KR100285537B1 - AlGaAs LED ARRAY AND METHOD FOR FABRICATING IT - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AlGaAs light emitting diode array and a method of manufacturing the same, and to replace a conventional diffusion type GaAsP light emitting diode array having limited light efficiency and light brightness for use as a light source for a display device of a miniaturized device, a portable electronic device A light source for a display device of which is formed of an AlGaAs light emitting diode array, and a structure for providing an integration degree such that the AlGaAs light emitting diode array can be mounted on a display device of a portable electronic device, that is, two columns of a plurality of unit pixels By providing an AlGaAs light emitting diode array having a structure arranged in this uneven shape and having a light emitting point formed in a protruding portion to achieve the unevenness, and a method of manufacturing the same, a light source suitable for portable electronic devices is provided.

Description

AlGaAs LED ARRAY AND METHOD FOR FABRICATING IT

The present invention relates to an AlGaAs light emitting diode array and a method of manufacturing the same, and more particularly, to an AlGaAs light emitting diode array having a degree of integration suitable for a light source for a display device of a portable electronic device and a method of manufacturing the same.

As is well known, display devices such as portable electronic devices such as cellular phones, pagers, and portable fax views are provided with light sources, and such light sources have low power consumption. In addition, a light emitting diode array (LED array: Light Emitting Diode array) has been used due to the advantages of small size and light weight.

The light emitting mechanism of the light emitting diode included in the light emitting diode array is formed by recombination of electrons in n-type and holes in p-type when a forward current flows through a pn junction. In order to facilitate the diffusion, a diffusion type GaAsP light emitting diode that forms a pn junction by diffusion has been mainly used.

Hereinafter, a manufacturing process of a diffusion type GaAsP LED array will be described with reference to FIG. 1.

First, referring to FIG. 1A, a GaAs substrate 10 is prepared.

Referring to FIG. 1B, GaAs _1-x P _x is grown on the upper surface of the GaAs substrate 10 by liquid phase epitaxy (LPE) to form a GaAsP balance layer 20. At this time, GaAs and GaP of the GaAsP light emitting layer 30 to be formed by the subsequent process has a large lattice constant difference, so that the GaAsP uniformity layer 20 is controlled by controlling the mole fraction x so as to alleviate the stress distribution due to lattice mismatch. It is formed by gradually changing its composition.

Referring to FIG. 1C, an n-type GaAsP light emitting layer 30 is formed by growing GaAs _0.6 P _0.4 on the upper surface of the GaAsP bacterial double layer 20 using the LPE method. At this time, the n-type GaAsP light emitting layer 30 functions as an n-type layer of pn junction.

Referring to FIG. 1D, an insulating layer 40 is formed by stacking an insulating material such as an oxide or nitride on the entire upper surface of the n-type GaAsP light emitting layer 30 and then insulating layer 40 by a conventional photolithography process. By patterning, portions of the n-type GaAsP light emitting layer 30 are exposed as shown in FIG. 1E.

Referring to FIG. 1F, impurities such as tellurium (Te) or zinc (Zn) are thinly diffused on the surface of the n-type GaAsP light emitting layer 30 exposed by the patterning of the insulating layer 40 to form the p-type diffusion region 50. By forming pn junctions.

Referring to FIG. 1G, an electrode 60 is formed by connecting metal wires to the p-type diffusion region 50 and the GaAs substrate 10.

As shown in the plan view of the GaAsP light emitting diode shown in FIG. 2, the diffusion type GaAsP light emitting diode made by the above-described process can easily make a plurality of minute light emitting points by diffusing a desired portion to form a light emitting point. have.

However, since the diffusion type GaAsP light emitting diode described above is difficult to control the diffusion depth of impurities in the formation of the diffusion region, it is difficult to control the brightness level of the light emitting point, and the brightness level of each light emitting point is uneven. there was.

In addition, in such a diffusion process, impurities are diffused not only in the vertical downward direction of the n-type GaAsP emission layer, but also in the horizontal direction of the n-type GaAsP emission layer, thereby increasing the contact resistance and lowering the luminous efficiency.

Further, there is a limit in converting the lattice mismatch between GaAs and GaP by the GaAsP balance layer 20, and there is a problem that the luminance level and the light efficiency are lowered even by such lattice mismatch.

On the other hand, in recent years, the miniaturization of portable electronic devices has been accelerated in order to increase the ease of portability. In response to the miniaturization of portable electronic devices, display devices mounted on the devices have also been miniaturized.

In order to reduce the size of the display device, a light source having a reduced overall size is required while maintaining the same or enhanced luminance level. Therefore, the conventional diffusion type GaAsP light emitting diode array has the above-mentioned problems, in particular, the problem of low light efficiency. There is a limit to the adoption in the display device of the portable electronic device, which is accelerating miniaturization.

