Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/81—Bodies
  • H10H20/819—Bodies characterised by their shape, e.g. curved or truncated substrates
  • H10H20/82—Roughened surfaces, e.g. at the interface between epitaxial layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/84—Coatings, e.g. passivation layers or antireflective coatings
  • H10H20/841—Reflective coatings, e.g. dielectric Bragg reflectors

Definitions

• the radiation-emitting body comprises a layer sequence with an active layer for generating electromagnetic radiation, with a reflection layer which reflects the generated radiation and with at least one
• a method for producing a radiation-emitting body is specified.
• a layer sequence is formed on a substrate with an active layer for generating electromagnetic radiation.
• the publication DE 10 2007 002 416 A1 describes a radiation-emitting body and a method for producing a radiation-emitting body.
• the active layer has a roughening on an interface directed towards the reflection layer and the reflection layer is substantially planar at an interface directed towards the active layer.
• a planar surface is to be understood as meaning a smooth surface which is virtually free of roughness even on a microscopic scale.
• the object is achieved with respect to the method by roughening an interface of the active layer, forming the at least one intermediate layer and forming a reflection layer.
• An interface of the active layer facing the reflective layer is roughened on its surface.
• the reflection layer is formed substantially planar at its interface directed to the active layer.
• An electromagnetic radiation emitted by the active layer is scattered at the roughening of the interface of the active layer, the scattered electromagnetic radiation is reflected back at the reflective layer.
• the abnormal skin effect is due to surface absorption. Microroughness of the surfaces can increase the absorption in the infrared wavelength range of electromagnetic waves by 50%. This increase in absorption also occurs with roughnesses that are too small to cause diffuse scattering in the infrared wavelength range.
• Each material has a specific optical penetration depth for electromagnetic waves, this optical penetration depth being dependent on the respective wavelength.
• the optical penetration depth describes the path the electromagnetic radiation has traveled in a material after the intensity has decreased by a predetermined amount at a normal incidence. For wavelengths in the infrared wavelength range, for example, the silver penetration depth is 22 nm at room temperature. For other materials, such as gold or copper, the penetration depth is similar to about 20 nm for a wavelength of 10 microns.
• This abnormal skin effect also occurs, for example, when an electromagnetic wave having a wavelength in the visible light region encounters an interface formed to have scattering and reflecting properties.
• the invention advantageously avoids this " effect Separation of the physical effects Dispersion and reflection of an electromagnetic beam, a light beam, which is achieved by separately forming an interface with scattering properties and an interface with reflective properties, the absorption of energy by the abnormal skin effect is avoided. Thus, an increase in the efficiency of the radiation extraction of the radiation-emitting body is achieved.
• the intermediate layer is preferably substantially transparent to the electromagnetic wave generated by the active region.
• the electromagnetic wave impinging on the intermediate layer traverses the intermediate layer and is reflected at the reflection layer.
• the material of the intermediate layer has a refractive index which differs from the refractive index of the material of the active layer, preferably the refractive index of the material of the intermediate layer is smaller than the refractive index of the material of the active layer.
• the refractive index is a physical quantity in optics. It marks the refraction of an electromagnetic wave in the transition between two media.
• the roughening is preferably formed in that the surface of the active layer and thus the interface between the active layer and the intermediate layer has a lateral structuring of a plurality of protruding structural elements.
• the electromagnetic radiation or electromagnetic wave is a wave of coupled electric and magnetic fields. These include radio waves, microwaves,
• wave relationship or ray types The distinction thus formed is based on the characteristics of the radiation or its source which continuously change with frequency and on the different uses or production methods or the various measuring methods used for this purpose.
• the layer sequence of the radiation-emitting body comprises a semiconductor layer sequence.
• This in turn comprises the active layer, which has a pn junction.
• a pn junction denotes a material transition of semiconductor crystals with different types of doping, ie regions in which the doping changes from negative (n) to positive (p).
• the special feature of the pn junction is the formation of a space charge zone in which there is poverty on free charge carriers, as well as an internal electric field, a so-called barrier layer, as long as no electrical voltage is applied to the device.
