Light detection device and distance measurement apparatus

A distance measurement apparatus comprising:

• an optical system;
• a light detection device;
• and
• a signal processing circuit that calculates a distance to a measurement object on a basis of an output signal from the light detection device, wherein
• the light detection device includes
• a semiconductor substrate that includes a first surface and a second surface opposed to each other, and includes a pixel array in which a plurality of pixels is disposed in an array;
• a semiconductor layer that is provided on a side of the first surface of the semiconductor substrate;
• a light receiver that is provided inside the semiconductor substrate for each of the pixels, and generates carriers corresponding to a received light amount by photoelectric conversion;
• a multiplier that includes a first conduction-type region and a second conduction-type region sequentially stacked on the side of the first surface, at least the second conduction-type region being provided in the semiconductor layer, and that performs avalanche multiplication on the carriers generated by the light receiver;
• a first electrode that is provided on the side of the first surface, and is electrically coupled to the light receiver;
• a second electrode that is provided on the side of the first surface, and is electrically coupled to the multiplier;
• an insulating layer disposed on the side of the first surface of the semiconductor substrate, the semiconductor layer being embedded in the insulating layer for each of the pixels;
• and
• a reflection layer that is provided in the insulating layer so as to surround the semiconductor layer for each of the pixels,
• wherein the reflection layer is split, a first end of the reflection layer is electrically coupled to the second electrode, and a second end of the reflection layer is electrically coupled to a readout circuit that reads out carriers multiplied by the multiplier.