KR100898586B1 - Light emitting diode - Google Patents

Abstract

A light emitting diode is disclosed. The light emitting diode includes a gallium nitride series N-type compound semiconductor layer and a gallium nitride series P-type compound semiconductor layer. An active layer is interposed between the N-type and P-type compound semiconductor layers, and an N-type Al _x Ga _{1 - x} N clad layer and a P-type Al _y Ga _{1 - y} N clad layer are respectively disposed between the N-type compound semiconductor layer and the active layer. And interposed between the N-type compound semiconductor layer and the active layer. Here, the Al composition ratio of the N-type cladding layer is the same as the Al composition ratio of the P-type cladding layer, and the thickness of the N-type cladding layer is relatively thicker than that of the P-type cladding layer. The Al composition ratio of the N-type cladding layer is the same as that of the P-type cladding layer, which simplifies the light emitting diode manufacturing process and prevents the crystallinity of the compound semiconductor layers from dropping. By relatively thickening it can control the rate at which electrons are introduced into the active layer.

Light-emitting diodes, gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), superlattice

Description

Light Emitting Diodes {LIGHT EMITTING DIODE}

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

2 is a cross-sectional view illustrating a light emitting diode according to another embodiment of the present invention.

The present invention relates to a light emitting diode, and more particularly to a light emitting diode having an n- clad layer and a p- clad layer of AlGaN.

In general, nitrides of Group III elements such as gallium nitride (GaN), aluminum nitride (AlN), and indium gallium nitride (InGaN) have excellent thermal stability and have a direct transition energy band structure. It is attracting much attention as a material for light emitting diodes in the ultraviolet region. In particular, indium gallium nitride (InGaN) compound semiconductors have attracted much attention due to their narrow band gap. Light emitting diodes using gallium nitride-based compound semiconductors are being used in a variety of applications such as large-scale color flat panel display, backlight light source, traffic light, indoor lighting, high density light source, high resolution output system and optical communication.

Recently, high-efficiency white LEDs are expected to replace fluorescent lamps. In particular, the efficiency of white LEDs has reached a level similar to that of conventional fluorescent lamps. However, the LED efficiency can be further improved, and thus, continuous efficiency improvement is further required. In particular, it is required to increase the internal quantum efficiency by improving the crystal quality and epilayer structure. .

Regarding the epilayer structure, conventional LEDs include an N-type AlGaN cladding layer between N-type GaN and an active layer, and a P-type AlGaN cladding layer between the P-type GaN and the active layer, whereby electrons and holes are formed by the clad layers. Adopt a structure to increase the recombination rate.

On the other hand, in the GaN-based compound semiconductor, the electron mobility is 100 times larger than the mobility of the holes, so that when the N-type AlGaN cladding layer and the P-type AlGaN cladding layer having the same Al composition ratio are adopted, the electrons are relatively As soon as it passes through the active layer, the recombination rate of electrons and holes is reduced. In order to prevent this, the Al composition ratio of the N-type AlGaN cladding layer can be relatively high compared to the Al composition ratio of the P-type AlGaN cladding layer to control the inflow rate of electrons, but the Al composition ratio of the N-type AlGaN cladding layer increases with Al and Due to the atomic size difference between Ga and Al and In, the crystallinity of the active layer and other semiconductor layers is degraded. In addition, when the Al composition ratio of the N-type cladding layer and the P-type cladding layer is different, process parameters of the growth process for growing the two layers, for example, source flow rates of Al, Ga, and N, must be changed. The manufacturing process can be complicated.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting diode capable of controlling an inflow rate of electrons introduced into an active layer without reducing crystallinity.

Another object of the present invention is to provide a light emitting diode which can prevent the manufacturing process from becoming complicated.

In order to achieve the above technical problem, a light emitting diode according to an aspect of the present invention includes a gallium nitride-based N-type compound semiconductor layer and a gallium nitride-based P-type compound semiconductor layer. An active layer is interposed between the N-type and P-type compound semiconductor layers. On the other hand, an Al _x Ga _{1 - x} N clad layer is interposed between the N-type compound semiconductor layer and the active layer, and a P-type Al _y Ga _1-y N clad layer is interposed between the P-type compound semiconductor layer and the active layer. Here, 0 <x, y ≦ 1, x = y, and the thickness of the N-type Al _x Ga _{1 - x} N cladding layer is relatively thick compared to the P-type Al _y Ga _{1 - y} N cladding layer.

According to the present aspect, the Al composition ratio of the N-type cladding layer and the Al composition ratio of the P-type cladding layer are the same, and the thickness of the N-type cladding layer is thicker than that of the P-type cladding layer, so that the compound semiconductor layer of the conventional Al compositional ratio increases. It is possible to control the inflow rate of the electrons flowing into the active layer while preventing the crystalline decrease. In addition, since the Al composition ratio of the N-type cladding layer and the Al composition ratio of the P-type cladding layer are the same, the process parameters for growing the N-type and P-type cladding layers, for example, the source flow rates of Al, Ga, and N can be matched to emit light. The diode manufacturing process can be simplified.

