We present an investigation of low-frequency noise in advanced vertical <i>pnp</i> 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 <i>npn</i> and <i>pnp </i>SiGe HBTs. Geometry effects on the low frequency noise are assessed, as well as the impact of interfacial oxide(IFO) thickness on <i>pnp</i> noise characteristics. Temperature measurements and ionizing radiation are used to probe the fundamental physics of 1/f noise in<i> npn</i> and <i>pnp</i> SiGe HBTs. The<i> npn </i>transistors show a stronger size dependence than the <i>pnp</i> transistors. The 1/f noise for <i>pnp</i> 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(I<sub>B</sub>), the only exception being for the post-radiation <i>npn</i> transistor biased at low base currents, which exhibits a near-linear dependence on I<sub>B</sub>. In the proton radiation experiments, the <i>pnp</i> devices show better radiation tolerance than the <i>npn </i>devices. The observed temperature dependence for both types is quiet weak, consistent a tunneling mechanism.