RADIATION-EMITTING SEMICONDUCTOR LASER AND METHOD FOR OPERATING A RADIATION-EMITTING SEMICONDUCTOR LASER

Abstract

The invention relates to a radiation-emitting semiconductor laser comprising—a semiconductor body comprising an active region which is designed to generate electromagnetic radiation, —a resonator which has a first end region and a second end region, and —a first sensor layer which is designed to measure the temperature of the semiconductor body, wherein the active region is located in the resonator in such a way that the electromagnetic radiation generated in the active region during operation is electromagnetic laser radiation, and —the first sensor layer is located in the first active end region of the resonator. The invention also relates to a method for operating a radiation-emitting semiconductor laser.

Claims

1. A radiation-emitting semiconductor laser, comprising a semiconductor body comprising an active region configured for generating electromagnetic radiation, a resonator comprising a first end region and a second end region, and a first sensor layer configured for measuring a temperature of the semiconductor body, wherein the active region is arranged in the resonator in such a way that the electromagnetic radiation generated in the active region during operation is electromagnetic laser radiation, and the first sensor layer is arranged on the first end region of the resonator.

2. The radiation-emitting semiconductor laser as claimed in claim 1, wherein the first end region has a first mirror arranged on a first main surface of the semiconductor body, and the second end region has a second mirror arranged on a second main surface of the semiconductor body.

3. The radiation-emitting semiconductor laser as claimed in claim 1, wherein a second sensor layer is arranged on the second end region of the resonator.

4. The radiation-emitting semiconductor laser as claimed in claim 1, wherein the semiconductor body has a ridge having a top surface and side surfaces adjoining the latter, the semiconductor body has a recessed outer surface arranged laterally with respect to the ridge, and the first sensor layer covers the top surface, the side surfaces and the recessed outer surface.

5. The radiation-emitting semiconductor laser as claimed in the preceding claim 4, wherein a first electrical contact is arranged on the ridge and the recessed outer surface, and the first end region is free of the first electrical contact.

6. The radiation-emitting semiconductor laser as claimed in claim 1, wherein a first passivation layer is arranged between the first sensor layer and the semiconductor body.

7. The radiation-emitting semiconductor laser as claimed in claim 6, wherein the first passivation layer covers the top surface of the ridge, the side surfaces of the ridge and the recessed outer surface of the semiconductor body.

8. The radiation-emitting semiconductor laser as claimed in claim 6, wherein the top surface of the ridge is free of the first passivation layer.

9. The radiation-emitting semiconductor laser as claimed in claim 8, wherein the first sensor layer is in direct contact with the semiconductor body.

10. The radiation-emitting semiconductor laser as claimed in claim 1, wherein a second passivation layer is arranged on the first sensor layer, and the second passivation layer covers the top surface of the ridge and the side surfaces of the ridge.

11. The radiation-emitting semiconductor laser as claimed in claim 1, wherein at least one second electrical contact is arranged on the first sensor layer.

12. The radiation-emitting semiconductor laser as claimed in claim 11, wherein the second electrical contact forms a common electrical contact that is also configured for energizing the semiconductor body.

13. The radiation-emitting semiconductor laser as claimed in claim 1, wherein the first sensor layer comprises a metal, a metal oxide and/or a semiconductor material.

14. A method for operating a radiation-emitting semiconductor laser as claimed in claim 1, wherein the first sensor layer has a first resistance dependent on a temperature of the semiconductor body in the first end region, and the radiation-emitting semiconductor laser is operated in a manner dependent on the first resistance.

15. The method as claimed in claim 14, wherein the first resistance and the semiconductor laser are connected in parallel.

16. The method as claimed in claim 14, wherein the first resistance and the semiconductor laser are connected in series.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0084] In the figures:

[0085] FIGS. 1, 2 and 3 show schematic illustrations of a radiation-emitting semiconductor laser each in accordance with one exemplary embodiment,

[0086] FIGS. 4, 5, 6, 7, 8 and 9 show a schematic sectional illustration of a radiation-emitting semiconductor laser each in accordance with one exemplary embodiment,

[0087] FIG. 10 shows a schematic illustration of a radiation-emitting semiconductor laser in accordance with one exemplary embodiment,

[0088] FIGS. 11, 12 and 13 show schematic illustrations in plan view of a radiation-emitting semiconductor laser each in accordance with one exemplary embodiment,

[0089] FIGS. 14 and 15 show schematic illustrations of an equivalent circuit diagram of a radiation-emitting semiconductor laser each in accordance with one exemplary embodiment, and

[0090] FIGS. 16 and 17 show exemplary illustrations of a resistance as a function of a temperature of a respective material of a sensor layer.

