KR101803647B1 - P-type semiconductor layer structure and uv light-emitting device including the same - Google Patents

Abstract

A p-type semiconductor layer structure includes a p-type semiconductor layer, an electrode structure including metal patterns which are formed on the p-type semiconductor layer and cross each other and ohmic contact patterns which are interposed between the metal patterns and the p-type semiconductor layer along the metal patterns and form ohmic contacts with the metal patterns, and a light reflecting structure formed to cover the electrode structure, thereby improving an ohmic contact characteristic and light extraction efficiency.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a p-type semiconductor layer structure and an ultraviolet light emitting device including the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a p-type semiconductor layer structure and an ultraviolet light emitting device including the same, and more particularly, to a p-type semiconductor layer structure and an ultraviolet light emitting device including the p- .

Research on light-emitting diodes (UV-LEDs) in the ultraviolet spectrum has been actively conducted worldwide due to its various applicability.

Particularly, it is possible to realize efficient UV LEDs in the ultraviolet C region, ultraviolet A region and ultraviolet B spectral region according to the ultraviolet spectrum region.

The UV LED uses an epitaxial layer made of AlGaN as a base semiconductor layer. At this time, as the light in a short wavelength region such as UV-C (ultraviolet C region having a short wavelength of 280 nm or less) is emitted, the content of aluminum (Al) contained in the epitaxial layer increases. As the content of aluminum (Al) increases in the epitaxial layer, the electrical conductivity of AlGaN is markedly deteriorated, and the doping efficiency is also drastically reduced.

In particular, the p-type semiconductor layer made of p-type AlGaN and the metal electrode do not form an ohmic contact with each other and have high contact resistance. As a result, there is a problem that heat generation of the light emitting element is caused and current injection efficiency is lowered.

In order to solve this problem, a contact layer made of p- (In) GaN, which forms an ohmic contact with a metal electrode, is interposed between the metal electrode and the semiconductor layer to form a p-type semiconductor layer and a metal electrode A technique has been developed to form an ohmic contact therebetween.

However, the contact layer made of p- (In) GaN has a problem in that the light extraction efficiency of the light emitting device is lowered by absorbing ultraviolet rays having a wavelength band of 280 nm or less generated from the light emitting device.

It is an object of the present invention to provide a p-type semiconductor layer structure capable of improving the ohmic characteristics between the p-type semiconductor layer and the metal electrode and increasing the light extraction efficiency of the light emitting device.

It is another object of the present invention to provide an ultraviolet light emitting device including a p-type semiconductor layer structure capable of improving the ohmic characteristics between the p-type semiconductor layer and the metal electrode and increasing the light extraction efficiency of the light emitting device.

A p-type semiconductor layer structure according to an embodiment of the present invention includes a p-type semiconductor layer, a plurality of metal patterns formed on the p-type semiconductor layer, An electrode structure interposed between the metal patterns and having a single layer structure and having ohmic contact patterns to form an ohmic contact with the metal patterns, and an electrode structure directly contacting the metal patterns, Light reflection structure.

In an embodiment of the present invention, the electrode structure may have a mesh shape as a whole.

In one embodiment of the present invention, the p-type semiconductor layer may be formed of a p-type AlGaN material, and the ohmic contact pattern may be formed of a p-type (In) GaN material.

In one embodiment of the present invention, the light reflecting structure may include transparent insulating film patterns formed between the electrode structures on the p-type semiconductor layer, and a metal reflecting layer formed to cover the electrode structures and the insulating film patterns. have.

In one embodiment of the present invention, the insulating film patterns may include a material having a refractive index of 1.5 or less.

An ultraviolet light emitting device according to an embodiment of the present invention is formed on a substrate and includes a light emitting structure including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer, And an ohmic contact pattern formed between the metal patterns and the p-type semiconductor layer along the metal patterns and having a single layer structure and forming ohmic contacts with the metal patterns, And a light reflecting structure provided to directly contact the metal patterns and cover the electrode structure.

