U.S. patent application number 15/255068 was filed with the patent office on 2016-12-22 for optoelectronic device.
The applicant listed for this patent is OSRAM Opto Semiconductors GmbH. Invention is credited to Alexander LINKOV, Matthias SABATHIL.
Application Number | 20160370513 15/255068 |
Document ID | / |
Family ID | 49170706 |
Filed Date | 2016-12-22 |
United States Patent
Application |
20160370513 |
Kind Code |
A1 |
LINKOV; Alexander ; et
al. |
December 22, 2016 |
OPTOELECTRONIC DEVICE
Abstract
The invention relates to an optoelectronic device (101),
comprising: a semiconductor layer sequence (103) comprising an
emitter layer (105) for emitting electromagnetic radiation, a
converter (113) for converting electromagnetic radiation with a
first wavelength into an electromagnetic radiation with a second
wavelength which differs from the first wavelength, a scattering
body (109) for scattering at least a part of the electromagnetic
radiation emitted by the emitter layer (105) in the direction of
the converter (113) in order to convert at least a part of the
emitted electromagnetic radiation, wherein the scattering body
(109) comprises a positive, temperature-dependent scattering
cross-section and so, as the temperature increases, scattering of
the electromagnetic radiation in the scattering body (109) in the
direction of the converter can be increased. The invention also
relates to a scattering body (109).
Inventors: |
LINKOV; Alexander;
(Regensburg, DE) ; SABATHIL; Matthias;
(Regensburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OSRAM Opto Semiconductors GmbH |
Regensburg |
|
DE |
|
|
Family ID: |
49170706 |
Appl. No.: |
15/255068 |
Filed: |
September 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14430202 |
Mar 20, 2015 |
9459383 |
|
|
PCT/EP2013/069040 |
Sep 13, 2013 |
|
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15255068 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 5/0278 20130101;
H01L 33/502 20130101; H01L 33/505 20130101; G02B 5/0263 20130101;
G02B 5/0294 20130101; H01L 33/58 20130101; G02B 5/0242 20130101;
H01L 2933/0091 20130101; H01L 33/56 20130101; H01L 33/504 20130101;
G02B 5/0247 20130101 |
International
Class: |
G02B 5/02 20060101
G02B005/02; H01L 33/50 20060101 H01L033/50; H01L 33/56 20060101
H01L033/56 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2012 |
DE |
102012217643.8 |
Claims
1. Scattering body for scattering electromagnetic radiation for an
optoelectronic device, wherein the scattering body has a positive,
temperature-dependent scattering cross-section and so as the
temperature increases, scattering of the electromagnetic radiation
in the scattering body can be increased, wherein the scattering
body comprises at least one scattering region and a plurality of
non-scattering regions, wherein the scattering region has a
positive, temperature-dependent scattering cross-section, wherein
the non-scattering regions are transparent for the emitted
electromagnetic radiation.
2. Scattering body according to claim 1, wherein the at least one
scattering region is formed above a converter.
3. Scattering body according to claim 2, wherein the converter is
embodied as a converter layer, wherein the scattering region is
rectangular as seen in cross-section and has a width equal to the
width of the converter layer.
4. Scattering body according to claim 1, wherein to the left and
right next to the scattering region in cross-section the
non-scattering regions are disposed.
5. Scattering body according to claim 1, wherein the at least one
scattering region is formed above a converter, wherein the
converter is embodied as a converter layer, wherein the scattering
region is rectangular as seen in cross-section and has a width
equal to the width of the converter layer, wherein to the left and
right next to the scattering region in cross-section the
non-scattering regions are disposed.
6. Scattering body according to claim 1, wherein the non-scattering
region is formed above the converter.
7. Scattering body according to claim 6, wherein the converter is
embodied as a converter layer, wherein the non-scattering region is
rectangular as seen in cross-section and has a width equal to the
width of the converter layer.
8. Scattering body according to claim 1, wherein to the left and
right next to the non-scattering region in cross-section the
scattering regions are disposed.
9. Scattering body according to claim 1, wherein the scattering
region comprises a matrix material of silicone and scattering
particles.
10. Scattering body according to claim 1, wherein the
non-scattering regions comprise a matrix material of silicone and
no scattering particles.
11. Scattering body according to claim 1, wherein the scattering
particles are formed by glass, BaF.sub.2, LiF or MgF.sub.2.
12. Scattering body according to claim 1, wherein the matrix
material of the scattering region is identical to the matrix
material of the non-scattering regions.
13. Scattering body according to claim 1, wherein the matrix
material is dialkyl polysiloxane.
14. Scattering body according to claim 1, wherein the
non-scattering region is formed above a converter, wherein the
converter is embodied as a converter layer, wherein the
non-scattering region is rectangular as seen in cross-section and
has a width equal to the width of the converter layer, wherein to
the left and right next to the non-scattering region in
cross-section the scattering regions are disposed.
15. Scattering body according to claim 1, wherein a
radiation-permeable matrix material with a first refraction index
and scattering particles embedded therein and having a second
refraction index are formed, wherein a difference between the first
and the second refraction index can be increased as the temperature
increases and so as the temperature increases, scattering of
electromagnetic radiation in the scattering body can be increased.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 14/430,202, filed Mar. 20, 2015, which claims
the benefit of International Patent Application No.
PCT/EP2013/069040, filed Sep. 13, 2013, which claims priority to
German Application No. 102012217643.8, filed Sep. 27, 2012, which
are incorporated herein by reference in their entirety.
DESCRIPTION
[0002] The invention relates to an optoelectronic device.
[0003] From laid-open document WO 2012/022628 A1 an optoelectronic
semiconductor component and a scattering body is known. The
scattering body is designed to scatter light, wherein the light
scattering decreases as temperature increases. At a temperature of
300 K, the scattering body is only partially permeable to a
radiation. Only as the temperature increases does the scattering
body become transparent.
[0004] The object of the invention can be considered that of
provided an optoelectronic device.
[0005] The object of the invention can also be considered that of
providing a scattering body.
[0006] These objects are achieved by the subject matter of the
independent claims. Advantageous embodiments are the subject of
dependent subordinate claims.
[0007] According to one aspect, an optoelectronic device is
provided. The device comprises a semiconductor layer sequence which
comprises an emitter layer for emitting electromagnetic
radiation.
