JP3517101B2 - Light emitting diode array - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode array, and more particularly to a light emitting diode array used as a light source for exposing a photosensitive drum for a page printer. 2. Description of the Related Art FIGS. 4 and 5 show a conventional light emitting diode array. FIG.
FIG. 5 shows a plan view of the light emitting diode array, and FIG.
Indicates a cross section of one light emitting element. 4 and 5, 11 is a substrate, 12 is a semiconductor layer of one conductivity type, 13 is a semiconductor layer of the opposite conductivity type, 14 is an individual electrode, 15 is a common electrode, 16
Is an insulating film. [0003] On a substrate 11, an island-shaped semiconductor layer in which a one-conductivity-type semiconductor layer 12 made of gallium arsenide or the like and a reverse-conductivity-type semiconductor layer 13 are stacked is arranged in a row. The opposite conductivity type semiconductor layer 13 is formed in a smaller area than the one conductivity type semiconductor layer 12 so that a part of the one conductivity type semiconductor layer 12 is exposed. A common electrode 15 is connected to an exposed portion of the one conductivity type semiconductor layer 12, and an individual electrode 14 is connected to an upper portion of the opposite conductivity type semiconductor layer 13. As shown in FIG. 4, one individual electrode 14 is provided to be connected to each adjacent opposite conductive semiconductor layer 13, and one conductive semiconductor layer below the opposite conductive semiconductor layer 13 connected to the same individual electrode 14. 12 are configured to be separately connected to the common electrodes 15a and 15b. Each light emitting diode is composed of the island-shaped semiconductor layer, the individual electrode 14 and the common electrode 15. A combination of the individual electrode 14 and the common electrode 15 is selected, and a current flows from the individual electrode 14 to the common electrodes 15a and 15b to selectively emit light from a plurality of light emitting diodes, thereby exposing the photosensitive drum for a page printer. Used as a light source. However, in this conventional light emitting diode array, when patterning the opposite conductivity type semiconductor layer 13 so that a part of the one conductivity type semiconductor layer 12 is exposed, the mask pattern is formed in the short direction of the substrate 1. When the misalignment occurs, the opposite conductivity type semiconductor layer 13 becomes larger or smaller for each island-shaped semiconductor layer, so that light emitting diodes having different light emitting areas are formed, and there is a problem that light emission variation occurs. . Therefore, as shown in FIG. 6, a reverse conductivity type semiconductor layer 13 is formed on the one conductivity type semiconductor layer so that the same side of the one conductivity type semiconductor layer 12 is exposed. There is also a light emitting diode array in which the individual electrodes 14 are connected from the same side in the direction intersecting, and the individual electrodes 14 are alternately distributed and drawn out on both sides in the direction intersecting with the arrangement direction of the island-shaped semiconductor layers. Also in this case, the common electrode 15 is distributed and drawn out on both sides in a direction intersecting the arrangement direction of the island-shaped semiconductor layers. As described above, when the exposed portion of the one conductivity type semiconductor layer 12 is provided on the same side in the direction intersecting the arrangement direction of the island-shaped semiconductor layers, the position of the mask pattern when patterning the opposite conductivity type semiconductor layer 13 is increased. Even if the displacement occurs, it is possible to prevent light emission variation between the light emitting diodes. That is, even when the mask pattern is misaligned in the lateral direction of the substrate 11 when patterning the opposite conductivity type semiconductor layer 13, all the opposite conductivity type semiconductor layers become larger or smaller. Light emission variation does not occur for each light emitting diode. However, in this conventional light-emitting diode array, light-emitting diodes having electrode wiring patterns on both sides of the island-like semiconductor layer and light-emitting diodes having electrode wiring patterns on only one side of the island-like semiconductor layer coexist. However, depending on the presence or absence of the wiring pattern of the electrodes, the reflection state of the emitted light becomes