JP2012204678A - Light-emitting thyristor, light source head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting thyristor in which variation in the amount of emitted light due to temperature variation is reduced when compared with a case where the whole gate layer functions as a luminous layer, and to provide a light source head and an image forming apparatus.SOLUTION: In the light-emitting thyristor 100 having an RC structure, a gate layer 108 is laminated between a p-type AlGaAs-based DBR layer 106 functioning as an anode layer, and an n-type AlGaAs-based DBR layer 112 functioning as a cathode layer. The luminous layer is a p-type AlGaAs-based luminous layer 108B having a small band gap, and the remaining gate layer 108 is an n-type AlGaAs-based DBR gate layer 108A having a band gap (average value of band gaps of respective DBR layers) larger than that of the luminous layer 108B.

Description

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

  Patent Document 1 describes a light-emitting thyristor in which a gate layer is formed of layers having different band gaps.

  Patent Document 2 discloses a pnpn light-emitting thyristor having a double hetero structure, wherein the concentration of impurities at least in the anode layer portion near the n-gate layer is lower than the concentration of impurities in the n-gate layer. Is described.

  In Patent Document 3, a first n-type semiconductor layer, a first p-type semiconductor layer, a second n-type semiconductor layer, a third n-type semiconductor layer, a second p-type are formed on an n-type semiconductor substrate. The semiconductor layer, the third p-type semiconductor layer, the fourth p-type semiconductor layer, and the fifth p-type semiconductor layer are sequentially stacked so that light emission inside these stacked semiconductor layers is extracted to the outside. The third n-type semiconductor layer has an energy gap larger than that of the second n-type semiconductor layer, and the third n-type semiconductor layer and the third p-type semiconductor layer have an energy gap. A light-emitting thyristor is described which is larger than the second p-type semiconductor layer, and the second p-type semiconductor layer has an energy gap larger than that of the first p-type semiconductor layer.

JP 08-153890 A Japanese Patent No. 2001-068726 Japanese Patent No. 2005-340471

  An object of the present invention is to provide a light-emitting thyristor, a light source head, and an image forming apparatus in which the variation in the amount of emitted light caused by temperature variation is smaller than when the entire gate layer functions as a light-emitting layer.

  In order to achieve the above object, a light emitting thyristor according to claim 1 includes a substrate, a first semiconductor multilayer reflector of the first conductivity type formed on the substrate, and the first semiconductor multilayer reflector. A gate layer formed by laminating a third semiconductor multilayer reflector and a semiconductor light emitting layer, and a second conductivity type second semiconductor multilayer reflector formed on the gate layer; Prepare.

  The light-emitting thyristor according to claim 2 is the light-emitting thyristor according to claim 1, wherein the average value of the band gap of the third semiconductor multilayer reflector is the average value of the band gap of the first semiconductor multilayer reflector. Smaller than the average value of the band gap of the second semiconductor multilayer mirror.

  The light-emitting thyristor according to claim 3 is the light-emitting thyristor according to claim 1 or 2, wherein the gate layer includes a plurality of third semiconductor multilayer mirrors, and a plurality of the third semiconductor multilayer films. The semiconductor light emitting layer is laminated between the reflecting mirrors.

  The light-emitting thyristor according to claim 4 is the light-emitting thyristor according to any one of claims 1 to 3, wherein the semiconductor light-emitting layer is a non-conductive semiconductor layer.

  A light source head according to a fifth aspect includes a plurality of light emitting thyristors according to any one of the first to fourth aspects as light sources.

  The image forming apparatus according to claim 6, comprising: a photoreceptor; a charging unit that charges the surface of the photoreceptor; and the light source head according to claim 5, and the surface of the photoreceptor charged by the charging unit. An exposure means for exposing with light emitted from the light source head in order to form an electrostatic latent image, a developing means for developing the electrostatic latent image formed by the exposure means, and the developing means developed by the developing means Fixing means for fixing the electrostatic latent image.

  According to the first, fifth, and sixth aspects of the present invention, the light amount fluctuation of the emitted light caused by the temperature fluctuation is reduced as compared with the case where the entire gate layer functions as the light emitting layer.

