There are continuing rapid developments in vertical geometry Ga2O3 for high voltage switching applications. Ga2O3 is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping and the availability of large diameter, relatively inexpensive substrates. These include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors and advanced power management and control electronics. There are already cases where the performance exceeds the theoretical values for SiC. Existing Si, SiC (vertical devices), and heteroepitaxial GaN (lateral devices) enjoy tremendous advantages in terms of process maturity, an advantage that is especially true for Si, where the ability to precisely process the material has resulted in devices such as super-junctions that surpass the unipolar “limit”. Continued development of low defect substrates, optimized epi growth and surface treatments and improved device design and processing methods for Ga2O3 are still required to push the experimental results closer to their theoretical values. Even 3 μm epi layers with doping concentration of 1016 cm-3 should have a theoretical breakdown voltage of ~1800V. The actual experimental value of VB is currently well below the theoretical predictions. Thermal management is a key issue in Ga2O3 power devices for practical high current devices and initial studies have appeared on both the experimental and theoretical fronts. We summarize progress in edge termination design, temperature measurement using thermoreflectance-based thermography to measure the thermal rise and decay of the active diodes, failure under forward bias and development of large current (up to 130A) arrays.
Semiconductor nanowires such as zinc oxide nanowires are projected to be the next generation materials for nanoscale
sensors and actuators. They also serve as ideal systems for studying material behavior at the small scale. In this paper,
we report experimental results on the mechanical properties of zinc oxide nanowires. We have designed a MEMS
(microelectromechanical systems) test-bed for mechanical characterization of nanowires and use a microscale version of
pick-and-place as a generic specimen preparation and manipulation technique. We performed experiments on zinc oxide
nanowires inside a scanning electron microscope (SEM) and estimated the Young's modulus to be approximately 21
GPa and the fracture strain to vary from 5 % to 15 %. We attribute the difference in mechanical properties of the
nanowires from bulk properties to several factors such as lower number of defects, charge redistribution at the atomic
scale and surface effects.
Semiconductor nanowires such as zinc oxide nanowires are projected to be the next generation materials for nanoscale
sensors and actuators. They also serve as ideal systems for studying material behavior at the small scale. In this paper,
we report experimental results on the mechanical properties of zinc oxide nanowires. We have designed a MEMS
(microelectromechanical systems) test-bed for mechanical characterization of nanowires and use a microscale version of
pick-and-place as a generic specimen preparation and manipulation technique. We performed experiments on zinc oxide
nanowires inside a scanning electron microscope (SEM) and estimated the Young's modulus to be approximately 21
GPa and the fracture strain to vary from 5% to 15%. We attribute the difference in mechanical properties of the
nanowires from bulk properties to several factors such as lower number of defects, charge redistribution at the atomic
scale and surface effects.
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