OPTOELECTRONIC COMPONENT AND METHOD FOR INCREASING CONTRAST BETWEEN EMISSORS OF AN OPTOELECTRONIC COMPONENT AND METHOD FOR CHANGING CONTRAST BETWEEN EMISSORS OF AN OPTOELECTRONIC COMPONENT

Abstract

Optoelectronic component (1) comprising - a semiconductor chip (2) with a plurality of emitters (3) which are independently configured to emit primary radiation in a main radiation direction in a first operating state (4) and not to emit primary radiation in a second operating state (5), and - an absorber (6) which is arranged downstream of the emitters (3) in the main radiation direction, wherein - the absorber (6) in first regions (7), which are assigned to emitters (3) in the first operating state (4), has a lower absorption coefficient than in second regions (8), which are assigned to emitters (3) in the second operating state (5), a conversion layer (9) is arranged in the main emission direction on at least one emitter (3) of the semiconductor chip (2), and wherein the absorber (6) is embedded in particle form in the conversion layer (9), or the absorber (6) is located in an absorber layer (10), wherein the absorber layer (10) is arranged in the main radiation direction on a side of the conversion layer (9) facing away from the semiconductor chip (2), and wherein the absorber layer (10) is electrically contacted.

Description

[0001] The documents DE 10 2013 101 530 A1, US 2016 / 0072029 A1, EP 2 331 870 A2 and US 8 455 808 B1 describe components.

[0002] The publication Mou et al., Nanoscale, 12, 2020, 9, 5374-5379 describes optical absorbers.

[0003] One problem to be solved is to specify an optoelectronic device that exhibits increased contrast between the device's emitters. Another problem to be solved is to specify a method for increasing contrast as well as a method for changing the contrast between the emitters of an optical device.

[0004] The problems are solved by an optoelectronic component as well as by a method for increasing the contrast between emitters of an optoelectronic component and a method for changing the contrast between emitters of an optoelectronic component according to the independent claims.

[0005] An optoelectronic component is specified. This optoelectronic component is a radiation-emitting optoelectronic component.

[0006] The optoelectronic device comprises a semiconductor chip with a plurality of emitters. In particular, the semiconductor chip is a monolithic light-emitting diode (LED) structured into a plurality of emitters. A structured light-emitting diode can also be referred to as a pixelated LED. For example, the semiconductor chip is a monolithic InGaN LED, a monolithic InGaAlP LED, a monolithic InGaAs LED, or a monolithic GaInNAs LED. The semiconductor chip comprises at least two emitters, in particular at least 10 emitters, preferably at least 100 emitters, for example, 1024 emitters or 25400 emitters.

[0007] The emitters are independently configured to emit primary radiation in a main radiation direction in a first operating state and to emit no primary radiation in a second operating state. Here and in the following, "no" primary radiation emission is also understood to mean emission that is "only negligible" or "imperceptible to an external observer." In other words, an emitter is active in the first operating state and an emitter is inactive in the second. During operation of the optoelectronic device, the operating state of an emitter can be changed independently of the operating states of the other emitters, for example, depending on an applied voltage. For instance, it is possible to switch an emitter between the first and second operating states independently of the other emitters of the semiconductor chip.In particular, the emitters can exhibit other operating states.

[0008] Primary radiation is electromagnetic radiation of a first wavelength range. In particular, each emitter can emit primary radiation of a first wavelength range independently of the other emitters. For example, each emitter emits primary radiation in the blue wavelength range, for example in the range of 400 nm to 500 nm, or in the red wavelength range, for example in the range of 580 nm to 650 nm, independently of the other emitters.

[0009] The optoelectronic component includes an absorber positioned downstream of the emitters in the main radiation direction. In other words, the absorber is located on a radiation-emitting surface of the semiconductor chip. Here and in the following, an absorber is understood to be a material that exhibits an absorption coefficient. The absorber is designed to absorb incident electromagnetic radiation, at least partially or completely, depending on its absorption coefficient. In particular, the absorber exhibits broadband absorption. This allows the absorber to be configured to absorb electromagnetic radiation from the blue to the red wavelength range, inclusive.

[0010] The absorber exhibits a lower absorption coefficient in the first regions, which are associated with emitters in the first operating state, than in the second regions, which are associated with emitters in the second operating state. The first regions are thus associated with active emitters, and the second regions with inactive emitters. The first regions can also be referred to as active regions and the second regions as inactive regions. Accordingly, electromagnetic radiation of high intensity is coupled out from the first regions, whereas no electromagnetic radiation or electromagnetic radiation of low intensity is coupled out from the second regions. In particular, electromagnetic radiation of low intensity, generated by the emitters in the first operating state and scattered from the first regions into the second regions, can be coupled out from the second regions.

[0011] Areas assigned to emitters do not necessarily encompass the emitters' area alone. They can also include adjacent regions where the effect of the emitter's operating state can be observed. Similarly, areas can be smaller than the emitters' area alone. For example, a first area assigned to an emitter in its first operating state can also include adjacent sub-areas of neighboring emitters in their second operating state, where the scattered radiation from the first emitter's area intersects. For the same reason, a second area assigned to an emitter in its second operating state can be smaller. In particular, the first areas are larger than the area of ​​the assigned emitters, and the second areas are smaller than the area of ​​the assigned emitters.

