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Expansion of single Shockley stacking faults (SSFs) during forward current operation is an important issue, because it decreases the reliability of 4H-SiC bipolar devices. In this paper, we propose a method for analyzing SSF dynamics based on free energy under current conduction, temperature, and resolved shear stress conditions. The driving force for dislocation dissociation reactions and formation of SSFs is incorporated into the free energy function, including chemical potential, stacking fault energy, crystallographic energy, gradient energy and elastic strain energy. The net energy gain of the chemical potential was calculated as a function of temperature and current conduction through use of the a TCAD device simulator based on the Boltzmann equation, Poisson equation and the current continuity equation concerning electron and hole distributions with self-consistency. It was confirmed that SSF dynamics can be simulated by the proposed method. It was also found that SSF formation can be attributed to quantum well variation in which electrons in n-type 4H–SiC enter SSF-induced quantum well states to lower the energy of the dislocation system.

We studied an advanced drift layer design which has an intermediate layer in mesa region for two-step-oxide field-plate MOSFET. The intermediate layer is formed by a high energy ion-implantation via source contact window. By TCAD simulation, it was confirmed the intermediate layer can decrease depletion layer capacitance in lower drain voltage. There was no change of breakdown voltage, and on-resistance (R ON A) increased slightly with increasing the implantation energy. An attractive effectiveness was obtained as gate-drain charge (Q GD ) decrease, and output charge and reverse recovery charge were slightly decreased. Evaluated performances showed that the Q GD and R ON Q GD were reduced by 14.1% and 10%, respectively. In power loss estimation of an assumed circuit, it was observed the newly designed FP-MOSFET can improve total power loss, especially in high-speed switching.

Expansion of a single Shockley stacking fault (SSF) during forward-current operation decreases the reliability of 4H-SiC bipolar devices. We propose a practical method for analyzing the defect evolution of SSF expansion based on free energy according to current density, temperature, and resolved shear stress conditions. The free energy includes chemical potential and elastic strain energy. Specifically, the chemical potential is related to the driving force for the formation of SSFs by temperature and current, and the elastic strain energy corresponds to the driving force for dislocations that form SSFs under the applied stress. It was confirmed that the proposed multiphysics method could well simulate SSF evolution when stress and current were applied. Furthermore, the results suggest that quantum well action, in which electrons in n-type 4H-SiC enter SSF-induced quantum well states to lower the energy of the dislocation system, affects the driving force of SSF formation.

Intracellular recording nanoscale electrode devices provide the advantages of a high spatial resolution and high sensitivity. However, the length of nanowire/nanotube-based nanoelectrodes is currently limited to10 μm long due to fabrication issues for high-aspect-ratio nanoelectrodes. The concept reported here can address the technological limitations by fabricating100 μm long nanoscale-tipped electrodes, which show intracellular recording capability.

Here we report vertical metal/silicon dioxide (SiO2) multiwalled microtube arrays as electrical and optical neuroprobes for “optogenetic”. Three-dimensional metal/SiO2-microtube arrays can be fabricated by vapor-liquid-solid (VLS) growth of silicon-wire, followed by the SiO2/metal depositions and the core-silicon etching. As the inside metal, we use iridium (Ir) with a low electrical electrolyte/electrode interfacial impedance in saline. An optical propagation through the Ir/SiO2-tube calculated by finite-difference time-domain (FDTD) method clearly indicates the effect of the inside Ir on the improved locality of light stimuli with the spot diameter of

In this paper, we present out-of-plane micro-scale diameter light guiding silicon dioxide tube arrays for use in optical stimulation of neurons. An optical propagation through the dioxide tube was calculated by using finite-difference time-domain (FDTD) simulation. Based on the calculated result, we designed and fabricated 3-µm-inner diameter 24-µm-height silicon dioxide tube arrays with the wall thickness of 0.5 µm, using selective vapor-liquid-solid (VLS) growth of silicon microwire, followed by microfabricating processes. The optical transmission capability of the fabricated tube was experimentally confirmed by using light of 470 nm, 525 nm, and 595 nm in wavelength.

We developed a batch-fabrication of nanoscale-tip silicon microprobe arrays for use in multipoint nanoscale investigations of cell/neuron in-vivo/in-vitro. Sharpened tips, less than 100nm diameter, can be formed at the tips of out-of-plane three-dimensional silicon microprobe (length ≫10?m) arrays, by silicon wet etching-based batch-process within only 1-3min, providing precisely controlled tip angles ranging from 15° to 50°. The penetration capability of the nanoscale-tip microprobes was demonstrated, using finite element modeling (FEM) simulations and penetration tests with a gelatin as tissue/cell.