Vertical GaN Schottky barrier diodes (SBDs) were fabricated on freestanding GaN substrates with low dislocation density. High quality n-GaN drift-layer with an electron mobility of 930 cm2 V-1 s-1 was obtained by optimizing the growth conditions by reducing the intensity of yellow luminescence using conventional photoluminescence measurements. The specific on-resistance (RonA) and the breakdown voltage (VB) of the SBDs were 0.71 mΩ cm2 and over 1100 V, respectively. The figure of merit (VB2/RonA) was 1.7 GW/cm2, which is the highest value among previously reported SBDs for both GaN and SiC.
We observed that Faraday waves are parametrically generated on a free surface of superfluid 4He when a sample cell is vibrated vertically. Standing-wave patterns appear on the surface, and their frequencies are one-half the driving frequency. We observed clear threshold amplitudes of the vibration for the instability. The difference in the threshold between the superfluid and the normal fluid is explained by a wall damping.
Novel vertical heterojunction field-effect transistors (VHFETs) with re-grown AlGaN/GaN two-dimensional electron gas (2DEG) channels on free-standing GaN substrates have been developed. The VHFETs exhibited a specific on-resistance (RonA) of 7.6 mΩ cm2 at a threshold voltage (VTH) of -1.1 V and a breakdown voltage (VB) of 672 V. The breakdown voltage and the figure of merit (VB2/RonA) are the highest among those of the GaN-based vertical transistors ever reported. It was demonstrated that the threshold voltage can be controlled by the thickness of AlGaN layers and a normally-off operation was achieved with a 10-nm-thick Al0.2Ga0.8N layer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.