The active layer may be a single quantum well or a multilayer quantum well including an InGaN compound semiconductor layer. Accordingly, it is possible to provide a light emitting diode that emits light in the ultraviolet to visible light region by changing the composition ratio of In. The N-type compound semiconductor layer may be formed of N-type GaN, and the P-type compound semiconductor layer may be formed of P-type GaN.

On the other hand, x may be in the range of 0.08 ~ 0.15. When x is less than 0.08, the bandgap of the clad layer is narrow to prevent blocking of electrons or holes, and when x is more than 0.15, crystallinity may be reduced by increasing lattice mismatch.

A light emitting diode according to another aspect of the present invention includes a gallium nitride-based N-type compound semiconductor layer and a gallium nitride-based P-type compound semiconductor layer. An active layer is interposed between the N-type and P-type compound semiconductor layers. Meanwhile, an N-type cladding layer having a super lattice structure in which Al _x Ga _{1 - x} N and In _z Ga _{1 - z} N are stacked is interposed between the N-type compound semiconductor layer and the active layer, and P-type Al _y Ga _{1 - y} An N clad layer is interposed between the P-type compound semiconductor layer and the active layer. Here, 0 <x, y, z ≦ 1, x = y, and the total thickness of Al _x Ga _{1 - x} N in the N-type cladding layer is relatively higher than that of the P-type Al _y Ga _{1 - y} N cladding layer. thick.

According to this aspect, the crystal lattice mismatch due to lattice mismatch can be alleviated by employing an N-type cladding layer having a superlattice structure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, a gallium nitride series N-type compound semiconductor layer 25 is positioned on a substrate 11. In addition, a buffer layer 23 may be interposed between the substrate 21 and the N-type compound semiconductor layer 25, and the buffer layer may include a low temperature buffer layer and a high temperature buffer layer. For example, sapphire, spinel, silicon carbide substrate, and the like.

A gallium nitride series P-type compound semiconductor layer 33 is positioned on the N-type compound semiconductor layer 25, and an active layer 29 between the N-type compound semiconductor layer 25 and the P-type compound semiconductor layer 33. This intervenes. The N-type compound semiconductor layer and the P-type compound semiconductor layer may be formed of a group III nitride semiconductor layer of (Al, Ga, In) N series. For example, the N-type compound semiconductor layer 25 and the P-type compound semiconductor layer 33 may be formed of N-type and P-type GaN, respectively.

The active layer 29 may be a single quantum well having a single well layer or a multi quantum well in which a well layer and a barrier layer are alternately stacked. The well layer may be formed of InGaN, and the barrier layer may be formed of (Al, In, Ga) N. The well layer contains more In than the barrier layer to form quantum wells.

Meanwhile, an Al _x Ga _{1 - x} N cladding layer 27 is interposed between the N-type compound semiconductor layer 25 and the active layer 29, and between the P-type compound semiconductor layer 33 and the active layer 29. The P-type Al _y Ga _1-y N cladding layer 31 is interposed. Here, 0 <x, y≤1, and x = y. That is, the Al composition ratio of the N-type cladding layer 27 is the same as the Al composition ratio of the P-type cladding layer 31. Composition ratios x and y of the N-type and P-type cladding layers 27 and 31 may be in a range of 0.08 to 0.15. When x or y is less than 0.08, the bandgap of the clad layer is narrow to prevent electrons or holes, and when x or y is more than 0.15, the crystallinity of the compound semiconductor layers may be reduced by increasing the lattice mismatch.

Meanwhile, the thickness of the N-type cladding layer 27 is relatively thicker than that of the P-type cladding layer 31. For example, the thickness of the P-type cladding layer 31 may be 100 to 300Å, and the thickness of the N-type cladding layer 27 may be formed to be 100 to 500Å thicker than the thickness of the P-type cladding layer 31. have. Accordingly, the inflow rate of the electrons flowing into the active layer 29 from the N-type compound semiconductor layer 25 can be controlled.

