Method, a semiconductor detector, and a detector arrangement, for the detection of sunlight

Abstract

The present invention concerns a method for the detection of sunlight with a detector arrangement that delivers an output signal as a function of incident sunlight. In the method a detector arrangement is deployed with an SiC-semiconductor detector, which is only sensitive to the UV-component of the incident sunlight. By the deployment of such a detector arrangement a disturbance of the sunlight detection by artificial light sources is to a large extent avoided, so that a more reliable detection of the sunlight is enabled.

Claims

1. A method for the detection of sunlight, in which a detector arrangement is deployed, which is only sensitive to a UV-component of incident sunlight, comprising: deploying at least one SiC-semiconductor detector in the detector arrangement, in which a lower of two semiconductor regions form a pn-junction which has a dopant concentration of <1*10.sup.15 cm.sup.3, and which has a thickness that is greater than 50% of the width of a space-charge zone in thermodynamic equilibrium, with the thickness not restricting the space-charge zone of this semiconductor region.

2. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector in which the thickness of the lower semiconductor region is at least 1.7 m.

3. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector in which the dopant concentration of the lower semiconductor region is <5*10.sup.14 cm.sup.3.

4. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector in which an upper of the two semiconductor regions forming the pn-junction has a thickness of between 1.5 m and 3 m.

5. The method according to claim 4, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector in which the upper semiconductor region has a dopant concentration of >5*10.sup.18 cm.sup.3.

6. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector, which carries an anti-reflection layer for a wavelength range of between 300 and 380 nm.

7. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector, which carries an anti-reflection layer of SiO.sub.2 with a thickness of between 50 and 66 nm.

8. The method according to claim 1, deploying as the at least one SiC-semiconductor detector, a 4HSiC-semiconductor detector.

9. The method according to claim 1, further comprising: deploying as the at least one SiC-semiconductor detector, a SiC-semiconductor detector in which the lower semiconductor region is n-doped.

10. The method according to claim 1, further comprising: applying a block voltage on the pn-junction, by means of which the sensitivity of the SiC-semiconductor detector is increased in the wavelength range between 330 and 380 nm.

11. The method according to claim 1, further comprising: deploying in the detector arrangement at least one second detector, which has a maximum sensitivity in the visible spectral range, and determining from output signals of the SiC-semiconductor detector and the second detector as to whether direct solar radiation is present, or whether solar radiation through a window, or radiation from a light source emitting only in the UV spectral range, or only in the visible spectral range, is present.

12. The method according to claim 11, further comprising: deploying as the second detector a Si, GaP or GaAs semiconductor detector.

13. A SiC-semiconductor detector, in which a lower of two semiconductor regions forming a pn-junction has a dopant concentration of <1*10.sup.15 cm.sup.3, and has a thickness that is greater than 50% of the width of the space-charge zone in thermodynamic equilibrium, with thickness not restricting this semiconductor region.

14. The SiC-semiconductor detector according to claim 13, characterised in that the dopant concentration of the lower semiconductor region is <5*10.sup.14 cm.sup.3.

15. The SiC-semiconductor detector according to claim 13, characterised in that the thickness of the lower semiconductor region is at least 1.7 m.

16. The SiC-semiconductor detector according to claim 13, characterised in that an upper of the two semiconductor regions forming the pn-junction has a thickness of between 1.5 m and 3 m.

17. The SiC-semiconductor detector according to claim 13, characterised in that the SiC-semiconductor detector carries an anti-reflection layer for a wavelength range of between 300 and 380 nm.

18. An application of a SiC-semiconductor detector according to claim 13 for the control of the air conditioning system in motor vehicles.

19. An application of a SiC-semiconductor detector according to claim 13 for the registration of an open window in a room.

20. A detector arrangement for the detection of sunlight that has at least one SiC-semiconductor detector according to claim 13, and at least one second detector, which has a maximum sensitivity in the visible spectral range.

21. The detector arrangement according to claim 20, in which a plurality of the SiC-semiconductor detectors and second detectors is arranged in the form of an array.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) In the following the proposed method is again explained in detail with by means of examples of applications and embodiments. Here:

(2) FIG. 1 shows in a highly schematic representation an example of the construction of a detector arrangement for the detection of sunlight according to the proposed method;

(3) FIG. 2 shows an example of the output signal (current strength) of the detector of the proposed detector arrangement, with and without irradiation by various light sources;

(4) FIG. 3 shows in a highly schematic representation an example of a detector arrangement with two detectors, which are sensitive to different spectral ranges; and

(5) FIG. 4 shows an example of the construction of the SiC-semiconductor detector in a schematic representation.

EXAMPLES FOR CARRYING OUT THE INVENTION

(6) FIG. 1 represents a detector arrangement in a highly schematic manner, as it can be deployed in the proposed method for the detection of sunlight. The detector arrangement features in this example, an SiC-semiconductor detector 1, which by virtue of the properties of the semiconductor material is only sensitive in the wavelength range <400 nm, and thus for the UV-component of the sunlight. With incident sunlight 2 this detector 1 delivers a signal, which is suitably treated in an evaluation and amplifier circuit 3, and is prepared as an output signal 4 of the detector arrangement. The level of this output signal is a measure for the intensity of the incident solar radiation.