DETAILED DESCRIPTION

[0091] Elements that are identical, of identical type or act identically are provided with the same reference signs in the figures. The figures and the size relationships of the elements illustrated in the figures along one another should not be regarded as to scale. Rather, individual elements may be illustrated with an exaggerated size in order to enable better illustration and/or in order to afford a better understanding.

[0092] The radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 1 comprises a semiconductor body 2. The semiconductor body 2 is bounded by a first main surface 7 at its front side and by a second main surface 8 at its rear side. Furthermore, the semiconductor body 2 comprises an active region 3, which is described for example in association with FIG. 4. The active region 3 is arranged in a resonator 4 of the radiation-emitting semiconductor laser 1 in such a way that the electromagnetic radiation generated in the active region 3 during operation is electromagnetic laser radiation.

[0093] Furthermore, a first mirror 11 is arranged on the first main surface 7. The first mirror 11 is partly transmissive to the electromagnetic laser radiation. Moreover, a second mirror 12 is arranged on the second main surface 8. In contrast to the first mirror 11, the second mirror 12 is configured such that it is highly reflective for the electromagnetic laser radiation. In this exemplary embodiment, the electromagnetic laser radiation propagates between the first main surface 7 and the second main surface 8 along a main extension plane of the active region. The first main surface 7 is a radiation exit surface for electromagnetic laser radiation.

[0094] Moreover, a first electrical contact 17 is arranged on the semiconductor body 2. The first electrical contact 17 is in electrically conductive contact with the semiconductor body 2. In this case, the first electrical contact 17 serves for impressing current into the semiconductor body 2, the active region 3 being electrically pumped by this impressing of current.

[0095] Furthermore, a first sensor layer 9 is arranged on the semiconductor body 2 in a first end region 5 of the resonator 4, said first sensor layer being configured for measuring a temperature of the semiconductor body 2. The first sensor layer 9 is thus a temperature sensor. The first sensor layer 9 is shaped as a strip having for example a width of approximately 15 micrometers, a length of approximately 80 micrometers and a thickness in a vertical direction of approximately 800 nanometers.

[0096] A second electrical contact 18 is arranged on the first sensor layer 9 in a first edge region, said second electrical contact being in direct electrically conductive contact with the first sensor layer 9. Furthermore, a third electrical contact 19 is arranged on the first sensor layer 9 in an edge region situated opposite the first edge region, said electrical contact being in direct electrically conductive contact with the first sensor layer 9.

[0097] By way of example, a resistance of the first sensor layer 9 is able to be read out via the second electrical contact 18 and the third electrical contact 19. The temperature of the semiconductor body 2 in the first end region 5 is determinable in a manner dependent on this resistance.

[0098] In this exemplary embodiment, the first end region 5 and a second end region 6, which comprises the second main surface 8, do not overlap the first electrical contact 17 in a lateral direction in plan view. Moreover, the second electrical contact 18 and the third electrical contact 19 do not overlap the first electrical contact 17 in plan view. The second electrical contact 18 and the third electrical contact 19 here are arranged at a distance in a lateral direction and in an electrically insulating manner with respect to the first electrical contact 17.

[0099] In contrast to the exemplary embodiment in FIG. 1, in accordance with the exemplary embodiment in FIG. 2, a second electrical contact 18 is electrically conductively connected to a first electrical contact 17 via a first sensor layer 9 and a third electrical contact 19. Furthermore, the first electrical contact 17 extends as far as a second main surface 8 of the semiconductor body 2.

[0100] In this exemplary embodiment, the second electrical contact 18 forms a common electrical contact that is also configured for energizing the semiconductor body 2. Here the third electrical contact 19 mediates an electrically conductive connection from the second electrical contact 18 to the first electrical contact 17. Here exclusively the second electrical contact 18 is provided for external electrically conductive contacting.

[0101] In contrast to the radiation-emitting semiconductor lasers 1 in accordance with the exemplary embodiments in FIGS. 1 and 2, the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 3 comprises a second sensor layer 10. The second sensor layer 10 is arranged on a semiconductor body 2 in a second end region 6. The second sensor layer 10 is configured here for measuring a temperature of the semiconductor body 2 in the second end region 6. The second sensor layer 10 is thus likewise a temperature sensor.

[0102] The second sensor layer 10 is furthermore shaped as a strip having for example a width of approximately 15 micrometers, a length of approximately 80 micrometers and a thickness in a vertical direction of approximately 800 nanometers.

