Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
  • H01L33/40—Materials therefor
  • H01L33/405—Reflective materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/42—Wire connectors; Manufacturing methods related thereto
  • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
  • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
  • H01L2224/4805—Shape
  • H01L2224/4809—Loop shape
  • H01L2224/48091—Arched
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
  • H01L33/46—Reflective coating, e.g. dielectric Bragg reflector
  • H01L33/465—Reflective coating, e.g. dielectric Bragg reflector with a resonant cavity structure

Definitions

• the invention relates to a light-emitting diode chip, in particular a thin-film LED chip.
• the object of the present invention is to provide a thin-film light-emitting diode chip with a high efficiency and low absorption losses.
• a thin-film light-emitting diode chip is specified, in which the distance between a mirror layer and a light-generating active zone is set such that a radiation emitted by the active zone interferes with a light reflected by the mirror layer. This interference affects the internal quantum efficiency of the active zone and achieves a directional radiation characteristic of the active zone.
• the directional radiation characteristic has at least one preferred direction.
• the thin-film light-emitting diode chip has a coupling-out layer which is at least semiconductive. The decoupling layer is not an antireflection coating.
• a thin-film light-emitting diode chip is characterized in particular by the following characteristic features: on a first main surface of a radiation-generating epitaxial layer sequence facing a carrier element, a reflective layer is deposited or formed which reflects back at least part of the electromagnetic radiation generated in the epitaxial layer sequence; the epitaxial layer sequence has a thickness in the range of 20 ⁇ m or less, in particular in the range between 4 ⁇ m and 10 ⁇ m; and the epitaxial layer sequence contains at least one semiconductor layer having at least one surface which has a mixing structure which, in the ideal case, leads to an approximately ergodic distribution of the light in the epitaxial epitaxial layer sequence, ie it has a possibly ergo-stochastically scattering behavior.
• a thin-film light-emitting diode chip is to a good approximation a Lambert surface radiator.
• the basic principle of a thin-film light-emitting diode chip is described, for example, in the publication I. Schnitzer et al. , Appl. Phys. Lett. 63 (16), 18 October 1993, 2174 - 2176.
• a thin-film LED chip is understood in particular to be a light-emitting diode chip having a layer structure with epitaxially grown layers, from which the growth substrate has preferably been removed after growth. At least part of the epitaxially grown layers are semiconductor layers.
• the chip may have a carrier different from the growth substrate on which the layer structure is applied.
• the specified thin-film LED chip has no resonator.
• the specified thin-film LED chip in contrast to a RCLED (Resonant Cavity Light Emmiting Diode) comprises only a single mirror.
• the thin-film LED chip and in particular the epitaxial layer construction advantageously does not comprise a Bragg mirror, in contrast to an RCLED.
• the thin-film light-emitting diode chip is GaN-based.
• the light generated in the semiconductor body is coupled out directly from the semiconductor body, ie without absorption losses and reflection losses due to a substrate arranged downstream of the radiation-emitting epitaxial layer sequence.
• Near-field optical effects greatly affect the output efficiency of thin-film LEDs.
• the advantage of using near-field optical effects is the increase in the proportion of radiation that is coupled out of the light-generating semiconductor.
• the thin-film chip specified here is characterized by a high coupling-out efficiency, which can exceed 70%.
• the active zone has several sublayers, for example in the form of a single quantum well or a multiple quantum well structure.
• the semiconductor body has at least a first semiconductor layer of a first conductivity type, at least one second semiconductor layer of a second conductivity type and the active zone arranged therebetween.
• the first semiconductor layer is preferably p-doped, and the second semiconductor layer is preferably n-doped.
• the semiconductor layers are preferably transparent, ie permeable to the radiation generated in the active zone.
• the semiconductor body may, for example, contain a barrier layer which is arranged between the first semiconductor layer and the mirror layer and z. B. acts as a charge carrier diffusion barrier, that prevents the emergence of charge carriers from the first semiconductor layer in the direction of the mirror layer.
• the charge carrier barrier layer is preferably at least partially semiconducting and may be included in a variant Al.
• the carrier barrier layer is preferably transparent to the radiation generated in the active zone.
• the semiconductor body is preferably identical to the epitaxially grown layer structure of the chip.
• the layers of the semiconductor body are grown on a growth substrate, which is present as a wafer.
• the n-doped second semiconductor layer is epitaxially deposited.
• the active zone or partial layers of the active zone, the p-doped first semiconductor layer and optionally a charge carrier barrier layer are epitaxially grown in succession.
• the mirror layer is preferably applied by sputtering or vapor deposition.
• the mirror layer is preferably a metal layer.
• the mirror layer is preferably highly reflective broadband, wherein z. B. at least 70%, preferably at least 80% of the incident light reflected.
• the mirror layer is z. B. from Ag, Au, Pt or Al and / or produced from an alloy of at least two of these metals.
• the mirror layer may also be a multi-layer sequence having multiple layers of various of the aforementioned metals or alloys.
