KR101154706B1 - Light emitting diode - Google Patents

Abstract

The present invention discloses a light emitting diode capable of improving light efficiency by inserting a high refractive index layer having a high refractive index and a low energy band gap between a P-type reflective electrode and a P-type semiconductor layer of the light emitting diode. The disclosed invention includes a first nitride semiconductor layer; An active layer formed on the first nitride semiconductor layer; A second nitride semiconductor layer formed on the active layer; A high refractive layer formed on the second nitride semiconductor layer; And a reflective electrode and an electrode formed on the high refractive layer.

The first nitride semiconductor layer may include a buffer layer made of a nitride material, an undoped nitride semiconductor layer, and an N-type doped nitride semiconductor layer, and the high refractive layer may be formed of phosphorus (P) or arsenic ( As) component, the high refractive index layer is characterized in that the refractive index is larger than the refractive index of the second nitride semiconductor layer.

LED, refractive, total reflection, light efficiency, reflective electrode

Description

[0001] LIGHT EMITTING DIODE [0002]

1 is a view illustrating flip chip bonding of a light emitting diode according to the related art.

2 is a view illustrating a flip chip bonding of a light emitting diode according to the present invention;

3 is a view according to another embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100: light emitting diode 101: sapphire substrate

103: N-type gallium nitride layer 105: active layer

106: P-type gallium nitride layer 108: P-type reflective electrode

120: high refractive layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode. More specifically, a light emitting diode having a high refractive index having a high refractive index and a low energy band gap is inserted between a P-type reflective electrode and a P-type semiconductor layer of the light emitting diode, thereby improving light efficiency. It is about.

In general, a light emitting diode (LED) is a type of semiconductor used to send and receive signals by converting electricity into infrared rays or light using characteristics of a compound semiconductor. It is used for various automation equipment.

The operation principle of the LED is that when a forward voltage is applied to a semiconductor of a specific element, electrons and holes move and recombine with each other through a junction portion of a positive-negative and a positive-negative, and energy levels are caused by the combination of electrons and holes. Will fall and this energy level is emitted as light.

In addition, LEDs are generally manufactured in small sizes and have structures mounted on epoxy molds, lead frames, and PCBs. Currently, the most commonly used LEDs are 5mm (T 1 3/4) plastic packages or new types of packages depending on the specific application. The wavelength of light emitted by an LED depends on the composition of the semiconductor chip components, which determine the color of the light.

In particular, LEDs are becoming smaller and smaller, such as resistors, capacitors, and noise filters, due to the trend toward miniaturization and slimming of information and communication devices, and directly mounting them on a PCB (Printed Circuit Board) board. In order to make the surface mount device (Surface Mount Device) type.

Accordingly, LED lamps, which are used as display elements, are also being developed in SMD type. Such SMD can replace the existing simple lighting lamp, which is used for lighting indicators of various colors, character display and image display.                         

In recent years, as high-density integration technologies for semiconductor devices have been developed and consumers have demanded more compact electronic products, surface mount technology (SMT) has been widely used, and packaging technologies for semiconductor devices have also been known as ball grid array (BGA) and wire bonding. Technology to minimize the installation space, such as flip chip bonding.

1 is a view illustrating flip chip bonding of a light emitting diode according to the prior art.

As shown in Fig. 1, the structure of the light emitting diode 1 is as follows.

N-type gallium nitride composed of a GaN buffer layer, an undoped GaN layer, and an N-type GaN layer on a sapphire substrate 1 composed of Al ₂ O ₃ series Form layer 3.

As described above, in order to grow a thin film of a group III-based element on the sapphire substrate 1, metal organic chemical vapor deposition (MOCVD) is generally used, and the growth pressure is 200 torr (torr). Form a layer while maintaining 650 torr.

As the N-type GaN layer, silicon using silicon tetrahydride (Si: H4) or silicon dihydrogen (Si2H6) gas is used.

When the N-type gallium nitride layer 3 is grown, an active layer 5 is grown on the N-type gallium nitride layer 3. The active layer 5 is a semiconductor layer to which a light emitting material made of indium gallium nitride (InGaN) is added as a light emitting region. As the active layer 5 is grown, a P-type gallium nitride layer 6 is formed. The P-type gallium nitride layer 6 is made of P-AlGaN (Mg) or P-InGaN component.

