Optimization of Base Profile in Bipolar Transistors Considering Retarding Field in Base, Sheet Resistance and Minority Carrier Velocity Saturation

Khanduri, Gagan; Panwar, B.S.

doi:10.1109/ems.2010.95

Cited by 1 publication

(1 citation statement)

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“…The methodology has been modified in the present study to optimize the base-doping profiles in SiGe HBTs, by including the effect of Ge induced bandgap narrowing for intrinsic carrier concentration and carriers diffusivity coefficients, as mentioned in Equations ( 3) and ( 4), respectively. The fixed point iteration algorithm solves for the minimum value of t B (as mentioned in Reference [24]), however, now it also takes into account the particular triangular-Ge profile and corresponding n ieB; SiGe , D nB; SiGe values in the algorithm. Once the minimum value of t B is found using a high level computer language program, then we extract the corresponding base doping profile values from the program.…”

Section: Theorymentioning

confidence: 99%

A novel approach for justification of box-triangular germanium profile in SiGe HBTs

Khanduri¹,

Panwar²

2015

J. Semicond.

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This work presents a unique and robust approach for validation of using the box-triangular germanium profile in the base of SiGe heterojunction bipolar transistors, where the methodology considers the simultaneous optimization of the p-type base doping profile in conjunction with the germanium profile in the base. The study analyses the electron motion across the SiGe base in SiGe HBTs, owing to different accelerating electric fields. The analysis first presents a figure of merit, to achieve the minimum electron transit time across the base in conjunction with the increased current gain in n-p-n-SiGe HBTs, which shows a general trend vis-à-vis the advantage of a trapezoid germanium profile, but with additional accuracy as we considered simultaneously optimized p-type base doping. The effect of minority carrier velocity saturation is then included to make the study more detailed. The analysis then investigates the shifted germanium profile in the base to further minimize the base transit time. Finally, it is shown that a shifted germanium profile eventually evolves into a box-triangular Ge-profile in the SiGe base, which could simultaneously minimize the base transit time and reduce emitter delay by virtue of the high current gain. The analysis verifies that for an average Ge-dose of 7.5% Ge across the base, a box-triangular germanium profile in conjunction with an optimum base doping profile has an approximately identical base transit time and a 30% higher current gain, in comparison with an optimum base doping and triangular Ge-profile across the whole base.

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Section: Theorymentioning

confidence: 99%