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The growth of AlGaN∕GaN heterostructure on Si (001) substrates by molecular-beam epitaxy using ammonia as nitrogen precursor is reported. The structural, optical, and electrical properties of such heterostructures are assessed. It is shown that a two-dimensional electron gas is formed at the Al0.23Ga0.77N∕GaN interface. This type of heterostructure exhibits a sheet carrier density of 4.2×1012cm−2 with a mobility of 730cm2∕Vs at room temperature. Preliminary results concerning high-electron-mobility-transistor static characteristics are presented.

International audienceA 60 GHz cavity-backed antenna array integrated on high-resistivity silicon is demonstrated. The antenna design makes use of Through-Silicon-Vias (TSV), silicon micromachining, and wafer-to-wafer bonding to meet the bandwidth and radiation gain requirements for short-range multi-Gbps communications. The fabrication process is presented. Simulated and experimental results show that the antenna element covers easily the 57–66 GHz standard band with good impedance matching and more than 5 dBi of gain. Several fixed-beam four-element antenna arrays demonstrate the capabilities for beam-steering across a range up to ±60°

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