JP2014038934A - Light-emitting element, light source head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element that suppresses a driving voltage compared with the case not having the present configuration, a light source head, and an image forming apparatus.SOLUTION: In a light-emitting element 100, a band gap of a light-emitting layer 126 is smaller than band gaps of an anode layer 122, an n-type gate layer 124, a p-type gate layer 128, and a cathode layer 130, and functions as a recombination layer for carriers to be recombined. A coupling diode 106 is formed between the p-type gate layer 128 and the n-type gate layer 124. Accordingly, the coupling diode 106 has a small diffusion potential, so that a driving voltage of the light-emitting element 100 can be suppressed.

Description

  The present invention relates to a light emitting element, a light source head, and an image forming apparatus.

  In Patent Document 1, a. Arranging a plurality of light emitting elements whose threshold voltage or threshold current can be controlled by light from the outside, one-dimensionally, two-dimensionally or three-dimensionally; b. A structure in which at least a part of light generated from each light emitting element is incident on another light emitting element in the vicinity of each light emitting element; c. A light emitting element array is described in which a clock line for applying a voltage or current from the outside is connected to each light emitting element.

  In Patent Document 2, a. Arranging a plurality of light emitting elements each having a control electrode whose threshold voltage or threshold current can be controlled from the outside, one-dimensionally, two-dimensionally or three-dimensionally; b. Forming a network wiring in which the control electrodes of each light emitting element are electrically connected to the control electrodes of at least two light emitting elements located in the vicinity; c. In a light emitting element array in which a clock line for applying voltage or current from the outside is connected to each light emitting element, as the electrical means, a current amount in any direction in which a voltage drop in the electrical means flows to the electrical means There is described a light-emitting element array characterized by using a coupling element that is constant without depending on the above.

Japanese Patent Laid-Open No. 01-238962

Japanese Patent Laid-Open No. 03-256372

  An object of the present invention is to provide a light emitting element, a light source head, and an image forming apparatus in which a driving voltage is suppressed as compared with a case where this configuration is not provided.

  In order to achieve the above object, a light emitting device of the present invention is formed on a first gate layer of a second conductivity type formed in a first region on an anode layer of a first conductivity type, on the first gate layer. A light emitting layer having a smaller band gap than the first gate layer; a second gate layer of a first conductivity type having a larger band gap than the light emitting layer formed on the light emitting layer; and formed on the second gate layer. Light emission having the first cathode layer of the second conductivity type formed, the first contact layer of the second conductivity type formed on the first cathode layer, and the first cathode electrode formed on the first contact layer And the first gate layer formed in the second region on the anode layer, the light emitting layer formed on the gate layer, the second gate layer formed on the light emitting layer, the second Second cathode of the second conductivity type formed on the gate layer A transfer portion having a second layer of the second conductivity type formed on the second cathode layer, a second cathode layer formed on the second contact layer, and a second portion on the anode layer. The first gate layer formed in three regions, the first gate electrode of the second conductivity type formed on the first gate layer, the light emitting layer formed on the first gate layer, on the light emitting layer And a coupling portion having a second gate electrode of the first conductivity type formed on the second gate layer.

  In the light-emitting element of the present invention, the first region and the second region are provided continuously, and the first region, the second region, and the third region are provided separately from each other. It may be.

  In the light emitting element of the present invention, the first region, the second region, and the third region may be provided continuously.

  The light source head of the present invention includes a plurality of light emitting elements of the present invention as a light source, and the coupling part of the light emitting elements electrically couples the transfer part of the light emitting element and the transfer part of the other light emitting element. Is.

  The image forming apparatus of the present invention includes a photosensitive member, a charging unit for charging the surface of the photosensitive member, and a light source head of the present invention, and forms an electrostatic latent image on the surface of the photosensitive member charged by the charging unit. In order to accomplish this, an exposure unit that exposes light emitted from the light source head, a developing unit that develops the electrostatic latent image formed by the exposure unit, and the electrostatic latent image developed by the developing unit are fixed. Fixing means.

  According to the first, fourth, and fifth aspects of the invention, the drive voltage can be suppressed as compared with the case where the present configuration is not provided.