In one embodiment of the present invention, the electrode structures may have a mesh shape as a whole.

In one embodiment of the present invention, the p-type semiconductor layer may be formed of a p-type AlGaN material, and the ohmic contact pattern may be formed of a p-type (In) GaN material.

In one embodiment of the present invention, the light reflecting structure includes transparent insulating film patterns formed between the electrode structures on the p-type semiconductor layer and made of a material having a refractive index of 1.5 or less, And a metal reflective layer formed to cover the insulating film patterns.

In one embodiment of the present invention, the light emitting structure may further include an electron blocking layer interposed between the active layer and the p-type semiconductor layer.

According to embodiments of the present invention, the p-type semiconductor layer structure includes an electrode structure having a mesh shape. Thus, the ohmic contact patterns included in the electrode structure can form ohmic contacts with the metal patterns. By this, the contact resistance in the electrode structure is reduced, so that the exothermic phenomenon that may occur from the electrode structure can be suppressed. Further, since the ohmic contacts are formed between the ohmic contact patterns and the metal patterns, a current supplied from the outside is effectively injected into the p-type semiconductor layer, thereby improving current injection characteristics.

In addition, since the electrode structure has a lamination pattern structure that does not cover the p-type semiconductor layer as a whole, the light absorption effect absorbed into the electrode structure can be reduced. Accordingly, when the p-type semiconductor layer structure is applied to an ultraviolet light-emitting device, the ultraviolet light-emitting device can secure improved light extraction efficiency.

1 is a cross-sectional view illustrating a p-type semiconductor layer structure according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a p-type semiconductor layer structure according to an embodiment of the present invention.
3 is a plan view for explaining the p-type semiconductor layer structure (excluding the light reflection structure) of FIG. 2;
4 is a cross-sectional view illustrating an ultraviolet light-emitting device according to an embodiment of the present invention.
5 is a cross-sectional view illustrating an ultraviolet light-emitting device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the accompanying drawings, the sizes and the quantities of objects are shown enlarged or reduced from the actual size for the sake of clarity of the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprise", "comprising", and the like are intended to specify that there is a feature, step, function, element, or combination of features disclosed in the specification, Quot; or " an " or < / RTI > combinations thereof.

On the other hand, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a cross-sectional view illustrating a p-type semiconductor layer structure according to an embodiment of the present invention.

1, a p-type semiconductor layer structure 100 according to an embodiment of the present invention includes a p-type semiconductor layer 110, an electrode structure 120, and a light reflecting structure 130. Referring to FIG.

The p-type semiconductor layer 110 may be formed of a semiconductor material doped with a p-type impurity such as a Group 2 metal element. For example, the p-type semiconductor layer 110 may be made of aluminum-gallium nitride (AlGaN) doped with a Group II metal element. The p-type semiconductor layer 110 may function as a p-type semiconductor layer among elements forming the P-N junction of the light emitting device.

The electrode structure 120 is formed on the p-type semiconductor layer 110. The electrode structure 120 may be electrically connected to an external current source. Thus, current may be applied to the p-type semiconductor layer 110 through the electrode structure 120.

The electrode structure 120 includes metal patterns 123 and ohmic contact patterns 121.

The metal patterns 123 are provided so as to cross each other. As a result, the metal patterns 123 can be electrically connected as a whole. For example, the metal patterns 123 may have a mesh structure. The metal patterns 123 may be formed of nickel (Ni), gold (Au), palladium (Pd), platinum (Pt), silver (Ag) The metal patterns 123 function as metal electrodes.

The ohmic contact patterns 121 are formed between the metal patterns 123 and the p-type semiconductor layer 110. The ohmic contact patterns 121 are formed along the metal patterns 123.

The ohmic contact patterns 121 may form an ohmic contact with the metal patterns 123. For example, when the p-type semiconductor layer 110 is formed of a p-type AlGaN material, the ohmic contact patterns 121 may be formed of a p-type (In) GaN material. By this, the contact resistance in the electrode structure is reduced, so that the exothermic phenomenon that may occur from the electrode structure can be suppressed. In addition, since an ohmic contact is formed between the ohmic contact patterns 121 and the metal patterns 123, an electric current supplied from the outside is effectively injected into the p-type semiconductor layer 110, Can be improved.

