Depletion-mode field-effect transistors (FETs) at standard voltage. From left to right: Junction FET, Polysilicon Metal-Oxide-Semiconductor FET, Dual-Gate Metal-Oxide-Semiconductor FET, Metal-Gate Metal-Oxide-Semiconductor FET, Metal-Semiconductor FET. Depletion layer, electrons, holes, metal, insulator. Top: Source, Bottom: Drain, Left: Gate, Right: Body. Details of channel formation due to voltage are not shown.
Doped FETs (explained below) use channels to fabricate N-type or P-type semiconductors. In depletion-mode FETs, the drain and source may be doped into different types to the channel. Or in boost-mode FETs, they may be doped into similar types. Field-effect transistors are distinguished by the different methods of insulating the channel and gate.
Types of FETs include:
DEPFET (Depleted FET) is a FET fabricated on a fully depleted substrate and used as a sensor, amplifier, and memory electrode. It can be used as an image (photon) sensor.
A DGMOFET (Dual-gate MOSFET) is a MOSFET with two gates.
A DNAFET is a special type of FET used as a biosensor, detecting matching DNA strands through a gate made of single-stranded DNA molecules.
A FREDFET (Fast Recovery Epitaxial Diode FET) is a special type of FET used to provide a very fast restart (shutdown) body diode.
A HEMT (High Electron Mobility Transistor), also known as a HFET (Heterostructure FET), is fabricated in a triple semiconductor such as AlGaAs using bandgap engineering. The fully depleted wide bandgap creates insulation between the gate and the body.
An IGBT (Insulated-Gate Bipolar Transistor) is a device used for power control. Its structure is similar to a bipolar-channel MOSFET. They are typically used for operation in the drain-source voltage range of 200-3000 volts. Power MOSFETs are still chosen for devices with drain-source voltages between 1 and 200 volts.
ISFETs are ion-sensitive field-effect transistors used to measure ion concentration in solution. As the ion concentration (e.g., pH) changes, the current through the transistor changes accordingly.
JFETs use a p-n junction with opposite bias to separate the gate and body.
MESFETs (Metal-Semiconductor FETs) replace the PN junction of a JFET with a Schottky barrier; they are used in GaAs and other group III-V semiconductor materials.
MODFETs (Modulation-Doped FETs) use a quantum well structure composed of screened active regions doped.
MOSFETs use an insulator (typically silicon dioxide) between the gate and body.
NOMFETs are nanoparticle organic memory field-effect transistors.
OFETs are organic field-effect transistors that use organic semiconductors in their channels.
