Semiconductors for microwave frequencies

Microwaves can now be processed by semiconductor structures, which are either a further development of the transistor for the lower microwave frequency ranges, or which use the non-linear behaviour of junction devices for mixing and parametric effects, particularly for low noise levels, or which exploit transit-time effects to create an effective negative conductance gd such as impatt and Gunn devices. The important role of material parameters is discussed New experimental results on gd vs. microwave voltage amplitude are presented for Gunn diodes as an illustration of the type of device characterization required.