor (HFET) concept based on a two-dimensional hole gas (2DHG) induced by polarization doping is presented. The structure employed is a GaN-InGaN-GaN heterostructure without external acceptor doping. The p-channel 2DHG characteristics are verified by operation at low temperature (20 K) and capacitance-voltage profiling. Hall measurements result in a positive Hall-coefficient and indicate a 2DHG hole mobility of approximately 700 cm ² /Vs at 66 K. For an optimum structure supported by extrinsic doping a simulated output current of approximately 100 mA/mm is predicted for a gate length of 0.5 μm.

Acceptor

Wide-bandgap semiconductor

10.1109/led.2004.830285

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Citations (65)

Epitaxy of GaN on silicon—impact of symmetry and surface reconstruction

New Journal of Physics (2007)

A. Dadgar F. Schulze M. Wienecke Aniko Gadanecz J. Bläsing

GaN-on-silicon is a low-cost alternative to growth on sapphire or SiC. Today epitaxial growth is usually performed on Si(111), which has a threefold symmetry. The growth of single crystalline GaN on Si(001), the material of the complementary metal oxide semiconductor (CMOS) industry, is more difficult due to the fourfold symmetry of this Si surface leading to two differently aligned domains. We show that breaking the symmetry to achieve single crystalline growth can be performed, e.g. by off-oriented substrates to achieve single crystalline device quality GaN layers. Furthermore, an exotic Si orientation for GaN growth is Si(110), which we show is even better suited as compared to Si(111) for the growth of high quality GaN-on-silicon with a nearly threefold reduction in the full width at half maximum (FWHM) of the -scan. It is found that a twofold surface symmetry is in principal suitable for the growth of single crystalline GaN on Si.

Silicon on sapphire

10.1088/1367-2630/9/10/389

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Citations (138)

In-situ growth monitoring of AlInN/AlGaN distributed Bragg reflectors for the UV-spectral range

Journal of Crystal Growth (2012)

Christoph Berger A. Dadgar J. Bläsing A. Krost

10.1016/j.jcrysgro.2012.08.046

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Citations (18)

MOVPE growth of high-quality ZnO

N. Oleynik A. Dadgar Daniel F. Förster F. Bertram S. Deiter

10.1285/i9788883050088p85

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Citations (0)

Optical characterization of a InGaN/GaN microcavity with epitaxial AlInN/GaN bottom DBR

MRS Proceedings (2012)

Alexander Franke B. Bastek S. Sterling Olga August S. Petzold

10.1557/opl.2012.83

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Metalorganic vapor phase epitaxy grown InGaN∕GaN light-emitting diodes on Si(001) substrate

Applied Physics Letters (2006)

F. Schulze A. Dadgar J. Bläsing A. Diez A. Krost

We present GaN-based light emitting diode structures on a Si(001) substrate. The 2.3μm thick, crack-free layers were grown by metalorganic vapor phase epitaxy using a high-temperature AlN seed layer and 4° off-oriented substrates. This allows us to grow a flat, fully coalesced, and single crystalline GaN layer on Si(001). For preventing crack formation, four AlN interlayers were inserted in the buffer structure. The optically active layers consist of five-fold InGaN∕GaN multiple quantum wells showing a bright electroluminescence at 490nm at room temperature. The crystallographic structure was analyzed by x-ray diffraction measurements and the optical properties were determined by photo- and electroluminescence.

Vapor phase

Wide-bandgap semiconductor

10.1063/1.2188383

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Citations (43)

Bright blue electroluminescence from an InGaN/GaN multiquantum-well diode on Si(111): Impact of an AlGaN/GaN multilayer

Applied Physics Letters (2001)

A. Dadgar J. Christen T. Riemann Shachar Richter J. Bläsing

We present an electroluminescence test structure which consists of an InGaN/GaN multiquantum well as active region on the top of an AlGaN/GaN multilayer grown by metalorganic vapor phase epitaxy on Si(111) substrate. The integral room-temperature electroluminescence spectrum reveals a peak emission wavelength of 467 nm and a significantly higher brightness than an identical reference structure on sapphire substrate. In microelectroluminescence imaging, two emission peaks at 465 and 476 nm can be separated originating from locally different areas of the diode. Cathodoluminescence measurements in cross section and high-resolution x-ray diffraction measurements show that the structure is less strained than a sample without the AlGaN/GaN multilayer. The AlGaN/GaN multiple layer sequence which has a total thickness of 1.5 μm causes lattice relaxation during growth after a thickness of around 0.9 μm as directly visualized by cathodoluminescence line scans across the diode.

Cathodoluminescence

Wide-bandgap semiconductor

10.1063/1.1362327

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Citations (105)

Ruthenium: A superior compensator of InP

Applied Physics Letters (1998)

A. Dadgar O. Stenzel A. Näser M. Zafar Iqbal D. Bimberg

The 4d-transition metal ruthenium presents a new dopant to fabricate thermally stable semi-insulating InP layers for both electron and hole injection. The layers are grown by low-pressure metalorganic chemical vapor deposition using tertiarybutylphosphine and trimethylindium as source materials for InP growth. Using bis(η5-2,4-dimethyl-pentadienyl)ruthenium(II) as precursor Ru doping concentrations of the order of 4×1018 cm−3 are achieved, determined by means of secondary ion mass spectroscopy. The Ru diffusion coefficient in InP is determined to DRu(800 °C)⩽1×10−15 cm2/s which is four orders of magnitude smaller than for Fe. Resistivities obtained under electron and hole injection are above 6×107 Ω cm and 5×108 Ω cm, respectively. In deep level transient spectroscopy measurements under electron emission and hole emission, one deep level each with concentrations around 1016 cm−3, is observed.

Trimethylindium

Deep-level transient spectroscopy

Electron Mobility

10.1063/1.122898

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Citations (32)

Reduction of on-resistance and current crowding in quasi-vertical GaN power diodes

Applied Physics Letters (2017)

Yuhao Zhang Min Sun Daniel Piedra Jonas Hennig A. Dadgar

This paper studies the key parameters affecting on-resistance and current crowding in quasi-vertical GaN power devices by experiment and simulation. The current distribution in the drift region, n−-GaN, was found to be mainly determined by the sheet resistance of the current spreading layer, n+-GaN. The actual on-resistance of the drift region significantly depends on this current distribution rather than the intrinsic resistivity of the drift layer. As a result, the total specific on-resistance of quasi-vertical diodes shows a strong correlation with the device area and sheet resistance of the current spreading layer. By reducing the sheet resistance of the current spreading layer, the specific on-resistance of quasi-vertical GaN-on-Si power diodes has been reduced from ∼10 mΩ·cm2 to below 1 mΩ·cm2. Design space of the specific on-resistance at different breakdown voltage levels has also been revealed in optimized quasi-vertical GaN power diodes.

Current crowding

Wide-bandgap semiconductor

Spreading resistance profiling

10.1063/1.4989599

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Citations (42)