JP2000012895A - Surface light-emitting diode array and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an light-emitting diode(LED) array where light can be restrained from leaking out of a region, other than a light-emitting region and a manufacturing method thereof. SOLUTION: A light-absorbing layer 72 is provided in a layer between an active layer 68 and a surface 58 in a range, except for light-emitting regions 86 on the surface 58, and an LED array 50 is formed including the light- absorbing layer 72, which absorbs light generated by the active layers 68. Therefore, some of the light that is generated by the active layer 68 for traveling toward the surface reaches a range except the light-emitting regions 86 and is absorbed by the light-absorbing layer 72, so that light is not projected from the surface 58, and only the light reaching the light-emitting regions 86 is projected from them. Therefore, the LED array 50, where light is properly restrained from leaking out except from the light-emitting regions 86 can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting type light emitting diode array.

[0002]

2. Description of the Related Art A plurality of semiconductor layers including a light-emitting layer are stacked on a substrate, and light generated in a plurality of current-carrying regions arranged along one direction in the light-emitting layer is transmitted to the plurality of semiconductor layers. 2. Description of the Related Art A surface-emitting type light-emitting diode array (hereinafter, referred to as an LED array) of a type in which light is extracted from a plurality of light-emitting regions provided on a light extraction surface constituted by a surface corresponding to each of the plurality of current-carrying regions is known. I have. An LED array having a monolithic structure in which portions constituting a plurality of light emitting diodes are arranged on a common substrate is used as an exposure head of an electrophotographic printer or an electrophotographic plotter, or an image display device or a virtual display device. It is used as a pixel component of a display.

[0003]

Heretofore, for the above-mentioned applications for an exposure head or the like, for example, an L-layer composed of a GaAsP-based compound semiconductor material as shown in FIGS. 1 (a) to 1 (c) is used.
An ED array 10 was used. FIGS. 1 (b) and (c)
3A and 3B show a bb section and a cc section, respectively. In the figure, an LED array 10 has, for example, an n-GaAsP epitaxial layer 14 laminated on an n-GaAs substrate 12 by crystal growth, and a diffusion portion 18 in which p-type impurities are diffused at a predetermined position on a surface 16 of the LED array 10. Further, a common n-type electrode 20 is provided on the entire lower surface of the substrate 12, and a plurality of independent p-type electrodes 22 are provided on the surface 16 for each diffusion portion 18.
The surface 16 is made of an insulating film 2 made of Si ₃ N ₄ (silicon nitride).
4 covers the entire area except for the area above the diffusion section 18, and p
The mold electrode 22 is provided on the insulating film 24, and a part thereof is located on a peripheral portion of the diffusion portion 18. Therefore, light is emitted by injecting a current into a pn junction between the n-type epitaxial layer 14 and the p-type diffusion portion 18, and the p-type electrode 22 and the insulating film 24 on the diffusion portion 18 are formed.
Light is extracted from the light emitting area 26 not covered by the light.

However, the above-described LED array 10 has a simple structure, but uses a homojunction structure with low injection efficiency and GaAsP with low luminous efficiency. Since the light generated at the boundary is absorbed in the diffusion portion 18 while traveling toward the surface 16, a high emission output cannot be obtained. Therefore, for example, when used for an exposure head of a printer or the like, the time required for the photosensitive drum to be charged to charge the toner becomes longer, so that the printing speed is increased to increase the number of printed sheets per unit time. Was difficult. Note that the light emission output can be increased by increasing the drive current, but in that case, the reliability is significantly reduced.
Moreover, since the insulating film 24 has a light transmitting property,
As shown for one dot in FIG. 2, there is also a problem that light leakage 28 occurs from outside the light emitting area 26. Such light leakage 28 causes a decrease in print quality such as crushing of fine characters in a printer. for that reason,
Since it is necessary to determine the arrangement density of the light emitting areas 26 in consideration of the light leakage 28, it is also difficult to increase the density of the dots of the printer.