2 is a cross-sectional view illustrating a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 2, as described with reference to FIG. 1, a gallium nitride-based N-type compound semiconductor layer 25 is positioned on the substrate 11, and the substrate 21 and the N-type compound semiconductor layer 25 are positioned. A buffer layer 23 may be interposed therebetween. Further, a gallium nitride-based P-type compound semiconductor layer 33 is positioned on the N-type compound semiconductor layer 25, and the N-type compound semiconductor layer 25 and P An active layer 29 is interposed between the type compound semiconductor layers 33. The N type compound semiconductor layer and the P type compound semiconductor layer may be formed of a group III nitride semiconductor layer of (Al, Ga, In) N series. For example, the N-type compound semiconductor layer 25 and the P-type compound semiconductor layer 33 may be formed of N-type and P-type GaN, respectively, and the active layer 29 may have a single quantum having a single well layer. The well layer may be a multi-quantum well in which a well layer and a barrier layer are alternately stacked.The well layer is formed of InGaN, and the barrier layer is (A 1, In, Ga) N. The well layer includes more In than the barrier layer to form quantum wells.

Meanwhile, an N-type cladding layer 37 having a super lattice structure in which Al _x Ga _{1 - x} N and In _z Ga _1-z N are alternately stacked between the N-type compound semiconductor layer 25 and the active layer 29 is formed. The P-type Al _y Ga _{1 - y} N cladding layer 31 is interposed between the P-type compound semiconductor layer 33 and the active layer 29. Here, 0 <x, y, z≤1, and x = y. That is, the Al composition ratio in Al _x Ga _{1 - x} N of the N-type cladding layer 37 is the same as the Al composition ratio of the P-type cladding layer 31. In addition, the Al composition ratio of Al _x Ga _{1 - x} N of the N-type cladding layer 37 and the Al composition ratio x and y of the P-type cladding layer 31 may be in a range of 0.08 to 0.15.

Meanwhile, the total thickness of Al _x Ga _{1 - x} N in the N-type cladding layer 27 is relatively thicker than that of the P-type cladding layer 31. For example, the thickness of the P-type cladding layer 31 may be 100 to 300Å, and the total thickness of Al _x Ga _{1 - x} N in the N-type cladding layer 27 is the thickness of the P-type cladding layer 31. Compared to 100 ~ 500Å can be formed thick. Accordingly, the inflow rate of the electrons flowing into the active layer 29 from the N-type compound semiconductor layer 25 can be controlled. On the other hand, the total thickness of InzGa1-zN in the N-type cladding layer 37 is preferably thin compared to the total thickness of Al _x Ga _{1 - x} N in order to prevent the overall thickness of the cladding layer from being excessively thick.

According to the present embodiment, the N-type cladding layer 37 having the superlattice structure is adopted to form the N-type compound semiconductor layer 25 and the N-type cladding layer 37, or the N-type cladding layer 37 and the active layer 29. The crystallinity can be improved by mitigating lattice mismatches therebetween.

According to the embodiments of the present invention, by making the Al composition ratio of AlGaN of the N-type cladding layer and AlGaN of the P-type cladding layer to be the same, it is possible to simplify the process and to prevent crystalline reduction and to further reduce the N-type cladding. By controlling the thickness of AlGaN of the layer can provide a light emitting diode that can control the flow rate of the electrons flowing into the active layer.

Claims (6)

Gallium nitride-based N-type compound semiconductor layers; Gallium nitride-based P-type compound semiconductor layers; An active layer interposed between the N-type and P-type compound semiconductor layers; An N-type Al _x Ga _1-x N cladding layer interposed between the N-type compound semiconductor layer and an active layer; P-type Al _y Ga _1-y N cladding layer interposed between the P-type compound semiconductor layer and the active layer, 0 <x, y ≦ 1, x = y, and the thickness of the N _- type Al _x Ga _1-x N cladding layer is 100 to 500 Å thicker than the P-type Al _y Ga _1-y N cladding layer. Light emitting diode. The method according to claim 1, The active layer includes an InGaN compound semiconductor layer, The N-type compound semiconductor layer is formed of N-type GaN, The P-type compound semiconductor layer is a light emitting diode formed of P-type GaN. The method according to claim 1, x is in the range of 0.08 ~ 0.15. Gallium nitride-based N-type compound semiconductor layers; Gallium nitride-based P-type compound semiconductor layers; An active layer interposed between the N-type and P-type compound semiconductor layers; An N-type cladding layer interposed between the N-type compound semiconductor layer and the active layer and having a lattice structure in which Al _x Ga _1-x N and In _z Ga _1-z N are stacked; P-type Al _y Ga _1-y N cladding layer interposed between the P-type compound semiconductor layer and the active layer, 0 <x, y, z≤1, x = y, and the total thickness of Al _x Ga _1-x N in the N _- type cladding layer is 100 to 500 Å more than that of the P-type Al _y Ga _1-y N cladding layer Light-emitting diode, characterized in that the thick. The method according to claim 4, The active layer includes an InGaN compound semiconductor layer, The N-type compound semiconductor layer is formed of N-type GaN, The P-type compound semiconductor layer is a light emitting diode formed of P-type GaN. The method according to claim 4, x is in the range of 0.08 ~ 0.15.

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