  According to the second aspect of the present invention, the light emitting thyristor can be appropriately operated as compared with the case where the present configuration is not provided.

  According to the third aspect of the present invention, the amount of emitted light can be increased and the light extraction efficiency can be improved as compared with the case without this configuration.

  According to the fourth aspect of the present invention, both carriers are confined in the semiconductor light emitting layer and recombined with light emission as compared with the case where the semiconductor light emitting layer is of a conductive type.

1 is a schematic configuration diagram showing an outline of an example of an image forming apparatus according to the present embodiment. 1 is a schematic cross-sectional view showing an internal configuration of an example of a printer head according to the present embodiment, and is an enlarged cross-sectional view schematically showing an example of a display medium. It is a perspective view which shows the external appearance of an example of the light emitting thyristor array which concerns on this Embodiment. It is a schematic sectional drawing which shows an example of the light emitting thyristor which concerns on this Embodiment. It is the schematic diagram which showed typically about the main structure of an example of the light emitting thyristor which concerns on this Embodiment. It is explanatory drawing which shows a specific example of Al composition and film thickness of each layer of an example of the light emitting thyristor according to the present embodiment. It is explanatory drawing for demonstrating a specific example of the relationship between the wavelength and intensity | strength of a natural light emission spectrum, a resonator spectrum, and a light emission spectrum in an example of the light emission thyristor which concerns on this Embodiment. It is explanatory drawing which shows a specific example of Al composition of each layer of another layer of the light emitting thyristor which concerns on this Embodiment, and a film thickness. It is the schematic diagram which showed typically about the main structure of the conventional light emitting thyristor. It is explanatory drawing for demonstrating a specific example of the relationship between the wavelength and intensity | strength of a spontaneous emission spectrum, a resonator spectrum, and an emission spectrum in the conventional light emission thyristor.

  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. FIG. 4 is a schematic cross-sectional view showing an example of the light-emitting thyristor of 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 that charges 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 thyristor 100 is controlled by the driving unit to emit a light beam based on the image data.

  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 light emitting unit (light emitting thyristor 100, which will be described later in detail) having a plurality of thyristor structures. As shown in FIG. 2, a mounting board on which a light emitting thyristor array 50 and a circuit (not shown) for supporting the light emitting thyristor array 50 and supplying various signals for controlling the driving of the light emitting thyristor 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 thyristor array 50 facing the photoconductor 12 and is supported by a plate spring 58.

  As shown in FIG. 3, the light-emitting thyristor array 50 includes, for example, a chip 62 configured by arranging a plurality of light-emitting thyristors 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 has been described. However, the present invention is not limited to this, and the chips 62 may be arranged in a two-dimensional manner in a plurality of rows. 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 if the light emitting thyristors 100 are divided into a plurality of chips 62, each of the light emitting thyristors 100 is arranged so that the distance between the two light emitting thyristors 100 adjacent to each other in the axial direction of the photoconductor 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 each light emitting thyristor 100 on the photoconductor 12.

  Next, the light emitting thyristor 100 of the present embodiment will be described.

  A schematic configuration of the light-emitting thyristor 100 according to the present embodiment will be described with reference to FIG. The light-emitting thyristor 100 according to the present embodiment includes a p-type GaAs substrate 104, a p-type AlGaAs anode layer 106 stacked on the p-type GaAs substrate 104, an n-type AlGaAs gate layer 108A, and a p-type AlGaAs. A gate layer 108 composed of a system gate layer 108B, an n-type AlGaAs-based cathode layer 112, and an n-type GaAs-based contact layer 114 are provided.

  The light emitting thyristor 100 includes an anode electrode 102, a gate electrode 116, and a cathode electrode 118. The anode electrode 102 is provided on the back surface (surface on which no resonator is formed) of the p-type GaAs substrate 104. The gate electrode 116 is provided in a region where a partial end region of the p-type AlGaAs-based gate layer 108B is formed in a thinner film than other portions. On the other hand, the cathode electrode 118 is formed on the n-type AlGaAs cathode layer 112 and the n-type GaAs contact layer 114 which are sequentially stacked in a region excluding the region formed in the thin film of the p-type AlGaAs gate layer 108B. Is provided.

