Early history of the physics and chemistry of semiconductors-from doubts to fact in a hundred years

Gray (1731), Desagullier (1742) and Volta (1782) discovered and investigated electric conduction in solids. Davy (1821) found a decrease of the conductivity sigma in metals and Faraday (1833) observed a strong increase with temperature in a number of binary chemical compounds. Hittorf's (1851) measurements on Ag2S and Cu2S led to a linear relation of log sigma against 1/T. The controversial case of Ag2S is described. Hall (1879) and Rowland (1880) discovered a transverse voltage of a current carrying metal film in a magnetic field. Riecke (1901) and Drude (1900) developed the first electron theory of metals and Koenigsberger (1914) tried to explain the temperature dependence of the electrical conductivity by a dissociation theory. Baedeker (1908) was the first to observe semiconducting properties of CuI depending on the stoichiometric composition. Wagner (1933) proved that the conductivity of Ag2S is essentially electronic and not ionic. Gudden (1930) suggested that semiconduction is the result of impurities and imperfections in solids and Wagner and Schottky (1931) developed their theories of lattice defects (Fehlordnungs-Erscheinungen). Wilson (1931) presented the first band theory of intrinsic and extrinsic semiconductors. The existence of intrinsic conduction has been questioned by experimentalists and is verified only by the preparation and investigation of high-purity semiconducting elements.