Growth of β-Ga2O3 and ϵ/κ-Ga2O3 on AlN(0001) by molecular-beam epitaxy

Keobounnam A.N., Lenert-Mondou C., Kubik A., Hawker M.J.

Silk fibroin is a naturally derived polymer with great potential for biomedical use due to its strength, lack of immune response, and ability to biodegrade. The relatively hydrophobic nature of silk, however, can cause challenges with cell adhesion in vivo. Therefore, modification must be performed to improve the surface hydrophilicity, enhancing silk utility in the biomedical space. Low-temperature plasma (LTP) treatment is an established method for polymer modification and has the benefits of being a solvent-free, adaptable process. N2 and H2O(g) LTP treatments are both well-documented as strategies to enhance polar functional groups on a polymer's surface. However, many polymers tend to revert to their original hydrophobic state upon aging, reversing the effects of LTP modification. The hydrophobic recovery of N2 and H2O(g) LTP-modified silk has not been previously studied but has important implications for the uses and longevity of silk substrates in biomedical contexts. The goal of this study was to systematically evaluate the hydrophobic recovery of N2 and H2O(g) LTP-treated silk films. Films were LTP-modified using optimized plasma parameters (applied power, pressure, treatment time) and aged under both ambient and elevated temperature conditions up to 6 weeks after the initial treatment. Silk film surface properties were evaluated immediately after treatment and throughout the aging process using both water contact angle goniometry and x-ray photoelectron spectroscopy. LTP-treated silk films demonstrated a significant decrease in hydrophobicity compared to the untreated controls. Remarkably, both N2 and H2O(g) LTP modifications resulted in surfaces that retained hydrophilic properties over the 6 week aging period. Our findings represent a departure from what has been previously demonstrated in most LTP-modified synthetic polymers, suggesting that the secondary structure of silk fibroin plays a critical role in resisting hydrophobic recovery.

Itoh T., Mauze A., Zhang Y., Speck J.S.

We report the continuous Si doping in β-Ga2O3 epitaxial films grown by plasma-assisted molecular beam epitaxy through the use of a valved effusion cell for the Si source. Secondary ion mass spectroscopy results exhibit that the Si doping profiles in β-Ga2O3 are flat and have sharp turn-on/off depth profiles. The Si doping concentration was able to be controlled by either varying the cell temperatures or changing the aperture of the valve of the Si effusion cell. High crystal quality and smooth surface morphologies were confirmed on Si-doped β-Ga2O3 epitaxial films grown on (010) and (001) substrates. The electronic properties of Si-doped (001) β-Ga2O3 epitaxial film showed an electron mobility of 67 cm2/Vs at the Hall concentration of 3 × 1018 cm−3.

Azizie K., Hensling F.V., Gorsak C.A., Kim Y., Pieczulewski N.A., Dryden D.M., Senevirathna M.K., Coye S., Shang S., Steele J., Vogt P., Parker N.A., Birkhölzer Y.A., McCandless J.P., Jena D., et. al.

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 µm/h with control of the silicon doping concentration from 5 × 1016 to 1019 cm−3. In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 µm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 µm thick films). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the β-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 µm thick film with a mobile carrier concentration of 2.7 × 1017 cm−3 reveal a room-temperature mobility of 124 cm2 V−1 s−1 that increases to 627 cm2 V−1 s−1 at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal–semiconductor field-effect transistors made from these silicon-doped β-Ga2O3 films grown by S-MBE at growth rates of ∼1 µm/h.

McCandless J.P., Rowe D., Pieczulewski N., Protasenko V., Alonso-Orts M., Williams M.S., Eickhoff M., Xing H.G., Muller D.A., Jena D., Vogt P.

Abstract We report the growth of α-Ga2O3 on m-plane α-Al2O3 by conventional plasma-assisted molecular-beam epitaxy and In-mediated metal–oxide-catalyzed epitaxy (MOCATAXY). We report a growth rate diagram for α-Ga2O3( 10 1 ¯ 0 ), and observe (i) a growth rate increase, (ii) an expanded growth window, and (iii) reduced out-of-plane mosaic spread when MOCATAXY is employed for the growth of α-Ga2O3. Through the use of In-mediated catalysis, growth rates over 0.2 μm h−1 and rocking curves with full width at half maxima of Δω ≈ 0.45° are achieved. Faceting is observed along the α-Ga2O3 film surface and explored through scanning transmission electron microscopy.

