Ambipolar drift-length measurement in amorphous hydrogenated silicon using the steady-state photocarrier grating technique

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Abstract
The steady-state photocarrier grating technique, which yields the ambipolar diffusion length in photoconductive insulators, can also yield the ambipolar drift length if the measurements are carried out as a function of electric field. This characteristic length in turn gives a lower bound on the experimental value of the minority-carrier drift length. From measurements of both the diffusion and drift length on the same sample of amorphous hydrogenated silicon it is found that the ratio between the ambipolar diffusion coefficient and the ambipolar mobility is equal to about twice the classical Einstein value.