KR20170048898A - Light emittng device and light emitting device package including the same - Google Patents

Abstract

An embodiment of the present invention provides a light emitting device which includes: a first conductive type semiconductor layer including a first layer and a second layer; an active layer of a multiple quantum well structure disposed on the first conductive type semiconductor layer; a second conductive type semiconductor layer disposed on the active layer; and a first electrode and a second electrode which are disposed on the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively, wherein the thickness of a quantum well is thicker than the thickness of a quantum wall. Accordingly, the present invention can improve thermal conductivity and current spreading.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting device and a light emitting device package including the light emitting device.

The present invention relates to a light emitting device, and more particularly, to a light emitting device having improved quality of a nitride based light emitting structure.

GaN, and AlGaN are widely used for optoelectronics and electronic devices due to their advantages such as wide and easy bandgap energy.

Particularly, a light emitting device such as a light emitting diode (Ligit Emitting Diode) or a laser diode using a semiconductor material of a 3-5 group or a 2-6 group compound semiconductor has been widely used in various fields such as red, green, blue and ultraviolet It can realize various colors, and it can realize efficient white light by using fluorescent material or color combination. It has low power consumption, semi-permanent lifetime, fast response speed, safety, and environment compared to conventional light sources such as fluorescent lamps and incandescent lamps Affinity.

Therefore, a transmission module of the optical communication means, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting element capable of replacing a fluorescent lamp or an incandescent lamp Diode lighting, automotive headlights, and traffic lights.

The light emitting device may be a nitride semiconductor, such as GaN, as a light emitting structure, and the light emitting structure may include a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer.

Since the substrate and the light emitting structure are different materials from each other in the nitride based semiconductor layer grown on the sapphire substrate which is an insulating substrate, the lattice mismatch is very large and the thermal expansion coefficient difference therebetween is very large, Dislocations, melt-backs, cracks, pits, surface morphology defects, and the like can occur.

Among the above-mentioned problems, ELOG (epitaxial lateral over-growth) growth method or Pendeo growth method has been proposed in order to suppress dislocation generation.

1 and 2 are views showing the growth of a conventional nitride-based semiconductor.

1 is a view showing an ELOG growth method. A mask is formed by a silicon oxide (SiO ₂ ) or the like in the middle of a nitride-based semiconductor (GaN) grown on a substrate, and the nitride-based semiconductor grown in the region between the masks is grown not only vertically but also horizontally , Defects can be removed in the region above the mask.

2 is a view showing a Pendeo growth method. A substrate is etched to form a groove, and a nitride-based semiconductor layer is grown on a substrate on which a groove is not formed. At this time, the nitride-based semiconductor grown in a part of the substrate may undergo vertical growth and horizontal growth, and the nitride-based semiconductor layer may be formed in the entire region above the substrate.

However, the growth of the conventional nitride-based semiconductor has the following problems.

In the case of the ELOG method, a tilt occurs due to the friction between the silicon oxide used as a mask and GaN, and a potential may be generated. Further, the nitride semiconductor grows horizontally on the mask, and the time for growing the nitride-based semiconductor may increase in the entire region above the mask.

In the case of the Pendeo method, etching to the sapphire substrate is indispensable, and the process time is increased and it is also difficult to etch an accurate pattern on the sapphire substrate.

As described above, the degradation of the quality of the nitride-based semiconductor layer constituting the light-emitting device can not be solved by the ELOC (epitaxial lateral over-growth) growth method or the Pendeo growth method.

The embodiment attempts to provide a light emitting device having reduced quality of crystal defects in a light emitting structure.

An embodiment includes a first conductive semiconductor layer including a first layer and a second layer; An active layer of a multiple quantum well structure disposed on the first conductive type semiconductor layer; A second conductive semiconductor layer disposed on the active layer; And a first electrode and a second electrode that are respectively disposed on the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, wherein the thickness of the quantum well is larger than the thickness of the quantum well.

The first and second layers may be doped with a first conductivity type dopant.

The second layer may be doped with the first conductivity type dopant by 1 x 10 ¹⁹ / cm ³ or more.

The first conductivity type dopant may be silicon.

The second layer may be from 3 micrometers to 10 micrometers in thickness.

10 to 20 pairs of quantum wells and quantum wells may be arranged.

The thickness of the quantum well may be greater than 40 ohms Strong, and the thickness of the quantum well may be less than 40 ohms.

The multiple quantum well can be made of InGaN / GaN.

A pattern may be formed on the bottom surface of the first layer.

Another embodiment includes a package body; A first lead frame and a second lead frame disposed on the package body and electrically separated from each other; And the above-described light emitting device flip-bonded to the first lead frame and the second lead frame.