[0008] A converter is also provided which can convert
electromagnetic radiation with a first wavelength, i.e.
particularly electromagnetic radiation corresponding to a first
optical spectrum, into an electromagnetic radiation with a second
wavelength, i.e. particularly into an electromagnetic radiation
corresponding to a second optical spectrum, wherein the second
wavelength differs from the first wavelength.
[0009] Furthermore, the optoelectronic device comprises a
scattering body for scattering at least a part of the
electromagnetic radiation emitted by the emitter layer in the
direction of the converter in order to convert at least a part of
the emitted electromagnetic radiation.
[0010] The scattering body comprises a positive,
temperature-dependent scattering cross-section and so, as the
temperature increases, scattering of the electromagnetic radiation
in the scattering body in the direction of the converter can be
increased. That is to say in particular that as the temperature
increases, the scattering of the electromagnetic radiation in the
scattering body in the direction of the converter increases. That
is to say in particular that at higher temperatures more
electromagnetic radiation is scattered in the direction of the
converter compared to at lower temperatures.
[0011] The scattering body can be adapted for interacting with
incident electromagnetic radiation, i.e. for absorbing,
transmitting and scattering incident electromagnetic radiation. The
portion of the absorption I.sub.a, and the portion of transmission
I.sub.t and the portion of scattering I.sub.s thereby total 100%.
I.sub.a+I.sub.t+I.sub.s=100% is true. Depending on the properties
of the scattering body I.sub.a, I.sub.t and I.sub.s can be
dependent on the temperature.
[0012] The fact that as the temperature increases, scattering of
the electromagnetic radiation in the scattering body can be
increased means particularly that the portion of scattering I.sub.s
of the scattering body is greater at higher temperatures than the
portion of scattering I.sub.s at lower temperatures, wherein the
sum of I.sub.a, I.sub.t and I.sub.s comes to 100% at the respective
temperature.
[0013] That is to say particularly that the scattering body
scatters a greater portion of the electromagnetic radiation at
higher temperatures and therefore transmits and absorbs less
compared with at lower temperatures.
[0014] "In the direction of the converter" means in this case and
hereinunder that the scattered electromagnetic radiation is
incident at least on a surface of the converter. In particular,
this surface of the converter is arranged transverse to the main
radiation direction of the electromagnetic radiation. The "main
radiation direction" means in this case transverse to the growth
direction of the semiconductor layer sequence.
[0015] According to a further aspect, a scattering body is provided
for scattering electromagnetic radiation for an optoelectronic
device, wherein the scattering body has a positive
temperature-dependent scattering cross-section and so as the
temperature increases, scattering of the electromagnetic radiation
in the scattering body can be increased.
[0016] A positive temperature-dependent scattering cross-section
means particularly that the scattering of the scattering body in
the direction of the converter becomes greater as the temperature
increases. In particular, the scattering body scatters more
electromagnetic radiation at higher temperatures compared to at
lower temperatures. In particular, an increase in temperature of at
least 25.degree. C., 30.degree. C. or 40.degree. C. and at most
100.degree. C., 125.degree. C. or 150.degree. C. can take place. In
particular, the temperature difference AT between the final and the
starting temperature is at least 30 K, 40 K or 50 K and at most 75
K, 80 K, 100 K or 150K.
[0017] In the case of optoelectronic devices it is generally the
case that they become warmer during operation. That is to say a
temperature of the device increases during operation. This
generally leads to a spectral shift in the emitted electromagnetic
radiation. For example, the spectrum can be red-shifted or
blue-shifted. For example, as the temperature increases, an
intensity distribution in the emitted electromagnetic radiation can
change.
[0018] The effects mentioned above generally lead to a chromaticity
coordinate shift.
[0019] By the provision of a scattering body comprising a positive
temperature-dependent scattering cross-section, the above-mentioned
effects, particularly the chromaticity coordinate shift, can
advantageously be compensated for at least partially, and in
particular entirely. This is the case because, as the temperature
increases, the scattering body increasingly scatters the originally
emitted electromagnetic radiation in the direction of the
converter. That is to say particularly that as the temperature
increases, the converter increasingly converts electromagnetic
radiation and in this respect, re-radiates the correspondingly
converted electromagnetic radiation. The converted electromagnetic
radiation can then, for example, compensate for gaps or intensity
variations in the spectrum of the electromagnetic radiation emitted
by means of the emitter layer.
[0020] Provided that, for example, by reason of the increasing
temperature, a red-shift of the spectrum of the originally emitted
electromagnetic radiation has taken place, the converter can, for
example, supplement the now lower blue or green portions in the
spectrum and so a chromaticity coordinate is achieved in the
overlap of the two spectra of the emitted radiation of the emitter
layer and the emitted, converted radiation of the converter, this
chromaticity coordinate essentially corresponding to the
chromaticity coordinate at a temperature existing prior to the
spectral shift of the spectrum, which is generally the case just
after the device has gone into operation.
[0021] Furthermore, in an advantageous manner it is possible to
achieve almost complete optical compensation of the chromaticity
coordinate shift by a purely passive optical apparatus, in this
case the scattering body. Therefore, in an advantageous manner, it
is possible to dispense with additional electrical compensation.
This considerably simplifies a structure. With corresponding
optical quality of the scattering body, stabilisation of the
emitted spectrum of the optoelectronic device can be effected with
no effect on efficiency.
[0022] A scattering cross-section in terms of the present invention
is particularly a measure of the probability that between an
incident wave radiation, in this case the electromagnetic
radiation, and the scattering body, scattering, i.e. an interaction
between the electromagnetic radiation and the scattering body, will
take place.
[0023] The fact that the scattering cross-section is a positive
temperature-dependent scattering cross-section means particularly
that the scattering cross-section increases as the temperature
increases.
[0024] In one embodiment provision can be made that the scattering
body for radiation emitted by the emitter layer is transparent at a
temperature of 300 K. Only as the temperature increases will the
scattering body become still only partially permeable or partially
transparent, by reason of the increasing scattering cross-section,
for the radiation emitted by the emitter layer or generally for
electromagnetic radiation.
[0025] According to a further embodiment, provision can be made
that the scattering body comprises a radiation-permeable matrix
material with a first refraction index and scattering particles
embedded therein and having a second refraction index, wherein a
difference between the first and the second refraction index can be
increased as the temperature increases. That is to say
particularly, that the difference between the first and the second
refraction index increases as the temperature increases. That is to
say particularly that the difference in the refraction index
between the matrix material and the scattering particles can be
increased or does increase as the temperature increases. By reason
of this property it is achieved in a particularly advantageous
manner that the scattering body has a positive
temperature-dependent scattering cross-section.
