Light-emitting element, method of manufacturing light-emitting element, self-scanning light-emitting element array, optical writing head, and image forming apparatus
View Patent ↗Provided is a light-emitting element including a semiconductor substrate, an island structure formed on the semiconductor substrate and including at least a current confining layer and p-type and n-type semiconductor layers, a light-emitting thyristor formed in the island structure and having a pnpn structure, and a shift thyristor formed in the island structure and having a pnpn structure, wherein the island structure includes a first side surface having a first depth such that the first side surface does not reach the current confining layer in a formation region of the shift thyristor and a second side surface having a second depth such that the second side surface reaches at least the current confining layer in a formation region of the light-emitting thyristor, and an oxidized region selectively oxidized from the second side surface is formed in the current confining layer in the formation region of the light-emitting thyristor.
1. A light-emitting element comprising:
a semiconductor substrate;
an island structure formed on the semiconductor substrate and including at least a current confining layer and p-type and n-type semiconductor layers;
a light-emitting thyristor formed in the island structure and having a pnpn structure; and
a shift thyristor formed in the island structure and having a pnpn structure, wherein
the island structure includes a first side surface having a first depth such that the first side surface does not reach the current confining layer in a formation region of the shift thyristor and a second side surface having a second depth such that the second side surface reaches at least the current confining layer in a formation region of the light-emitting thyristor, and
an oxidized region selectively oxidized from the second side surface is formed in the current confining layer in the formation region of the light-emitting thyristor.
2. The light-emitting element according to claim 1 , wherein
a cathode layer of the light-emitting thyristor is separated from a cathode layer of the shift thyristor,
a current confining layer including an oxidized region and a non-oxidized region is present immediately below the cathode layer of the light-emitting thyristor, and
a current confining layer of the non-oxidized region is present immediately below the cathode layer of the shift thyristor.
3. The light-emitting element according to claim 1 , wherein
the island structure has a rectangular shape having four side surfaces,
the first side surface includes one side surface and two partial side surfaces adjacent thereto, and the shift thyristor is formed in a region surrounded by the three side surfaces, and
the second side surface includes one side surface and two partial side surfaces adjacent thereto, and the light-emitting thyristor is formed in a region surrounded by the three side surfaces.
4. The light-emitting element according to claim 2 , wherein
the island structure has a rectangular shape having four side surfaces,
the first side surface includes one side surface and two partial side surfaces adjacent thereto, and the shift thyristor is formed in a region surrounded by the three side surfaces, and
the second side surface includes one side surface and two partial side surfaces adjacent thereto, and the light-emitting thyristor is formed in a region surrounded by the three side surfaces.
5. The light-emitting element according to claim 1 , wherein
the current confining layer is formed in an anode layer of the light-emitting thyristor and the shift thyristor,
the first side surface has a first depth such that the first side surface does not reach the current confining layer in the anode layer, and
the second side surface has a second depth such that the second side surface reaches the current confining layer in the anode layer.
6. The light-emitting element according to claim 2 , wherein
the current confining layer is formed in an anode layer of the light-emitting thyristor and the shift thyristor,
the first side surface has a first depth such that the first side surface does not reach the current confining layer in the anode layer, and
the second side surface has a second depth such that the second side surface reaches the current confining layer in the anode layer.
7. The light-emitting element according to claim 1 , wherein
the first side surface is a wet-etching surface which is wet-etched when forming the island structure, and
the second side surface is a dry-etching surface which is dry-etched when forming the island structure.
8. The light-emitting element according to claim 1 , wherein
the light-emitting element further comprises:
a semiconductor multilayer reflecting mirror disposed between the pnpn structure of the light-emitting thyristor and the semiconductor substrate.
9. The light-emitting element according to claim 1 , wherein
a diode is formed in the island structure in a region of a pn layer separated from the light-emitting thyristor and the shift thyristor, and
an anode layer of the diode is shared with the gates of the light-emitting thyristor and the shift thyristor.
10. A method of manufacturing a light-emitting element in which a plurality of island structures including at least a current confining layer and p-type and n-type semiconductor layers are formed on a semiconductor substrate, and at least a light-emitting thyristor having a pnpn structure and a shift thyristor having a pnpn structure are formed in one island structure, the method comprising:
when forming the island structure, forming a first side surface having a first depth such that the first side surface does not reach the current confining layer in a formation region of the shift thyristor and forming a second side surface having a second depth such that the second side surface reaches at least the current confining layer in a formation region of the light-emitting thyristor; and
forming an oxidized region selectively oxidized from the second side surface in the current confining layer in the formation region of the light-emitting thyristor.
11. The method according to claim 10 , wherein
the first and second side surfaces are formed by two steps of etching.
12. The method according to claim 10 , wherein
the first side surface is formed by wet-etching, and the second side surface is formed by dry-etching.
13. The method according to claim 12 , wherein
the first side surface has a first depth such that the first side surface reaches at least an active region of the light-emitting thyristor and the shift thyristor.
14. The method according to claim 12 , wherein
the island structure includes a semiconductor multilayer reflecting mirror formed on the semiconductor substrate,
the semiconductor multilayer reflecting mirror includes a plurality of pairs of AlGaAs layers having different Al contents,
the current confining layer is an AlAs layer or an AlGaAs layer, and
the second side surface has a second depth such that the second side surface reaches at least the semiconductor multilayer reflecting mirror.
15. The method according to claim 10 , wherein
a first etching step of forming the first side surface is performed, and then, a second etching step of forming the second side surface is performed.
16. The method according to claim 10 , wherein
a first etching step of forming the second side surface is performed, and then, a second etching step of forming the first side surface is performed.
17. The method according to claim 10 , wherein
the island structure has a rectangular shape having four side surfaces,
the second side surface includes one side surface and two partial side surfaces adjacent thereto, and
the current confining layer is selectively oxidized from the three side surfaces.
18. A self-scanning light-emitting element array comprising:
a plurality of the light-emitting elements according to claim 1 , wherein
a first transfer signal is applied to a cathode layer of the shift thyristor of each of odd-numbered island structures,
a second transfer signal different from the first transfer signal is applied to a cathode layer of the shift thyristor of each of even-numbered island structures, and
the gates of the shift thyristors of the adjacent island structures are electrically connected by the diode.
19. An optical writing head using the light-emitting element array according to claim 18 .
20. An image forming apparatus comprising the optical writing head according to claim 19 .