On the other hand, there has been proposed a high-output LED array 30 as shown in FIG. In the figure, the LED array 30 includes, for example, an n-Al _0.7 Ga _0.3 AS clad layer 34, an Al _0.35 Ga _0.65 AS active layer 36, a p-Al _0.7 Ga _0.3 AS clad layer 38, an n- Al _0.7 Ga _0.3
An AS current block layer 40 is laminated by crystal growth, and diffusion portions 44 in which p-type impurities are diffused from a surface 42 side to predetermined positions are formed at a constant arrangement interval.
Similarly to the LED array 10, an n-type electrode 20, a p-type electrode 22 (not shown), and an insulating film 24 are provided.
6 are formed. According to such an LED array 30, a double heterojunction structure having a high injection current density is provided, and a semiconductor provided between the active layer 36 and the surface 42 provided with a sufficiently small thickness. The layers (cladding layer 38 and current blocking layer 40) do not absorb the light generated because the band gap energy is larger than that of the active layer 36, so that a higher luminous output can be obtained as compared with the LED array 10. . However, even in such a structure, the problem of the light leakage 28 from the peripheral portion of the light emitting region 26 similarly occurs, and instead, the distance between the active layer 36 functioning as the light emitting layer and the surface 42 is long. Therefore, the surface 42 is formed at an angle smaller than the critical angle.
Since the range in which light can be incident on the substrate becomes wide, the light leakage 28 tends to be more remarkable. Moreover, as mentioned above,
Even when the heterostructure is used, for example, for an exposure head, the light emission output is still insufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an LED array capable of suppressing light leakage from outside a light emitting region and a method of manufacturing the same. .

[0007]

A first aspect of the present invention to achieve the above object is to provide a semiconductor device including a plurality of semiconductor layers including a light emitting layer laminated on a substrate. A form in which light generated in a plurality of energized regions arranged along one direction is extracted from a plurality of light emitting regions provided on a surface of the plurality of semiconductor layers in correspondence with each of the plurality of energized regions. An LED array, comprising (a) a light absorbing layer that is provided in a layered manner between the light emitting layer and the surface in a range excluding the light emitting region and absorbs light generated in the light emitting layer. is there.

[0008]

According to the first aspect of the invention, the light absorbing layer is provided between the light emitting layer and the surface thereof in a layered form except for the light emitting region on the surface of the semiconductor layer, and absorbs light generated in the light emitting layer. The LED array includes the layers. Therefore, of the light generated in the light-emitting layer and traveling toward the surface of the semiconductor layer, light that reaches the region other than the light-emitting region is absorbed by the light-absorbing layer and is not emitted from the surface, and light that reaches the light-emitting region. Only is emitted from there. Therefore, LE
In the D array, light leakage from outside the light emitting region is suitably suppressed.

[0009]

Another aspect of the first invention Here, preferably, (a-1) the light absorbing layer is made of a semiconductor having a smaller band gap energy than a semiconductor constituting the light emitting layer. With this configuration, the light absorbing layer provided in a layer between the light emitting layer and the surface is formed of a semiconductor having a smaller band gap energy than the semiconductor forming the light emitting layer. Therefore, light generated in the light-emitting layer is not absorbed by a semiconductor having a higher band gap energy than that of the light-emitting layer, but is absorbed by a semiconductor having a smaller band-gap energy. Band than
By providing a light absorbing layer made of a semiconductor having a small gap energy in a range excluding a light emitting region, light traveling toward the light absorbing layer can be suitably absorbed. At this time, since the light absorption layer is made of a semiconductor, crystal growth can be performed continuously with other semiconductor layers including the light emitting layer. Therefore, it is possible to obtain an LED array having a light absorbing layer that can appropriately suppress light leakage from outside the light emitting region and can be easily formed.

Preferably, the LED array is
(b) a light reflecting layer provided between the light emitting layer and the substrate and reflecting light generated in the light emitting layer toward the surface; With this configuration, the LED array includes, in addition to the light absorbing layer, a light reflecting layer that reflects light generated in the light emitting layer toward the surface between the light emitting layer and the substrate. Therefore, light generated in the light-emitting layer and directed toward the substrate is also reflected by the light-reflective layer and directed toward the surface and extracted from the light-emitting region, so that the generated light is more efficiently extracted and the light-emission output is increased. Can be Moreover,
Since the reflective layer is provided between the light emitting layer and the substrate, the position where the light is reflected is closer to the light emitting layer than when the light is reflected on the back surface of the substrate and directed toward the semiconductor layer surface. Therefore, the range in which the incident angle of the reflected light exceeds the critical angle on the surface is reduced to a range close to the light emitting region provided directly above the energized region of the light emitting layer.
Therefore, LE having high light emission output and little leakage light emission
A D array is obtained.

