Bernhard Friedrich Adolf Gudden (14.03.1892 — 3.08.1945) was a German experimental physicist. He graduated from the University of Göttingen, where in 1919 he received the degree of Doctor of Philosophy and worked (professor from 1924).
From 1926 he was professor at the University of Erlangen and from 1939 director of the Institute of Physics of the University of Prague.
His work was in the field of solid-state physics and the physics of semiconductors. He studied photoelectric phenomena and conductivity in semiconductors, and photoelectric processes in diamond, selenium, sulfides and halides. From the early 1920s, together with R. Pohl, he began systematic studies of the photoconductivity of non-metallic crystals. Having separated the primary photocurrent in crystals from a number of secondary processes, they established that it has no inertia, that it is proportional to the intensity of the light, and that saturation sets in as the voltage is raised. As a result a technique for studying photoelectric phenomena was also developed, which was later widely used for special investigations of semiconductors. In experiments with diamonds, together with R. Pohl, he established the basic laws of the internal photoelectric effect. In 1930 he concluded that impurities play a special part in the conductivity of semiconductors and put forward the hypothesis that this conductivity is impurity in nature. Although the hypothesis proved not to be entirely correct, it nevertheless played an essential part in the creation of the first theory of the electrical conductivity of semiconductors.