ABSTRACT
Semiconductors have been at the origin of the most important industrial revolution of the 20th century, which has been dominated by the development of electronics. One of its basic components, the transistor, was initially proposed in the 1940s and based on germanium [1], This was a bipolar device, a structure still in use in amplifi ers. Another device structure, the fi eld-effect transistor, FET, was developed later and used as a building block in electronic components such as logic circuits and microprocessors [2]. Field-effect transistors are unipolar devices in which the current fl owing between two electrodes is controlled by the voltage applied at a third electrode, which recalls the mode of operation of the vacuum triode that was used in earlier radio and TV sets.
