DE19747433A1 - Semiconductor LED has a reflection reducing quarter wavelength layer stack of semiconductor materials - Google Patents

Abstract

A semiconductor LED has a reflection reducing arrangement of pairs of alternate high and low refractive index lambda /4 layers consisting of an electrically conductive semiconductor material. A semiconductor LED has a reflection reducing layer arrangement which is located between a lambda -emitting optically active zone and a light output interface, between the high refractive index semiconductor material and an external low refractive index material, and which comprises pairs of a high refractive index lambda /4 layer and an overlying low refractive index lambda /4 layer, each layer having an optical thickness of one-quarter (or an odd number multiple) of the wavelength of the light waves and the uppermost lambda /4 layer, in contact with the external low refractive index material via the light output interface, being a low refractive index lambda /4 layer. The novelty is that the lambda /4 layers are arranged parallel to the active zone and consist of an electrically conductive semiconductor material.

Description

The invention relates to a light-emitting semiconductor diode according to the Preamble of claim 1.

Layer arrangements for changing, e.g. reducing, the reflection of light waves at an interface between substances with different refractive index are theoretically from Weißmantel / Haman: Basis of Solid State Physics, 2nd ed. 1981, VEB German Publishing House of Sciences, p. 708 ff . refer to. The optical layer thickness is the geometric layer thickness multiplied by the refractive index n of the substance. This should take into account the changing wavelength of light waves depending on the refractive index, because the wavelength in the medium is the wavelength in vacuum λ divided by the refractive index of the medium n _medium . The geometrical thickness d of a λ / 4 layer, as proposed by Weißmantel / Hamann, results from the formula: d = λ _vacuum / 4n _medium .

It can also be seen that with optical layer thicknesses of λ / 4 of the wavelengths length λ of the light waves in the respective medium or an odd multiple of λ / 4 there is interference of the incoming and reflected light waves. The most important materials for the field of semiconductor technology have been dielectric materials, for example SiO ₂ , SiN _x , SiON or metallic oxides (TiO _x , Al ₂ O ₃ ), which can be used as bandpass filters or bandpass filters. Dielectrics are applied technically in a separate process only after the epitaxy.

Lin / Wu / Jou / Chang / Lee / Tsai became 13th in Electronics Letters. October 1994, Vol. 30, No. 21 p. 1793 f. a λ / 4 layer made of indium tin oxide (ITO), whose refractive index is significantly lower than that of semiconductors materials and thus has a positive influence on the reflection. ITO layers also have very good conductivity, which makes them suitable for LEDs  a contact surface on the light exit surface are applicable and additionally improve the current spread, which will be explained later shall be. However, ITO layers are due to the high material price and the manufacturing effort unsuitable for cost reasons.

In addition to transparent single layers, which are periodic Systems with multiple layers also exhibit frequency behavior known. The basic physical principles are from Born / Wolf: Principles of Optices - Electromagnetic Theory of Propagation, Interference and Dif fraction of Light, Pergamon Press, 5th ed. 1975, esp. pp. 64 to 69 been. As with Weißmantel / Hamann on p. 716 f. inferred increased However, reflection is generally caused by a multilayer arrangement in a predeterminable frequency range, so that reflective systems arise with a band filter characteristic.

This just contrary to the intended reduction in the Layer arrangements that act as reflections are called Bragg reflections referred to as gates and in particular with LEDs at the limit of absorption renden substrate used to ent otherwise ineffective in the substrate to deflect the soft energy portion, such as US 5565694, the JP 07176788 or EP 473362 and for example the publication by Baets / Deme ester / Lagasse in Journal Appl. Phys. 62 (2), 15 July 1987.

EP 0 349 193 is a dielectric multilayer arrangement with λ / 4- Layers of alternating refractive indices. Advantage of di electrical materials are the relatively high refractive index differences and the electrical insulating effect since these layer arrangements be arranged on the side of the facet of lasers. Conductive Materials would be the optically active layers of the laser, in particular bridge the pn junction. The side facet arrangement of this Layers are not suitable to be integrated epitaxially, which reduces the effort multiple.

