JP3229403B2 - 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 semiconductor light emitting device using a light emitting diode array.

[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. 11, 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. Cables 106, 107 for connection to image signals and a power source are respectively attached to the wiring members 103, 104, and 105.
Is connected. 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 imaging point of the photosensitive drum surface, as shown in FIG. 12, 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 type light emitting diode array, for example, a structure shown in FIG. 13 has been reported (Papers 1-211 of the Institute of Electrical and Electronics Engineers, 1980, pp. 1-211, and JP-A-62-238673. )), In this surface-emitting type light emitting diode array, in order to make the intensity of the light output obtained from the light emitting unit 120 uniform within the light emitting surface,
Electrodes 121 are formed at both ends or around 120.
However, in this structure, the light emitting unit 120 from which the light output is taken out
Since the electrodes 121 and 121 exist on the same plane, the width required per unit element is the sum of the width of the light emitting section 120, the width of the electrode 121, and the width of the element isolation region.
It is extremely difficult to form a high-density light emitting portion of dpi (dots per inch) or more.

Next, as an edge emitting type light emitting diode array, for example, there is one as shown in FIG. 14 (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. The light emitting portions 122 are electrically and spatially separated by a separation groove 123 formed in a direction parallel to the substrate surface in a direction perpendicular to the end surface. . In such an edge emitting light emitting diode array, the light emitting unit 12 from which light output is taken out
2 and the electrodes 124 and 125 are not on the same plane, and the width required per unit element is the sum of the width of the light emitting portion 122 and the width of the element isolation groove region. The formation of the light emitting section 122 is also possible in principle. Therefore, it can be said that an edge-emitting light-emitting diode array is suitable as a light-emitting diode array used as a light source for a high-density optical printer. Regarding the variation in light output of each light emitting diode in the light emitting diode array, the recent progress in compound semiconductor crystal growth technology has led to the uniformity of the thickness of the crystal growth structure within the substrate plane, the electrical characteristics of the film, and the like. The uniformity of the optical characteristics was improved, and the variation in the light output of each light emitting diode of the light emitting diode array in the same chip could be sufficiently reduced to within ± 5%.

[0006]

However, in the light emitting device using the conventional light emitting diode array, the electrode forming means for extracting the characteristics of the compound semiconductor crystal growth layer constituting the light emitting diode array and the heat radiation of the element are used. Non-uniformity in the light output of the light-emitting diode between chips due to variations in mounting including characteristics (the value reaches up to ± 50%). However, there is a problem that a large difference occurs in the size and print density. In particular, in the conventional edge-emitting light-emitting diode array, the light-emitting edge is formed by cleavage as shown in FIG.
Manufacturing the light emitting end face of the light emitting diode array by cleavage in this way is a technique in which the cleavage itself is not stable, so that the shape of the light emitting end face varies, and the light output from the light emitting section is scattered or absorbed. The light output of the light emitting diode array lacks uniformity due to the difference in the effect of the light emitting diode array. In addition, since the light-emitting end face is formed by cleavage, the light-emitting end face inevitably also serves as the substrate end face. Therefore, there is a problem that the light emitting end face is exposed, and the light emitting end face is easily damaged during handling for mounting, and the uniformity of light output and the yield are often further deteriorated.

The present invention has been made in view of the above circumstances, and solves the above-mentioned problems to greatly improve the uniformity of the light output of the edge-emitting light-emitting diode array, and at the same time, manufacture the light-emitting diode array. Easy to implement and easy to implement
By devising the shape of the substrate in front of the light emitting end face of the edge emitting light emitting diode and its manufacturing method, it is possible to further increase the density of the light emitting portion and make the light output uniform, and when used as a light source for an optical printer or the like. It is an object of the present invention to provide a semiconductor light emitting device capable of realizing high density and high quality printing.

