KR102817111B1 - Semiconductor lighting source for display and method of manufacturing the same - Google Patents

Abstract

A semiconductor light source for a display and a method for manufacturing the same are disclosed.
A semiconductor light source according to the present invention comprises: a first conductive semiconductor layer; an active layer formed on the first conductive semiconductor layer; and a second conductive semiconductor layer formed on the active layer, wherein the active layer comprises a first active layer in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated, and a second active layer in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated, wherein the first active layer is formed in a superlattice structure, the second active layer is formed in a multi-well structure, and a threading potential is formed penetrating the first conductive semiconductor layer and the first active layer, and a wedge-shaped groove is formed on an upper end of the first active layer intersecting with the threading potential.

Description

{SEMICONDUCTOR LIGHTING SOURCE FOR DISPLAY AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a technology for manufacturing a semiconductor light source for a display, and more specifically, to a semiconductor light source for a display capable of exhibiting high efficiency characteristics through defect control and a method for manufacturing the same.

A semiconductor light source is a semiconductor device that converts electrical energy into light energy, and the semiconductor light source contains a material that can generate light. Among the materials that can generate the light in the semiconductor light source, nitride semiconductors, represented by GaN, are widely known, and the energy generated when electrons and holes recombine is converted into light and emitted to the outside.

Semiconductor light sources have advantages such as long life, low power consumption, fast response speed, and environmental friendliness compared to conventional light sources such as fluorescent lamps, and therefore are widely used as light sources for lighting and displays.

To improve the luminous efficiency of semiconductor light sources, various studies are being conducted. For example, many studies are being conducted to form wedge-shaped grooves in the active layer.

It is known that when the active layer of a semiconductor light source is formed in a wedge-shaped groove structure, the light extraction efficiency can be improved by increasing the area of the active layer.

Patent Document 1 discloses a method for manufacturing a nitride semiconductor light source. According to Patent Document 1, a wedge-shaped groove is formed on the upper surface of an n-type nitride semiconductor layer, and the method suggests lowering the growth temperature of the n-type nitride semiconductor layer to 700 to 1000°C or forming the n-type nitride semiconductor layer at a temperature of 1000°C or higher, and then performing chemical etching.

However, if the growth temperature of the n-type nitride semiconductor layer is lowered below 1000℃, various problems that adversely affect the luminescence efficiency or life characteristics, such as insufficient doping and deterioration of crystal quality, may occur. In addition, if chemical etching is performed while the n-type nitride semiconductor layer is formed, there is a problem of reduced productivity because it entails an interruption of the MOCVD process.

Publication of Patent Publication No. 10-2010-0093872 (Published on August 26, 2010)

The problem to be solved by the present invention is to provide a semiconductor light source for a display having excellent light emission efficiency by forming a wedge-shaped groove structure in an active layer, and a method for manufacturing the same.

In particular, the problem to be solved by the present invention is to provide a semiconductor light source for a display and a method for manufacturing the same, which can maintain a nitride semiconductor layer growth temperature at a sufficiently high temperature and form a wedge-shaped groove structure in an active layer without interrupting the MOCVD process.

According to an embodiment of the present invention for achieving the above object, a semiconductor light source includes: a first conductive semiconductor layer; an active layer formed on the first conductive semiconductor layer; and a second conductive semiconductor layer formed on the active layer, wherein the active layer includes a first active layer in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated, and a second active layer in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated, wherein the first active layer is formed in a superlattice structure, the second active layer is formed in a multi-well structure, and a threading dislocation is formed penetrating the first conductive semiconductor layer and the first active layer, and a wedge-shaped groove is formed on an upper end of the first active layer intersecting with the threading dislocation.

The second active layer is formed to cover the upper surface of the first active layer including the inclined surface of the wedge-shaped groove, so that the wedge-shaped groove can extend to the second active layer.

An undoped semiconductor layer may be additionally formed under the first challenge type semiconductor layer.

