Abstract
The low-frequency noise characteristics of p-n-p InAlAs/InGaAs heterojunction bipolar transistors (HBTs) were investigated. Devices with various geometries were measured under different bias conditions. The base noise current spectral density (3.11 × 10 -16 A 2 /Hz) was found to be higher than the collector noise current spectral density (1.48 × 10 -16 A 2 2/Hz) at 10 Hz under low bias condition (I c = 1 mA, V EC = 1 V), while the base noise current spectral density (2.04 × 10 -15 A 2 /Hz) is lower than the collector noise current spectral density (7.87 × 10 -15 A 2 /Hz) under high bias condition (I c = 10 mA, V EC = 2 V). The low-frequency noise sources were identified using the emitter-feedback back technique. The results suggest that the low-frequency noise is a surface-related process. In addition, the dominant noise sources varied with bias levels.