WO2020038744A1

WO2020038744A1 - Optoelectronic semiconductor device comprising a transparent substrate and a carrier

Info

Publication number: WO2020038744A1
Application number: PCT/EP2019/071501
Authority: WO
Inventors: Tansen Varghese
Original assignee: Osram Oled Gmbh
Priority date: 2018-08-24
Filing date: 2019-08-09
Publication date: 2020-02-27

Abstract

An optoelectronic semiconductor device (10) comprising a transparent substrate (100), a light emitting structure (110) arranged over a first main surface (101) of the transparent substrate (100), and a carrier (120) arranged at a second main surface (102) of the transparent substrate (100), remote from the first main surface (101). An interface (125) or an interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned so that the light transmitted via the transparent substrate (100) is redirected towards the sidewalls (104) of the transparent substrate (100).

Description

OPTOELECTRONIC SEMICONDUCTOR DEVICE COMPRISING A TRANSPARENT

SUBSTRATE AND A CARRIER

BACKGROUND

This application claims the priority of German patent application DE 10 2018 120 715.8, the entire contents of which is hereby incorporated by reference.

Some kinds of light emitting diodes (LEDs) comprise light emitting semiconducting layers over a transparent substrate. Generally, part of the electromagnetic radiation generated by the semiconductor layers is emitted via side faces of the transparent substrate. These kinds of LEDs are also referred to as volume emitters.

Generally, concepts are sought, by which the outcoupling efficiency of the optoelectronic semiconductor device may be increased .

It is an object of the present invention to provide an improved optoelectronic semiconductor device.

According to embodiments, the above object is achieved by the claimed matter according to the independent claims. Preferred embodiments are defined in the dependent claims.

SUMMARY

According to embodiments, an optoelectronic semiconductor device comprises a transparent substrate, a light emitting structure arranged over a first main surface of the transparent substrate, and a carrier arranged at a second main surface of the transparent substrate, remote from the first main surface. An interface or an interface layer between the carrier and the transparent substrate is patterned to at least one periodic pattern so that light transmitted via the transparent substrate is diffracted towards the sidewalls of the transparent substrate.

For example, the light emitting structure may comprise a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a first contact pad. The first semiconductor layer may be arranged between the second semiconductor layer and the transparent substrate. The first contact pad may be directly adjacent to the first semiconductor layer.

For example, the second main surface of the transparent substrate may be patterned. According to further embodiments, a first main surface of the carrier may be patterned. The first main surface is arranged on a side of the transparent substrate .

According to embodiments, the optoelectronic semiconductor device may further comprise an interlayer between the transparent substrate and the carrier. For example, the interlayer may be patterned. According to embodiments, the interlayer is transparent. For example, the interlayer may comprise a polymer or a resin, for example, silicone. By way of example, a material of the interface layer may have a refractive index which is different from the refractive index of the substrate.

According to further embodiments, the interlayer comprises a reflective material, e.g. a conductive material. By way of example the second main surface of the transparent substrate may be patterned and the interface layer comprises a metal layer coated over the patterned second main surface of the transparent substrate. The metal layer may or may not have a planar surface remote from the transparent substrate.

According to further embodiments, the second main surface of the transparent substrate is patterned. The interface layer may comprise a nanoparticle or microparticle metal die bonding paste that is coated over the patterned second main surface of the transparent substrate.

According to still further embodiments, the second main surface of the transparent substrate is patterned. The interface layer may comprise a dielectric layer formed over the second main surface and may or may not have a planar surface on a side remote from the transparent substrate.

According to still further embodiments, the second main surface of the transparent substrate is patterned. The interface layer comprises a polymer that is embossed by the second main surface.

For example, the interface or the interface layer between the carrier and the transparent substrate may be patterned to a pattern comprising more than 4 protruding portions or holes. For example, the interface or the interface layer between the carrier and the transparent substrate may be patterned to a pattern comprising protruding portions having a diameter larger than half a wavelength of emitted light in the substrate. According to further embodiments, the interface or the interface layer between the carrier and the transparent substrate may be patterned to a pattern comprising holes having a diameter larger than half a wavelength of emitted light in the substrate, According to still further embodiments, the interface or the interface layer between the carrier and the transparent substrate may be patterned to a pattern comprising ridges having a pitch larger than a wavelength of emitted light in the substrate. According to embodiments, the interface or the interface layer between the carrier and the transparent substrate is patterned to a pattern comprising ridges, wherein the ridges may have orientations that depend on the position of the ridge.