Therefore, in order to miniaturize portable electronic devices, a highly efficient light source capable of solving the problems of the conventional diffusion type GaAsP light emitting diode array is required.

The present invention is to satisfy the above-described requirements, and since the lattice constants of GaAs and AlAs are almost the same in the AlGaAs light emitting diode array, lattice defects due to heterogeneous contact are hardly generated, and light is emitted in a region where the forbidden bandwidth Eg is small. Since light is emitted through a large crystal, it is possible to integrate such an AlGaAs light emitting diode array to a suitable level for a portable electronic device by focusing on the low absorption in the crystal and the improvement of the external quantum efficiency, resulting in high light efficiency and high brightness. An object of the present invention is to provide an AlGaAs light emitting diode array having a structure and a method of manufacturing the same.

In order to achieve the above object, in one aspect of the present invention, a plurality of units including a light emitting portion to form a pn junction by a p-type epi layer and an n-type epi layer, and an electrode for supplying a voltage to the light emitting portion An AlGaAs light emitting diode array comprising cells, each unit cell constituting the AlGaAs light emitting diode array; The AlGaAs light emitting diode array is formed in a rectangular shape having a protrusion formed with a light emitting point; The unit included in each of the two columns in such a manner that the light emitting points of the unit cells are arranged on the same line so that the light emitting points of the unit cells are arranged on the same line. Provided is an AlGaAs LED array, characterized in that the protrusions of the cells are arranged in a latch structure sandwiched between each of the grooves formed between neighboring unit cells of the other row.

On the other hand, in order to achieve the above object, in another aspect of the present invention, in the method of manufacturing an AlGaAs light emitting diode array, a p-type AlGaAs film and an n-type AlGaAs film are sequentially stacked on the entire upper surface of the GaAs substrate to form a pn junction. Forming; Patterning the n-type AlGaAs film and the p-type AlGaAs film in units of square pixels having protrusions, wherein the patterned pixels are arranged in two columns forming a cladding structure; And forming an electrode exposing a portion of the n-type AlGaAs film at the protruding portion on the n-type AlGaAs film of each of the patterned pixels.

1 is a sequential process diagram showing a manufacturing process of a diffusion type GaAsP light emitting diode array according to the prior art in a cross section of a unit cell;

2 is a plan view showing a diffusion type GaAsP light emitting diode array manufactured according to the prior art;

3A to 3J are sequential process diagrams showing, in plan view, a method of manufacturing an AlGaAs LED array according to a preferred embodiment of the present invention;

4A to 4J are sequential process diagrams showing a method of manufacturing an AlGaAs light emitting diode array according to a preferred embodiment of the present invention in cross-sections corresponding to each of FIGS. 3A to 3J;

5 is a mask pattern for patterning an AlGaAs light emitting diode cell by cell according to a preferred embodiment of the present invention;

6 is a mask pattern for forming a light emitting part and an electrode in an AlGaAs light emitting diode patterned on a cell basis according to a preferred embodiment of the present invention;

7 is a perspective view illustrating an AlGaAs light emitting diode array according to a preferred embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

10: GaAs substrate 20: GaAsP uniform layer

30 n-type GaAsP emitting layer 40 insulating layer

50 p-type diffusion region 60 electrode

110: GaAs substrate 120: p-type AlGaAs layer

130: n-type AlGaAs layer 140, 150 photosensitive film

160 electrode

Hereinafter, an AlGaAs LED array and a method of manufacturing the same according to the present invention will be described with reference to FIGS. 3 to 7. In this case, a 400-dpi class LED array having 128 light emitting points formed on an 8 mm die and a method of manufacturing the same will be described. For example, in FIGS. 3 to 7, it is distinguished from the diffusion type GaAsP LED array according to the prior art. The reference number is assigned to one hundred units (for example, 110, 120, ...).

Here, the core technical idea of the present invention is to form an AlGaAs light emitting diode array as a light source for a display device of a portable electronic device, and provide an integration degree such that the AlGaAs light emitting diode array can be mounted on a display device of a portable electronic device. In order to provide an AlGaAs array of light emitting diodes having a structure in which two rows of unit pixels are arranged in a concave-convex shape, and a light emitting point is formed in a protruding portion to form the concave-convex, and The focus will be on the same core technical ideas.

First, referring to FIG. 7, which is a perspective view of an AlGaAs light emitting diode array according to a preferred embodiment of the present invention, each of a plurality of (eg, 128) unit cells constituting an AlGaAs light emitting diode array according to the present embodiment Silver has a structure in which the p-type AlGaAs layer 120, the n-type AlGaAs layer 130, and the electrode 160 are sequentially stacked in an 'L' shape on the GaAs substrate 110, and the L-shaped In the protruding portion, a portion of the electrode 160 positioned at the top is removed to form a light emitting point at which the n-type AlGaAs layer 130 is exposed.