Preferably, (b-1) the light reflecting layer comprises:
It is composed of a semiconductor multilayer film. With this configuration, since the light reflection layer is formed of a multilayer film in which a plurality of types of semiconductors are alternately stacked, crystal growth can be performed continuously with another plurality of semiconductor layers including the light emitting layer. Therefore, it is possible to obtain an LED array having a light reflection layer which has a high light emission output, can appropriately suppress light leakage from outside the light emitting region, and can be easily formed.

[0012]

According to a second aspect of the present invention, there is provided a method for manufacturing an LED array, comprising the steps of: The plurality of semiconductor layers including a semiconductor layer functioning as a light absorbing layer that absorbs light generated in the layer are sequentially grown on the substrate such that the light absorbing layer is located closer to the surface than the light emitting layer. Crystal growth step of stacking and stacking, (d)
And etching the surface of the semiconductor layer to form the plurality of light emitting regions from which the light absorbing layer has been removed.

[0013]

In this way, when manufacturing an LED array, a plurality of semiconductor layers including a semiconductor layer functioning as a light absorbing layer for absorbing light generated in the light emitting layer are formed in the crystal growth step. Then, the light absorbing layer is sequentially stacked on the substrate by crystal growth so that the light absorbing layer is located on the surface side of the light emitting layer, and then, in the etching process, the light absorbing layer is removed by etching from the surface of the semiconductor layer. A plurality of light emitting regions are formed. Therefore, since a plurality of light emitting regions are formed by partially removing the light absorbing layer made of a semiconductor stacked by crystal growth in the crystal growth step in the same manner as the other semiconductor layers in the etching treatment step, these light emitting layers are formed. A light absorbing layer is provided in a layered manner between the light emitting layer and the semiconductor layer surface in a range excluding the light emitting region. Therefore, the light absorption layer can be easily provided at a desired position and shape without complicating the process.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In the following examples, the dimensional ratios and the like of each part are not necessarily drawn accurately.

FIG. 4 is a diagram schematically showing a configuration of a surface-emitting type LED array 50 according to one embodiment of the present invention.
(a) is a plan view as viewed from the light emitting direction, (b) is a cross-sectional view as viewed from bb in (a), and (c) is a cross-sectional view as viewed from cc in (a). The LED array 50 constitutes a light source of an exposure head of an LED printer, for example, and has a length of about several mm in the left-right direction in FIGS. 1 (a) and 1 (b). The pieces are used in a state where they are arranged in a straight line along the longitudinal direction. In the figure, LE
The D array 50 is formed, for example, on a substrate 52 by, for example, metal organic chemical vapor deposition (MOCVD).
or an epitaxial layer 54 formed by successively growing an AlGaAs-based compound semiconductor by using a well-known crystal growth technique such as a crystal growth technique, and the back surface 56 of the substrate 52 and the front surface of the epitaxial layer 54. 58 is provided with a back electrode 60 and a front electrode 62 respectively.

The substrate 52 is a compound semiconductor made of, for example, an n-GaAs single crystal having a thickness of about 300 (μm). The epitaxial layer 54 includes a reflective layer 64, a first clad layer 66, an active layer 68, a second clad layer 70, and a light absorption layer 72, which are sequentially stacked from the substrate 52. The reflection layer 64 includes, for example, n-AlAs having a thickness of about 55.5 (nm) and n-GaAs having a thickness of about 46 (nm).
The former is a semiconductor multilayer reflective layer (DBR) in which about 30 sets are alternately stacked such that the former is on the substrate 52 side. The thickness of each of the two types of semiconductors constituting the reflective layer 64 is determined so as to be about 1 / 4n (n is the refractive index of each semiconductor) of the emission wavelength of the active layer 68. Of the light generated at 68, the light directed toward the substrate 52 is reflected toward the surface 58 by light wave interference. In this embodiment, the epitaxial layer 54 corresponds to a plurality of semiconductor layers, and the above-mentioned reflection layer 64 corresponds to a light reflection layer.

The first cladding layer 66 has a thickness of, for example, 1.0
(μm) is a compound semiconductor composed of a single crystal of n-Al _0.7 Ga _0.3 As, and the active layer 68 is composed of, for example, a single crystal of p-Al _0.35 Ga _0.65 As having a thickness of about 0.3 (μm). The second cladding layer 70 is a compound semiconductor made of a single crystal of p-Al _0.7 Ga _0.3 As having a thickness of, for example, about 1.0 (μm). Therefore, the first cladding layer 66 and the active layer 6
8 and the second cladding layer 70 are provided in a double-hetero junction structure, and a current is efficiently injected into the active layer 68 by applying a driving voltage between the back electrode 60 and the front electrode 62 as described later. Thus, the active layer 68 emits light with high luminous efficiency. In this embodiment,
The active layer 68 corresponds to a light emitting layer.

