Stability of carbon and beryllium-doped base GaAs/AlGaAs heterojunction bipolar transistors
GaAs/AlGaAs heterojunction bipolar transitors (HBTs) utilizing highly Be-doped base layers display a rapid degradation of dc current gain and junction ideality factors during bias application at elevated temperature. For example, the gain of a 2×10 μm2 device with a 4×1019 cm−3 Be-doped base layer o...
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Veröffentlicht in: | Applied physics letters 1991-12, Vol.59 (27), p.3613-3615 |
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Sprache: | eng |
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Zusammenfassung: | GaAs/AlGaAs heterojunction bipolar transitors (HBTs) utilizing highly Be-doped base layers display a rapid degradation of dc current gain and junction ideality factors during bias application at elevated temperature. For example, the gain of a 2×10 μm2 device with a 4×1019 cm−3 Be-doped base layer operated at 200 °C with a collector current of 2.5×104 A cm−2 falls from 16 to 1.5 within 2 h. Both the base emitter and base collector junction ideality factors also rise rapidly during device operation, and this current-induced degradation is consistent with recombination-enhanced diffusion of Be interstitials producing graded junctions. By sharp contrast, devices with highly C-doped (p=7×1019 cm−3) base layers operated under the same conditions show no measurable degradation over much longer periods (12 h). This high degree of stability is most likely a result of the fact that C occupies the As sublattice, rather than the Ga sublattice as in the case of Be, and also has a higher solubility than Be. The effect of nearby implant isolated regions in promoting Be diffusion is also reported. |
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ISSN: | 0003-6951 1077-3118 |
DOI: | 10.1063/1.105623 |