[0012] The absorber has a lower absorption coefficient in the first region than in the second. Therefore, radiation is absorbed less strongly in the first region than in the second. The first region, i.e., regions of high intensity, experiences little attenuation, whereas the second region, with lower intensity, is attenuated more strongly. This allows the contrast between active and inactive emitters to be increased.

[0013] The optoelectronic device comprises a semiconductor chip with a plurality of emitters, each independently configured to emit primary radiation in a main emission direction in a first operating state and not to emit primary radiation in a second operating state, and an absorber located downstream of the emitters in the main emission direction, wherein the absorber has a lower absorption coefficient in the first regions associated with emitters in the first operating state than in the second regions associated with emitters in the second operating state.

[0014] The following considerations, among others, underlie the design of this optoelectronic component: Contrast is a crucial product characteristic for pixelated LEDs. The precise definition of contrast varies depending on the application and product; generally, contrast is defined as the ratio between the luminance of an active area and the luminance of an inactive area. An absorber with a lower absorption coefficient in the former than in the latter results in low attenuation of high-intensity areas and greater attenuation of low-intensity areas. This significantly increases the contrast between individual emitters. The absorber can also lead to a separation or decoupling of the emitters.

[0015] In particular, the component described here enables good channel separation of small emitters in a monolithic LED without a grid. When a grid is used, light striking the grid is either absorbed or reflected, which, in combination with the other components of the device, leads to a significant loss of efficiency. Since a grid's effect is primarily felt at the emitter edges, the edge-to-area ratio plays a crucial role. While channel separation of individual emitters can also be achieved in principle using discrete LEDs, the emitter size and spacing are limited to feature sizes of 50–100 µm by the package design and backend manufacturing processes.

[0016] Advantageously, the component described here can achieve a contrast improvement of approximately 20% to 40%, independent of the emitter size and dependent only on the absorber concentration or the absorber layer thickness. Furthermore, its compatibility with existing backend processes is beneficial. The absorber described here allows the contrast to be adjusted at the expense of the component's brightness, which is advantageous for process control and manufacturing, thus avoiding the need for contrast binning. Moreover, it can be advantageous to control the component brightness without additional effort or cost. For example, it may be necessary to significantly dim a component designed for very high brightness levels, such as in headlights, for indoor use without drastically altering its current-voltage characteristics.

[0017] Advantageously, the contrast of the component described here can also be adjusted after the component has been manufactured, for example, during operation. Thus, the contrast between individual emitters of the component can be adjusted depending on the emitter's operating state, thereby increasing the contrast between active and inactive emitters.

[0018] According to at least one embodiment, the absorber is a saturable absorber. A saturable absorber is a passive optical switching element. A saturable absorber is characterized in that its absorption coefficient is intensity-dependent. In particular, the material of a saturable absorber becomes transparent to electromagnetic radiation when a threshold value of photons is reached. Saturable absorbers whose threshold has been reached remain transparent to electromagnetic radiation at least as long as the threshold value of photons is exceeded. If the threshold value of photons is undershot, the absorption of the saturable absorber increases again after a relaxation period. The saturable absorbers are then once again opaque or less transparent to electromagnetic radiation.

[0019] According to at least one embodiment, the absorption coefficient of the saturable absorber decreases with increasing intensity of electromagnetic radiation. The electromagnetic radiation can be the primary radiation of the semiconductor chip or secondary radiation that is at least partially different from the primary radiation of the semiconductor chip. The secondary radiation can be wavelength-converted primary radiation, generated, for example, by a conversion agent such as a phosphor arranged in the optoelectronic device. The absorption coefficient of the saturable absorber decreases with the excitation intensity of the electromagnetic radiation. In other words, the more intense the incident electromagnetic radiation, i.e., the higher the photon count, the less a saturable absorber absorbs.Photons in a first region, associated with active emitters, are therefore absorbed with a lower probability than photons in a second region, associated with inactive emitters. This behavior leads to an improvement in the contrast between the first and second regions.

[0020] According to at least one embodiment, the saturable absorber is graphene or a semiconductor material such as GeSbTe, GaN, or InGaN. According to at least one embodiment, the saturable absorber is selected from the group consisting of graphene, GeSbTe, GaN, InGaN, and combinations thereof.

[0021] According to at least one embodiment, the absorber is a phase change material. A phase change material (PCM) is characterized by a crystallization temperature and / or glass transition temperature in the range of 100 °C to 300 °C, particularly in the range of 100 °C to 200 °C, preferably 150 °C. In particular, a phase change material exhibits both a crystallization temperature and a glass transition temperature in the range of 100 °C to 300 °C, particularly in the range of 100 °C to 200 °C, preferably 150 °C. The crystallization temperature can be adjusted via the composition of the phase change material, in particular a ternary compound. A phase change material exhibits a very fast phase transition in the nanosecond range and / or a material phase-dependent dielectric function. For example, germanium-antimony-tellurium compounds can be used as phase change materials.By using a phase-change material as an absorber, it is possible to configure the system so that a different phase exists in the first and second regions. This allows for a contrast improvement of up to 200% between the first and second regions in the visible light range.

