A single electron transistor or single-electron tunneling transistor is a special type of
field-effect transistor that operates by passing a single electron from source to drain.
Single Electron Transistor is a device that turns on and off again every time one
electron is added to it. This is the reason why it is called Single Electron Transistor.
The single electron transistor is made of metallic island (quantum nanodot) connected
through two tunneling junctions (very thin insulators) to a drain and a source
electrode.
The gate electrode connects the island through a capacitor.
The tunneling junctions are simply a thin (<10 nm) oxide layer between the island
and the electrodes.
.
When all the bias voltages (D, S, G) are zero, electrons do not have enough energy to
tunnel through the junctions.
The island or quantum dot is isolated piece of metal. The no of electrons on the
island are finite and energy of the electrons also finite or quantized.
The energy level of the electrons on the quantum dot is higher than source and drain
and no electrons can pass through it. This phenomenon is known as “Coulomb
blockade”. The size of the quantum dot is very small such that the energy of the
electrons is higher than that of thermal energy.
Applying positive voltage on the gate terminal charges the gate capacitor and causes
drop in the energy of the electrons on the quantum dot. This energy level becomes
less than that of electrons in the source.
Under this condition, at a particular gate voltage, one electron tunnels through the
tunneling junction and is placed in the quantum dot.
field-effect transistor that operates by passing a single electron from source to drain.
Single Electron Transistor is a device that turns on and off again every time one
electron is added to it. This is the reason why it is called Single Electron Transistor.
The single electron transistor is made of metallic island (quantum nanodot) connected
through two tunneling junctions (very thin insulators) to a drain and a source
electrode.
The gate electrode connects the island through a capacitor.
The tunneling junctions are simply a thin (<10 nm) oxide layer between the island
and the electrodes.
.
When all the bias voltages (D, S, G) are zero, electrons do not have enough energy to
tunnel through the junctions.
The island or quantum dot is isolated piece of metal. The no of electrons on the
island are finite and energy of the electrons also finite or quantized.
The energy level of the electrons on the quantum dot is higher than source and drain
and no electrons can pass through it. This phenomenon is known as “Coulomb
blockade”. The size of the quantum dot is very small such that the energy of the
electrons is higher than that of thermal energy.
Applying positive voltage on the gate terminal charges the gate capacitor and causes
drop in the energy of the electrons on the quantum dot. This energy level becomes
less than that of electrons in the source.
Under this condition, at a particular gate voltage, one electron tunnels through the
tunneling junction and is placed in the quantum dot.