• the active layer may have a quantum well structure, wherein the Quantum well structure denotes any structure in which charge carriers undergo quantization of their energy states by inclusion.
• a quantum well is a potential curve that limits the freedom of movement of a particle in a spatial dimension, so that only a planar region can be occupied.
• the width of the quantum well decisively determines the quantum mechanical states that the particle can occupy. This leads in particular to the formation of energy levels. Then the particle can only accept discrete, potential energy values.
• the term quantum well structure does not include information about the dimensionality of the quantization. It thus includes quantum wells, quantum wires and quantum dots and any combination of these structures.
• the layer sequence contains a phosphide-, arsenide- or nitride-based
• Compound semiconductor material are suitable for generating radiation of a wavelength mainly in the blue to infrared region of the optical spectrum.
• Phosphide-based compound semiconductor material in this context means that the material preferably comprises AlnGamInn-n-mP with O ⁇ n ⁇ l, O ⁇ m ⁇ l and n + m ⁇ 1.
• This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it may include one or more dopants as well as additional ingredients that do not substantially alter the physical properties of the material.
• the above includes
• Phosphide-based compound semiconductor material in this context also means that the material preferably comprises Ganlnl-nAsmPl-m with O ⁇ n ⁇ l, O ⁇ m ⁇ l.
• This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it may include one or more dopants as well as additional ingredients that do not substantially alter the physical properties of the material.
• the above formula contains only the essential constituents of the crystal lattice (Ga, In, As, P), even if these can be partially replaced by small amounts of other substances.
• the material comprises a nitride III / V compound semiconductor material preferably AlnGamlnl-n-mN with O ⁇ n ⁇ l, O ⁇ m ⁇ l, n + m ⁇ l.
• This material does not necessarily have to have a mathematical exact composition according to the above formula. Rather, it may include one or more dopants as well as additional ingredients that do not substantially alter the characteristic physical properties of the material. For the sake of simplicity, however, the above formula includes only the essential ones
• the material preferably AlnGamlnl-n-mAs with O ⁇ n ⁇ l, O ⁇ msl, n + m ⁇ l comprises.
• This material does not necessarily have a mathematical have exact composition according to the above formula. Rather, it may include one or more dopants as well as additional ingredients that do not substantially alter the physical properties of the material.
• the above formula contains only the essential components of the crystal lattice (Al, Ga, In, As), even though these may be partially replaced by small amounts of other substances.
• the radiation-emitting body is a
• Thin-film semiconductor body That is, a growth substrate for the epitaxially produced radiation-emitting body is thinned or completely removed.
• a basic principle of a thin-film semiconductor body is, for example, in I. Schnitzer et al., Appl. Phys. Lett. 63 (16), 18 October 1993, 2174 to 2176. The disclosure of this document is hereby incorporated by reference.
• a radiation-emitting thin-film semiconductor body is, to a good approximation, a Lambertian surface radiator and is particularly well suited for backlighting, illumination or display purposes.
• a Lambert radiator is a physically ideal radiator. The beam density or the luminance of a Lambertian radiator is constant in all directions.
• the structural elements on the interface of the active layer to the intermediate layer are particularly effective if they optionally have a feature size which is either in the range of the wavelength of the radiation passing through the structural elements or greater than this. It is the structure size in the range of wavelength, if it is equal to or greater than half the wavelength and less than or equal to twice the wavelength. Alternatively, the feature size may be larger than the wavelength to the extent that the laws of geometric optics apply. Upwards, the structure size is limited only by the size of the radiation-emitting body and the thickness of the structured layer.
• the structure size is preferably to be understood as meaning at least one of the variables structure width or structure depth.
• structure width is the width of the
• Structural element measured in the lateral direction, and as a structural depth, the depth of the structural element, measured in the vertical direction, respectively.
• structure size in the range of
• Wavelength of the emitted electromagnetic radiation or is greater than this.
• a wavelength range of 50 to 1000 nm is preferably to be understood as the range of the wavelength, but also feature sizes smaller than 50 nm are possible.
• the reflection layer preferably contains a metal or is formed as a metallic layer.