The light emitting device according to the embodiments is advantageous for growing InGaN that is a quantum well (QW) because the nitride based semiconductor layer is grown on the same kind of substrate and the quality is excellent and the compressive strain is reduced. GaN, which is a substrate, has the same electric conductivity as the light emitting structure, so that the current spreading can be improved and the thermal conductivity can be improved.

1 and 2 are diagrams showing the growth of a conventional nitride-based semiconductor, and FIG.
3 is a cross-sectional view of an embodiment of a light emitting device,
4 is a detailed view showing the structure of the active layer of FIG. 3,
5 is a view showing bowing of GaN grown on bulk-GaN together with a comparative example,
6 is a diagram showing a comparison example and an operation voltage of the light emitting device according to the embodiment,
7 is a view showing various examples of the electrode arrangement of the light emitting device according to the embodiment,
8 is a view showing an embodiment of a light emitting device package in which a light emitting device is disposed.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

In the description of the embodiment according to the present invention, in the case of being described as being formed "on or under" of each element, the upper (upper) or lower (lower) or under are all such that two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements. In addition, when expressed by upper or lower (on or under), it is possible to include not only the upward direction but also the downward direction based on one element.

3 is a cross-sectional view of one embodiment of the light emitting device, and FIG. 4 is a detailed view illustrating the structure of the active layer of FIG.

The light emitting device 100 according to the embodiment includes a first conductive semiconductor layer including a first layer 122a and a second layer 122b, an active layer 124, a second conductive semiconductor layer 126, A transmissive conductive layer 140, and a first electrode 162 and a second electrode 166.

The light emitting structure includes the first conductive semiconductor layer, the active layer 124, and the second conductive semiconductor layer 126. The first conductive semiconductor layer may include a first conductive semiconductor layer such as sapphire 122a may be used as the substrate.

The first conductive semiconductor layer may be formed of a compound semiconductor such as Group III-V or Group II-VI, and may be doped with a first conductive dopant. The first conductive semiconductor layer may be a semiconductor material having a composition formula of Al _x In _y Ga _(1-xy) N (0? X? 1, 0? _Y? 1, 0? _X + y? InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the first conductivity type semiconductor layer is an n-type semiconductor layer, the first conductivity type dopant may include n-type dopants such as Si, Ge, Sn, Se, and Te.

The second layer 122b may be grown after the growth of the first layer 122a. The second layer 122b may be doped with a first conductivity type dopant, for example, silicon (Si) at a high concentration, for example, doped to 1 x 10 ¹⁹ / cm ³ or more. And, a second layer (122b) may be in the thickness (t ₁₎ 3 micrometers to 10 micrometers.

The active layer 124 is disposed between the first layer 122b and the second conductivity type semiconductor layer 126 and has a single well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW) , A quantum dot structure, or a quantum well structure, and may be a multiple quantum well structure in particular.

InGaN / InGaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and AlGaN / AlGaN / InGaN / / AlGaAs, GaP (InGaP) / AlGaP, but is not limited thereto. In particular, it may be a pair structure of InGaN / GaN.

In the Figure 4, forming the active layer (MQW) of the multiple quantum well structure, the thickness (t ₃₎ of the two walls (QB) thickness of the quantum well (QW) than that (t ₂₎ of the can thicker. Both walls (QB) and quantum well (QW) is 10 pairs to 20 pairs can be arranged and, particularly, the thickness of the two walls (QB) (t ₂₎ is 40 angstroms smaller, the thickness of the quantum well (QW) (t ₃ ) may be greater than 40 ohms Strong.

For example, the thickness of the quantum well QW may be between 43 and 45 ohms, the thickness of the quantum wall QB may be between 34 and 37 ohms, and the final quantum wall QB may serve as an electron blocking layer So it can be placed at a thickness of 98 ohm Strong.

The active layer of the multiple quantum structure in the light emitting structure grown on the conventional sapphire substrate has the quantum well QW of about 32 ohm Strength and the quantum wall QB about 54 Ohm Strong and the last quantum wall QB ) Could be placed at a thickness of 80 ohms.

That is, in the case of the nitride based semiconductor layer grown on the conventional sapphire substrate, if the quality of the multiple quantum well of the InGaN / GaN structure is deteriorated and the crystallinity is weak and the thickness of the quantum well QW is too large, There was no. However, when the thickness of the quantum well QW is increased to not less than 40 angstroms in the case where the substrate is grown on the same substrate and the high concentration silicon is doped in the second layer 122b, the crystallinity can be sufficiently grown without deteriorating the crystallinity, The coupling of electrons and holes is sufficiently performed in the quantum well QW having a thickness larger than that of the conventional art, so that the light efficiency of the light emitting device can be improved.

The quantum well can be formed of a material having an energy band gap smaller than the energy band gap of the quantum wall.