[0022] According to at least one embodiment, the phase-change material exhibits a reversible phase transition from a crystalline phase to an amorphous phase. The phase-change material exists in the solid state, i.e., as a solid, in both the crystalline and the amorphous phases. For the purposes of this document, a crystalline phase is understood to mean that the absorber material consists of crystallized, regularly structured material and possesses both short-range and long-range order. For the purposes of this document, an amorphous phase is understood to mean that the absorber material does not have an ordered structure, but rather forms an irregular pattern and possesses only short-range order, but not long-range order. In particular, the crystalline and amorphous phases can coexist during the operation of the optoelectronic device.Thus, the phase change material can exist in both the crystalline and the amorphous phase at the operating temperature of the optoelectronic component.

[0023] The phase transition between the crystalline and amorphous phases occurs primarily when the glass transition temperature of the phase change material is exceeded. Above this temperature, the phase change material enters a melt, from which it can transition into either the crystalline or the amorphous phase. For example, the transition to the amorphous phase can occur via rapid cooling, while the transition to the crystalline phase can occur via slow cooling.

[0024] According to at least one embodiment, the phase transition is controlled thermally, in particular optically and / or electrically. The phase transition occurs by exceeding the glass transition temperature and subsequent cooling. Exceeding the glass transition temperature can be achieved by heating the phase-change material. Heating to a temperature above the glass transition temperature can occur in the nanosecond range. For example, the phase-change material is heated by the intensity of the primary radiation or by applying a voltage. For electrical switching of a phase-change material, the material must be contacted, in particular, by an electrically conductive means. Cooling of the phase-change material can then be initiated by reducing the light intensity or switching off the voltage.For example, the emitters assigned to the first areas are switched off or operated at low light intensity to achieve rapid cooling, while the emitters assigned to the second areas are operated at higher light intensity to achieve slow cooling, which can lead to the formation of crystallization nuclei.

[0025] It is also possible to control the phase transition through a combination of light intensity and current. For example, exceeding the glass transition temperature occurs electrically, while the transition to the crystalline or amorphous phase occurs optically.

[0026] According to at least one embodiment, the absorption coefficient of the phase-change material depends on the phase of the phase-change material. Phase-change materials are so-called switchable absorbers. In particular, at the power densities generated during the operation of LEDs, the absorption of the phase-change material is independent of the power density of the electromagnetic radiation and depends only on the phase structure of the respective phase of the phase-change material. This allows for uniform absorption of the electromagnetic radiation during operation of the optoelectronic component, regardless of its power density.

[0027] According to at least one embodiment, the crystalline phase has a higher absorption coefficient than the amorphous phase. In the optoelectronic device, the crystalline phase of the absorber can be arranged in the second regions and the amorphous phase in the first regions. The higher absorption coefficient of the absorber in the crystalline phase in the second regions leads to increased absorption of electronic radiation there compared to the absorber in the amorphous phase in the first regions. The photons that would be coupled out by the second region are absorbed more strongly by the crystalline state of the absorber than the photons coupled out by the first region. This allows the contrast between the emitters in the first operating state and the emitters in the second operating state to be advantageously improved.

[0028] According to at least one embodiment, the absorption coefficient of the crystalline phase is twice as high as that of the amorphous phase. As a result, the absorber in the crystalline phase exhibits twice the absorption compared to the absorber in the amorphous phase, which can advantageously improve the contrast between emitters in the first operating state and emitters in the second operating state significantly.

[0029] According to at least one embodiment, the phase-change material is selected from the group consisting of GeTe, GeSbTe, Ge₂Sb₂Te₅, GeSb₂Te₄, GeSb₄Te₇, Sb₂Te₃, VO₂, V₂O₅, AgInTe₂, InSb, and combinations thereof. These compounds have crystallization temperatures in the range of 100 °C to 300 °C, a very fast phase transition in the nanosecond range, and a material-dependent dielectric function. These compounds are absorbers of class 2, the class of phase-change materials, in particular subclasses of phase-change materials that change their absorption. With these materials, a contrast improvement on the order of 20% to 40% can be achieved, independent of the emitter size and depending only on the concentration of the absorber or the thickness of an absorber layer. Therefore, they are particularly suitable for use as absorbers in an optoelectronic device.

[0030] A conversion layer is arranged in the main emission direction on at least one emitter of the semiconductor chip. In particular, the conversion layer can be arranged on all emitters of the semiconductor chip. Alternatively, the conversion layer can be arranged on only some of the emitters. Specifically, the remaining emitters, on which the conversion layer is not arranged, can be free of a conversion layer. Alternatively or additionally, another conversion layer can be arranged on these remaining emitters or some of them.

[0031] In particular, the conversion layer has a thickness of 3 µm inclusive up to and including 150 µm, especially 100 µm inclusive up to and including 130 µm, for example 120 µm.

[0032] The conversion layer comprises at least one phosphor. In particular, the phosphor is present in the conversion layer as a ceramic or in a matrix material. A phosphor present as a ceramic is, in particular, largely free of a matrix material and / or another phosphor. Alternatively, the phosphor, especially in particle form, is embedded in a matrix material. The matrix material comprises, for example, silicone or glass.