  As materials for the anode electrode 102, the gate electrode 116, and the cathode electrode 118, materials suitable for maintaining good ohmic contact with the semiconductor layer or the p-type GaAs substrate 104 that are 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 the light-emitting thyristor 100 according to the present embodiment, the n-type AlGaAs-based cathode layer 112 and the p-type AlGaAs-based anode layer 106 have large band gaps, and a signal (voltage) is applied to the gate electrode 116. By flowing a gate current to the electrode 118, the anode electrode 102 and the cathode electrode 118 are made conductive. As a result, the light emitting layer (a part of the gate layer 108, p in this embodiment, p-type AlGaAs-based cathode layer 112 and p-type AlGaAs-based anode layer 106) has a smaller band gap (resonator). Carriers (electrons and holes) are recombined in the AlGaAs gate layer 108B, which will be described in detail later, and the emitted light is emitted through the uppermost layer (n-type GaAs contact layer 114).

  Next, the main structure of the light emitting thyristor 100 will be described in detail with reference to the drawings. First, the main structure of the conventional light emitting thyristor 1000 will be described for comparison with the light emitting thyristor 100 of the present embodiment. FIG. 9 schematically shows the main structure of a conventional light-emitting thyristor 1000.

  A conventional light-emitting thyristor 1000 includes a p-type GaAs substrate 1104, a p-type AlGaAs DBR (Distributed Bragg Reflector) layer 1106 that functions as an anode layer, an n-type AlGaAs gate layer 1108A, and a p-type AlGaAs gate. A layer 1108B, an n-type AlGaAs DBR layer 1112 functioning as a cathode layer, and an n-type GaAs contact layer 1114 are sequentially stacked. In this way, the anode layer 1106 and the cathode layer 1112 are DBR mirrors, and the n-type AlGaAs-based gate layer 1108A and the p-type AlGaAs-based gate layer 1108B are resonators (cavities), thereby providing an RC (Resonant Cavity) structure. It is said.

  In the conventional light emitting thyristor 1000, the Al composition of the n-type AlGaAs gate layer 1108A and the p-type AlGaAs gate layer 1108B is set to 0.12, so that the n-type AlGaAs gate layer 1108A and the p-type AlGaAs gate layer 1108B are 0.12. Light having a peak wavelength of 780 nm is generated in the gate layer 1108B. In the RC structure, the thickness of one layer of the DBR mirror is 780 / (4n) nm, and the length of the resonator is an integral multiple of 780 / (2n) nm, so that light having a peak wavelength of 780 nm is obtained. Is emitted. Here, n is a refractive index with respect to light of 780 nm of AlGaAs constituting a DBR mirror or a resonator.

  In general, in a light emitting thyristor having an RC structure, a product of a spontaneous emission spectrum in a gate layer and a resonator spectrum formed by the RC structure becomes an emission spectrum emitted to the outside. A specific example of the relationship between the spontaneous emission spectrum, the resonator spectrum, and the wavelength and intensity of the emission spectrum in the conventional light emitting thyristor 1000 is shown in FIG.

  In the spontaneous emission spectrum, the peak wavelength is shifted due to temperature fluctuation. Specifically, when the temperature rises, the peak wavelength shifts to the long wavelength side (right side in FIG. 10).

  In general, in a light-emitting thyristor, it is desirable that the gate layer be thick from the viewpoint of withstand voltage in order to perform a stable thyristor operation as a thyristor element. On the other hand, when the gate layer constituting the cavity is thick, the mode interval of the resonator spectrum is shortened and the intensity changes sharply with respect to the wavelength. Therefore, when the spontaneous emission spectrum shifts due to temperature fluctuation, the emission spectrum changes greatly. .