[0026] In another embodiment at a predetermined temperature,
particularly 300 K, the scattering particles have approximately the
same refraction index as the matrix material. In an advantageous
manner this means that at this temperature there is no optical
contrast between the scattering particles and the matrix material.
In an advantageous manner this means that electromagnetic radiation
can propagate unhindered through the scattering body and in this
respect can be coupled-out.
[0027] In a further embodiment provision can be made that at a
higher temperature the refraction number of the matrix material
changes more than that of the scattering particles and so a
difference between the individual refraction indices increases.
Thus in an advantageous manner increased optical scattering takes
place.
[0028] According to one embodiment the matrix material can be a
silicone. The silicone can be, for example, a polysiloxane, a
methylene-silicone, a phenylene-silicone or a silicone-epoxide
hybrid material. The silicone can also preferably be a silicone
from a respective subgroup of the above-mentioned silicone types.
Preferably, in the case of a methylene-silicone the refraction
index can be between 1.40 and 1.42. In the case of a
phenylene-silicone a refraction index can be, for example, greater
than 1.41. In particular a refraction index of a phenylene-silicone
can be at most 1.56.
[0029] In particular, the phenylene-silicones can advantageously
have increased thermal stability and increased chemical
resistance.
[0030] In particular, the methylene-silicones have beneficial
properties, for example, mechanical properties in relation to use
in the health sector. Furthermore, the methylene-silicones can be
used for encapsulation by reason of their good mechanical
properties. That is to say also, for example, that a converter
comprising a matrix material made from a methylene-silicone is
particularly suitable for an encapsulation of the optoelectronic
device. Therefore the device is advantageously particularly well
protected against external influences.
[0031] According to a further embodiment provision can be made that
the particle material, i.e. the material from which the scattering
particles are formed, is glass, BaF.sub.2, LiF or MgF.sub.2.
Preferably, different scattering particles can be embedded in the
matrix material. For example, the particle material can be a
silicon oxide, silicon dioxide or a metal fluoride.
[0032] According to a further embodiment provision can be made that
a scattering particle size is between 200 .mu.m and 10,000 .mu.m,
particularly between 200 .mu.m and 1,000 .mu.m. Preferably, the
scattering particles each have the same size or a different size.
The scattering particles can, for example, each be of a different
form or of the same form. The scattering particles can be
homogeneously or unhomogeneously dispersed in the scattering
body.
[0033] According to another embodiment provision can be made that
the scattering body is formed as a lens to refract the
non-scattered electromagnetic radiation. In this way the scattering
body can advantageously refract the non-scattered electromagnetic
radiation and therefore change a radiation direction. For example,
provision can be made that the scattering body is formed as a
collecting lens for focussing the non-scattered electromagnetic
radiation. Preferably, the scattering body, as a collecting lens,
is of a convex or biconvex form. In the case of an appropriate
geometric arrangement of the converter relative to the lens, this
lens can also refract the converted electromagnetic radiation and,
in the case of the collecting lens, can focus it.
[0034] According to a further embodiment provision can be made that
the semiconductor layer sequence and the converter are arranged
adjacent to one another on a common carrier substrate surface.
[0035] "Adjacent to one another" in terms of the present invention
means particularly that the converter and the semiconductor layer
sequence are arranged immediately adjacent to one another, i.e.
without a space between the converter and the semiconductor layer
sequence. "Adjacent to one another" particularly includes the case
where the semiconductor layer sequence and the converter are
arranged spaced apart from one another on the carrier substrate
surface, i.e. not immediately adjacent.
[0036] In another embodiment provision can be made that the
semiconductor layer sequence and the converter are each arranged
adjacent to one another on a dedicated carrier substrate surface,
i.e. are arranged particularly immediately or not immediately
adjacent to one another.
[0037] According to a further embodiment provision can be made that
the scattering body is arranged at least on one of the two
respective surfaces of the semiconductor layer sequence and of the
converter opposite the carrier substrate surface. That is to say
particularly that the scattering body can be disposed on the
surface of the semiconductor layer sequence, which is opposite the
carrier substrate surface. The scattering body is preferably
arranged on the surface of the converter, which is opposite the
carrier substrate surface. In particular, the scattering body is
arranged both on the surface of the semiconductor layer sequence,
which is opposite the carrier substrate surface, and also on the
surface of the converter, which is opposite the carrier substrate
surface. The embodiments mentioned above and hereinunder are valid
regardless of whether the semiconductor layer sequence and the
converter are arranged on a common or on a respective dedicated
carrier substrate surface.
[0038] The surface of the semiconductor layer sequence, which is
opposite the carrier substrate surface, can particularly be
designated as a semiconductor layer sequence surface. The surface
of the converter, which is opposite the carrier substrate surface,
can, for example, be designated as a converter surface.
[0039] By reason of the fact that the scattering body is arranged
on the converter surface, it is advantageously achieved that a
majority of the scattered radiation can also reach the converter,
which considerably increases efficiency or effectiveness.
[0040] By reason of the fact that the scattering body is arranged
on the semiconductor layer sequence surface, it is advantageously
achieved that a majority of the radiation emitted by the emitter
layer reaches the scattering body and so a majority of the emitted
radiation is also scattered. This can advantageously increase
effectiveness.
[0041] According to a further embodiment provision can be made that
the scattering body is arranged as an encapsulation on the carrier
substrate surface with the semiconductor layer sequence and the
converter. That is to say particularly that the scattering body
encapsulates the carrier substrate surface with the semiconductor
layer sequence and the converter.
[0042] In another embodiment provision can be made that the
scattering body is formed as a protective layer which is arranged
on the respective surfaces of the individual elements.
[0043] Preferably, the encapsulation or the protective layer can be
of a rectangular or semi-circular form.
[0044] By the provision of an encapsulation or of a protective
layer the encapsulated or coated elements can advantageously be
protected against external influences, for example, mechanical
stresses or chemical influences. A service life of a corresponding
optoelectronic device can therefore advantageously be
increased.
[0045] According to a further embodiment provision can be made that
the scattering body comprises a non-scattering region to emit a
minimum intensity of a non-converted electromagnetic radiation. The
region which scatters the radiation is particularly designated as a
scattering region. A plurality of non-scattering regions can
preferably be formed which can be formed, in particular,
identically or preferably differently.