The second conductive semiconductor layer 126 may be formed of a semiconductor compound. The second conductive semiconductor layer 126 may be formed of a compound semiconductor such as a Group III-V or a Group II-VI, and may be doped with a second conductive dopant. The second conductive semiconductor layer 126 may be a semiconductor material having a composition formula of In _x Al _y Ga _{1 -xy} N (0? X? 1, 0? _Y? 1, 0? _X + y? 1) For example, the second conductivity type semiconductor layer 326 may be made of Al _x Ga _(1-x) N. The second conductivity type semiconductor layer 326 may be formed of Al _x Ga _{y (1-x)} N.

When the second conductive semiconductor layer 126 is a p-type semiconductor layer, the second conductive dopant may be a p-type dopant such as Mg, Zn, Ca, Sr, or Ba. The second conductive semiconductor layer 126 may be formed as a single layer or a multilayer, but the present invention is not limited thereto.

Although not shown, an electron blocking layer may be disposed between the active layer 124 and the second conductive semiconductor layer 126. The electron blocking layer may have a superlattice structure. For example, the superlattice may include AlGaN doped with a second conductive dopant, and GaN having a different composition ratio of aluminum may be formed as a layer And a plurality of these may be alternately arranged.

When the second conductivity type semiconductor layer 126 is p-type GaN, the current injection characteristic may not be good from the second electrode 166. Therefore, the light-transmitting conductive layer 140 is disposed on the second conductivity type semiconductor layer 126 And the transmissive conductive layer 140 may be made of ITO (Indium Tin Oxide), for example.

The first electrode 162 is disposed on the second layer 122b that is mesa etched from the second conductive type semiconductor layer 126 to a part of the active layer 124 and the second layer 122b and is etched and exposed, A second electrode 166 may be disposed on layer 140.

The first electrode 162 and the second electrode 166 may include at least one of aluminum (Al), titanium (Ti), chrome (Cr), nickel (Ni), copper (Cu) Or a multi-layer structure.

Although not shown, a passivation layer may be disposed on a side surface of the exposed light emitting structure to protect and isolate the light emitting structure from foreign substances or the like.

In the light emitting device 100 according to the above-described embodiment, the light emitting structure 120 is grown on GaN, which is a bulk nitride semiconductor, by GaN or the like, which is a homogeneous material, so that the quality of the light emitting structure can be excellent.

Table 1 compares the quality of the light emitting device according to the embodiment with the light emitting device in which the nitride based semiconductor layer is grown on different kinds of substrates.

Board
Lattice parameter Biaxial Uniaxial Threading dislocation density (TDD) XRC Thermal conductivity (W / mK)
Ohms / sq (LEI)
a c Strain Stress (Mpa) Strain Stress (Mpa) (002) (102) Sapphire 3.1832 5.1892 -0.086% -169 + 0.063% +123 1 to 2 x 10 ⁸ 65 124 30 ~ 10 bulk GaN 3.1890 5.1847 + 0.097% +190 -0.024% -47 2 to 5 × 10 ⁶ 63 52 130 ~ 0.5

The light emitting device according to the embodiment is mainly grown using the c-plane of GaN as a substrate. The biaxial shows the strain and stress in the horizontal direction, and + indicates the compressive stress such as expansion due to tensile stress, etc. ≪ / RTI >

Fig. 5 is a diagram showing bowing of GaN grown on bulk-GaN together with a comparative example.

5, the horizontal axis represents the growth time of the nitride-based semiconductor layer, and the vertical axis represents the curvature of each layer. When the curvature is negative (-), it can be concave upward, and when the curvature is positive (+), it can be convex upward.

As shown in FIG. 5, when the nitride based semiconductor layer is grown on the sapphire (SAP) substrate and when the nitride based semiconductor layer is grown on the silicon (Si) substrate, the convex Direction, the quality of the nitride based semiconductor layer may deteriorate and the crystallinity may deteriorate.

6 is a diagram showing a comparison example and an operation voltage of the light emitting device according to the embodiment.

In the GaN grown on the sapphire (SAP), the thickness of the n-GaN corresponding to the second layer 122b in the above embodiment is set to 3 micrometers and the doping amount of silicon is set to 1 x 10 ¹⁹ pieces / cm ³ In the case where the thickness of GaN grown on GaN is set to 3 micrometers and 4 micrometers, respectively, and the doping amount of silicon is set to 1 x 10 ¹⁹ atoms / cm ³ , the operating voltage at 100 A / cm ² .

7 is a view showing various examples of the electrode arrangement of the light emitting device according to the embodiment.

