Extremely high peak specific transconductance AlGaAs/GaAs heterojunction bipolar transistors

Self-aligned AlGaAs/GAs heterojunction bipolar transistors with peak specific transconductances as high as 25 mS/ mu m/sup 2/ of emitter area are discussed. These are the highest specific transconductances ever reported for a bipolar transistor. These devices, which contain no indium in the emitter, display specific parasitic emitter resistances of less than 1*10/sup -7/ Omega -cm/sup 2/. This low parasitic resistance is attributed to an improved n-type contact technology, in which a molybdenum diffusion barrier and a plasma-enhanced chemical vapor deposition SiO/sub 2/ overlayer are used to achieve low specific contact resistivities.<
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