For example, the interface or the interface layer between the carrier and the transparent substrate may be patterned to a first pattern at a first position and to a second pattern at a second position. The first pattern is different from the second pattern.

According to a further example the interface or the interface layer between the carrier and the transparent substrate is patterned to at least one periodic pattern so that light transmitted via the transparent substrate at different positions is diffracted towards different sidewalls of the transparent substrate.

According to embodiments, the interface or the interface layer between the carrier and the transparent substrate is patterned to a patterned portion having protruding portions, sidewalls of the protruding portions intersecting the second main surface at an angle different from 90°.

By way of example, the light emitting structure may comprise a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type, the first semiconductor layer being arranged between the second semiconductor layer and the transparent substrate. According to embodiments, an interface or an interface layer between the first semiconductor layer and the transparent substrate is patterned .

For example, the interface or the interface layer between the carrier and the transparent substrate may be patterned so as to enable a reflection or re-direction of light emitted by the light emitting structure.

According to embodiments, the interface or the interface layer between the carrier and the transparent substrate may be patterned so as to enable a reflection or re-direction of light emitted by the light emitting structure at an angle of less than 45°, being measured between the reflected light and a plane of the interface. For example, the interface or the interface layer between the carrier and the transparent substrate is patterned so as to enable a reflection or re direction of light emitted by the light emitting structure towards sidewalls of the transparent substrate. According to embodiments, the interface or the interface layer between the carrier and the transparent substrate may be patterned so as to enable a reflection or re-direction of light emitted by the light emitting structure towards sidewalls of the transparent substrate at an angle within a cone of transmission of the sidewall .

According to further embodiments, an optoelectronic semiconductor device comprises a transparent substrate, a light emitting structure arranged over a first main surface of the transparent substrate, and a carrier arranged at a second main surface of the transparent substrate, remote from the first main surface. An interface or an interface layer between the carrier and the transparent substrate is patterned. The light emitting structure comprises a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a first contact pad. The first semiconductor layer is arranged between the second semiconductor layer and the transparent substrate. The first contact pad is directly adjacent to the first semiconductor layer .

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.

Fig. 1 shows a schematic cross-sectional view of an optoelectronic semiconductor device according to embodiments.

Fig. 2A shows details of an example of an optoelectronic semiconductor device.

Fig. 2B shows details of an optoelectronic semiconductor device according to further embodiments.

Fig. 2C shows details of components of an optoelectronic semiconductor device according to further embodiments. Fig. 3A shows a perspective view of an element of an optoelectronic semiconductor device according to embodiments

Fig. 3B shows a perspective view of a component of an optoelectronic semiconductor device according to further embodiments .

Fig. 3C shows a perspective view of a component of an optoelectronic semiconductor device according to further embodiments .

Fig. 4 shows a schematic cross-sectional view of an optoelectronic semiconductor device according to further embodiments .

DETAILED DESCRIPTION

In the following detailed description reference is made to the accompanying drawings, which form a part hereof and in which are illustrated by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "over", "on", "above", "leading", "trailing" etc. is used with reference to the orientation of the Figures being described. Since components of embodiments of the invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope defined by the claims . The description of the embodiments is not limiting. In particular, elements of the embodiments described hereinafter may be combined with elements of different embodiments.

The semiconductor materials used in the context of the present specification may be particularly suitable for generation of electromagnetic radiation. Examples comprise nitride-compound semiconductors, by which e.g. ultraviolet or blue light or longer wavelength light may be generated, such as GaN, InGaN, AIN, AlGaN, AlGalnN, phosphide-compound semiconductors, by which e.g. green or longer wavelength light may be generated such as GaAsP, AlGalnP, GaP, AlGaP, as well as further semiconductor materials including AlGaAs, GaSb, InAs, SiC, ZnSSe, GaAs, ZnO, Ga₂0₃, diamond, hexagonal BN und combinations of these materials. The stoichiometric ratio of the compound semiconductor materials may vary. In the context of the present specification, the term "semiconductor" further encompasses organic semiconductor materials.

