Unilateral power gain limitations due to dynamic base widening effects

Power gain singularities in transferred-substrate InAlAs-InGaAs-HBTs

“…As the theory in [8]- [10] depends on the device operating in the base pushout regime, we note for the data presented in Fig. 1, the operating current density of the device referenced to the emitter junction area is 0.93 mA m .…”

“…The theory proposes a sub-resonance in the unilateral power gain followed by a much steeper than 20 dB/decade roll-off in the unilateral power gain. Given the similarity of the theory to the presented results and the fact that the publications make specific reference to results from our research group, we feel it is necessary to present data of highlighted importance in [8]- [10].…”

“…A series of recent publications have presented a hypothesis describing a resonance behavior in the unilateral power gain due to the dynamics of hole movement in the collector for HBTs operating under the condition of base pushout. [8]- [10]. Given the similarities to the measured data, parameters of highlighted importance from the proposed theory are discussed.…”

“…A recent series of publications [8]- [10] has proposed a resonance behavior in the unilateral power gain for InGaAs collector HBTs operating under the condition of base-pushout [15]. The theory proposes a sub-resonance in the unilateral power gain followed by a much steeper than 20 dB/decade roll-off in the unilateral power gain.…”

“…The sub-resonance theory of [8]- [10] makes definite predictions of measurable transistor quantities and these predictions may be compared to experimental data. Among these predictions are: an increase in the slope of the roll-off in the maximum available and maximum stable gain at frequencies above the resonance [8], an experimentally measured increase in the roll-off of the short-circuit current gain for a device said to be operating in base pushout [10], a peaking in the magnitude of the common-base current gain followed by a steep decrease [9], [10], and a strong peaking in the effective collector-base ca- pacitance with increasing frequency [9]. None of these experimentally observable trends were seen in the measured transistor characteristics.…”