In addition, since the electrode structure has a lamination pattern structure that does not cover the p-type semiconductor layer 110 as a whole, the light absorption effect absorbed into the electrode structure can be reduced. Accordingly, when the p-type semiconductor layer structure 100 is applied to an ultraviolet light emitting device, the ultraviolet light emitting device can secure an improved light extraction efficiency.

The metal patterns 123 and the ohmic contact patterns 121 included in the electrode structure may have a laminated structure in which the p-type semiconductor layers 110 do not completely cover each other and intersect with each other like a mesh. Accordingly, the current spreading effect can be increased. That is, when the electrode structures do not cross each other and have island shapes, the electrode structures may be separated from each other, thereby deteriorating the current spreading effect. On the other hand, the current spreading effect can be improved as the metal patterns 123 included in the electrode structure according to the present invention and the ohmic contact patterns 121 cross each other.

The light reflection structure 130 is provided to cover the electrode structure 120. Accordingly, light incident toward the light reflection structure can be reflected toward the p-type semiconductor layer without leaking to the outside.

The light reflecting structure 130 may be made of silver (Ag), aluminum (Al), or ruthenium (Rh), for example.

2 is a cross-sectional view illustrating a p-type semiconductor layer structure according to an embodiment of the present invention. 3 is a plan view for explaining the p-type semiconductor layer structure (excluding the light reflection structure) of FIG. 2;

2 and 3, a p-type semiconductor layer structure 100 according to an embodiment of the present invention includes a p-type semiconductor layer 110, an electrode structure 120, and a light reflecting structure 130 do. Here, the light reflecting structure 130 is different from the light reflecting structure shown in FIG. Therefore, the light reflecting structure 130 will be described later.

As shown in FIG. 3, the electrode structure 120 has various types of mesh structures.

The light reflection structure 130 includes transparent insulating film patterns 133 and a metal reflection layer 131.

The transparent insulating layer patterns 133 are formed between the electrode structures 120 on the p-type semiconductor layer 110. The transparent insulating layer patterns 133 are formed of a material that can effectively transmit light so that light reflected from the metal reflective layer 131 can enter the p-type semiconductor layer 110 again .

The metal reflection layer 131 is formed to cover the electrode structure 120 and the insulating film patterns 133. The metal reflection layer 131 may be made of silver (Ag), aluminum (Al), or ruthenium (Rh), for example.

In one embodiment of the present invention, the insulating layer pattern 133 may include a material having a refractive index of 1.5 or less. For example, the insulating film pattern 133 may be formed of magnesium fluoride, silicon oxide, silicon nitride, or silicon oxynitride.

Since the transparent insulating film patterns 133 have a refractive index of 1.5 or less, the transparent insulating film patterns 133 can function as an omni-directional reflector (ODR) together with the metal light reflecting layer. As a result, the light reflecting structure 130 including the transparent insulating layer patterns 133 and the metal reflecting layer 131 can have improved light reflection efficiency. Accordingly, when the p-type semiconductor layer structure 100 is applied to an ultraviolet light emitting device, the ultraviolet light emitting device can have a higher light extraction efficiency.

4 is a cross-sectional view illustrating an ultraviolet light-emitting device according to an embodiment of the present invention.

Referring to FIG. 4, an ultraviolet light emitting device 20 according to an embodiment of the present invention includes a light emitting structure, an electrode structure, and a light reflecting structure formed on a substrate 10. The substrate 10 may include at least one of sapphire (Al 2 O 3), GaN, SiC, ZnO, GaP, InP, Ga 2 O 3, GaAs and Si. For example, a buffer layer (not shown) may be additionally interposed between the substrate 10 and the light-emitting structure to improve the difference in thermal expansion coefficient and lattice mismatch. The buffer layer may be made of, for example, Al, In, N or Ga.