The terms "lateral" and "horizontal" as used in this specification intends to describe an orientation parallel to a first surface of a substrate or semiconductor body. This can be for instance the surface of a wafer or a die.

The term "vertical" as used in this specification intends to describe an orientation which is arranged perpendicular to the first surface of a substrate or semiconductor body.

As used herein, the terms "having", "containing", "including", "comprising" and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles "a", "an" and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise. As employed in this specification, the terms "coupled" and/or "electrically coupled" are not meant to mean that the elements must be directly coupled together - intervening elements may be provided between the "coupled" or "electrically coupled" elements. The term "electrically connected" intends to describe a low-ohmic electric connection between the elements electrically connected together.

The term "electrically connected" further comprises tunneling contacts between connected elements.

Fig. 1 shows a cross-sectional view of an optoelectronic semiconductor device 10 according to embodiments. As is shown in Fig. 1, an optoelectronic semiconductor device 10 comprises a transparent substrate 100 and a light emitting structure 110 arranged over a first main surface 101 of the transparent substrate 100. The optoelectronic semiconductor device further comprises a carrier 120 at a second main surface 102 of the transparent substrate, remote from the first main surface 101. An interface or an interface layer between the carrier 120 and the transparent substrate 100 is patterned. The light emitting structure 110 may for example comprise a first semiconductor layer 115 of a first conductivity type, e.g. p-type and a second semiconductor layer 118 of a second conductivity type, e.g. n-type. An active region 117 may be arranged between the first semiconductor layer 115 and the second semiconductor layer 118. By way of example, the active region 117 may comprise a pn junction, a double hetero structure, a single quantum well structure or a multiple quantum well structure for generating electromagnetic radiation. The term "quantum well" does not relate to any specific dimension of the quantization. The term "quantum well structure" is intended to encompass inter alia quantum wells, quantum wires, quantum dots as well as any combination of these layers. The first and second semiconductor layers 115, 118 may comprise different or identical materials. The above-mentioned first and second semiconductor layers may comprise several sub-layers, e.g. having different compositions and/or doping concentrations. The light emitting structure may further comprise other conductive and insulating layers of different materials such as metals, transparent conductive oxides, polymers, and dielectrics. For example, these layers may together enable and optimize electricity injection and light emission.

The light emitting structure 110 is arranged over a transparent substrate. The substrate may e.g. be made of sapphire, SiC, GaP or glass. The specific composition of the transparent substrate 100 may depend on the wavelength of the emitted light. A thickness of the transparent substrate may e.g. be larger than 10 ym. For example, the thickness of the transparent substrate may be smaller than 1 mm. A thickness of the first and second semiconductor layers may be larger than 0.5 ym. For example, the thickness may be smaller than 10 ym. Specific semiconductor materials of the first and second semiconductor layers may comprise In_xGa_yAli-_x-yP, In_xGa_yAsi-_x-yP, Al_xGai__xAs, In_xGai__xN and Al_xIn_yGai-_x-yN (0£x£l, 0£y£l) as well as further semiconductor materials such as ZnSSe, GaSb, and InAs- based materials. The stoichiometric ratio of the compound semiconductor materials may vary. The material of the transparent substrate 100 may be insulating or may be a semiconductor material that does not form part of the light emitting structure 110. For example, if the transparent substrate 100 comprises a semiconductor material, this semiconductor material may be different from a material of the first semiconductor layer 115 and of the second semiconductor layer 118. The carrier 120 may be made of a reflecting material. For example, the carrier 120 may be made of a metal or another reflective material. According to further embodiments, the carrier 120 may be made of a base material and may be coated with a reflecting material. The carrier may also comprise or be made of a transparent material.

An interface 125 or an interface layer is patterned. Accordingly, as illustrated in Fig. 1, a patterned portion 140 is arranged between the transparent substrate 100 and the carrier 120.

