BY :K . SHIVA KUMAR REDDYP . MANOJ

VACUUM TUBE COMPUTER

THE FIRST TRANSISTOR

TRANSISTORIZED COMPUTER…

THE FUTURE ELECTRONICS

SINGLE ELECTRON TRANSISTORS

Source Drain

SiO2 Insulator (Glass) Gate

holes

electrons

5 volts

electrons to be transmitted

MOSFET OperationStep 1: Apply Gate Voltage

Step 2: Excess electrons surface in channel, holes are

repelled.

Step 3: Channel becomes saturated with electrons.

Electrons in source are able to flow across channel to Drain.

P

N N

SINGLE ELECTRON TRANSISTOR

COULOMB BLOCKADE BARRIER

• No electron on quantum dot Electrostatic energy = 0

• Electron put on the quantum dot Charge stored EC = E2/2Cdot

• EC acts as potential barrier.• This potential barrier is called COULOMB BLOCKADE BARRIER.

CONDITION 1

1.Thermal energy < Coulomb blockade barrier KBT < E2/2Cdot

For safety 10KBT < E2/2Cdot

For spherical capacitor C α d(diameter of dot)

CONDITION 2

2. Uncertainty in energy < charging energy

E < e2/2Cdot 1From uncertainity principle E. T ~ h/2

E ~ h/2 T E ~ h/2RCdot 2

Put 2 in 1 h/2RCdot < e2/2Cdot R > h/e2

Hence R > 26kohm

OPERATION OF SINGLE ELECTRON TRANSISTOR

STAGE 1 STAGE 2 STAGE 3

STAGE 1:

STAGE 2:

Applying negative voltage

Applying positive voltage

FERMI LEVELS IN STAGE 2 :

STAGE 2:

Applying negative voltage

Applying positive voltage

Applying positive voltage

FERMI LEVEL IN STAGE 3:

Gate voltage and current relation

curre

nt

Gate voltagee2/2Cdot 2e2/2Cdo

t3e2/2Cdot

ADVANTAGES

• Power consumption

• Memory cells

• Size

• Heat dissipation

K . SHIVA KUMAR REDDYP . MANOJ