The standard time of flight technique is modified to analyse the internal field profiles in hydrogenated amorphous silicon or amorphous alloys devices. The spatial resolution of the field can be better than a thousand angstroms.
With this method the internal field profile in a Schottky structure, built in the sandwich geometry Pt/a-SiGe:H/Cr, was studied. The field profile is found to decrease exponentially with the distance to the Pt/a-SiGe. We also underline the non-ohmic behaviour of the a-SiGe/Cr interface. The shape of the internal field along the intrinsic zone in P-I-N devices is also studied by the same method.
The variations of the field profiles in both devices (Schottky and P-IN) with various applied DC biases is presented.