VCSEL for emitting laser light

Abstract

A VCSEL (10) for emitting a laser beam, having a main element (12) having a mesa portion (14) including a stack of different layers (19) stacked in a stacking direction (18), a light emitting region (22) being formed on a top surface (24) of the mesa portion (14), laser light generated in an active layer (20) in the stack emerging from the light emitting region (22), and an electrical contact (26) for feeding electrical energy to the active layer (20) being provided on the main element (12), at least one side portion (28) of the electrical contact (26) being disposed on a side surface (30) of the main element (12), the side surface (30) being oriented transversely to the layer (19), a VCSEL (10) is disclosed. Also disclosed is a VCSEL array (46), and a method for producing the VCSEL (10).

Description

Technical Field

[0001] The present invention relates to a VCSEL for emitting laser light. Further, the present invention relates to a VCSEL array having such a VCSEL, and an electric circuit board having such a VCSEL and / or VCSEL array. The present invention further relates to a method for producing such a VCSEL.

Background Art

[0002] VCSELs having electrical contacts for feeding electrical energy are known. These electrical contacts are attached on the upper side portion and / or the lower side portion of the VCSEL (vertical cavity surface emitting laser). This makes it impossible to perform efficient soldering using, for example, a jet soldering process.

[0003] For example, in U.S. Patent No. 6,678,29 (B2), a VCSEL having both a p-type contact and an n-type contact on the light emitting surface is shown. These contacts are connected to an electric circuit board via wires. This makes it impossible to perform a soldering process suitable for mass production.

[0004] The problem to be solved by the present invention is to provide a VCSEL that can be attached onto an electric circuit board by a soldering process suitable for mass production.

Summary of the Invention

[0005] There is provided a VCSEL for emitting laser light, having a main element having a mesa portion having a stack of different layers stacked in a stacking direction, a light emitting region being formed on the top surface of the mesa portion, from which laser light generated in an active layer in the stack appears, and an electrical contact for feeding electrical energy to the active layer being provided on the main element, at least one side portion of the electrical contact being disposed on the side surface of the main element, the side surface being oriented in a lateral direction with respect to the layers.

[0006] The main elements are formed by layers stacked on each other's tops. The mesa portion forms the laser-emitting part of the main elements, with a light-emitting region located on its surface. This surface includes a top surface that forms the outer side of one of a pair of Bragg mirrors, with an active layer in between.

[0007] The electrical contacts contain metal and preferably cover a portion of the side surface of the main element.

[0008] Advantageous embodiments and further developments of the present invention are made possible by means described in the dependent claims.

[0009] Advantageously, the top surface is oriented perpendicular to the lamination direction. The side surfaces are also oriented approximately perpendicular to the top surface, or may form an angle greater than 90° with the top surface.

[0010] It is particularly preferable to install an insulating layer between the side portion of the electrical contact and the side surface. This insulating layer can also function as an adhesive layer, ensuring that the electrical contact adheres to the side surface.

[0011] In a specific developmental form, the electrical contact extends from its lateral portion to the upper lateral portion of the main element. This electrical contact may cover a portion of the top surface at the upper portion.

[0012] Preferably, the side portions of the electrical contacts, which are configured as cathodes or anodes, may be mounted on a common side surface of the mesa portion. This allows both the supply and discharge of electrical energy in the VCSEL to be achieved through connections on the side surface, which may be located, for example, on electrical solder contacts of conductor tracks on an electrical circuit board. For this purpose, the VCSEL may be tilted so that the beam axis of the laser beam is oriented parallel to the extending plane of the electrical circuit board, and the electrical contacts are preferably located between the electrical circuit board and the VCSEL.

[0013] Alternatively or additionally, electrical contacts may be mounted on different sides of the VCSEL. The cathode electrical contacts may be located on the side opposite to the anode electrical contacts.

[0014] To achieve low-stress transfer between the upper and lateral portions of the electrical contact on the top surface, chamfered or rounded portions may be formed in the transition region between the lateral and top surfaces, and the electrical contact portion is positioned on the transition region. The transition region may be created by an etching process, for example, by a combination of isotropic and anisotropic etching processes.

[0015] A solder barrier may be formed on the upper portion of the electrical contact on the top surface of the main element to prevent solder from flowing from the side portion into the light-emitting region. The solder barrier may be attached to the upper portion of the electrical contact in an additional step after the electrical contact has been applied.

[0016] In further exemplary embodiments, at least one electrical contact is formed only on the side surface, without extending to the top surface. This prevents solder from flowing onto the surface of the main element, as the metallized portion of the electrical contact does not reach the top surface.

[0017] Furthermore, a VCSEL array may be formed by VCSELs and have at least two main elements, each of which has at least one side portion of an electrical contact on its side surface. The side portions may be mounted on side surfaces facing opposite directions. Alternatively, the side portions may be arranged on side surfaces facing the same direction.

[0018] Furthermore, an electrical circuit board having a VCSEL and / or a VCSEL array may be provided, wherein the VCSEL or VCSEL array is mounted on a side surface of the electrical circuit board so that its side portion can be soldered onto the solder contacts of the electrical circuit board.