The P-type gallium nitride layer 6 is a layer contrasted with the N-type gallium nitride layer 3, and the N-type gallium nitride layer 3 transfers electrons to the active layer 5 by a voltage applied from the outside. Supply.

Relatively, the P-type gallium nitride layer 6 supplies holes to the active layer 5 by a voltage applied to the outside, whereby holes and electrons in the active layer 5 couple to each other. Generate light.

The P-type electrode to be subsequently formed on the P-type gallium nitride layer 6 forms a transparent layer made of a transparent metal when wire-bonding the light emitting diode 10, and then a P-type electrode electrically bonded to the wire. To form. Similarly, the N-type electrode is opened to the N-type gallium nitride layer 3, and then an N-type electrode is formed on the N-type gallium nitride layer 3.

However, since the sapphire substrate 1 is a substrate that can transmit light, the edge region is etched after the p-type gallium nitride layer 6 is formed in flip chip bonding in which the light emitting diode 10 is inverted and bonded. The N-type gallium nitride layer 3 can be opened.

Then, a metal having high reflectance is formed on the P-type gallium nitride layer 6 to form a P-type reflective electrode 8 serving as a P-type electrode and a reflecting plate. In the case of the N-type electrode, since there is no active layer 5 for generating light, the electrode is formed using a general metal.

When the light emitting diode 10 is completed as described above, the light emitting diode 10 is mounted on the printed circuit board 11. Since the light emitting diode 10 is flip-chip bonded, the printed circuit board of the region in which the light emitting diode 10 is mounted ( The reflective layer 12 is formed on 11).

The light emitting diode 10 is mounted on the printed circuit board 11 in the form of a flip chip, and an under bumper metal (UBM) 15 is emitted to an area to be mounted on the printed circuit board 11. It is formed on the diode 10 and the printed circuit board 11, and then electrically bonded with a solder (16) in between.

In the flip chip bonded light emitting diode 10 having the above structure, when power is applied to the light emitting diode 10 through the printed circuit board 11, electrons and holes are combined in the active layer 5 to generate light. .

As described above, part of the light generated in the active layer 5 is emitted to the outside through the sapphire substrate 1, and part of the light is the P-type gallium nitride layer 6, the P-type reflective electrode 8, and the printing. The light is reflected by the reflective layer 12 formed on the circuit board 11 and then emitted to the outside.

In particular, when the light emitting diode 10 is flip-chip bonded, since the light generated in the active layer 5 is directly or reflected and then emitted to the outside through the sapphire substrate 1, the light emitting diode 10 may be mounted compared to the light emitting diode mounted by wire bonding. There is an advantage that the light efficiency is increased.

In addition, in the case of a light emitting diode mounted by wire bonding, since the P-type electrode and the N-type electrode are formed of an opaque metal in the region bonded by the wire, there is a problem that the light efficiency is lowered. There is no such factor of deterioration.

However, a light emitting diode manufactured for flip chip bonding as described above has a problem in that 50% of light reflected from a reflective layer formed on a P-type reflective electrode and a printed circuit board is degraded by a P-type gallium nitride layer having a low refractive index. .

When the refractive index of the P-type gallium nitride layer is 2.5 or more, most of the light generated in the active layer is reflected by the P-type reflective electrode or the reflective layer, and the P-type gallium nitride layer has a refractive index of about 2, which reduces the light efficiency. Cause.

The present invention provides a light reflection efficiency by inserting a high refractive index layer having a similar p-type gallium nitride layer and a lattice combination between a p-type reflective electrode and a p-type gallium nitride layer of a light emitting diode for flip chip bonding, and having a low band gap energy. The purpose is to provide a light emitting diode with improved.

In order to achieve the above object, a light emitting diode according to the present invention,

A first nitride semiconductor layer;

An active layer formed on the first nitride semiconductor layer;

A second nitride semiconductor layer formed on the active layer;

A refractive layer formed on the second nitride semiconductor layer and having a refractive index greater than that of the second nitride semiconductor layer; And

It characterized in that it comprises a reflective electrode formed on the refractive layer.