  According to invention of Claim 2, compared with the case where it does not have this structure, it suppresses that a light emission part, a transfer part, and a coupling | bond part mutually interfere mutually.

  According to the third aspect of the present invention, the manufacturing process becomes easier as compared with the case where the present configuration is not provided.

1 is a schematic configuration diagram showing an outline of an example of an image forming apparatus according to the present embodiment. It is a schematic sectional drawing which shows the internal structure of an example of the light source head which concerns on this Embodiment. It is a perspective view which shows the external appearance of an example of the semiconductor light-emitting element array which concerns on this Embodiment. It is a schematic diagram which shows an example of the chip | tip of this Embodiment. It is an equivalent circuit diagram which shows an example of the chip | tip of this Embodiment. It is a top view which shows schematic structure of an example of the light emitting element array provided with two or more light emitting elements of 1st Embodiment. It is sectional drawing which shows the X-X 'cross section of the light emitting element array shown in FIG. It is sectional drawing which shows the Y-Y 'cross section of the light emitting element array shown in FIG. It is explanatory drawing which shows a specific example of Al composition and film thickness of each layer of the light emitting element of 1st Embodiment. It is a top view which shows schematic structure of an example of the light emitting element array provided with two or more light emitting elements of 2nd Embodiment. It is sectional drawing which shows the X-X 'cross section of the light emitting element array shown in FIG. It is sectional drawing which shows schematic structure of an example of the conventional light emitting thyristor. It is sectional drawing which shows the cross section of an example of the light emitting element which used the conventional light emitting thyristor shown in FIG. 12 for the light emission part.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an outline of an example of an image forming apparatus according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing the internal configuration of an example of the light source head of the present embodiment. FIG. 3 is a perspective view showing the appearance of an example of the light-emitting thyristor array according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 according to the present exemplary embodiment includes a photoconductor 12 that rotates at a constant speed in an arrow A direction.

  In order to form an electrostatic latent image on the surface of the photoconductor 12 around the photoconductor 12 along the rotation direction of the photoconductor 12, the charger 14 for charging the surface of the photoconductor 12, and the surface of the photoconductor 12 charged by the charger 14. A light source head 16 (exposure means) for exposing the toner image, a developing device 18 (developing means) for developing the electrostatic latent image with a developer to form a toner image, and transferring the toner image to a paper 28 (recording medium). A transfer body 20 (transfer means), a cleaner 22 for removing residual toner remaining on the photoconductor 12 after transfer, and an erase lamp 24 for discharging the photoconductor 12 to make the potential uniform are arranged in this order.

  That is, the surface of the photoconductor 12 is charged by the charger 14, and then a light beam is irradiated by the light source head 16 to form a latent image on the photoconductor 12. The light source head 16 is connected to a driving unit (not shown), and the lighting of the light emitting element 100 (light emitting unit 102) is controlled by the driving unit to emit a light beam based on image data. Yes.

  To the formed latent image, toner is supplied by the developing unit 18 to form a toner image on the photoreceptor 12. The toner image on the photoconductor 12 is transferred onto the conveyed paper 28 by the transfer body 20. The toner remaining on the photoconductor 12 after the transfer is removed by the cleaner 22, neutralized by the erase lamp 24, charged by the charger 14 again, and the same processing is repeated.

  On the other hand, the paper 28 onto which the toner image has been transferred is conveyed to a fixing device 30 (fixing means) composed of a pressure roller 30A and a heating roller 30B and subjected to a fixing process. As a result, the toner image is fixed and a desired image is formed on the paper 28. The paper 28 on which the image is formed is discharged out of the apparatus.

  Next, the configuration of the light source head 16 of the present embodiment will be described in detail. The light source head 16 of the present embodiment uses an SLED (Self-scanning LED). The SLED is obtained by integrating an LED array and a driving portion thereof, and includes a plurality of light emitting elements 100 having a light emitting unit 102 (described later in detail) having a thyristor structure. As shown in FIG. 2, a mounting board on which a light emitting element array 50 and a circuit (not shown) for supporting the light emitting element array 50 and supplying various signals for controlling the driving of the light emitting element array 50 are mounted. 52 and a rod lens array 54 (Selfoc is a registered trademark of Nippon Sheet Glass Co., Ltd.) such as a Selfox lens array.