Polyakov A.Y., Nikolaev V.I., Pechnikov A.I., Yakimov E.B., Karpov S.Y., Stepanov S.I., Shchemerov I.V., Vasilev A.A., Chernykh A.V., Kuznetsov A., Lee I., Pearton S.J.

Typically, semiconducting oxides and nitrides exhibit strong conductivity type asymmetries. In this work, we observed and interpreted the emergence of p-type conductivity at the κ-Ga2O3/AlN interface. Films of lightly Sn-doped -Ga2O3 were deposited by Halide Vapor Phase Epitaxy (HVPE) on AlN/Si templates. Capacitance-voltage (C-V), current-voltage (I-V) measurements on Ni Schottky diodes and Ti/Au Ohmic contacts deposited on the layer surface unexpectedly showed p-type-like behavior, while Electron Beam Induced Current (EBIC) images collected with different beam energies suggest that the EBIC collection occurs near the Ga2O3/AlN interface, which also implies the formation of a p-type layer at this interface. We modelled this effect, taking into account the difference in spontaneous electrical polarization of κ-Ga2O3 and AlN and this indicated a layer of two-dimensional holes can form at this interface. The possibility to detect this layer depends on the balance between the doping level and the thickness of the κ-Ga2O3.

Kang H.Y., Yeom M.J., Yang J.Y., Choi Y., Lee J., Park C., Yoo G., Kyu Chung R.B.

GaN power technology, especially AlGaN/GaN high electron-mobility transistors (HEMTs), has made significant progress in recent years. However, the performance of HEMTs is still limited due to a trade-off between on-resistance and off-state breakdown voltage (BV). Integrating a polar gate dielectric with GaN HEMTs can potentially improve both sheet resistance of the two-dimensional electron gas channel and the field distribution between gate and drain. In this regard, orthorhombic κ-Ga2O3 has attractive properties since it is predicted to be strongly polar and highly dielectric while it grows epitaxially on GaN. By successfully integrating crystalline κ-Ga2O3 on GaN HEMTs, the channel sheet resistance is reduced by 20% from a reference device with amorphous Al2O3 gate dielectric. As a result, the cut-off frequency increases from 4.8 to 9.1 GHz. The dielectric property of κ-Ga2O3 also improves BV from 354 to 380 V by reducing the peak electric field in the gate-drain region.

Hensling F.V., Smeaton M.A., Show V., Azizie K., Barone M.R., Kourkoutis L.F., Schlom D.G.

We demonstrate the epitaxial growth of the first two members, and the [Formula: see text] member of the homologous Ruddlesden–Popper series of [Formula: see text] of which the [Formula: see text] member was previously unknown. The films were grown by suboxide molecular-beam epitaxy where the indium is provided by a molecular beam of indium-suboxide [[Formula: see text]O (g)]. To facilitate ex situ characterization of the highly hygroscopic barium indate films, a capping layer of amorphous [Formula: see text] was deposited prior to air exposure. The structural quality of the films was assessed by x-ray diffraction, reflective high-energy electron diffraction, and scanning transmission electron microscopy.

Bhuiyan A.F., Feng Z., Huang H., Meng L., Hwang J., Zhao H.

