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N-p-n InGaP/GaAs double heterojunction bipolar transistor has been successfully grown on a 200 mm Ge/Si wafer using metalorganic chemical vapor deposition with low defect density of 107 cm-2. Non-gold metals of Ni/Ge/Al and Ti/Al are used to form the ohmic contact for small pieces device fabrication. Both direct-current (dc) and high-frequency characteristics of the device were measured. The device with emitter area of 6 × 8 μm2 shows a dc gain of 55 at a collector current of Ic = 4 mA, with high collector-emitter breakdown voltage of ~17 V. The high-frequency response with cutoff frequency (fT) of 23 GHz and maximum available frequency (fmax) of 10 GHz can be achieved. These results demonstrate that InGaP/GaAs double heterojunction bipolar transistor grown on low defect density Ge/Si wafer has the potential for realizing III-V CMOS integrated platform for high-frequency applications.

AbstractSi/Si0.66Ge0.34coupled quantum well (CQW) structures with different barrier thickness of 40, 4 and 2 nm were grown on Si substrates using an ultra high vacuum chemical vapor deposition (UHV-CVD) system. The samples were characterized using high resolution x-ray diffraction (HRXRD), cross-sectional transmission electron microscopy (XTEM) and photoluminescence (PL) spectroscopy. Blue shift in PL peak energy due to interwell coupling was observed in the CQWs following increase in the Si barrier thickness. The Si/SiGe heterostructure growth process and theoretical band structure model was validated by comparing the energy of the no-phonon peak calculated by the 6 + 2-bandk·pmethod with experimental PL data. Close agreement between theoretical calculations and experimental data was obtained.

Measuring buried, undercut microstructures is a challenging task in metrology. These structures are usually characterized by measuring their cross sections after physically cutting the samples. This method is destructive and the obtained information is incomplete. The distortion due to cutting also affects the measurement accuracy. In this paper, we first apply the laser fluorescent confocal microscopy and intensity differentiation algorithm to obtain the complete three-dimensional profile of the buried, undercut structures in microfluidic devices, which are made by the soft lithography technique and bonded by the oxygen plasma method. The impact of material wettability and the refractive index (n) mismatch among the liquid, samples, cover layer, and objective on the measurement accuracy are experimentally investigated. OCIS codes: 100.5010, 100.6890, 120.0120, 120.2830, 120.6650.

A microvalve is a key part in a multilayer microfluidic device to control the fluid flow, and its thickness directly determines its performance. In this paper, a three-dimensional measurement technology using a white-light confocal microscope is developed for measuring both the topography and thickness of microvalves. The impact of system parameters and sample parameters on measurement accuracy is discussed in detail, particularly for measurement with a dry objective. With this technique, the microvalve thicknesses before and after bonding were characterized with submicrometer measurement sensitivity and about 1 [micro]m measurement accuracy. OCIS codes: 180.1790, 080.0080, 080.1010, 110.6880, 110.2960.

This paper demonstrates a ultraviolet (UV)-embossed polymeric chip for protein separation by capillary isoelectric focusing (CIEF) and identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The polymeric chip was replicated by a UV-embossing technique using a soft rubber mold. Five diverse widely investigated families of UV-cured formulations were examined for MALDI ionization efficiency of bovine serum albumin (BSA) samples spotted on the polymer surfaces. The signal and signal-to-noise ratio from the polyester formulation were each 12 times those obtained with PMMA (a commonly used polymer material for MALDI) at picomole sample concentration. A polyester chip was successfully used to carry out CIEF to separate proteins, followed by MALDI-TOF-MS identification. Issues related to the successful chip fabrication and protein separation and identification are discussed.

A comprehensive characterization is presented, of dc and microwave performances involving InP/InGaAs metamorphic heterojunction bipolar transistors (HBT). Metamorphic heterojunction bipolar transistors (MHBT) were grown by solid-source molecular beam epitaxy (SSMBE).

Research was conducted on the surface and structural effects of aluminum mole fraction on AlxGa1-xAs prepared at low temperature via molecular beam epitaxy using scanning force microscopy. Results showed an average roughness increase of as much as 26 angstrom accompanying AlGaAs surface morphology changes. It was found that high arsenic partial pressure and low substrate temperature hamperedaluminum atom surface mobility which subsequently led to surface roughness degradation.

The influence of Si doping in GaAs layers grown by molecular beam epitaxy as a function of varying arsenic to gallium flux ratio was investigated. The results showed that high electron concentrations can be achieved by using a slow growth rate of 1500 Angstroms per hour. However, this concentration decreased rapidly when the flux ratio became smaller. At lower flux ratios, the effect of Si accumulation near the surface was increased.