  In the conventional light-emitting thyristor 1000, the n-type AlGaAs-based gate layer 1108A and the p-type AlGaAs-based gate layer 1108B constitute a cavity, so that the film thickness is large. As shown in FIG. As described above, when the spontaneous emission spectrum shifts due to temperature fluctuation, the emission spectrum varies greatly. That is, there arises a problem that the amount of light emitted from the light-emitting thyristor 1000 varies greatly due to temperature variation.

  Next, the main structure of the light-emitting thyristor 100 of this embodiment will be described. FIG. 5 schematically shows the main structure of the light-emitting thyristor 100 of the present embodiment.

  The light-emitting thyristor 100 according to the present embodiment includes a p-type GaAs substrate 104, a p-type AlGaAs DBR (Distributed Bragg Reflector) layer 106 that functions as an anode layer, and an n-type AlGaAs-based gate layer that functions as a DBR layer. A gate layer 108 comprising a DBR gate layer 108A and a p-type AlGaAs light-emitting layer 108B that functions as a light-emitting layer, an n-type AlGaAs DBR layer 112 functioning as a cathode layer, and an n-type GaAs-based material The contact layer 114 is laminated. In this way, the p-type AlGaAs anode layer 106 and the n-type AlGaAs cathode layer 112 are DBR mirrors, and the light-emitting layer that becomes the cavity is the p-type AlGaAs light-emitting layer 108B that is part of the gate layer 108, and the remaining The gate layer 108 is a DBR layer (n-type AlGaAs-based DBR gate layer 108A), and the reflectivity of the n-type AlGaAs-based DBR layer 112 is slightly lower than that of the p-type AlGaAs-based DBR layer 106. An RC (Resonant Cavity) structure that emits light from the AlGaAs-based DBR layer 112 side is employed.

  FIG. 6 shows a specific example of the Al composition and film thickness of each layer of the light emitting thyristor 100. In FIG. 6, a part of the film thickness is shown as an optical film thickness based on the peak wavelength λ. This is because the peak wavelength in the semiconductor layer is assumed when the peak wavelength of the emitted light emitted from the light emitting thyristor 100 to the outside is λ0, and the refractive index of the semiconductor layer of the difference propagating outside in the semiconductor layer having the wavelength λ0 is n. The wavelength λ is λ = λ0 / n. In general, the DBR layer formed of a plurality of layers having different Al compositions and the resonator length formed of the gate layer are designed based on the wavelength in the semiconductor layer. It is.

  In the light emitting thyristor 100 of the present 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.

  A p-type AlGaAs DBR layer 106 that functions as an anode layer is stacked on a p-type GaAs substrate 104 via a p-type GaAs buffer layer. Although not shown in FIGS. 4 and 5, in the light-emitting thyristor 100 of the present embodiment, as shown in FIG. 6, the crystallinity between the p-type GaAs substrate 104 and the anode layer 106 is improved. Is provided with a p-type GaAs buffer layer.

  The p-type AlGaAs DBR layer 106 is formed by laminating an AlGaAs layer having a thickness of λ / 4 nm with an Al composition of 0.16 and an AlGaAs layer having a thickness of λ / 4 nm with an Al composition of 0.86. Ten pairs are repeatedly stacked. Therefore, the entire thickness of the p-type AlGaAs DBR layer 106 is 5λ nm, and the average composition of Al is 0.51.

  The n-type AlGaAs-based DBR gate layer 108A is formed by laminating an AlGaAs layer having an Al composition of 0.12 having a thickness of λ / 4 nm and an AlGaAs layer having an Al composition of 0.24 having a thickness of λ / 4 nm. Two pairs are repeatedly laminated. Therefore, the entire thickness of the n-type AlGaAs DBR gate layer 108A is λ nm, and the average composition of Al is 0.18. In the present embodiment, light is emitted also in an AlGaAs layer having an Al composition of 0.12, which is included in the n-type AlGaAs DBR gate layer 108A.

  The p-type AlGaAs light emitting layer 108B is an AlGaAs layer having a thickness of 2λ nm and an Al composition of 0.12.

