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20 results on '"Czap, Heiko"'

1. Influence of Different Surface Morphologies on the Performance of High Voltage, Low Resistance Diamond Schottky Diodes

Author

Reinke, Philipp, Benkhelifa, Fouad, Kirste, Lutz, Czap, Heiko, Pinti, Lucas, Zürbig, Verena, Cimalla, Volker, Nebel, Christoph, and Ambacher, Oliver

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science, Physics - Instrumentation and Detectors
Abstract

Vertical diamond Schottky diodes with blocking voltages $V_{\text{BD}} > 2.4 \text{ kV}$ and on-resistances $R_{\text{On}} < 400 \text{ m}\Omega \text{cm}^{2}$ were fabricated on homoepitaxially grown diamond layers with different surface morphologies. The morphology (smooth as-grown, hillock-rich, polished) influences the Schottky barrier, the carrier transport properties, and consequently the device performance. The smooth as-grown sample exhibited a low reverse current density $J_{\text{Rev}} < 10^{-4} \text{ A}/\text{cm}^{2}$ for reverse voltages up to $2.2 \text{ kV}$. The hillock-rich sample blocked similar voltages with a slight increase in the reverse current density ($J_{\text{Rev}} < 10^{-3} \text{ A}/\text{cm}^{2}$). The calculated 1D-breakdown field, however, was reduced by $30 \text{ } \%$, indicating a field enhancement induced by the inhomogeneous surface. The polished sample demonstrated a similar breakdown voltage and reverse current density as the smooth as-grown sample, suggesting that a polished surface can be suitable for device fabrication. However, a statistical analysis of several diodes of each sample showed the importance of the substrate quality: A high density of defects both reduces the feasible device area and increases the reverse current density. In forward direction, the hillock-rich sample exhibited a secondary Schottky barrier, which could be fitted with a modified thermionic emission model employing the Lambert W-function. Both polished and smooth sample showed nearly ideal thermionic emission with ideality factors $1.08$ and $1.03$, respectively. Compared with literature, all three diodes exhibit an improved Baliga Figure of Merit for diamond Schottky diodes with $V_{\text{BD}} > 2 \text{ kV}$., Comment: Accepted April 20, 2020

Published
2020
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16. Flexible and Scalable Heterogeneous Integration of GaN HEMTs on Si‐CMOS by Micro‐Transfer‐Printing.

Author

Lerner, Ralf, Eisenbrandt, Stefan, Fischer, Frank, Fecioru, Alin, Trindade, António Jośe, Bonafede, Salvatore, Bower, Christopher, Waltereit, Patrick, Reiner, Richard, and Czap, Heiko

Subjects
GALLIUM nitride, MODULATION-doped field-effect transistors, COMPLEMENTARY metal oxide semiconductors, EXPERIMENTAL design, POWER electronics, BREAKDOWN voltage
Abstract

Tomorrow's power electronic systems require cost‐saving and more efficient power conversion solutions. The heterogeneous integration of GaN‐based high electron mobility transistors (HEMTs) together with silicon CMOS by micro‐Transfer‐Printing could be a key technology for this. It enables the integration of highly integrated mature CMOS logic functionality with fast GaN HEMT output drivers with very low on‐state and switching losses. The scalability by design measures of the printed HEMT is investigated in terms of drain‐to‐gate spacing and channel width defining breakdown voltage and area‐related parameters like on‐resistance. The design flexibility of the micro‐Transfer‐Printing by printing the HEMTs on top of the CMOS devices without restrictive design rule limits is investigated by CMOS DC parameter comparison and thermal TCAD Design Of Experiment (DOE) study. No electrical or thermal functional limitation of printing the HEMTs directly on top of the CMOS dielectric layer stack was found. This enables the usage of the isolation capabilities of the CMOS dielectric layer stack to enhance the HEMT breakdown voltage. [ABSTRACT FROM AUTHOR]

Published
2018
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19. Vertical Buffer Leakage and Temperature Effects on the Breakdown Performance of GaN/AlGaN HEMTs on Si Substrate

Author

Benkhelifa, Fouad, Muller, Stefan, Polyakov, Vladimir M., Breuer, Steffen, Czap, Heiko, Manz, Christian, Mikulla, Michael, and Ambacher, Oliver

Abstract

The epitaxial growth of a GaN/AlGaN HEMTs epi-structure based on a carbon doped superlattice buffer has been optimized for achieving a highly isolated buffer, and transistors with high breakdown voltages and low leakage currents. The 10 mm gate periphery normally-on HEMTs demonstrate a drain-source leakage current lower than 0.4 uA/mm at 600 V drain bias. Furthermore, the breakdown voltage performance of the HEMT is not altered at 600 V bias when the measurement is performed with the substrate being grounded. The isolation blocking voltage of the epi-structure reaches 840 V for a corresponding leakage current density of 10 uA/mm2. We highlight low buffer vertical isolation degradation at high temperature (150degC) and that the decrease in HEMT's breakdown voltage performance is not due to the vertical buffer leakage when increasing the substrate temperature.

Published
2015

20. Mechanical and electrical properties of plasma and thermal atomic layer deposited Al2O3 films on GaAs and Si.

Author

Sah, Ram Ekwal, Driad, Rachid, Bernhardt, Frank, Kirste, Lutz, Leancu, Crenguta-Columbina, Czap, Heiko, Benkhelifa, Fouad, Mikulla, Michael, and Ambacher, Oliver

Subjects
ALUMINUM oxide films, GALLIUM arsenide, PLASMA gases, ATOMIC layer deposition, ELECTRIC properties of aluminum oxide, ALUMINUM oxide, MECHANICAL properties of metals, THERMAL expansion, THERMAL properties
Abstract

Mechanical and electrical properties of Al2O3 films are compared for plasma-assisted atomic layer deposition (ALD) and thermal ALD on two substrates, GaAs and Si, of different thermal expansion coefficient. Films with stable chemical structure and mechanical residual stress could be produced by both techniques without inducing any damage to sensitive multiquantum-well structures. However, the as-deposited residual stress in the plasma ALD Al2O3 films is lower and decreases, while that in the thermal ALD films increases with the deposition temperature. Moreover, the stress hysteresis observed upon thermal cycles is much lower for the plasma ALD films compared to that for the thermal ALD films. The biaxial elastic modulus (BEM or stiffness parameter) increases with the deposition temperature for both ALD films, being higher for the plasma ALD than that for the thermal ALD at a given temperature. The higher BEM is reflected in better electrical properties of the films. Thus, the leakage current of metal-oxide-semiconductor capacitors with the plasma ALD-Al2O3 film is three orders of magnitude lower and the breakdown voltage 20% higher than that of the capacitors with the thermal ALD film. [ABSTRACT FROM AUTHOR]

Published
2013
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