Epitaxial growth of κ-phase Ga2O3 thin films is investigated on c-plane sapphire, GaN- and AlN-on-sapphire, and (100) oriented yttria stabilized zirconia (YSZ) substrates via metalorganic chemical vapor deposition. The structural and surface morphological properties are investigated by comprehensive material characterization. Phase pure κ-Ga2O3 films are successfully grown on GaN-, AlN-on-sapphire, and YSZ substrates through a systematical tuning of growth parameters including the precursor molar flow rates, chamber pressure, and growth temperature, whereas the growth on c-sapphire substrates leads to a mixture of β- and κ-polymorphs of Ga2O3 under the investigated growth conditions. The influence of the crystalline structure, surface morphology, and roughness of κ-Ga2O3 films grown on different substrates are investigated as a function of precursor flow rate. High-resolution scanning transmission electron microscopy imaging of κ-Ga2O3 films reveals abrupt interfaces between the epitaxial film and the sapphire, GaN, and YSZ substrates. The growth of single crystal orthorhombic κ-Ga2O3 films is confirmed by analyzing the scanning transmission electron microscopy nanodiffraction pattern. The chemical composition, surface stoichiometry, and bandgap energies of κ-Ga2O3 thin films grown on different substrates are studied by high-resolution x-ray photoelectron spectroscopy (XPS) measurements. The type-II (staggered) band alignments at three interfaces between κ-Ga2O3 and c-sapphire, AlN, and YSZ substrates are determined by XPS, with an exception of κ-Ga2O3/GaN interface, which shows type-I (straddling) band alignment.

Singhal J., Chaudhuri R., Hickman A., Protasenko V., Xing H.G., Jena D.

Due to its high breakdown electric field, the ultra-wide bandgap semiconductor AlGaN has garnered much attention recently as a promising channel material for next-generation high electron mobility transistors (HEMTs). A comprehensive experimental study of the effects of Al composition x on the transport and structural properties is lacking. We report the charge control and transport properties of polarization-induced 2D electron gases (2DEGs) in strained AlGaN quantum well channels in molecular-beam-epitaxy-grown AlN/Al xGa1− xN/AlN double heterostructures by systematically varying the Al content from x = 0 (GaN) to x = 0.74, spanning energy bandgaps of the conducting HEMT channels from 3.49 to 4.9 eV measured by photoluminescence. This results in a tunable 2DEG density from 0 to 3.7 × 1013 cm2. The room temperature mobilities of x ≥ 0.25 AlGaN channel HEMTs were limited by alloy disorder scattering to below 50 cm2/(V.s) for these 2DEG densities, leaving ample room for further heterostructure design improvements to boost mobilities. A characteristic alloy fluctuation energy of [Formula: see text] eV for electron scattering in AlGaN alloy is estimated based on the temperature dependent electron transport experiments.

Krishna S., Lu Y., Liao C., Khandelwal V., Li X.

• High-quality orthorhombic Ga 2 O 3 epitaxial film grown on GaN, AlN and Sapphire substrate by pulsed laser deposition. • A unique type-I band alignment of κ -Ga 2 O 3 with GaN and AlN is observed. • There is a high conduction band offset of 1.38 eV and 1.04 eV for κ-Ga 2 O 3 /GaN, and κ -Ga 2 O 3 /AlN heterostructure. Ga 2 O 3 semiconductors have attracted tremendous research interests because of their fascinating material properties for future-generation energy, electronic, and optoelectronic applications. In the present study, we have performed the epitaxial growth of tin-doped Ga 2 O 3 on sapphire, GaN, and AlN templates by the pulsed laser deposition technique. The initial characterizations show a two-dimensional mode of single-crystalline orthorhombic Ga 2 O 3 (κ-Ga 2 O 3 ) growth on these substrates with smooth surface morphology. Integrating κ-Ga 2 O 3 with nitride semiconductors is interesting since both these materials possess polarization, which could induce 2-dimensional carrier gas (2DCG) at the interface. X-ray photoelectron spectroscopy studies reveal that both κ-Ga 2 O 3 /GaN and κ-Ga 2 O 3 /AlN heterostructure form a type-I band structure where the conduction band offset (CBO) was calculated to be 1.38 eV and 1.04 eV, respectively. This unique band alignment with high CBO could lead to the development of efficient power devices.

Li Y., Zhang Y., Zhang J., Zhang T., Xu S., Feng L., Feng Q., Zhang C., Hao Y.

