Metal Insulator Metal Diode
A metal insulator metal diode is produced by inserting two metal layers around a thin insulator. It works in such a way that when a current is passed through the two layers of metal, the electrons get induced to quantum mechanically tunnel from one piece of metal to the other piece of metal passing through the insulator placed between them.
In metal-insulator-metal-diodes, it is always make sure that the insulator used in the diode is very thin as otherwise it would not be possible to pass the voltage which is of very low strength, typically of one Volt and less than this. Therefore, the insulator which is less than fifty angstroms is used to form MIM diode.
The two different metals are used in MIM diode because as a result of this there are two different barrier heights which are a utility of metal work function and the insulator electron affinity.
So, when the voltage is passed through the metal insulator metal diode, the electrons preferentially make a tunnel in one particular direction over the other, therefore resulting in the formation of a diode. Thus, we see that the main feature of MIM diode is the formation of barrier with two different heights.
Other important fact to know about metal insulator metal diode is that in these types of diodes, the tunneling effect is so fast that it is in the order of a femtosecond, generally between ten to fifteen seconds. Thus, in principle, the devices in which metal-insulator-metal-diodes are used have the ability to correct the extremely high-frequency signals, which are beyond terahertz and into the optical range.
The RC time constant, is decided by the MIM diode and circuit resistances and the diode capacitance? This capacitance is made smaller by decreasing the area of the device.
The metal insulator metal diode has been in use for a long time now, since it started in 1960s, however basic devices have put up with poor performance and reliability in the past.