Some of the unit cells having such a structure and shape (for example, 64) are repeatedly arranged on the same line with the light emitting points located at the top to form a lower row, and the remaining unit cells are located at the bottom at the light emitting points. The upper row and the lower row are each unit included in each of the two rows (that is, the upper row and the lower row) so that the light emitting points may be disposed on the same line as illustrated in FIG. 7. Protruding portions of the cell are sandwiched between each of the grooves formed between neighboring unit cells of the other row (hereinafter, referred to as a "slancing structure") to form an AlGaAs LED array according to an embodiment of the present invention. At this time, both ends of the lower row or the upper row (for example, the lower row in the present embodiment with reference to FIG. 9), in which the same pattern cannot be repeated when forming the cladding structure, one end of the light emission to the protrusions The point is formed in the form of an 'iron (凸)' shape, the other end is made of a rectangular shape (□) formed with a light emitting point at the end.

As described above, in the present embodiment, 128 light emitting points can be formed in an 8 mm die by arranging L-shaped unit cells in two rows so as to form a cladding structure. By increasing the integration degree of the light emitting point, as in the L-shape, it is possible to provide a minimum electrode area that can be bonded to an external voltage source (not shown) for supplying voltage to the pn junction. In the above, the individual shape of the entire unit cell including the protruding range and protruding shape may be variously changed.

Hereinafter, a method of manufacturing an AlGaAs light emitting diode array having the above-described structure according to a preferred embodiment of the present invention will be described with reference to FIGS. 3 to 6.

3A to 3J are sequential process diagrams showing a method of manufacturing an AlGaAs LED array according to a preferred embodiment of the present invention in a plan view, and FIGS. 4A to 4J are steps of manufacturing an AlGaAs LED array according to a preferred embodiment of the present invention. 3A to 3J are sequential process diagrams showing cross sections corresponding to each of FIGS. 3A to 3J, FIG. 5 is a mask pattern for patterning AlGaAs light emitting diodes cell by cell, according to a preferred embodiment of the present invention, and FIG. According to a preferred embodiment, a mask pattern for forming a light emitting part and an electrode in an AlGaAs light emitting diode patterned on a cell basis.

3A and 4A, a GaAs substrate 110 is prepared.

Referring to FIGS. 3B and 4B, p-type Al _0.65 GaAs _0.35 is formed on a top surface of the GaAs substrate 110 prepared by liquid phase epitaxy (LPE), and has a predetermined thickness (for example, a thickness within 27 to 31 μm. ) To form a p-type AlGaAs layer (120).

Referring to FIGS. 3C and 4C, the n-type Al _0.65 GaAs _0.35 is formed on the upper front surface of the p-type AlGaAs layer 120 by a liquid phase epitaxy (LPE), and has a predetermined thickness (eg, 43 to 47 μm). Thickness) to form an n-type AlGaAs layer 130. As a result, a pn junction in which light is emitted by electron-hole recombination is formed between the p-type AlGaAs layer 120 and the n-type AlGaAs layer 130. The p-type AlGaAs layer 130 is a p-type AlGaAs layer ( Since the pn junction is uniformly formed over the entire area of the upper front surface of the substrate 120, each of the light emitting points may have the same luminance level when separated into a plurality of light emitting points by a subsequent process.

Referring to FIG. 3D and FIG. 4D, a photoresist (PR) is applied to the upper surface of the n-type AlGaAs layer 130 by a spin coating method to form a photosensitive film 140.

Referring to FIGS. 3E and 4E, after the mask pattern as illustrated in FIG. 5 is transferred to the photosensitive layer 140 by photolithography, the remaining photosensitive layer 140 except for the transferred pattern shape is transferred. Remove The photosensitive film 140 thus patterned has the same shape as that of the array of AlGaAs light emitting diode arrays to be formed according to the present embodiment, so that the p-type AlGaAs layer 120 and the n-type AlGaAs layer 130 in a subsequent process. Is used as a mask for patterning the pn junction formed by the?) Into a shape according to the present embodiment.

3F and 4F, the n-type AlGaAs layer 130 and the p-type AlGaAs layer 120 which are exposed through the pattern of the photosensitive film 140 by the etching method are sequentially removed, whereby the pn junction is applied to the present embodiment. Patterned in the shape of the unit cell according to. That is, each unit cell forms an 'L' shape according to the present embodiment, and two rows repeatedly arranged in the same shape of the L shape form a latch structure. After the p-n junction is patterned as such, the photoresist 140 used as a mask for patterning the p-n junction is removed by a conventional PR stripping technique.