Abstract β-Ga2O3 films were grown on AlN templates by metal organic chemical vapor deposition (MOCVD), and the properties of the β-Ga2O3/AlN heterostructures were investigated in detail. The β-Ga2O3/AlN heterostructure with abrupt interface was observed by the high resolution transmission electron microscope with high angle annular dark field. The refactor of the atoms at the interface is discussed. Moreover, the band structure of the MOCVD β-Ga2O3/AlN heterostructures was investigated by x-ray photoelectron spectroscopy. The conduction band and valence band offsets of β-Ga2O3/AlN heterostructure were calculated to be −1.44 eV ± 0.05 eV and −0.14 eV ± 0.05 eV, respectively.

Vogt P., Hensling F.V., Azizie K., McCandless J.P., Park J., DeLello K., Muller D.A., Xing H.G., Jena D., Schlom D.G.

We observe a catalytic mechanism during the growth of III-$\mathrm{O}$ and IV-$\mathrm{O}$ materials by suboxide molecular-beam epitaxy ($S$-MBE). By supplying the molecular catalysts ${\mathrm{In}}_{2}\mathrm{O}$ and SnO we increase the growth rates of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. This catalytic action is explained by a metastable adlayer $A$, which increases the reaction probability of the reactants ${\mathrm{Ga}}_{2}\mathrm{O}$ and ${\mathrm{In}}_{2}\mathrm{O}$ with active atomic oxygen, leading to an increase of the growth rates of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. We derive a model for the growth of binary III-$\mathrm{O}$ and IV-$\mathrm{O}$ materials by $S$-MBE and apply these findings to a generalized catalytic description for metal-oxide-catalyzed epitaxy (MOCATAXY), applicable to elemental and molecular catalysts. We introduce a mathematical description of $S$-MBE and MOCATAXY, providing a computational framework to set growth parameters in previously inaccessible kinetic and thermodynamic growth regimes when using the aforementioned catalysis. Our results indicate that MOCATAXY takes place with a suboxide catalyst rather than with an elemental catalyst. As a result of the growth regimes achieved, we demonstrate a ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$/${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ heterostructure with an unrivaled crystalline quality, paving the way for the preparation of oxide device structures with unprecedented perfection.

Ogura Y., Arata Y., Nishinaka H., Yoshimoto M.

Abstract We studied the phase diagram of (In x Ga1−x )2O3 thin films with a composition of x = 0 to 1 on Aluminum Nitride (AlN) templates grown using mist chemical vapor deposition. From X-ray diffraction results, we observed that the (In x Ga1−x )2O3 thin films exhibited three different single-phase crystal structures depending on the value of x: orthorhombic (κ)-(In x Ga1−x )2O3 for x ≤ 0.186, hexagonal (hex)-(In x Ga1−x )2O3 for 0.409 ≤ x ≤ 0.634, and body-centered cubic (bcc)-(In x Ga1−x )2O3 for x ≥ 0.772. The optical bandgap of (In x Ga1−x )2O3 was tuned from 3.27 eV (bcc-In2O3) and 4.17 eV (hex-InGaO3) to 5.00 eV (κ-Ga2O3). Moreover, hex-(In x Ga1−x )2O3 exhibited a wide bandgap (4.30 eV) and a low resistivity (7.4 × 10‒1 Ω·cm). Furthermore, hex-(In x Ga1−x )2O3 thin films were successfully grown on GaN and AlGaN/GaN templates. Therefore, hex-(In x Ga1−x )2O3 can be used in transparent conductive films for deep-ultraviolet LEDs.

Green A.J., Speck J., Xing G., Moens P., Allerstam F., Gumaelius K., Neyer T., Arias-Purdue A., Mehrotra V., Kuramata A., Sasaki K., Watanabe S., Koshi K., Blevins J., Bierwagen O., et. al.

Gallium Oxide has undergone rapid technological maturation over the last decade, pushing it to the forefront of ultra-wide band gap semiconductor technologies. Maximizing the potential for a new semiconductor system requires a concerted effort by the community to address technical barriers which limit performance. Due to the favorable intrinsic material properties of gallium oxide, namely, critical field strength, widely tunable conductivity, mobility, and melt-based bulk growth, the major targeted application space is power electronics where high performance is expected at low cost. This Roadmap presents the current state-of-the-art and future challenges in 15 different topics identified by a large number of people active within the gallium oxide research community. Addressing these challenges will enhance the state-of-the-art device performance and allow us to design efficient, high-power, commercially scalable microelectronic systems using the newest semiconductor platform.