The light emitting structure is formed on the substrate 10. The light emitting structure includes n-type semiconductor layers 11a and 11b, an active layer 12, and a p-type semiconductor layer 110. Thus, the light emitting structure can emit light, particularly ultraviolet light.

The n-type semiconductor layers 11a and 11b are disposed on the substrate 10. The n-type semiconductor layers 11a and 11b may be formed of a compound semiconductor such as a group III-V or II-VI doped with an n-type dopant. The n-type dopant may include, but is not limited to, Si, Ge, Sn, Se, and Te.

The n-type semiconductor layers 11a and 11b may include one or more of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, .

The active layer 12 is disposed on the n-type semiconductor layers 11a and 11b. Electrons (or holes) injected through the n-type semiconductor layers 11a and 11b and holes (or electrons) injected through the p-type semiconductor layer 110 meet with each other to form the active layer 12 It can emit light with energy determined by the material's inherent energy band.

The active layer 12 may be at least one of a single well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW), a quantum-wire structure, or a quantum dot structure It can be formed in any one of them.

The well layer / barrier layer forming the active layer 12 is formed of any one or more of a pair of InGaN / GaN, InGaN / InGaN, GaN / AlGaN, InAlGaN / GaN, GaAs (InGaAs) / AlGaAs, GaP (InGaP) But is not limited to. The well layer may be formed of a material having a band gap energy lower than the band gap energy of the barrier layer.

In particular, the active layer 12 emits light in the ultraviolet wavelength band of 100 nm to 400 nm. In this case, the n-type conductivity type semiconductor layers 11a and 11b are implemented as AlGaN, and absorption of ultraviolet light can be minimized.

In addition, an electron blocking layer 13 may be further interposed between the active layer 12 and the p-type conductivity type semiconductor layer 110.

The electron barrier layer 13 may have a larger band gap energy than the barrier layer of the active layer 12. The electron blocking layer 13 serves to prevent electrons, which are carriers supplied from the n-type semiconductor layers 11a and 11b to the active layer 12, from being introduced into the p-type semiconductor layer 110 .

The p-type semiconductor layer 110 is disposed on the active layer 12. The p-type semiconductor layer 110 is made of a compound semiconductor such as a III-V group or a II-VI group. The p-type conductivity-type semiconductor layer 110 may be doped with Mg, Zn, Ca, Sr, or Ba as a p-type dopant.

Thus, the light emitting structure including the n-type semiconductor layers 11a and 11b, the active layer 12, and the p-type semiconductor layer 110 can have a P-N junction structure.

The electrode structure is formed on the p-type semiconductor layer 110. The electrode structure may be electrically connected to an external current source (not shown). Thus, current may be applied to the p-type semiconductor layer 110 through the electrode structure.

The electrode structure includes metal patterns 123 and ohmic contact patterns 121.

The metal patterns 123 are provided so as to cross each other. As a result, the metal patterns 123 can be electrically connected as a whole. For example, the metal patterns 123 may have a mesh structure. The metal patterns 123 may be formed of Ni, Au, Pd, Pt, Ag, or the like. The metal patterns 123 function as metal electrodes.

The ohmic contact patterns 121 are formed between the metal patterns 123 and the p-type semiconductor layer 110. The ohmic contact patterns 121 are formed along the metal patterns 123.

The light reflection structure may be made of silver (Ag), aluminum (Al), or ruthenium (Rh), for example.

According to embodiments of the present invention, the ohmic contact patterns 121 may form ohmic contacts with the metal patterns 123. For example, when the p-type semiconductor layer 110 is formed of a p-type AlGaN material, the ohmic contact patterns 121 may be formed of a p-type (In) GaN material. By this, the contact resistance in the electrode structure is reduced, so that the exothermic phenomenon that may occur from the electrode structure can be suppressed. In addition, since an ohmic contact is formed between the ohmic contact patterns 121 and the metal patterns 123, an electric current supplied from the outside is effectively injected into the p-type semiconductor layer 110, Can be improved.

