We present an investigation of low-frequency noise in advanced vertical pnp bipolar junction transistors (BJTs) with
differing interfacial oxide thicknesses (10Å, 12Å, and 14Å). Low-frequency noise is observed to exhibit a cubic
dependence on IFO thickness. Devices were measured across the temperature range of 90 K to 450 K. From 90 K to 250
K, the magnitude of the low-frequency noise is found to decrease with temperature, but from 250 K to 450 K the noise
actually increases with temperature. Devices were hot-carrier (electrically) stressed, and the low-frequency noise was
found to be almost unchanged with the addition of stress-induced traps. The transparency fluctuation model is suggested
as a possible explanation for the operative noise mechanism, due to the similar dependence of base current and low-frequency
noise on interfacial oxide thickness.
We present a comprehensive investigation of the fundamental differences in low frequency noise behavior between npn and pnp SiGe HBTs. Geometry effects on the low frequency noise are assessed, as well as the impact of interfacial oxide(IFO) thickness on pnp noise characteristics. Temperature measurements and ionizing radiation are used to probe the fundamental physics of 1/f noise in npn and pnp SiGe HBTs. The npn transistors show a stronger size dependence than the pnp transistors. The 1/f noise for pnp SiGe HBTs exhibits an exponential dependence on IFO thickness, indicating that IFO produces the main contribution. In most cases, the magnitude of the 1/f noise has quadratic dependence on the base current(IB), the only exception being for the post-radiation npn transistor biased at low base currents, which exhibits a near-linear dependence on IB. In the proton radiation experiments, the pnp devices show better radiation tolerance than the npn devices. The observed temperature dependence for both types is quiet weak, consistent a tunneling mechanism.