Optoelectronic semiconductor component

Abstract

An optoelectronic semiconductor component is disclosed. In an embodiment an optoelectronic semiconductor component includes a front side, a first diode and a second diode arranged downstream of one another in a direction away from the front side and electrically connected in series such that the first diode is located closer to the front side than the second diode and an electrical tunnel contact between the first and the second diodes, wherein the second diode comprises a diode layer of Si.sub.nGe.sub.1-n, where 0≤n≤1, wherein the first diode comprises a first partial layer of SiGeC, a second partial layer of SiGe and a third partial layer of SiGeC, and wherein the partial layers follow one another directly in the direction away from the front side according to their numbering such that the first and third partial layers are of (Si.sub.yGe.sub.1-y).sub.1-xC.sub.x, whereas 0.05≤x≤0.5 or 0.25≤x≤0.75, and whereas 0≤y≤1, and the second partial layer is of SizGe1-z, whereas 0≤z≤1.

Claims

1. An optoelectronic semiconductor component comprising: a front side; a first diode and a second diode arranged downstream of one another in a direction away from the front side and electrically connected in series such that the first diode is located closer to the front side than the second diode; and an electrical tunnel contact between the first and the second diodes, wherein the second diode comprises a diode layer of Si.sub.nGe.sub.1-n, where 0<n≤0.8, wherein the first diode comprises a first partial layer of SiGeC, a second partial layer of SiGe and a third partial layer of SiGeC, and wherein the partial layers follow one another directly in the direction away from the front side according to their numbering such that the first and third partial layers are of (Si.sub.yGe.sub.1-y, .sub.i-xC.sub.x, whereas 0.05≤x≤0.5 or 0.25≤x≤0.75, and whereas 0.25≤y≤0.9, and the second partial layer is of Si.sub.zGe.sub.1-z, whereas 0.1≤z≤0.95 so that the optoelectronic semiconductor component comprises the following layers following directly one above another: a first contact layer made of n-doped silicon at the front side, the first partial layer, the second partial layer, the third partial layer, a first tunnel contact layer of the electrical tunnel contact made of degeneratively p-doped silicon, a second tunnel contact layer of the electrical tunnel contact made of degeneratively n-doped silicon, a carrier layer which is an n-doped or a p-doped silicon substrate, the diode layer of the second diode, and a second contact layer which is a silicon layer.

2. The optoelectronic semiconductor component according to claim 1, wherein the first diode is configured to: absorb first radiation in a first wavelength range between 300 nm and 500 nm; and generate first charge carriers by the first radiation.

3. The optoelectronic semiconductor component according to claim 2, wherein the second diode is configured to: absorb second radiation in a second wavelength range between 500 nm and 1500 nm; and generate second charge carriers by the second radiation.

4. The optoelectronic semiconductor component according to claim 1, wherein each of the first and the third partial layers has a thickness of between 1 nm and 10nm inclusive, and wherein the second partial layer has a thickness between 5 nm and 25 nm inclusive.

5. The optoelectronic semiconductor component according to claim 4, wherein the diode layer has a thickness of between 5 nm and 200 nm inclusive.

6. The optoelectronic semiconductor component according to claim 1, wherein the partial layers consists essentially of a material with a high band spacing so that a band gap of the material is between 2.4 eV and 3.2 eV inclusive.

7. The optoelectronic semiconductor component according to claim 6, wherein the diode layer has a band gap in a range from 0.66 eV to 0.95 eV inclusive.

8. The optoelectronic semiconductor component according to claim 1, wherein the second contact layer is the silicon layer doped with B, Al and/or Ga with a dopant concentration of at least 1×10.sup.191/cm.sup.3.

9. The optoelectronic semiconductor component according to claim 8, wherein the second contact layer has a thickness between 30 nm and 300 nm inclusive, and wherein the diode layer directly adjoins the carrier layer with a thickness of between 30 μm and 600 μm inclusive in a direction towards the front side.

10. The optoelectronic semiconductor component according to claim 1, wherein the second contact layer has a thickness between 30 nm and 300 nm inclusive, and wherein the diode layer directly adjoins the carrier layer with a thickness of between 30 μm and 600 μm inclusive in a direction towards the front side.

11. The optoelectronic semiconductor component according to claim 1, wherein semiconductor layers of the first and second diodes are polycrystalline.

12. The optoelectronic semiconductor component according to claim 1, wherein semiconductor layers of the first and second diodes are amorphous.

13. The optoelectronic semiconductor component according to claim 1, wherein the optoelectronic semiconductor component is a tandem solar cell.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, an optoelectronic semiconductor component described here is explained in more detail with reference to the drawing on the basis of an exemplary embodiment. Identical reference signs indicate identical elements in the individual figures. However, no relationship to scale is shown here, but rather individual elements can be illustrated in an exaggerated manner for better understanding.

(2) FIGS. 1 and 2 show schematic sectional views of exemplary embodiments of optoelectronic semiconductor components;

(3) FIG. 3 shows a schematic illustration of a band structure of an optoelectronic semiconductor device described herein; and

(4) FIG. 4 shows a schematic illustration of spectral properties of an optoelectronic semiconductor device described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(5) An exemplary embodiment of a semiconductor component 1 is shown in FIG. 1. The semiconductor component 1 is configured as a tandem solar cell and comprises a first diode 2 and a second diode 4, which are electrically connected to one another via a tunnel contact 3 and which are connected in series. In this case, the first diode 2 is located closer to a front side 10 of the semiconductor component 1, wherein the front side 10 is preferably a radiation inlet side of the semiconductor component 1.

