Mechanisms limiting the internal quantum efficiency in various types of oxidehyphen;passivated silicon photodiodes are discussed. It is argued that unit internal quantum efficiency is achievable in metallurgical junction, oxidehyphen;n+hyphen;phyphen;p+photodiodes, if it is achievable in the inversion layer of induced junction diodes of the same type. Measurements of the variation in response of the latter type of photodiode under both oxide bias and reverse bias are described. The results indicate that 100percnt; collection of the minority carriers generated in the inversion layer is achieved for sufficiently low flux levels. Implantation in the oxide of Na+ions to augment the trapped positive charge increases the maximum flux level at which 100percnt; collection is observed.
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