JP3093439B2 - Semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used as a light source for an electrophotographic image forming apparatus or an optical printer, and more particularly to a light emitting diode array in which light emitting dots are arranged in a straight line. The present invention relates to a semiconductor light emitting device that performs optical writing on a photosensitive member or the like by using a light source.

[0002]

2. Description of the Related Art In recent years, research on a light emitting diode array for use as a light source of an electrophotographic image forming apparatus or an optical printer has been advanced. This light-emitting diode array is composed of a self-luminous array element, emits light from the light-emitting diode array in response to an image signal, forms an electrostatic latent image on the surface of the photoreceptor with the same-size imaging element, and uses the electrophotographic method. Printing and printing are performed through development, transfer, and fixing steps. As shown in FIG. 9, a light emitting unit substrate constituting an optical printer head using this conventional light emitting diode array has wiring members 103, 104, 105 formed of a ceramic substrate or the like on a substrate 102 also serving as a heat sink. Are attached to the wiring members 103, 104, and 105, and cables 106 and 107 for connection to image signals and a power supply are connected to the wiring members 103, 104, and 105, respectively. Also, 108-1 to 108-n (n is a positive integer) in the figure are light-emitting diode array chips in which light-emitting diodes are arranged in a line, and 109-1 to 109-n and 110-1 to 110-n
Is a driver circuit for driving the light-emitting diode array chips 108-1 to 108-n, that is, a light-emitting diode drive integrated circuit having a built-in serial-parallel conversion circuit for image signals input from the cables 106 and 107 and the like.

In the light emitting unit substrate 101 having such a configuration, the image signals are sequentially transmitted from the cables 106 and 107 for one line to the light emitting diode drive integrated circuits 109-1 to 109-n and 110-1 to 110.
-n, shift one row of data, output it in parallel to the light emitting diode drive terminal, and then each light emitting diode is turned on and off according to it, and one row of image forming bright spots is generated . As for the relationship between the light emitting portion of the light emitting diode and the image forming point of the photosensitive drum surface, as shown in FIG. 10, the light emitting diode 201-mp on each light emitting diode array chip 201-m constituting the light emitting diode array is: The photosensitive drum 203 is provided by an equal-magnification imaging system 202 such as a selfoc lens array or an RMLA (roof mirror lens array).
Imaged on top. An optical printer head using such a light emitting diode array has no moving parts and has few components, and thus can be downsized. In addition, the self-emission type has a high extinction ratio, provides good contrast, and can be made longer by connecting the chip. There are advantages.

A light emitting diode array used in such an optical print head is, for example, a surface emitting type light emitting diode array in which a large number of light emitting portions such as squares are arranged in a predetermined direction in a plane parallel to a substrate surface, or a substrate surface. Edge-emitting light-emitting diodes that can provide a large number of light outputs arranged in a predetermined direction from an end surface perpendicular to the end surface. First, as a basic structure of a surface-emitting light emitting diode array, for example, a structure shown in FIG. 11 is reported (Preliminary Proceedings of the Dentsu Society of Japan, 1980, pp. 1-211).
In order to make the intensity of the light output obtained from the light emitting unit 120 uniform within the light emitting surface, electrodes 12 are provided at both ends or around the light emitting unit 120.
1 is formed. However, in this structure, the light emitting portion 120 from which light output is taken out and the electrode 121 are on the same plane, so the width required per unit element is the width of the light emitting portion 120, the width of the element isolation region, and the width of the electrode 121. It is the sum in the necessary range. In the case of a surface-emitting light emitting diode,
Normally, the width of the light emitting section 120 is required to be about 40 μm, and the width of the element isolation region is required to be about 20 μm. Therefore, the minimum width required per unit element is required to be 60 μm. When considered, it is no longer 800 dpi (21.1
It is extremely difficult to form a high-density light-emitting portion in a light-emitting diode array chip having a pitch of 5 μm pitch or more because the width of an element isolation region becomes small. This is one of the reasons why 400 dpi (63.5 μm pitch) is currently the mainstream.