[0046] By the provision of a non-scattering region it is
advantageously achieved that the scattering body does not scatter a
certain portion of electromagnetic radiation which was generated by
the emitter layer, but rather lets it pass through and so the
optoelectronic device constantly radiates a minimum intensity of
electromagnetic radiation. The non-scattering region is preferably
formed from the matrix material, wherein the matrix material is
then free of embedded scattering particles. Provision can
preferably be made that the non-scattering region is formed from a
matrix material different from the matrix material of the
scattering region.
[0047] According to a further embodiment provision can be made that
the non-scattering region is arranged on at least one of the two
respective surfaces of the semiconductor layer sequence and of the
converter. That is to say particularly that the non-scattering
region is arranged on the semiconductor layer sequence surface
and/or on the converter surface. The scattering region or regions
are then preferably arranged on the corresponding free surfaces on
which the non-scattering regions are not arranged.
[0048] A scattering region particularly designates a region in
which scattering can take place. The scattering region thus
particularly comprises a positive temperature-dependent scattering
cross-section. The scattering region particularly comprises a
matrix material with embedded scattering particles. In this
respect, the non-scattering region particularly comprises only a
matrix material without embedded scattering particles, i.e. it is
free of scattering particles. A plurality of scattering regions are
preferably formed which can in particular be identical or
preferably different.
[0049] According to a further embodiment provision can be made that
the emitter layer is formed as a converter layer for converting
electromagnetic radiation with a third wavelength into
electromagnetic radiation with a fourth wavelength different from
the third wavelength and that the semiconductor layer sequence
comprises an active zone for producing electromagnetic radiation
which can be at least partially converted by the converter
layer.
[0050] That is to say particularly that first a primary radiation
is formed in the active zone of the semiconductor layer sequence,
which, prior to a radiation from the optoelectronic device, is at
least partially, in particular wholly, converted by the converter
layer. For example, provision can be made that the active zone
produces ultraviolet to blue light which is then converted in the
converter layer at least partly, in particular wholly, into green
light. A wavelength of the converted radiation can preferably be
greater than a wavelength of the primary radiation.
[0051] Ultraviolet in terms of the present invention designates
particularly a wavelength range between 230 nm and 400 nm.
Preferably, an active zone, a converter layer, a converter and/or
an emitter layer can then each comprise a diamond (C), aluminium
nitride (AlN), aluminium gallium nitride (AlGaN), aluminium gallium
indium nitride (AlGaInN) or a combination of the above-mentioned
materials.
[0052] Violet in terms of the present invention designates
particularly a wavelength range between 400 nm and 450 nm. Violet
can particularly also designate only the wavelength of 450 nm. An
active zone, a converter layer, a converter and/or an emitter layer
can then preferably also each comprise indium gallium nitride
(InGaN).
[0053] Blue in terms of the present invention designates
particularly a wavelength range between 450 nm and 500 nm. An
active zone, a converter layer, a converter and/or an emitter layer
can then preferably each comprise zinc selenide (ZnSe), indium
gallium nitride (InGaN), silicon carbide (SiC), zinc oxide (ZnO),
silicon (Si) as a carrier or a combination of the above-mentioned
materials.
[0054] Green in terms of the present invention designates
particularly a wavelength range between 500 nm and 570 nm. An
active zone, a converter layer, a converter and/or an emitter layer
can then preferably each comprise InGaN, gallium nitride (GaN),
gallium phosphide (GaP), aluminium-gallium-indium-phosphide
(AlGaInP), aluminium-gallium-phosphide (AlGaP), zinc oxide (ZnO) or
a combination of the above-mentioned materials.
[0055] Yellow in terms of the present invention designates
particularly a wavelength range between 570 nm and 590 nm. An
active zone, a converter layer, a converter and/or an emitter layer
can then preferably each comprise gallium arsenide phosphide,
aluminium-gallium-indium-phosphide (AlGaInP), gallium phosphide
(GaP) or a combination of the above-mentioned materials.
[0056] Orange in terms of the present invention designates
particularly a wavelength range between 590 nm and 610 nm. An
active zone, a converter layer, a converter and/or an emitter layer
can then preferably each comprise GaAsP, AlGaInP, GaP or a
combination of the above-mentioned materials.
[0057] Red in terms of the present invention designates
particularly a wavelength range between 610 nm and 760 nm. An
active zone, a converter layer, a converter and/or a emitter layer
can then preferably each comprise aluminium-gallium-arsenide
(AlGaAs), gallium arsenide phosphide (GaAsP),
aluminium-gallium-indium-phosphide (AlGaInP), gallium phosphide or
a combination of the above-mentioned materials.
[0058] Infrared in terms of the present invention designates
particularly a wavelength range greater than 760 nm. An active
zone, a converter layer, a converter and/or an emitter layer can
then preferably each comprise AlGaAs, GaAs or a combination of the
above-mentioned materials.
[0059] Where a wavelength is generally mentioned previously or
hereinunder, this wavelength can then be particularly in a
wavelength range from ultraviolet to infrared.
[0060] According to a further embodiment provision can be made that
the active zone is formed to produce electromagnetic radiation in a
wavelength range from 230 nm to 500 nm, particularly from 400 nm to
500 nm, preferably 450 nm to 500 nm. The converter layer is
preferably formed to convert at least some of the produced
radiation into electromagnetic radiation in a wavelength range from
500 nm to 570 nm. The converter is preferably formed to convert the
radiation converted by the converter layer into electromagnetic
radiation with a wavelength of greater than 610 nm.
[0061] That is to say particularly, that in the active zone,
particularly ultraviolet to blue light is first produced, which is
converted into green light in the converter layer. The green
radiation is then converted into red radiation in the converter.
Therefore in an advantageous manner, a decrease in the red light in
a luminous flux caused by an increasing temperature during
operation of the optoelectronic device can advantageously be
compensated for, this red light is emitted, for example, by an
appropriately formed further device. A chromaticity coordinate
shift into red can advantageously be compensated for.
[0062] In a further embodiment, a plurality of converters can be
formed. The converters can preferably be the same or, in
particular, different.
