Materials Science Forum Vol. 924

Abstract: This work is a contribution to the design of high-power DC-DC converters for future wind power applications by use of new semiconductors made of silicon carbide. First, the application is introduced, that is selected for high performance SiC devices. The design methodology is presented and validated with measurements of a physical prototype.

Abstract: This paper extends a previously presented SiC power module design philosophy to critical, higher-level components for increased system performance, namely the DC bussing and DC link capacitor design. The DC bussing is essential to connect the DC bulk capacitors to the high-speed power modules and it is imperative that low inductance is maintained while current carrying capability and temperature be maintained. Often, high frequency capacitors are added to systems to increase performance by compensating for extra stray inductance that the DC bussing can introduce. However, issues that may arise by doing such are presented and it is shown that the best solution is to optimize the DC bus structure rather than compensate for a poor design. Finally, the implemented bussing is shown and full power system results presented for the inverter stack-up design.

Abstract: In the past 20 years, SiC has gone through rapid development as a next-generation power semiconductor and the automotive market is considered one of its key potential application areas. Recently SiC power MOSFETs became commercially available from multiple manufacturers, attracting significant interest in the automotive industry for their benefits in the electric drivetrain system, including higher energy efficiency and opportunities of component weight and size reduction. Optimistic prediction of technology adoption in hybrid electric vehicles (HEV) also helped create a momentum for semiconductor suppliers to engage in the demonstration of SiC power modules for the traction inverter application. However, the performance expectations and reliability requirements of SiC-based power control units remain challenging for the cost-sensitive market. This paper will discuss the status and outlook of electrified powertrain systems, and outline the requirements for wide implementation of SiC power MOSFETs.

Abstract: Point defects in wide band gap semiconductors have recently shown outstanding potential for implementing room temperature quantum bits and single photon emitters. These atomic scale tools can be used in various quantum information processing, sensing, and imaging applications. Silicon vacancy related photoluminescence centers in 4H, 6H, and 15R-SiC are among the most studied quantum bits that possess a particular spin-3/2 ground and excited state. The microscopic structures of these defects have been recently identified as isolated negatively charged silicon vacancy defects at the symmetrically non-equivalent silicon sites in SiC. Relying on this identification, here we carry out high precision ab initio simulations on negatively charged silicon vacancies in 4H and 6H-SiC and calculate the most important magneto-optical data, such as the zero-phonon photoluminescence energies, the zero-field-splitting, and the hyperfine tensors for the nearest and farther nuclear spins.

Abstract: In this study, the influence of the gate-source voltage on the forward conduction properties of the body-diode in SiC-MOSFETs is demonstrated experimentally and analyzed by numerical simulations. Thereby, it can be figured out that the conduction properties of the body-diode strongly depend on the operational state of the MOS-capacitor. In depletion case, the current via the body-diode is dominant, whereby in accumulation and inversion mode the current mainly flows through the MOS-channel.

Abstract: Quantum technology is a field of significant interest that will benefit many applications including communications and sensing. SiC is a promising material for quantum applications such as quantum memories, due to point defects, specifically V_Si, in the material, which result in long spin coherence times. We have found that no V_Si are present in our epitaxially grown unintentionally and nitrogen-doped 4H-SiC with electron concentrations ranging from 10¹⁴ to 10¹⁸ cm^-3. We create these vacancies using electron irradiation, in concentrations from single defects to ensembles. To utilize the defect luminescence for realistic applications, we have fabricated the SiC into photonic crystal arrays. We present the processing steps required to create photonic crystal cavities in SiC and subsequent challenges.

Abstract: Functionalization of graphene/SiC dies by nitro-phenyl and its reduction to phenyl-amine is discussed. The graphene films were formed on a SiC substrate by the substrate surface thermal decomposition at 1800-2000°C. The functionalizing procedure included a two-step electrochemical process monitored by cyclic voltammetry and the die resistance. Functionalized graphene/SiC dies with applied antibody were blood sensitive and can be potentially applied to identify promptly types of the blood.

Abstract: The cubic polytype of SiC (3C-SiC) is the only one that can be grown on silicon substrate with the thickness required for targeted applications. Possibility to grow such layers has remained for a long period a real advantage in terms of scalability. Even the relatively narrow band-gap of 3C-SiC (2.3eV), which is often regarded as detrimental in comparison with other polytypes, can in fact be an advantage. However, the crystalline quality of 3C-SiC on silicon has to be improved in order to benefit from the intrinsic 3C-SiC properties. In this project new approaches for the reduction of defects will be used and new compliance substrates that can help to reduce the stress and the defect density at the same time will be explored. Numerical simulations will be applied to optimize growth conditions and reduce stress in the material. The structure of the final devices will be simulated using the appropriated numerical tools where new numerical model will be introduced to take into account the properties of the new material. Thanks to these simulations tools and the new material with low defect density, several devices that can work at high power and with low power consumption will be realized within the project.

Abstract: This paper demonstrates ion implanted lateral GaN MISFETs using double ion implantation technology, which enables us to form Si ion implanted source/drain regions in Mg ion implanted p-well fabricated on free-standing GaN substrates. Maximum drain current of 39 mA/mm and maximum transconductance of 4.5 mS/mm for GaN MISFET with a gate length of 2 μm at an estimated Mg surface concentration of 2.2 × 10¹⁸ cm^-3 were obtained. A threshold voltage was-0.5 V for the device. These results show that we successfully formed Si ion implanted n-type regions in the Mg ion-implanted layer and achieved innovative performance.

Abstract: Aluminum nitride (AlN) single crystal boules were grown by physical vapor transport (PVT). Diameter expansion during boule growth, without the introduction of low angle grain boundaries (LAGB) around the boule periphery, was confirmed by crossed polarizer imaging, synchrotron white beam x-ray topography (SWBXT), and synchrotron monochromatic beam x-ray topography (SMBXT). The densities of basal plane dislocations (BPD) and threading edge dislocations (TED) averaged from high-magnification topographs of five regions of a high-quality substrate were 0 cm^-2 and 992 cm^-2, respectively. Substrates fabricated from AlN boules possessed excellent surface finishes suitable for epitaxy.