GB 2 134 282 shows dielectric layers on a substrate low refractive index, such as glass, sapphire or plastic for anti-reflective treatment of the light coming from outside.  

Insulating layers, especially those according to the prior art known oxide layers, but are for the light exit surface on the The top of light-emitting semiconductor diodes is unsuitable, provided that this can also be contacted from above as usual. The manufacture of such Layering is also more complex.

In order to further improve the light output of such semiconductor diodes, also known the lateral current spread from the contact on the Semiconductor surface to the active zone in the semiconductor material improve. Basically, the current density is directly below the contact area always the highest. However, since the contact surface is also considered reflective Aperture for the released light acts, a good current distribution is also in the areas of the active zone not covered by the contact surface to strive for.

A possible solution for LEDs is presented in EP 0 434 233 B1 by arranging a relatively thick transparent window layer with a low specific resistance compared to the active layer between the output and active surfaces. EP 0 551 001 A1 shows the resulting effect of the quasi-conically increasing current spreading particularly clearly. EP 0 434 233 B1 specifies the required thickness of such a window layer with 2 to 30 μm. Also from the article by Sugawara / Itaya / Ishikawa / Hatakoshi in Jpn. J. Appl. Phys. Vol. 31 (1992), pp. 2446-2451 is a so-called "current spreading layer" with a thickness of 7 µm (see p. 2449) and in FIG. 4 of the article the improvement in the luminous efficiency can be clearly seen. By Huang / Yu / Kuo / Fletcher / Osentowski / Stinson / Craford in Appl. Phys. Letters 61 (9), August 31, 1992, pp. 1045 ff. Also show a thick window layer for current distribution, a thickness of 15 to 45 μm being specified in this article.

The main disadvantage of these thick window layers is that compared to active layers (thickness <1 µm) considerable thickness of the layer, resulting in a high cost of materials and a lot with conventional machines long epitaxial time. Through correspondingly complex and expensive Machines can push the epitaxial time, but not the cost.

The object of the invention is to provide a semiconductor diode with improved light to present performance that is inexpensive and technically simple can be produced.  

This object is achieved by the characterizing features of claim 1 solved.

In contrast to dielectric materials, λ / 4 layers are made of half conduct the material for surface-contacting light-emitting diodes, because they are electrically conductive. They become parallel to the active zone or the Light exit interface arranged, that is between the contact on the Surface and the underlying semiconductor layers. Let also these semiconductor layers are deposited epitaxially, causing the change to other machines for dielectric materials. So far Semiconductor materials especially never considered because of you Refractive index is relatively high, so the refractive index difference of a pair of layers is relatively small. However, this can be done according to the invention be remedied by correspondingly many pairs of layers on top of each other be used.

By separating at least one, preferably several, pairs a first and a second layer, both of which are optical Thickness of a quarter of the wavelength (or an odd number times) of the light waves emitted in the active zone and their refractive indices in the order given Refractive indices of the adjacent substances can be found through destruc tive interference a reduction in the overall effective reflection and an increase in the effective light output can be achieved.

The light waves reflected at the interface with the first substance become due to the resulting within the layer arrangement, exactly against phase reflected waves extinguished by destructive interference. This already shows that the order of the layers is mandatory is, because in the other case those reflected within the layer arrangement Waves are in phase with those reflected at the interface and so there is constructive rather than destructive interference. Will the Relationships of the refractive indices are not observed, so there is a poorer reflection behavior corresponding to the Bragg reflectors. With several pairs the reflectivity improves up to a point which the reflection of the layer arrangement itself compared to the Reflections at the interface becomes too large.

In addition to an even number corresponding to the paired layers The number of layers can also be one among the layer pairs single additional λ / 4 layer with lower refractive index inserted  be, whereby the reflectivity of the layer arrangement accordingly compared to the pure layer arrangement, which leads to a Reduction in total reflection results as long as the amplitude of the Layer arrangement of reflected light is smaller than the proportion of light emitted by the light exit interface is reflected.