Next, as an edge emitting type light emitting diode array, for example, there is one as shown in FIG. 12 (Japanese Patent Laid-Open No. 60-32373). In this example, a plurality of light emitting diodes are arranged in a laminated structure on a substrate. These light emitting portions 122 are electrically connected between adjacent edge emitting light emitting diodes by separating grooves 123 formed in a direction parallel to the end surface in a plane parallel to the substrate surface. And spatially separated. In such an edge-emitting light-emitting diode array, the light-emitting section 122 from which light output is taken out and the electrodes 124, 1
25 are not present on the same plane, and the width required per unit element is the sum of only the width of the light emitting portion 122 and the width of the element isolation groove region. Since the formation of the light emitting portion 122 having a high density is determined in principle by the minimum width of the element isolation region, it is possible to sufficiently realize the element by using the current technology. Therefore, it can be said that an edge emitting light emitting diode array is more suitable as a light emitting diode array used as a light source for a high density optical printer than a surface emitting light emitting diode array. In addition, the variation in the light output of each light emitting diode in the light emitting diode array chip for both the edge emitting type and the surface emitting type has been improved by the recent progress of the crystal growth technology of the compound semiconductor (the layer having the crystal growth structure in the substrate plane). Good uniformity of thickness and uniformity of electrical and optical characteristics of the film), and it is possible to keep the variation of the light output of each light emitting diode in the light emitting diode array within the chip within ± 5%. It became.

[0006]

However, in the above-described conventional semiconductor light emitting device using the light emitting diode array, an electrode for extracting the electrical or optical characteristics of the compound semiconductor crystal growth layer constituting the light emitting diode array. As shown in FIG. 10, when the same-magnification imaging element having a focal length condition and the like and the light-emitting diode array chip row are combined due to variations in the mounting means including the forming means and the heat radiating means of the element, and the arrangement accuracy, etc. Because of the relationship between the light emitting diode light emitting portion and the image forming point on the drum surface, the light output intensity formed on the photosensitive drum 203 has non-uniformity (the value is up to ± 50%). However, when used as an optical printer light source, there is a problem that a large difference occurs in the size of a printing dot and printing density. In particular, in a conventional light printer light source using an edge-emitting light emitting diode array, it is necessary to manufacture a light emitting diode array head by arranging a large number of light emitting diode array chips as shown in FIG. For this reason, depending on the connection technology of the light emitting diode array chips, even if the light output of each light emitting diode in the light emitting diode array chip can be made uniform, the light output from the light emitting diode array head (focal length condition, etc. (Light output after passing through the same magnification imaging element), the light output lacks uniformity, or the light-emitting diode dot missing occurs at the imaging point on the drum surface. .

That is, when the connection accuracy of the light emitting diode array chips cannot be obtained, as shown in FIG. 10, the relationship between the light emitting diode light emitting portion and the image forming point on the drum surface is determined by each light emitting diode constituting the light emitting diode array. The image formed on the photosensitive drum 203 is defined by the positional relationship between the light-emitting diode 201-mp on the array chip 201-m and the same-magnification imaging system 202 such as a selfoc lens array or RMLA (roof mirror lens array). Therefore, a false dot missing occurs at a joint in the column direction of the light emitting diode array chip due to a chip arrangement error with respect to the X axis (main scanning direction), and the Y axis (light emitting direction).
In contrast, the non-uniformity of the light output after passing through the lens array occurs due to the focal depth shift with respect to the unit magnification imaging system 202 (lens array), and the optical axis shift with respect to the lens array with respect to the Z axis (sub-scanning direction). This causes non-uniformity of light output after passing through the lens array. Therefore, even if the light output of the edge emitting type light emitting diode array chip itself is uniform, the light output may become non-uniform depending on the accuracy of the connecting technique of the light emitting diode array chips at the time of manufacturing the light emitting diode array head. Often, large differences occur in the size of print dots and print density.

