Ohmic contacts to semiconductors are typically constructed by depositing thin metal films of a carefully chosen composition, possibly followed by annealing to alter the semiconductor–metal bond.

To form an excellent ohmic contact (low resistance), the barrier height should be small everywhere and furthermore the interface should not reflect electrons.

The Schottky barrier height between a metal and semiconductor is naively predicted by the Schottky–Mott rule to be proportional to the difference of the metal-vacuum work function and the semiconductor-vacuum electron affinity.

Thus, the heights of the Schottky barriers in metal–semiconductor contacts often show little dependence on the value of the semiconductor or metal work functions, in stark contrast to the Schottky–Mott rule.

Since a native oxide rapidly forms on the surface of silicon, for example, the performance of a contact can depend sensitively on the details of preparation.

The measurement of contact resistance is most simply performed using a four-point probe although for more accurate determination, use of the transmission line method is typical.

As with other reactive metals, Al contributes to contact formation by consuming oxygen from native silicon-dioxide residue.

Silicide contacts can also be deposited by direct sputtering of the compound or by ion implantation of the transition metal followed by annealing.

Transparent or semi-transparent contacts are necessary for active matrix LCD displays, optoelectronic devices such as laser diodes and photovoltaics.

The charging and discharging of the leads resistance is a major cause of power dissipation in high-clock-rate digital electronics.

Contact resistance causes power dissipation by Joule heating in low-frequency and analog circuits (for example, solar cells) made from less common semiconductors.