The first active layer may be formed with a structure in which InGaN layers and GaN layers, each having a thickness of 10 nm or less, are alternately laminated two or more times, and the second active layer may be formed with a structure in which InGaN quantum well layers and GaN quantum barrier layers are alternately laminated two or more times.

The above-mentioned threading potential can be terminated in the second active layer.

The concentration of indium in the semiconductor layer including indium of the first active layer may be lower than the concentration of indium in the semiconductor layer including indium of the second active layer.

According to an embodiment of the present invention for solving the above problem, a method for manufacturing a semiconductor light source includes: a step of forming a first conductive semiconductor layer on a substrate; a step of forming a first active layer having a superlattice structure in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated on the first conductive semiconductor layer, wherein a wedge-shaped groove is formed on an upper portion of the first active layer; a step of forming a second active layer having a multi-well structure in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated on the first active layer while maintaining the wedge-shaped groove; and a step of forming a second conductive semiconductor layer on the second active layer, wherein a threading potential is formed by penetrating the first conductive semiconductor layer and the first active layer, and a wedge-shaped groove is formed on an upper portion of the first active layer intersecting with the threading potential.

The above-mentioned threading potential can be terminated in the second active layer.

The concentration of indium in the semiconductor layer including indium of the first active layer may be lower than the concentration of indium in the semiconductor layer including indium of the second active layer.

The semiconductor light source for a display according to the present invention can maintain the nitride semiconductor layer growth temperature at a sufficiently high temperature, thereby suppressing problems such as insufficient doping and deterioration of crystal quality, and also has the effect of preventing a decrease in productivity by forming a wedge-shaped groove structure in the active layer without interrupting the MOCVD process.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the detailed description below.

Figure 1 schematically illustrates an example of a typical semiconductor light source for a display.
Figure 2 schematically illustrates a semiconductor light source for a display according to an embodiment of the present invention.
Figure 3 is an enlarged view of part A of Figure 2.
Figure 4 shows the surface and cross-section of the active layer of a semiconductor light source according to the present invention.

The advantages and features of the present invention, and the methods for achieving them, will become clear with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and these embodiments are provided only to make the disclosure of the present invention complete and to fully inform a person having ordinary skill in the art to which the present invention belongs of the scope of the invention, and the present invention is defined only by the scope of the claims.

When an element or layer is referred to as being "above" or "below" another element or layer, it includes not only directly above or below the other element or layer, but also intervening elements or layers. Additionally, when an element is described as being "connected," "coupled," or "connected" to another element, it should be understood that the elements may be directly connected or connected to one another, but that other elements may also be "interposed" between the elements, or that the elements may be "connected," "coupled," or "connected" through the other elements.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the present invention. In this specification, the singular also includes the plural unless the context clearly dictates otherwise. The terms "comprises" and/or "comprising" as used herein do not exclude the presence or addition of one or more other elements, components, steps and/or operations.

Hereinafter, a semiconductor light source for a display and a manufacturing method thereof according to the present invention will be described in detail with reference to the attached drawings.

Figure 1 schematically illustrates an example of a typical semiconductor light source for a display.

Referring to FIG. 1, the illustrated semiconductor light source has a structure in which an active layer (120) having a multi-quantum well (MQW) structure is formed between a first conductive semiconductor layer (110) and a second conductive semiconductor layer (130).

The first conductive semiconductor layer (110) is formed of an n-type nitride semiconductor doped with an n-type impurity, such as silicon (Si), as in the n-GaN illustrated in FIG. 1. And, the second conductive semiconductor layer (130) is formed of a p-type nitride semiconductor doped with a p-type impurity, such as magnesium (Mg), as in the p-GaN illustrated in FIG. 1.

Each of the nitride semiconductor layers (110, 120, 130) is formed by epitaxial growth on a substrate (101), such as a sapphire substrate. In addition, in order to improve the crystal quality of each of the nitride semiconductor layers (110, 120, 130), each of the nitride semiconductor layers (110, 120, 130) is generally formed after an undoped nitride semiconductor layer (105) or a buffer layer is formed on the substrate (101).