  The mounting substrate 52 is disposed in the housing 56 with the mounting surface of the light emitting element array 50 facing the photoreceptor 12, and is supported by a plate spring 58.

  As shown in FIG. 3, the light emitting element array 50 includes, for example, a chip 62 configured by arranging a plurality of light emitting elements 100 along the axial direction of the photoconductor 12 according to the resolution in the axial direction. A plurality of light beams are arranged in series, and light beams are irradiated in the axial direction of the photosensitive member 12 with a predetermined resolution.

  In the present embodiment, an example in which a plurality of chips 62 are arranged in a one-dimensional manner in series is shown. However, the present invention is not limited to this, and the chips 62 may be arranged in a plurality of rows and arranged in a two-dimensional manner. For example, when arranged in a zigzag pattern, the plurality of chips 62 are arranged in a row so as to be aligned along the axial direction of the photoconductor 12 and are arranged in two rows with a certain interval in the direction intersecting the axial direction. Is done. Even when divided into a plurality of chips 62, each of the plurality of light emitting elements 100 is arranged such that the distance between the two light emitting elements 100 adjacent to each other in the axial direction of the photosensitive member 12 is substantially constant. ing.

  As shown in FIG. 2, the rod lens array 54 is supported by a holder 64 and forms an image of the light beam emitted from the light emitting unit 102 of each light emitting element 100 on the photoconductor 12.

  A schematic diagram of an example of the chip 62 is shown in FIG. Further, an equivalent circuit diagram of an example of the chip 62 is shown in FIG. On the chip 62, a light emitting unit 102 made of a light emitting thyristor, a transfer unit 104 made of a transfer thyristor, a coupling diode 106 for electrically coupling adjacent bit transfer units 104, a gate electrode of the light emitting unit 102, and A gate resistor 108 for connecting the gate electrode of the transfer unit 104 to the reference potential line Vg is provided for each bit.

  Although details will be described later, the anode electrodes of the light emitting unit 102 and the transfer unit 104 are connected to a substrate on the chip 62. The gate electrode is connected to the reference potential line Vg via the gate resistor 108. The cathode electrode of the light emitting unit 102 is connected to the transfer signal line φI. On the other hand, in the transfer unit 104, the transfer unit 104 having the cathode electrode connected to the transfer signal line φ1 and the transfer unit 104 having the cathode electrode connected to the transfer signal line φ2 are alternately arranged.

  Here, before describing the light emitting element 100 of the present embodiment in detail, first, the conventional light emitting element 100 will be described for comparison with the present embodiment.

In a light emitting thyristor having a double hetero structure using an Al _x Ga _1-x As-based semiconductor layer, generally, the Al composition of a gate layer functioning as a barrier layer is made higher than that of the light emitting layer so that the band gap is larger than that of the light emitting layer. It is necessary to spread. A cross-sectional view of a schematic configuration of an example of such a light emitting thyristor having a double hetero structure is shown in FIG. Here, as an example, a PNPN light-emitting thyristor is shown from the substrate side. FIG. 13 is a sectional view of a schematic configuration of an example of a conventional light-emitting element using the light-emitting thyristor shown in FIG. 12 as a light-emitting portion.

  A conventional light-emitting thyristor (light-emitting portion) 1102 shown in FIG. 12 is formed on a p-type GaAs substrate 1120, a p-type AlGaAs-based anode layer 1122, an n-type AlGaAs-based gate layer 1124, a light-emitting layer 1126, and a p-type. An AlGaAs gate layer 1128, an n-type AlGaAs cathode layer 1130, and an n-type GaAs contact layer 1132 are sequentially stacked.

  A cathode electrode 1140 is formed on the contact layer 1132. A p-type gate electrode 1142 is formed on the p-type gate layer 1128 from which the cathode layer 1130 has been removed to expose a part of the surface. An anode electrode 1146 is formed on the back surface of the substrate 1120 (the surface on which the anode layer 1122 is not provided). Further, an insulating film 1134 is formed in the emission region of the light emitting surface where the cathode electrode 1022 and the gate electrode 1020 are provided.

