How to achieve high mobility thin film transistors by direct deposition of silicon using 13.56 MHz RF PECVD?

CMOS nanocrystalline silicon thin film transistors with high field effect mobility are reported. The transistors were directly deposited by radio-frequency plasma enhanced chemical vapor deposition at 150°C The transistors show maximum field effect mobility of 450 cm2/V-s for electrons and 100 cm2/V-s for holes at room temperature. We attribute the high mobilities to a reduction of the oxygen content, which acts as an accidental donor. Indeed, secondary ion mass spectrometry measurements show that the impurity concentration in the nanocrystalline Si layer is comparable to, or lower than, the defect density in the material, which is already low thanks to hydrogen passivation.

Thermal evolution of Er silicate thin films grown by rf magnetron sputtering

Stoichiometric Er silicate thin films, monosilicate (Er2SiO 5) and disilicate (Er2Si2O7), have been grown on c-Si substrates by rf magnetron sputtering. The influence of annealing temperature in the range 1000-1200 °C in oxidizing ambient (O 2) on the structural and optical properties has been studied. In spite of the known reactivity of rare earth silicates towards silicon, Rutherford backscattering spectrometry shows that undesired chemical reactions between the film and the substrate can be strongly limited by using rapid thermal treatments. Monosilicate and disilicate films crystallize at 1100 and 1200 °C, respectively, as shown by x-ray diffraction analysis; the crystalline structures have been identified in both cases. Moreover, photoluminescence (PL) measurements have demonstrated that the highest PL intensity is obtained for Er2Si2O7 film annealed at 1200 °C. In fact, this treatment allows us to reduce the defect density in the film, in particular by saturating oxygen vacancies, as also confirmed by the increase of the lifetime of the PL signal. © 2008 IOP Publishing Ltd.

Anisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAlO3 and MgO substrates. Two orientations of the magnetic field with respect to the electrical current have been studied: (i) magnetic field in the plane of the film and parallel to the electrical current, and (ii) magnetic field perpendicular to the plane of the film. The film grown on LaAlO 3 is characterised by an unusual magnetoresistive behaviour when the magnetic field is applied perpendicular to the film plane: the appearance of two bumps in the field dependence of the resistance is shown to be related to the occurrence of anisotropic magnetoresistive effects in manganate films. © 2004 Elsevier B.V. All rights reserved.

High power, low-jitter encoded picosecond pulse generation using an rf-locked self-q-switched multicontact GaAs/GaAlAs diode laser

The RF locking of a self-Q-switching diode laser is shown to reduce the jitter of a 2.48 GHz train of 1 W peak power picosecond pulses to less than 300 fs. By using direct modulation of the loss in the Q-switched laser, direct encoding of data has been achieved at rates in excess of 2 Gbit/s.

Sub-kHz RF electrical linewidth from a 10GHz passively mode-locked quantum-dot laser diode

A packaged 10GHz monolithic two-section quantum-dot mode-locked laser is presented, with record narrow 500Hz RF electrical linewidth for passive mode-locking. Single sideband noise spectra show 147fs integrated timing jitter over the 4MHz-80MHz frequency range. © 2009 Optical Society of America.

High performance uncooled 1.3μm VCSELs for RF-over-fiber applications

Uncooled directly-modulated 1.3μm VCSELs are shown to exhibit dynamic range, linearity and noise performance required for wireless LAN applications. A multimode fiber based WLAN 802.11b system shows performances comparable to systems with state-of-the-art DFB lasers. © 2005 Optical Society of America.

High performance uncooled 1.3μm VCSELs for RF-over-fiber applications

Uncooled directly-modulated 1.3μm VCSELs are shown to exhibit dynamic range, linearity and noise performance required for wireless LAN applications. A multimode fiber based WLAN 802.11b system shows performances comparable to systems with state-of-the-art DFB lasers. © 2005 Optical Society of America.

