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.

• Received 29 September 1986

DOI:https://doi.org/10.1103/PhysRevB.34.9031