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Performance Enhancement of Gate-Annealed AlGaN/GaN HEMTs
Somna S. Mahajan,Amit Malik,Robert Laishram,Seema Vinayak 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.5
The electrical performances of unannealed and post gate-annealed AlGaN/GaN High Electron Mobility Transistors (HEMTs) were analyzed. A considerable improvement in HEMT parameters such as the drain source current (Ids), transconductance (gm), gate reverse leakage current (Ir) and off-state breakdown voltage (Vboff ) were observed in optimally post gate-annealed HEMT devices. The improvement in the device parameters was correlated with the combined effects of an improved electron mobility and the removal of interface inhomogenity in the gated region as a result of gate annealing. The gate-annealed HEMTs, thus, delivered an output power of 5 W/mm at the S and the C bands.
Two-Dimensional Excitonic Photoluminescence in Graphene on a Cu Surface
Park, Youngsin,Kim, Yooseok,Myung, Chang Woo,Taylor, Robert Anthony,Chan, Christopher C. S.,Reid, Benjamin P. L.,Puchtler, Tim J.,Nicholas, Robin J.,Singh, Laishram Tomba,Lee, Geunsik,Hwang, Chan-Cuk American Chemical Society 2017 ACS NANO Vol.11 No.3
<P>Despite having outstanding electrical properties, graphene is unsuitable for optical devices because of its zero band gap. Here, we report two-dimensional excitonic photoluminescence (PL) from graphene grown on a Cu(111) surface, which shows an unexpected and remarkably sharp strong emission near 3.16 eV (full width at half-maximum <= 3 meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue shift, displaying the characteristic negative thermal coefficient of graphene. The observed PL originates from the significantly suppressed dispersion of excited electrons, in graphene caused by hybridization of graphene pi and Cu d orbitals of the first and second Cu layers at a shifted saddle point 0.525(M+K) of the Brillouin zone. This finding provides a pathway to engineering optoelectronic graphene devices, while maintaining the outstanding electrical properties of graphene.</P>