Question

Write a detailed summary about the working principle of Schottky diodes, photodiodes, solar cells and light emitting diodes (LEDs). You can use any source you want, but please include your sources in the “References” section of your summary!

Answer 1

schotty barrier

schotty barrier diode is formed by bringing metal into contact with a moderately doped n type semiconductor material.The resulting metal semiconductor junction behaves like a diode conducting current in one direction and acting as an open circuit and in the other.And V-I charactericks of the schotty diode also similar like normal diode except1)here current is conducted by majority carriers(electrons) so it doesnot exhibit the minority carrier charge storage effects in normal diode so it is faster in switching action.2)forward voltage drop of conducting diode is lower than that of pn junction diode.

2)Photo diode

if revese biased pn junction is illuminated that is exposed to a incident light the photons impcating on the junction cause covalent bonds to break and thus electron hole pairs are generated in the depletion layer.The electric field in the depletion region then sweeps the liberated electrons to the n side and holes to the p side.giving rise the current across the junction.The current is known as photo current is praportional to the intensity of light such diode is photo diode and is used to convert light signals into electric signals

3)Solar cells:

high purity silicon crystals are used to manufacture solar cells.Silicon atoms have four arms under stable conditios they become perfect insulators we make this as n type semiconductor by doping with a phosphorous film.

a pn junction is formed by placing p type and n type semiconductor next to one another.The p type with one less electron attracts the one surplus electron from the ntype to stablilize itself.thus the electricty if displaced and generates a flow of electrons otherwise known as electricity.when the sunlight hits the semiconductor an electron springs up and it's attracted towards the n type semiconductor.This causes more negative in the n type semiconductor and more positives in the p type.Thus generating high flow of electricity.

4)Light emitting diode:

it performs the inverse of the functions of the photodiode.it converts a forward current in to light.minority carriers are injected across the junction and diffuse into the p and n regions.The diffusing minority carriers then recombine with the majority carriers such recomninations can be made to give rise the light emission.This can be done by fabricating the pn junction using a semiconductor of the type known as direct bandgap materials.The light emitted by the LED is praportional to the number of recombinations that take place which in turn is praportional to the forward current in the diode

reference:microelectonic circuits by sedra and smith