Wavelength-selective photodetector - including cut-off filter layer, used esp. in laser measuring processes

摘要

A wavelength-selective photodetector has a transparent active layer contg. a semiconductor junction, electrodes arranged on both sides of the active, at least one of the electrodes being transparent, and a cut-off filter with a selected cut-off wavelength (lambda k) located in front of the transparent electrode in the light incidence direction. The incident light is subject to multiple reflection within the active layer resulting in interference with a max. value (lambda max) greater than the selected cut-off wavelength in the longer wavelength region of decreasing sensitivity of the active layer. Prodn. of the photodetector involves (i) producing a smooth transparent electrode layer (thin conductive oxide layer) on a transparent substrate; (ii) depositing an amorphous photoconductive active layer by glow discharge; (iii) producing a back face metal electrode on the active layer by vapour or sputter deposition; (iv) depositing an undoped amorphous semiconductor layer on the opposite surface of the substrate from the thin conductive oxide layer; and (v) producing an arrangement for conducting away and amplifying current generated in the active layer. USE/ADVANTAGE - The photodetector is used esp. in optical measuring processes employing coherent, esp. laser light. It is unaffected by room lighting or daylight, has a narrow band of 500-1000 nm, and is simple and inexpensive to mfr.