  The greater the difference between the Al composition of the light emitting layer 1126 and the Al composition of the n-type gate layer 1124 and p-type gate layer 1128, the greater the confinement of carriers to the light emitting layer 1126, and the higher the light output.

  In the conventional light emitting device 1100 using the light emitting thyristor (light emitting portion) 1102 using such a double hetero structure, when the Al composition of the p-type gate layer 1128 is increased, the gate resistance is increased and the coupled diode is increased. The operating voltage of 1106 is increased. The drive voltage for operating the light emitting element array provided with the light emitting element 1100 is increased by increasing the gate resistance (see FIGS. 4 and 5 and the gate resistor 108) and increasing the operating voltage of the coupling diode 1106.

  Next, the light emitting element 100 of the present embodiment will be described in detail. Hereinafter, as an example of the light emitting element 100 of the present embodiment, when the light emitting unit 102 and the transfer unit 104 and the coupling diode (coupling unit) 106 are provided apart from each other (first embodiment), A case where the light emitting unit 102, the transfer unit 104, and the coupling diode (coupling unit) 106 are continuously provided (second embodiment) will be described.

[First Embodiment]

  In this embodiment mode, a case where the light emitting unit 102 and the transfer unit 104 of the light emitting element 100 and the coupling diode (coupling unit) 106 are provided apart from each other will be described. Specifically, in this embodiment, the region where the light emitting unit 102 is provided on the anode layer 122 (first region) and the region where the transfer unit 104 is provided (second region) are continuous. The region where the coupling diode 106 is provided (third region) is separated.

FIG. 6 shows a top view of a schematic configuration of an example of a light emitting element array 50 (chip 62) provided with a plurality of light emitting elements 100 of the present embodiment. FIG. 7 shows a cross-sectional view of the light emitting element array 50 shown in FIG. Further, FIG. 8 shows a YY ′ cross-sectional view of the light emitting element array 50 shown in FIG. 6. Note that in this embodiment mode, the light-emitting element 100 is an Al _x Ga _1-x As-based PNPN type from the substrate side.

  The light emitting device 100 according to the present embodiment includes a p-type GaAs substrate 120, a p-type AlGaAs anode layer 122, an n-type AlGaAs n-type gate layer 124 (124A, 124B), and an undoped AlGaAs system. Light emitting layer 126 (126A, 126B), p-type AlGaAs-based p-type gate layer 128 (128A, 128B), n-type AlGaAs-based cathode layer 130 (130A, 130B), and n-type GaAs-based contact layer 132 (132A, 132B) are stacked.

  In addition, the light emitting element 100 of the present embodiment includes a cathode electrode 140 (140A, 140B), a p-type gate electrode 142 (142A, 142B, 142C), an n-type gate electrode 144, and an anode electrode 146. ing. The anode electrode 146 is provided on the back surface of the substrate 120 (the surface facing the side where the anode layer 122 is laminated).

  Specifically, the n-type gate layer 124A and the n-type gate layer 124B are provided separately on the anode layer 122. The light emitting layer 126A is provided on the n-type gate layer 124A, and the p-type gate layer 128A is provided on the light emitting layer 126A. On the p-type gate layer 128A, a cathode layer 130A and a cathode layer 130B are provided apart from each other, and a p-type gate electrode 142A is provided. A contact layer 132A is provided on the cathode layer 130A, and a cathode electrode 140A is provided on the contact layer 132A. A contact layer 132B is provided on the cathode layer 130B, and a cathode electrode 140B is provided on the contact layer 132B.

  On the other hand, a light emitting layer 126B and an n-type gate electrode 144 are provided on the n-type gate layer 124B. A p-type gate layer 128B is provided on the light emitting layer 126B, and a p-type gate electrode 142B and a p-type gate electrode 142C are provided on the p-type gate layer 128B.

