High-gain, high-frequency AlGaAs/GaAs graded band-gap base bipolar transistors with a Be diffusion setback layer in the base
- 15 March 1985
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 46 (6) , 600-602
- https://doi.org/10.1063/1.95553
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.Keywords
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