Light detection apparatus, photoelectric conversion system, and movable body

A light detection apparatus comprising:

• a first semiconductor region having a first conductivity type in which carriers having a first polarity that is the same polarity as that of a signal charge are set as majority carriers;
• a second semiconductor region having a second conductivity type in which carriers having a second polarity are set as majority carriers;
• and
• a third semiconductor region having the first conductivity type where the signal charge is transferred from the first semiconductor region,
• wherein a reverse bias voltage for causing avalanche multiplication of the signal charge is applied to the second semiconductor region and the third semiconductor region,
• a potential barrier having a height lower than the reverse bias voltage with respect to the signal charge in the first semiconductor region is formed between the first semiconductor region and the third semiconductor region, and
• the signal charge is accumulated in the first semiconductor region by forming the potential barrier,
• wherein the light detection apparatus comprises a control unit configured to transfer the signal charge in the first semiconductor region to the third semiconductor region in a manner that the height of the potential barrier is controlled;
• and
• a circuit unit configured to count the number of generation times of an avalanche current generated by the avalanche multiplication.