• the layer composite comprising the epitaxial layer sequence, the growth substrate and the mirror layer is preferably firmly connected by eutectic bonding with a carrier, which may be optimized in terms of electrical and / or thermal properties and on the optical properties of which no requirements are made.
• the carrier is preferably electrically conductive or at least semiconducting. Suitable as carrier material z. As germanium, GaAs, SiC, AlN or Si. A surface of the carrier facing the mirror layer is preferably planar. The on achsubstrat is detached after joining the layer composite with the carrier from the Halbleier Sciences.
• At least one adhesion-promoting layer may be provided between the mirror layer and the carrier.
• the preferably electrically conductive adhesion-promoting layer connects the carrier to the epitaxial layer sequence, the mirror layer facing the carrier.
• the adhesion-promoting layer may in particular be a metal layer z. PbSn (Lot), AuGe, AuBe, AuSi, Sn, In or Pdln.
• the mirror layer can by a facing the adhesion-promoting layer diffusion barrier layer, the z. B. Ti and / or W, be protected.
• a diffusion barrier layer prevents penetration of material from the primer layer into the mirror layer.
• All of the layers of the light-emitting diode chip mentioned here, in particular the active zone and the semiconductor layers of the semiconductor body, can each consist of several partial layers.
• the semiconductor body comprises a decoupling layer with a decoupling surface.
• the radiation distribution in the coupling-out layer has preferred directions.
• the coupling-out layer is preferably connected to the second semiconductor layer, the z. B. n-doped, identical.
• the first semiconductor layer, the z. B. p-doped is preferably disposed between the mirror layer and the active zone.
• the mirror layer is arranged so close to the light source, ie the active zone, that in the case of interference optical near-field effects come to bear clearly.
• the interference of the generated and the reflected light wave influences the spontaneous emission in the active zone, in particular the lifetime of the radiative recombination and thus the internal quantum efficiency in the light-generating layer.
• Certain mirror spacings eg, ⁇ / 4, 3 ⁇ / 4, 5 ⁇ / 4) to the active layer, which produce a favorable (angle-dependent) emission characteristic, are accompanied by an increase in the internal quantum efficiency.
• the distance between the light-generating layer and the mirror layer is smaller than 1.75 ⁇ in one variant. In a further advantageous variant, this distance is smaller than 1, 5 ⁇ .
• the small distance has the advantage that the spontaneous emission of the active zone is controlled by the interaction of the radiation generated in the active zone and the radiation reflected by the mirror.
• a distance between the light-generating layer and the mirror layer which is substantially (2m + l) ⁇ / 4
• a directional radiation of the active zone is obtained whose emission characteristic deviates from the Lambert 'radiation characteristic and the alternately arranged areas with has a high and a low intensity.
• the distance of the mirror to the light-generating layer can be chosen such that the emission characteristic within the semiconductor can also be adjusted such that a high proportion of radiation is already within the limit angle of total reflection at the first impingement on the light-coupling interface.
• the distance between the mirror layer and the active zone is in different variants z. B.
• the radiation distribution has a preferential direction, which is perpendicular to the outcoupling surface
• the radiation distribution has two preferred directions, one perpendicular to the outcoupling surface and one obliquely to this;
• the radiation distribution has three preferred directions, one perpendicular to the Auskoppelflache and two obliquely to this.
• the wavelength of the coupled-out radiation can be in the infrared range, visible range or ultraviolet range.
• the semiconductor body can be based on wavelength based on various semiconductor material systems are produced.
• a semiconductor body based on In x Ga y Al ⁇ - x - y As for visible red to yellow radiation, for example, a semiconductor body based on In x Ga y Al ⁇ - x _ y P and short-wave visible (green to blue) or UV radiation z.
• the spectral width of the exiting radiation can, for. B. 15 to 40 nm. However, the spectral half width of the generated radiation is not limited to the specified range.
• the distance between the light-generating layer and the mirror layer is preferably identical to the layer thickness of the p-layer.
• the second semiconductor layer may have a planar decoupling surface.
• the emission characteristic of the light emerging from the chip deviates from the lambertian emission characteristic and has a high radiation density in at least one preferred direction and a low radiation density in other angular ranges.
• the decoupling surface of the second semiconductor layer can be roughened in such a way that the radiation that is not decoupled when it encounters this interface is scattered back into the semiconductor in different directions. This redistribution of the radiation directions avoids a so-called waveguide effect and thus increases the coupling-out efficiency.
• the radiation characteristic of the radiation emerging from the chip is in this case substantially Lambert's.
• the second semiconductor layer may be arranged between the active zone and an antireflection coating whose thickness is approx. is equal to one quarter wavelength.
• the antireflection coating is preferably a dielectric layer which is applied to the outcoupling surface of the semiconductor body after the removal of the growth substrate.
• the light-emitting diode chip is preferably arranged in an optical component in a recess of a housing, wherein the recess may have a reflective surface.
• the LED chip can be encapsulated in this recess with a potting compound.