As a rudimentary means for solving the above problem, as shown in FIG. 8, a light emitting diode at an end in a light emitting diode array chip and a light emitting diode at an end in a light emitting diode array chip adjacent to the light emitting diode chip are arranged. Dot pitch: a (for example, 800 dpi: 21.1)
The light emitting diode array head may be manufactured by precisely arranging the light emitting diode array heads so as to have a pitch of 5 μm by an array chip connecting technique. However, it is not so easy in practice. In other words, the state-of-the-art light emitting element mounting position accuracy at the state of the art, and the accuracy of the light emitting part between adjacent chips is ± 7.5 μm (in the case of all surface emitting light emitting diode array heads)
Although the X-axis (main scanning direction) and the linearity of the entire light emitting diode array chip are ± 10 μm (Y-axis: sub-scanning direction), the technology is completed in the same manner as the Z-axis (light emission direction). Does not exist. Therefore, it is actually difficult to accurately arrange them depending on the connection technique of the array chips. Here, since the light emitting portions between adjacent chips are actually overlapped with each other, there is no negative accuracy. Therefore, the light emitting portion accuracy between adjacent chips is 15 μm (X
Axis), the linearity of one of the light-emitting diode array chip rows is 20 μm (Y-axis), and they are arranged with no problem in the Z-axis direction. Therefore, even if a light emitting diode array head can be manufactured by arranging the light emitting diodes with high precision by the connection technique of the array chips, dots of the light emitting diode may be simulated at the image forming point on the drum surface (X axis). A large difference in the size of the printing dots and the printing density occurs (Y axis), and the printing quality is reduced. This is a major obstacle to realizing high-density optical printer heads, and as long as the configuration of the printer head consists essentially of a light-emitting diode array, a driving integrated circuit, and a lens array, the current mounting technology It is not possible to respond at the level.

In view of the above, the present invention allows a light-emitting diode array head to be basically constructed without using a lens array when used in an optical printer light source or the like, and does not impose a burden on array chip connection technology. It is an object of the present invention to provide a semiconductor light emitting device provided with a light emitting diode array chip which can be manufactured and can make light output on a photosensitive drum surface uniform.

[0010]

To achieve the above object, the present invention provides at least a light emitting layer of a light emitting diode,
The light-emitting layer has a laminated structure including electrodes for emitting light, and an edge-emitting light-emitting diode in which light output is obtained from the laminated end face is electrically and spatially separated by a plurality of first separation grooves provided at equal intervals. In a semiconductor light emitting device composed of a light emitting diode array formed separately, the light emitting diodes at both ends on a light emitting diode array chip are cut at an angle of 16 ° or less according to Snell's law. , And has a shape different from other light emitting diodes.

[0011]

In the semiconductor light emitting device of the present invention, an edge emitting light emitting diode array having light directivity is used as a light source, and the shape of the light emitting diodes at both ends on the light emitting diode array chip is different from other light emitting diodes. By making such a light emitting diode array chip shape,
The dot omission of the light emitting diode at the drum surface imaging point can be prevented, and the printing quality can be improved. In addition, when the array chips are connected and mounted, the accuracy of the light emitting portion between adjacent chips (X
Since a large mounting margin with respect to (axis) can be taken, the yield at the time of manufacturing the light emitting diode array head can be improved. Further, as for the edge emitting light emitting diode having light directivity, a so-called double hetero junction structure comprising an active layer and a cladding layer which is a light confinement layer is used for the element structure, and the thickness d of the active layer is 0.01 μm <d. <0.
The energy gap difference ΔE between the active layer and the cladding layer is set to 0.1 eV <ΔE <0.3 eV,
This can be realized by symmetrically arranging the active layers. On the other hand, the shape of the light-emitting diodes at both ends on the light-emitting diode array chip is smaller than the critical angle according to Snell's law in consideration of the refractive index n inherent in the material of the active layer of the light-emitting diode in the outward direction (longitudinal direction) of the chip. This can be realized by forming a light emitting end surface having a surface inclined to each other.

