TITLE

High-gain, high-frequency AlGaAs/GaAs graded band-gap base bipolar transistors with a Be diffusion setback layer in the base

AUTHOR(S)
Malik, R. J.; Capasso, F.; Stall, R. A.; Kiehl, R. A.; Ryan, R. W.; Wunder, R.; Bethea, C. G.
PUB. DATE
March 1985
SOURCE
Applied Physics Letters;3/15/1985, Vol. 46 Issue 6, p600
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
AlGaAs/GaAs heterojunction bipolar transistors (HBT’s) with graded band-gap bases were fabricated from computer-controlled molecular beam epitaxy layers. It was found that the use of an undoped setback layer of 200–500 Å to offset Be diffusion in the emitter resulted in significant current gain increases. Maximum current gains of 1150 for a base width of 0.18 μm were obtained which are the highest yet reported for graded base HBT’s. Zn diffusion was used to contact the base and provides a low base contact resistance. Microwave s-parameter measurements yielded fT=5 GHz and fmax=2.5 GHz. Large signal pulse measurements resulted in rise times of τr∼150 ps and pulsed collector currents of Ic>100 mA which is useful for high current laser drivers.
ACCESSION #
9817254

 

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