[0103] By way of example, a further second electrical contact 23 and a further third electrical contact 24 are arranged on the second sensor layer 10, as described for example in association with the exemplary embodiment in FIG. 13. By way of example, a resistance of the second sensor layer 10 is able to be read out via the further second electrical contact 23 and the further third electrical contact 24. The temperature of the semiconductor body 2 in the second end region 6 is determinable in a manner dependent on this resistance.

[0104] In accordance with the exemplary embodiment in FIG. 4, the radiation-emitting semiconductor laser 1 has a semiconductor body 2 having a ridge 13. The ridge 13 is formed by an elevated region of the semiconductor body 2. The ridge 13 has a top surface 14 and side surfaces 15 adjoining the latter. The ridge 13 extends in a lateral direction between the first main surface 7 and the second main surface 8, as described in association with the exemplary embodiments in FIGS. 1 to 3.

[0105] The semiconductor body 2 comprises a first semiconductor layer sequence 25 of a first conductivity type and a second semiconductor layer sequence 26 of a second conductivity type, which is different than the first conductivity type. The first conductivity type is for example a p-conducting type and the second conductivity type is for example an n-conducting type.

[0106] A recessed outer surface 16 of the semiconductor body 2 adjoins the side surfaces 15 of the ridge 13. Here the top surface 14 and the side surfaces 15 and also the recessed outer surface 16 form a step profile.

[0107] Between the first sensor layer 9 and the semiconductor body 2, a first passivation layer 20 is arranged in a first end region 5, described in greater detail in FIGS. 1 to 3. The first passivation layer 20 completely covers the recessed outer surface 16 of the semiconductor body 2 in the first end region 5. Furthermore, the first passivation layer 20 completely covers the top surface 14 and the side surfaces 15 of the ridge 13 in the first end region 5. The first sensor layer 9 is thus arranged completely on the first passivation layer 20.

[0108] The first passivation layer 20 is configured such that it is electrically insulating and has for example a thickness in a vertical direction of approximately 0.5 micrometer.

[0109] Furthermore, a second passivation layer 21 is arranged on the first sensor layer 9. The second passivation layer 21 here does not completely cover the first sensor layer 9. That is to say that a first edge region and a second edge region of the first sensor layer 9, said second edge region being situated opposite the first edge region, are free of the second passivation layer 21. A second electrical contact 18 is arranged on the first edge region of the first sensor layer 9, and a third electrical contact 19 is arranged on the second edge region of the first sensor layer 9. The edge regions of the first sensor layer 9 here are configured for electrically contacting the first sensor layer 9.

[0110] The second passivation layer 21 is likewise configured such that it is electrically insulating and has for example a thickness in a vertical direction of approximately 1 micrometer.

[0111] The first passivation layer 20, the first sensor layer 9 and the second passivation layer 21 are arranged one above another in each case in a positively locking manner. That is to say that the first passivation layer 20, the first sensor layer 9 and the second passivation layer 21 in each case copy the step profile of the ridge 13.

[0112] In contrast to the exemplary embodiment in FIG. 4, a top surface 14 of a ridge 13 of the semiconductor body 2 in accordance with the exemplary embodiment in FIG. 5 is free of a first passivation layer 20. In accordance with this exemplary embodiment, the top surface 14 of the ridge 13 is completely free of the first passivation layer 20. That is to say that the first sensor layer 9 is in direct contact with the top surface 14 of the ridge 13 and thus with the semiconductor body 2.

[0113] In contrast to the exemplary embodiments in FIGS. 4 to 5, the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 6 does not comprise a first passivation layer 20. That is to say that the first sensor layer 9 is in direct contact with the top surface 14 and the side surfaces 15 of the ridge 13 and also with the recessed outer surface 16 of the semiconductor body 2.

[0114] In contrast to the exemplary embodiment in accordance with FIG. 5, the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 7 does not comprise a second passivation layer 21. In this exemplary embodiment, the first sensor layer 9 is freely accessible from outside.

[0115] In contrast to FIG. 4, the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 8 does not comprise a second passivation layer 21. In this exemplary embodiment, the first sensor layer 9 is likewise freely accessible from outside.

[0116] In accordance with the exemplary embodiment in FIG. 9, in contrast to FIG. 4, a contact metal layer 22 is arranged between a first passivation layer 20 and a semiconductor body 2. In this exemplary embodiment, the contact metal layer 22 completely covers a top surface 14 of a ridge 13.