The light absorbing layer 72 is a compound semiconductor made of, for example, an n-GaAs single crystal having a thickness of about 0.5 (μm).
As shown in FIG. 5 showing the relationship between the composition and the band gap energy, in the Al _x Ga _{1 -x} As compound semiconductor, the Al mixed crystal ratio x
Is larger, the band gap energy tends to increase. Therefore, the GaAs constituting the light absorbing layer 72
Is x = 0, and x = 0.35 Al constituting the active layer 68
_{Since the} Al mixed crystal ratio x is smaller than _0.35 Ga _0.65 As, the band gap energy of the light absorption layer 72 is smaller than that of the active layer 68. For this reason, the energy of light generated by recombination light emission in a semiconductor is equal to its band energy.
Since light is absorbed by a semiconductor whose band gap energy is smaller than its own energy while being equal to the gap energy, light emitted from the active layer 68 and incident on the light absorbing layer 72 is It is absorbed by the absorption layer 72 and cannot pass therethrough. That is, the composition of the compound semiconductor forming the light absorbing layer 72 is determined by its band gap,
By setting the energy sufficiently smaller than that of the active layer 68, the light generated in the active layer 68 is determined to be absorbed by the light absorbing layer 72. In this embodiment, the band gap energy of Al _0.35 Ga _0.65 As forming the active layer 68 is about 1.86 (eV), and that of the GaAs forming the light absorbing layer 72 is about 1.42 (eV). Therefore, the difference between them is about 0.44 (eV).

Returning to FIG. 4, on the surface 58 of the epitaxial layer 54, a plurality of recesses 74 having a rectangular (square or rectangular) planar shape of, for example, about one side (μm) to several tens (μm) are formed. In the horizontal direction of FIG. 1B, that is, along the longitudinal direction of the LED array 50, they are provided at a constant center interval of about p = 20 to 120 (μm). The depth of the recess 74 is about 0.5 (μm), which is equal to the thickness of the light absorbing layer 72. For this reason,
At the position where the recess 74 is provided, the light absorbing layer 72
Is removed to expose the surface of the first cladding layer 70. The LED array 50 has a thickness of 0.1 (μ) made of silicon nitride or the like so as to cover the light absorbing layer 72.
m), an insulating film 76 having a thickness of about m) is provided, and the surface electrode 62 is provided on the insulating film 7 as shown in FIG.
6 is provided. The insulating film 76 has a perforated pattern in which a plurality of rectangular holes 78 larger than the recesses 74 are provided along the longitudinal direction of the LED array 50 at a constant center interval p similar to that of the recesses 74. It is provided in,
The plurality of recesses 74 are exposed at the center of the hole 78. Therefore, the surface 5 of the epitaxial layer 54 is located on the inner peripheral side of the hole 78 and the outer peripheral side of the recess 74.
8, that is, the surface of the light absorbing layer 72 is exposed,
A part of the surface electrode 62 on the insulating film 76 is
Is provided directly on the surface of the epitaxial layer 54 at the inner peripheral side of the substrate, and is electrically contacted with the epitaxial layer 54, that is, the light absorption layer 72.

In the epitaxial layer 54, the inner peripheral side of each of the plurality of holes 78 provided in the insulating film 76 (strictly speaking, the inner peripheral side of the inner peripheral end of the hole 78 slightly beyond the inner peripheral end of the hole 78). A plurality of diffusion portions 80 doped with p-type impurities such as Zn (zinc) at a high concentration are formed in the range (1). That is, the diffusion portion 80 is formed along the shape of the surface 58 including the concave portion 74, and the second cladding layer is formed in a range slightly closer to the inner peripheral side than the outer peripheral edge from the outer peripheral edge of the concave portion 74. The light absorbing layer 72 has a depth up to an intermediate portion of the light absorbing layer 72 in a range on an outer peripheral side thereof. Therefore, since the conductivity type of the n-type light absorbing layer 72 is inverted to the same p-type as the second cladding layer 70 in the portion where the diffusion portion 80 is formed, the LED array 50 Can be energized only through the path passing through. Therefore, the energized region 82 in the active layer 68 is
Is limited to a range immediately below a portion formed to a depth up to an intermediate portion of the second cladding layer 70. In the LED array 50, each position where the plurality of recesses 74 are provided is provided. , A plurality of energization regions 82 are provided at a center interval similar to the center interval p. That is, the light absorption layer 72
Also function as a current blocking layer (current blocking layer) for forming the current confinement structure by limiting the current-carrying region 82.

