When a metal is deposited on silicon, these dangling bonds give rise to interface states within the energy band gap of silicon. The interface Fermi energy is pinned by these interface states, making the Schottky barrier height independent of the metal work function and primarily controlled by the interface states. This is the most commonly encountered difficulty in fabricating a semiconductor-metal ohmic contact. To make such a junction ohmic we will have to resort to doping the semiconductor, which would result in the thinning down of the energy barrier at the interface and consequently allowing for tunneling. It should be however noted that the resistance of such a junction is fairly high because electrons have to tunnel through the thinned Schottky barrier.