[0033] The phosphor in the conversion layer can convert the primary radiation from the semiconductor chip completely or at least partially into electronic radiation of a second wavelength range, the secondary radiation. The conversion of primary radiation into secondary radiation is also called wavelength conversion. In particular, the secondary radiation has a wavelength range that differs at least partially from the primary radiation. For example, the phosphor converts blue primary radiation into yellow secondary radiation.

[0034] According to at least one embodiment, the conversion layer comprises a filler. The filler is in particle form with particle sizes from 1 µm up to and including 20 µm. The filler comprises, for example, TiO2, SiO2, or ZrO2. The filler serves to scatter electromagnetic radiation, in particular primary and / or secondary radiation.

[0035] According to at least one embodiment, the absorber is embedded in the conversion layer in particle form. The absorber is integrated into the conversion layer, which in this case comprises a matrix material. The absorber, like the phosphor, is embedded in the matrix material in particle form. The absorber is applied to the emitters by embedding the particle-shaped absorbers in the conversion layer in the same manufacturing step as the application of the conversion layer itself, thus allowing the use of existing processes.

[0036] According to at least one embodiment, the concentration of the absorber in the conversion layer is between 0 wt% (weight percent) and inclusive of 15 wt%, in particular between 5 wt% and 10 wt%, for example 7 wt%. Since the phase-change materials in particular exhibit very strong absorption, only a relatively small proportion of absorber in the conversion layer is necessary to achieve sufficient absorption for contrast enhancement.

[0037] According to at least one embodiment, the absorber is contained within an absorber layer. The absorber layer is present either as an alternative or in addition to the conversion layer. The absorber can be present in particle form within a matrix material in the absorber layer, or it can be produced as a homogeneous layer consisting of the absorber material, for example, by vapor deposition or sputtering. The matrix material for the absorber layer includes, for example, the matrix materials for the conversion layer mentioned above.

[0038] According to at least one embodiment, the absorber layer is arranged on the semiconductor chip in the main emission direction. In particular, no conversion layer is arranged between the absorber layer and the semiconductor chip. For example, the absorber layer is applied in direct mechanical contact with the emission surface of the semiconductor chip. In this embodiment, the electronic component specifically lacks a conversion layer. Such a configuration of the optoelectronic component enables contrast enhancement between the emitters of a monolithic pixelated LED or a pixelated semiconductor chip during primary emission.

[0039] According to at least one embodiment, the absorber layer is arranged in the main emission direction on a side of the conversion layer facing away from the semiconductor chip. The absorber layer can be in direct mechanical contact with the conversion layer. Alternatively, further layers, for example adhesive layers, can be arranged between the conversion layer and the absorber layer. In particular, the conversion layer is free of an absorber. Such a configuration of the optoelectronic device enables contrast improvement between the emitters during the emission of secondary radiation or white light.

[0040] According to at least one embodiment, the absorber layer is electrically contacted. For example, the absorber layer is electrically contacted from the component side.

[0041] By electrically contacting the absorber layer, a voltage can be applied to the absorber layer, thus enabling, for example, an electrical circuit of an absorber that has a phase change material.

[0042] According to at least one embodiment, the absorber layer has a thickness of 10 µm to 40 µm inclusive, and in particular of 10 µm to 30 µm inclusive, for example, 20 µm. The thickness of the absorber layer, especially of a homogeneous absorber layer, can influence the absorption of electromagnetic radiation. In particular, absorption increases with increasing thickness of the absorber layer. This can reduce the brightness of the component on the one hand, but also improve the contrast between the individual emitters on the other.

[0043] According to at least one embodiment, the absorber is in particle form and has a particle size between 1 µm and 20 µm. The particle size can exhibit a certain distribution. Due to these particle sizes, the absorber can also be suitable for scattering electromagnetic radiation, in particular primary and / or secondary radiation.

[0044] Furthermore, a method for increasing the contrast between emitters of an optoelectronic device is described. Preferably, the method described here is suitable and intended for use in an optoelectronic device described above. Features or embodiments described in connection with the optoelectronic device also apply to the method and vice versa.

[0045] The method for increasing the contrast between emitters of an optoelectronic device, wherein the optoelectronic device comprises a semiconductor chip with a plurality of emitters independently configured to emit primary radiation in a main emission direction in a first operating state and not to emit primary radiation in a second operating state, and an absorber arranged downstream of the emitters in the main emission direction, wherein the absorber has a lower absorption coefficient in first regions associated with emitters in the first operating state than in second regions associated with emitters in the second operating state, comprises the steps - Heating the absorber to a temperature above the glass transition temperature, - Cooling of the absorber in the first areas to a temperature below the glass transition temperature within a time t j, - Cooling the absorber in the second areas to a temperature below the glass transition temperature at time t2, where t1 < t2.

[0046] The heating of the absorber to a temperature above its glass transition temperature occurs primarily on the nanosecond scale. Above the glass transition temperature, the absorber exists in a molten state.

