Si metal oxide semiconductor field effect transistors (MOSFETs) with the gate lengths of 120-300 nm have been studied as room temperature plasma wave detectors of 0.7 THz electromagnetic radiation. In agreement with the plasma wave detection theory, the response was found to depend on the gate length and the gate bias. The obtained values of responsivity (<= 200 V/W) and noise equivalent power (>= 10(-10) W/Hz(0.5)) demonstrate the potential of Si MOSFETs as sensitive detectors of terahertz radiation. (c) 2006 American Institute of Physics

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PACS 72.80. Ey, 74.25.Fy, 74.90.+n In this report we present our recent investigation on the co-existence of superconducting and semiconducting properties in InN grown on sapphire (0001) by the use of MBE and MOCVD methods. Magnetotransport measurements were done using InN with a carrier density e n from 4 × 10 17 to 4 × 10 20 cm -3 in the temperature range from 20 mK to 2 K and under the magnetic field (B) up to 23 T. As a result, even InN samples with e n as low as 4 × 10 17 cm -3 showed superconductivity at T c = 0.12 K. The vortex solid of InN was melted by thermal fluctuation and by the external field, similarly to the observation in layered high c T superconductors. By the Shubnikov -de Haas oscillation measurements it was found that there were substantial carriers spread in the a -b plane which played an essential role not only for the occurrence of the superconductivity, but also for many other unexpected electronic and optical properties of InN. Based on these results we present a possible mechanism of superconductivity in terms of the interaction between the conduction electrons and the fixed d-electrons of In atoms spread in the a -b plane.

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Room temperature electron mobility (μ) in nanometer Si metal-oxide-semiconductor field-effect transistors (MOSFETs) with gate length (LG) down to 30 nm was determined by the magnetoresistance method. A decrease of μ with the decrease of LG was observed. Monte Carlo simulations of electron transport in nanometer MOSFETs were carried out for realistic devices as a function of LG. The dependence with LG and electron concentration of simulated mobility and transmission coefficient agree with experimental data. An analysis of scattering events and time of flight gives evidence of the presence of ballistic motion in the investigated structures and proves its influence on mobility degradation in short transistors. The results give arguments that interpretation of the magnetoresistance coefficient as the square of the mobility is valid also in the case of quasiballistic electron transport.

We report on the low frequency ͓1/ f and generation-recombination ͑GR͔͒ noise in InAlAs/InGaAs modulation doped field effect transistors with a 50-nm gate length. The characteristic capture and emission times of the GR noise depended on the gate voltage. Measurements of the noise as a function of the gate voltage showed that the gate leakage current, contacts, and ungated sections of the channel did not contribute to the 1 / f noise. The gate voltage dependence of the 1 / f noise agreed well with the model of number of carriers fluctuations as a source of the 1 / f noise. An effective density of traps responsible for the 1 / f noise was found to be D eff Ϸ 2.7ϫ 10 12 cm −2 eV −1 .

We have fabricated and characterized blue (Ga,In)N/GaN multiple quantum well light emitting diodes grown on a Si(110) substrate by molecular beam epitaxy. For a 20 mA current, we have found that the operating voltage and the series resistance are as low as 3.5 V and 17 Ω, respectively. A maximum light output power of 72 µW is obtained as measured on the wafer. These characteristics are almost identical to those obtained on a reference sample grown on the commonly used Si(111) orientation.

High electron mobility field effect transistors were fabricated on AlGaN∕GaN heterostructures and their magnetoresistance was measured at 4.2K up to 10T with simultaneous modulation of the gate potential. Low and high magnetic field data were used to determine the electron mobility (μ) and concentration (n), respectively, in the gated part of the transistor channel. With these measurements we present a method to determine μ and n under the gate of a transistor, which does not require knowledge of the transistor gate length, access resistance, threshold voltage, or capacitance. We discuss applications of this method for nanometer and ballistic transistors.