irregular, which causes a problem that light emission variation occurs. The present invention has been made in view of such a problem of the prior art, and has solved the problem that light emission variation occurs in a light emitting diode due to the presence or absence of an electrode wiring pattern near an island-shaped semiconductor layer. An object is to provide a light emitting diode array. In order to achieve the above object, according to a light emitting diode array according to the present invention, a plurality of islands in which a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are stacked. The semiconductor layers are arranged in a row on a substrate, and a common electrode is connected to the one-conductivity-type semiconductor layer, and the individual electrodes are connected to the opposite-conductivity-type semiconductor layer. Connected to the same individual electrode for each of the adjacent opposite conductivity type semiconductor layers from the same side in a direction intersecting with the arrangement direction of the island-shaped semiconductor layers and alternately pulled out to the opposite end face side of the substrate, The common electrodes are provided on both sides in a direction intersecting the arrangement direction of the layers, and a lower conductive type semiconductor layer connected to the same individual electrode from a side opposite to the direction intersecting the arrangement direction of the island-shaped semiconductor layers. Conductive type half Each conductor layer was alternately divided and connected to the common electrodes on both sides, and dummy wires were provided between the island-shaped semiconductor layers through which wires for connecting to the individual electrodes and the common electrode did not pass. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing the light emitting diode array according to the present invention in a plan view, and FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 1. 1 to 3, 1 is a substrate, 2 is a semiconductor layer of one conductivity type,
3 is a reverse conductivity type semiconductor layer, 4 is an individual electrode, 5 is a common electrode,
6 is an insulating film and 7 is a dummy wiring. The substrate 1 is formed of a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs) or a single crystal insulating substrate such as sapphire (Al ₂ O ₃ ). In the case of a single crystal semiconductor substrate, a substrate whose (100) plane is turned off by 2 to 7 ° in the <011> direction is preferably used. In the case of sapphire, a C-plane substrate or the like is preferably used. The one conductivity type semiconductor layer 2 includes a buffer layer 2a,
It comprises an ohmic contact layer 2b and a cladding layer 2c. The buffer layer 2a has a thickness of about 1 to 3 μm, and the ohmic contact layer 2b has a thickness of 0.01 to 3 μm.
The cladding layer 2c is formed to a thickness of about 0.2 to 0.4 μm. The buffer layer 2a and the ohmic contact layer 2b are formed of gallium arsenide or the like, and the cladding layer 2c is formed of aluminum gallium arsenide (AlGaAs) or the like. The ohmic contact layer 2b is made of one conductivity type semiconductor impurity such as silicon (Si) or selenium (Se) at 1 × 10 ¹⁹ to 10 ^{22 at.}
contains about ms / cm ^3, the cladding layer 2c is one conductivity type semiconductor impurity such as silicon (Si) or selenium (Se) containing approximately ^{1 × 10 16 ~10 19 atoms /} cm 3. The buffer layer 2a is provided to prevent misfit dislocation due to a difference in lattice constant between the substrate 1 and the island-shaped semiconductor layers 2, 3, and does not necessarily need to contain semiconductor impurities. The opposite conductivity type semiconductor layer 3 includes the light emitting layer 3a, the second
And a second ohmic contact layer 3c. Light emitting layer 3a and second cladding layer 3
b is formed to a thickness of about 0.2 to 0.4 μm, and the second ohmic contact layer 3c is formed to a thickness of about 0.01 to 0.1 μm. The light emitting layer 3a and the second cladding layer 3b are formed of aluminum gallium arsenide or the like.
Is formed of gallium arsenide or the like. The light emitting layer 3a and the second cladding layer 3b are made of AlA in consideration of an electron confinement effect and a light extraction effect.
It is configured such that the mixed crystal ratio of s and GaAs is different. The light emitting layer 3a and the second cladding layer 3b contain opposite conductive semiconductor impurities such as zinc (Zn) at 1 × 10 ¹⁶ to 10 ¹⁹ atoms /.
cm ³ , the second ohmic contact layer 3c
Represents 1 × 10 of a reverse conductivity type semiconductor impurity such as zinc (Zn).
