Papers by Author: Jörg Pezoldt

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Authors: Katja Tonisch, Wael Jatal, Ralf Granzner, Mario Kittler, Uwe Baumann, Frank Schwierz, Jörg Pezoldt
Abstract: We present the realization of high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures grown on silicon substrates using a SiC transition layer. The growth of AlGaN/GaN heterostructures on Si (111) was performed using metalorganic chemical vapour deposition (MOCVD). The (111) SiC transition layer was realized by low pressure CVD and prevented Ga-induced meltback etching and Si-outdiffusion in the subsequent MOCVD growth. The two-dimensional electron gas (2DEG) formed at the AlGaN/GaN interface showed an electron sheet density of 1.5x1013 cm-3 and a mobility of 870 cm²/Vs proving the high structural quality of the heterostructure. Device processing was done using electron beam lithography. DC and RF characteristics were analysed and showed a peak cut-off frequency as high as 6 GHz for a 1.2 µm gate HEMT.
Authors: Yu.V. Truschin, R.A. Yankov, V.S. Kharlamov, D.V. Kulikov, D.N. Tsigankov, U. Kreissig, M. Voelskow, Jörg Pezoldt, Wolfgang Skorupa
Authors: Katja Tonisch, Robert Benzig, Gernot Ecke, Jörg Pezoldt
Abstract: The growth of AlGaN solid solutions on 3C-SiC(111)/Si(111) is demonstrated. The residual stress of the grown layer was investigated by high resolution X-ray diffraction (HRXRD) and infrared ellipsometry. Analysis of the HRXRD data showed that the observed lattice distortion was caused partially by hydrostatic pressure and partially by biaxial tension. The residual stress depends on the layer composition and weakly on the growth temperature.
Authors: Wael Jatal, Katja Tonisch, Uwe Baumann, Frank Schwierz, Jörg Pezoldt
Abstract: Al0.35Ga0.65N/GaN- and Al0.2Ga0.8N/AlN/GaN-heterostructures high electron mobility transistors (HEMTs) with a gate length (LG) varying from 1.2 to 0.08 µm were fabricated on silicon Si(111) substrates using a 3C-SiC transition layer. Metal organic chemical vapour deposition (MOCVD) was used to growth the AlGaN-heterostructures and a low pressure chemical vapour deposition (LPCVD) to create the 3C-SiC(111) transition layer preventing Ga-induced melt back etching and Si-out diffusion. Reduced Al content and an AlN interlayer improved the device performance. The HEMTs with LG=0.08µm had a maximum drain current density of 1.25 A/mm and a peak extrinsic transconductance of 400 mS/mm. A unity current gain cut-off frequency (ƒT) of 180 GHz and maximum frequency (ƒmax) of 70 GHz were measured on these devices.
Authors: Jörg Pezoldt, Bernd Hähnlein, Heiko O. Jacobs, Frank Schwierz
Abstract: All carbon three terminal junctions were fabricated from epitaxial graphene grown on semiinsulating Si-face 4H-SiC. It is demonstrated that self-contained gate devices exhibit current modulation characteristics. The obtained current gain depends on the device design and is controlled by the applied gate voltage.
Authors: Jörg Pezoldt, Thomas Kups, Petia Weih, Thomas Stauden, Oliver Ambacher
Abstract: 3C-(Si1-xC1-y)Gex+y ternary alloys were grown on 8.5° off axis 4H-SiC substrates by solid source molecular beam epitaxy in a temperature range between 750°C and 950°C. Energy dispersive X-ray (EDX) analysis revealed a decrease of the Ge incorporation versus substrate temperature. This effect is due to the fixed Si/Ge ratio during the epitaxial growth. The Ge distribution within the grown epitaxial layers was found to be nearly homogeneous. The investigations by atomic location by channeling enhanced microanalysis allowed the conclusion that Ge is located mainly at Si lattice sites.
Authors: Ariadne Andreadou, Jörg Pezoldt, Christian Förster, Efstathios K. Polychroniadis, M. Voelskow, Wolfgang Skorupa
Abstract: One of the main challenging tasks in the prospective technology is the buckling suppression of the 3C-SiC film due to the melting and solidification process and the stress relief as a consequence of the short time Si melting during the Flash Lamp Annealing. To overcome this effect and to stabilize a flat surface morphology an alternative i-FlASiC process was developed. This work refers to the influence of the layer stack modifications by doping and meltstop formation by ion implantation on the wafer buckling. The samples were studied by transmission electron microscopy, high resolution x-ray diffraction and infrared ellipsometry. The aim was to optimize the doping and flash lamp annealing conditions in relation to the i-FLASiC layer stack modification.
Authors: Jörg Pezoldt, Bernd Schröter, Volker Cimalla, Thomas Stauden, R. Goldhahn, Henry Romanus, Lothar Spieß
Authors: Elena Tschumak, Katja Tonisch, Jörg Pezoldt, Donat J. As
Abstract: Cubic gallium nitride epitaxial layers grown on differently carbonized silicon substrates were studied by high resolution X-ray diffraction. In the case of cubic GaN layers with equal layer thickness an improvement of the layer quality in terms of full width of the half maximum can be achieved by using higher carbonization temperatures. The higher crystalline quality led to an in¬crease of the residual stress in the grown layer. An increase in the thickness of the cubic Gallium Nitride allows to improve the crystallinity and to reduce the residual stress.
Authors: Francisco M. Morales, S.I. Molina, Daniel Araújo, Volker Cimalla, Jörg Pezoldt
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