[0008]

In order to achieve the above object, the present invention provides an array-like light emitting portion and an array-like equal-magnification imager.
A semiconductor light-emitting device comprising: a light-emitting portion, wherein the light-emitting portion has a stacked structure including at least a light-emitting layer of a light-emitting diode and an electrode for causing the light-emitting layer to emit light; In a semiconductor light emitting device in which a light emitting diode is formed by a light emitting diode array in which each layer is electrically and spatially separated by a plurality of first separation grooves provided at equal intervals, a light emitting end surface of the edge emitting light emitting diode The front substrate shape is terraced so as to satisfy the following equation, which is geometrically related to the angle θ of the emitted light beam.
The maximum intensity of the light output of the light emitting diode array formed
The position matches the position of the optical axis of the array-shaped unity-magnification imaging element.
Characterized in that the same-magnification imaging element is arranged
It is. Lx> Lz / tanθ: (Lx ≠ Lz / tanθ), (0 ≦ θ ≦ 90 °) Lz: Depth from the light emitting layer to the terrace surface Lx: Length from the light emitting end surface to the terrace end surface (substrate end surface)

Hereinafter, the configuration of the present invention will be described in more detail. As a rudimentary means for solving the above-mentioned problem of the prior art, instead of forming the light-emitting end face by cleavage, when forming a separation groove between adjacent elements of the light-emitting diode array, the light of the light-emitting diode is simultaneously formed. The front surface of the light-emitting diode is formed in a terrace shape in front of the light-emitting end surface, and has a monolithic structure as shown in FIG. It can be considered.
In other words, by forming the light-emitting end face by a method that does not rely on cleavage, the shape can be made uniform, and since the light-emitting end face itself does not also serve as the substrate end face by forming a terrace, the light-emitting end face can be used during handling for mounting. Since there is no damage, the non-uniformity of the light output and the yield can be improved.

Now, as shown in the relationship diagram of the light emitting portion of the light emitting diode and the image forming point of the photosensitive drum in FIG. 12, the light emitted from the light emitting diode forms an image on the photosensitive drum surface via an equal magnification image forming system. In such an optical system, the lens angle Θ (= arctan (φ / 2s): φ is the effective aperture of the lens,
(s is the object distance) is important. That is, the numerical aperture (NA = nsinΘ: n is the refractive index of the medium) of the unit magnification imaging element is MT
F (spatial frequency of the lens) is taken into consideration, so that when the angle θ of the light beam from the end face of the light emitting diode is larger than Θ, light that cannot be incident on the equal-magnification imaging element lowers the light use efficiency. Therefore, efforts have been made to reduce the angle θ of the light beam.

In general, in an edge emitting type light emitting diode, light emitted from the light emitting end face does not contribute much to light output, but rather light emission near the light emitting end face mainly contributes. It is known that the angle θ of the luminous flux in various directions is smaller than that of the surface-emitting type light emitting diode.
According to the experiments of the present inventors, the surface emitting type light emitting diode has an angle of about 2θ ≒ 120 °, whereas the edge emitting type light emitting diode has an angle of 2θ = 30 ° to 100 °. They have confirmed that an element having a desired light beam angle can be produced in this range. Under these circumstances, as a means for solving the above-mentioned conventional problems, instead of forming the light emitting end face by cleavage, the light emitting end face is formed at the same time as forming the separation groove between the adjacent elements of the light emitting diode array. Lz: depth from the light emitting layer 23 to the terrace surface 29 Lx: length from the light emitting layer end surface (light emitting end surface) 2a to the terrace end surface (substrate end surface) 1a θ : It is inevitable to design and create the shape of the substrate in front of the light emitting end face of the edge emitting light emitting diode so as to satisfy the following equation, which geometrically considers the relationship of the angle of the light flux from the light emitting layer end face 2a. Become. Lx <Lz / tan θ: (Lx ≠ Lz / tan θ), (0 ≦ θ ≦ 90 °) (1)