[0063] The above-described properties, features and advantages of
this invention and the manner in which they are achieved will
become more clearly and explicitly understandable in conjunction
with the following description of the exemplified embodiments which
are explained in more detail in conjunction with the drawings in
which:
[0064] FIG. 1 shows an optoelectronic device;
[0065] FIG. 2 shows a chromaticity coordinate shift;
[0066] FIGS. 3 and 4 show spectra of different dyes which can be
used for emitter layers, converters, converter layers and active
zones, and corresponding overlaid spectra;
[0067] FIG. 5 shows an RGB system;
[0068] FIGS. 6 to 8 show further RGB systems;
[0069] FIG. 9 shows a comparison of two chromaticity coordinate
shifts in a known optoelectronic device and in an optoelectronic
device in accordance with the invention;
[0070] FIG. 10 shows a spectral shift in a known optoelectronic
device;
[0071] FIG. 11 shows a spectral shift in an optoelectronic device
in accordance with the invention;
[0072] FIG. 12 shows absorption curves of phosphors; and
[0073] FIG. 13 shows a graphical illustration of a dependency of
the refraction index of silicone upon a wavelength.
[0074] Hereinunder like features can be designated by like
reference numerals.
[0075] FIG. 1 shows an optoelectronic device 101.
[0076] The optoelectronic device 101 comprises a semiconductor
layer sequence 103 comprising a plurality of layers 103a, 103b and
103c. The semiconductor layer 103b is formed between the two
semiconductor layers 103a and 103c and is arranged directly
adjacent to them. The semiconductor layer 103b is formed in the
optoelectronic device 101 as an emitter layer 105. That is to say
particularly that the emitter layer 105 is formed to emit
electromagnetic radiation. In this case provision can preferably be
made that the two semiconductor layers 103a and 103c are n-doped
and p-doped semiconductor layers. The emitter layer 105 emits the
electromagnetic radiation 107 as symbolically indicated in FIG. 1
by an arrow with the reference numeral 107.
[0077] The emitted electromagnetic radiation 107 at least partially
reaches a scattering body 109. The scattering body 109 scatters at
least some of the electromagnetic radiation 107, which is emitted
by the emitter layer 105, in the direction of a converter 113. This
scattered light is symbolically indicated in FIG. 1 by an arrow
with the reference numeral 111.
[0078] The converter 113 converts the scattered electromagnetic
radiation 111 into an electromagnetic radiation which at least
partly has a wavelength range different from the scattered
radiation 111. The converted electromagnetic radiation which is
then radiated by the converter 113 is symbolically indicated in
FIG. 1 with an arrow with the reference numeral 115.
[0079] In the optoelectronic device 101, the scattering body 109
has a positive temperature-dependent scattering cross-section and
so, as the temperature increases, a scattering of the
electromagnetic radiation in the scattering body 109 in the
direction of the converter 113 increases.
[0080] That is to say particularly that while a temperature is
increasing, the scattering in the scattering body 109 increases and
so electromagnetic radiation is increasingly scattered in the
direction of the converter 113. That is to say particularly that in
the case of an increase in the temperature, a portion of the
electromagnetic radiation 107 emitted by the emitter layer 105 is
converted by the converter 113.
[0081] In this case provision is preferably made that the
scattering body 109 at ambient temperature, particularly 300 K, is
transparent for the emitted electromagnetic radiation 107 of the
emitter layer 105. Only as the temperature increases, i.e., for
example, during operation of the optoelectronic device 101, does
the scattering cross-section in the scattering body 109 increase
and so then light and/or electromagnetic radiation is then
increasingly scattered in the direction of the converters 113.
[0082] In an embodiment which is not shown, provision can be made
that the emitter layer 105 is formed as a converter layer and is
preferably arranged as the last semiconductor layer on the top of
the semiconductor layer sequence 103. Instead of the semiconductor
layer 103b an active zone is then preferably provided which can
also emit electromagnetic radiation. This emitted radiation,
however, then radiates first into the converter layer and is
converted therein. Only this converted light is then at least
partly radiated in the direction of the scattering body 109.
[0083] For example, provision can be made that the active zone
emits blue light, wherein then the converter layer is formed
particularly to convert the blue light into green light. This green
light is then particularly at least partly scattered by the
scattering body 109 in the direction of the converter 113.
Provision is then preferably made that the converter 113 is formed
to convert the green light into red light. For example, for this
purpose the converter 113 can comprise a phosphor compound.
[0084] In fact it is generally the case that optoelectronic devices
such as, for example, light-emitting diodes, are normally operated
at different temperatures. For example, at switch-on, an active
zone or an emitter layer of the optoelectronic device is generally
at ambient temperature, for example room temperature, for example
300 K. During a warm-up phase, the duration of which is dependent,
for example, on the thermal resistances of the optoelectronic
device and particularly dependent on a coupling to an optionally
present heat sink which can be provided, a temperature of the
active zone or of the emitter layer normally increases. This
continues until normally a stable temperature is reached at a
stationary operating point. This process normally takes place
within a period of the first 10 to 30 minutes after switch-on.
After the warm-up phase the temperature is generally particularly
between ca. 75.degree. C. and 125.degree. C., wherein at the
stationary operating point the temperature can also be, for
example, above 150.degree. C.
[0085] In the case of material systems used for optoelectronic
devices, a light flux or a radiation flux typically changes
particularly in dependence upon the temperature, particularly in
the presence of a constant, temperature-independent current. Higher
operating temperatures generally lead to a decrease in the light
flux. For example, for semiconductor layer sequences based on InGaN
a light flux at 100.degree. C. is usually, for example, ca. 85% of
the light flux at 25.degree. C. In the case of semiconductor layer
sequences based on InGaAlP this effect is generally somewhat more
pronounced, particularly also since the emission wavelength is
shifted out of a range of higher eye sensitivity. Thus in the case
of a semiconductor layer sequence based on InGaAlP and emitting in
the yellow spectral range, the brightness at 100.degree. C. can
decrease to ca. 40% of the value at 25.degree. C. In the case of an
emission in the red wavelength range, this decrease can be about
50% with respect to the brightness sensed by the human eye.
[0086] This temperature-dependency of the light flux can cause
problems during use. For example, in the case of blinking lights or
rear lights in automobiles a specific preset light flux is
generally to be achieved. If the optoelectronic devices used, such
as, for example, light-emitting diodes, are cold, i.e., for
example, close to room temperature, they will generally shine too
brightly. In the case of general illumination in workspaces,
greenish-white-emitting optoelectronic devices with a plurality of
semiconductor layer sequences are particularly used which emit
particularly in the red, green, blue and/or yellow wavelength range
and so the corresponding spectra can be combined with one another.
In the case of such a combination of differently emitting
semiconductor layer sequences and the comparatively strong decrease
in the light flux--which accompanies the increasing temperature--of
the red-emitting semiconductor layer sequence and possibly the
yellow-emitting semiconductor layer sequence, strong colour changes
can occur, i.e. a shift in the chromaticity coordinate.
