Hot-carrier induced degradations on RF power characteristics of SiGe heterojunction bipolar transistors

Abstract

Hot-carrier (HC) effects on high-frequency and RF power characteristics of Si/SiGe HBTs are investigated in this paper. By using the two-tone load-pull measurement, we find that not only the cutoff frequency, but also the output power performances of Si/SiGe HBTs are suffered by the HC stress. In this work, S-parameters and intrinsic elements of an equivalent hybrid-model were used to validate the HC effects on high-frequency characteristics. With different bias conditions, the degradations of cutoff frequency, power gain, and linearity are found to be worse under constant base-current measurement than that under constant collector-current measurement. The HC-induced degradations on the current gain, transconductance, and ideality-factor of base and collector currents are analyzed to explain the experimental observations. Index Terms-Cut-off frequency, hot-carrier effect, linearity, power gain, power-added efficiency, SiGe HBT.

Effect of Mixed-Mode Electrical Stress on High-Frequency and RF Power Characteristics of SiGe Hetero-Junction Bipolar Transistors

“…The decrease in emitter series resistance is related to the hydrogenation of electronic traps. [8][9][10] Additionally, in our case, this effect may be due to the native oxide in the interface of the poly emitter and epi layer of the SiGe base is punctured by stressing at a higher current density. f max is a power gain index for RF transistors, and is related to the output resistance, base resistance, and isolation capacitance between the base and collector junction of Si/ SiGe HBTs.…”

“…Therefore, device electric performance under ''mixed-mode stressing'' is different from that under traditional OC stressing. 9) Since the dc performance of SiGe HBT degrades after electrical stressing, it will certainly affect the figures of merit (FOM) of RF characteristics. The cutoff frequency ( f T ) and maximum oscillation frequency ( f max ), which indicate the limitations of high-frequency current gain and power gain, respectively, are the most common RF FOMs of RF transistors expressed as…”