Photodetection device, photodetection system, and moving body

A photodetection device comprising:

• a semiconductor substrate including a first surface and a second surface opposed to the first surface;
• and
• a pixel disposed on the semiconductor substrate, the pixel including an avalanche diode that includes
• at a first depth of the semiconductor substrate, a first semiconductor region having a first conductivity type same as a signal electric charge, and a second semiconductor region of a second conductivity type being in contact with the first semiconductor region and having a polarity different from the first conductivity type,
• at a second depth deeper than the first depth from the first surface of the semiconductor substrate, a third semiconductor region and a fourth semiconductor region being in contact with the third semiconductor region and having a concentration of an impurity of the second conductivity type lower than the second semiconductor region,
• a fifth semiconductor region disposed at a third depth deeper than the second depth from the first surface of the semiconductor substrate,
• a sixth semiconductor region is provided between the first semiconductor region and the second semiconductor region, and
• in a plan view, the avalanche diode is arranged such that
• the first semiconductor region overlaps at least a part of the third semiconductor region,
• the second semiconductor region overlaps at least a part of the fourth semiconductor region, and
• the third semiconductor region and the fourth semiconductor region overlap the fifth semiconductor region, wherein
• a height of a potential with respect to a signal electric charge in the third semiconductor region is lower than a height of a potential with respect to the signal electric charge in the fourth semiconductor region, and
• a height of a potential with respect to the signal electric charge in the fourth semiconductor region is higher than a height of a potential with respect to the signal electric charge in the fifth semiconductor region.