Two-dimensional metallic broadband absorbers on a SiO(2)/Ag/Si substrate were experimentally studied. The absorptivity of such structure can be increased by tailoring the ratio of disk size to the unit cell area. The metallic disk exhibits a localized surface plasmon polariton (LSPP) mode for both TE and TM polarizations. A broadband thermal emitter can be realized because the LSPP mode is independent of the periodicities. By manipulating the ratios and disk sizes, a high-performance, wide-angle, polarization-independent dual band absorber was experimentally achieved. The results demonstrated a substantial flexibility in absorber designs for applications in thermal photovoltaics, sensors, and camouflage.

Normally-off p-GaN gated AlGaN/GaN high electron mobility transistors (HEMTs) were developed. Oxygen plasma treatment converted a low-resistive p-GaN layer in the access region to a high-resistive GaN (HR-GaN); that oxygen plasma treatment used an AlN layer as an oxygen diffusion barrier layer to prevent further oxidizing of the underlying AlGaN barrier layer, and to ensure that the low-resistive p-GaN layer in the access region was fully oxidized. Relative to conventional p-GaN gated AlGaN/GaN HEMTs, these AlGaN/GaN HEMTs with HR-GaN layers achieved a lower drain leakage current of 4.4 × 10 −7 mA/mm, a higher drain current on/off ratio of 3.9 × 10 9 , a lower on-state resistance of 17.1 •mm, and less current collapse. INDEX TERMS p-GaN gate HEMT, normally-off, high-resistivity GaN.

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In this study, the instability of the drain current on p-GaN gate AlGaN/GaN HEMT is observed. Contrary to the Schottky gate HEMT, Id-Vd curves of the p-GaN gate devices show dispersion in the saturation region under pulsed condition, which cannot be explained by trapping of electrics in the semiconductor. A model of trapping of holes in the p-GaN layer is proposed for this new observation.