• FIG. 1 shows an exemplary thin-film LED chip with a planar output surface
• FIG. 2 shows a thin-film LED chip with a semiconductor body which comprises a barrier layer and with an antireflection coating
• FIG. 3 shows a thin-film LED chip with a roughened outcoupling surface
• FIG. 4 shows an optical component with an LED chip.
• FIG. 1 shows a schematic detail of an exemplary thin-film LED chip 100 which has a carrier 6 and a multilayer structure 10. Between carrier 6 and multilayer construction 10, an adhesion-promoting layer 5 is arranged.
• the multilayer structure 10 comprises a light-emitting active zone 3, which is arranged between a p-type first semiconductor layer 1 and an n-type second semiconductor layer 2.
• the first semiconductor layer 1 is arranged between the active zone 3 and a metallic mirror layer 4.
• the electrically conductive mirror layer 4 functions both as a mirror and as an electrical contact layer to the first semiconductor layer.
• the mirror layer 4 is protected by a diffusion barrier layer 45, which is arranged between the mirror layer 4 and the adhesion-promoting layer 5.
• the first and second semiconductor layers 1 and 2 and the active zone 3 together form a semiconductor body 123. Together with the diffusion barrier layer 45 and the mirror layer 4, this forms the multilayer structure 10.
• the second semiconductor layer 2, the active zone 3 and the first semiconductor layer 1 are epitaxially produced on a growth substrate not shown here in succession.
• the mirror layer 4 is applied on this epitaxial layer structure is z. B. by sputtering or vapor deposition, the mirror layer 4 is applied.
• the multi-layer structure 10 is connected by means of the adhesion-promoting layer 5 to the carrier 6, the z. B. consists of Ge or has a substantial part Ge, connected.
• the growth substrate is then removed.
• the second semiconductor layer 2 facing the growth substrate forms a coupling-out layer after the removal of this substrate, and the surface of this coupling-out layer facing away from the active zone 3 forms a coupling-out surface 20, which is planar in this exemplary embodiment.
• the propagation direction of the radiation generated in the active zone 3 and the radiation reflected by the mirror layer 4 is indicated in FIG. 1 by the arrows 7 and 8, respectively.
• the light generated by the interference of the two radiation components 7 and 8 emerges from the multilayer structure 10 in a direction away from the carrier 6.
• the near-field effects utilized in the specified thin-film LED chip are comparable to a cavity effect, ie the wave effects occurring in an optical resonator (resonant cavity).
• its emission characteristic can be adjusted within the light-generating semiconductor such that a majority of the photons strike the coupling-out boundary surface at an angle which is below the angle of the total reflection.
• the use of the cavity effect in the thin-film LED chip significantly reduces the recycling rate.
• Another advantage of using the cavity effect in thin-film LEDs is the influence of the radiation characteristic outside the semiconductor. Depending on how the angular distribution of the photons within the semiconductor is dependent on the distance between the mirror and the light-generating layer, the emission characteristic outside the semiconductor can be varied and, in particular, a radiation distribution with preferential directions can be achieved with an uncoated decoupling surface.
• the zero-order output is set.
• An expedient concrete structure of a thin-film LED chip based on GaN has the following layer sequence:
• At least one further, preferably one thin carrier barrier layer 11 is arranged between the active zone 3 and the semiconductor layer facing the mirror layer 4 (ie the first semiconductor layer 1).
• the carrier barrier layer 11 is preferably part of the semiconductor body and therefore grown epitaxially and semiconducting.
• a passivation layer 8 which is formed as an antireflection coating by setting a certain thickness in an expedient embodiment, is provided on the second semiconductor layer 2. see. Such may be after removal of the growth substrate z. B. be applied by deposition.
• the anti-reflection layer 8 is not epitaxially generated and consists for example of silicon oxide or silicon nitride.
• the exemplary embodiment of a thin-film LED chip according to FIG. 3 has, in contrast to the exemplary embodiment according to FIG. 2, a roughened outcoupling surface 20.
• the profit generated by the use of Cavity effects is thereby only slightly weakened.
• An emission characteristic that is only slightly influenced by distance fluctuations of the active layer to the mirror proves to be an advantage.
• an optical device is shown, the 100 a zener LED chip z. B. according to embodiments presented in Figures 1 to 3.
• the light-emitting diode chip 100 is mounted on a leadframe 92 and installed in a recess of the housing 91.
• the recess of the housing 91 preferably has a light-reflecting surface.
• the LED chip is encapsulated with a potting compound 90.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Led Devices (AREA)

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• 2005
  • 2005-04-11 DE DE102005016592A patent/DE102005016592A1/de not_active Withdrawn
  • 2005-04-14 WO PCT/DE2005/000677 patent/WO2005101531A2/de active Application Filing
  • 2005-04-14 JP JP2007507664A patent/JP2007533143A/ja active Pending
  • 2005-04-14 US US11/578,657 patent/US7709851B2/en active Active
  • 2005-04-14 KR KR1020067023305A patent/KR20070009673A/ko not_active Application Discontinuation
  • 2005-04-14 EP EP05742638A patent/EP1738420A2/de not_active Withdrawn

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