As described above, in the semiconductor light emitting device of the present invention, the means for preventing the false omission of the light emitting diode at the image forming point on the drum surface is provided by a method which does not depend on the technology for connecting and mounting the light emitting diode array chips. Can be achieved. As a result, a uniform high-quality image with no missing dots can be realized. Further, since the light-emitting diode array head can be achieved without using a lens array, simplification in manufacturing the array head can be achieved, and the yield is improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a view showing one embodiment of the present invention, and is a plan view of a light-emitting diode array chip constituting a semiconductor light-emitting device. FIG. 2 is a cross-sectional view of a laminated structure of the light-emitting diode array chip shown in FIG. FIG. 3 is a perspective view of a light emitting diode array portion of the light emitting diode array chip shown in FIG. In the light emitting diode array chip shown in FIG. 1, an edge emitting light emitting diode array 2 (2-1 to 2-256)
Is equivalent to a dot density of 600 dpi, and 256 elements are formed on the n-type GaAs substrate 1. As shown in FIG. 2, the stacked structure of this light emitting diode array 2
N-type GaAs buffer layer 2 prepared by VPE method
1. Energy gap: 1.92 eV n-type Al _0.4 Ga
_{A 0.6} As cladding layer 22, an Al _0.2 Ga _0.8 As active layer 23 having an energy gap of 1.67 eV as a light emitting layer, a p-type Al _0.4 Ga _0.6 As cladding layer 24 having an energy gap of 1.92 eV, a p-type GaAs cap layer 25, and It is formed of a stacked structure composed of a plurality of layers of a p + -type GaAs contact layer 26 doped with zinc at a high concentration. Al
The thickness d of the _0.2 Ga _0.8 As active layer 23 is 0.05 μm.
Further, the energy gap difference between the active layer and the cladding layer: Δ
E is 0.25 eV. In addition, since the present laminated structure includes a so-called double heterostructure, the angle θ of the luminous flux at the depression angle and the angle of elevation at the far-field image of the light output are equal.

The first separation groove 11 (see FIG. 3) reaching the substrate 1 perpendicularly to the array direction from the surface of the laminated structure, that is, from the upper surface of the contact layer 26 to the surface of the substrate 1, uses a chlorine-based gas. The light-emitting diodes (2-1 to 2-256) in the light-emitting diode array 2 are electrically separated by the first separation groove 11 by a dry etching method. The light emitting end face 2a of each light emitting diode (2-1 to 2-256) is arranged at a position perpendicular to the substrate surface and parallel to the array direction and close to the side 1a of the substrate 1. Thus, the light emitting diode array 2 is formed, and at the same time, the light emitting diodes (2-1, 2-256) at both ends on the light emitting diode array chip different from the other light emitting diodes according to the present invention are formed.

As shown in FIG. 2, on the contact layer 26 of each light emitting diode (2-1 to 2-256) of the light emitting diode array 2,
As shown in FIG. 3, a p-type electrode 27 made of Au—Zn / Au is formed, and Au—G
An n-type electrode 28 made of e / Ni / Au is formed.
As shown in FIG. 1 and FIG. 3, the p-type electrode 27 is a bonding wire for wiring arranged on the side opposite to the light emitting end face 2a of the end face light emitting diode array 2 and behind the end face light emitting diode array 2. It is electrically connected to the pads 3 (3-1 to 3-256). This bonding pad 3 (3-1 to 3-25
6) and the wiring are formed on the GaAs substrate 1 via an insulating film 31 such as SiO ₂ deposited by PE-CVD or the like, thereby protecting the element from damage due to bonding and preventing deterioration in luminous efficiency. I'm preventing. The wiring bonding pads 3 (3-1 to 3-256) are arranged in four stages in the light emitting direction, so that high-density mounting is possible. The light emitting diode array chip is connected from the wiring bonding pad 3 to a driver circuit chip (not shown) by wire bonding. In FIG. 3, the insulating film 31 of each light emitting diode (2-1 to 2-256) is separated and shown in the figure for easy reference of the laminated structure including a plurality of layers of the light emitting diode. is there. The near-field image (N.F.
P) is shown in FIG. 35μ near-field image of each light emitting diode
It can be seen that the light directivity is about mx 6 µm.