That is, when the expression (1) is not satisfied, there is no problem with respect to the elevation angle θ from the light emitting end face.
As shown in (a), the length L from the light emitting end surface to the substrate end
When x is long, the light from the light emitting end face is reflected on the terrace surface (etched bottom surface) and the light output is attenuated due to the loss of the light output, and then the light travels in the elevation angle θ direction. 2θ increases due to mutual interference with light emitted in the elevation angle θ direction and becomes large with respect to Θ of the unit-magnification imaging element, so that the light use efficiency decreases. Also, when Lz is shallow as shown in FIG. 5B or when θ is large as shown in FIG. 5C, the light use efficiency is reduced for the same reason. Therefore, forming the substrate shape in front of the light-emitting end face of the edge-emitting light emitting diode so as to satisfy the expression (1) can be achieved by making the angle θ of the luminous flux from the light-emitting end face of the edge-emitting light-emitting diode equal in magnification. It is extremely important for effective control of Θ. In addition, the reason why Lx = Lz / tanθ is excluded in the equation (1) is that when the equality is satisfied, light is reflected at the terrace end in the depression angle direction from the light emitting end face.

By the way, even if the substrate is designed and manufactured in front of the light emitting end face of the edge emitting light emitting diode so as to satisfy the conditional expression (1), there are the following problems in manufacturing. That is, in the current manufacturing process of compound semiconductor elements, a single crystal wafer having a size of 2 inches is usually used, and light emitting devices such as the edge emitting light emitting diode array described above are efficiently arranged on this wafer as shown in FIG. I do. When the array elements manufactured on the wafer are cut out from the wafer, they are cut along the scrub line by the aforementioned cleavage technique or dicing technique. At this time, in order to satisfy the conditional expression (1), the dimensional processing accuracy of Lx at the time of cutting out from the wafer is an important point. However, since the cleavage technique is an unstable technique as described above, it is difficult to obtain dimensional processing accuracy of Lx. On the other hand, the dicing technology, which is more stable than the cleavage technology, has a disk-shaped blade blade of 30,000.
Since the wafer is cut out from the wafer while being rotated at a high speed of about rpm, chipping is apt to occur in the edge emitting light emitting diode array chip, and the light emitting surface of the edge emitting light emitting diode is damaged, and Lx
It is difficult to achieve sufficient dimensional accuracy.

Here, Table 1 shows that Lx = Lz / tan θ: (0
≦ θ ≦ 90 °).

[Table 1] That is, as shown in Table 1, the specific required dimensional accuracy is, for example, when the angle θ of the light beam is 15 ° and the depth Lz from the light emitting layer to the etching bottom is 1 μm, The length Lx to the substrate edge is 3.7 μm
Reflection from the terrace surface can be prevented by the following. Similarly, when the light beam angle θ is 50 °, Lz = 1 μm
Therefore, it is necessary to make Lx = 0.8 μm or less.

Therefore, in order to realize the present invention, considerable dimensional accuracy of Lx is required at the time of cutting out from a wafer. Therefore, conditional expression (1)
It is difficult to satisfy the above by using the current cleavage technology and dicing technology. According to our experimental results, it has been confirmed that Lx can be reduced to about 10 μm by the dicing technique, but in reality, when Lx is 10 μm and the angle θ of the light beam is 50 °, Lz is set to 12 μm or more. There is a need. However, etching of 12 μm or more requires a long dry etching time (about 1 μm / 10 min).
As a result, the manufacturing cost increases. In addition, since the step between the light emitting element portion and the metal wiring portion is 12 μm or more, there is a disadvantage that the metal wiring is likely to be disconnected. Therefore, it is not desirable to find a technical path only for the formation of the depth Lz from the light emitting layer to the etching bottom.

On the other hand, when Lx = 10 μm, the angle θ of the light beam is 1
In the case of 5 °, Lz only needs to be 2.7 μm or more, so that the dry etching time does not become extremely long. However, regarding the control of the angle θ of the light beam, MO
It depends on an epitaxial growth technique for forming an element layer structure by a CVD method or the like. In order to make θ = 15 ° or less, light is emitted over all elements of an edge-emitting light emitting diode array (over the entire area of a 2-inch wafer). The structure must satisfy the propagation conditions, and the active layer must be uniformly and stably realized with a thickness of 500 ° or less. However, at present, it is possible to reduce the angle θ of the light beam to about 15 ° or less at the laboratory level, but it is difficult to incorporate it into the mass production level.

