High-Frequency Characteristics of SiGe Heterojunction Bipolar Transistors under Pulsed-Mode Operation

Kun-Ming CHEN
Hua-Chou TSENG
Tsun-Lai HSU

IEICE TRANSACTIONS on Electronics   Vol.E87-C    No.5    pp.720-725
Publication Date: 2004/05/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Advances in Characterization and Measurement Technologies for Microwave and Millimeter-Wave Materials, Devices and Circuits)
Category: Active Devices and Circuits
high-frequency,  SiGe,  heterojunction bipolar transistor,  pulsed measurement,  self-heating effect,  

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High-frequency characteristics of SiGe heterojunction bipolar transistors with different emitter sizes are studied based on pulsed measurements. Because the self-heating effect in transistors will enhance the Kirk effect, as the devices operate in high current region, the measured cutoff frequency and maximum oscillation frequency decrease with measurement time in the pulsed duration. By analyzing the equivalent small-signal device parameters, we know the reduction of cutoff frequency and maximum oscillation frequency is attributed to the reduction of transconductance and the increase of junction capacitances for fixed base-emitter voltage, while it is only attributed to the degradation of transconductance for fixed collector current. Besides, the degradation of high-frequency performance due to self-heating effect would be improved with the layout design combining narrow emitter finger and parallel-interconnected subcells structure.