[0087] For example, the correlated colour temperature changes by
about 600 K from ca. 2400 K at room temperature to 3000 K at the
stationary operating point of the optoelectronic device at ca.
100.degree. C. Thus after switch-on, red-tinged light is emitted
before, after ca. 10 minutes to 30 minutes, the desired light
colour is achieved. Furthermore, such temperature-dependent colour
changes which extend over relatively long time periods, can cause
problems in the case of back-lighting, for example, for liquid
crystal displays.
[0088] The explanations above relating to a chromaticity coordinate
shift in the case of red-emitting semiconductor layer sequences are
caused particularly by a strong decrease in the quantum efficiency
in the case of InGaAlP.
[0089] The chromaticity coordinate shift can, for example, be
compensated for by a suitable electrical control. However, this
generally requires additional effort in driver design and therefore
leads to high additional costs for the system depending on the
precision of the compensation.
[0090] FIG. 2 graphically illustrates the above-described
chromaticity coordinate shift by light flux decrease in a red
light-emitting semiconductor layer sequence. The two lower graphs
show the emitted spectrum of a system comprising a red-, blue- and
green-emitting semiconductor layer sequence with respective
corresponding emitter layers and possibly active zones with an
associated converter layer. The left-hand graph shows the situation
at a temperature of 25.degree. C. The right-hand graph shows the
situation at a temperature of 100.degree. C. The intensity in Watts
per nanometre is plotted over the wavelength in nanometres. Above
the spectrum the colour space is illustrated, wherein this is
particularly the RGB (red, green, blue) colour space. Above these
two spectra a further spectrum is shown. In this case also, the
intensity in Watts per nanometre is plotted over the wavelength in
nanometres. The curve with the reference numeral 201 depicts the
case of a temperature of 25.degree. C. The curve with the reference
numeral 203 shows the case at a temperature of 100.degree. C. Both
spectra correspond to the red light of the red light-emitting
semiconductor layer sequence.
[0091] A strong chromaticity coordinate shift at T=100.degree. C.
is clear to see.
[0092] FIGS. 3 and 4 each show different spectra of different dyes,
as can be used for emitter layers, active zones, converters and
converter layers. Also shown are corresponding overlaid spectra
which result from the overlaying of the individual spectra.
[0093] The intensity is plotted in Watts per nanometre over the
wavelength in nanometres.
[0094] The respective curve with the reference numerals 305 and 401
depicts a spectrum of a YaG dye.
[0095] The respective curve with the reference numerals 307 and 405
depicts a spectrum for a green dye based on LuAG mixed with the
spectrum 305 or 401.
[0096] The curve with the reference numeral 403 depicts a spectrum
of a green dye based on LuAG.
[0097] The curve with the reference numeral 301 depicts a spectrum
of a green-yellow dye based on YaG mixed with a spectrum of a
principally orange--(for example, at a maximum at 606 nm) or
red-emitting dye.
[0098] The curve with the reference numeral 303 depicts a spectrum
mixed from the spectrum 307 with a spectrum of the principally
orange--(for example, at a maximum at 606 nm) or red-emitting
dye.
[0099] For the spectrum shown on the left in FIG. 3 it is
particularly the case that a temperature at the p-n-transition is
100.degree. C. and a colour reproduction index is 91 and a luminous
efficacy of radiation (LER) is =45-350 lm/W.
[0100] FIG. 5 shows an RGB system 500.
[0101] RGB in this case stands for red, green and blue. Such a
system conventionally comprises an optoelectronic device emitting
red electromagnetic radiation, blue electromagnetic radiation and
green electromagnetic radiation and so where there is an overlay of
red, blue and green, a specific chromaticity coordinate or a
specific colour temperature, for example, white light, is
produced.
[0102] The RGB system 500 comprises three optoelectronic devices
501, 503 and 505. Each of the three optoelectronic devices 501, 503
and 505 has a carrier substrate 507.
[0103] The three optoelectronic devices are preferably also each
disclosed in their own right. Thus in particular the optoelectronic
device 503 is disclosed in its own right without the two other
devices 501 and 505.
[0104] The devices 501, 503, 505 are each shown twice one above
another in two rows. The upper row describes the case where the
temperature is 25.degree. C. The lower row describes the case where
the temperature is 90.degree. C.
[0105] On a carrier substrate surface 507a of the optoelectronic
device 501 and of the optoelectronic device 505 in each case a
TiO.sub.2 silicone layer 509 is applied. In the device 501 the
TiO.sub.2 silicone layer 509 has a blue light-emitting active zone
511. In the optoelectronic device 505 the TiO.sub.2 silicone layer
509 comprises a red light-emitting active zone 513. A lens 515
comprising a convex shape is provided in each case on the TiO.sub.2
silicone layer 509 of the two devices 501 and 505. The lens 515
preferably comprises a silicone as its material.
[0106] During operation of the two devices 501 and 505 the device
501 thus emits blue light. The device 505 emits red light. By
reason of an increasing temperature, however, there will normally
be a decrease in light flux in the device 505 which emits red
light.
[0107] Emission of red light is symbolically shown by arrows
designated with the reference numeral 519. The reference numeral
517 designates arrows with respect to the device 501, which are
intended to show the emission of blue light.
[0108] The optoelectronic device 503 has a blue light-emitting
active zone 521 on the carrier substrate surface 507a, on which
zone a converter layer 523 is applied which can convert the blue
light of the active zone 521 into green light. The green light then
emitted is in this case designated by arrows designated by the
reference numeral 527. The converter layer 523 can preferably
comprise an LuAG-ceramic converter material.
[0109] Also disposed on the carrier substrate surface 507a are two
converters 529 which are disposed left and right of the active zone
521 and adjacent thereto. In this case the two converters 529
comprise a phosphor compound which ensures that the converters 529
can convert the green light 527 into red light when the green light
527 reaches them.
[0110] A scattering body 525 is disposed on the converters 529 and
on the converter layer 523 and in this case is preferably formed as
a collecting lens comprising a convex shape. In a form which is not
shown, other shapes for the scattering body are possible. That is
to say particularly that the embodiment described in FIG. 5 should
not be limited to collecting lenses comprising a convex shape.
[0111] The collecting lens 525 comprises a positive
temperature-dependent scattering cross-section and so, as the
temperature increases, the scattering body 525, i.e. in this case
the collecting lens, can scatter light.