Will the number of pairs in the stratification or the refraction index difference between the first and second λ / 4 layer exactly the same chosen that the reflection, that is, the amplitude of the total reflected light, the layer arrangement with that of the interface matches as closely as possible, the reflection on the Theoretically, interface completely. A single additional λ / 4 layer with a lower refractive index may enable an even better one Approaching the optimum.

It is sensible to limit the number of layer pairs also due to the slowly increasing number of layers electrical resistance, although this in the semiconductor layers Orders of magnitude less than with the insulating oxide layers according to the state of the art.

By using the same basic atomic components in the λ / 4- Layers of the layer arrangement as in the other layers can be these layer arrangements are very good in terms of production technology Epitaxial process of the semiconductor layers, for example in LED production, integrate, since no additional chemicals have to be added. MOVPE (metal organic vapor phase epitaxy) processes enable the required accuracy of the layer thickness. The waiver of oxides and the Restricting to semiconductors also avoids oxidation associated disadvantages.

A particularly preferred development of the invention is claim 6 inferred that at the same time to reduce reflection in over The lateral current spread is surprisingly simple improved.

From the theory of solid-state physics, for example from Ibach / Lüth: Solid physics - introduction and basics, 4th edition 1995 Springer Verlag, p. 368 ff., esp. p. 372 f. and p. 374, is the emergence of an enrichment zone for Majority carriers in the hetero-interface between two halves conductor layers of different materials or material mixtures  relationship. Ultimately, a requirement is given by the below different materials result in the different band gap, so that it while observing the continuity condition of the Fermi level on the Side of the semiconductor layer with a smaller band gap to a band dis continuity and an enrichment space charge zone of the majority la manure carrier is coming. For the application to spread electricity is included the greatest possible discontinuity in the majority carrier band of advantage, since the resulting enrichment space charge zone ent speaking large amount of majority load carriers as quasi free Contains electron gas. As an advantageous effect for the spread of electricity it turns out that the enrichment space charge zone over the entire hetero-interface between the two semiconductor layers forms and with a correspondingly large disc discontinuity it becomes a very good two-dimensional mobility of the majority carriers comes what Ibach / Lüth also as two-dimensional electron gas (cf. Ibach / Lüth, p. 374: The approach was two different ones, n = endowed Semiconductor materials) is called.

If the band discontinuity in the majority carrier band (for p-doped Semiconductor layers the valence band, for n-doped the conduction band) very much low or almost zero, because of the low or total lack of discontinuity also insufficient enrichment of the Majority load carriers take place. The resulting enrichment the minority charge carrier is much lower, although one Effect in principle also occurs there.

The effects of the two-dimensionally freely moving electron gas are however, as also from the textbook of experimental physics by Bergmann / Schaefer, Vol. 6 - Solid Edited by Raith, Verlag Walter de Gruyter 1992 on p. 564 is clear, so far only to be achieved in the active layer of LEDs so-called potential pots based on quantum effects, especially for multiple quantum well structures or as described by Ibach / Lüth on p. 373 f. described as modulation-doped heterojunctions, however again in the active layer. Here is not the high moving the two-dimensional electron gas. The usage of quantum films serves to modify the density of states and offers the possibility of making the material pseudomorphic (braced) what can be used particularly advantageously in laser diodes, such as from  Geng, Christian: Spontaneous mixed crystal order in AlGaInP - laser structures, Shaker Verlag Aachen, 1997, chap. 6, p. 95 ff.

To improve the spread of electricity, however, these are more extensive Effects without meaning and appropriate measures, such as the targeted Choice of the doping amounts or the suitable bandgaps of the two Semiconductor layers are not absolutely necessary, although for the active totality positive. Funding can in principle be both isotypic and be different (p-n, p-i-n). The effect of a two-dimensional electron gases is operated by Delagebeaudeuf / Linh: IEEE Transactions on Electron Devices, Vol. ED-29, No. 6, June 1982, pp. 955 ff. Also for pn heterojunctions so-called TEG (two-dimensional electron gas) fat detected and their low noise level is highlighted. As from this for so-called HEMT (high electron mobility transistors) has been demonstrated, mobility the charge carrier even reinforced by an i-n heterojunction be, the intrinsic material the smaller bandgap must have. Would the intrinsic material with higher bandgap chosen as the n-doped, there is no enrichment zone of the Majority load carriers, as with the well-known belt model can be traced. Here at HEMT, too, was ultimately the only one the aspect of the improved frequency response of these transistors examined and the lateral current propagation is irrelevant. Hetero-boundary layer sequences with isotropic doping and high discontinuity in the majority charge carrier band show a very good lateral Current spread on.

