Semiconductor switching devices - Future trends

A variety of semiconductor devices and circuits have been successfully developed using conduction properties of electrons and holes in a number of elemental and compound semiconductors. Carriers confinement in a potential well, formed out of a thin layer of lower band gap material sandwitched between two layers of a higher band gap material, has been extended from one to two and three dimensions. Resultant of two-dimensional carrier sheet, quantum wire and quantum dot having discrete energy levels arising out of quantisation are being presently explored for possible device applications. A number of devices have been fabricated using resonant tunneling across a thin potential barrier. This has opened up several newer possibilities of using such structures for various electronic and optoelectronic devices and circuits applications as tunneling is relatively faster than conduction process. While looking into the interband tunneling between two quantum dots, possibility of a single electron switching has also been examined carefully. The idea of a single electron switching is conceptually being extended from quantum dots to molecules and atoms ultimately. Simulations based on transmission of electrons through a chain of molecules and atoms have shown that tens of THz speed and functional device density 10(12) devices/mm(2) are possible with such schemes. Devices based on atom relay transistor (ART) will be ultimate in its performance of switching speed. A brief on present-day situation followed by future proposals of fast switching devices for information electronics has been discussed.