[0112] During operation of the of the optoelectronic device 503
this has the advantageous effect that the green light 527 is
strongly scattered, preferably in the direction of the converters
529. As the temperature increases, these thus increasingly convert
the green light 527 into red light, which is then radiated from the
converters 529. The converted light is in this case depicted with
arrows with the reference numeral 531. This is illustrated by way
of example in this case at a temperature of 90.degree. C.
[0113] Since the green light 527 is generally not wholly scattered,
some of the green light continues to be radiated outwards by the
collecting lens 525. Red light 531 is radiated at the same
time.
[0114] This converted red light 531 compensates for the loss of red
light 519 which the optoelectronic device 505 comprises.
[0115] That is to say particularly that a return of the emission
from the optoelectronic device 505, which directly radiates red
light, can be compensated for by an additional emission of the
green-red converted light 531 from the optoelectronic device
503.
[0116] That is to say particularly that a simple optical
compensation of the chromaticity coordinate drift or the
chromaticity coordinate shift can be achieved in that via a
temperature-activated scattering, namely by the scattering body
525, the green light 527 is converted into red light 531 at least
partly or more strongly as the temperature increases. In this way
the loss of red light by thermal quenching processes in the device
505 is advantageously compensated for by means of a change in the
red-green ratio, whereby in the radiated full spectrum of the RGB
system 500, the chromaticity coordinate can be stabilised.
[0117] Thus an almost complete optical compensation of the
chromaticity coordinate shift is thereby effected by a purely
passive optical apparatus, in this case the scattering body with
the positive temperature-dependent scattering cross-section and so
advantageously no additional electric compensation is required.
This simplifies the RGB system 500 considerably. In the case where
the individual components are of suitable optical quality a
stabilisation can be carried out with no effect on efficiency.
[0118] The scattering body 525 preferably comprises as a matrix
material a silicone, in which scattering particles, for example,
SiO.sub.2, are embedded. In this case at room temperature,
particularly at 300 K, the scattering particles comprise
approximately the same refraction index as the matrix material, in
this case, for example, silicone. This advantageously means that at
this temperature, i.e. room temperature, particularly 300 K, no
optical contrast between the scattering particles and the matrix
material is provided. This advantageously means that
electromagnetic radiation can propagate unhindered through the
scattering body 525 and in this respect can be coupled out.
[0119] At a higher temperature the refraction number of the matrix
material changes more strongly than that of the scattering
particles and so a difference between the individual refraction
indices increases. Stronger optical scattering thereby
advantageously occurs. This scattering then advantageously leads to
the green photons being scattered onto the converter 529 disposed
next to the active blue zone 521, which converter can particularly
be formed as a red phosphor layer and so these photons can then be
converted into red photons. This advantageously leads to a shift of
the spectrum of the originally green-emitting device 503 towards
red, whereby the strong return of the emission of the device 505
can be compensated for.
[0120] FIGS. 6, 7 and 8 each show a further embodiment of an RGB
system 600 or 700 or 800.
[0121] The RGB system 600 as shown in FIG. 6 comprises a carrier
substrate 507. Different semiconductor layers or semiconductor
layer sequences are applied to the carrier substrate surface 507a
as follows:
[0122] From left to right as seen relative to a top view a
converter 529 is first applied, wherein on the right next to the
converter 529 the active blue zone 511 is applied. On the right
next to the active blue zone 511 a further converter 529 is
applied. On the right, adjacent to the converter 529 a further blue
active zone 521 is disposed. Adjacent to this active zone 521 a
further converter 529 is applied to the carrier substrate surface
507a. Adjacent to this converter 529 a red active zone 513 is
applied. Adjacent to this red active zone 513 a further converter
529 is applied to the substrate surface 507a.
[0123] That is to say particularly that the three optoelectronic
devices 501, 503, 505 according to the system 500 as shown in FIG.
5, which in that location were still provided as individual devices
with a dedicated carrier substrate, are now formed as shown in FIG.
6 on a common carrier substrate, in this case carrier substrate
507. Analogously to the device 503, in this case the blue active
zone 521 also comprises a converter layer 523 which is disposed on
the active zone 521.
[0124] The system 600 thus emits both blue and also red and also
green light, in as far as the blue light of the zone 521 is
converted into green light by means of the converter layer 523.
[0125] Furthermore, analogously to the devices 501, 503, 505, a
collecting lens 525 is applied as a scattering body to the elements
disposed on the carrier substrate 507, wherein in contrast to FIG.
5, the collecting lens 525 is provided as a common collecting lens
for the individual light-emitting elements.
[0126] The scattering body 525 is formed analogously to the
scattering body 525 as shown in FIG. 5. Statements made in
conjunction with the system 500 of FIG. 5 with respect to the
temperature-dependent scattering apply analogously to the RGB
system 600 as shown in FIG. 6.
[0127] In this case provision can preferably be made that the
active zone 513 comprises InGaAlP. The active zone 521 and the
active zone 511 can preferably comprise InGaN. The converters 529
preferably comprise a phosphor compound.
[0128] FIG. 7 shows a further RGB system 700 which is constructed
substantially analogously to the RGB system 600 as shown in FIG. 6.
Reference may be made to the corresponding statements.
[0129] As a difference thereto the scattering body 525 in FIG. 7
comprises two non-scattering regions 701 and one scattering region
703. That is to say particularly that the region 703 comprises a
positive temperature-dependent scattering cross-section. The two
non-scattering regions 701, in contrast, are transparent for the
emitted electromagnetic radiation. In this case the scattering
region 703 is formed above the converter layer 523. The region 703
is rectangular as seen in cross-section and has a width equal to
the width of the converter layer 523. To the left and right next to
the scattering region 703 the two non-scattering regions 701 are
disposed.
[0130] In this case provision can be made that the scattering
region 703 comprises both a matrix material, for example silicone,
and scattering particles, for example silicon dioxide.
[0131] The non-scattering regions 701 preferably comprise merely a
matrix material, for example, silicone, and are in this respect
free of scattering particles. They are thus in particular free of
scattering particles. In particular, the matrix material of the
scattering region and the matrix material of the non-scattering
region can be formed from the same material, for example, dialkyl
polysiloxane. In particular, the matrix materials of the scattering
and non-scattering regions both have the same chemical
composition.
[0132] Thus when, in operation of the RGB system 700, a temperature
increases, only the scattering region 703 will at least partly
scatter back the green light emitted by the converter layer 523 in
the direction of the converter 529. Light which is emitted by the
converter layer 523 in the direction of the non-scattering regions
701 is not scattered in the direction of the converter 529. Rather,
the light penetrates the non-scattering regions 701 and is then
correspondingly coupled out of the scattering body 525.