[0047] In particular, the structure of the absorber is influenced by the cooling rate. For example, time t1 is in the nanosecond range and time t2 in the microsecond range. Thus, the absorber cools faster in the first region than in the second. Due to the faster cooling in time t1, the absorber transitions to the amorphous phase in the first region. Due to the slower cooling in time t2, the absorber transitions to the crystalline phase in the second region. The times t1 and t2 are highly dependent on the material used. For example, for germanium-antimony telluride compounds, especially GeSbTe, a time t1 of less than 50 ns and a time t2 of approximately 0.2 µs are used. Consequently, the absorber exhibits a lower absorption coefficient in the first region than in the second.

[0048] This method allows the contrast between the emitters of the optoelectronic component to be adjusted during production or after the component has been manufactured. In particular, the method described here is reversible, allowing the contrast to be adjusted flexibly and variably to meet different requirements.

[0049] According to at least one embodiment, the absorber is a phase-change material. Phase-change materials are particularly well-suited for the method described here because they exhibit very fast phase transitions in the nanosecond range, material-phase-dependent dielectric properties, and crystallization temperatures in the range of 100 °C to 300 °C. By using a phase-change material, the method described here can achieve a contrast improvement of up to 200% in the visible light range.

[0050] According to at least one embodiment, the absorber is heated electrically to a temperature above the glass transition temperature. For this purpose, a voltage can be applied to the absorber material, in particular to the layer containing the absorber. Specifically, the applied voltage is high enough to heat the absorber to a temperature above the glass transition temperature on all emitters.

[0051] According to at least one embodiment, the absorber is heated optically to a temperature above the glass transition temperature. The primary radiation from the individual emitters can be used for this purpose. The heating is achieved via the luminous intensity of the primary radiation. This luminous intensity is higher than the luminous intensity of the emitters in the first operating state of the optoelectronic device. In particular, all emitters are operated with such a high luminous intensity that the absorber is heated to a temperature above the glass transition temperature on all emitters.

[0052] According to at least one embodiment, the absorber is heated electrically to a temperature above the glass transition temperature, and the absorber is cooled optically into the first and second regions. Thus, the phase transition is controlled by a combination of light intensity and current.

[0053] Furthermore, a method for changing the contrast between emitters of an optoelectronic device is described. Preferably, the method described herein is suitable and intended for use in an optoelectronic device as described above. Features or embodiments described in connection with the optoelectronic device or the method for increasing the contrast between emitters of an optoelectronic device also apply to the method for changing the contrast between emitters of an optoelectronic device, and vice versa. The method for changing the contrast can also be an additional step in the method for increasing the contrast.

[0054] The method for changing the contrast between emitters (3) of an optoelectronic device (1), wherein the optoelectronic device (1) comprises a semiconductor chip (2) with a plurality of emitters (3) which are independently configured to emit primary radiation in a main emission direction in a first operating state (4) and not to emit primary radiation in a second operating state (5), and an absorber (6) which is arranged downstream of the emitters (3) in the main emission direction, wherein the absorber (6) in first areas (7), which are assigned to emitters (3) in the first operating state (4), has a lower absorption coefficient than in second areas (8), which are assigned to emitters (3) in the second operating state (5), includes the steps - Heating the absorber (6) on at least one emitter (3) to a temperature above the crystallization temperature, - Cooling the absorber (6) on the at least one emitter (3) to a temperature below the crystallization temperature, wherein the absorption coefficient of the absorber (6) on the at least one emitter (3) is changed after cooling compared to the absorption coefficient before heating. The absorber on an emitter is the absorber that is downstream of the emitter.

[0055] The absorption coefficient of the absorber on the at least one emitter corresponds, for example, to the absorption coefficient of the absorber in the second regions before heating. After heating and cooling, the absorption coefficient can then correspond to the absorption coefficient of the absorber in the first regions. Alternatively, the absorption coefficient of the absorber on the at least one emitter can correspond to the absorption coefficient of the absorber in the first regions before heating and then to the absorption coefficient of the absorber in the second regions after heating and cooling. In particular, the absorption coefficient of a specific emitter can be selectively adjusted if the assignment of an emitter to the first or second operating state changes.

[0056] Such a method allows the contrast between individual emitters of the optoelectronic component to be modified, and in particular increased, during production or after the component's completion. Specifically, such a method allows the absorption coefficient of a specific absorber to be selectively changed without affecting the absorption coefficients of the absorbers on the other emitters.

[0057] According to at least one embodiment, the absorption coefficient of the absorber is adjusted by the cooling rate. For example, cooling occurs in the nanosecond range (t1) or in the microsecond range (t2). Faster cooling in t1 causes the absorber to transition into the amorphous phase, while slower cooling in t2 causes it to transition into the crystalline phase. The times t1 and t2 are highly dependent on the material used. For example, germanium-antimony telluride compounds, particularly GeSbTe, a t1 time of less than 50 ns and a t2 time of approximately 0.2 µs are used.

[0058] According to at least one embodiment, the absorber is a phase-change material. Phase-change materials are particularly advantageous for the method described here, since their absorption coefficients depend on the respective phase and can therefore be adjusted and thus changed by altering the phase.