The present invention solves the above-mentioned drawbacks to greatly improve the uniformity of the light output of the edge-emitting light-emitting diode array, and at the same time, to make it easier to manufacture and mount Lx. , Lz, and θ are geometrically considered, a substrate shape in front of a light emitting end face of an edge emitting light emitting diode for satisfying the conditional expression, and a method of manufacturing the same. Here, in the present invention, the substrate shape in front of the light emitting end face of the edge emitting light emitting diode is formed in a terrace shape geometrically related to the angle θ of the emitted light beam,
Further, the terrace shape related to the geometry is formed so as to satisfy the following expression (2). Lx> Lz / tan θ: (Lx ≠ Lz / tan θ), (0 ≦ θ ≦ 90 °) (2) That is, in the present invention, the formula (1) is not satisfied, but rather (2). Forming a substrate shape in front of the light emitting end face of the edge emitting light emitting diode so as to satisfy the formula,
Further, it is an object of the present invention to provide an industrially advantageous edge-emitting light-emitting diode array by compensating for the disadvantages at that time.

By the way, when the substrate shape in front of the light emitting end face is formed so as to satisfy the expression (2), FIG.
As shown in FIGS. 5 (a), 5 (b) and 5 (c), light is reflected at the terrace end in the depression angle direction from the light emitting end face. On the other hand, the angle θ of the light beam becomes large, and the light use efficiency is reduced. FIG. 6 shows a far-field image (FFP) when the substrate shape in front of the light emitting end face of the edge emitting light emitting diode is formed so as to satisfy the expression (2). Above the element, after the light coming out of the element is reflected on the terrace surface,
There are side lobes that are expected to have emerged due to mutual interference with upwardly directed light emerging above the device. This side lobe causes the angle θ of the light beam to be larger than Θ of the unit magnification imaging element, and causes a reduction in light use efficiency. It can also be seen that the light intensity peak position has shifted upward from the device. This is due to the fact that the distribution of the far-field image (FFP) is biased upward from the element due to the appearance of the side lobe.

The point of the technology is whether or not the light intensity peak position can be made uniform when the edge emitting type light emitting diode array formed so as to satisfy the expression (2) is used as a light source for an optical printer. Is shown. That is, as shown in the relationship diagram between the light emitting portion of the light emitting diode and the image forming point of the photosensitive drum in FIG. 12, the light emitted from the light emitting diode is imaged on the photosensitive drum surface via the same magnification image forming system. However, in such an optical system, if the optical axis of the light-emitting diode array does not coincide with the optical axis of the array-type equal-magnification imaging system, not only the light utilization efficiency is reduced, but also the photosensitive drum is formed. This indicates that the light intensity distribution on the image plane becomes non-uniform. Therefore, it suffices to solve this problem, instead of trying to satisfy equation (1).
Rather, the substrate shape is formed in front of the light-emitting end face of the edge-emitting light emitting diode so as to satisfy the expression (2), and the array is formed so as to be substantially horizontal above the light emitting region (active layer) of the light emitting diode. If an optical printer head is mounted by aligning the optical axes by arranging the same-magnification imaging elements, it is possible to provide an industrially advantageous edge-emitting light-emitting diode array.

[0020]