By arranging several such hetero-interfaces behind one another otherwise the current spread is improved. The is also advantageous here special effect of such a so-called superlattice, such as from Ibach / Lüth on p. 374 for the modulation-doped heterostructures named, whereby the number of enrichment space charge zones of the Majority charge carriers by a factor of 2n-1 (n - number of layer pairs) increased, for example one at the top and one at the bottom of a semiconductor layer larger band gap surrounding semiconductor layer both on their Such an enrichment space charge on the top and on its underside zone of majority carriers. The spread of electricity and thus the luminous power is determined by a sequence of such a heterojunction layer follow effectively improved. A sequence of such heterogeneous boundary layers follow already arises from the appropriate material design for  the reflection reduction layers used by all of these Layers also ge according to the required tape discontinuity chooses and thus a reduction in reflection and an improved Current spread can be achieved simultaneously with a layer sequence.

The invention is described below using exemplary embodiments and Figures explained in more detail.

Brief description of the figures

Fig. 1 embodiment, a light emitting diode with a layer arrangement for reducing the reflection,

FIG. 2a refractive index profile in the region of the layer arrangement according to the prior art with oxide materials,

Fig. 2b refractive index curve at stack of semiconductor materials,

Fig. 3 the course of the reflection of the layer arrangement shown in FIG. 2 in a resolution from 0 to 40 layer pairs,

Fig. 4 reflection as a function of wavelength at a difference considerable number of layer pairs in the air interface,

Fig. 5 and current spreading band model when using materials with a band discontinuity,

Fig. 6 shows details of current spreading and band discontinuity of FIG. 5,

Fig. 7 detailed views of the various possible layer arrangements with and without additional individual λ / 4 layer.

Fig. 1 shows a section through a semiconductor diode with a layer arrangement 1 , consisting of a plurality of pairs of a first λ / 4 layer 1 .hi with a high refractive index and on this a second λ / 4 layer 1 .lo with a lower Refractive index. The pairs are arranged in such a way that the layers always change and the first λ / 4 layer 1 .hi with likewise high refractive index is arranged on the lower-lying semiconductor layer 2 with a high refractive index. The last λ / is located on the light exit boundary surface 9 4-1 .lo layer with low refractive index. These λ / 4 layer thicknesses or odd multiples of λ / 4 can be deposited reliably, for example, by means of organometallic gas phase epitaxy (MOVPE). In addition to the λ / 4 layer, the thickness is of course also an odd multiple of it, i.e. every 3λ / 4-, 5λ / 4-. . . Layer with the same effect.

Under the layer arrangement 1 there is possibly a window layer 2 for the transition to a new lattice constant, the upper cladding layer 3 of the LED, the active zone 4 , the lower cladding layer 5 and a Bragg reflector 6 consisting of a sequence of λ / 4 layers with different refractive index. Below this is the semiconductor substrate 7 , the underside of which is metallically coated as contact 8 . The light exit interface 9 lies between the λ / 4 layers and the outer material 11 with a low refractive index, which can either be the air directly or, for example, a translucent epoxy or silicone compound as a shell.

In Fig. 1 it is an exemplary embodiment of an AlGaInP LED arrangement, which were deposited on a GaAs substrate ( 7 ) in a lattice-matched manner. Adjacent to the substrate is the reflection layer 6 , the so-called Bragg reflector made of alternating (Al _x Ga _1-x ) As layers with n-doping of different compositions. The individual layers of the Bragg reflector are each λ / 4 thick, where λ is the wavelength of the emitted light in the respective medium, so that there is a reflection of the light component emitted in the direction of the substrate. This effect is described by Murtaza and others in IEEE Journal of Quantum Electronics, Vol. 31, no. 10, Oct. 1995, p. 1819 ff.