For example, the patterned portion 140 may comprise a periodic pattern of protruding portions or holes, e.g. a grating. For example, the grating may be a phase grating or an amplitude grating. For example, the periodic pattern may extend in one or in two directions. For example, as shown in Fig. 1, the pattern may be formed so that the pattern is visible in the depicted cross-sectional plane. Electromagnetic radiation 20 which is generated by the light emitting structure 110 is outcoupled via main surfaces of the light emitting structure as well as via sidewalls of the light emitting structure and sidewalls 104 of the transparent substrate 100. Due to the presence of the patterned portion 140, light which is transmitted via the transparent substrate 100 may be obliquely reflected or diffracted by the patterned portion 140. For example, diffracted light of the first diffraction order may be deflected in a direction having a shallow angle with respect to the first main surface 121 of the carrier. In a corresponding manner reflected light may be reflected in a direction having a shallow angle with respect to the first main surface 121 of the carrier. The term "shallow angle" is intended to mean an angle between the diffracted light beam and a plane of the interface to be less than 45°. For example, the angle may be less than 40° or even less than 20°. Due to the fact that the light reflected at the second main surface of the transparent substrate 100 is diffracted at a small angle a, a large proportion of light will outcouple from the transparent substrate 100 without being totally internally reflected by the interface between the sidewall 104 of the transparent substrate 100 and the adjacent medium, e.g. air, a lower index encapsulation or a lens material. In more detail, the light may be reflected at the second main surface of the transparent substrate 100 at an angle within a cone of transmission of the sidewalls 104. Fig. 1 further illustrates a cone 105 of transmission or escape cone. The opening angle (2g) of the cone 105 is a function of the ratio of refractive indices between the transparent substrate 100 and the adjacent medium. Reflected light beams incident on the sidewall 104 at an angle d smaller than g will be transmitted through the interface, wherein d is measured with respect to the normal of the sidewall 104 as is illustrated in Fig. 1. Light beams incident on the sidewall 104 at an angle d larger than g will be totally internally reflected by the sidewall 104.

As a consequence of being transmitted by the sidewall 104, the electromagnetic radiation 20 leaves the optoelectronic semiconductor device without being redirected to the light emitting structure, within the optoelectronic semiconductor device. As a consequence, less absorption by the metallization layers or other absorptive components of the optoelectronic device will occur. Hence, the ratio of outcoupled light to generated light may be increased. As a further consequence, the thickness of the transparent substrate may be reduced without decreasing the outcoupling efficiency. As a result of the reduced thickness of the transparent substrate, heat may be more efficiently dissipated thus increasing efficiency. Further, due to the reduced amount of absorption by the light emitting structure 110 or other absorptive components of the optoelectronic device, less heat is generated thus increasing the efficiency of the optoelectronic device.

Since the total internal reflections may be reduced due to the presence of the patterned portion, a substrate material of the transparent substrate 100 may have a higher refractive index. As a result light outcoupling from the light emitting structure to the transparent substrate may be improved, e.g. by reducing the total internal reflection between the light emitting structure and the transparent substrate. As a further result, the efficiency may be increased. Further, due to the patterning of the interface or an interface layer, substrates of a high refractive index may be employed. As an example of a high index substrate, SiC which has a high thermal conductivity may be employed. As a result, efficiency losses due to temperature rise may be additionally reduced. Finally, by using a patterned interface material to reflect and redirect the light incident on the bottom of the transparent substrate, reflection may be caused without using a reflective metal. As a further result, absorption of electromagnetic radiation by the reflective metal may be avoided.

The optoelectronic semiconductor device may further comprise a first contact pad 155 for electrically contacting the first semiconductor layer 115 and a second contact pad 158 for electrically connecting to the second semiconductor layer 118. As is readily to be appreciated, the specific composition and structure of the light emitting structure and its contacts may deviate from the structure shown in Fig. 1. In more detail, the specific patterned interface or interface layer between the transparent substrate 100 and the carrier 120 determines the special radiation characteristic of the semiconductor device .