As described above, in the present invention, the substrate shape in front of the light emitting end face of the edge emitting light emitting diode is made into a terrace shape satisfying the expression (2), which is shown in FIG. This is nothing less than accepting a), (b) and (c). Further, in this case, as described above, the light utilization efficiency is reduced due to the light that cannot be incident on the equal-magnification imaging element. However, the ease of fabrication is unparalleled, and above all, the advantage of having a uniform light intensity profile in the array element and the maximum light intensity position in the array direction is greater. Further, by forming the light emitting end face by a method that does not rely on cleavage, the light emitting end face can be formed in a high density and uniform shape, so that the light output of the edge emitting type light emitting diode array can be made more uniform. further,
By making the shape of the substrate in front of the light emitting end surface of the end surface light emitting diode array into a long terrace shape, the light emitting end surface itself does not also serve as the substrate end surface, so that the light emitting end surface is not damaged during handling for mounting. Therefore, the uniformity of the light output and the yield of the device can be improved. In addition, by forming a geometrically-considered terrace in front of the light-emitting end face, it is possible to positively control the light emission direction of the edge-emitting light-emitting diode array to make the light profile uniform, and to increase the size of the printed dot. High quality images with uniform pod print density can be realized.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a plan view of a semiconductor light emitting device (light emitting diode array chip) showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of the semiconductor light emitting device shown in FIG. FIG. 2 is a partial perspective view of the semiconductor light emitting device (light emitting diode array chip) shown in FIG. In the light emitting diode array chip shown in FIG. 1, the edge emitting light emitting diode array 2 (2-1 to 2-256) has a dot density equivalent to 600 dpi, and 256 elements are formed on the n-type GaAs substrate 1. The laminated structure of the light emitting diode array 2 is shown in FIG.
As shown in FIG. 3, n is formed on the substrate 1 by MOVPE.
Buffer layer 21, n-type Al _0.4 Ga _0.6 As clad layer
22, an Al _0.2 Ga _0.8 As active layer 23 as a light emitting layer, p-type A
l _0.4 Ga _0.6 As clad layer 24, p-type GaAs cap layer 25, and p + -type Ga doped heavily with zinc.
The As contact layer 26 is formed by a laminated structure including a plurality of layers.

Since the present laminated structure includes a so-called double hetero structure, the angles θ of the emitted light beams at the depression angle and the elevation angle are equal. In addition, as shown in FIG.
That is, the first separation groove 11 reaching the substrate from the upper surface of the contact layer 26 to the surface of the substrate 1 and at right angles to the array direction.
Are formed by a dry etching method using a chlorine-based gas, and 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. . At the same time, the substrate in front of the light emitting end face 2a of the light emitting diode is formed in a terrace (29) shape as shown in FIG. At this time, a dry etching mask (for example, a resist, a dielectric film such as SiO ₂ , a metal such as Cr or Ti, or a combination thereof) so as to satisfy the geometrical expression (2) according to the present invention. Should be used. The light emitting end face 2a of each light emitting diode (2-1 to 2-256) of the light emitting diode array 2 is perpendicular to the substrate surface and parallel to the array direction, and is a side (terrace end surface) 1a of the substrate 1. Is located at a position according to the present invention close to.

On the contact layer 26 of each light emitting diode of the light emitting diode array 2, Au—Zn / Au
A p-type electrode 27 made of Au-Ge / Ni / Au is formed on the back surface of the substrate 1. As shown in FIGS. 2 and 3, the surface of the edge emitting light emitting diode array 2 from the side opposite to the light emitting end face 2a to the substrate surface behind the edge emitting light emitting diode array 2 is made of SiO ₂ or the like. An insulating film 4 is formed, and wiring bonding pads 3 (3-1 to 3-256) are provided on the insulating film 4 for each light emitting diode. The electrode 27 is electrically connected to the wiring bonding pad 3 (3-1 to 3-256). This protects the element from damage due to bonding, and prevents deterioration in luminous efficiency. The wiring bonding pads 3 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. Since the edge-emitting light-emitting diode array 2 thus configured is manufactured by the MOVPE method having excellent uniformity of the film characteristics, the variation of the light output within the same light-emitting diode array chip is ± 5. % Or less.

[Embodiment 2] FIG. 9 is a partial perspective view of a semiconductor light emitting device (light emitting diode array chip) showing another embodiment of the present invention. In the first embodiment, while the surface of the terrace 29 in front of the light emitting end face of the light emitting diode array is the surface of the GaAs substrate 1 after the dry etching,
In this embodiment, as shown in FIG.
It is covered with an insulating film 4 such as O ₂ . Thereby, the scattering of light reflected on the terrace surface can be reduced, so that a light-emitting diode array having a uniform far-field pattern (FFP) can be realized.