In the case of the active layer (120), a high electron-hole recombination rate is required. However, according to the nitride semiconductor light-emitting device structure illustrated in Fig. 1, there was a disadvantage in that the well layer and barrier layer were thick, reducing the carrier injection efficiency.

FIG. 2 schematically illustrates a semiconductor light source for a display according to an embodiment of the present invention, and FIG. 3 is an enlarged view of part A of FIG. 2.

Referring to FIGS. 2 and 3, a semiconductor light source for a display according to the present invention includes a first conductive semiconductor layer (210), a first active layer (220), a second active layer (230), and a second conductive semiconductor layer (240).

Each of the semiconductor layers described above can be formed on the substrate (201) by a known epitaxial growth method such as MOCVD (metal organic chemical vapor deposition) or MBE (Molecular Beam Epitaxy). As precursors for forming the semiconductor layers, TMGa (Trimethylgallium), TMIn (Trimethylindium), and ammonia (NH ₃ ) can be used. In addition, when forming each nitride semiconductor layer, a process temperature of about 900 to 1300° C. and a pressure condition of about 50 to 200 100 mbar can be applied, but are not limited thereto.

The substrate (201) may be a substrate made of a known material such as sapphire, SiC, Si, or GaN. In addition, a hemispherical pattern, etc. may be formed on the surface of the substrate (201) (for example, a patterned sapphire substrate (PSS). In addition, an undoped semiconductor layer (205) or a buffer layer, etc. may be further formed on the substrate (201) to improve the crystal quality of the nitride semiconductor.

The first conductive semiconductor layer (210) may be formed of an n-type nitride semiconductor doped with an n-type impurity, such as silicon (Si), such as n-GaN. In addition, the second conductive semiconductor layer (240) may be formed of a p-type nitride semiconductor doped with a p-type impurity, such as magnesium (Mg), such as p-GaN. In this case, carriers injected from the first conductive semiconductor layer (210) become electrons, and carriers injected from the second conductive semiconductor layer (240) become holes. It may also be considered that the first conductive semiconductor layer (210) is formed of a p-type nitride semiconductor, and the second conductive semiconductor layer (240) is formed of an n-type nitride semiconductor.

In the present invention, the active layer includes a first active layer (220) and a second active layer (230).

The first active layer (220) is formed on the first conductive semiconductor layer (210). The second active layer (230) is formed on the first active layer (220).

The first active layer (220) and the second active layer (230) may each have a structure in which semiconductor layers containing indium (e.g., an InGaN layer) and semiconductor layers not containing indium (e.g., a GaN layer) are alternately laminated. At this time, the first active layer (220) may be formed in a superlattice structure, and the second active layer (220) may be formed in a multi-quantum well (MQW) structure in which quantum well layers, which are semiconductor layers containing indium, and quantum barrier layers, which are semiconductor layers not containing indium, are alternately formed.

Here, the first active layer of the superlattice structure is a nitride semiconductor layer in which a semiconductor layer (221) containing indium, such as InGaN/GaN, and a semiconductor layer (222) not containing indium are alternately laminated, and each layer has a thickness of 10 nm or less, more preferably 8 nm or less, and even more preferably 6 nm or less. For example, the first active layer (220) may be formed in a structure in which an InGaN layer and a GaN layer, each having a thickness of 10 nm or less, are alternately laminated two or more times to have a superlattice structure.

In the present invention, the first active layer (220) has a form including a wedge-shaped groove (225) at the top. When the first active layer (220) of the superlattice structure is formed at about 850 to 950°C, growth occurs on a different plane (for example, the (1,1-,0,1) plane) at a temperature that is relatively lower than the growth temperature of the first conductive semiconductor layer, and in particular, since the binding energy at the peak of the threading dislocation is different, a wedge-shaped groove (225) can be created at this peak.