• This metallic layer preferably comprises a sequence of metallization layers, for example of Ti-Ag-Ti (titanium-silver-titanium).
• Ti-Ag-Ti titanium-silver-titanium
• the different metals have different tasks, so the first Ti layer serves as a bonding agent, followed by an Ag layer, which acts as a reflector.
• the second Ti layer serves as a protective layer in subsequent processes in the production of the radiation-emitting body. Also acting as a primer layer first Ti layer has an influence on the reflection and is part of the Reflective layer.
• Radiation-emitting body are electrically terminated by means of the reflection layer.
• an electrically conductive intermediate layer can be advantageously form an electrical supply to the active region of the radiation-emitting body.
• a metal which is particularly suitable for the reflection of the incident radiation.
• a reflective layer containing silver or gold and a nitride-based compound semiconductor material having a reflective layer containing silver or aluminum is particularly suitable.
• the reflection layer is applied directly to the layer sequence.
• the reflective layer is not self-supporting and is applied to the interface of the intermediate layer.
• the reflection layer can be vapor-deposited or sputtered onto the layer sequence, this allows an intimate connection of the reflection layer with the layer sequence.
• the reflection layer is positively connected to the layer sequence.
• the intermediate layer may consist of a structured layer sequence of materials having different Refractive index exist. Furthermore, the intermediate layer may optionally be formed electrically non-conductive or electrically conductive.
• a dielectric material in particular SiN or SiC> 2 and for an electrically conductive intermediate layer, an oxide, a TCO (transparent conductive oxide), in particular ITO (indium tin oxide), IZO (indium zinc oxides) or ZnO (Zinc oxide), especially suitable.
• a material is used which has a refractive index of near 1.
• the reflective layer can serve as an electrical contact of the radiation-emitting body with an electrically conductive intermediate layer and the supply of the active layer with electrical energy can be guided via the reflective layer and the intermediate layer.
• the interface of the active layer with the intermediate layer is roughened.
• the structural elements may have different structural sizes at least in part. Furthermore, the
• Structural elements be distributed irregularly on the interface.
• a surface of the active layer adjoining the intermediate layer may comprise a plurality of
• the intermediate layer is preferably applied to the surface of the active layer.
• the surface of the intermediate layer facing the active layer is positively bonded to the structure of the surface of the active layer.
• the method for producing the radiation-emitting body is given.
• the method is suitable for producing a radiation-emitting body according to the abovementioned embodiments.
• the method may be characterized by the features mentioned in connection with the radiation-emitting body, in addition to the features mentioned below, and vice versa. This may, for example, relate to material specifications or size specifications.
• the method for producing a radiation-emitting body has the steps described below. Subsequent to the formation of the active layer, a roughening of an interface takes place on the active layer and a formation of at least one intermediate layer. Further, a reflection layer is formed.
• the roughening is preferably carried out by forming a lateral structuring.
• a plurality of protruding structural elements is formed which are arranged irregularly on the boundary surface of the active layer directed toward the subsequently formed reflection layer.
• the reflection layer is preferably formed after the intermediate layer, so that an interface is formed at the transition from the intermediate layer to the reflection layer. This interface is substantially planar, so that radiation incident there is reflected back into the intermediate layer.
• the intermediate layer is disposed between the active layer and the reflective layer.
• Layer sequence an active layer, a semiconductor layer, which can be advantageously grown epitaxially on a substrate.
• the lattice constant of the Material system is preferably adapted to the lattice constant of the substrate.
• the substrate is peeled off during the manufacture of the body.
• the layer sequence can be applied to an intermediate carrier which stabilizes the layer sequence after detachment of the substrate.
• the intermediate carrier can be detached, wherein preferably a carrier is arranged at the location of the detached substrate.
• the interface is patterned by means of natural lithography.
• This method can be described, for example, by applying to the surface of the active layer beads which adhere to the surface of the active layer.
• columnar structural elements remain at the locations where the spheres adhere.
• the space between the structural elements is etched away from the layer sequence by the dry etching process.
• Structure elements incident radiation can be formed.
• the feature width may be 300 ntn and the feature depth 300 nm.