The first nitride semiconductor layer may include a buffer layer made of a nitride material, an undoped nitride semiconductor layer, and an N-type doped nitride semiconductor layer, and the high refractive layer may be formed of phosphorus (P) or arsenic ( As) component, the high refractive index layer is characterized in that the refractive index is larger than the refractive index of the second nitride semiconductor layer.

The refractive index of the high refractive index layer is in the range of 2.5 to 3, the energy band gap of the high refractive layer has a lower value than the energy band gap of the second nitride semiconductor layer, the electrode is light generated in the active layer It serves as a reflector for reflecting the electrode and supplying power, characterized in that it further comprises a third nitride semiconductor layer between the second nitride semiconductor layer and the high refractive layer.

In addition, the third nitride semiconductor layer is characterized in that the nitride semiconductor layer doped with a high concentration of N-type.

According to the present invention, a light reflection is inserted between a P-type gallium nitride layer and a lattice combination between the P-type reflective electrode and the P-type gallium nitride layer of a light emitting diode for flip chip bonding by inserting a high refractive layer with low band gap energy. There is an effect of improving the efficiency.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view illustrating flip chip bonding of a light emitting diode according to the present invention.                     

As shown in FIG. 2, the light emitting diode 100 has a GaN buffer layer made of gallium nitride (GaN) on an sapphire substrate 100 composed of Al ₂ O ₃ series components, and is not doped. An N-type gallium nitride layer 103 composed of an (undoped) GaN layer and an N-type GaN layer is formed.

As described above, in order to grow a thin film of the Group 3 series element on the sapphire substrate 101, a metal organic chemical vapor deposition (MOCVD) is generally used, and the growth pressure is 200 torr (torr). Form a layer while maintaining 650 torr.

As the N-type GaN layer, silicon using silicon tetrahydride (Si: H4) or silicon dihydrogen (Si2H6) gas is used.

When the N-type gallium nitride layer 103 is grown, an active layer 105 is grown on the N-type gallium nitride layer 103. The active layer 105 is a semiconductor layer to which a light emitting material made of indium gallium nitride (InGaN) is added as a light emitting region.

As the active layer 105 grows, a P-type gallium nitride layer 106 is formed. The P-type gallium nitride layer 106 is made of P-AlGaN (Mg) or P-InGaN component.

The P-type gallium nitride layer 106 is a layer contrasted with the N-type gallium nitride layer 103, and the N-type gallium nitride layer 103 transmits electrons to the active layer 105 by a voltage applied from the outside. Supply.

In addition, the P-type gallium nitride layer 106 supplies holes to the active layer 105 by a voltage applied to the outside, so that holes and electrons are coupled to each other in the active layer 105. To generate light.

When the P-type gallium nitride layer 106 is formed, a high refractive index layer 120 having a refractive index of 2.5 or more is formed by inserting a phosphorus (P) or arsenic (As) component into the chamber forming the P-type gallium nitride layer 106. .

Therefore, the high refractive index layer 120 includes a P component or an As component in the gallium nitride-based material to have a refractive index of 2.5 or more and 3 or less.

When the high refractive layer 120 is formed on the P-type gallium nitride layer 106 as described above, the edge region is etched to open the N-type gallium nitride layer 103.

Then, a reflective electrode 108 is formed on the high refractive index layer 120 using a metal having a high reflectance to serve as an electrode and a reflecting plate electrically connected to the P-type gallium nitride layer 106. In the case of the N-type electrode, since there is no active layer 105 that generates light, an electrode is formed on the N-type gallium nitride layer 103 using a general metal.

As such, when the light emitting diode 100 is completed, the light emitting diode 100 is mounted on the printed circuit board 111. Since the light emitting diode 100 is flip chip bonded, the printed circuit board in the region where the light emitting diode 100 is mounted is mounted. The reflective layer 112 is formed on the (111).

The light emitting diode 100 is mounted on the printed circuit board 111 in the form of a flip chip, and an under bumper metal (UBM, 115) is emitted to an area to be mounted on the printed circuit board 111. It is formed on the diode 100 and the printed circuit board 111, and then electrically bonded to the printed circuit board 111 with a solder (116) in between.

In the flip chip bonded light emitting diode 100 having the above structure, when power is applied to the light emitting diode 100 through the printed circuit board 111, electrons and holes are combined in the active layer 105 to generate light. .

