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- ItemGrowth and Properties of Intentionally Carbon-Doped GaN Layers(Weinheim : Wiley-VCH, 2019) Richter, Eberhard; Beyer, Franziska C.; Zimmermann, Friederike; Gärtner, Günter; Irmscher, Klaus; Gamov, Ivan; Heitmann, Johannes; Weyers, Markus; Tränkle, GüntherCarbon-doping of GaN layers with thickness in the mm-range is performed by hydride vapor phase epitaxy. Characterization by optical and electrical measurements reveals semi-insulating behavior with a maximum of specific resistivity of 2 × 1010 Ω cm at room temperature found for a carbon concentration of 8.8 × 1018 cm−3. For higher carbon levels up to 3.5 × 1019 cm−3, a slight increase of the conductivity is observed and related to self-compensation and passivation of the acceptor. The acceptor can be identified as CN with an electrical activation energy of 0.94 eV and partial passivation by interstitial hydrogen. In addition, two differently oriented tri-carbon defects, CN-a-CGa-a-CN and CN-a-CGa-c-CN, are identified which probably compensate about two-thirds of the carbon which is incorporated in excess of 2 × 1018 cm−3. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCurrent Status of Carbon‐Related Defect Luminescence in GaN(Weinheim : Wiley-VCH, 2021) Zimmermann, Friederike; Beyer, Jan; Röder, Christian; Beyer, Franziska C.; Richter, Eberhard; Irmscher, Klaus; Heitmann, JohannesHighly insulating layers are a prerequisite for gallium nitride (GaN)-based power electronic devices. For this purpose, carbon doping is one of the currently pursued approaches. However, its impact on the optical and electrical properties of GaN has been widely debated in the scientific community. For further improvement of device performance, a better understanding of the role of related defects is essential. To study optically active point defects, photoluminescence is one of the most frequently used experimental characterization techniques. Herein, the main recent advances in the attribution of carbon-related photoluminescence bands are reviewed, which were enabled by the interplay of a refinement of growth and characterization techniques and state-of-the-art first-principles calculations developed during the last decade. The predicted electronic structures of isolated carbon defects and selected carbon-impurity complexes are compared to experimental results. Taking into account both of these, a comprehensive overview on the present state of interpretation of carbon-related broad luminescence bands in bulk GaN is presented.
- ItemSuppression of particle formation by gas-phase pre-reactions in (100) MOVPE-grown β -Ga2O3films for vertical device application(Melville, NY : American Inst. of Physics, 2023) Chou, Ta-Shun; Seyidov, Palvan; Bin Anooz, Saud; Grüneberg, Raimund; Pietsch, Mike; Rehm, Jana; Tran, Thi Thuy Vi; Tetzner, Kornelius; Galazka, Zbigniew; Albrecht, Martin; Irmscher, Klaus; Fiedler, Andreas; Popp, AndreasThis work investigated the metalorganic vapor-phase epitaxy (MOVPE) of (100) β-Ga2O3 films with the aim of meeting the requirements to act as drift layers for high-power electronic devices. A height-adjustable showerhead achieving a close distance to the susceptor (1.5 cm) was demonstrated to be a critical factor in increasing the stability of the Ga wetting layer (or Ga adlayer) on the surface and reducing parasitic particles. A film thickness of up to 3 μm has been achieved while keeping the root mean square below 0.7 nm. Record carrier mobilities of 155 cm2 V-1 s-1 (2.2 μm) and 163 cm2 V-1 s-1 (3 μm) at room temperature were measured for (100) β-Ga2O3 films with carrier concentrations of 5.7 × 1016 and 7.1 × 1016 cm-3, respectively. Analysis of temperature-dependent Hall mobility and carrier concentration data revealed a low background compensating acceptor concentration of 4 × 1015 cm-3.