65 research outputs found
on Vicinal Substrates
No full textS.47-74This chapter summarizes and explains the key factors in the development of 4H-SiC homoepitaxial growth and defect engineering. It will be shown that 4H-SiC homoepitaxy is a mature technology today, based on step-flow growth on vicinal substrates in a CVD process, providing epilayers of high structural quality. Still, extended defects like such as e.g. dislocations, stacking faults, and complexes thereof as well as point defects are relevant for device performance and device production yield. This chapter classifies defects, explains their nature and occurrence, provides adequate strategies for defect avoidance, and introduces pertinent characterization methods for such defects. Special attention is paid to the physical properties of point defects and their impact on minority carrier lifetimes
Versetzungsverhalten bei der Homoepitaxie von hexagonalem Siliziumkarbid (4H-SiC)
No full textIn dieser Dissertation wird das homoepitaktische Wachstum von 4H-Siliziumkarbidschichten auf unterschiedlich verkippten Substraten untersucht. Weitere Schwerpunkte liegen auf dem Verhalten der Versetzungen, speziell der Basalflächenversetzungen, bei der Epitaxie sowie auf der dotierungsinduzierten Fehlpassung zwischen Substrat und Schicht. Darüber hinaus wird das Charakterisierungsverfahren des defektselektiven Ätzens in einer Vergleichsstudie mittels Synchrotron-Röntgentopographie verifiziert
SiC in Power Electronics: Overcoming the obstacle of bipolar degradation
No full textSilicon Carbide (4H-SiC) is an ideal semiconductor for energy efficient power conversion modules. In recent years, unipolar SiC devices have been conquering the power electronics market. Contrarily, the commercialization of bipolar SiC devices has been hindered by the so-called bipolar degradation, which is closely related to the existence of certain structural defects within the active device volume. It will be shown how these critical defects can be avoided by optimizing the epitaxial growth of the active device volume. Furthermore, it will be proven that the absence of critical defects in the device prevents bipolar degradation. As the root cause of bipolar degradation is solved now, we also present remaining challenges for the commercialization of bipolar devices such as the cost reduction by enhancing the epitaxial growth rate and the improvement of device characteristics by increasing the minority carrier lifetime
Improvement of 4H-SiC material quality
No full textThe Fraunhofer IISB will introduce its activities in Silicon Carbide to the spintronic community with a special focus on its undertakings on material development and characterization. Our activities in materials development started about 10 years ago. We were improving the 4H-SiC homoepitaxial growth process in order to avoid extended defects, e.g. dislocations and stacking faults, in homoepitaxial layers. We were able to avoid device-killing defects like Basal Plane Dislocations in epilayers and explained these experimental results by appropriate models. Within the last years, the improvement of the minority carrier lifetime by reducing the point defect density has come into focus. Therefore, the influence of epigrowth parameters like, e.g. gas mixing and growth temperature, on the point defect density and carrier lifetime are investigated by using Deep Level Transient Spectroscopy (DLTS) and microwave-detected photoconductivity decay (µ-PCD). Our recent developments target on the reduction of the carbon vacancy, which is known as a lifetime-killing defect. The experimental work is completed by implementing models regarding the point defect generation / annihilation as well as the carrier lifetime measurements. Besides the materials development, the Fraunhofer IISB has been manufacturing SiC electronic devices for more than 20 years. We are producing power electronic as well as optoelectronic SiC devices in small series or prototype fabrication. The process line could be used also to fabricate spintronic prototype devices. In our presentation, we will show and discuss ou r recent advances in materials development and characterization as well as introduce the device processing
Modellierung der Minoritätsladungsträgerlebensdauer in n-4H-SiC Epitaxieschichten
No full textS.341-344We present an extended model for the simulation of the effective minority carrier lifetime in 4H-SiC epiwafers after optical excitation. This multilayer model uses measured values (doping profile, point defect concentration, capture cross sections for electrons and epilayer thickness) as input parameters. The bulk lifetime and the diffusion constant are calculated from the actual time dependent excess carrier profiles, resulting in more realistic transients having different decay regimes than in other models. This enables a better understanding of optical lifetime measurements
HCl assisted growth of thick 4H-SiC epilayers for bipolar devices
No full textS.210-213The addition of hydrogen chloride (HCl) to our conventional CVD process allows for high growth rates up to 50 mm/h while maintaining the step-flow growth mode. Such epilayers exhibit quite low total concentrations of point defects less than 2 x 1013 cm-3. But, the HCl addition shows an ambivalent influence on the concentration of the lifetime killer defect Z1/2. For low growth rates, the Z1/2 concentration slightly decreases with increasing HCl addition. For higher growth rates, the Z1/2 concentration increases with increasing HCl addition
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