  As materials for the cathode electrode 140, the p-type gate electrode 142, the n-type gate electrode 144, and the anode electrode 146, materials suitable for maintaining good ohmic contact with the semiconductor layer or the substrate 120 in contact with each other are used. Specific examples include gold (Au), an alloy of gold and germanium (AuGe), an alloy of gold and zinc (AuZn), nickel (Ni), and the like.

  In addition, the surface of the light emitting element 100 of this embodiment is in a region other than where the cathode electrode 140 (140A, 140B), the p-type gate electrode 142 (142A, 142B), and the n-type gate electrode 144 are formed. An insulating film 134 is provided. The insulating film 134 is an antireflection film having a function of preventing light reflection. Examples of the insulating film 134 include SiNx and the like.

  In this embodiment, the band gap of the anode layer 122 is Eg1, the band gap of the n-type gate layer 124 (124A, 124B) is Eg2, the band gap of the light emitting layer 126 (126A, 126B) is Eg3, and the p-type gate. When the band gap of the layer 128 (128A, 128B) is Eg4 and the band gap of the cathode layer 130 (130A, 130B) is Eg5, the following relationships (1) and (2) are satisfied.

  Eg3 <Eg2 ≦ Eg1 (1)

  Eg3 <Eg2 ≦ Eg5 (2)

  That is, in the light emitting element 100 of this embodiment, the band gap Eg3 of the light emitting layer 126 is any of the band gap Eg2 of the n-type gate layer 124, the band gap Eg4 of the p-type gate layer 128, and the band gap Eg5 of the cathode layer 130. Is smaller than

  In the light-emitting element 100 of the present embodiment, the band gap value is determined by the Al composition of each layer. In the case of an AlGaAs system, the band gap increases as the Al composition increases. As the Al composition x of the light emitting layer 126, 0 <x <0.2, and as the Al composition x of the n-type gate layer 124 and the light emitting layer 126, 0.2 <x <0.35 is used as a representative value. It is done. The wavelength of light emitted from the light emitting unit 102 is determined by the band gap value of the light emitting layer 126. When the AlGaAs type is used as in the present embodiment, the light emitting layer 126 has an Al composition of about 0.12 to 0.13, and light having a wavelength having a peak near 780 nm can be obtained.

  A specific example of the Al composition and film pressure of each layer of the light emitting element 100 of this embodiment having such a band gap is shown in FIG. In the light emitting element 100 of this embodiment, as an example, Zn is used as a dopant in the case of p-type, and Si is used as a dopant in the case of n-type.

  Further, the light emitting element 100 of the present embodiment includes the light emitting unit 102, the transfer unit 104, and the coupling diode (coupling unit) 106 as described above. Each part will be described in detail.

  The light emitting unit 102 functions as a light emitting thyristor, and is formed on the substrate 120. The anode layer 122, the n-type gate layer 124A, the light emitting layer 126A, the p-type gate layer 128A, the cathode layer 130A, the contact layer 132A, and the cathode electrode 140A. have. The cathode electrodes 140A of the light emitting portions 102 of each bit are connected to each other by a wiring electrode 150A.

  In the light-emitting portion 102 of this embodiment, the light-emitting layer 126 has a double hetero structure, so that confinement of carriers (electrons and holes) is strengthened, and the recombination probability of carriers is increased to increase the light output. Realize.

  The transfer unit 104 functions as a transfer thyristor. The anode layer 122, the n-type gate layer 124A, the light emitting layer 126A, the p-type gate layer 128A, the cathode layer 130B, the contact layer 132B, and the cathode electrode 140B formed on the substrate 120. have. As described above, in the present embodiment, the light emitting unit 102 and the transfer unit 104 share the n-type gate layer 124A, the light emitting layer 126A, and the p-type gate layer 128A.

  In the present embodiment, the cathode electrodes 140B of the transfer units 104 of each bit are alternately connected by the wiring electrode 150B (corresponding to the transfer signal line φ2) or the wiring electrode 150C (corresponding to the transfer signal line φ1). Has been.