The back electrode 60 is made of, for example, Au.
An n-type electrode made of a (gold) -based material, which is provided in common throughout the LED array 50. On the other hand, the surface electrode 62 is a p-type electrode made of, for example, Al (aluminum), and a plurality of the surface electrodes 62 are provided independently for each diffusion portion 80, that is, for each energized region 82, as shown in FIG. As described above, each is in contact with the surface 58 of the epitaxial layer 54 exposed there at the inner peripheral position of the insulating film 76. Therefore, while the respective contact positions are within a range in which the conduction type of the light absorbing layer 72 is reversed and which can be supplied with electricity, the plurality of surface electrodes 62 are electrically connected to each other by being provided on the insulating film 76 as described above. Since the electrodes are electrically insulated, a current is independently injected into each of the plurality of conducting regions 82 provided in the active layer 68 for each surface electrode 68. Therefore, in the LED array 50, it can be said that a plurality of LEDs 84 independently driven for each energized area 82, that is, for each recess 74, are provided in a line with a constant center interval p.

The LED array 50 configured as described above
When a driving voltage is applied between the back surface electrode 60 and the desired front surface electrode 62, light is generated in the energized region 82 of the active layer 68 below the front surface electrode 62. The generated light travels in all directions from the current-carrying region 82. For example, in the case where light is emitted in the current-carrying region 82 located at the center in FIG. The light traveling obliquely to the stacking direction, that is, the crystal growth direction, as shown by, reaches the light absorbing layer 72 and is absorbed there because the light absorbing layer 72 is sufficiently thick at about 0.5 (μm). , From the surface 58. Also, as shown by the arrow D, the adjacent recess 7
The light traveling toward the bottom surface of 4 is not absorbed by the light absorbing layer 72, but is reflected and not emitted because the incident angle θ increases and exceeds the critical angle. Further, as shown by an arrow E, the light traveling toward the rear surface side, that is, toward the substrate 52 is reflected by the reflection layer 64.
Is reflected toward the surface 58, but also in this case, if it is going to the light absorbing layer 72, it is absorbed there, and if it is going to the bottom of the adjacent recess 74, the incident angle is Since θ exceeds the critical angle, it is reflected. The light traveling toward the substrate 52 side has a center distance p [= 20 between the light emitting regions 86.
To about 120 (μm)], the active layer 68 is a sufficiently small distance [about 1 (μm) equal to the thickness of the first cladding layer 66].
Since the light is reflected by the reflection layer 64 provided at a position away from the light source, the range in which the reflected light can be incident on the surface 58 at an incident angle sufficiently smaller than the critical angle is located on the light-emitting current-carrying region 82. Is limited to a narrow range near the recess 74.

For this reason, only the light that travels almost directly downward and is directed almost directly upward by the reflection layer 64 among the light traveling upward and the light traveling toward the back side as shown by the arrow A is the recess 74. Since the light-emitting area 86 of each LED 84 is taken out from the interior, the light-emitting area 86 of the LED 84
Only within the range. That is, since the light absorbing layer 72 is provided in a layered manner between the active layer 68 and the surface 58 in a range other than the light emitting region 86 on the surface 58, the light absorbing layer 72 is formed in advance by patterning. Light emitting area 8
Light does not leak from outside the recess 74 defined as 6. Moreover, since the light traveling toward the substrate 52 is also reflected and extracted from the surface 58, the luminous efficiency is increased as compared with the case where only the light traveling directly toward the surface 58 is extracted.

The above-described LED array 50 is manufactured by forming a plurality of components on a single substrate using a wafer process and dividing the components by dicing. Hereinafter, an example of the manufacturing process will be described with reference to FIG. First, in the crystal growth step, the reflection layer 64 is formed on the substrate 52 by using, for example, the MOCVD method.
The light absorption layer 72 is sequentially crystal-grown to produce an epitaxial wafer 88 on which the epitaxial layer 54 is formed. At this time, the light absorbing layer 7 is formed on the surface 58 of the wafer 88.
2 are provided. FIG. 6A shows this state. Next, in the insulating film forming step, the insulating film 76 is formed by growing silicon nitride to a thickness of about 0.1 (μm) on the surface 58 of the wafer 88 by, for example, a plasma CVD method or the like. FIG. 6B shows this state.
In the subsequent patterning step, a photoresist is formed in a perforated pattern having holes at positions similar to the holes 78 by using, for example, a photolithography technique. Then, in the insulating film etching step, the insulating film 76 is etched by, for example, a reactive ion etching (RIE) process using CF ₄ plasma or the like. As a result, only the portions of the photoresist that have been exposed in the holes are selectively removed, and an insulating film 76 having a hole pattern and having the holes 78 is formed. FIG. 6C shows a state at the time when the photoresist is further removed thereafter.