  Specifically, the cathode layer (DBR layer) 112 includes an AlGaAs-based cathode layer having a thickness of λ / 4 nm and an AlGaAs-based cathode layer having a thickness of 0.86, and an AlGaAs-based layer having a thickness of 30 nm and an Al composition of 0.16. The n-type AlGaAs DBR layer 112 is laminated between the cathode layer and the cathode layer. The n-type AlGaAs-based DBR layer 112 is formed by laminating an AlGaAs layer having a thickness of λ / 4 nm with an Al composition of 0.16 and an AlGaAs layer having a thickness of λ / 4 nm with an Al composition of 0.86. Pairs are repeatedly stacked in four layers. Therefore, the thickness of the n-type AlGaAs DBR layer 112 is 2λ nm, and the average composition of Al is 0.51.

  The n-type GaAs-based contact layer 114 has a thickness of 25 nm.

  In addition, the Al composition and the film thickness of each of these layers are specific examples, and are not limited to these as long as they are within the following ranges.

  For example, the thickness of the p-type AlGaAs light emitting layer 108B is an integral multiple of λ / 2. In addition, the thickness of the entire gate layer may be such that no current flows even if there is a potential difference (for example, 3 to 5 V) between the gate electrode 116 and the anode electrode 102. Note that the p-type AlGaAs light-emitting layer 108B needs to be partially exposed in the light-emitting thyristor 100 of the present embodiment as shown in FIG. Therefore, it is preferably about 0.1 μm or more.

  In addition, for example, the Al composition of each layer can be operated as a thyristor by using a p-type AlGaAs light emitting layer 108B <n-type AlGaAs DBR gate layer 108A (average value) <cathode layer (n-type AlGaAs DBR). Layer 112) and anode layer (p-type AlGaAs DBR layer 106) (average value) are within an appropriate range.

  For crystal growth of each layer of the light-emitting thyristor 100, for example, a MOCVD (Metal Organic Chemical Vapor Deposition) method is applied.

  As described above, in the light-emitting thyristor 100 having the RC structure according to the present embodiment, between the p-type AlGaAs DBR layer 106 functioning as an anode layer and the n-type AlGaAs DBR layer 112 functioning as a cathode layer. Of the stacked gate layers 108 is a p-type AlGaAs-based light-emitting layer 108B having a small band gap, while the remaining gate layer 108 is more band-gap than the light-emitting layer 108B (average of band gaps of DBR layers). The n-type AlGaAs DBR gate layer 108A having a large value.

  Since the p-type AlGaAs light emitting layer 108B, which is a part of the gate layer 108, is used as the light emitting layer, the entire gate layer 108 (in the case of the conventional light emitting thyristor 1000 shown in FIG. And the p-type AlGaAs-based gate layer 1110) function as a light emitting layer, the cavity layer becomes thinner and the cavity length becomes shorter. On the other hand, since the entire thickness of the gate layer 108 is maintained, the breakdown voltage is maintained.

  FIG. 7 shows a specific example of the relationship between the spontaneous emission spectrum, the resonator spectrum, and the wavelength and intensity of the emission spectrum in the light emitting thyristor 100 of the present embodiment. Since the cavity layer is thinned, as shown in FIG. 7, the spectrum width of the resonator spectrum is expanded and the mode interval is also increased.

  Therefore, as described above, even when the peak position of the spontaneous emission spectrum is shifted due to temperature fluctuations, fluctuations in the emission spectrum are suppressed, thereby suppressing fluctuations in the amount of emitted light with respect to temperature fluctuations.

  In addition, since the spectrum width of the resonator spectrum is expanded and the efficiency of spontaneous light emission is increased, the amount of emitted light is increased. Furthermore, even if the film thickness of the entire light emitting thyristor 100 element remains constant, the reflectance of the DBR layer provided below the light emitting layer is increased, so that the amount of emitted light is increased, and thus the light extraction efficiency is improved.