  The coupling diode 106 functioning as a coupling unit includes an n-type gate layer 124B, a light emitting layer 126B, a p-type gate layer 128B, a p-type gate electrode 142B, a p-type gate electrode 142C, and an n-type gate formed on the anode layer 122. An electrode 144 is provided. The p-type gate electrodes 142B of the coupling diode 106 of each bit are connected by a wiring electrode 150F (corresponding to the reference potential line Vg). The p-type gate electrode 142A and the p-type gate electrode 142C are connected to the n-type gate electrode 144 of the bit adjacent to one side by the wiring electrode 150D and the wiring electrode 150E.

  An example of a method for forming the light-emitting element 100 of this embodiment will be described.

  First, the anode layer 122, the n-type gate layer 124, the light emitting layer 126, the p-type gate layer 128, the cathode layer 130, and the contact layer 132 are sequentially formed on the substrate 120. In addition, what is necessary is just to apply MOCVD (metal organic chemical vapor deposition) method for the crystal growth of each layer, for example.

  Next, the cathode electrode 140 (140A, 140B) is formed on the contact layer 132. Further, a part of the surface of the p-type gate layer 128 is exposed by etching and removing part of the contact layer 132, the cathode layer 130, and the p-type gate layer 128, and the p-type is formed on the p-type gate layer 128. Gate electrodes 142 (142A, 142B, 142C) are formed.

  Next, a part of the surface of the n-type gate layer 124 is exposed by removing a part of the p-type gate layer 128, the light emitting layer 126, and the n-type gate layer 124, and an n-type gate is formed on the n-type gate layer 124. An electrode 144 is formed. Further, an anode electrode 146 is formed below the substrate 120.

  Thereafter, the entire surface of the substrate 120 on which the cathode electrode 140 (140A, 140B), p-type gate electrode 142 (142A, 142B), and n-type gate electrode 144 are formed is covered with an insulating film 134. Furthermore, an opening is provided in the insulating film 134 on the cathode electrode 140A, the cathode electrode 140B, the p-type gate electrode 142A, the p-type gate electrode 142B, the p-type gate electrode 142C, and the n-type gate electrode 144, and each electrode is connected to the outside. Wiring electrodes 150 (150A, 150B, 150C, 150D, 150E, 150F) are formed to connect to electrode pads (not shown) to which the signal lines are connected. Further, a protective film (not shown) for protecting the surface of the light emitting element 100 is formed thereon.

  In the light emitting element 100 of this embodiment formed as described above, the band gap of the light emitting layer 126 is the smallest, and the coupling diode 106 is formed between the p-type gate layer 128B and the n-type gate layer 124B. Has been.

  By applying a signal (voltage) to the p-type gate electrode 142 and the n-type gate electrode 144 and causing a gate current to flow from the p-type gate electrode 142 and the n-type gate electrode 144 to the cathode electrode 140, the anode electrode 146 and the cathode electrode 140. Conduction between and. Accordingly, carriers (electrons and holes) are recombined in the light emitting layer 126 having a small band gap. As a result, the band gap of the junction region of the coupling diode 106 is reduced, and accordingly, the carrier diffusion potential is also reduced. That is, the diffusion potential is smaller than that of the coupling diode 1106 of the conventional light emitting device 1100 configured between the cathode layer 1130C and the p-type gate layer 1128 shown in FIGS. When the diffusion potential is thus reduced, the threshold voltage at which an effective current flows in the coupling diode 106 is lowered. Therefore, the driving voltage of the light emitting element 100 can be suppressed.

  Further, in the light emitting element 100 of the present embodiment, the light emitting unit 102, the transfer unit 104, and the coupling diode 106 are provided on the anode layer 122 so as to be separated from each other. To suppress.

[Second Embodiment]

  In this embodiment, the case where the light emitting unit 102, the transfer unit 104, and the coupling diode (coupling unit) 106 of the light emitting element 100 are provided in succession will be described. Specifically, in this embodiment, the region (first region) where the light emitting unit 102 is provided on the anode layer 122, the region (second region) where the transfer unit 104 is provided, and the coupling diode 106 are The provided region (third region) is continuous.