As described above, part of the light generated by the active layer 105 is emitted to the outside through the sapphire substrate 101, and part of the light is the P-type gallium nitride layer 106, the high refractive layer 120, and the reflective electrode 108. Reflections).

Light reflection also occurs through the reflective layer 112 formed on the printed circuit board 111.

In the present invention, since the high refractive layer 120 is interposed between the P-type gallium nitride layer 106 and the reflective electrode 108, the light traveling through the P-type gallium nitride layer 106 passes through the high refractive layer 120. Most of the light reflected and transmitted by the light reflected by the reflective electrode 108 is reflected in the high refractive index layer 120 to improve the reflection efficiency.

In addition, when power is applied through the reflective electrode 108, a uniform carrier is injected through the high refractive layer 120 having a lower energy band gap and similar crystal structure than the P-type gallium nitride layer 106. The luminous efficiency of the active layer 105 can be improved.

3 is a diagram according to another embodiment of the present invention, as shown in FIG. 2, but having a structure similar to that of FIG. The doped gallium nitride layer 170 was inserted.

Accordingly, the light emitting diode 100 includes the sapphire substrate 101, the N-type gallium nitride layer 103, the active layer 105, the P-type gallium nitride layer 106, the doped gallium nitride layer 170, and the high refractive layer 120. ), And a reflective electrode 108.

Hereinafter, a description will be given focusing on a part different from the above-described FIG. 2.

In the light emitting diode of the present invention, an N-type high concentration doped gallium nitride layer 170 is formed between the P-type gallium nitride layer 106 and the reflective electrode 108. The doped gallium nitride layer 170 The thickness is thin in Å unit.

Here, when power is applied to the reflective electrode 108, a super grading effect occurs between the P-type gallium nitride layer and the doped gallium nitride layer, and holes pass through the doped gallium nitride layer 170. Thus, holes are introduced into the P-type gallium nitride layer 106.

Holes flowing from the P-type gallium nitride layer 106 and electrons flowing from the N-type gallium nitride layer 103 are combined in the active layer 105 to generate light.

As such, the light generated in the active layer 105 is mostly reflected by the high refractive layer 120 and the remaining light is reflected by the reflective electrode 108. In the high refractive index layer 120 having a refractive index of 2.5 or more and precisely 2.5 or more and 3 or less, the transmittance was increased to improve light efficiency.

In addition, when power is applied through the reflective electrode 108, a uniform carrier is injected through the high refractive layer 120 having a lower energy band gap and similar crystal structure than the P-type gallium nitride layer 106. The luminous efficiency of the active layer 105 can be improved.

As described in detail above, the present invention inserts a high refractive index layer having a similar lattice combination and a low band gap energy between the reflective electrode and the p-type gallium nitride layer of the light emitting diode for flip chip bonding. Thereby, there exists an effect which improved light reflection efficiency.

The present invention is not limited to the above-described embodiments, and various changes can be made by those skilled in the art without departing from the gist of the present invention as claimed in the following claims.

Claims (9)

An active layer formed on the first nitride semiconductor layer; A second nitride semiconductor layer formed on the active layer; A third nitride semiconductor layer on the second nitride semiconductor layer; A refractive layer formed on the third nitride semiconductor layer and having a refractive index greater than that of the second nitride semiconductor layer; And A reflection electrode and a pad formed on the refractive layer; The third nitride semiconductor layer is a light emitting diode, characterized in that when the power is applied to the reflective electrode, holes are introduced into the second nitride semiconductor layer through the third nitride semiconductor layer. The method of claim 1, And the first nitride semiconductor layer comprises a buffer layer of a nitride material, an undoped nitride semiconductor layer, and an N-type doped nitride semiconductor layer. The method of claim 1, The refractive layer is a light emitting diode, characterized in that the phosphorus (P) or arsenic (As) component is included in the gallium nitride-based material. delete The method of claim 1, The refractive index of the refractive layer is a light emitting diode, characterized in that it has a range value of 2.5 ~ 3. The method of claim 1, The energy band gap of the refractive layer has a lower value than the energy band gap of the second nitride semiconductor layer. The method of claim 1, The reflective electrode is a light emitting diode, characterized in that serves as a reflector for reflecting the light generated in the active layer and the electrode for supplying power. delete delete

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