Ambipolar diffusion length measurements in hydrogenated amorphous silicon

Abstract
Many studies have been devoted in recent years to the experimental determination of the diffusion length of the minority carriers in hydrogenated amorphous silicon. The most popular method for this purpose was the surface photovoltage technique while the most novel method is the photocarrier grating technique. In the present work we report the first experimental comparison of the two methods. It is found that the first method yields values which are typically twice as large as those of the second method. This disagreement can be explained by the recent theoretical studies of the two methods. On the other hand, the present results seem to indicate how some more information on the electronic structure of the above material can be derived by future comparisons between theoretical and experimental results.