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Silicon photodiodes, photoelectric transistor, and other silicon photoelectric devices have many advantages such as high response speed, good linearity of current vs. illuminance, high quantum efficiency over a wide spectrum range, and long life. However, a whole class of photoelectric detectors is based on low dark current. For example, silicon vidicon, silicon blue sensitive photodiode (SPD) and its integrated amplifier, and silicon photoelectric array have special features which depend on dark current. The dark current must be kept low enough. The reduction of the dark current was investigated by the author in making SPD. Dark current can be ascribed to the following causes: diffusion current, extended defects and generation current on the surface and junction depleted layer. The diffusion current is the unavoidable contribution to the dark current. Extended defects in active zones once decorated by metal atoms bring about an increase of dark current. Generation current plays an important part in dark current. Therefore, it is important to reduce density of the generation center and metal atom in surface and junction to obtain low dark current. HCl treatment, gettering techniques, etc., are the efficient methods. The author has improved HCl oxidation, intrinsic gettering, phosphorus diffusion gettering, and Si3N4 film deposition to obtain further reduction of dark current.
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