111 research outputs found
High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate
Si/Ge uni-traveling carrier photodiodes exhibit higher output current when
space-charge effects are overcome and thermal effects are suppressed, which is
highly beneficial for increasing the dynamic range of various microwave
photonic systems and simplifying high-bit-rate digital receivers in different
applications. From the point of view of packaging, detectors with
vertical-illumination configuration can be easily handled by pick-and-place
tools and are a popular choice for making photo-receiver modules. However,
vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from
inter-constraint between high speed and high responsivity. Here, we report a
high responsivity vertical-illumination Si/Ge UTC photodiode based on a
silicon-on-insulator substrate. The maximum absorption efficiency of the
devices was 2.4 times greater than the silicon substrate owing to constructive
interference. The Si/Ge UTC photodiode was successfully fabricated and had a
dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25%
thinner Ge absorption layer.Comment: 5pages,2figure
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
Full-Field Strain Mapping at a Ge/Si Heterostructure Interface
The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface
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