After patterning the insulating film 76 as described above, in the wafer etching step, the surface 5
8 is covered with a photoresist of a perforated pattern having an opening at a position corresponding to the recess 74, for example, mixed etching of ammonia and hydrogen peroxide for selectively removing AlGaAs having a small Al mixed crystal ratio. Etching is performed from the surface 58 side using a liquid. As a result, the light absorbing layer 74 made of GaAs is selectively corroded and removed at a portion exposed to the opening of the photoresist. A region 86 is formed. FIG. 6D shows this state. In the state where the insulating film 76 is provided on the surface 58 in a predetermined perforated pattern and the recess 74 is formed at a predetermined position, in the impurity diffusion step, the surface 58 is formed using, for example, a sealing method. Zn, which is a p-type impurity, is diffused from the side. As a result, Zn is doped according to the unevenness formed on the surface 58 by the recess 74, but the insulating film 76 is formed.
Since diffusion of Zn from the surface 58 is prevented in the portion where the light absorbing layer 72 is provided, the diffusion portion 80 is formed only in the inner peripheral portion of the hole 78 of the insulating film 76. Inside, a p-type region whose conductivity type is inverted is formed. FIG. 6E shows this state.

After the impurity diffusion process is performed as described above, the back surface electrode 60 and the front surface electrode 62 are fixed to the back surface 56 and the front surface 58 of the substrate, and further, a dicing process is performed to obtain the LED array 50. . In addition,
As is clear from the above description, the insulating film 76 not only insulates the surface electrode 62 but also forms the light absorbing layer 72 having a different conductivity type from the second clad layer 70 into the same p-type as the second clad layer 70. It also functions to locally form a diffusion section 80 for inverting the diffusion. However, if the insulating film 76 does not function sufficiently to control the diffusion of impurities,
It is necessary to separately form a diffusion control film on the insulating film 8 and the insulating film 76.

Here, according to the present embodiment, a layer is provided between the active layer 68 and the surface 58 in a range excluding the light emitting region 86 on the surface 58 to absorb the light generated by the active layer 68. LED array 50 including light absorbing layer 72
Is configured. Therefore, the surface 5
Of the light traveling toward 8, the light that reaches the area excluding the light emitting region 86 is absorbed by the light absorbing layer 72 and is not emitted from the surface 58, and only the light that reaches the light emitting region 86 is emitted therefrom. You. Therefore, in the LED array 50, light leakage from outside the light emitting region 86 is suitably suppressed.

In this embodiment, the light absorption layer 72 provided in a layer between the active layer 68 and the surface 58 has a band _width smaller than that of the semiconductor (Al _0.35 Ga _0.65 As) constituting the active layer 68. Semiconductor with small gap energy (GaAs)
It consists of. Therefore, the light generated in the active layer 68 is
Since the semiconductor whose band gap energy is smaller than that is absorbed by the semiconductor, the light absorption layer 72 made of a semiconductor whose band gap energy is smaller than that of the constituent material of the active layer 68 is connected to the light emitting region 86. By providing the light in the range excluding the light, the light traveling there is favorably absorbed.
At this time, since the light absorption layer 72 is also made of an AlGaAs-based compound semiconductor like the active layer 68, it can be crystal-grown continuously with a plurality of other semiconductor layers including the active layer 68. Therefore, the light absorption layer 72 for suitably suppressing light leakage from outside the light emitting region 86 can be easily formed.