The feature "an interface or an interface layer between the carrier and the transparent substrate is patterned" may be implemented in various manners. For example, as is shown in Fig. 2A, the second main surface 102 of the transparent substrate 100 may be patterned. The specific shape of possible patterns will be explained later. According to embodiments shown in Fig. 2A, the patterned portion 140 is formed in contact with the transparent substrate 100. For example, the carrier 120 may not be patterned but may have a planar and smooth first main surface 121. When the transparent substrate 100 comes into contact with the carrier 120, the patterned portion 140 may protrude into the carrier 120. The carrier may be made of a reflecting or a transparent material.

According to further embodiments, the patterned portion 140 may not protrude into the carrier 120 and air may be arranged between the first main surface 121 of the carrier and the patterned portion 140. According to further embodiments, an interlayer 130 may be arranged between the transparent substrate 100 and the carrier 120. For example, the interlayer 130 may comprise a transparent smooth material into which the patterned portion 140 may protrude. For example, the interlayer 130 may be made of a reflecting material, or a transparent polymer or resin, for example silicone, having a refractive index which is different from the refractive index of the substrate 100. For example, the interlayer 130 may be patterned using an embossing method. For example, the difference between the refractive indices may be made as large as possible. According to further embodiments, the interlayer 130 may comprise a metal layer that is coated over the patterned substrate. By way of example, the metal layer may be planarized or may not be planarized before bonding the transparent substrate to the carrier. As a result, a surface of the metal layer remote from the substrate may be planar. According to further examples, the interlayer 130 may comprise a nanoparticle or microparticle metal die bonding paste (such as, for example, silver paste) that is coated over the patterned substrate. For example, the interlayer 130 may comprise any combination of nanoparticle or microparticle metal die bonding paste along with or without the metal layer as mentioned above.

According to further examples, the interlayer 130 may comprise a dielectric which is deposited over the substrate and and which may or may not be planarized before bonding the transparent substrate to the carrier. Accordingly, a surface of the dielectric may be planar on a side remote from the transparent substrate. When the interlayer 130 comprises a dielectric, the refractive index of the dielectric is different from the refractive index of the transparent substrate 100. For example, it may be desirable to increase the difference between the refractive indices as much as possible. The dielectric or polymer is transparent. For example, if a reflecting metal or metal paste is not in contact with the patterned substrate, the interlayer 130 material may be as transparent as possible.

The pattern 140 may e.g. be formed by patterning the substrate 100. According to further embodiments, a material layer, e.g. of a conductive, an insulating or a semiconductor material, may be directly adjacent to the substrate and may be patterned. As is further shown in Fig. 2A, for example, the patterned portion 140 has protruding portions 135. At least one sidewall of the protruding portions 135 intersects the (imaginary) second main surface 102 of the transparent substrate at an angle smaller than 90°. For example, the angle b and the distance d between adjacent protruding portions 135 may be determined in dependence from the wavelength of the electromagnetic radiation and in dependence of the angle of the first diffraction order of diffracted light.

According to further embodiments, as is shown in Fig. 2B, the first main surface 121 of the carrier 120 may be patterned to form a patterned portion 140. For example, the material of the carrier 120 itself may be patterned. According to further embodiments, a material in direct contact with the carrier 120 may be patterned. Similar to the carrier 120 of embodiments explained with reference to Fig. 2A, the transparent substrate 100 may not be patterned or may be correspondingly patterned. Moreover, an interlayer 130 may be arranged between the carrier and the transparent substrate 100. For example, the interlayer 130 may be made of a transparent polymer or resin, for example silicone. In this case, the patterned portion 140 may protrude in the interlayer 130.. According to embodiments described with reference to Fig. 2B, the interlayer 130 has a refractive index which is close to the refractive index of the transparent substrate 100. In particular, it is desirable to minimize a difference between the refractive index of the transparent substrate 100 and the refractive index of the interlayer 130 as much as possible. Further, it is desirable to increase the transparency of the interlayer 130 as much as possible. For example, the material of the interlayer 130 may be deposited over the patterned carrier 120 and may be subsequently planarized. According to further embodiments, the material of the interlayer 130 may be deposited over the transparent substrate 100 and may be subsequently patterned. According to further embodiments, as is shown in Fig. 2C, the interlayer 130 may be patterned. As is shown in Fig. 2C, both surfaces of the interlayer 130 may be patterned. As is clearly to be understood, one of the surfaces may as well be patterned whereas the other surface of the interlayer is not patterned. According to further embodiments, a first surface of the interlayer may be patterned according to a first pattern, and a second surface of the interlayer may be patterned according to a second pattern. The first pattern may be different from the second pattern. For example, the interlayer may comprise a conductive material e.g. a metal. For example, the patterned portion 140 may comprise a grating. Accordingly, a grating of a conductive material may be arranged between the carrier 120 and the transparent substrate. The grating may be one-or two- dimensional grating as will be explained below.