  FIG. 10 shows a top view of a schematic configuration of an example of a light emitting element array 50 (chip 62) provided with a plurality of light emitting elements 100 of the present embodiment. FIG. 11 is a cross-sectional view of the light emitting element array 50 shown in FIG.

  In the light emitting element 100 of the present embodiment, the light emitting unit 102 and the transfer unit 104 have substantially the same configuration as that of the first embodiment. On the other hand, the coupling diode 106 has a configuration different from that of the first embodiment. Therefore, the coupling diode 106 of the present embodiment will be described in detail.

  The coupling diode 106 of this embodiment includes an n-type gate layer 124, a light emitting layer 126, a p-type gate layer 128, a p-type gate electrode 142, and an n-type gate electrode 144 formed on the anode layer 122. Yes. In the present embodiment, the light emitting unit 102, the transfer unit 104, and the coupling diode 106 share the n-type gate layer 124, the light emitting layer 126, and the p-type gate layer 128.

  The p-type gate electrodes 142 of the coupling diode 106 of each bit are connected by a wiring electrode 150F (corresponding to the reference potential line Vg). The p-type gate electrode 142 is connected to the n-type gate electrode 144 of the bit adjacent to one side by the wiring electrode 150D and the wiring electrode 150E.

  An example of a method for forming the light-emitting element 100 of this embodiment will be described.

  First, the anode layer 122, the n-type gate layer 124, the light emitting layer 126, the p-type gate layer 128, the cathode layer 130, and the contact layer 132 are sequentially formed on the substrate 120. In addition, what is necessary is just to apply MOCVD (metal organic chemical vapor deposition) method for the crystal growth of each layer, for example.

  Next, the cathode electrode 140 (140A, 140B) is formed on the contact layer 132. Further, a part of the surface of the p-type gate layer 128 is exposed by etching and removing part of the contact layer 132, the cathode layer 130, and the p-type gate layer 128, and the p-type is formed on the p-type gate layer 128. A gate electrode 142 is formed.

  Next, a part of the surface of the n-type gate layer 124 is exposed by removing a part of the p-type gate layer 128, the light emitting layer 126, and the n-type gate layer 124, and an n-type gate is formed on the n-type gate layer 124. An electrode 144 is formed. Further, an anode electrode 146 is formed below the substrate 120.

  Thereafter, the entire surface of the substrate 120 on which the cathode electrode 140, the p-type gate electrode 142, and the n-type gate electrode 144 are formed is covered with an insulating film 134. Furthermore, an opening is formed in the insulating film 134 on the cathode electrode 140A, the cathode electrode 140B, the p-type gate electrode 142, and the n-type gate electrode 144, and electrode pads (not shown) to which the electrodes and external signal lines are connected. Wiring electrode 150 (150A, 150B, 150C, 150D, 150E, 150F) is formed. Further, a protective film (not shown) for protecting the surface of the light emitting element 100 is formed thereon.

  In the light emitting element 100 of this embodiment formed as described above, the light emitting layer 126 has the smallest band gap, and the coupling diode 106 is formed between the p-type gate layer 128 and the n-type gate layer 124. Has been.

  As in the first embodiment, carriers (electrons and holes) are recombined in the light emitting layer 126 having the smallest band gap, so that the band gap in the junction region of the coupling diode 106 is reduced. The carrier diffusion potential is also reduced. As the diffusion potential decreases, the threshold voltage at which an effective current flows through the coupling diode 106 decreases. Therefore, similarly to the first embodiment, the driving voltage of the light emitting element 100 can be suppressed.

  Further, in the light emitting element 100 of the present embodiment, since the light emitting unit 102, the transfer unit 104, and the coupling diode 106 are continuously provided on the anode layer 122, the manufacturing process is facilitated.

  As described above, in the light emitting device 100 of each of the above embodiments, the band gap of the light emitting layer 126 is larger than the band gaps of the anode layer 122, the n-type gate layer 124, the p-type gate layer 128, and the cathode layer 130. It is small and functions as a recombination layer for carrier recombination. The coupling diode 106 is formed between the p-type gate layer 128 and the n-type gate layer 124.

  Therefore, the diffusion potential of the coupling diode 106 is small, and the driving voltage of the light emitting element 100 can be suppressed.