The lower cladding layer 5 of the LED consists of lattice-matched (Al _y Ga _1-y ) InP, which is also n-doped. The composition y is chosen so that the band gap or the energy gap of the cladding layer 5 is higher than that of the active zone 4 or of the emitted light, in order to be quasi transparent to it. The active zone 4 itself is undoped in this exemplary embodiment and can consist of a single layer of (Al _z Ga _1-x ) InP or of (Al _a Ga _1-a ) InP quantum films with (Al _b Ga _1-b ) InP- Barriers exist, where 0 ≦ a ≦ b ≦ 1 applies. On top is the upper cladding layer 3 made of lattice-matched (Al _y Ga _1-y ) InP with a higher band gap than the active zone 4, comparable to the lower cladding layer 5 , but p-doped.

As a special configuration of the layer arrangement 1 , p-doped GaP is followed by AlP. Since this material system has a smaller lattice constant than GaAs or (Al _x Ga _1-x ) InP, a transition layer 2 made of GaP is first grown thin in which the new lattice constant is to be set.

Then the layer arrangement 1 is applied in alternating pairs of layers of GaP and AlP, each p-doped.

FIG. 2 enables a comparison of the different refractive index profiles over a layer arrangement according to the prior art ( FIG. 2a) with a layer arrangement according to the invention ( FIG. 2b).

The refractive indices for the deeper semiconductor layer 3 are about 3.5 in both cases for the

• - λ / 4 dielectric layers 1 .Hi (≈ 2.5) and 1 .Lo (≈ 1.5) shown in FIG. 2a
• - In Fig. 2b shown semiconducting λ / 4 layers 1 .Hi (≈ 3.35) and 1 .Lo (≈ 3.275)

and for the outer material (air, epoxy) each indicated with around 1. The course in

Fig.

2a corresponds to the anti-reflective layer arrangement according to FIG EP 0 349 193, which has two pairs of λ / 4 dielectric layers. The refractive indices of the two λ / 4 layers are clearly below different. In contrast, the semiconducting λ / 4 layers, as in

Fig.

2b, both relatively high and in particular less strong changing refractive indices. The sequence of the λ / 4 layers opposite the semiconductor substrate is, however, the reason for this exemplary embodiment laying right away.

GaP and AlP as an exemplary embodiment have a refractive index difference (≈ 0.075), even if this is much smaller than that of dielectric materials (≈ 1.0). Therefore, more pairs of λ / 4 layers are used, the number of which ultimately always depends on the technically realizable refractive indices. With GaP on Al _x Ga _1-x P, for example, even more pairs would be required.

Fig. 3 illustrates the course of the Reflexivion the layer arrangement depending on the number of layers. The number is varied from 0 to 40 pairs of layers.

When the semiconductor material (n ≈ 3.5) meets the outer material (n ≈ 1) directly, the reflection is 30%. The function f1 illustrates the increasing reflection of the layer arrangement 1 without taking into account the reflection at the light exit interface. However, since the reflections on the layer arrangement 1 are in phase opposition to the light previously reflected at the interface due to the selected sequence of the layers, the total reflection, represented as a function f3, is reduced. If the layer sequence were chosen incorrectly, the reflection behavior of a Bragg reflector would be comparable to that shown in function f2 and in which f1 would add up to the 30% constant.

However, if the layer sequence is selected correctly (see FIGS. 7a and 7b) and the number of layer pairs is so large that the reflection of the layer arrangement corresponds to that of the interface, the reflection can at least theoretically be reduced to zero and the transitivity consequently increased to 100% will. Fig. 3 also makes it clear that a further increase in the number of layers leads to an increasing deterioration in the reflection properties, since now the reflectivity of the layer arrangement becomes dominant. The exact number of pairs of layers for which the reflection becomes zero depends, of course, on the exact refractive index values of semiconductors, the λ / 4 layers and the outer material. For an outer material made of air, an optimum of 25 layer pairs was determined for AlP / GaP-λ / 4 layers, for an epoxy or silicone shell, 18 layer pairs resulted in the optimum. If, for example, instead of AlP and GaP, an Al _x Ga _1-x P mixed crystal with different compositions x were used in one case, the optimal number would change slightly. For example, Al ₁ Ga ₀ P has a poorer electrical resistance than Al _0.8 Ga _0.2 P and can be replaced by this, which means that only slightly more layer pairs would have to be used.