According to embodiments, the patterned portion 140 may be formed using an embossing method or any other method suitable for forming a grating.

Fig. 3A shows a perspective view of a patterned portion 140 according to embodiments. The patterned portion 140 may be arranged at a surface of the transparent substrate 100, at a surface of the carrier 120 and at a surface of the interlayer 130. For example, the patterned portion 140 may comprise a grating of protruding portions 135 or ridges 137. The ridges 137 may be formed along a first direction, e.g. the x- direction, whereas no pattern is formed along a second direction, e.g. the y-direction. The ridges 137 may be arranged at a constant pitch. According to further embodiments, the ridges 137 may not be arranged at a constant pitch. The ridges 137 or a part of the ridges 137 may be identical in shape. According to further embodiments, some of the ridges 137 may be different in shape. The ridge cross- sections may be rectangular, square-shaped, pyramidal, squewed pyramidal (blazed grating) or have other shapes such as hemispherical or semispherical . The ridges may have different orientations on different areas of the chip, to redirect light to different sides of the chips, for example, to the closest sides. The ridges can also be patterned as concentric circles or ellipses, centered at the center of the chip, depending on the shape of the chip (square or rectangular, for example) . Accordingly, the interface 125 or the interface layer 130 between the carrier 120 and the transparent substrate 100 may be patterned to a pattern comprising ridges, wherein the ridges may have orientations that depend on the position of the ridge. In more detail, in a first position, the ridges may have a first orientation. Further, in a second position, the ridges may have a second orientation. The first orientation may be different from the second orientation. The first orientation may be selected so that light is directed to the sidewall having the shortest distance to the first position. The second orientation may be selected so that light is directed to the sidewall having the shortest distance to the second position.

According to a further implementation, the interface 125 or the interface layer 130 between the carrier 120 and the transparent substrate 100 may be patterned to a first pattern at a first position and to a second pattern at a second position, the first pattern being different from the second pattern. In a corresponding manner as has been discussed above, the first pattern may be selected so that light is directed to the sidewall having the shortest distance to the first position. The second pattern may be selected so that light is directed to the sidewall having the shortest distance to the second position. According to a further implementation, the interface 125 or the interface layer 130 between the carrier 120 and the transparent substrate 100 is patterned to at least one periodic pattern so that light transmitted via the transparent substrate 100 at different positions is diffracted towards different sidewalls 104 of the transparent substrate 100.

A rectangular cross-section may have, for example, a pitch of slightly more than the wavelength of light in the transparent substrate. In the context of the present specification, the term "wavelength of light in a material" is intended to mean the wavelength in air divided by the refractive index of the material, e.g. the substrate. The width in this case could be half the pitch, and the minimum height could be also about the same as half the wavelength.

Fig. 3B shows a further example of the patterned portion 140 which may be arranged at a surface of the transparent substrate, at a surface of the carrier or at a surface of the interlayer 130. As illustrated in Fig. 3B, a plurality of holes 139 may be formed in the transparent substrate, the carrier 120 or the interlayer 130. For example, the holes 139 may form a regular periodic pattern. The holes may be identical in shape with a diameter larger than about half the wavelength in the material, e.g. the substrate. The holes may also have two or more diameters and pitches, e.g. in different directions .

According to embodiments illustrated with reference to Fig. 3C, the plurality of protruding portions 135 may be arranged at a main surface of the transparent substrate, at a surface of the carrier 120 or at a surface of the interlayer 130. The protruding portions may be formed at a regular pattern to form a periodic structure. The protruding portions 135 may be identical in shape, with a diameter larger than about half the wavelength in the material, e.g. the substrate. The protrusions may also have two or more diameters and pitches, e.g. in different directions. The protruding portions 135 may, for example, have a shape of columns, e.g. having a circular, rectangular, oval or arbitrarily shaped cross- section. They may also have a cone-like or a pyramidal or further suitable shape.

