In this topics we will understand what is difference between MOSFET and HEMT?
Defination and use of Mosfet
Mosfet (metal-oxide semiconductor field-effect transistor, pronounced maws-feht) is a special type of field-effect transistor (fet) that works by electronically varying the channel width along which the charge carrier (electron s or s hole) flows. the wider the channel, the better the performance of the device. the load carrier inserts the channel at its source, and exits through the drain. the width of the channel is controlled by a voltage at an electrode called a gate, which is physically located between the source and the drain and is isolated from the channel by a very thin metal oxide layer.
There are two ways in which the mosfet can work. the first known as depletion mode. when there is no voltage across the gate, the channel shows its maximum conductance. as the gate voltage increases (either positive or negative, depending on whether the channel is made of p-type or n-type semiconductor material), the channel conductivity decreases. the second way in which the mosfet can operate is called an additional mode. when there is no voltage in the gate, no channels, and the device is not working. channel is produced by applying voltage to the gate. the greater the gate voltage, the better the device performs.
Mosfet has certain advantages over conventional junction junction, or jfet. because the gate is insulated from the power line, there is no current flow between the gate and the channel, no matter what gate voltage (as long as it does not become so large that it causes physical damage of the metal oxide layer). thus, the MOSFET has an unlimited practical impedance. this makes MOSFET useful for power amplifier. the device is also suitable for high-speed switching applications. some integrated circuits (ics) contain small mosfets and are used in computers.
Because the oxide layer is very thin, the MOSFET is susceptible to permanent damage by electrostatic charge. even a small electrostatic buildup can destroy MOSFETs permanently. in weak radio frequency (rf) signals, MOSFET devices generally do not work as well as other fet types.
Defination and use of Hemt
High-mobility transistor electrons (hemt), also known as heterostructure fet (hfet) or modulation-doped fet (modfet), are field effect transistors that combine the junctions between two materials with different bandgap (ie heteroin). channel is not a doped area (as is common for MOSFETs). the combination of commonly used materials is gaas with algae, although there is wide variation, depending on the application of the device. devices that incorporate more indium generally exhibit better high frequency performance, while in recent years, gallium nitride mounds have attracted attention due to their high power performance.
like other fets, hemts are used in integrated circuits as a digital on-off switch. Fets can also be used as amplifiers for large numbers of currents using small voltages as control signals. both of these uses are made possible by the unique fetal current voltage characteristics. hemt transistors can operate at higher frequencies than ordinary transistors, to millimeter wave frequencies, and are used in high frequency products such as cell phones, satellite television receivers, voltage converters, and radar equipment. they are widely used in satellite receivers, in low power amplifiers and in the defense industry.