  In addition, since the light emitting thyristor structure of the light emitting unit 102 is a standard double heterostructure, some electrons are injected from the cathode layer 130 in the process of being drawn to the p-type gate electrode 142. Is not structured to trap electrons in the p-type gate layer 128 when it reaches the n-type gate layer 124 and performs a thyristor operation, so that the light-emitting element 100 does not change in the thyristor characteristics. Drive voltage can be reduced.

  As described in each of the above embodiments, the transfer unit 104 and the coupling diode 106 also have the light emitting layer 126 and thus emit light. Compared to the amount of light emitted in 102, the amount is very small. Further, since the surface of the transfer unit 104 and the coupling diode 106 (the surface from which light is emitted) may be covered and the emitted light may be shielded, the influence on the light emitted from the light emitting unit 102 is a problem. It will never be.

  Each of the above embodiments is an example of the present invention, and it is needless to say that it can be changed according to the situation without departing from the gist of the present invention.

  For example, the light emitting layer 126 may be undoped, p-type, or n-type as shown in the above embodiments and examples. Note that holes are less p-type or undoped because they have a lower mobility than electrons and have a small spatial spread (spread in the thickness direction and in-plane direction of the layer) and high luminous efficiency.

  Further, the light emitting element 100 may be a PNPN type or an NPNP type as described above.

  In this embodiment, the light emitting element 100 using an AlGaAs-based material has been described as a specific example. However, the present invention is not limited to this, and the light-emitting element 100 using an InGaAsP-based, AlGaInP-based, InGaN / GaN-based material, or the like. You may apply to.

  In the present embodiment, the case where the light source head 16 of the self-scanning electrophotographic image forming apparatus 10 is applied has been described. However, the present invention is not limited to this, and the light emitting element 100 of the present embodiment is replaced with another light source head. And may be applied to other image forming apparatuses. Further, the light emitting element 100 may be applied to a light source of another device such as a scanner.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Light source head 62 Chip 100 Light emitting element 102 Light emission part (light emission thyristor)
104 Transfer section (transfer thyristor)
106 Coupling diode (coupling part)

Claims (5)

A second conductive type first gate layer formed in a first region on the first conductive type anode layer, a light emitting layer having a smaller band gap than the first gate layer formed on the first gate layer; A first conductivity type second gate layer having a larger band gap than the light emitting layer formed on the light emitting layer, a second conductivity type first cathode layer formed on the second gate layer, the first A light emitting section having a first contact layer of a second conductivity type formed on the cathode layer, and a first cathode electrode formed on the first contact layer;
The first gate layer formed in the second region on the anode layer, the light emitting layer formed on the gate layer, the second gate layer formed on the light emitting layer, and on the second gate layer A second conductivity type second cathode layer formed on the second cathode layer, a second conductivity type second contact layer formed on the second cathode layer, and a second cathode electrode formed on the second contact layer. A transfer unit having
The first gate layer formed in the third region on the anode layer, the first gate electrode of the second conductivity type formed on the first gate layer, and the light emission formed on the first gate layer. A coupling portion having a layer, the second gate layer formed on the light emitting layer, and a second gate electrode of the first conductivity type formed on the second gate layer;
A light emitting device comprising: The first region and the second region are provided continuously, and the first region, the second region, and the third region are provided separately from each other.
The light emitting device according to claim 1. The first region, the second region, and the third region are provided continuously.
The light emitting device according to claim 1.   A plurality of light emitting elements according to any one of claims 1 to 3 are provided as light sources, and a coupling part of the light emitting elements is a transfer part of the light emitting element and a transfer part of the other light emitting element. A light source head that is electrically coupled with the light source. A photoreceptor,
Charging means for charging the surface of the photoreceptor;
An exposure means comprising the light source head according to claim 4 and exposing with light emitted from the light source head to form an electrostatic latent image on the surface of the photoreceptor charged by the charging means,
Developing means for developing the electrostatic latent image formed by the exposure means;
Fixing means for fixing the electrostatic latent image developed by the developing means;
An image forming apparatus.

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