In Search of Scalable Models for FET and HEMT Structures

In Search of Scalable Models for FET and HEMT Structures

Abstract

FET and HEMT transistors designed to operate up to frequencies of 50GHz and beyond continue to be used for microwave and millimetre wave applications such as terrestrial and satellite communication, automotive radar and aerospace systems. These systems typically demand that the transistor based circuits have excellent wideband performance in terms of one or more of the following parameters – noise figure, linearity, power-added-efficiency, or saturated power handling. The optimal transistor geometry will vary widely for each scenario so circuit designers require transistor models for the full range of possible device sizes. Typically, a foundry will allow the unit-gate-width (UGW) and the number-of-gate-fingers (NOF) to be varied. In this context scalable models become very attractive as the measurement and characterisation of every possible geometry can be avoided. The following presentation will give an outline of some of the approaches that are proving to be successful in realising scalable models.