^It contains about ¹⁹ to 10 ²² atoms / cm ³ . The insulating film 6 is made of a silicon nitride (SiN _x ) film or the like and has a thickness of about 3000 °. The individual electrode 4 and the common electrode 5 are made of gold (Au) or a two-layer film of gold (Au) and chromium (Cr), and have a thickness of about 1 μm. A plurality of island-shaped semiconductor layers are arranged in a row on a substrate 1, and a semiconductor layer 3 of the opposite conductivity type is formed such that the same side of the semiconductor layer 2 of one conductivity type is exposed. The individual electrodes 4 are connected to the opposite conductivity type semiconductor layer 3 from the same side in the direction intersecting the arrangement direction of the island-shaped semiconductor layers, and are separated and drawn out on both sides in the direction intersecting the arrangement direction of the island-shaped semiconductor layers. ing. In addition, the one conductivity type semiconductor layer 2 located under the opposite conductivity type semiconductor layer 3 connected to the same individual electrode 4 is alternately distributed so as to be connected to different common electrodes 5a and 5b. It is pulled out to the end face side. A combination of the individual electrode 4 and the common electrode 5 is selected, and a current is supplied from the individual electrode 4 to the common electrode 5 to selectively emit light, thereby being used as an exposure light source for a photosensitive drum for a page printer. By providing the exposed portion of the one-conductivity-type semiconductor layer 2 on the same side in the direction intersecting with the arrangement direction of the island-shaped semiconductor layers, the reverse conductivity due to the pattern shift when the opposite-conductivity-type semiconductor layer 3 is formed is provided. Variations in the area of the conductive semiconductor layer can be prevented, and as a result, variations in light emission for each light emitting diode can be prevented. Further, the exposed portion of the one conductivity type semiconductor layer 2 is provided on the same side in a direction intersecting the arrangement direction of the island-shaped semiconductor layers,
When the individual electrodes 4 and the common electrode 5 are alternately pulled out to the end face side in the longitudinal direction of the semiconductor substrate 1, an island-shaped semiconductor layer having electrode wiring patterns on both sides and an island-shaped layer having electrode wiring patterns on only one side are provided. A semiconductor layer is formed. In the light emitting diode array shown in FIG. 1, for example, the second, third, fourth, seventh, and eighth island-shaped semiconductor layers 2 , 3 , 4 , 7 , 8,
Has electrode wiring patterns on both sides thereof, but the fifth, sixth, ninth, and tenth island-shaped semiconductor layers 5 , 6 , and.
9 and 10 have an electrode wiring pattern only on one side thereof. Therefore, in the present invention, the fifth and sixth island-shaped semiconductor layers 5 , 6 and the ninth and tenth island-shaped semiconductor layers
Dummy wirings 7 are provided between 9 and 10, and the wiring patterns of the electrodes are located on both sides of all the island-shaped semiconductor layers except for the endmost island-shaped semiconductor layers. It is desirable that the width, thickness, and material of the dummy wiring 7 be exactly the same as those of the individual electrode 4 and the common electrode 5 from the viewpoint of uniformity of light reflection and the manufacturing process. That is, it is made of gold (Au) or a two-layer film of gold (Au) and chromium (Cr) and has a thickness of about 1 μm and a width of about 1 to 20 μm. The length may be equal to or longer than the length of each island-shaped semiconductor layer. Further, the dummy wiring 7 is only for appropriately reflecting light from the island-shaped semiconductor layer, and does not necessarily need to be connected to another wiring member. As described above, when the electrode wiring patterns and the dummy wirings 7 exist on both sides of all the island-shaped semiconductor layers, the reflection state of light emitted from all the island-shaped semiconductor layers becomes the same,
Emission variations between light emitting diodes are eliminated. Next, a method for manufacturing the above-described semiconductor light emitting device will be described. First, a semiconductor layer 2 of one conductivity type and a semiconductor layer 3 of opposite conductivity type are sequentially formed on a single crystal substrate 1 by MOCVD or the like. When these semiconductor layers 2 and 3 are formed,
First, the substrate temperature is set to 400 to 500 ° C. and 200 to 2
After forming an amorphous gallium arsenide film to a thickness of 000 °, the substrate temperature is raised to 700 to 900 ° C. to form semiconductor layers 2 and 3 having a desired thickness. In this case, TMG ((C
H ₃ ) ₃ Ga), TEG ((C ₂ H ₅ ) ₃ Ga), arsine (AsH ₃ ), TMA ((CH ₃ ) ₃ Al), TE
A ((C ₂ H ₅ ) ₃ Al) or the like is used, and silane (SiH ₄ ), selenium hydride (SeH ₂ ), DMZ ((CH ₃ ) ₃ Zn) or the like is used as a gas for controlling the conductivity type. Hydrogen (H ₂ ) is used as the carrier gas. Next, the semiconductor layers 2 and 3 are patterned in an island shape so that adjacent elements are electrically separated from each other, and a connection portion between the one conductivity type semiconductor layer 2 and the common electrode 5 is exposed. Thus, a part of the opposite conductivity type semiconductor layer 3 is patterned. Such etching of the semiconductor layers 2 and 3 is performed by wet etching using a sulfuric acid-hydrogen peroxide-based etchant, dry etching using CCl ₂ F ₂ gas, or the like. Next, the insulating film 6 is made of silane gas (SiH ₄ ).
