Aluminum-Graded-Base PNp AlGaAs/GaAs Heterojunction Transistor with 37 GHz Cut-Off Frequency (Special Issue on Ultra-High-Speed LSIs)

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概要

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• The base transit time of an Aluminum-graded-base PNp AlGaAs/GaAs heterojunction bipolar transistor (HBT) was studied in order to clarify the effect of aluminum grading in the base. Theoretical analysis using a classical drift diffusion model with velocity saturation at the base-collector junction and a high base quasi-electric field (58 keV/cm) created by 20%-aluminum linear grading in a 400 Å base, leads to a base transit time (τ_b) of 0.9 ps. The base transit time is reduced by four times, compared to the base transit time of 3.6 ps without aluminum grading in the base. In order to demonstrate this advantage, we fabricated aluminum-graded-base PNp AlGaAs/GaAs heterojunction transistor which employs a 20%-aluminum linear graded 400 Å-wide base. The device with a 2μm×10μm emitter showed high RF performance with a cut-off frequency (f_t) of 37 GHz and a maximum oscillation frequency (f_ltmaxgt) of 30 GHz at a collector current density of 3.4×10^4 A/cm^2. Further analysis using direct parameter extraction of a small signal circuit model under the collector current density of 1.1-9.9×10^4 A/cm^2 indicated the intrinsic transit time, which is the sum of the base transit time and the collector depletion layer transit time (τ_ltscgt), was as low as 2.3 ps under low-injection level. Subtracting the collector depletion-layer transit time from the intrinsic time leads to a base transit time of 1.1 ps, which is close to the theoretical base transit time and is the shortest value ever reported. The structure is very attractive for pnp-type AlGaAs HBTs combined with Npn HBTs for complementary applications.

• 1996-04-25

著者

• KAMEYAMA Atsushi

  Toshiba Research and Development Center

• Harris James

  Department Of Electrical Engineering Stanford University

• Harris J

  Department Of Electrical Engineering Stanford University

• Kameyama Atsushi

  Toshiba Corporation Semiconductor Company

• Kameyama Atsushi

  Toshiba Ulsi Research Center Toshiba Corporation

• MASSENGALE Alan

  Department of Electrical Engineering, Stanford University

• DAI Changhong

  Department of Electrical Engineering, Stanford University

• Dai Changhong

  Department Of Electrical Engineering Stanford University

• Massengale Alan

  Department Of Electrical Engineering Stanford University

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