Photoelectromagnetic Effect

the phenomenon whereby an electromotive force (emf) is generated when electromagnetic radiation is incident in the perpendicular direction on a homogeneous semiconductor placed in a magnetic field H that is perpendicular to the radiation flux; the direction of the generated emf is perpendicular to both the magnetic field and the radiation flux.

The mean energy of the charge carriers in the semiconductor changes as a result of the absorption of the incident radiation by the carriers. Such “heating” of the carriers is nonuniform and generates a current of hotter carriers in the direction in which the radiation propagates. Since the semiconductor is electrically open in this direction, a compensating current of colder carriers arises in the opposite direction. The free-carrier lifetime is energy dependent, so that a magnetic field perpendicular to the currents deflects the hot and cold carriers differently, resulting in the generation of the emf.

In contrast to the Nernst-Ettingshausen effect and the photomagnetoelectric, or Kikoin-Noskov, effect, the photoelectromagnetic effect occurs even if no temperature gradient is present in the crystal lattice of the semiconductor or no carrier concentration gradient is present in the semiconductor. The emf is the highest in semiconductors with a low effective charge-carrier mass, for example, in InSb at low temperatures.

The photoelectromagnetic effect is used to construct highly sensitive microwave and infrared detectors with a low time constant. Such detectors are employed in radio astronomy, space studies, spectroscopy, and passive radar.