Higashiwaki M.

Rapid progress in β-gallium oxide (β-Ga2O3) material and device technologies has been made in this decade, and its superior material properties based on the very large bandgap of over 4.5 eV have been attracting much attention. β-Ga2O3 appears particularly promising for power switching device applications because of its extremely large breakdown electric field and availability of large-diameter, high-quality wafers manufactured from melt-grown bulk single crystals. In this review, after introducing material properties of β-Ga2O3 that are important for electronic devices, current status of bulk melt growth, epitaxial thin-film growth, and device processing technologies are introduced. Then, state-of-the-art β-Ga2O3 Schottky barrier diodes and field-effect transistors are discussed, mainly focusing on development results of the author’s group.

Lee J., Oh J., Kim J., Kim W., Koo S., Kim S., Kim M., Park C., Shin W.H., Won K., Oh J.

Taboada Vasquez J.M., Li X.

The demand for compact, high‐power electronic devices, such as power trains, and smartphone chargers, continues to grow, driving advancements in power electronics. Traditional silicon‐based semiconductors are increasingly unable to meet the performance requirements of these applications due to their physical limitations. As a result, wide bandgap (WBG) materials like silicon carbide and gallium nitride are now widely used for their superior capabilities, although their fabrication remains costly and complex. Recently, gallium oxide (Ga2O3) has emerged as a promising alternative, offering an ultra WBG of 4.8 eV and a breakdown electric field of 8 MV cm−1 while benefiting from relatively simple and cost‐effective growth methods. Despite these advantages, Ga2O3 has limitations, including low electron mobility and poor thermal management, which restrict its use primarily to high‐voltage, low‐frequency applications such as diodes. This article analyzes recent developments in Ga2O3 diodes, providing an overview of their properties, fabrication techniques, and application‐specific performance. The challenges Ga2O3 diodes currently face are examined, particularly in thermal management and electron mobility, and ongoing research efforts aimed at overcoming these issues to enable broader use of Ga2O3 diodes in power electronics are discussed.

Choudhary R., Jalan B.

Wang L., Wang Y., Feng Q., Zhang Y., Zhang J., Hao Y.

Seguret A., Okuno H., Roussel H., Rouvière J., Bujak A., Ferrandis P., Bellet-Amalric E., Consonni V., Monroy E.

Yang Y., Han D., Wu S., Lin H., Zhang J., Zhang W., Ye J.

Abstract To achieve high-quality solar-blind ultraviolet (UV) imaging applications based on ultrawide bandgap semiconductor photodetectors, it is crucial to fabricate highly uniform wafer-scale films. In this work, we demonstrate the fabrication of exceptionally uniform two-inch ϵ-Ga2O3 thin films on sapphire substrates using an off-axis pulsed laser deposition method. The two-inch ϵ-Ga2O3 films exhibit remarkable uniformity across key parameters, including thickness, crystalline quality, bandgap, and surface roughness, with an inhomogeneity ratio less than 5%. Additionally, these films are preferentially oriented along the (001) crystal plane. At 20 V bias, the individual ϵ-Ga2O3 photodetector demonstrates outstanding solar-blind UV photodetection performance, with a responsivity of 52.77 A W−1 at 240 nm, an external quantum efficiency of 2.7 × 104%, a dark current of 5.5 × 10−11 A and a UV–visible rejection ratio of 1.2 × 104. Furthermore, the 10 × 10 photodetector arrays fabricated on two-inch ϵ-Ga2O3 films exhibit highly uniform photodetection performance, with photocurrent deviations remaining within one order of magnitude and a maximum standard deviation of ∼8%. High-contrast optical imaging of the letters of ‘NIMTE’ is successfully achieved using the 10 × 10 photodetector arrays. This work provides valuable insights for fabricating wafer-scale uniform ϵ-Ga2O3 films and achieving high-quality solar-blind UV imaging applications.

