THIN-FILM BIPBSRCACUO DIRECT-CURRENT SUPERCONDUCTING QUANTUM INTERFERING DEVICES OPERATING AT 78-K

Direct current SQUIDs (superconducting quantum interference devices) have been successfully fabricated by using a Pb-doped BiSrCaCuO superconducting thin film made by mixed evaporation of a single source composed of related components with a resistance heater. The dc SQUID comprises a square washer with a small hole. These SQUIDs show perfectly periodic voltage-flux characteristics without magnetic shield, that is, typically, the flux noise and energy resolution at a frequency range from dc to 1 Hz and at 78 K being 1.7 x 10(-3) PHI-0/ square-root Hz and 3.6 x 10(-26) J/Hz, respectively. Meanwhile, we have found out that one of the SQUIDs still was able to operate on flux-locked mode without bias currents and showed voltage-flux second harmonic characteristics. This phenomenon is not well understood, but it may be related to I-V (current-voltage) characteristics of the dc SQUID.

First-principles investigation of the electronic structure and magnetism of eskolaite

The electronic structure and magnetism of eskolaite are studied by using first-principles calculations where the on-site Coulomb interaction and the exchange interaction are taken into account and the LSDA+U method is used.The calculated energies of magnetic configurations are very well fitted by the Heisenberg Hamiltonian with interactions in five neighbour shells; interaction with two nearest neighbours is found to be dominant. The Neel temperature is calculated in the spin-3/2 pair-cluster approximation. It is found that the measurements are in good agreement with for the values of U and J that are close to those obtained within the constrained occupation method.The band gap is of the Mott-Hubbard type.

InP-base resonant tunneling diodes

We have fabricated In_0.53Ga_0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing.The epitaxial layers of the RTD were grown on semi-insulating (100) InP substrates by molecular beam epitaxy.RTDs with a peak current density of 24.6 kA/cm~2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.

A Multi-Finger Si_(1-x)Ge_x/Si Heterojunction Bipolar Transistor for Wireless Power Amplifier Applications

A large area multi-finger configuration power SiGe HBT device(with an emitter area of about 880μm~2)was fabricated with 2μm double-mesa technology.The maximum DC current gain β is 214.The BV_(CEO) is up to 10V,and the BV_(CBO) is up to 16V with a collector doping concentration of 1×10~(17)cm~(-3) and collector thickness of 400nm.The device exhibits a maximum oscillation frequency f_(max) of 19.3GHz and a cut-off frequency f_T of 18.0GHz at a DC bias point of I_C=30mA and V_(CE)=3V.MSG(maximum stable gain)is 24.5dB,and U(Mason unilateral gain)is 26.6dB at 1GHz.Due to the novel distribution layout,no notable current gain fall-off or thermal effects are observed in the I-V characteristics at high collector current.

DCXRD Investigation of a Ge/Si（001） Island Multilayer Structure

A Ge/Si（001） island multilayer structure is investigated by double crystal X-ray diffraction, transmission electron microscopy,and atomic force microscopy. We fit the satellite peaks in the rocking curve by two Lorentz lineshapes, which originate from the wetting layer region and the island region. Then from the ratio of the thick- nesses of the Si and Ge （GeSi） layers as determined by TEM,tbe Ge compositions of the wetting layer and islands are estimated to be about 0. 51 and 0. 67, respectively,according to the positions of the fitted peaks. This proves to be a relatively simple way to investigate the Ge/Si （001） island multilayer structure.

Layout Design and Optimization of RF Spiral Inductors on Silicon Substrate

The effects of key geometrical parameters on the performance of integrated spiral inductors are investigated with the 3D electromagnetic simulator HFSS. While varying geometrical parameters such as the number of turns （N）,the width of the metal traces （W）,the spacing between the traces （S）,and the inner diameter （ID）, changes in the performance of the inductors are analyzed in detail. The reasons for these changes in performance are presented. Simulation results indicate that the performance of an integrated spiral inductor can be improved by optimizing its layout. Some design rules are summarized.

Design and Fabrication of Power Si1-xGex/Si Heterojunction Bipolar Transistor for Wireless Power Amplifier Applications

A multi-finger structure power SiGe HBT device （with an emitter area of about 166μm^2） is fabricated with very simple 2μm double-mesa technology. The DC current gain β is 144.25. The B-C junction breakdown voltage reaches 9V with a collector doping concentration of 1 × 10^17cm^-3 and a collector thickness of 400nm. Though our data are influenced by large additional RF probe pads, the device exhibits a maximum oscillation frequency fmax of 10.1GHz and a cut-off frequency fτ of 1.8GHz at a DC bias point of IC=10mA and VCE = 2.5V.

Passively Mode Locked Diode-End-Pumped Yb∶YAB Laser with High Reflectivity Type Semiconductor Saturable Absorption Mirror

利用金属有机气相淀积方法生长了一种新型吸收体:高反射率半导体可饱和吸收镜.用这种吸收体兼作端镜,实现了1.044μm半导体端面泵浦Yb∶YAB激光器被动锁模,脉冲宽度为3.05ps,重复率为375MHz,输出功率为45mW.

Passive mode locking of an Yb:YAB laser with a low modulation depth SESAM

A passive mode-locked diode-pumped self-frequency-doubling Yb:YAB laser with a low modulation depth semiconductor saturable absorber mirror operating at 374 MHz is demonstrated. The measured pulse duration is 1.98 ps at the wavelength of 1044 nm. The maximum average power reaches 45 mW.

LD Side-Pumped Passive Mode-Locked TEM00 Nd:YAG Laser Based on SESAM

We report an LD side-pumped continuous-wave passive mode-locked Nd:YAG laser with a Z-type folded cavity based on a semiconductor saturable absorber mirror (SESAM). The average output power 2.95 W of mode-locked laser with electro-optical conversion efficiency of 1.3% and high beam quality (M-x(2) = 1.25 and M-y(2) = 1.22) is achieved. The repetition rate of mode-locked pulse of 88 MHz with pulse energy of 34 nJ is obtained.