[0059] According to at least one embodiment, the absorber is heated optically on at least one emitter to a temperature above the crystallization temperature. The luminous intensity of the emitter's primary radiation can be used for this purpose. This luminous intensity is higher than the luminous intensity of an emitter in the first operating state of the optoelectronic device. In particular, the emitter's luminous intensity is adjusted such that the absorber is heated to a temperature above the crystallization temperature, but not the glass transition temperature. Specifically, the heating of the absorber to a temperature above the crystallization temperature takes place on the nanosecond scale.

[0060] Further advantageous embodiments, configurations and further developments of the optoelectronic component and the method for increasing the contrast between the emitter as an optoelectronic component result from the following exemplary embodiments shown in conjunction with the figures. The Fig. Figures 1, 2 and 5 to 7 each show a schematic sectional view of an optoelectronic component according to different embodiments. The Fig. 3 and Fig. Figure 4 each shows a schematic sectional view of an optoelectronic component according to examples, and Fig. Figure 8 shows a rough estimate of the relative contrast gain over the relative brightness loss.

[0061] Identical, similar, or similarly functioning elements are marked with the same reference symbols in the figures. The figures and the relative sizes of the elements depicted within them are not to be considered to scale. Rather, individual elements, particularly layer thicknesses, may be exaggerated for clarity and / or better understanding.

[0062] The Fig. 1 and Fig. Figures 2 each show an optoelectronic device 1 according to one embodiment. The optoelectronic device 1 comprises a semiconductor chip 2 having a plurality of emitters 3. Here and in the following figures, the pixelation of the semiconductor chip 2 is represented by vertically dashed lines. The emitters 3 of the semiconductor chip 2 are independently configured to emit primary radiation during operation of the optoelectronic device 1. For example, each emitter 3 can emit primary radiation in the blue or red wavelength range.

[0063] Each emitter 3 has at least two operating states that can be set independently of the operating states of the other emitters during the operation of the optoelectronic component 1 ( Fig. 2) The emitters 3 can have a first operating state 4 (shown hatched) in which they emit primary radiation in a main radiation direction. Emitters 3 in the first operating state 4 can also be called active emitters. The emitters 3 can have a second operating state 5 in which they emit no primary radiation or primary radiation that is not perceptible to an external observer. Emitters 3 in the second operating state 5 can also be called inactive emitters.

[0064] A conversion layer 9 is arranged in the main emission direction on the emitters 3 of the semiconductor chip 2. The conversion layer 9 comprises a phosphor 11. The phosphor 11 is present in particle form within the conversion element 9. The phosphor 11 can be embedded in a matrix material, for example, silicon. The phosphor 11 is configured to convert the primary radiation emitted by the emitters 3 partially or completely into secondary radiation.

[0065] According to the exemplary embodiment of the Fig. 1 and Fig. 2. Absorber 6 is also present in the conversion element 9 in particle form. The absorber 6 is embedded in the matrix material. The absorber has a concentration of 0 wt% to 15 wt% inclusive in the conversion layer, for example, 10 wt%.

[0066] The absorber 6 is a saturable absorber or a phase-change material. In both cases, the absorber 6 exhibits a lower absorption coefficient in the first regions 7, which are assigned to emitters 3 in the second operating state 4, than in the second regions 8, which are assigned to emitters 3 in the second operating state 5. In particular, the absorber 6 exhibits a lower absorption coefficient in the first regions 7 for both primary and secondary radiation.

[0067] The effect of absorber 6 is in Fig. Figure 2 illustrates this. The absorber 6 in the first region 7 is more transparent to electromagnetic radiation than the absorber 6 in the second regions 8 due to its lower absorption coefficient. Here and in the following, the absorber 6 with a lower absorption coefficient is shown with a white fill. Due to the lower absorption coefficient of the absorber 6, the electromagnetic radiation in the first regions 7 is absorbed less strongly than the electromagnetic radiation that reaches the absorber 6 in the second regions 8, for example, as scattered radiation. Because the electromagnetic radiation in the active first regions 7 is absorbed less strongly than electromagnetic radiation in the inactive second regions 8, the contrast between the active first regions 7 and the inactive second regions 8 is improved, resulting in decoupling.Separation of the individual emitters 3 in the different operating states 4,5.

[0068] The Fig. 3 and Fig. Figure 4 shows an optoelectronic component 1 according to an example. The optoelectronic component has the same semiconductor chip 2 as the embodiment shown in Figure 4. Fig. 1 and Fig. 2. In contrast to the optoelectronic component 1 of the Fig. 1 and Fig. 2 shows the optoelectronic component 1 of the Fig. 3 and Fig. 4 no conversion layer. An absorber layer 10 is arranged in the main radiation direction on the emitters 3 of the semiconductor chip 2, in particular in direct mechanical contact.

[0069] The absorber layer 10 comprises a saturable absorber or a phase-change material. The saturable absorber or the phase-change material can be embedded in a matrix material, for example, silicone. Alternatively, the absorber layer 10 can consist entirely of the saturable absorber or the phase-change material. For example, the absorber material can be homogeneously vapor-deposited. The absorber layer 10 has a thickness of 10 µm to 40 µm inclusive, for example, 20 µm. Thus, the absorber can be applied as a thin layer to the emitters 3 of the semiconductor chip 2.

