Photoelectric conversion device and imaging device
A photoelectric conversion device includes: a light absorption layer that has a light entrance surface and a compound semiconductor material; a first electrode provided for each of the pixels, in opposed relation to an opposite surface to the light entrance surface; a first semiconductor layer of a first conductive type, with a bandgap energy larger than bandgap energy of the light absorption layer and that is provided between the light absorption layer and the first electrode; a second semiconductor layer of a second conductive type, with a bandgap energy larger than the bandgap energy of the light absorption layer and that is provided between the first semiconductor layer and the light absorption layer; and a first diffusion region of the second conductive type, in which the first diffusion region is provided between adjacent ones of the pixels and across the second semiconductor layer and the light absorption layer.
1. A photoelectric conversion device, comprising:
a light absorption layer that has a light entrance surface and includes a compound semiconductor material;
a first electrode provided for each of pixels, in opposed relation to an opposite surface to the light entrance surface of the light absorption layer;
a first semiconductor layer of a first conductive type, the first semiconductor layer having bandgap energy larger than bandgap energy of the light absorption layer and being provided between the light absorption layer and the first electrode;
a second semiconductor layer of a second conductive type, the second semiconductor layer having bandgap energy larger than the bandgap energy of the light absorption layer and being provided between the first semiconductor layer and the light absorption layer; and
a first diffusion region of the second conductive type, the first diffusion region being provided between adjacent ones of the pixels, and being provided across the second semiconductor layer and the light absorption layer.
2. The photoelectric conversion device according to claim 1 , wherein
the first diffusion region is provided in a lattice shape in plan view.
3. The photoelectric conversion device according to claim 1 , further comprising
an electrical charge collection layer that is provided between the second semiconductor layer and the light absorption layer, and temporarily accumulates electrical charges generated in the light absorption layer.
4. The photoelectric conversion device according to claim 1 , further comprising
a barrier alleviation layer that is provided between the second semiconductor layer and the light absorption layer, and alleviates a band offset barrier between the second semiconductor layer and the light absorption layer.
5. The photoelectric conversion device according to claim 1 , wherein
the second semiconductor layer is configured to cause avalanche amplification of electrical charges generated in the light absorption layer.
6. The photoelectric conversion device according to claim 5 , further comprising
an electric field descending layer that is provided between the second semiconductor layer and the light absorption layer, and restrains propagation of an electric field from the second semiconductor layer to the light absorption layer.
7. The photoelectric conversion device according to claim 1 , wherein
the first semiconductor layer and the second semiconductor layer have a first groove that separates the adjacent ones of the pixels.
8. The photoelectric conversion device according to claim 7 , wherein
the first groove extends in the light absorption layer.
9. The photoelectric conversion device according to claim 7 , further comprising
an insulating film that is provided from a front surface of the first semiconductor layer to a sidewall of the first groove, covers a sidewall of the first semiconductor layer, and extends over a portion of a sidewall of the second semiconductor layer.
10. The photoelectric conversion device according to claim 7 , further comprising
a light-shielding member fitted into the first groove.
11. The photoelectric conversion device according to claim 1 , further comprising
a second electrode provided in opposed relation to the light entrance surface of the light absorption layer.
12. The photoelectric conversion device according to claim 11 , wherein
the second electrode is provided over an entirety of the light entrance surface of the light absorption layer.
13. The photoelectric conversion device according to claim 11 , wherein
the second electrode includes a light-shielding material.
14. The photoelectric conversion device according to claim 13 , further comprising
a second diffusion region of the second conductive type, the second diffusion region being provided between the adjacent ones of the pixels, on side of the light absorption layer on which the light entrance surface is disposed.
15. The photoelectric conversion device according to claim 14 , wherein
the light entrance surface of the light absorption layer has a second groove, and
the second diffusion region is provided near the second groove.
16. The photoelectric conversion device according to claim 1 , further comprising
a third electrode electrically coupled to the first diffusion region.
17. The photoelectric conversion device according to claim 15 , further comprising
a fourth electrode electrically coupled to the second diffusion region,
wherein the fourth electrode is fitted into in the second groove.
18. The photoelectric conversion device according to claim 1 , further comprising
a coating film that covers the first diffusion region.
19. The photoelectric conversion device according to claim 18 , wherein
the coating film includes electrical charges of the first conductive type.
20. An imaging device, comprising:
a light absorption layer that has a light entrance surface and includes a compound semiconductor material;
a first electrode provided for each of pixels, in opposed relation to an opposite surface to the light entrance surface of the light absorption layer;
a first semiconductor layer of a first conductive type, the first semiconductor layer having bandgap energy larger than bandgap energy of the light absorption layer and being provided between the light absorption layer and the first electrode;
a second semiconductor layer of a second conductive type, the second semiconductor layer having bandgap energy larger than the bandgap energy of the light absorption layer and being provided between the first semiconductor layer and the light absorption layer; and
a first diffusion region of the second conductive type, the first diffusion region being provided between adjacent ones of the pixels, and being provided across the second semiconductor layer and the light absorption layer.