| 摘要 |
PROBLEM TO BE SOLVED: To lower the perfect depletion voltage by applying all PIN photodiodes provided on the same semiconductor substrate with a reverse voltage higher than the perfect depletion voltage thereby making thin a high resistance layer for forming a depletion layer. SOLUTION: When a reverse voltage is applied to a PIN photodiode, a depletion layer 28 begins to be formed on an N type semiconductor substrate 21 starting from a P+ type impurity region 22 and steady state is settled when the depletion layer 28 eventually reaches an N+ type impurity region 23. In view point of capacity-reverse voltage characteristics, the capacity decreases as the reverse voltage increases and becomes constant at some reverse voltage. The capacity is substantially invariant when the reverse voltage is increased furthermore and the reverse voltage when the depletion layer 28 reaches the N+ type impurity region 23 is referred to perfect depletion voltage. Leak current between adjacent PIN photodiodes in a multi-channel PIN photodiode can thereby be reduced by a simple method.
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