Peculiarities of Photovoltage Formation across p-n Junction under Illumination of Laser Radiation

Photovoltage formation across Si and GaAs p-n junctions exposed to laser radiation is experimentally investigated. When the photon energy is lower than semiconductor forbidden energy gap, the photovoltage is found to consist of two components, U=Uf+ Uph. The first one Uf is fast having polarity of thermoelectromotive force of hot carriers. The second one Uph is slow component of opposite polarity, and it is caused by electron-hole pair generation due to two-photon absorption. Uph was shown to decrease with the rise of radiation wavelength due to diminution of two-photon absorption coefficient with wavelength. Predominance of each separate component in the formation of the net photovoltage depends on both laser wavelength and intensity.