• both structure width and structure depth are in the range of the wavelength of the radiation-emitting body, which lies between 50 and 1000 nm.
• Structural elements having a feature size substantially greater than the wavelength may be formed by wet chemical etching or dry etching.
• the structure size is in the range of> 4 microns.
• etching methods can be used to form structural elements on the interface or for roughening the interface.
• etching methods are, for example, wet-chemical etching or dry etching, including reactive ion etching, ion beam etching or chemically assisted ion beam etching.
• photolithography is particularly suitable for the formation of regular interface structures.
• Chemical vapor deposition can generally be described as depositing a solid component onto a heated surface due to a chemical reaction from the gas phase. The prerequisite for this is that volatile compounds of the layer components exist, which deposit the solid layer at a certain reaction temperature.
• the process of chemical vapor deposition is characterized by at least one reaction on the surface of the workpiece to be coated. At least two gaseous starting compounds and at least two reaction products, at least one of which is gaseous and at least one in the solid phase must be involved in this reaction.
• evaporation methods such as thermal evaporation, electron beam evaporation, laser beam evaporation, Arc evaporation, molecular beam epitaxy or ion plating. All these methods have in common that the material to be deposited is present in solid form in the most evacuated coating chamber. By bombardment with laser beams, magnetically deflected electrons and by arc discharge, the material is evaporated. The vaporized material moves either ballistic or guided by electric fields, through the chamber and strikes the parts to be coated, where it comes to the film formation.
• the intermediate layer can preferably also be formed by a spin coating method.
• a wafer is fixed on a turntable.
• a planarization is preferably provided, which takes place, for example, by mechanical polishing a planar surface on the boundary layer formed to a reflective layer yet to be applied.
• Wafer is a circular or square, approximately 1 mm thick disc, which is the substrate of the radiation-emitting body.
• the epitaxial layer construction is carried out with photoelectric layers for producing a plurality of radiation-emitting bodies according to the invention.
• the reflection layer can also be applied by the aforementioned methods.
• the invention is based on a
• Figures 2A to 2D a schematic stepwise
• FIG. 1 shows an active layer 10 which has a structuring 20 at its boundary surface 15.
• Structuring 20 is shown and depicted uniformly in the illustration, which is to be understood as meaning a particular embodiment, but not a limitation of the subject invention to this feature of uniformity.
• the structuring 20 is formed from individual protruding
• Structural elements 30 which are arranged in a plurality on the surface of the active layer 10 and thus form the interface 15 to an intermediate layer 40.
• the intermediate layer 40 is arranged in a form-fitting manner on the surface of the active layer 10.
• the intermediate layer 40 is disposed directly on the interface 15 of the active layer 10.
• a further layer is arranged positively with two layers.
• special properties, such as filter properties or reflectivity of the arrangement can thus be changed and thus the radiation-emitting body can be optimized for a particular intended use.
• the reflectivity of the overall arrangement can be increased.
• the intermediate layer is preferably formed in a thickness of 200 nm to 2000 nm.
• the intermediate layer 40 has a refractive index which is different from the refractive index of the active layer 10 and preferably has the lowest possible absorption. This ensures that a deflection of an electromagnetic beam takes place at the interface 15 of the active layer 10 to the intermediate layer 40.
• the structuring 20 fulfills the task of scattering. Each individual electromagnetic beam tracks a particular direction in a medium such as the active layer 10. In a transition from one medium to another medium whose refractive index differs from that of the first, for example at the interface 15 of the active layer 10 in the intermediate layer 40, a part of the electromagnetic beam is reflected, another part is according to the Snellius Refraction law distracted.
• This distraction takes place when passing into a medium with a greater refractive index to the solder of the interface and the passage into a medium with a smaller refractive index of the solder of the interface away.
• total reflection occurs when the angle of incidence of the electromagnetic beam exceeds a certain value.
• the intermediate layer 40 is formed on its interface 45 formed with a reflective layer 50 having a planar surface.
• the interface 45 is formed by a reflection layer 50, which is preferably formed from metal.