The shape of the light emitting diodes at both ends on the light emitting diode array chip is smaller than the critical angle in accordance with Snell's law in consideration of the refractive index n inherent in the material of the active layer of the light emitting diode. Are cut and formed. Hereinafter, the shapes of the light emitting diodes at both ends will be described with reference to the drawings of the embodiments. That is,
FIG. 5 (for the sake of convenience, explanation will be made with 2-256 light emitting diodes, but the opposite side 2-1 is only symmetrical with 2-256 as shown in FIG. 1, and the same applies to the application of the present invention. As shown in (a), the normal line on the boundary between the active layer having the refractive index n ₁ and the medium (for example, air) having the refractive index n ₂ , the transmitted light of the light emitted from the inside of the light emitting diode, and the emission from the end face of the light emitting diode. angle between Shako, i.e., between the transmission angle [psi ₁ and outgoing light [psi _2, the following relationship holds according to Snell's law. _{n 1 sinψ 1 = n 2 sinψ} 2 ··· (1) The critical angle theta _c the total reflection occurs is given by the following equation. θ _c = sin ~ ¹ (n ₂ / n ₁ ) (2)

Since the refractive index n ₁ of the Al _0.2 Ga _0.8 As active layer 23 is 3.54 and the refractive index n ₂ of the medium (air) is 1, the critical angle θ _{c is} 16.4 °. Accordingly, the cut angle of the light emitting facet has to be smaller than the critical angle theta _c. Table 1 according to the present invention [psi ₁ and shows the [psi ₂ relationship.

[Table 1]

[0018] Therefore, when [psi ₁ to 16 ° becomes the light emitting intensity profile as shown in FIG. 6 for the light is emitted in an angle of 77.4 ° to the normal to on the boundary surface. Incidentally, the spread width of the light beam at a position 3 mm away from the light emitting end face is about 80 μm, which is a device that can be sufficiently used without a lens. Therefore, the object of the present invention is achieved by the synergistic action of the light emission intensity profile with the light emitting diode at each end of the adjacent light emitting diode array chip. The driving of the element according to the present invention is basically based on 3-bit lighting.
It goes without saying that bit lighting is also possible. Therefore, when each light emitting diode (2-1 to 2-256) in the light emitting diode array is electrically separated by dry etching using a chlorine-based gas, the shape of the light emitting diodes at both ends on the light emitting diode array chip is changed. 16 ° according to the invention
What is necessary is just to use the dry etching mask designed so that it can cut below.

Now, as described above, each light emitting diode array is formed by the dry etching method using a chlorine-based gas. At this time, the shape of the light emitting diode at both ends on the above-mentioned light emitting diode array chip is different from the other light emitting diodes in the light emitting end face, and at the same time, the width and the element length of the light emitting diode are smaller than the other light emitting diodes. By adjusting, rather than making the area of the current injection area smaller than that of the other light emitting diodes, and keeping the injection current for all the light emitting diodes on the array chip constant, the light emitting diode injection at both ends on the light emitting diode array chip The light emitting diode is formed so as to obtain a higher light output than other light emitting diodes by increasing the current density.