[0070] The effect of the absorber layer 10 is in Fig. Figure 4 illustrates this. The absorption coefficient of the absorber layer 10 is lower in the first regions 7 than in the second regions 8. Thus, the electromagnetic radiation emitted by an emitter 3 in the first operating state 4 is absorbed less strongly than the electromagnetic radiation reaching the absorber layer 10 in the second regions 8. Because the electromagnetic radiation from the active emitters 4 is absorbed less strongly than electromagnetic radiation in regions of the inactive emitters 5, such as scattered radiation, the contrast between the active emitters 4 and inactive emitters 5 is improved.

[0071] The Fig. 5 and Fig. Figure 6 shows an optoelectronic component 1 according to a further embodiment. In contrast to the embodiments of Fig. 1 and Fig. 3 includes the optoelectronic component 1 in the Fig. 5 and Fig. 6 a conversion layer 9 and an absorber layer 10, which are arranged in the main emission direction on the emitters 3 of the semiconductor chip 2. In particular, the absorber layer 10 is arranged in the main emission direction on a side of the conversion layer 9 facing away from the semiconductor chip 2.

[0072] The conversion layer 9 comprises a phosphor 11. The phosphor 11 is embedded in a matrix material. In particular, the conversion element can additionally contain a filler designed to scatter the primary and / or secondary radiation. Alternatively, the conversion layer 9 can consist of a ceramic of the phosphor 11 (not shown here). In particular, the conversion layer 9 can be free of an absorber.

[0073] The absorber layer 10 has the same properties as the absorber layer of the exemplary embodiment of the Fig. 3 and Fig. 4. In particular, the absorber layer 10 exhibits a lower absorption coefficient for both primary and secondary radiation in first regions 7.

[0074] Fig. Figure 7 shows the optoelectronic component 1 of the Fig. 5, in which the absorber layer 10 is additionally electrically contacted. For example, the absorber layer can be contacted from the component side (represented here by the symbol U for the applied voltage). In particular, if the absorber layer 10 comprises or consists of a phase-change material, the phase-change material can be brought into the amorphous or crystalline phase by applying a voltage. This allows the absorption coefficient of the absorber 6 to be adjusted.

[0075] The absorption coefficient of a phase change material can be adjusted as follows: First, the phase-change material is heated to a temperature above its glass transition temperature in both the first and second regions. The intensity of the primary radiation can be used to heat the phase-change material. For this purpose, all emitters are operated at a light intensity high enough that the absorber temperature exceeds the glass transition temperature. Specifically, this light intensity is higher than the light intensity during the device's operation, for example, higher than the light intensity emitted by the emitters in the first operating state. Alternatively, the phase-change material can be heated by applying a voltage to the absorber layer. This heating can occur within nanoseconds. Upon heating to a temperature above the glass transition temperature, the phase-change material melts.

[0076] The cooling of the phase-change material from the melt can then be initiated by reducing the light intensity or switching off the voltage. For example, the emitters assigned to the first range are switched off or operated at low light intensity to achieve rapid cooling, during which the phase-change material transitions into the amorphous phase. This transition to the amorphous phase can occur via cooling in the nanosecond range (t1). The emitters assigned to the second range are operated, for example, at higher light intensity to achieve slow cooling, during which crystallization nuclei can form and a transition of the phase-change material to the crystalline phase occurs. This transition to the crystalline phase can occur via cooling in the microsecond range (t2).

[0077] It is also possible to control the phase transition through a combination of light intensity and current. For example, exceeding the glass transition temperature occurs electrically, while the transition to the crystalline or amorphous phase occurs optically via light intensity.

[0078] Alternatively, the absorption coefficient of a phase-change material can also be adjusted as follows: First, the phase-change material is selectively heated on a specific emitter to a temperature above its crystallization temperature. For this purpose, the intensity of the primary radiation is used, for example. The phase-change material is then cooled by switching off the emitter or operating it at a lower intensity. Depending on how the emitter is operated, rapid cooling occurs, during which the phase-change material transitions into the amorphous phase, or slow cooling occurs, during which crystallization nuclei can form and the phase-change material transitions into the crystalline phase. For example, rapid cooling is achieved by switching off the emitter, and slow cooling by operating the emitter at a lower intensity.Thus, the absorption coefficient of the absorber can be selectively adjusted on a specific emitter.

[0079] The absorption coefficient of the absorber on the specific emitter, for example, corresponds to the absorption coefficient of the absorber in the second regions before heating. After heating and cooling, the absorption coefficient can then correspond to the absorption coefficient of the absorber in the first regions. Alternatively, the absorption coefficient of the absorber on the specific emitter can correspond to the absorption coefficient of the absorber in the first regions before heating and then to the absorption coefficient of the absorber in the second regions after heating and cooling. In particular, the absorption coefficient of a specific emitter can be selectively adjusted if the assignment of an emitter to the first or second operating state changes, without altering the absorption coefficients of the absorbers on the other emitters.

[0080] Fig.Figure 8 shows a rough estimate of the relative contrast K (in %) plotted against the relative brightness loss V (in %). It can be seen that an improvement in contrast always comes at the expense of component brightness. A 25% brightness loss results in a 50% improvement in contrast. Thus, the contrast of the electronic component can be improved at the expense of component brightness.

