Light-emitting component, print head, image forming apparatus and method of manufacturing light-emitting component

1. A light-emitting component comprising:

a plurality of light-emitting thyristors, each configured with a semiconductor layer stack in which a first semiconductor layer of a first conduction type, a second semiconductor layer of a second conduction type, which is different from the first conduction type, a third semiconductor layer of the first conduction type and a fourth semiconductor layer of the second conduction type are laminated in order, each of the plurality of light-emitting thyristors emitting light at a predetermined wavelength in an ON state;

a plurality of transfer thyristors, each configured with the semiconductor layer stack, the plurality of transfer thyristors shifting to the ON state in order so as to transfer the ON state, to thereby set corresponding light-emitting thyristors in a light-enabled state in the plurality of light-emitting thyristors; and

a plurality of coupling transistors, each configured with the first semiconductor layer, the second semiconductor layer and the third semiconductor layer in the semiconductor layer stack, provided to couple a former transfer thyristor and a latter transfer thyristor that are adjacent in order that the plurality of transfer thyristors sequentially shift to the ON state, and shifting to the ON state affected by the former transfer thyristor shifting to the ON state, the first semiconductor layer and the second semiconductor layer of each coupling transistor being continued to the first semiconductor layer and the second semiconductor layer of the former transfer thyristor and the third semiconductor layer of each coupling transistor being continued to the third semiconductor layer of the former transfer thyristor with a thickness to be depleted in a state where no voltage is applied.

2. The light-emitting component according to claim 1 , wherein the third semiconductor layer is configured with a third semiconductor layer lower layer on a side of the second semiconductor layer and a third semiconductor layer upper layer on a side of the fourth semiconductor layer, an impurity concentration of the third semiconductor layer upper layer is higher than that of the third semiconductor layer lower layer, the third semiconductor layer lower layer has a thickness depleted in a state where no voltage is applied, and part of the third semiconductor layer lower layer in a thickness direction on the second semiconductor layer is continued between the former transfer thyristor and the coupling transistor coupled thereto in the former transfer thyristors in the plurality of transfer thyristors and the plurality of coupling transistors.

3. A print head comprising:

a light-emitting unit including:

a plurality of light-emitting thyristors, each configured with a semiconductor layer stack in which a first semiconductor layer of a first conduction type, a second semiconductor layer of a second conduction type, which is different from the first conduction type, a third semiconductor layer of the first conduction type and a fourth semiconductor layer of the second conduction type are laminated in order, each of the plurality of light-emitting thyristors emitting light at a predetermined wavelength in an ON state;

a plurality of transfer thyristors, each configured with the semiconductor layer stack, the plurality of transfer thyristors shifting to the ON state in order so as to transfer the ON state, to thereby set corresponding light-emitting thyristors in a light-enabled state in the plurality of light-emitting thyristors; and

a plurality of coupling transistors, each configured with the first semiconductor layer, the second semiconductor layer and the third semiconductor layer in the semiconductor layer stack, provided to couple a former transfer thyristor and a latter transfer thyristor that are adjacent in order that the plurality of transfer thyristors sequentially shift to the ON state, and shifting to the ON state affected by the former transfer thyristor shifting to the ON state, the first semiconductor layer and the second semiconductor layer of each coupling transistor being continued to the first semiconductor layer and the second semiconductor layer of the former transfer thyristor and the third semiconductor layer of each coupling transistor being continued to the third semiconductor layer of the former transfer thyristor with a thickness to be depleted in a state where no voltage is applied; and

an optical unit that forms an image with light emitted from the light-emitting unit.

4. An image forming apparatus comprising:

an image carrier;

a charging unit that charges the image carrier;

an exposure unit that includes a light-emitting section and exposes the image carrier charged by the charging unit with light emitted by the light-emitting section through an optical section, the light-emitting section including:

a plurality of light-emitting thyristors, each configured with a semiconductor layer stack in which a first semiconductor layer of a first conduction type, a second semiconductor layer of a second conduction type, which is different from the first conduction type, a third semiconductor layer of the first conduction type and a fourth semiconductor layer of the second conduction type are laminated in order, each of the plurality of light-emitting thyristors emitting light at a predetermined wavelength in an ON state;

a plurality of transfer thyristors, each configured with the semiconductor layer stack, the plurality of transfer thyristors shifting to the ON state in order so as to transfer the ON state, to thereby set corresponding light-emitting thyristors in a light-enabled state in the plurality of light-emitting thyristors; and

a plurality of coupling transistors, each configured with the first semiconductor layer, the second semiconductor layer and the third semiconductor layer in the semiconductor layer stack, provided to couple a former transfer thyristor and a latter transfer thyristor that are adjacent in order that the plurality of transfer thyristors sequentially shift to the ON state, and shifting to the ON state affected by the former transfer thyristor shifting to the ON state, the first semiconductor layer and the second semiconductor layer of each coupling transistor being continued to the first semiconductor layer and the second semiconductor layer of the former transfer thyristor and the third semiconductor layer of each coupling transistor being continued to the third semiconductor layer of the former transfer thyristor with a thickness to be depleted in a state where no voltage is applied;

a developing unit that develops an electrostatic latent image formed on the image carrier by exposure of the exposure unit; and

a transfer unit that transfers an image developed on the image carrier onto a transferred body.

5. A method of manufacturing a light-emitting component including a plurality of light-emitting thyristors, a plurality of transfer thyristors and a plurality of coupling transistors, the method comprising:

forming a semiconductor layer stack by laminating a first semiconductor layer, a second semiconductor layer, a third semiconductor layer and a fourth semiconductor layer in order, by which the plurality of light-emitting thyristors and the plurality of transfer thyristors are configured;

forming the plurality of coupling transistors by performing etching on a partial region of the fourth semiconductor layer to expose the third semiconductor layer;

separating the plurality of transfer thyristors and the plurality of coupling transistors by performing etching on a partial region of the third semiconductor layer to leave a thickness to be depleted in a state where no voltage is applied in a case of shallowest etching; and

performing etching to reach the first semiconductor layer and forming a plurality of island regions, each configured by combining each of the plurality of light-emitting thyristors, each of the plurality of transfer thyristors and each of the plurality of coupling transistors.