Application of Device-Degradation Modeling to SiGe-LNA Analysis

Abstract

In this paper, the degradation of low-noise amplifiers (LNAs) using silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) under RF stress was investigated. Electrical stress in SiGe HBTs generates hot carriers that cause the avalanche effect through impact ionization, leading to degradations in performance parameters such as S-parameters and noise figure (NF) of LNAs. To study the impact ionization caused by RF stress under large-signal conditions, an equivalent circuit model with breakdown network is employed. The model is used to compare simulation and measurement results of the degradation characteristics of SiGe LNAs. A comparison of S<inf>21</inf> and NF before and after stress shows that RF stress degrades the performance of S<inf>21</inf> by 1.85 dB and NF by 0.19 dB. The degradation model can be used to predict performance loss due to large voltage swings and provide guidelines for reliability analysis.