In addition, since the electrode structure has a lamination pattern structure that does not cover the p-type semiconductor layer 110 as a whole, the light absorption effect absorbed into the electrode structure can be reduced. The ultraviolet light emitting device can secure an improved light extraction efficiency.

The metal patterns 123 and the ohmic contact patterns 121 included in the electrode structure may have a laminated structure in which the p-type semiconductor layers 110 do not completely cover each other and intersect with each other like a mesh. Accordingly, the current spreading effect can be increased. That is, when the electrode structures do not cross each other and have island shapes, the electrode structures may be separated from each other, thereby deteriorating the current spreading effect. On the other hand, the current spreading effect can be improved as the metal patterns included in the electrode structure according to the present invention and the ohmic contact patterns cross each other.

The light reflection structure is provided to cover the electrode structures. Accordingly, light incident toward the light reflection structure can be reflected toward the p-type semiconductor layer without leaking to the outside.

5 is a cross-sectional view illustrating an ultraviolet light-emitting device according to an embodiment of the present invention.

Referring to FIG. 5, an ultraviolet light emitting device 20 according to an embodiment of the present invention includes a light emitting structure, an electrode structure, and a light reflecting structure formed on a substrate 10. The ultraviolet light-emitting device according to Fig. 5 has a structure in which the ultraviolet light-emitting device described above with reference to Fig. 4 is reversed upside down. That is, the ultraviolet light emitting device according to FIG. 5 has a structure in which the n-type semiconductor layer is located on the upper side and the p-type semiconductor layer is located on the lower side.

10: substrate 11a, 11b: n-type semiconductor layer
12: active layer 13: electron blocking layer
110: p-type semiconductor layer 120: electrode structure
130: light reflecting structure

Claims (10)

a p-type semiconductor layer;
The semiconductor device according to claim 1, wherein the metal patterns and the p-type semiconductor layer are disposed on the p-type semiconductor layer and are interposed between the metal patterns and the p-type semiconductor layer, An electrode structure having ohmic contact patterns to form ohmic contact patterns; And
A p-type semiconductor layer structure directly contacting the metal patterns and covering the electrode structure. The p-type semiconductor layer structure according to claim 1, wherein the electrode structure has a mesh shape as a whole. The p-type semiconductor layer structure according to claim 1, wherein the p-type semiconductor layer is made of a p-type AlGaN material and the ohmic contact pattern is made of a p-type (In) GaN material. The light reflection structure according to claim 1, wherein the light reflection structure includes transparent insulation film patterns formed between the electrode structures on the p-type semiconductor layer, and a metal reflection layer formed to cover the electrode structures and the insulation film patterns A p-type semiconductor layer structure. The p-type semiconductor layer structure according to claim 4, wherein the insulating film patterns include a material having a refractive index of 1.5 or less. A light emitting structure formed on the substrate and including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer;
Type semiconductor layer, the metal patterns and the p-type semiconductor layer are formed on the p-type semiconductor layer, the metal patterns are interposed between the metal patterns and the p-type semiconductor layer, Electrode structures having ohmic contact patterns that form ohmic contact patterns; And a light reflection structure directly contacting the metal patterns and covering the electrode structure. The ultraviolet light emitting device according to claim 6, wherein the electrode structure has a mesh shape as a whole. 7. The ultraviolet light emitting device according to claim 6, wherein the p-type semiconductor layer is made of a p-type AlGaN material and the ohmic contact pattern is made of a p-type (In) GaN material. [7] The method of claim 6, wherein the light reflecting structure includes transparent insulating film patterns formed between the electrode structures on the p-type semiconductor layer and made of a material having a refractive index of 1.5 or less, And a metal reflective layer formed thereon. The ultraviolet light emitting device according to claim 6, wherein the light emitting structure further comprises an electron blocking layer interposed between the active layer and the p-type semiconductor layer.

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