Ultrafast transistors and ballistic devices

This paper is concerned with the some of the details of the engineering of ultrafast transistors based on GaAs and InP for operation at and above 94 GHz. We illustrate some of the short-channel problems which arise in high-speed devices, discuss fabrication techniques for the critical gate region of the transistor, and report our most recent results on both substrates, including some of the first W-band on-wafer measurements made on such devices. We also describe a ballistic mixer device for possible application above 100 GHz, utilising a new intrinsically fast non-linear phenomenon for mixing and frequency conversion