Band Bending and Potential & Kinetic Energies
Band bending occurs when an electric field is applied to a semiconductor.
When there isn't an electric field being applied, the energy bands are
not a function of position. Therefore, when an electric field is applied,
energy is being supplied to the carriers in the material. Where band bending
has occurred, we can measure the energy being given to the electrons or
holes by taking a reference energy and measuring the distance between it
and the energy the carrier is at.
In essence, the potential energy of an electron is the distance the
electron is from the reference energy to Ec, the lowest
conduction band energy. The kinetic energy of an electron is the distance
between Ec and the energy it is at. For holes, it's similar.
A hole's potential energy is measured as being the distance between the
reference energy and Ev, the highest valence band energy.
The kinetic energy of a hole is measured by taking the difference between
Ev and the energy the hole is at.