An Amorphous Silicon Photoconductor for UV Detection

An amorphous silicon photoconductor to detect wavelengths between 180 nm to 550 nm without scintillator is presented. The photoconductor is based on a coplanar configuration of the electrodes, similar to measurement structures to determine material characteristics of amorphous layers, e.g. for the C onstant Photocurrent M ethod (CPM). After passing through a thin transparent passivation layer, the incident radiation is directly absorbed in the intrinsic a-Si:H material. The carrier collecting electrical field is applied perpendicular to the incoming light. Test structures have been fabricated with 80 nm thick sputtered chromium contacts on top of a 60 nm carbonized hydrogenated i-layer and a Si x N x passivation layer with a thickness of about 36 nm. The spacing between the Schottky contacts is varied between 3 μm and 100 μm. They are deposited on top or below the a-SiC:H layer. First experiments with this simple coplanar design show that with an increasing voltage a shift towards UV wavelengths can be observed. The new UV detector is applicable in the field of TFA image sensors ( T hin Film on A SIC) and in the new Lab-on-a-Chip concept presently under development at the institute for microsystem technologies.