Metal–semiconductor junction

Usually an ohmic contact is desired, so that electrical charge can be conducted easily between the active region of a transistor and the external circuitry.

For lower Schottky barrier heights, the semiconductor is not depleted and instead forms an ohmic contact to the metal.

In practice, the Schottky barrier height is not precisely constant across the interface, and varies over the interfacial surface.

This made the Schottky barrier height almost completely insensitive to the metal's work function:[5] where Ebandgap is the size of band gap in the semiconductor.

As a result, the semiconductor's bands would necessarily align to a location relative to the surface states which are in turn pinned to the Fermi level (due to their high density), all without influence from the metal.

[7] The solution to this inflexibility requires additional processing steps such as adding an intermediate insulating layer to unpin the bands.

In 1907, George W. Pierce published a paper in Physical Review showing rectification properties of diodes made by sputtering many metals on many semiconductors.

During 1925–1940, diodes consisting of a pointed tungsten metal wire in contact with a silicon crystal base, were fabricated in laboratories to detect microwaves in the UHF range.

A World War II program to manufacture high-purity silicon as the crystal base for the point-contact rectifier was suggested by Frederick Seitz in 1942 and successfully undertaken by the Experimental Station of the E. I du Pont de Nemours Company.

He found the solution for both the diffusion and drift currents of the majority carriers through the semiconductor surface space charge layer which has been known since about 1948 as the Mott barrier.

Walter H. Schottky and Spenke extended Mott's theory by including a donor ion whose density is spatially constant through the semiconductor surface layer.

[23][24] They published their results in 1962 and called their device the "hot electron" triode structure with semiconductor-metal emitter.

They developed high vacuum metal film deposition technology,[27] and fabricated stable evaporated/sputtered contacts,[28][29] publishing their results in January 1963.

[27] In 1967, Robert Kerwin, Donald Klein and John Sarace at Bell Labs, patented a method to replaced the aluminum gate with a polycrystalline layer of silicon.