Investigation Into the Scalability of Selectively Implanted Buried Subcollector (SIBS) for Submicrometer InP DHBTs |
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| Authors: | James Chingwei Li Yakov Royter Tahir Hussain Mary Y. Chen Charles H. Fields Rajesh D. Rajavel Steven S. Bui Binqiang Shi Donald A. Hitko David H. Chow Peter M. Asbeck Marko Sokolich |
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| Affiliation: | Dept. of Electr. & Comput. Eng., California Univ., San Diego, La Jolla, CA; |
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| Abstract: | Recent attempts to achieve 400 GHz or higher fT and f MAX with InP heterojunction bipolar transistors (HBTs) have resulted in aggressive scaling into the deep submicrometer regime. In order to alleviate some of the traditional mesa scaling rules, several groups have explored selectively implanted buried subcollectors (SIBS) as a means to decouple the intrinsic and extrinsic collector design. This allows tauC to be minimized without incurring a large total CBC increase, and hence, a net improvement in fT and fMAX is achieved. This paper represents the first investigation into the series resistance and capacitance characteristics of submicrometer-width SIBS regions (as narrow as 350 nm) for InP double HBTs. Although the SIBS resistance is higher than that of epitaxially grown layers, the SIBS concept is able to provide good dopant activation and a significant decrease in CBC. S-parameter measurements are presented to clarify the impact of SIBS geometry variations, caused by both intentional device design and process variations, on fT and fMAX. Parasitic resistances and high background doping limit the fT improvement, but the CBC reduction is sufficient to demonstrate a 30% increase in fMAX. Results indicate that further improvements in fT and fMAX using the SIBS concept will be possible |
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