A treading dislocation (250) is formed by passing through the first conductive semiconductor layer (210) and the first active layer (220), and a wedge-shaped groove (225) is formed at the top of the first active layer (220) intersecting with the treading dislocation (250). As the wedge-shaped groove (225) is formed at the top of the first active layer (220), the treading dislocation (250) may be terminated at the bottom or inside of the second active layer (230), for example.

It is known that defects occurring in nitride semiconductor epitaxial growth are generally associated with a deterioration in luminescence characteristics. When a large number of crystal defects, such as pits, are generated on the surface of a multiple quantum-well structure and a second-conductivity semiconductor layer, such as a p-GaN layer, is formed on top of the crystal defects, the pits themselves become passages for the crystal defects as the crystal defects are transferred to the second-conductivity semiconductor layer. In addition, as Mg atoms are transferred to the luminescent layer through internal diffusion, a decrease in luminescence efficiency occurs, and the semiconductor light source itself may be destroyed due to excessive leakage current when the semiconductor light source is operated by current injection. However, the wedge-shaped groove does not function as a defect, but rather can be effectively utilized to improve luminous efficiency and can contribute to the termination of threading dislocations.

In the case of a threading dislocation generated and raised from the lower nitride semiconductor layers (undoped semiconductor layer, first conductive semiconductor layer), a wedge-shaped groove is formed in the first active layer (220) of the superlattice structure. Thereafter, the wedge-shaped groove structure is maintained in the second active layer (230) through nitride growth, and a relatively high-resistance layer is formed on the side of the wedge-shaped groove to form a high energy barrier. Since this high energy barrier layer has a relatively low growth rate on the inclined plane, the emitting layer is not formed well, and thus electrons in the emitting layer cannot escape through the threading dislocation due to the high band gap and are combined inside the emitting layer, so that high efficiency can be realized.

The second active layer (230) formed on the first active layer (220) is formed in a form that maintains the upper shape of the first active layer (220) including the wedge-shaped groove. That is, when the second active layer (230) is formed, deposition is also performed on the slope of the wedge-shaped groove, so that the wedge-shaped groove is maintained. This is achieved by substantially increasing the area of the second active layer (230), and as a result, it can bring about the effects of increasing the light-emitting area and improving the efficiency of carrier injection into the active layer.

The second active layer (230) can be formed with a structure in which an InGaN quantum well layer and a GaN quantum barrier layer are alternately laminated two or more times.

Meanwhile, it is preferable that the concentration of indium in the semiconductor layer including indium of the first active layer (220) is lower than the concentration of indium in the semiconductor layer including indium of the second active layer (230).

If the amount of wedge-shaped grooves (225) generated in the first active layer (220) becomes excessively large, a phenomenon of reducing the surface area that can emit light may occur. The density of the wedge-shaped grooves can be controlled by controlling the amount of indium injected and the temperature of the first active layer formation during the formation of the first active layer. If the amount of indium is reduced and the growth temperature is lowered to about 900° C. in an ammonia atmosphere, the density of the wedge-shaped grooves can be reduced. For example, the concentration of indium in the semiconductor layer including indium of the first active layer (220) may be lower by 70% or less, more preferably 50% or less, than the concentration of indium in the semiconductor layer including indium of the second active layer (230).

The second conductive semiconductor layer (240) is formed on the second active layer (230). The second conductive semiconductor layer (240) may be formed of a p-type nitride semiconductor doped with a p-type impurity, such as magnesium (Mg), such as p-GaN.

An electron blocking layer may be additionally formed between the second active layer (230) and the second conductive semiconductor layer (240) to prevent overflow of electrons supplied from the first conductive semiconductor layer (210). The electron blocking layer may be formed of a high-resistance material such as AlGaN.

If the second conductive semiconductor layer (240) is formed with a relatively thick thickness, the wedge-shaped groove portion of the second active layer (230) can also be filled, and a flattened second conductive semiconductor layer (240) can be formed.