Fig. 4 additionally shows the wavelength-selective dependency with different numbers of layers at the interface with air. For the number a = 0 there is a constant reflectivity of 30%, with about 20 layers a significant reduction in the wavelength λ _s , but with 80 layers a significant deterioration and increase. In addition, the behavior can also be seen in FIG. 4 for the wave components that deviate from the wavelength λ _s . The thickness of the λ / 4 layers determines the wavelength curve and the position of wavelength λ _s .

If one also selects the materials of the λ / 4 layers in such a way that a band discontinuity with an enrichment zone of the majority charge carriers arises between them, in addition to the reflectivity, the current spread can also be significantly improved. This is to be visualized using FIG. 5. FIG. 5a shows a sequence of λ / 4 layer pairs 1 .hi / 1 .lo, for example AlP / GaP pairs, between which there are each in a λ / 4 layer 1 .lo on the side to the other λ / 4 layer 1 .hi forms a majority charge carrier enrichment and thus forms a current channel 1.3 . The resulting step-like current spread i from the number of layers of layers from the exit surface of the contact 10 to the lower lying semiconductor layers ( 2 , 3 ,...) Is indicated sketchily, whereby of course the current spread in the three-dimensional space of the hetero interface layer sequence is quasi conical. The different band gaps can be caused by different semiconductor materials (e.g. AlP / GaP) or different compositions, i.e. mixing ratios of a mixed crystal (e.g. Al _x Ga _1-x P / GaP).

Charge carriers thus come into an area of very good conductivity ( 1.3 ), which is followed in each case by an area of poor conductivity, so that the current does not spread in a straight line but drifts laterally, thus considerably increasing the current spread.

Fig. 5b illustrates the different conductivity between a very good conductivity S _high in the enrichment zone and a rather poor conductivity S _Low in the depletion regions varies. Although this average sequence can slightly increase compared to a simple semiconductor layer of the same thickness, this sequence is negligible given a correspondingly limited number of layer pairs or heterogeneous layer sequences. In contrast, the local increase in conductivity, which always extends over the entire hetero interface, causes a strong spread of current spread, which is only marginally influenced by whether a depletion zone or the semiconductor material with quasi-medium conductivity is connected. From Fig. 5c can be seen in the band model, consisting of the energy level of the valence band E _VB , the Fermi level E _F and the conduction band E _LB , the sequence of enrichment and depletion zones even more clearly. Both semiconductor layers 1 .hi and 1 .lo are p-doped in this exemplary embodiment (Fermi level in the vicinity of the valence band).

FIG. 6a shows again in detail (D1 in FIG. 5) the current propagation at a heterojunction layer and FIG. 6b the corresponding discontinuity of the band model and the majority charge carrier enrichment (comparable to detail D2 in FIG. 5). Thus, in FIG. 6 a the lateral current spread 4.6 within the hetero-interface is compared with the normal current spread ( 5.6 ) indicated by the dashed line without the two-dimensional current channel. It is clearly recognizable that a lateral current drift occurs on the side of the hetero interface with the enrichment of majority charge carriers in the immediate vicinity of the hetero interface. If one considers the band model according to FIG. 6b, the discontinuity of the majority charge carriers, here the enrichment of the electrons in n-doped materials, becomes clear. In the case of p-doped materials, as previously described in FIGS. 1 to 5, this would be an enrichment of holes in the valence band, as can be seen in D2 in FIG. 5c. The discontinuity 6.6 can even reach and exceed the Fermi level (E _F ), as a result of which the number of free majority charge carriers increases sharply. However, even with a smaller discontinuity, lateral current spreading at the hetero-interface can generally be observed, although not as strongly as with a two-dimensionally freely moving electron gas. The depletion zone 7.6 opposite the depletion zone 6.6 has no significant influence on the current spreading, ultimately only increases the overall resistance of the layer sequence only slightly. The layer arrangement 1 thus has both a reduced reflectivity and an improved current spread.