Referring to FIGS. 3G and 4G, the photoresist PR is applied to the entire upper surface of the structure formed by the above-described process by the rotation coating method to form the photoresist film 150.

3H and 4H, after the mask pattern as shown in FIG. 6 is transferred to the photosensitive film 150 by photolithography, the remaining photosensitive film 150 except for the transferred pattern shape is transferred. Remove The patterned photosensitive film 150 has the same shape as that of the electrode array of the AlGaAs light emitting diode array to be formed according to the present embodiment, but the light emitting point is formed on the protruding portion of each unit cell. It is used as a mask for forming the electrode 160 in the lift-off process in the process.

Referring to FIGS. 3I and 4I, a metal having good conductivity (eg, gold) is formed on the upper portion of the photoresist film 150 and the upper portion of the n-type AlGaAs layer 130 exposed by the patterning of the photoresist film 150 by sputtering or the like. (Au)) and the like.

3J and 4J, the photoresist film 150 is removed using conventional PR stripping techniques. As a result, the metal stacked on the photoresist film 150 is also removed, and only the metal formed on the n-type AlGaAs layer 130 exposed by the patterning of the photoresist film 150 remains to become the electrode 160. In this case, since the photoresist film 150 is stacked on the protrusions of the unit cells of the AlGaAs LED array to form the light emitting point, the photosensitive film 150 is removed and the photosensitive film 150 is stacked on the protruding portion of the unit cells. The metal is also removed, and the light emitting point is formed by exposing the n-type AlGaAs layer 130 through the pattern of the electrode 160 at the light emitting point portion. Subsequently, when power is supplied to the electrode 160, light is emitted at a pn junction that is a junction portion of the p-type AlGaAs layer 120 and the n-type AlGaAs layer 130 through the light emitting points thus formed, and the emitted light. Is irradiated to the outside through the above-mentioned light emitting point.

Meanwhile, in the present embodiment, the electrode 160 is formed by a lift-off technique through the same process as in FIGS. 3G to 3J and FIGS. 3G to 3J. The reason for forming the technique is to form an upper portion of the flat GaAs substrate 110. Unlike the p-type AlGaAs layer 120 and the n-type AlGaAs layer 130, which are uniformly formed and then sequentially patterned on the electrode 160, the electrode 160 is already formed on the n-type AlGaAs layer 130 patterned with high density. Since the pattern formation of the electrode 160 is required to be more accurate than the AlGaAs layer 120 or the n-type AlGaAs layer 130, it is to improve the accuracy by reducing an error occurrence factor such as an alignment or an etching process. Therefore, the electrode 160 having the structure according to the present embodiment can be easily formed using not only the lift-off technique but also conventional lamination and photolithography techniques.

According to the present invention described above, by manufacturing an AlGaAs light emitting diode array of high efficiency and high brightness as compared to the conventional diffused GaAsP light emitting diode array, the same diffusion type GaAsP light emitting diode at low power Since the luminance and efficiency beyond the array can be obtained, it is possible to provide a light source suitable for a display device of a portable electronic device.

Claims (5)

In an AlGaAs light emitting diode array comprising a plurality of unit cells including a light emitting portion that is a p-n junction by a p-type epi layer and an n-type epi layer, and an electrode for supplying a voltage to the light emitting portion, Each of the unit cells constituting the AlGaAs LED array is; It consists of a rectangular shape having a protrusion formed with a light emitting point, The AlGaAs light emitting diode array; The unit included in each of the two columns in such a manner that the light emitting points of the unit cells are arranged on the same line so that the light emitting points of the unit cells are arranged on the same line. An AlGaAs LED array, characterized in that the protrusions of the cells are arranged in a latch structure sandwiched between each of the grooves formed between neighboring unit cells of the other row. The method of claim 1, wherein each of the unit cells, An AlGaAs light emitting diode array comprising an 'L' shape. In the method of manufacturing an AlGaAs light emitting diode array, Sequentially forming a p-type AlGaAs film and an n-type AlGaAs film on the entire upper surface of the GaAs substrate to form a p-n junction; Patterning the n-type AlGaAs film and the p-type AlGaAs film in units of square pixels having protrusions, wherein the patterned pixels are arranged in two columns forming a cladding structure; And forming an electrode exposing a part of the n-type AlGaAs film at the protruding portion on the n-type AlGaAs film of each of the patterned pixels. The method of claim 3, wherein the n-type AlGaAs film and the p-type AlGaAs film are patterned in units of L-shaped pixels. The method of claim 3 or 4, wherein the electrode is formed by a lift-off technique.