Abstract
The cutoff frequency performance of an NPN Si/SiGe/SiGe Single-heterojunction bipolar transistor (SiGe SHBT) at high collector current densities has been analyzed using a 2-dimensional MEDICI device simulator. A conventional NPN Si/SiGe/Si Double-heterojunction bipolar transistor (SiGe DHBT) having uniform 14%Ge in the base region has been investigated for comparison. The analysis shows the formation of a retarding potential barrier for minority carrier electrons at the basecollector heterojunction of the DHBT structure. Whereas, the base-collector homojunction of the SiGe SHBT structure, having a uniform 14%Ge profile in its base and collector, inhibits the formation of such a retarding potential barrier. The SHBT structure with a base-collector homojunction shows an Improved cutoff frequency at a high collector current density in comparison with conventional SiGe DHBT, which makes it more promising for high speed, scaled down, field-specific applications.
Highlights
With a collector current density (Jc) for the saturated drift velocity condition is given as [9]: The use of silicon-germanium (SiGe) technology in the field of mobile communications[1] and various other Jc = q vdsatnc (1)
An NPN SiGe double-heterojunction transistor (DHBT) structure is attributed to the valence band offset for holes in emitter-base (e-b) and base collector (b-c) junction
The analysis of SiGe DHBT illustrates the formation of VRB at b-c junction due to valence band offset for holes
Summary
An NPN SiGe double-heterojunction transistor (DHBT) structure is attributed to the valence band offset for holes in emitter-base (e-b) and base collector (b-c) junction. We have simulated a conventional NPN SiGe DHBT structure with uniform 14% of Ge in strained base to supplement the earlier reported results in the formation of VRB at a b-c junction. The analysis of SiGe DHBT illustrates the formation of VRB at b-c junction due to valence band offset for holes.
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