(6) A first contact layer 25 serves as emitter at the radiation inlet side 10. The first contact layer 25 is made of silicon, which is highly n-doped, for example, with As. The degree of doping of the layers is illustrated by the symbols −, +, ++. A thickness of the first contact layer 25 is preferably at least 10 nm and/or at most 150 nm, for example, at 80 nm. The first contact layer 25 can be a double layer with an initial doping of 1×10.sup.18 1/cm−3 and a highly doped layer with a dopant concentration of 2×10.sup.20 1/cm3. The doping preferably increases towards a light inlet layer 5, that is, the transition between the first and second upper contact layers can also be made graduated, that is, the transition does not have to take place abruptly.

(7) The first contact layer 25 is partially included in the first diode 2. A main component of the first diode 2 is formed by three partial layers 21, 22, 23. The first and the third partial layers 21, 23 are SiGeC layers, between which a preferably thin SiGe layer is located as the second partial layer 22. The partial layers 21, 22, 23 are essentially configured to absorb short-wave light in the range from 300 nm to approximately 500 nm, and are used to generate current by means of radiation from this wavelength range.

(8) A low p-doped layer 24 follows the partial layers 21, 22, 23 in the direction away from the radiation inlet side 10. The low-doped layer 24 is preferably a silicon layer doped with B. A thickness of the low-doped layer 24 is, for example, at least 30 nm or 50 nm and at most 200 nm or 100 nm.

(9) The subsequent tunnel contact 3 is composed of a first tunnel contact layer 31 and a second tunnel contact layer 32. The first tunnel contact layer 31 located closer to the radiation inlet side 10 is preferably doped with a silicon layer which is p-doped as far as the degenerate, that is, for example, with more than 8×10.sup.18 1/cm3 of boron. The second tunnel contact layer 32 is preferably a silicon layer which is n-doped as far as the degenerate, wherein P or As is used as dopant, for example, and the doping should be above 2×10.sup.19 1/cm3. Thicknesses of the tunnel contact layers 31, 32 are preferably at least 20 nm or 40 nm and/or at most 150 nm or 80 nm, in particular in each case at approximately 50 nm.

(10) The tunnel contact 3 is located directly on a carrier layer 43. The carrier layer 43 is formed by an n-doped or alternatively by a p-doped silicon substrate. A conductivity of the carrier layer 43 is preferably at least 1 Ωcm and/or at most 6 Ωcm. A thickness of the carrier layer 43 is preferably approximately 180 μm.

(11) A diode layer 41, preferably made of SiGe, is located directly on the carrier layer 43, which forms part of the second diode 4. The diode layer 41 is undoped or lightly p-doped. For example, the diode layer 41 has a thickness of 50 nm.

(12) The diode layer 41 is followed by a second contact layer 42 in the direction away from the radiation inlet side 10, the second contact layer 42 is a highly doped p-layer. The dopant used is, for example, B or Ga or Al. A thickness of the second contact layer 42 is, for example, 100 nm.

(13) In the exemplary embodiment of FIG. 2, the radiation inlet side 10 is formed by a light inlet layer 5, in particular of a nitride such as silicon nitride, or of a transparent conductive oxide, TCO for short. A thickness of the light inlet layer is, for example, at least 50 nm and/or 90 nm, in particular approximately 65 nm.

(14) A contact layer 62, for example, by means of silver screen printing, is applied to the radiation inlet side 10 for electrical contacting. For this purpose, the optional light inlet layer 5 is preferably removed in places, in particular in a self-adjusting manner, by a known method.

(15) On a rear side 40 opposite the radiation inlet side 10, that is, on the second contact layer 42, a further electrode 61 is preferably applied in a planar or structured manner, for example, by means of aluminum screen printing. A firing process can then be carried out. The semiconductor component 1 designed as a solar cell can thus be produced using standard methods.

(16) Otherwise, the embodiment of FIG. 2 corresponds to that of FIG. 1.

(17) The electronic band structure resulting from this construction illustrated in conjunction with FIGS. 1 and 2 is schematically illustrated in FIG. 3. The respective band gap in eV is indicated for partial sections. The dash lines symbolize the boundaries between the layers of the semiconductor component 1. The zero line with respect to the band gap is illustrated as a dash-dot line. In contrast to FIG. 1 or 2, according to FIG. 3, other dopings can also be present, for example, in the layers 24, 43.

(18) In FIG. 4, the light irradiation power P for sunlight in W/m.sup.2/nm is shown in relation to the wavelength λ in nm. The absorption ranges for the first diode 2 and the second diode 4 are shown schematically.

(19) Unless otherwise indicated, the components shown in the figures preferably follow one another in each case directly in the specified sequence. Likewise, unless otherwise indicated, the relative positions of the illustrated components with respect to one another are correctly reproduced in the figures.

(20) The invention is not restricted to the exemplary embodiments by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.