Electrical Properties of Semiconductor Photodiodes with Semitransparent Films

High speed photodiodes with semitransparent film-semiconductor junctions, which behave as Schottky barriers, are designed and prepared. The optimized width of the depletion layer of the photodiode is calculated for the selected cut-off frequency. The relations between transmittance and sheet resistivity are studied with some films of semiconducting compounds, which affect the gain and response time of photodiodes. The photodiodes, fabricated by the deposition of the semitransparent films of CdS or CU2Se on Si, have high frequency response and the cut-off frequency of Cu2Se-n.Si photodiodes is higher than 4 GHz.