InN材料的RF-MBE生长及其禁带宽度研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

A Fully Integrated 900-MHz Passive RFID Transponder Front End With Novel Zero-Threshold RF-DC Rectifier

This paper presents a fully integrated CMOS analog front end for a passive 900-MHz radio-frequency identification (RFID) transponder. The power supply in this front end is generated from the received RF electromagnetic energy by using an RF-dc voltage rectifier. In order to improve the compatibility with standard CMOS technology, Schottky diodes in conventional RF-dc rectifiers are replaced by diode-connected MOS transistors with zero threshold. Meanwhile, theoretical analyses for the proposed rectifier are provided and verified by both simulation and measurement results. The design considerations of the pulsewidth-modulation (PWM) demodulator and the backscatter modulator in the front end are also discussed for low-power applications. The proposed front end is implemented in a 0.35-mu m 2P4M CMOS technology. The whole chip occupies a die area of 490 x 780 mu m(2) and consumes only 2.1 mu W in reading mode under a self-generated 1.5-V supply voltage. The measurement results show that the proposed rectifier can properly operate with a - 14.7-dBm input RF power at a power conversion efficiency of 13.0%. In the proposed RFID applications, this sensitivity corresponds to 10.88-m communication distance at 4-W equivalent isotropically radiated power from a reader base station.

Epitaxial Growth of AlInGaN Quaternary Alloys by RF-MBE

AlInGaN quaternary alloys were successfully grown on sapphire substrate by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). AlInGaN quaternary alloys with different compositions were acquired by changing the Al cell's temperature. The streaky RHEED patterns were observed during AlInGaN quaternary alloys growth. Scanning Electron Microscope (SEM), Rutherford back-scattering spectrometry (RBS), X-Ray diffraction (XRD) and Cathodoluminescence (CL) were used to characterize the structural and optical properties of the AlInGaN alloys. The experimental results show that the AlInGaN quaternary alloys grow on the GaN buffer in the layer-by-layer growth mode. When the Al cell's temperature is 920 degrees C, the Al/In ratio in the AlInGaN quaternary alloys is about 4.7, and the AlInGaN can acquire better crystal and optical quality. The X-ray and CL full-width at half-maximum (FWHM) of the AlInGaN are 5arcmin and 25nm, respectively.

Improved DC and RF performance of AlGaN/GaN HEMTs grown by MOCVD on sapphire substrates

High-quality AlGaN/GaN high electron mobility transistor (HEMT) structures were grown by metalorganic chemical vapor deposition (MOCVD) on 2-in. sapphire substrates. Two-dimensional electron gas (2DEG) mobility of 1410 cm(2)/Vs and concentration of 1.0X10(13) CM-2 are obtained at 295 K from the HEMT structures, whose average sheet resistance and sheet resistance uniformity are measured to be about 395 Omega/sq and 96.65% on 2-in. wafers, respectively. AlGaN/GaN HEMTs with 0.8 mu m gate length and 0.2 mm gate width were fabricated and characterized using the grown HEMT structures. Maximum current density of 0.9 A/ mm, peak extrinsic transconductance of 290 mS/mm, unity cutoff frequency (f(T)) of 20 GHz and maximum oscillation frequency (f(max) of 46 GHz are achieved. These results represent significant improvements over the previously fabricated devices with the same gate length, which are attributed to the improved performances of the MOCVD-grown HEMT structures. (c) 2005 Elsevier Ltd. All rights reserved.

Growth and characterization of InN on sapphire substrate by RF-MBE

Indium nitride (InN) films were grown on sapphire substrates by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). Atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) spectroscopy were used to characterize the InN films. The results show that the InN films have good crystallinity, with full-width at half-maximum (FWHM) of InN (0 0 0 2) DCXRD peak being 14 arcmin. At room temperature, a strong PL peak at 0.79eV was observed. At 1.9eV or so, no peak was observed. In addition, it is found that the InN films grown with low-temperature (LT) InN buffer layer are of better quality than those without LT-InN buffer layer. (c) 2004 Elsevier B.V. All rights reserved.