The design represents the design of the electrodes, particularly the first electrode, and the area indicated by the white color on the black background represents the arrangement of the first electrodes. As shown in FIG. 7, VF3 to VF6 represent operating voltages according to the respective currents. In the four electrode designs, the change in the operating voltage is not significant. The first layer 122a ) And the second layer 122b doped with silicon at a high concentration, current spreading in the first conductivity type semiconductor layer 122 is excellent.

The above-described light emitting device is advantageous for growing InGaN that is a quantum well (QW) because the nitride based semiconductor layer is grown on the same kind of substrate and the quality is excellent and the compressive strain is reduced. GaN has the same electric conductivity as the light emitting structure, thereby improving the current spreading and improving the thermal conductivity.

8 is a view showing an embodiment of a light emitting device package in which a light emitting device is disposed.

In the light emitting device package according to the embodiment, the light emitting device may be flip-bonded.

The light emitting device package 200 includes a package body 210, a first lead frame 222 and a second lead frame 226 mounted on the package body 210, A light emitting device 100 according to the above embodiments electrically connected to the frame 222 and the second lead frame 226 and a molding part (not shown) surrounding and protecting the light emitting device 100.

The package body 210 may be formed of a silicon material, a synthetic resin material, or a metal material. When the package body 210 is made of a conductive material such as a metal material, although not shown, an insulating layer is coated on the surface of the package body 210 to electrically short circuit the first and second lead frames 222 and 226 .

The first lead frame 222 and the second lead frame 226 are electrically separated from each other and supply current to the light emitting element 100 through a conductive material such as solder 242 and 246. [ The first lead frame 222 and the second lead frame 226 may reflect the light generated by the light emitting device 100 to increase the light efficiency. It may be discharged to the outside.

The molding part can surround and protect the light emitting device 100. The phosphor may include a phosphor to change the wavelength of light emitted from the light emitting device 100. The phosphor may be a YAG-based phosphor, a Nitride-based phosphor, or a silicate-based phosphor.

The light of the first wavelength range emitted from the light emitting device 100 is excited by the phosphor to be converted into the light of the second wavelength range and the light of the second wavelength range passes through the lens (not shown) can be changed.

The light emitting device package 200 may be mounted on one or a plurality of light emitting devices according to the above-described embodiments, but the present invention is not limited thereto.

7, a pattern is formed on the upper surface of the first layer of the flip-bonded horizontal light emitting device, so that light extraction efficiency of light emitted from the light emitting device can be improved. 7, the upper surface of the first layer may correspond to the lower surface of the first layer 122a of the light emitting device 100 in FIG. 3 and the like.

In the embodiment of FIG. 3, a part of the light emitting structure is mesa-etched to dispose the first electrode 162, but the first electrode may be disposed on the lower surface of the first layer 122a to be used as a vertical light emitting device .

The light emitting device to the light emitting device package described above can be used as a light source of an illumination system, for example, a backlight unit of a video display device and a lighting device.

When used as a backlight unit of an image display apparatus, it can be used as a backlight unit of an edge type or as a direct-type backlight unit, and can be used as a light source of a register or a ball type when used in a lighting apparatus.

It can also be used as a light source for a vehicle headlamp and a projector.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100: light emitting device 120: light emitting structure
122a: first layer 122b: second layer
124: active layer 126: second conductivity type semiconductor layer
140: translucent conductive layer 162: first electrode
166: second electrode 200: light emitting device package
210: substrates 222 and 226: first and second lead frames
242, 246: Solder

Claims (11)

A first conductive semiconductor layer including a first layer and a second layer;
An active layer of a multiple quantum well structure disposed on the first conductive type semiconductor layer;
A second conductive semiconductor layer disposed on the active layer; And
A first electrode and a second electrode which are respectively disposed on the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,
Wherein a thickness of the quantum well is larger than a thickness of the quantum well. The method according to claim 1,
Wherein the first layer and the second layer are doped with a first conductive dopant. The method according to claim 1,
And the second layer is doped with a first conductivity type dopant of 1 x 10 ¹⁹ / cm ³ or more. The method of claim 3,
Wherein the first conductive dopant is silicon. The method according to claim 1,
And the second layer has a thickness of 3 micrometers to 10 micrometers. The method according to claim 1,
Wherein the quantum well and the quantum well are arranged in 10 pairs to 20 pairs. The method according to claim 1,
Wherein the thickness of the quantum well is greater than 40 ohms. The method according to claim 1,
Wherein the thickness of the quantum wall is less than 40 ohms. The method according to claim 1,
Wherein the multiple quantum well is made of InGaN / GaN. The method according to claim 1,
And a pattern is formed on a bottom surface of the first layer. A package body;
A first lead frame and a second lead frame disposed on the package body and electrically separated from each other; And
The light emitting device package according to any one of claims 1 to 10, wherein the light emitting element is flip-bonded to the first lead frame and the second lead frame.

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