semiconductor basic

Discussion in 'General Electronics Chat' started by timkuc, Mar 24, 2014.

  1. timkuc

    Thread Starter New Member

    Jul 26, 2012
    I don't know if I am asking some stupid questions but I can't really move without knowing them.

    In reverse bias situation electrons attracted towards positive terminal and hole attracted towards negative terminal widen the depletion region .My question is that why can't these hole combined and make a bond with the metal terminal because the negative terminal will give electrons to the p side [as battery always provides electrons].
    (2) True or false ?
    "The current in forward bias flows because the potential across the diode is more then the barrier potential but the current flows due the potential applied across it ,it is not the diffusion process in the diode which occurs after when the external voltage reduce barrier potential to zero."
    I am very confused with very basics .:(
  2. Veracohr

    Well-Known Member

    Jan 3, 2011
    When reverse biased, the electrons and holes are attracted away from each other by the potential, increasing the width of the depletion region. Current requires a complete circuit, but the depletion region is almost like a break in the circuit that prohibits electrons from crossing it. When forward biased, the electrons and holes are attracted toward each other, shrinking the depletion region and making it easy for current to flow.

    I'm a bit confused by that statement too, due to the way it's written. But I think I'd say it's true. Diffusion happens when you stick P-tye and N-type pieces of semiconductor together. The P-type has an excess of holes and the N-type has an excess of electrons, so when you put them together, those two carriers are attracted to each other. In the region close to the junction, some electrons in the N-type combine with holes in the P-type, creating a region that is neutral, and is called the depletion region. This happens without external potential. When you apply an external potential, and overcome the barrier potential to make current flow, it's called drift current.