The patterning of the interface or the interface layer may be selected depending on the angular distribution of the light incident on the interface of the transparent substrate and the carrier. This may depend on the features of the light emitting structure such as - among others - topography, the wavelengths involved, and the refractive indices of the materials in the whole structure. The patterning of the interface or the interface layer may be selected in order to redirect a large proportion of light to the sides of the transparent substrate. The patterning on different areas of the chip can be different, to redirect light to different sides of the chip, for example, the closest side.

Fig. 4 shows a cross-sectional view of the semiconductor device 10 according to further embodiments. The semiconductor device 10 of Fig. 4 is similar to the semiconductor device shown in Fig. 1. Differing from embodiments of Fig. 1, an interface 142 between the light emitting structure 110, in particular, the first semiconductor layer 115, and the transparent substrate 100 is patterned. Thereby, the outcoupling efficiency from the first semiconductor layer 115 to the transparent substrate 100 may be improved. In a corresponding manner, the first main surface 119 of the second semiconductor layer 118 may be patterned. For example, the pattern of the first main surface 119 may be a non-periodic pattern. In a corresponding manner, the pattern of the patterned interface 142 between the light emitting structure 110 and the transparent substrate 100 may be non-periodic. Moreover, a first contact portion 151 may be arranged adjacent to the first semiconductor layer 115. For example, the first contact portion 151 may comprise a metal grid for electrically contacting the first semiconductor layer 115 to the first contact pad 155. In a corresponding manner, the second contact portion 153 may comprise a metal grid for electrically connecting the second contact pad 158 to the second semiconductor layer 118.

While embodiments of the invention have been described above, it is obvious that further embodiments may be implemented. For example, further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above. Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein .

LIST OF REFERENCES

10 optoelectronic semiconductor device

20 emitted electromagnetic radiation

100 transparent substrate

101 first main surface of transparent substrate

102 second main surface of transparent substrate

104 sidewall of transparent substrate

105 cone of transmission

110 light emitting structure

115 first semiconductor layer

117 active region

118 second semiconductor layer

119 first main surface of the second semiconductor layer

120 carrier

121 first main surface of carrier

125 interface between carrier and transparent substrate

130 interface layer

135 protruding portion

137 ridge

139 hole

140 patterned portion

142 patterned interface

151 first contact portion

153 second contact portion

155 first contact pad

158 second contact pad

Claims

1. An optoelectronic semiconductor device (10) comprising:

a transparent substrate (100);

a light emitting structure (110) arranged over a first main surface (101) of the transparent substrate (100); and

a carrier (120) arranged at a second main surface (102) of the transparent substrate (100), remote from the first main surface (101) ,

wherein an interface (125) or an interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to at least one periodic pattern so that light transmitted via the transparent substrate (100) is diffracted towards sidewalls (104) of the transparent substrate (100).

2. The optoelectronic semiconductor device (10) according to claim 1, wherein the light emitting structure (110) comprises a first semiconductor layer (115) of a first conductivity type, a second semiconductor layer (118) of a second conductivity type, and a first contact pad (155), the first semiconductor layer (115) being arranged between the second semiconductor layer (118) and the transparent substrate (100) and the first contact pad (155) being directly adjacent to the first semiconductor layer (115) .

3. The optoelectronic semiconductor device (10) according to claim 1 or 2, wherein the second main surface (102) of the transparent substrate (100) is patterned.

4. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein a first main surface (121) of the carrier (120) is patterned, the first main surface (121) being arranged on a side of the transparent substrate (100) . 5. The optoelectronic semiconductor device (10) according to any of the preceding claims, further comprising an interface layer (130) between the transparent substrate (100) and the carrier (120) .

6. The optoelectronic semiconductor device (10) according to claim 5, wherein the interface layer (130) is patterned.

7. The optoelectronic semiconductor device (10) according to claim 5 or 6, wherein the interface layer (130) comprises a transparent material.