[0081] The features and embodiments described in connection with the figures can be combined with one another according to further embodiments, even if not all combinations are explicitly described. Furthermore, the embodiments described in connection with the figures can alternatively or additionally include further features as described in the general section. Reference symbol list 1 optoelectronic component 2 Semiconductor chips 3 emitters 4 first operating state 5 second operating state 6 absorbers 7 first area 8 second area 9 Conversion layer 10 Absorber layer U voltage

Claims

[1] Optoelectronic device (1) comprising - a semiconductor chip (2) with a plurality of emitters (3) which are independently configured to emit primary radiation in a main radiation direction in a first operating state (4) and not to emit primary radiation in a second operating state (5), and - an absorber (6) which is arranged downstream of the emitters (3) in the main radiation direction, wherein - the absorber (6) in first regions (7), which are assigned to emitters (3) in the first operating state (4), has a lower absorption coefficient than in second regions (8), which are assigned to emitters (3) in the second operating state (5), a conversion layer (9) is arranged in the main emission direction on at least one emitter (3) of the semiconductor chip (2), and wherein the absorber (6) is embedded in particle form in the conversion layer (9), or the absorber (6) is located in an absorber layer (10), wherein the absorber layer (10) is arranged in the main radiation direction on a side of the conversion layer (9) facing away from the semiconductor chip (2), and wherein the absorber layer (10) is electrically contacted. [2] Optoelectronic device (1) according to the preceding claim, wherein the absorber (6) is a saturable absorber. [3] Optoelectronic device (1) according to the preceding claim, wherein an absorption coefficient of the saturable absorber decreases with increasing intensity of electromagnetic radiation. [4] Optoelectronic device (1) according to claim 2 or 3, wherein the saturable absorber is selected from the group consisting of graphene, GeSbTe, GaN, InGaN and combinations thereof. [5] Optoelectronic device (1) according to claim 1, wherein the absorber (6) is a phase change material. [6] Optoelectronic device (1) according to the preceding claim, wherein the phase change material has a reversible phase transition from a crystalline phase to an amorphous phase. [7] Optoelectronic device (1) according to claim 6, wherein the phase transition is thermally controlled. [8] Optoelectronic device (1) according to claim 6 or 7, wherein the crystalline phase has a higher absorption coefficient than the amorphous phase. [9] Optoelectronic device (1) according to claim 8, wherein the absorption coefficient of the crystalline phase is 2 times higher than the absorption coefficient of the amorphous phase. [10] Optoelectronic device (1) according to any one of claims 6 to 9, wherein the phase change material is selected from the group consisting of GeTe, GeSbTe, Ge2Sb2Te5, GeSb2Te4, GeSb4Te7, Sb2Te3, VO2, V2O5, AgInTe2, InSb and combinations thereof. [11] Optoelectronic device (1) according to one of the preceding claims, wherein the concentration of the absorber (6) in the conversion layer (9) is between 0 wt% and inclusive 15 wt%. [12] Optoelectronic device (1) according to one of the preceding claims, wherein the absorber (6) is located in an absorber layer (10), the absorber layer (10) being arranged in the main radiation direction on the semiconductor chip (2). [13] Method for increasing the contrast between emitters (3) of an optoelectronic device (1), wherein the optoelectronic device (1) comprises a semiconductor chip (2) with a plurality of emitters (3) which are independently configured to emit primary radiation in a main emission direction in a first operating state (4) and not to emit primary radiation in a second operating state (5), and an absorber (6) which is arranged downstream of the emitters (3) in the main emission direction, wherein the absorber (6) in first areas (7), which are assigned to emitters (3) in the first operating state (4), has a lower absorption coefficient than in second areas (8), which are assigned to emitters (3) in the second operating state (5), comprehensive the steps - Heating the absorber (6) to a temperature above the glass transition temperature, - Cooling of the absorber (6) in the first areas (7) to a temperature below the glass transition temperature in a time t1, - Cooling of the absorber (6) in the second areas to a temperature below the glass transition temperature in a time t2, where t1 < t2. [14] Method for increasing the contrast between emitters (3) of an optoelectronic device (1) according to the preceding claim, wherein the absorber (6) is a phase change material. [15] Method for increasing the contrast between emitters (3) of an optoelectronic device (1) according to one of claims 13 or 14, wherein the heating of the absorber (6) to a temperature above the glass transition temperature is carried out electrically or optically. [16] Method for changing the contrast between emitters (3) of an optoelectronic device (1), wherein the optoelectronic device (1) comprises a semiconductor chip (2) with a plurality of emitters (3) independently configured to emit primary radiation in a main emission direction in a first operating state (4) and not to emit primary radiation in a second operating state (5), and an absorber (6) arranged downstream of the emitters (3) in the main emission direction, wherein the absorber (6) has a lower absorption coefficient in first regions (7) associated with emitters (3) in the first operating state (4) than in second regions (8) associated with emitters (3) in the second operating state (5), comprising the steps - Heating the absorber (6) on at least one emitter (3) to a temperature above the crystallization temperature, - Cooling the absorber (6) on the at least one emitter (3) to a temperature below the crystallization temperature, wherein the absorption coefficient of the absorber (6) on the at least one emitter (3) is changed after cooling compared to the absorption coefficient before heating.

Images