In this embodiment, in addition to the light absorbing layer 72, the active layer 68 and the substrate 5
2 is provided with a reflective layer 64 for reflecting light generated by the active layer 68 toward the surface 58. Therefore, the light generated in the active layer 68 and traveling toward the substrate 52 is also reflected by the reflection layer 64 and directed to the surface 58 so that the light emitting region 8 is exposed.
Since the light is extracted from the light source 6, the efficiency of extracting the generated light is increased, and the light emission output is increased. By the way, the drive current is
When a test was performed under similar driving conditions of about 5 (mA), the light emission output of the LED array 10 shown in FIG.
About 20 (μW), 50 in the LED array 30 shown in FIG.
On the other hand, the LED array 50 of the present embodiment provided an extremely high light emission output of about 100 to 200 (μW), whereas the LED array 50 of the present embodiment was about 100 to 200 (μW). In addition, since the reflection layer 64 is provided between the active layer 68 and the substrate 52, a position where the light is reflected as compared with a case where the light is reflected on the back surface of the substrate 52 and directed to the front surface 58. Is closer to the active layer 68, the range in which the incident angle of the reflected light exceeds the critical angle on the surface 58 of the active layer 68 is closer to the light emitting region 86 provided immediately above the current-carrying region of the active layer 68. Scaled down,
Light does not leak from the adjacent light emitting region 86. Therefore, the LED array 50 having a high light emission output and a small amount of light leakage is obtained.

In this embodiment, since the reflection layer 64 is formed of a multilayer film in which a plurality of types of semiconductors are alternately stacked, crystal growth is performed continuously with a plurality of other semiconductor layers including the active layer 68. There is also the advantage that it can be done.

In this embodiment, the LED array 5
0 is manufactured in the crystal growth step in FIG.
As shown in (a), a plurality of semiconductor layers including a light absorbing layer 72 that absorbs light generated in the active layer 68 are located at the most surface layer where the light absorbing layer 72 is closer to the surface 58 than the active layer 68 is. 6 (d), the light absorbing layer 72 is partially etched by etching the wafer 88 from the surface 58 as shown in FIG. 6 (d). A plurality of light emitting regions 86 are formed, which have been removed. Therefore, the plurality of light emitting regions 86 are formed by partially removing the light absorbing layer 72 formed by crystal growth in the crystal growth step in the same manner as the other semiconductor layers in the etching process. A light absorbing layer 72 is provided in a layer form between the active layer 68 and the surface 58 in a range excluding the light emitting region 86. Therefore, the light absorbing layer 72 can be easily provided at a desired position and shape without complicating the process.

While the embodiment of the present invention has been described with reference to the drawings, the present invention can be embodied in other forms.

For example, the LED array 50 of the above embodiment
Had a double-heterojunction structure composed of an AlGaAs-based compound semiconductor; however, GaAsP-based, InP-based, and InGaAsP-based
Heterostructure, single heterostructure, or other compound semiconductors such as AlInGaP-based or GaN-based
The present invention is similarly applied to a case where the structure is a homozygous structure. Note that the layer configuration of the LED is appropriately changed according to the type of the semiconductor material, the use of the LED, and the like.

In the embodiment, the active layer 68 is made of Al
_Although the light absorption layer 72 was formed of a single crystal of GaAs and the light absorption layer 72 was formed of a single crystal of _0.35 Ga _0.65 As, the composition such as the mixed crystal ratio of the compound semiconductor forming the active layer 68 was appropriately changed according to the desired emission wavelength. The composition such as the mixed crystal ratio of the compound semiconductor forming the light absorbing layer 72 is appropriately set so that the band gap energy is smaller than that of the active layer 68.

Further, in the embodiment, the compound semiconductor formed simultaneously with the crystal growth of the epitaxial wafer 88 is used as the light absorbing layer 72. However, a material such as resin capable of absorbing light is used for the light emitting region 86. Even if it is provided on the outer peripheral side, the effect of preventing light leakage can be obtained similarly.

In the embodiment, the light absorbing layer 72 is provided on the uppermost part of the epitaxial layer 54. For example, a current blocking layer for forming a current confinement structure is separately provided on the light absorbing layer 72. By providing the light absorbing layer 7
2 may be provided in an intermediate portion of the epitaxial layer 54.

In the embodiment, the LED array 5
Each of the active layers 68 is electrically separated from each other by a plurality of LEDs 84 constituting the LED 0. The active paths 68 are electrically isolated. For example, the back surface of the reflective layer 64 (that is, the substrate 52) is etched between the LEDs 84 by etching. By removing the active layer 68 in the range up to (surface), the active layer 68 may be made physically independent.

Further, in the embodiment, the wafer 88 is
Although the crystal was grown by the OCVD method, the crystal growth method is not particularly limited, and various crystal growth methods such as a liquid phase growth (LPE) method and a molecular beam epitaxy (MBE) method can be appropriately used.