A semiconductor light source for a display according to the present invention can be manufactured as follows:

First, a first conductive semiconductor layer (210), such as an n-GaN layer, is formed on a substrate (201) such as PSS. When forming the first conductive semiconductor layer, the growth temperature is preferably 1000°C or higher, and more preferably 1100°C or higher. If the growth temperature of the first conductive semiconductor layer is too low, various problems may occur that adversely affect the luminescence efficiency or life characteristics, such as insufficient doping and deterioration of crystal quality.

Next, a first active layer (220) such as InGaN/GaN with a superlattice structure is formed on the first challenge-type semiconductor layer (210). At this time, a wedge-shaped groove (225) is formed on the top of the first active layer (220).

In the step of forming the first active layer (220), a semiconductor layer containing indium, such as an InGaN layer, and a semiconductor layer not containing indium, such as a GaN layer, are alternately laminated. A threading potential is formed by penetrating the first conductive semiconductor layer (210) and the first active layer (220), and a wedge-shaped groove (225) is formed on the top of the first active layer (220) that intersects the threading potential.

Next, while maintaining the wedge-shaped groove (225), a second active layer (230) having a multi-well structure, such as an InGaN/GaN multi-well active layer, is formed on the first active layer (220). The second active layer (230) is formed to cover the upper surface of the first active layer (220) including the inclined surface of the wedge-shaped groove (225), so that the wedge-shaped groove (225) extends to the second active layer (230).

Next, a second conductive semiconductor layer (240) is formed on the second active layer (230).

Figure 4 shows the surface and cross-section of the active layer of a semiconductor light source according to the present invention.

Referring to FIG. 4, it can be seen that a wedge-shaped groove is maintained on the surface of the second active layer of the semiconductor light source according to the present invention. In addition, it can be seen that the threading potential penetrating the first active layer (220) is terminated in the second active layer (230).

In the case of a semiconductor light source according to the present invention, a light-emitting layer based on an InGaN material can be formed on the inclined surface of a wedge-shaped groove, and a light-emitting phenomenon can occur by injection of electrons and holes. Such light-emitting can be implemented through a wedge-shaped groove structure, so that a wider light-emitting layer can be secured compared to forming a light-emitting layer through a conventional planar structure. Therefore, threading dislocation defects can be suppressed through the wedge-shaped groove structure, and light-emitting can be achieved through a multi-quantum well layer grown on the inclined surface of the wedge-shaped groove, so that an improvement in light efficiency and an increase in light-emitting amount can be expected.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

201 : Substrate
205: Undoped semiconductor layer
210: 1st challenge type semiconductor layer
220: 1st active layer
230: 2nd active layer
240: Second challenge type semiconductor layer
250 : Penetrating potential

Claims (8)

A step of forming a first conductive semiconductor layer on a substrate;
A step of forming a first active layer having a superlattice structure in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated on the first challenging semiconductor layer, wherein a wedge-shaped groove is formed on the upper end of the first active layer;
A step of forming a second active layer having a multi-well structure in which semiconductor layers containing indium and semiconductor layers not containing indium are alternately laminated on the first active layer while maintaining the wedge-shaped groove;
Comprising a step of forming a second conductive semiconductor layer on the second active layer,
A penetration potential is formed through the first conductive semiconductor layer and the first active layer, and a wedge-shaped groove is formed on the upper part of the first active layer intersecting with the penetration potential.
The step of forming the first active layer is performed at a lower temperature than the step of forming the first conductive semiconductor layer.
A method for manufacturing a semiconductor light source, characterized in that the concentration of indium in the semiconductor layer including indium of the first active layer is lower than the concentration of indium in the semiconductor layer including indium of the second active layer.
In the first paragraph,
A method for manufacturing a semiconductor light source, characterized in that the above-mentioned threading potential is terminated in the second active layer. delete delete delete delete delete delete