Optical rectification and photon drag in n-type gallium phosphide

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Abstract
Optical rectification and the photon-drag effect have been studied in n-type gallium phosphide at various wavelengths between 1.06 and 10.8 mu m. A pronounced peak occurs in both quantities near 3 mu m, corresponding to transitions between the lowest point in the conduction band, near X1, and the minimum at X3. It is shown that the optical rectification is primarily due to free electrons and the spectrum explained in terms of the band structure of GaP proposed by Lawaetz. At this peak, the optical rectification coefficient of n-type GaP containing 2.4*1016 electrons cm-3 is the largest ever observed. The results also represent the first observation of a resonance effect in optical rectification and the first in which free carriers play a major role.