8. The optoelectronic semiconductor device (10) according to claim 6 or 7, wherein a material of the interface layer (130) has a refractive index which is different from the refractive index of the substrate (100) .

9. The optoelectronic semiconductor device (10) according to claim 6, wherein the interface layer (130) comprises a reflective material.

10. The optoelectronic semiconductor device (10) according to claim 9, wherein the second main surface (102) of the transparent substrate (100) is patterned and the interface layer (130) comprises a metal layer coated over the patterned second main surface (102) of the transparent substrate (100) .

11. The optoelectronic semiconductor device (10) according to claim 10, wherein the metal layer has a planar surface remote from the transparent substrate (100) .

12. The optoelectronic semiconductor device (10) according to any of claims 9 to 11, wherein the second main surface (102) of the transparent substrate (100) is patterned and the interface layer (130) comprises a nanoparticle or microparticle metal die bonding paste that is coated over the patterned second main surface (102) of the transparent substrate (100) .

13. The optoelectronic semiconductor device (10) according to claim 7, wherein the second main surface (102) of the transparent substrate (100) is patterned and the interface layer (130) comprises a dielectric layer formed over the second main surface (102) .

14. The optoelectronic semiconductor device (10) according to claim 13, wherein the dielectric layer has a planar surface on a side remote from the transparent substrate (100) .

15. The optoelectronic semiconductor device (10) according to claim 7, wherein the second main surface (102) of the transparent substrate (100) is patterned and the interface layer (130) comprises a polymer that is embossed by the second main surface (102) .

16. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a pattern comprising more than 4 protruding portions or holes.

17. The optoelectronic semiconductor device (10) according to claim 16, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a pattern comprising protruding portions having a diameter larger than half a wavelength of emitted light in the substrate. 18. The optoelectronic semiconductor device (10) according to claim 16, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a pattern comprising holes having a diameter larger than half a wavelength of emitted light in the substrate.

19. The optoelectronic semiconductor device (10) according to claim 16, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a pattern comprising ridges having a pitch larger than a wavelength of emitted light in the substrate.

20. The optoelectronic semiconductor device (10) according to claim 16, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a pattern comprising ridges, wherein the ridges may have orientations that depend on the position of the ridge.

21. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a patterned portion (140) having protruding portions (135), sidewalls of the protruding portions (135) intersecting the second main surface at an angle different from 90°.

22. The optoelectronic semiconductor device (10) according to any of the preceding claims wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to a first pattern at a first position and to a second pattern at a second position, the first pattern being different from the second pattern.

23. The optoelectronic semiconductor device (10) according to any of the preceding claims wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned to at least one periodic pattern so that light transmitted via the transparent substrate (100) at different positions is diffracted towards different sidewalls (104) of the transparent substrate (100).

24. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the light emitting structure (110) comprises a first semiconductor layer (115) of a first conductivity type and a second semiconductor layer (118) of a second conductivity type, the first semiconductor layer (115) being arranged between the second semiconductor layer (118) and the transparent substrate (100) .

25. The optoelectronic semiconductor device (10) according to claim 24, wherein an interface (125) or an interface layer (130) between the first semiconductor layer (115) and the transparent substrate (100) is patterned.

26. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned so as to enable a re direction of radiation (20) emitted by the light emitting structure (110) .

27. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned so as to enable a re direction of radiation (20) emitted by the light emitting structure (110) at an angle of less than 45°, being measured between the reflected radiation (20) and a plane of the interface.

28. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the interface (125) or the interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned so as to enable a re direction of radiation (20) emitted by the light emitting structure (110) towards sidewalls of the transparent substrate

(100) at an angle within a cone (105) of transmission of the sidewall (104) .

29. An optoelectronic semiconductor device (10) comprising:

a transparent substrate (100);

wherein an interface (125) or an interface layer (130) between the carrier (120) and the transparent substrate (100) is patterned, and

the light emitting structure (110) comprises a first semiconductor layer (115) of a first conductivity type, a second semiconductor layer (118) of a second conductivity type, and a first contact pad (155), the first semiconductor layer (115) being arranged between the second semiconductor layer (118) and the transparent substrate (100) and the first contact pad (155) being directly adjacent to the first semiconductor layer (115).