(7) With a semiconductor detector based on SiC, in particular a 4HSiC detector, which has a very simple design, even in the event of scattered incident sunlight, or additional direct or indirect irradiation by artificial light sources, the presence of solar radiation can be reliably detected. Moreover, the detector is also not disturbed by sunlight that is incident through a window, since the glazing that is usual in building construction absorbs UV light. By evaluation of the signal measured by the detector it is possible to deduce whether direct solar irradiation, or indirect solar irradiation from scattered light, is present. Moreover it is possible to measure precisely the irradiation intensity at room temperature. In combination with a detector that is sensitive to the visible spectral range, for example a silicon detector, irradiation by artificial light or by filtered sunlight, in which the UV-component has been filtered out, can also be determined in parallel. This will be explained once again in more detail further below in conjunction with FIG. 3.

(8) FIG. 2 shows an example of measurements with a 4HSiC-semiconductor detector in the event of incidence of various types of light. From the measurements it can be seen that artificial light sources, such as light from a halogen lamp or an incandescent lamp, do not deliver a measurement signal lying above the measurement noise. Without illumination the detector signal is dominated by the measurement noise (dark leakage current of the detector). Neither with irradiation by a halogen lamp, nor an incandescent bulb is there a significant alteration in the detector signal. If the detector is subjected to direct or indirect solar irradiation, the detector signal clearly rises. However, if the irradiation takes place through a window, the detector signal once again decreases to the value before exposure to direct or indirect solar radiation. In this example the irradiation with sunlight has been determined by indirect irradiation of the detector with sunlight in the form of scattered light that is incident through an open window on the north side of a building on a cloudy day.

(9) FIG. 3 shows in a highly schematic manner an example of a detector arrangement in which in addition to the SiC semiconductor detector 1 a detector 6 is deployed that is sensitive to the visible spectral range. The signals of both detectors are prepared in an evaluation circuit 3, in the event of detection of direct or indirect incident sunlight, in which case both detectors deliver a measurement signal, to provide an output signal 4 that represents a measure for the intensity of the sunlight. In the event of detection by just one of the two detectors on the other hand an appropriate output signal 5 is generated. By this means the insensitivity of the method to disturbances generated by other light sources can be increased further. For the construction of such a detector arrangement, the methods usual for the construction and connection of semiconductor components made of silicon are also available for silicon carbide components.

(10) Finally, FIG. 4 shows in a schematic representation an example of the construction of the SiC semiconductor detector that is deployed. The electrical contacts on the upper and lower faces of the detector are not represented in this figure. In this example the detector has a preferably (highly) n-doped SiC semiconductor substrate 7, on which a first doped semiconductor region 8 (designated as the lower semiconductor region) is applied or embedded, likewise preferably n-doped, with a dopant concentration of less than 5*10.sup.14 cm.sup.3. The thickness of the lower semiconductor region 8 is at least 1.7 m. On this lower semiconductor region 8 is applied a second highly doped semiconductor region 9 (designated as the upper semiconductor region), preferably p+-doped with a dopant concentration of more than 5*10.sup.18 cm.sup.3 and a layer thickness of between 1.5 m and 3 m. This upper semiconductor region 9 is preferably deposited on the lower semiconductor region 8 using an epitaxy process. These two semiconductor regions 8, 9 form the pn-junction of the semiconductor detector. In this example an anti-reflection coating 10 of SiO.sub.2 is applied on the upper semiconductor region 9; this has a thickness in the range between 50 nm and 66 nm. For this anti-reflection coating a material is preferably chosen, which for the wavelength range below 300 nm is no longer (completely) transparent.

(11) The proposed method, the related SiC semiconductor detector and the related detector arrangement can be deployed in the applications for motor vehicles already mentioned in the introduction to the description. By this means, for example, for the control of an air conditioning system disturbances generated by other light sources, such as street lighting or lighting in tunnels, are avoided; these, for example, would deliver false information concerning the position of the sun. Measurement of the irradiation of light-sensitive objects with sunlight over a longer period of time is also possible with this method. Here too, the measurement is not falsified by other artificial light sources.

(12) A further example of an application is represented by the contactless registration of an open window in daylight. In contrast to mechanical contact circuits or magnetic (contactless) monitoring components, the solution with the proposed detector arrangement allows almost any positioning in the building interior, on or away from the window that is to be monitored. Particularly when using an SiC-based sunlight detector, by virtue of its small leakage current the scattered light of the solar spectrum passing through the gap of a tilted window can also be reliably detected so as to decide whether a window is open. Any disturbance generated by other light sources in the building is thereby excluded.

(13) Spatially resolved sunlight detection can also be implemented using an appropriately configured detector arrangement, in which the individual detectors are assembled to form a pixel sensor (identical to that of a CCD camera), in order to determine the position of the solar radiation. Combination with a detector array that is sensitive to the visible spectral range, for example a silicon CCD camera, is also possible here.

(14) Needless to say, many other applications are also possible in which sunlight radiation is to be detected, for example, in order to reduce the probability of a false alarm or a false interpretation of other measurements as a result of solar radiation. One example is spatially resolved flame detection, as deployed in registration of the power units of anti-aircraft missiles. Here by comparing the UV light component and the visible light component a differentiation can be made between sunlight and power unit emissions. Measurement of the length of the day is also relevant for a series of commercial applications. Thus the duration of the length of the day influences the time of flowering in plant cultivation.

REFERENCE LIST

(15) 1 SiC-semiconductor detector 2 Sunlight 3 Evaluation circuit 4 Output signal 5 Further output signal 6 Detector for the visible spectral range 7 SiC-semiconductor substrate 8 Lower semiconductor region 9 Upper semiconductor region 10 Anti-reflection layer