As can be seen, this device works as a channel is induced in the semiconductor and this channel contains n-type charges (thus, n-channel MOFET). The thickness of this channel is controlled by the applied v (it is proportional to v V t ). As a result, when v become larger than a threshold voltage, V t, a narrow layer ECE60L Lecture Notes, pringĢ between source and drain regions is created that is populated with n-type charges (see figure). As v increases, hole concentration decreases, and the region near gate behaves progressively more like intrinsic semiconductor material (when excess hole concentration is zero) and then, finally, like a n-type material as electrons from n + electrodes (source and drain) enter this region. This voltage repels the holes in the p-type substrate near the gate region, lowering the concentration of the holes. To see the operation of a NMO, let s ground the source and the body and apply a voltage v between the gate and the source, as is shown above.

Metal contacts are also made to the source, drain, and body region. Metal is deposited on the insulator to form the ate of the device (thus, metal-oxide semiconductor). A thin (fraction of micron) layer of io 2, which is an excellent electrical insulator, is deposited between source and drain region. Two heavily doped n-type regions (ource and rain) are created in the substrate. The device is fabricated on a p-type substrate (or Body). n-channel Enhancement-Type MOFET (NMO) The physical structure of a n-channel Enhancement-Type MOFET (NMO) is shown. As transistors in these 6 FET categories behave in a very similar fashion, we will focus below on the operation of enhancement MOFETs that are the most popular. FETs in each of these three categories can be fabricated either as a n-channel device or a p-channel device. Another type of FET is the Junction Field-Effect Transistors (JFET) which is not based on metal-oxide fabrication technique. MOFET can be manufactured as enhancement-type or depletion-type MOFETs. The most widely used FETs are Metal-Oxide-emiconductor FETs (or MOFET).

As such, a FET is a voltage-controlled device.

1 Field-Effect (FET) transistors References: Barbow (Chapter 8), Rizzoni (chapters 8 & 9) In a field-effect transistor (FET), the width of a conducting channel in a semiconductor and, therefore, its current-carrying capability, is varied by the application of an electric field (thus, the name field-effect transistor).

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