  Further, in the light emitting thyristor 100 of the present embodiment, the average composition of Al in the n-type AlGaAs DBR gate layer 108A is set to the outside of the gate layer 108 (p-type AlGaAs DBR layer 106: anode layer, n-type AlGaAs system). Therefore, the light emitting thyristor is appropriately operated. Note that when the average composition of Al in the BR gate layer 108A is the same as or larger than that outside the gate layer 108, the light emitting thyristor does not operate properly.

  Note that the light-emitting thyristor 100 is not limited to the above structure and composition, and the gate layer 108 only needs to be composed of the DBR gate layer 108A and the light-emitting layer 108B. For example, the stacking order of the DBR gate layer 108A and the light emitting layer 108B may be reversed. Note that electrons are more likely to move regardless of the band gap than holes, and thus the light-emitting thyristor 100 of this embodiment is preferably stacked in this order.

  Further, in this embodiment mode, the gate layer 108 includes the DBR gate layer 108A and the light emitting layer 108B, one layer each, but may include a plurality of layers. For example, DBR gate layers may be provided above and below the light emitting layer. A specific example of the Al composition and film thickness of each layer of such a light emitting thyristor is shown in FIG. In the light-emitting thyristor having the structure shown in FIG. 8, the gate layer is formed in order from the substrate side, an n-type AlGaAs-based DBR gate layer, a non-doped AlGaAs-based light-emitting layer having an Al composition of 0.12, and a p-type AlGaAs-based layer. A DBR gate layer is stacked. In this case, the proper range of the Al composition of the p-type AlGaAs DBR gate layer is preferably 0.3 or less from the viewpoint of gate contact formation. With such a configuration, it is possible to suppress the light amount fluctuation of the emitted light caused by the temperature fluctuation, and to increase the emitted light amount, thereby improving the light extraction efficiency. The light emitting layer may be either p-type or n-type. However, as shown in FIG. 8, by forming a non-doped semiconductor layer, both minority carriers (electron / positive) are formed in the light emitting layer. Hole) is confined and light emission is recombined, so that the light emission efficiency is increased, which is preferable.

  In the present embodiment, as a specific example, the light-emitting thyristor 100 having the p-type first conductivity type and the n-type second conductivity type on the p-type GaAs substrate 70 has been described. The light-emitting thyristor of the NPNP structure may be an n-type first conductivity type and a p-type second conductivity type.

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

  Further, in the present embodiment, the case where it is applied to the light source head 16 of the self-scanning electrophotographic image forming apparatus 10 has been described. And may be applied to other image forming apparatuses. Further, the light emitting thyristor 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 100 Light emission thyristor 102 Anode electrode 104 p-type GaAs substrate 106 p-type AlGaAs type DBR layer (anode layer)
108 Gate layer 108A n-type AlGaAs DBR gate layer 108B p-type AlGaAs light-emitting layer 112 n-type AlGaAs DBR layer (cathode layer)
114 n-type GaAs contact layer 116 gate electrode 118 cathode electrode

Claims (6)

A substrate,
A first conductivity type first semiconductor multilayer film reflecting mirror formed on the substrate;
A gate layer formed on the first semiconductor multilayer mirror and formed by laminating a third semiconductor multilayer reflector and a semiconductor light emitting layer;
A second conductivity type second semiconductor multilayer mirror formed on the gate layer;
Light-emitting thyristor with   The average value of the band gap of the third semiconductor multilayer film reflecting mirror is smaller than the average value of the band gap of the first semiconductor multilayer film reflecting mirror and the average value of the band gap of the second semiconductor multilayer film reflecting mirror. The light-emitting thyristor according to claim 1, which is also small.   The said gate layer is provided with the said some 3rd semiconductor multilayer film reflective mirror, The said semiconductor light emitting layer is laminated | stacked between each of the said some 3rd semiconductor multilayer film reflective mirror, The Claim 1 or Claim 2. The light-emitting thyristor according to 2.   The light emitting thyristor according to claim 1, wherein the semiconductor light emitting layer is a non-conductive semiconductor layer.   5. A light source head comprising a plurality of light emitting thyristors according to claim 1 as a light source. A photoreceptor,
Charging means for charging the surface of the photoreceptor;
An exposure means comprising the light source head according to claim 5 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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