DEVICE AND METHOD FOR DETERMINING A WAVELENGTH OF A RADIATION

Abstract

The invention relates to a device and a method for determining a wavelength of radiation.

Claims

1. A device (10) for determining a wavelength of radiation comprising at least two absorption elements (12, 14) for generating photosignals, wherein the absorption elements (12, 14) are arranged in a layer structure (16) one above the other, characterized in that an upper absorption element (12) has a vertically varying chemical composition, which is characterized by a material gradient in order to set a wavelength-dependent absorption coefficient, and a lower absorption element (14) is designed to be chemically homogeneous.

2. The device (10) according to claim 1, characterized in that the absorption elements (12, 14) comprise at least one semiconductor material.

3. The device (10) according to claim 1 or 2, characterized in that the absorption elements (12, 14) comprise binary, ternary, or quaternary alloys of semiconductors, preferably direct semiconductors.

4. The device (10) according to any one or more of the preceding claims, characterized in that the material gradient is varied monotonically rising or falling vertically, wherein the material gradient preferably has a linear or quadratic dependence on the vertical position within the upper absorption element (12).

5. The device (10) according to any one or more of the preceding claims, characterized in that the material gradient in the upper absorption element (12) is formed by a vertical variation of the proportions of the alloy partners of a semiconductor alloy.

6. The device (10) according to any one or more of the preceding claims, characterized in that the upper absorption element (12) comprises a semiconductor alloy of the general form A.sub.xB.sub.1-X, wherein A and B each characterize alloy partners and x is the proportion of A in the semiconductor alloy which is vertically varied.

7. The device (10) according to any one or more of the preceding claims, characterized in that the upper absorbent element has a monotonically rising or monotonically falling absorption coefficient over a spectral range of at least 100 meV, preferably at least 200 meV, more preferably at least 300 meV.

8. The device (10) according to any one or more of the preceding claims, characterized in that a material for the absorption elements (12, 14) is selected from a group comprising (Mg, Zn)O, (In, Ga).sub.2O.sub.3, (Si, Ge), (Si, Ge)C, (Al, Ga).sub.2O.sub.3, (In, Ga)As, (Al, Ga)As, (In, Ga)N, (Al, Ga)N, (Cd, Zn)O, Zn(O, S), (Al, Ga, In)As, (In, Ga)(As, P), (Al, Ga, In)N, (Mg, Zn, Cd)O, or (Al, Ga, In).sub.2O.sub.3.

9. The device (10) according to any one or more of the preceding claims, characterized in that the absorption elements (12, 14) are configured to absorb radiation in a defined wavelength range.

10. The device (10) according to any one or more of the preceding claims, characterized in that the layer structure (16) comprises a substrate (20), wherein the upper absorbent element (12) and the lower absorbent element (14) are arranged on different sides of the substrate (20).

11. The device (10) according to the preceding claim, characterized in that the substrate (20) is at least partially transparent to the radiation.

12. The device (10) according to any one or more of the preceding claims, characterized in that the layer structure (16) comprises contacts (18) between the absorption elements (12, 14), wherein photosignals in the form of photocurrents are measurable between the contacts (18).

13. The device according to any one or more of the preceding claims, characterized in that the device comprises a data processing device which is configured to calculate the ratio of the signals of the photocurrents and to determine the wavelength of the radiation in consideration of the ratio.

14. A method for determining a wavelength of radiation comprising the following steps a) providing a device for detecting a wavelength of radiation according to any one of the preceding claims, b) providing radiation, the wavelength of which is to be determined, wherein the radiation is directed onto the device, c) absorbing a first component of the radiation by way of an upper absorption element (12) and converting it into a photocurrent signal I1, d) absorbing a second component of the radiation by way of a lower absorption element (14) and converting it into a photocurrent signal I2, e) determining the wavelength of the radiation taking into consideration the signal ratio I1/I2.

15. The method according to the preceding claim, characterized in that the signal ratio is dependent on the wavelength of the incident radiation.

Description

[0085] The invention will be described in greater detail on the basis of the following figures; in the figures:

[0086] FIG. 1 shows a representation of a schematic cross section through a preferred embodiment of the invention

[0087] FIG. 2 shows a representation of an alternative embodiment of the invention

[0088] FIG. 3 shows an illustration of an exemplary design of the absorption spectrum by means of a variation in the proportions of the alloy partners of a semiconductor alloy

