Materials in Electronics/The Hole

The hole is a carrier of positive charge. It is named "hole" because it equivalent to an empty space in the lattice of the conductor where an electron could be. It has the same charge as the electron, but positive. Therefore, the holes move in the same direction as conventional current:



Holes do, however, have a different mass, and a different time between colllions and therefore a different mobility, called the hole mobility, &mu;h. This is given by:


 * $$\mu_h=\frac{e \tau_h}{m_h}$$

To properly model current flow, we should take both electron and hole flow into account:


 * $$\sigma= e \left(n \mu_e + p \mu_h \right) $$

where
 * n is the electron density in m-3
 * p is the hole density in m-3


 * $$\sigma = n{{e^2 \tau _e } \over {m_e }} + p{{e^2 \tau _h } \over {m_h }}$$

where
 * &tau;e is the electron scatering time in s
 * &tau;h is the electron scatering time in s
 * mh is the mass of a hole in kg