Determination of a small-signal model for ion-implanted microwave transistors

Most microwave transistor models are useful within specific frequency ranges; outside those ranges, they become inaccurate essentially because of the distributed nature of the active base resistance which is modeled as a lumped element. In this paper, a quantitative study of the two-dimensional current flow in the active region of an ion-implanted device leads to the synthesis of a small-signal model, emphasizing its relations to the distributed parameters defined. Methods for extracting those parameters are proposed via expressions that relate them to electrical measurements at the terminals. A final section deals with the analysis of experimental data to verify the validity of a distributed equivalent circuit at frequencies up to 10 GHz.