• the reflective layer 50 if it is a metallic layer, is preferably formed with silver or gold, since these materials are particularly suitable for a InGaAlP-having radiation-emitting body.
• the thickness of the reflective layer 50 is selected so that the incident radiation does not penetrate the reflective layer 50, but is substantially reflected at it.
• the thickness of the reflective layer 50 is in the
• the reflection layer 50 contains a metal such as silver or gold, this is at the same time electrically conductive, which advantageously makes it possible to supply the radiation-emitting body with electrical energy via the reflection layer 50.
• the reflection layer 50 has a substantially planar surface at the common interface 45 with the intermediate layer 40. This is formed, for example, by a mechanical planarization process, such as mechanical polishing and subsequent application of a metal layer. Other methods of producing a planar surface are also possible. Examples include, for example, the use of a low melting point material that begins to flow in a thermal treatment at temperatures less than 500 ° C and thus forms a planar surface.
• etch-back technology Another possibility for producing a planar surface is given by the so-called ion-beam technology or the etch-back technology.
• etch-back technology the rough surface is coated with a photoresist and then "etched back" (etch-back) using an ion beam, an ion beam, to create a smooth surface.
• the direction reversal of the incident radiation occurring at the reflection layer 50 is based on reflection at the
• the structure of the boundary layer 15 thus results in a scattering of all the boundary layer 15 urgent electromagnetic radiation.
• FIG. 2 shows individual method steps for forming a radiation-emitting body according to the principle described above.
• FIG. 2A shows the active layer 10 with its structured surface, which forms the interface 15 with respect to the intermediate layer 40.
• the feature size of the features 30 is typically within the range of
• Wavelength of the emitted electromagnetic radiation or is greater than this.
• a wavelength range of 50 to 1000 nm is preferably to be understood as the range of the wavelength, but also feature sizes smaller than 50 nm are possible.
• Structure size relates to the width B and the depth T of the structural elements 30.
• Such structural elements 30 can be formed by means of one of the aforementioned methods. In the illustration, the structural elements 30 are uniform. This is a special form of structuring 20, which can be formed, for example, by a photolithographic process with a subsequent etching process. By means of a natural It is also possible to form lithographic processes of differently sized and irregularly arranged structural elements 30 on the boundary surface 15.
• FIG. 2B shows the active layer 10 with its structured surface which forms the interface 15 with respect to the intermediate layer 40 and the intermediate layer 40 arranged directly and positively thereon.
• the intermediate layer 40 can improve the mechanical stability of the radiation-emitting body and influence the electrical conductivity.
• the intermediate layer 40 may contain a dielectric material or SiN or silicon oxide.
• the intermediate layer 40 may contain a conductive metal oxide, for example ITO or ZnO.
• the intermediate layer 40 is form-fitting, for example by chemical vapor deposition (CVD) or physical vapor
• the intermediate layer 40 may be formed at least partially electrically conductive or insulating. If the intermediate layer 40 is formed, for example, by a vapor deposition method, structuring occurs on the outer surface of the intermediate layer 40, the cause of which lies in the structuring 20 of the interface 15. These unevennesses on the surface of the intermediate layer 40 facing the reflection layer 50 are removed by a planarization step.
• An example of such a planarization step is mechanical polishing. After planarization, a substantially planar surface shown in FIG. 2D is formed on the intermediate layer 40. On this, the reflection layer 50 is applied.

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• 2008
  • 2008-05-21 DE DE102008024517A patent/DE102008024517A1/de not_active Withdrawn
  • 2008-12-19 KR KR1020107016854A patent/KR101652531B1/ko not_active Expired - Fee Related
  • 2008-12-19 EP EP08868217.4A patent/EP2225782B1/de not_active Not-in-force
  • 2008-12-19 WO PCT/DE2008/002136 patent/WO2009083001A2/de not_active Ceased
  • 2008-12-19 CN CN2008801229538A patent/CN101911319B/zh not_active Expired - Fee Related
  • 2008-12-19 JP JP2010540027A patent/JP5781766B2/ja not_active Expired - Fee Related
  • 2008-12-19 US US12/811,030 patent/US8723199B2/en active Active

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