[0117] In accordance with the exemplary embodiment in FIG. 10, in contrast to the exemplary embodiment in FIG. 1, a first main surface 7 and a second main surface 8 of the radiation-emitting semiconductor laser 1 run parallel to a main extension plane of the active region 3. A partly transmissive first mirror 11 is arranged on the first main surface 7 and a highly reflective second mirror 12 is arranged on the second main surface 8. In this exemplary embodiment, electromagnetic laser radiation thus propagates between the first main surface 7 and the second main surface 8 perpendicularly to the main extension plane of the active region 3.

[0118] The first main surface 7, which in this exemplary embodiment is parallel to the main extension plane of the semiconductor body 2, is a radiation exit surface for electromagnetic laser radiation. In this exemplary embodiment, the radiation-emitting semiconductor laser is a vertical cavity surface emitting laser (for short “VCSEL”).

[0119] The first sensor layer 9 is arranged on the first main surface 7 of the semiconductor body 2 in a first end region 5. By way of example, the first sensor layer 9 is in direct contact with the semiconductor body 2.

[0120] A first passivation layer 20 of the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 11 is arranged over the whole area on side surfaces 15 of a ridge 13 and a recessed outer surface 16 of a semiconductor body 2, the ridge 13 being described in greater detail for example in association with FIG. 4.

[0121] Furthermore, a first electrical contact 17 is arranged on the ridge 13 and the recessed outer surface 16. The first electrical contact 17 covers the ridge 13 and the recessed outer surface 16 at least regionally. The first passivation layer 20 is arranged regionally between the first electrical contact 17 and the semiconductor body 2. In this case, the first passivation layer 20 is not arranged on the top surface 14 of the ridge 13 covered by the first electrical contact 17. That is to say that in this region the first electrical contact 17 is in electrically conductive contact with the top surface 14 of the ridge 13.

[0122] In accordance with the exemplary embodiment in FIG. 12, a contact metal layer 22 completely covers a top surface 14 of the ridge 13. Furthermore, the contact metal layer 22 is arranged exclusively on the top surface 14. Furthermore, the top surface 14 is completely free of a first passivation layer 20.

[0123] In contrast to FIG. 12, the radiation-emitting semiconductor laser 1 in accordance with the exemplary embodiment in FIG. 13 additionally comprises a second sensor layer 10 in a second end region 6.

[0124] The equivalent circuit diagram of the exemplary embodiment in FIG. 14 shows a diode 29, corresponding to a semiconductor body 2 of the radiation-emitting semiconductor laser 1, and a first resistance 27 or a second resistance 28, dropped across a first sensor layer 9 or a second sensor layer 10 during operation. The first resistance 27 or the second resistance 28 is connected in parallel with the diode 29.

[0125] The first resistance 27 is determined by means of a second electrical contact 18 and a third electrical contact 19, as described in greater detail in association with FIG. 1.

[0126] An external device 30 is configured to determine the first resistance 27. A maximum output power applied to the diode 29 for the operation of the radiation-emitting semiconductor laser 1 can subsequently be determined by the external device 29. This maximum output power is then made available to the diode 29.

[0127] In the equivalent circuit diagram in accordance with the exemplary embodiment in FIG. 15, in contrast to the exemplary embodiment in FIG. 14, the diode 29 and the first resistance 27 are connected in series. In this exemplary embodiment, a second electrical contact 18 is electrically conductively connected to a first electrical contact 17 by means of a third electrical contact 19, as described in greater detail in association with FIG. 2. The external device 30 here is configured to provide a maximum output power.

[0128] By way of example, if the first resistance 27 increases as a result of heating, then the maximum output power with which the diode 29 is operated decreases automatically. Advantageously, the maximum output power here does not have to be adapted.

[0129] A thermal characteristic of a material of a sensor layer is plotted in accordance with the diagrams in FIGS. 16 and 17. In the diagrams in FIGS. 16 and 17, values of a resistance R of the respective material in ohms are marked in each case on the y-axis. Temperatures T in ° C. are marked on the x-axis. The resistance R of the respective material is thus plotted against the respective temperature T in each of the diagrams. In the temperature range of approximately 0° C. to approximately 150° C., the thermal characteristic of the resistance R of the materials is substantially linear. The thermal characteristic in accordance with FIG. 16 shows values of the resistance R as a function of a temperature for the metal Ti. FIG. 17 shows a thermal characteristic for the semiconductor Si. By means of n-type doping of Si, values of the resistance R in the same temperature range can be increased by approximately three orders of magnitude.

[0130] The features and exemplary embodiments described in association with the figures can be combined with one another in accordance with further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in association with the figures can alternatively or additionally have further features in accordance with the description in the general part.

[0131] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any novel feature and also any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.