OVERVIEW

This chapter discusses five models available in circuit simulators. Since dedicated HBT models are to date only sparsely available in simulation software packages, and due to their importance concerning the modeling of bipolars in general, the SPICE Gummel-Poon (SGP) and vertical bipolar intercompany (VBIC) models are addressed first. The simulation accuracy of these models, however, is only limited. Both lack a formulation of velocity modulation effects in the collector, and the SGP model does not provide dynamic self-heating.

The last three models to be covered here, the UCSD, Agilent and FBH models, are full-featured III V HBT models. The UCSD model deserves respect since it was available at a time when virtually all simulators only provided the SGP model for bipolars, and advanced models for Si devices like VBIC, MEXTRAM, and HICUM were largely unknown or still under development. It was finished around the same time as the GaAs HBT technology became commercially available, and it is based on rigorous physical studies that are the basis for all later modeling approaches. Unfortunately, it suffers from several shortcomings concerning the implementation, as will be discussed in the respective section.

The second generation models (i.e., Agilent and FBH models), overcome these issues. The starting point of the development of the Agilent model, similar to the UCSD model, was the work of L. Camnitz [1]. Also, the DC model is close to the UCSD model in order to be backward compatible. It was initially developed to describe InP-based HBTs, and was extended to...