[0089] FIG. 1 shows a schematic cross section through a preferred embodiment of the invention (10) and in particular a side view of a preferred embodiment of the proposed device (10). A layer structure (16) is shown which comprises absorption elements (12, 14) and contacts (18a, 18b, 18c). The layer structure (16) shown in FIG. 1 terminates at the top with an upper or first contact (18a). A photoresistive layer, which preferably forms the upper absorption element (12), is arranged below the first contact (18a). The second or middle contact (18b) is arranged below the upper absorber (12). It is preferred in terms of the invention that a photon current I1 can be measured between the first contact (18a) and the second contact (18b), which is brought into connection with the upper absorption element (12), wherein a voltage V1 can be applied to the first contact (18a) and a voltage V2 can be applied to the second contact (18b). The lower absorption element (14) is arranged below the second contact (18b). The third or lower contact (18c) is arranged below the lower absorber (14), wherein the five layers mentioned (12, 14, 18a, 18b, and 18c) form the layer structure (16) of the wavemeter (10), wherein the layer structure (16) can preferably be arranged on a substrate (20).

[0090] FIG. 2 shows an alternative embodiment of the invention. In particular, FIG. 2 shows a layer structure (16) in which the absorption elements (12, 14) are arranged on different sides of a substrate (20). In the exemplary structure shown in FIG. 2, the upper absorption element (12) is arranged on an upper side of the substrate (20), while the lower absorption element (14) is arranged on a lower side of the substrate (20). Contacts (18a, b, c) or contact layers can preferably be arranged between each of the absorption elements (12, 14) and the substrate (20). The entirety of the contact layers 18a, b, c is preferably described in the description of the figures and the claims by the reference symbol “18”. In terms of this embodiment of the invention, it is preferred that the photosignals, in particular the photocurrents, are measured between two contacts (18) which each surround the first absorption element (12) and the second absorption element (14). According to the invention, it is very particularly preferred that the first photosignal, which is preferably formed by a first photocurrent I1, is measured between the two contacts (18) which surround the first absorption element (12). According to the invention, it is also preferred that the second photosignal, which is preferably formed by a second photocurrent I2, is measured between the two contacts (18) which surround the second absorption element (14). The photosignal is preferably induced in each case in that charge carriers are released by the incident radiation in the absorption element (12, 14), wherein the charge carriers move within the absorption element (12, 14) due to the applied voltage in an oriented movement from one contact (18) to the other contact (18). This charge carrier current can preferably be measured as a photocurrent.

[0091] FIG. 3 illustrates, by way of example, a design or the setting option of an absorption spectrum by means of a variation of the proportions of the alloy partners of a semiconductor alloy.

[0092] By way of example, the mode of operation will be described using the example of a (Mg, Zn)O system, wherein the principles explained can be applied analogously to other semiconductor alloy systems. In the (Mg, Zn)O mixed semiconductor having the chemical formula Mg.sub.xZn.sub.1-xO, x indicates the Mg content.

[0093] In FIG. 3, the schematic absorption spectra for x=0 (i.e., pure ZnO) and x=0.4 (i.e., Mg.sub.0.4Zn.sub.0.6O) are shown as solid lines (1) and (4), respectively. The absorption edge for x=0 extends approximately in the spectral range of 3.25-3.45 eV. The absorption edge for x=0.4 extends approximately in the spectral range of 4.0-4.2 eV. If the chemical concentration is varied continuously and linearly in a layer from x=0 to x=0.4 during growth (vertical material gradient), the result is the absorption spectrum (2) shown by dashed lines. Here the absorption increases continuously over the entire broad spectral range from approximately 3.3-4.2 eV between the absorption edges of ZnO and Mg.sub.0.4Zn.sub.0.6O. If the chemical concentration is varied continuously and linearly in a layer from x=0.2 to x=0.4, the result is the absorption spectrum (3) shown by dot-dash lines. Here the width of the spectral range of the absorption edge is now smaller, approximately 3.6-4.2 eV.

[0094] By means of variation of the alloy partners of the semiconductor system to set the material gradient, a wavelength-dependent absorption coefficient can thus be set for a preferred detection range. In the case of an upper absorption element having an absorption spectrum (2), the detection range would extend, for example, from 3.3 eV to 4.2 eV and therefore over a spectral range of almost 1 eV. The lower absorption element will preferably have an absorption coefficient that is essentially wavelength-independent over the detection range. In relation to the example, Mg.sub.0.0Zn.sub.1.0O, i.e. pure ZnO, would be suitable, which from 3.3. eV has a high absorption coefficient. Alternatively, in particular other semiconductors or semiconductor alloys would also be conceivable, whose absorption edge is preferably below 3.3 eV.

LIST OF REFERENCE SIGNS

[0095] 10 device, in particular wavemeter [0096] 12 upper absorption element [0097] 14 lower absorption element [0098] 16 layer structure [0099] 18 contacts (a: first contact, b: second contact, c: third contact) [0100] 20 substrate