An ultra-portable, self-contained point-of-care nucleic acid amplification test for diagnosis of active COVID-19 infection.

There is currently a high level of demand for rapid COVID-19 tests, that can detect the onset of the disease at point of care settings. We have developed an ultra-portable, self-contained, point-of-care nucleic acid amplification test for diagnosis of active COVID-19 infection, based on the principle of loop mediated isothermal amplification (LAMP). The LAMP assay is 100% sensitive and specific to detect a minimum of 300 RNA copies/reaction of SARS-CoV-2. All of the required sample transportation, lysing and amplification steps are performed in a standalone disposable cartridge, which is controlled by a battery operated, pocket size (6x9x4cm3) unit. The test is easy to operate and does not require skilled personnel. The total time from sample to answer is approximately 35 min; a colorimetric readout indicates positive or negative results. This portable diagnostic platform has significant potential for rapid and effective testing in community settings. This will accelerate clinical decision making, in terms of effective triage and timely therapeutic and infection control interventions.

Electron beam-induced crystallization of Al2O3 gate layer on ß-Ga2O3 MOS capacitors.

Electron irradiation was observed to induce crystallization of amorphous Al2O3 films grown by atomic layer deposition on ß-Ga2O3 substrates. Growth of large, strongly oriented crystalline γ-Al2O3 regions was induced using conventional-mode transmission electron microscopy (TEM) and observed to propagate outward from the interface as well as from the previously crystallized Al2O3. A few nm of epitaxial Al2O3 was already visible at the beginning of the crystallization front propagation. The phenomenon is not explained by electron beam-induced heating, which amounted to less than 1 K at all times. Direct measurement of the beam current permitted quantitative correlation between electron dose rates and crystallization rates. Enlarging the electron beam to reduce current density was found to slow the propagation of the crystallization front. Furthermore, a factor of 4 smaller electron dose was required for a given rate using 100 keV electrons as compared to 200 keV, indicating that crystallization is driven by ionization-induced atomic rearrangement within the gate layer. Lattice spacing between the oxygen sub-lattices of ß-Ga2O3 and γ-Al2O3 are favorable for the nucleation of crystallites at the interface. Multivariate statistical analysis of electron energy loss spectroscopy (EELS) data also showed evidence of diffusion between Al and Ga in the substrates and gate oxides, respectively. These structural transformations at the semiconductor-insulator interface are expected to influence the device electrical behavior and are relevant to the continued refinement of ß-Ga2O3 device technology.

Thermal characterization of gallium oxide Schottky barrier diodes.

The higher critical electric field of ß-gallium oxide (Ga2O3) gives promise to the development of next generation power electronic devices with improved size, weight, power, and efficiency over current state-of-the-art wide bandgap devices based on 4H-silicon carbide (SiC) and gallium nitride (GaN). However, it is expected that Ga2O3 devices will encounter serious thermal issues due to the poor thermal conductivity of the material. In this work, self-heating in Ga2O3 Schottky barrier diodes under different regimes of the diode operation was investigated using diverse optical thermography techniques including thermoreflectance thermal imaging, micro-Raman thermography, and infrared thermal microscopy. 3D coupled electro-thermal modeling was used to validate experimental results and to understand the mechanism of heat generation for the diode structures. Measured top-side and cross-sectional temperature fields suggest that device and circuit engineers should account for the concentrated heat generation that occurs near the anode/Ga2O3 interface and/or the lightly doped drift layer under both forward and high voltage reverse bias conditions. Results of this study suggest that electro-thermal co-design techniques and top-side thermal management solutions are necessary to exploit the full potential of the Ga2O3 material system.