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Heavily Sn-doped films of α -Ga2O3 were grown by halide vapor phase epitaxy (HVPE) on basal plane c-sapphire and on (10-12) r-sapphire substrates with and without α -Cr2O3 thin buffers prepared by magnetron sputtering and annealing in air at 500 °C for 3 h. For both substrate orientations, the use of α -Cr2O3 buffers led to three major effects. The first was a substantial decrease of the half-width of the symmetric and asymmetric x-ray reflections. The second was an order of magnitude decrease of the net donor concentration produced by flowing the same amounts of Sn into the reactor. Third, there was a reduction in the concentration of the major electron trap in the films near E c âˆ' 1 eV by more than a factor of two. These results show the major influence of sapphire substrate orientation on the electrical and structural properties of α -Ga2O3 grown by HVPE. [ABSTRACT FROM AUTHOR]

This report details the use of a Si Metal Oxide Semiconductor Field Effect Transistor (MOSFET) with the gate connected to a disposable antibody-functionalized electrode for the detection of β-2-transferrin (β2T) as a marker of cerebral spinal fluid (CSF). Through the design of a Si based PCB the need for GaN High Electron Mobility Transistors has been mitigated and brings the cost of production for commercial application closer to realization. Through the use of a double pulse method to the test electrode and the drain of the Si MOSFET, ionicity of the test solution is no longer a concern as a double layer is produced and perturbed on the test electrode giving rise to current changes related to the concentration of the biomarker. Additionally, the PCB provides connections for an oscilloscope readout or an onboard display entirely removing the need for any expensive semiconductor parameter analyzers. Clinically, the cutoff for β2T as indicator of CSF leakage has traditionally been limited to ~2 μg/mL and takes several hours; with this newly designed board, CSF was detected at levels from 0.1 ng/mL to 100 μg/mL within 5 minutes, greatly improving the detection limits and feedback time for medical professionals. [ABSTRACT FROM AUTHOR]

We report the chemical etching characteristics of Ga-face and N-face GaN using phosphoric acid (H3PO4) or potassium hydroxide (KOH) solutions. Hexagonal pyramids, which consisted of the {10-1-1} planes, were present on the N-face after KOH (2M, 100°C) etching. By contrast, using the H3PO4 (85 wt.%, 100°C) solutions, the nitrogen surface of GaN showed dodecagonal pyramids. Dodecagonal and hexagonal pyramids repeatedly appear on the etched surface when using the H3PO4 or KOH solutions, respectively. A low concentration of H3PO4 (H3PO4 : deionized water = 1:32, 1:64) produced a roughened surface with coexistence of dodecagonal and hexagonal pyramids. The photoluminescence (PL) intensity of the etched surfaces significantly increased due to multiple scattering events compared to the non-etched surface. Thus, the etching techniques developed in this study were shown to improve the light extraction efficiency of light emitting diodes (LEDs), avoiding the damage to the GaN typically created by plasma etching methods. [ABSTRACT FROM AUTHOR]

We studied the effects of photo electrochemical (PEC) etching by using various concentrations (1,2, and 4 M) of KOH solutions on both Gaand N-face GaN layers on sapphire substrates. The Ga-face was chemically stable for KOH solutions, while by sharp contrast the KOI-1 could etch the N-face, where the 6-fold symmetry was observed after the PEC etching. Surface texturing of GaN-based light emitting diodes and solar cells by KOH-based PEC etch could enhance the efficiency of GaN-based photonic devices by increasing the number of the scattering events and randomly changing the angles of the light. [ABSTRACT FROM AUTHOR]