After forming the semiconductor layers 2 and 3 by dry etching using a hydrofluoric acid (HF) -based etchant or dry etching using a CF ₄ gas, the electrodes are formed by a plasma CVD method or the like using an ammonia gas (NH ₃ ). Contact holes C ₁ and C ₂ (see FIG. 3), which are connection portions of 4, 5 are formed. Finally, the individual electrodes 4, the common electrodes 5, and the dummy wirings 7 are formed by vapor deposition or sputtering, and are completed by patterning. As described above, according to the light emitting diode array according to the present invention, the opposite conductivity type semiconductor adjacent from the same side in the direction intersecting the arrangement direction of the island-shaped semiconductor layers formed on the substrate is provided. Each layer is connected to the same individual electrode and alternately pulled out to the opposite end face side of the substrate, and common electrodes are provided on both sides in a direction intersecting with the arrangement direction of the island-like semiconductor layers, and the arrangement direction of the island-like semiconductor layers is From the opposite side of the intersecting direction, alternately connecting to the common electrodes on both sides for each one conductive semiconductor layer below the opposite conductive semiconductor layer connected to the same individual electrode, and connecting to this individual electrode and the common electrode Since the dummy wiring is provided between the island-shaped semiconductor layers through which the wiring for the wiring does not pass, the wiring pattern of the electrode or the dummy wiring is located on both sides of all the island-shaped semiconductor layers except for the end portion, and the island-shaped semiconductor layer is formed. Nearby The reflection state of the light emitted from the island-shaped semiconductor layer does not differ depending on the presence or absence of the wiring material, and it becomes unnecessary or easy to correct the emission state by the drive circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing one embodiment of a light emitting diode array according to the present invention. FIG. 2 is a sectional view taken along line AA in FIG. FIG. 3 is a sectional view taken along line BB in FIG. 1; FIG. 4 is a plan view showing a conventional light emitting diode array. FIG. 5 is a sectional view taken along line AA in FIG. 4; FIG. 6 is a plan view showing another conventional light emitting diode array. [Description of Signs] 1 substrate, 2 semiconductor layer of one conductivity type, 3 semiconductor layer of reverse conductivity type, 4 individual electrodes, 5 common electrode, 6 insulation Film, 7mm dummy wiring

Claims (1)

(57) [Claim 1] A plurality of island-like semiconductor layers in which a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are stacked are arranged in a row on a substrate, and In a light emitting diode array provided with a common electrode connected to the type semiconductor layer and connected with an individual electrode to the opposite conductivity type semiconductor layer, the light emitting diode array is formed from the same side in a direction intersecting the arrangement direction of the island-shaped semiconductor layers. Connected to the same individual electrode for each adjacent opposite conductivity type semiconductor layer and alternately drawn to the opposite end face side of the substrate, and the common electrodes are provided on both sides in a direction intersecting the arrangement direction of the island-shaped semiconductor layers. The common electrodes on both sides are alternately arranged for each one conductive type semiconductor layer below the opposite conductive type semiconductor layer connected to the same individual electrode from a side opposite to the direction intersecting the arrangement direction of the island-shaped semiconductor layers. And connect them to the individual electrodes. Light-emitting diode array, wherein a wiring for connecting to the electrode provided with dummy wirings to the island-like semiconductor layers which does not pass through.