|Mar2-12, 08:05 PM||#1|
Minority carriers in a Schottky diode
Say I have a schottky diode with n type semiconductor. Why cant electrons from the metal flow to the valance band of the semiconductor?
If I reverse bias the schottky diode, the valance band may be higher than the fermi level at the contact, and electrons should be able to flow from metal to the semiconductor. Consequently the reverse saturation current should increase. Could anyone explain?
|Mar4-12, 05:02 PM||#2|
In case you meant the conduction band and not the valence band of the semiconductor : the electrons cannot flow from the metal to the conduction band of the semiconductor because a potential barrier forms at the contact between the metal and the semiconductor. In theory, it's height can be calculated as the difference between the work function of the metal and the electron affinity of the semiconductor. (In practice, the height depends more on the microstructure of the contact layer.) In order to cross this barrier, the electrons either have to tunnel through it or be thermally activated to jump over it. Only extremely few electrons manage to do it.
However, even if the height of the potential barrier stays the same, I guess (but I'm not sure) that its width becomes smaller making the tunneling more probable and thus increasing the current. (Maybe somebody else can comment on this?) Finally, if you increase the reverse voltage high enough. a breakdown occurs which usually destroys the diode, see
Very interesting is also
Hope that helps.
|Similar Threads for: Minority carriers in a Schottky diode|
|existence of minority carriers||Electrical Engineering||3|
|Concentration of minority carriers in a pn junction||Engineering, Comp Sci, & Technology Homework||2|
|Majority Vs Minority Carriers||Atomic, Solid State, Comp. Physics||4|
|majority carriers and minority carriers coexist, how?||Electrical Engineering||0|
|Formation of Schottky Diode||Atomic, Solid State, Comp. Physics||6|