Next, as another embodiment of the semiconductor light emitting device according to the present invention, the shapes of the light emitting diodes at both ends on the light emitting diode array chip will be described with reference to FIG. It is also applicable to 2-1). Embodiment 2 In this embodiment, in the light emitting diode array chip shown in FIG. 1, the shape of the light emitting diodes at both ends on the light emitting diode array chip different from other light emitting diodes according to the present invention is shown in FIG. As described above, the light emitting diode is formed into a concave shape so that the light emitting end face becomes substantially straight at an angle smaller than the critical angle according to Snell's law in consideration of the refractive index n inherent to the material of the active layer of the light emitting diode. .

Embodiment 3 In this embodiment, in the light emitting diode array chip shown in FIG. 1, the shape of the light emitting diodes at both ends on the light emitting diode array chip different from other light emitting diodes according to the present invention is shown in FIG. ), The light emitting diode is formed by being cut into a convex shape so that the light emitting end face becomes substantially straight at an angle smaller than the critical angle according to Snell's law in consideration of the refractive index n inherent to the material of the active layer of the light emitting diode. ing.

Embodiment 4 In this embodiment, in the light emitting diode array chip shown in FIG. 1, the shape of the light emitting diodes at both ends on the light emitting diode array chip different from the other light emitting diodes according to the present invention is shown in FIG. ), The light emitting end face is cut and formed in a trapezoidal shape at an angle smaller than a critical angle according to Snell's law in consideration of the refractive index n inherent to the material of the active layer of the light emitting diode.

Embodiment 5 In this embodiment, in the light emitting diode array chip shown in FIG. 1, the shape of the light emitting diodes at both ends on the light emitting diode array chip different from the other light emitting diodes according to the present invention is shown in FIG. ), The light emitting end face is cut into a concave shape so as to be substantially straight at an angle smaller than the critical angle according to Snell's law in consideration of the refractive index n inherent in the material of the active layer of the light emitting diode, and has a trapezoidal shape. Is formed.

Embodiment 6 In this embodiment, in the light emitting diode array chip shown in FIG. 1, the shape of the light emitting diodes at both ends on the light emitting diode array chip different from the other light emitting diodes according to the present invention is shown in FIG. ), The light emitting end face is cut into a convex shape so that the light emitting end face becomes substantially straight at an angle smaller than the critical angle according to Snell's law in consideration of the refractive index n inherent to the material of the active layer of the light emitting diode. It is formed in a shape.

The edge emitting light emitting diode array 2 configured as described above has an MO having excellent uniformity of film characteristics.
Since the light emitting diode array is manufactured by the VPE method, the variation of the light output is within ± within the same light emitting diode array chip.
It is less than 5%. In the edge emitting light emitting diode array 2 on the light emitting diode array chip which is the light emitting portion of the semiconductor light emitting device according to the present invention, the n type is p
The type and the p-type may be configured as the n-type. Further, a light-emitting end face of the edge-emitting light-emitting diode array 2 on the light-emitting diode array chip and a first separation groove for separating each light-emitting diode of the edge-emitting light-emitting diode array 2 from each other.
Although 11 is formed perpendicular to the surface of the substrate 1, it is not necessarily required to be perpendicular, and may be any surface that is substantially perpendicular or not parallel to the active layer 23. Also, the first separation groove 11,
Although the groove is formed so as to reach the substrate 1 from the surface of the laminated structure, the bottom of the groove is not necessarily formed on the substrate 1 because the active layers 23 of the adjacent edge emitting light emitting diodes only have to be electrically separated. It does not need to reach, and it will function sufficiently if it reaches the cladding layer 22 through the active layer 23.

[0026]

As described above, the present invention is shown in FIG. 6 by forming the light emitting diodes at both ends of an edge emitting type light emitting diode array chip constituting a semiconductor light emitting device in accordance with Snell's law. Because such a light emitting diode light emission intensity profile can be realized,
When manufacturing a light-emitting diode array head, it is possible to prevent false dot omission at a connection portion in the column direction of the light-emitting diode array chip due to an alignment error with respect to the X-axis (main scanning direction) of the light-emitting diode array. it can. As a result, a uniform high-quality image without missing dots can be realized. In addition, the adoption of an edge-emitting light-emitting diode element structure with improved light directivity enables the realization of a light-emitting diode array head without using a lens array, which simplifies the fabrication of the array head and reduces the The yield is improved.

