The efficiency of the yield of second harmonics in nonpolar nondegeneratesemiconductors is estimated by a simple method without using the Boltzmanntransport equation. For n-Ge and n-Si, the efficiency of 4 to 5 percent isobtained for the optimum dc bias field, about Vo/μo, i.e., the ratio of thesaturation velocity to the low-field mobility. In order to give this estimation,a hyperbolic equation is assumed, which may describe the nonlinear velocityelectricfield relation from the ohmic region up to the saturation region inthe temperature range between 77 and 300K. The velocity-field characteristic,by this approximation is found to be in good agreement with the experiment.It is suggested that the optimum field for n-Ge is lower than that for n-Si,and that the optimum bias field in both n-Ge and n-Si is decreased in thetemperature range of interest as the temperature is lowered.
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