Vogt P., Shang S., Liu Z.

General MBE reaction scheme for binary III–VI and IV–VI materials. It presents the complex, consecutive reaction pathways of the adsorbed metal (e.g., Ga), via its subcompound (e.g., Ga2Se), to its solid-state ground state (e.g., Ga2Se3).

Wang Y., Zhao S., Xiao H., Wang J., Hu P., Qiao J., Zhang Y., Hu H.

InSe/β-Ga2O3 heterojunction detects 230 nm deep UV under zero bias.

Wang L., Qin X., Zhang L., Xu K., Yang F., Lu S., Li Y., Liu B., Yu G., Zeng Z., Zhang B.

Abstract In this work, AlN films were grown using gallium (Ga) as surfactant on 4° off-axis 4H-SiC substrates via microwave plasma chemical vapor deposition (MPCVD). We have found that AlN growth rate can be greatly improved due to the catalytic effect of trimethyl-gallium (TMGa), but AlN crystal structure and composition are not affected. When the proportion of TMGa in gas phase was low, crystal quality of AlN can be improved and three-dimensional growth mode of AlN was enhanced with the increase of Ga source. When the proportion of TMGa in gas phase was high, two-dimensional growth mode of AlN was presented, with the increase of Ga source results in the deterioration of AlN crystal quality. Finally, employing a two-step growth approach, involving the initial growth of Ga-free AlN nucleation layer followed by Ga-assisted AlN growth, high quality of AlN film with flat surface was obtained and the full width at half maximum (FWHM) values of 415 nm AlN (002) and (102) planes were 465 and 597 arcsec.

Yan Z., Li S., Liu Z., Yue J., Ji X., Wang J., Hou S., Wu G., Lei J., Sun G., Li P., Tang W.

Ga2O3, with its large band gap, is a promising material suitable for utilization in solar-blind photodetection. Sapphire with a higher lattice match with Ga2O3 was used as the substrate for epitaxial growth of Ga2O3. Here, the epitaxial layers of Ga2O3 were deposited by MOCVD on patterned sapphire substrates. The structure of epitaxial Ga2O3 layers on patterned substrates has been identified by X-ray diffractometry. To investigate the influence of the patterned substrates on the formation of epitaxial layers, thin Ga2O3 layers were grown on a flat sapphire substrate under the same conditions. Both types of samples were β-phase. However, no improvement in the layers’ crystalline quality was discovered when utilizing patterned sapphire substrates. In addition, the performance of the obtained two types of Ga2O3 photodetectors was compared. The photoelectric properties, such as responsivity, response speed, and detection capability, were different in the case of flat samples.

Kalanov D., Gerlach J.W., Bundesmann C., Bauer J., Lotnyk A., von Wenckstern H., Anders A., Unutulmazsoy Y.

Deposition of epitaxial oxide semiconductor films using physical vapor deposition methods requires a detailed understanding of the role of energetic particles to control and optimize the film properties. In the present study, Ga2O3 thin films are heteroepitaxially grown on Al2O3(0001) substrates using oxygen ion beam sputter deposition. The influence of the following relevant process parameters on the properties of the thin films is investigated: substrate temperature, oxygen background pressure, energy of primary ions, ion beam current, and sputtering geometry. The kinetic energy distributions of ions in the film-forming flux are measured using an energy-selective mass spectrometer, and the resulting films are characterized regarding crystalline structure, microstructure, surface roughness, mass density, and growth rate. The energetic impact of film-forming particles on the thin film structure is analyzed, and a noticeable decrease in crystalline quality is observed above the average energy of film-forming Ga+ ions around 40 eV for the films grown at a substrate temperature of 725 °C.

Zhang S., Yuan H., Wang P., Ren L., Wang Y., Xia Z., Li B., Tu R., Goto T., Zhang L.

Raghuvansy S., McCandless J.P., Schowalter M., Karg A., Alonso-Orts M., Williams M.S., Tessarek C., Figge S., Nomoto K., Xing H.G., Schlom D.G., Rosenauer A., Jena D., Eickhoff M., Vogt P.