Embodiment 3 FIG. 10 is a partial perspective view of a semiconductor light emitting device (light emitting diode array chip) showing still another embodiment of the present invention. In this embodiment, FIG.
As shown in FIG. 0, the terrace surface 29 ″ in front of the light emitting end face of the light emitting diode array is covered with an insulating film 4 such as SiO ₂ and a metal material 30 such as Au formed thereon.
This not only reduces the scattering of light reflected on the terrace surface 29 '', but also suppresses light absorption,
A light emitting diode array having a uniform far-field pattern (FFP) can be realized, and at the same time, a decrease in light output can be suppressed.

In the first to third embodiments, 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, is configured such that n-type is p-type and p-type is n-type. Is also good. Further, the light-emitting end face of the edge-emitting light-emitting diode array 2 on the light-emitting diode array chip and the first separation groove 11 for separating the light-emitting diodes of the edge-emitting light-emitting diode array 2 from each other are perpendicular to the substrate 1 surface. However, it is not always necessary to be vertical, and any surface may be used as long as it is a substantially vertical surface or a surface that is not parallel to the active layer 23. The first separation groove 11 is formed so as to reach the substrate 1 from the surface of the laminated structure. However, the first separation groove 11 is essentially formed on the active layer 23 of the adjacent edge emitting light emitting diode.
Since it is only necessary to electrically separate the gaps, the bottom of the groove does not necessarily have to reach the substrate 1; if the groove reaches the cladding layer 22 through the active layer 23, it will function satisfactorily.

[0027]

As described above, according to the present invention, the shape of the substrate in front of the light emitting end face of the edge emitting light emitting diode array constituting the light emitting portion of the semiconductor light emitting device is geometrically related to the light beam angle θ. Shaped like a terrace to satisfy the following formula
By form was, Lx> Lz / tanθ: ( Lx ≠ Lz / tanθ), (0 ≦ θ ≦ 90 °) ··· (2) Lz: depth Lx from the light emitting layer to the terrace surfaces: from the light emitting end face Length to terrace end (substrate end)
The shape of the light-emitting end face can be made uniform, and the light-emitting end face can be formed at a high density by forming the light-emitting end face by a method that does not rely on cleavage (dry etching method). In addition, since the shape of the light emitting end face can be made uniform, the light output of the edge emitting light emitting diode array can be further uniformed. Soshi
The maximum intensity position of the light output of the light emitting diode array
In order to match the position of the optical axis of the ray-shaped equal-magnification imaging element,
By placing an imaging element, an image is formed on the photoconductor
The intensity of each bit becomes uniform. Further, the shape of the substrate in front of the light emitting end face of the edge emitting light emitting diode array ,
(2) Ri by <br/> to the formed terraced so as to satisfy the equation, by simple design means can uniformly emitting end face shape, and since the light emitting end surface itself does not serve as the substrate end face, of the mounting The light-emitting end face is not damaged during handling. Therefore, the uniformity of the light output and the yield can be improved. As described above, according to the present invention, it is possible to make the light output of the edge emitting type light emitting diode array constituting the light emitting portion of the semiconductor light emitting device uniform, and when the light emitting device is used as a light source for an optical printer or the like, the print dot is printed. It is possible to realize a high quality image with uniform size and print density.

[0028] Here, since the verified experimentally for effects of the present invention, and the results are shown in below. The sample prepared for the experiment was Lz = 2.5 μm, Lx = 25 μm, and θ = 20 °. Lx = 25> 2.5 / tan20 ° = Lz / tanθ: (Lx ≠ Lz / tanθ) , (0 ≦ θ ≦ 90 °), which satisfies the expression (2). FIG. 7 is a view spatially showing a far-field pattern (FFP) of each light-emitting diode measured using the sample (edge-emitting light-emitting diode array element) arranged in the array direction. As shown in FIG.
Above the element, side lobes appearing due to interaction with light traveling directly upward from the element after light coming below the element is reflected off the terrace surface. On the other hand, the maximum light intensity position in the array direction is uniform between bits,
The position and shape of the side lobes are also uniform. As described above, in the edge emitting light emitting diode array manufactured according to the present invention, although a side lobe is observed, a uniform optical output is obtained between bits. As described above, the validity of the principle of the present invention is clarified by experimental verification, and that the edge-emitting light-emitting diode array manufactured according to the present invention has much superior light output uniformity as compared with the related art. Was confirmed.