Further, in the present invention, the light emitting diodes at both ends are formed with a small area of the injection current region so that the injection current density is higher than those of the other light emitting diodes. Higher light output than a diode is obtained. By optimizing the shape of the light emitting diodes at both ends, the same light output as that of other light emitting diodes originally required for light intensity distribution can be realized at a fixed position, and at the same time, adjacent light emitting diode array chips Since the light is emitted with the light intensity obtained by adding the light emission intensity profiles from the light emitting diodes at the respective ends, the effect of preventing false dot omission is further improved. The present invention is preferably applied to a light-emitting diode array head that does not use a lens array, but can also be applied to a conventional light-emitting diode array head that uses a lens array.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of the present invention, and is a plan view of a light emitting diode array chip constituting a semiconductor light emitting device.

FIG. 2 is a sectional view of a stacked structure of the light emitting diode array chip shown in FIG.

FIG. 3 is a perspective view of a light emitting diode array portion of the light emitting diode array chip shown in FIG.

FIG. 4 is a diagram showing a near-field image of the semiconductor light emitting device shown in FIG.

FIG. 5 is a diagram showing the principle of a basic idea when determining the shapes of the light emitting diodes at both ends on the light emitting diode array chip of the semiconductor light emitting device according to the present invention.

FIG. 6 is a diagram showing a light intensity profile of a semiconductor light emitting device manufactured according to the principle of the basic concept of the present invention.

FIGS. 7 (1) to (5) are diagrams showing another embodiment of the present invention, and are plan views showing examples of shapes of light emitting diodes at both ends on a light emitting diode array chip of a semiconductor light emitting device. .

FIG. 8 is a perspective view showing a light emitting diode array chip arranged by a conventional connection technique.

FIG. 9 is a perspective view showing a light emitting unit substrate constituting an optical printer head using a conventional light emitting diode array.

FIG. 10 is a diagram illustrating a relationship between a light emitting unit of a light emitting diode array and an image forming point on a photoconductor surface.

FIG. 11 is a plan view showing a conventional surface-emitting light emitting diode array.

FIG. 12 is a perspective view showing a conventional edge emitting light emitting diode array.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... n-type GaAs substrate 2 ... Edge emission type light emitting diode array 2-1 to 2-256 ... Light emitting diode 2a ... Light emission end face 3 (3-1 to 3-256) ... Wiring bonding pad 7 ・ ・ ・ Emitted light 11 ・ ・ ・ First separation groove 21 ・ ・ ・ n-type GaAs buffer layer 22 ・ ・ ・ n-type Al _0.4 Ga _0.6 As clad layer 23 ・ ・ ・ Al _0.2 Ga _0.8 As activity Layer (light-emitting layer) 24 ... p-type Al _0.4 Ga _0.6 As clad layer 25 ... p-type GaAs cap layer 26 ... p + GaAs contact layer 27 ... p-type electrode 28 ... n-type electrode 31 ・ ・ ・ Insulating film

Continuation of front page (56) References JP-A-60-54484 (JP, A) JP-A-1-195068 (JP, A) JP-A-4-10582 (JP, A) JP-A-3-94481 (JP) , A) JP-A-5-42718 (JP, A) JP-A-4-107890 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00 B41J 2/44- 2/455

Claims (1)

(57) [Claims] 1. A light emitting diode comprising: a light emitting diode having at least a light emitting layer and an electrode for causing the light emitting layer to emit light; In the semiconductor light emitting device comprising a light emitting diode array formed by electrically and spatially separating each layer by the first separation groove, the light emitting diodes at both ends on the light emitting diode array chip are light emitting end faces according to Snell's law. The semiconductor light emitting device has a shape different from that of other light emitting diodes because the light emitting diode is cut at an angle of 16 ° or less.