Overview

The first choice that must be made when designing an MMIC is the component technology that will be used to make the chip, and this choice will then lead to a decision as to which foundry process is required. The primary factor is the choice of substrate material as the properties of this semiconductor material have the greatest influence over the potential performance of the final MMIC. The electron mobility and peak velocity in the doped semiconductor determine how fast the electrons in the active components, such as the transistors, can react to quickly fluctuating electric fields, dictating their frequency response, and the energy band-gap of the semiconductor substrate determines how high the breakdown voltage of the transistors will be, hence their power-handling characteristics. The resistivity of the semiconductor substrate in its semi-insulating state also has an important effect on the circuit as its value determines the loss and Q-factor of the passive components created on its surface.

The next technology choice that must be made is the type of transistor that will be used as the active component to create the signal gain within the MMIC. At the simplest level, this is a choice between using a field effect transistor (FET) or a bipolar transistor, but there is a large range of device types, from traditional silicon complementary metal-oxide semiconductor (CMOS) transistors to devices such as high-electron-mobility transistors (HEMT) with quantum well confinement of the electrons to improve their mobility.

This chapter outlines the choice of component technology...