Thermal emission of semiconductors under nonequilibrium conditions

Abstract

The thermal emission of semiconductors under the fundamental absorption edge at excitation of nonequilibrium charge carriers in them has been investigated. A broad spectrum of various actions upon a semiconductor—photoexcitation, contact injection, magnetoconcentration effect—has been used for the first time for modulation of the emissivity of crystals under isothermal conditions. Spectral, field, temperature and coordinate dependencies of the thermal emission as well as its transient characteristics at a pulsed excitation have been measured. It is shown that a considerable modulation of the thermal emission in a semiconductor can be obtained without a temperature change, through changing its emissivity alone. A number of features of the thermal emission in the region under consideration has been revealed: a spectral maximum which position depends on the optical thickness of the crystal, a kinetics delay effect, etc. It has been established that the thermal emission of an excited semiconductor can be used as a means for determining various parameters of a material. Experiments were carried out on Ge, Si plates and Ge diode structures at 310 ⩽ T ⩽ 350 K.