Further, in the embodiment, the reflection layer 64 for increasing the light emission output is constituted by the semiconductor multilayer film provided on the substrate 52, but the back surface 56 of the substrate 52 is made of a dielectric or metal. A reflective film may be provided. Light emitting area 86
When the center distance p is sufficiently large, the light emission output can be increased without causing light leakage, which is a particular problem even if the light is reflected by the back surface 56 of the substrate 52.

In the embodiment, the thickness of the light absorbing layer 72 is set to about 0.5 (μm). However, the thickness is set so as to sufficiently prevent light leakage from outside the light emitting region 86. It is appropriately determined according to the type of material to be used.

In the embodiment, the light absorbing layer 72 is completely removed in the light emitting region 86. However, the light absorbing layer 72 is also thinned in the light emitting region 86 as long as light is sufficiently transmitted. You may leave it. Incidentally, as in the embodiment, the semiconductor layer provided under the light absorbing layer 72 is made of Al.
When the light absorbing layer 72 is made of a material having a relatively large mixed crystal ratio and easily oxidizable, while the light absorbing layer 72 is made of a material having a relatively small Al mixed crystal ratio and which is difficult to oxidize, the light absorbing layer 72 is formed of the light emitting region 8.
6 can function as a protective film (antioxidant film) by leaving it thin. In this case, the recess 74 formed in the etching step is provided at a depth shallower than the thickness of the light absorbing layer 72.

In the embodiment, the case where the present invention is applied to the surface-emitting type LED array 50 used as a light source for exposure of a printer has been described. Is applied, there is obtained the effect of the present invention in that there is no light leakage in each light emitting diode 84 and the light emission output is increased.

Although not specifically exemplified, the present invention can be embodied with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIGS. 1A to 1C are diagrams illustrating the configuration of a conventional LED array.

FIG. 2 is a diagram illustrating light leakage of the LED array of FIG. 1 for one dot.

FIG. 3 is a cross-sectional view illustrating a configuration of another example of a conventional LED array.

FIGS. 4A and 4B are diagrams illustrating a configuration of an LED array according to an embodiment of the present invention, wherein FIG. 4A is a plan view, and FIGS.
2A shows a cross section taken along line bb and a cross section taken along line cc in FIG.

FIG. 5 is a diagram illustrating a relationship between an Al mixed crystal ratio and a band gap energy.

6 (a) to 6 (e) are views for explaining a manufacturing process of the LED array of FIG.

[Explanation of symbols]

 50: Surface-emitting type LED array 52: Substrate 54: Epitaxial layer (plural semiconductor layers) 58: Surface 64: Reflective layer 68: Active layer (light-emitting layer) 72: Light absorbing layer 82: Current-carrying area 86: Light-emitting area

Claims (5)

[Claims] 1. A semiconductor device comprising: a plurality of semiconductor layers including a light-emitting layer laminated on a substrate; light generated in a plurality of current-carrying regions disposed in the light-emitting layer along one direction; A surface-emitting light-emitting diode array of a type in which a plurality of light-emitting regions are respectively provided on a surface of a layer corresponding to each of the plurality of current-carrying regions. A surface-emitting type light-emitting diode array, comprising: a light absorbing layer provided in a layer between the surface and the light-absorbing layer and absorbing light generated in the light-emitting layer. 2. The surface-emitting light emitting diode array according to claim 1, wherein said light absorbing layer is made of a semiconductor having a smaller band gap energy than a semiconductor forming said light emitting layer. 3. A light emitting diode according to claim 1, further comprising a light reflecting layer provided between said light emitting layer and said substrate and reflecting light generated in said light emitting layer toward said surface. ·array. 4. The surface emitting light emitting diode array according to claim 3, wherein said light reflection layer is formed of a semiconductor multilayer film. 5. A light emitting device comprising: a plurality of semiconductor layers including a light emitting layer laminated on a substrate; light generated in a plurality of current-carrying regions disposed in the light emitting layer along one direction; A method of manufacturing a surface-emitting light-emitting diode array of a type in which light is extracted from a plurality of light-emitting regions provided corresponding to each of the plurality of current-carrying regions on a surface of a layer, wherein light generated in the light-emitting layer is absorbed. A crystal growth step of sequentially crystal-growing the plurality of semiconductor layers including a semiconductor layer functioning as a light absorption layer on the substrate such that the light absorption layer is located closer to the surface than the light-emitting layer. And etching the surface of the semiconductor layer to form the plurality of light-emitting regions from which the light-absorbing layer has been removed. Manufacture Law.