[Brief description of the drawings]

FIG. 1 is a plan view of a semiconductor light emitting device (light emitting diode array chip) showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA ′ of the semiconductor light emitting device shown in FIG.

FIG. 3 is a partial perspective view of the semiconductor light emitting device (light emitting diode array chip) shown in FIG.

FIG. 4 is an explanatory cross-sectional view of a light-emitting diode array showing the principle of the basic concept of the present invention.

5A and 5B are cross-sectional explanatory views of a light-emitting diode array portion showing the principle of the basic concept of the present invention, and FIG. 5A shows a case where a length Lx of a terrace portion from a light-emitting end surface of a light-emitting diode to a substrate end surface is long. (B) is a diagram showing the progress of light when the depth Lz from the light emitting layer to the terrace surface is small, and (c) is a diagram showing the progress of light when the angle θ of the emitted light beam is large. FIG.

FIG. 6 shows a far-field image (FFP) of a light emitting diode formed using the present invention.

FIG. 7 is a view spatially showing a far-field image (FFP) of a light-emitting diode of a light-emitting diode array element formed by using the present invention, arranged in the array direction.

FIG. 8 is a perspective view showing a light emitting diode array chip group formed on a single crystal wafer.

FIG. 9 is a partial perspective view of a semiconductor light emitting device (light emitting diode array chip) showing another embodiment of the present invention.

FIG. 10 is a partial perspective view of a semiconductor light emitting device (light emitting diode array chip) showing still another embodiment of the present invention.

FIG. 11 is a perspective view showing a light emitting unit substrate constituting an optical printer head using a conventional light emitting diode array.

FIG. 12 is an explanatory 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. 13 is a plan view showing a conventional surface-emitting light emitting diode array.

FIG. 14 is a perspective view showing a conventional edge emitting light emitting diode array.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... n-type GaAs substrate 1a ... substrate end surface 2 (2-1 to 2-256) ... end surface light emitting diode array 2a ... light emitting end surface 3 (3-1 to 3-256) ... Bonding pads for wiring 4 ... Insulating film 11 ... First isolation groove 21 ... n-type buffer layer 22 ... n-type Al _0.4 Ga _0.6 As clad layer 23 ... Al _0.2 Ga _0.8 As Active layer (light emitting layer) 24: p-type Al _0.4 Ga _0.6 As clad layer 25: p-type GaAs cap layer 26: p + -type GaAs contact layer 27: p-type electrode 28: n Type electrode 29 ・ ・ ・ Terrace

Continued on the front page (56) References JP-A-62-238673 (JP, A) JP-A-1-137677 (JP, A) JP-A-4-89354 (JP, U) (58) Fields surveyed (Int .Cl. ⁷ , DB name) H01L 33/00

Claims (1)

(57) [Claims] 1. An array-like light-emitting portion and an array-like equal-size imaging element
Wherein the light emitting portion has a laminated structure including at least a light emitting layer of a light emitting diode and an electrode for causing the light emitting layer to emit light, and an edge emitting light emitting device capable of obtaining a light output from an end face of the stacked layer. In a semiconductor light emitting device including a light emitting diode array in which diodes are electrically and spatially separated from each other by a plurality of first separation grooves provided at equal intervals, a light emitting end face forward of the edge emitting light emitting diode is provided. The following equation geometrically relates the substrate shape to the angle θ of the emitted light beam
Was formed into a terrace shape so as to satisfy, Lx> Lz / tanθ: ( Lx ≠ Lz / tanθ), (0 ≦ θ ≦ 90 °) Lz: depth Lx from the light emitting layer to the terrace surfaces: the terrace from the light emitting end face Length up to the end face (board end face)
Said light emitting diode maximum intensity position and front of the light output of the array
The array-shaped equal-magnification imaging element is adjusted so that the position of the optical axis is aligned.
A semiconductor light-emitting device comprising a unit- size imaging element .