Reference should be made to the simple realization of this layer arrangement 1 made of GaP and AlP, since the chemical atomic basic components (Ga, Al, P) substances already have all these basic components for the production of the other semiconductor layers (active layer (Al _y Ga _1-y ) InP) on) are available and therefore no adjustments other than the corresponding control of the epitaxy need to be carried out. In principle, the heterogeneous layers can also consist of different compositions of a mixed crystal, provided that the required band discontinuity occurs on the heterogeneous surface. The basic components do not necessarily all have to occur together in a single layer, but only for the epitaxial process as a whole, which is possible due to the occurrence in several different layers.

FIG. 7, consisting of FIGS. 7a without and 7b with the individual additional λ / 4 layer 1 .z, shows once again the two possible layer arrangements, in FIG. 7a an even number of layers x corresponding to twice the number of pairs a is used, during which the number of layers in FIG. 7b is odd and increased (or decreased) by one.

Claims (8)

1. Light-emitting semiconductor diode (LED) with a light of the wavelength λ-emitting optically active zone and a light exit interface between the semiconductor material with a high refractive index and an outer material with a lower refractive index, with a layer arrangement between the light exit interface and the optically active zone to reduce the occurring reflection of the light waves is provided,
in which the layer arrangement consists of at least one pair of a first λ / 4 layer with a high refractive index and then a second λ / 4 layer with a lower refractive index, both of which each have an optical thickness of a quarter of the wavelength of the light waves or a have an odd multiple thereof, where
the pairs are arranged one above the other in such a way that the layers change in each case and the uppermost λ / 4 layer, which is in contact with the outer material via the light exit surface, is a λ / 4 layer with a low refractive index, characterized in that the λ / 4 layers arranged parallel to the active zone and are made of electrically conductive semiconductor material. 2. Light-emitting semiconductor diode according to claim 1, characterized shows that several pairs of a first and a second λ / 4- Layer are each arranged one on top of the other Semiconductor material with a high refractive index using a first λ / 4 layer with a high refractive index.   3. Light-emitting semiconductor diode according to claim 1, characterized shows that several pairs of a first and a second λ / 4- Layer can be arranged on top of each other and additionally on the Semiconductor material with high refractive index a single, further λ / 4- Layer with a low refractive index is deposited. 4. Light emitting semiconductor diode according to one of the preceding Claims, characterized in that the number of pairs in the Layer arrangement and / or the refractive index difference between the first and second λ / 4 layers are chosen so that the Amplitude of the total light reflected by the layer arrangement with the amplitude of the reflected light of the light exit interface matches as closely as possible. 5. Light-emitting semiconductor diode according to one of the preceding Claims, characterized in that the two λ / 4 layers of the layer arrangement of epitaxial semiconductors are layers whose chemical atomic basic components are preferred do not have the basic chemical atomic components of the Go out semiconductor diode. 6. Light-emitting semiconductor diode according to one of the preceding Claims, characterized in that the materials or Material mixtures of the two λ / 4 layers can be chosen so that between them a band discontinuity with an enrichment zone for trains the majority load carriers.   7. Light-emitting semiconductor diode according to one of the preceding claims, characterized in that
the active zone of the semiconductor diode consists of a composition of aluminum gallium indium phosphide (Al _x Ga _1-x ) InP, where x indicates the mixing ratio between aluminum and gallium and can be between zero and one, and that
between 5 and 30 pairs each of a first λ / 4 layer made of gallium phosphide (GaP) and a second λ / 4 layer made of aluminum phosphide (AlP) or aluminum gallium phosphide (Al _x Ga _1-x P) to be ordered. 8. Light-emitting semiconductor diode according to claim 7, characterized notes that between 23 and 28 pairs of GaP / AlP are used, if the outer fabric is air and 15 and 20 pairs if the outer fabric Fabric is translucent epoxy or silicone mass.