energy band diagram in a pn junction

Discussion in 'General Electronics Chat' started by VENUGOPAL ADABALA, Jul 9, 2016.


    Thread Starter New Member

    Dec 15, 2015
    *silicon has a specific valence and conduction band energies that does not change with doping
    *so,when a pn junction is formed to maintain the uniform fermi energy level there is a shift in the energy bands of respective sides
    *how does it occur?
    this is where i found disruption

    4.2.1. Flatband diagram

    [​IMG] [​IMG][​IMG][​IMG][​IMG]
    The principle of operation will be explained using a gedanken experiment, an experiment, which is in principle possible but not necessarily executable in practice. We imagine that one can bring both semiconductor regions together, aligning both the conduction and valence band energies of each region. This yields the so-called flatband diagram shown in Figure 4.2.2.

    Figure 4.2.2 : Energy band diagram of a p-n junction (a) before and (b) after merging the n-type and p-type regions
    Note that this does not automatically align the Fermi energies, EF,n and EF,p. Also, note that this flatband diagram is not an equilibrium diagram since both electrons and holes can lower their energy by crossing the junction. A motion of electrons and holes is therefore expected before thermal equilibrium is obtained. The diagram shown in Figure 4.2.2 (b) is called a flatband diagram. This name refers to the horizontal band edges. It also implies that there is no field and no net charge in the semiconductor.