[0133] Therefore there is advantageously always a minimum potion of
green-converted electromagnetic radiation available since a certain
part is always non-scattered and in this respect can be coupled out
in an unhindered manner.
[0134] FIG. 8 shows a further RGB system 800.
[0135] The RGB system 800 is constructed substantially analogously
to the RGB system 700 as shown in FIG. 7. Reference can be made to
the corresponding statements.
[0136] In contrast thereto, in this case the non-scattering regions
and the scattering regions are exchanged in the geometrical
arrangement.
[0137] That is to say particularly that the scattering region 703
extends or is disposed on the left and right of the non-scattering
region 701. That is to say particularly that the non-scattering
region 701 extends above the converter layer 523.
[0138] FIG. 9 shows a comparison between a chromaticity coordinate
shift in a known optoelectronic device and an optoelectronic device
in accordance with the invention.
[0139] The coordinates Cy and Cx of the RGB colour space are
plotted. The reference numeral 901 designates the position which
the chromaticity coordinate of the respective optoelectronic device
comprises at a temperature of 25.degree. C. The reference numeral
903 designates the position which the chromaticity coordinate of
the optoelectronic device in accordance with the invention
comprises at a temperature of 90.degree. C. That is to say
particularly that this optoelectronic device comprises a scattering
body with a positive temperature-dependent scattering cross-section
and a correspondingly disposed converter.
[0140] The reference numeral 905 designates the position of a
chromaticity coordinate at a temperature of 90.degree. C. in an
optoelectronic device according to the prior art, in which no
compensation of the chromaticity coordinate shift has taken
place.
[0141] FIG. 10 shows a spectral shift.
[0142] The intensity in Watts per nanometre is plotted over the
wavelength in nanometres.
[0143] The reference numeral 1001 designates the spectrum of a red
light-emitting semiconductor layer sequence at a temperature of
25.degree. C. The reference numeral 1003 designates the
corresponding spectrum at a temperature of 90.degree. C. By reason
of the increased temperature it is clear to see the shift of the
spectrum, which leads to a corresponding chromaticity coordinate
shift.
[0144] FIG. 11 shows a spectral shift in an optoelectronic device
in accordance with the invention.
[0145] The intensity in Watts per nanometre is plotted over the
wavelength in nanometres.
[0146] The reference numeral 1101 designates the spectrum of the
red light-emitting semiconductor layer sequence at a temperature of
25.degree. C. The reference numeral 1103 designates the
corresponding spectrum at a temperature of 90.degree. C. The reason
for the greater shift towards red in some wavelength ranges
compared to the spectral shift shown in FIG. 10 is particularly
that in this case an increased phosphor concentration is provided
in the converter.
[0147] FIG. 12 shows absorption curves of different red
phosphors.
[0148] The absorption in random units is plotted over a wavelength
in nanometres.
[0149] The region designated by the reference numeral 1201 shows
the wavelength range in which the LuAG preferentially absorbs
photons. This is in this case particularly a green wavelength
range.
[0150] The reference numerals 1203 and 1205 designate corresponding
absorption curves for 2 possible phosphor compounds.
[0151] Such phosphor compounds can, for example, comprise Eu-doped
CaAlSiN.
[0152] FIG. 13 shows a dependency of a refraction index of a
silicone over a wavelength.
[0153] The refraction index n is plotted over the wavelength in
nanometres.
[0154] The reference numeral 1301 designates the course at a
temperature of 25.degree. C.
[0155] The reference numeral 1303 designates the course at a
temperature of 120.degree. C.
[0156] In this case, for silicone dn/dT.apprxeq.3.2e-4.
[0157] A change to the refraction index in dependence upon the
temperature for SiO.sub.2 is about dn/dT.apprxeq.5e-6.
[0158] There follows an exemplified calculation for the change to
the corresponding refraction index at a temperature of 25.degree.
C. and 125.degree. C.
[0159] n in this case designates the refraction index.
[0160] At a temperature of 25.degree. C., a refraction index of
silicon dioxide is 1.4600. The refraction index of silicone at a
temperature of 25.degree. C. is 1.410.
[0161] That is to say particularly that a difference in the
refraction index is 0.05.
[0162] At a temperature of 125.degree. C. a refraction index of
silicon dioxide is 1.4595. A refraction index of silicone at a
temperature of 125.degree. C. is 1.377.
[0163] That is to say particularly that a difference in refraction
index at a temperature of 125.degree. C. is 0.0825.
[0164] That is to say particularly that as the temperature
increases, the difference in the refraction index increases. This
means particularly that the scattering increases
correspondingly.
[0165] Polysiloxane or subgroups can preferably be provided as
silicone. For example, methylene side groups can be provided,
particularly phenylene side groups can be provided.
[0166] In an embodiment which is not illustrated, provision can be
made that the converter layer 523 which converts red light into
green light, has a thickness of between 50 .mu.m and 400 .mu.m.
[0167] A thickness of the converter 529 which converts the green
light into red light is particularly between 100 .mu.m and 500
.mu.m.
[0168] Preferably a weight concentration of phosphor or of a
phosphor compound in the converter 529 can be between 5 wt. %
(percent by weight) and 80 wt. %.
[0169] SiO.sub.2 can be provided, for example, as the matrix
particles. A particle size can be between 200 .mu.m and 10,000
.mu.m.
[0170] The scattering particles, in this case, for example, the
silicon dioxide, can, for example, be formed as ground glass,
particularly ground glass with a correspondingly adapted refraction
index. That is to say that glass can be ground in order to produce
the scattering particles.
[0171] In summary, therefore, the invention particularly comprises
the idea of providing a scattering body with a positive
temperature-dependent scattering cross-section, which, at an
increasing temperature, increasingly scatters electromagnetic
radiation in the direction of a converter and so the scattered
light can then be converted by the converter.
[0172] In corresponding RGB systems therefore, for example, a
chromaticity coordinate shift can advantageously be compensated
for. This requires in particular no complex electrical control for
a compensation of a chromaticity coordinate shift, which leads to
lower costs and less complexity in production.
[0173] Although the invention was described and illustrated in
detail using the preferred exemplified embodiments, the invention
is not limited by the examples disclosed and other variations may
be derived therefrom by the person skilled in the art without
departing from the scope of protection of the invention.
* * * * *