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Localized micro/nano-electroporation (MEP/NEP) shows tremendous potential in cell transfection with high cell viability, precise dose control, and good transfection efficacy. In MEP/NEP, micro or nanochannels are used to tailor the electric field distribution. Cells are positioned tightly by a micron or nanochannel, and the cargoes are delivered into the cell via the channel by electrophoresis (EP). Such confined geometries with micro and nanochannels are also widely used in sorting, isolation, and condensing of biomolecules and cells. Theoretical studies on the electrokinetic phenomena in these applications have been well established. However, for MEP/NEP applications, electrokinetic phenomena and their impact on the cell transfection efficiency and cell survival rate have not been studied comprehensively. In this work, we reveal the coupling between electric field, Joule heating, electroosmosis (EO), and EP in MEP/NEP at different channel sizes. A microfluidic biochip is used to investigate the electrokinetic phenomena in MEP/NEP on a single cell level. Bubble formation is observed at a threshold voltage due to Joule heating. The bubble is pushed to the cargo side due to EO and grows at the outlet of the nanochannel. As the voltage increases, the cargo transport efficiency decreases due to more intense EO, particularly for plasmid DNAs (3.5 kbp) with a low EP mobility. An 'electroporation zone' is defined for NEP/MEP systems with different channel sizes to avoid bubble formation and excessive EO velocity that may reduce the cargo delivery efficiency. [ABSTRACT FROM AUTHOR]

Devices based on gallium nitride (GaN) have great potential for high power switching applications due to the high breakdown field and high electron mobility. In this work, we present a vertical GaN-on-GaN PN power diode using high dielectric constant material, BaTiO3, for electrical field management and high breakdown voltages, in together with an optimized guard-ring and field plate design. Numerical simulation shows that with high-k dielectrics implemented, the peak electrical field at the PN interface is mitigated from 3.5 to 3.1 MV/cm under a reverse bias of −9.05 kV. The device design with BaTiO3 shows a breakdown voltage of 9.65 kV or about 600 V improvement. The fabricated diodes with a 57 μm thick drift layer demonstrate a breakdown voltage of 7.86 kV on a bulk GaN substrate. The device has an on-resistance of 2.8 mΩ cm 2 and a Baliga figure of merit of 22 GW/ cm 2 . [ABSTRACT FROM AUTHOR]

The etching of epitaxially grown perovskite oxide BaSnO3 (BSO) and BaTiO3 (BTO) thin films is studied using Cl-based (BCl3/Ar) and F-based (CF4/Ar) plasma chemistries in an inductively coupled plasma reactive ion etching (ICP-RIE) system for the development of field effect transistors (FETs). It is found that the BCl3/Ar process has a time-independent and a higher etch rate and creates a smooth etched surface, while the etch rate of BSO and BTO in CF4/Ar plasma decreases with the etching time duration. For the BCl3/Ar etching process, the etch rate increases with both ion density and ion energy, suggesting the combination of chemical plasma etching and physical ion sputtering mechanisms. Using the Cl-based etching process, BaSnO3 and BaTiO3 heterojunction FETs are developed. The devices with a gate length of 1.5 μm have a saturation current density of 287.6 mA/mm, a maximum transconductance of gm = 91.3 mS/mm, an FET mobility of 45.3 cm2/V s, and a threshold voltage of −1.75 V. The etching processes developed in this work will enable further development of perovskite oxide heterostructure electronic devices. [ABSTRACT FROM AUTHOR]

BaSnO3, a high mobility perovskite oxide, is an attractive material for oxide-based electronic devices. However, in addition to low-field mobility, high-field transport properties such as the saturation velocity of carriers play a major role in determining the device performance. We report on the experimental measurement of the electron saturation velocity in La-doped BaSnO3 thin films for a range of doping densities. The predicted saturation velocities based on a simple LO-phonon emission mode, using an effective LO phonon energy of 120 meV show good agreement with the measurements of velocity saturation in La-doped BaSnO3 films. Density-dependent saturation velocity in the range of 1.8 × 107 cm/s reducing to 2 × 106 cm/s is predicted for δ-doped BaSnO3 channels with carrier densities ranging from 1013 cm−2 to 2 × 1014 cm−2, respectively. These results are expected to aid the informed design of BaSnO3 as an active material for high-charge density electronic transistors. [ABSTRACT FROM AUTHOR]