The built-in potential (at 300 K) equals fi = kT/q ln (1016 x 9 x 1017/ni2) = 0.77 V, using kT/q = 25.84 mV and ni = 1010 cm-3. The built-in potential (at 100°C) equals fi = kT/q ln(1016 x 9 x 1017/ni2) = 0.673 V, using kT/q = 32.14 mV and ni = 8.55 x 1011 cm-3 (from Example 20).
What is the built-in potential of a pn junction?
The built-in potential of a P N junction diode is 0.7 V at room temperature .
Can we measure the built-in potential?
An ordinary voltmeter has finite input impedance which simply means that, to measure a voltage across, there must be some (tiny) current through the voltmeter. Thus, to measure the built-in potential of a diode with a voltmeter would require that the built-in potential ‘drive’ a (tiny) current through the voltmeter.
What is the formula for barrier potential?
The barrier potential for pn junctions is given by following relation, Vbi = Vt ln(Na*Nd/ni2) which is normally 0.2V for Ge and 0.8V for Si.
What is built-in potential?
Equilibrium (zero bias) In a p–n junction, without an external applied voltage, an equilibrium condition is reached in which a potential difference forms across the junction . This potential difference is called built-in potential .
How do you measure contact potential?
The contact potential cannot be measured because when contact is made to the junction a potential forms at the contacts which works to cancel the contact potential. The contact potential also separates the bands with the conduction energy bands higher on the p-side.
What is the built-in voltage?
Built-in voltage is simply the difference of the Fermi levels in p- and n-type semiconductors before they were joined .
What is the potential barrier in pn junction?
The potential barrier in the p-n junction is a type of barrier which does not allow the normal flow of charge across the junction and this resistance to the flow of charge is known as barrier potential.
What is meant by barrier potential?
: a region in which particles (as alpha particles, photoelectrons, or thermions) are decelerated or stopped by a repulsive force .
Why pn junction is called a diode?
A diode is called a diode because it has two distinct electrodes (i.e. terminals) , called the anode and the cathode. A diode is electrically asymmetric because current can flow freely from the anode to the cathode, but not in the other direction.
What is barrier potential difference?
Definition: The potential barrier in the PN-junction diode is the barrier in which the charge requires additional force for crossing the region . In other words, the barrier in which the charge carrier stopped by the obstructive force is known as the potential barrier.
How potential barrier is created?
When the holes start to move towards the electrons then there is formation of the layer of electrons on the p-type and a layer of holes in the n-type side which forms a region known as depletion layer, this depletion layer is the cause of the formation potential barrier.
What’s the potential barrier of germanium?
The barrier potential of germanium is approximately 0.3 V , and of silicon is 0.7 V. These values cannot be measured directly and appears across the space charge region of the junction. In order to produce current conduction, the barrier potential of a P-N junction must be overcome by an external voltage source.
What is the contact potential?
• The contact potential is the voltage necessary to maintain equilibrium at the . junction . • The contact potential does not imply the presence of an external potential.
Is contact and built-in potential same?
Thus, an electric field is formed going from the n-side to the p-side and there is a built-in potential, from the p to the n side. This potential is called the junction potential or contact potential.
What is the contact potential difference?
The potential difference that occurs between two electrically connected metals or between the base regions of two semiconductors . ... As a result, a contact potential difference occurs between the two metals or semiconductors.