[0019] Furthermore, a method is proposed for generating a VCSEL in which a main element is arranged on a wafer, a trench is formed next to the main element, the trench creates a side surface on the main element, and the side surface provides a side portion of an electrical contact assigned to the mesa portion of the main element. For example, an insulating layer containing silicon may be applied first, and a metal adhesive layer containing titanium, for example, may be applied to this insulating layer. Electrical contacts, which may be made of gold, may be applied to the adhesive layer.

[0020] Advantageously, a trench may be formed between two main elements, its side surface being coated, and the two main elements being separated from each other by performing a separating cut along the trench, the separating cut leaving the side portion on the side surface. Specifically, the trench is not completely filled.

[0021] In another embodiment, the trench may be completely filled with metal so that the side surfaces are also coated with metal. Alternatively, only one side surface within the trench may be coated.

[0022] Preferably, after filling the trench, portions adjacent to the trench that reach the trench may be removed so as to expose the main element having a metal-coated side surface, and as a result, the metal forming the side portion may be in contact. As a result, portions adjacent to the trench are removed and the side portion is exposed.

[0023] The present invention will be described in more detail below based on exemplary embodiments with reference to the relevant drawings. Directional indications in the following description should be understood according to the reading direction of the drawings. Upper and lower positional indications should be understood according to the drawings. [Brief explanation of the drawing]

[0024] [Figure 1] This shows a VCSEL in which electrical contacts are located on both the side and top surfaces of the main element. [Figure 2]A VCSEL having electrical contacts, with at least one electrical contact disposed only on one side surface of the main element, is shown. [Figure 3] A plan view of a VCSEL according to FIG. 1 or 2 is shown. [Figure 4] A plan view of a VCSEL array having a VCSEL according to FIG. 1 or 2 is shown. [Figure 5] A first embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 6] A first embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 7] A first embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 8] A first embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 9] A first embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 10] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 11] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 12] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 13] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 14] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 15] A second embodiment of a method for generating a side portion on the side surface of the main element is shown. [Figure 16] A schematic diagram of an electric circuit board having two different arrangement deformation forms of a VCSEL is shown.

Embodiments for Carrying Out the Invention

[0025] Figure 1 shows a VCSEL (Vertical Cavity Surface Emitting Laser) 10 that emits laser light. The VCSEL 10 has a main element 12 having a mesa portion 14. The main element 12, and therefore the mesa portion 14, is made from a laminate 16 of different layers 19 stacked in the stacking direction 18.

[0026] Layer 19 performs a different function, and therefore the mesa portion 14 has a pair of Bragg mirrors, with an active layer 20 positioned between the Bragg mirrors. The active layer 20 generates photons that emerge as laser light from the light-emitting region 22. The light-emitting region 22 is on the surface of the mesa portion 14. This surface includes a top surface 24 on the upper side portion 25 of the VCSEL, which is the outer side portion of the upper Bragg mirror.

[0027] Electrical contacts 26 for supplying electrical energy to the active layer 20 are provided on the main element 12. The electrical contacts 26 are configured as an anode 33 and a cathode 29 and have metal portions. Furthermore, at least one of the electrical contacts 26 has a side portion 28 located on the side surface 30 of the main element 12. The side surface 30 is oriented transversely to the top surface 24 on the main element 12. Preferably, the side surface 30 is oriented perpendicular to the top surface 24. Alternatively, at least a portion of the side surface 30 may form an angle greater than 90° with the top surface 24.

[0028] The electrical contacts 26 preferably contain gold, which is applied in any case to the titanium-containing adhesive layer, and the electrical contacts 26 cover only a portion of the side surface 30 of the main element 12 by at least one side portion 28. The side portion 28 may be in the form of a strip. Only one side portion 28 may be provided for each main element 12. The titanium-containing adhesive layer is applied to the insulating layer 31.

[0029] The main element 12 of the VCSEL 10 has a substrate 32 on which a laminate 16 is disposed. In a simple embodiment, the mesa portion 14 is separated from the rest of the main element 12 by a groove 34. A chamfered or rounded portion is formed in the transition region 36 between the top surface 24 and the side surface 30 of the upper side portion 25 of the main element 12. The groove 34 is filled with a material that forms an insulating layer 31. The insulating layer 31 beneath the titanium-containing adhesive layer is continuously connected to the material in the groove 34.

[0030] The upper portion 35 of the electrical contact 26 is located on the top surface 24. The electrical contact 26 extends from the top surface 24 to the side surface 30, and the portion of the electrical contact 26 is located on the transition region 36 such that it is situated between the upper portion 35 and the side portion 28.

[0031] On the upper side portion 25, a solder barrier 38 is placed over the electrical contacts 26 to prevent solder from flowing from the side portion 28 to the light-emitting region 22 on the top surface 24 of the main element 12, for example, due to the surface tension of the solder. The solder barrier 38 is deposited on the electrical contacts 26 by an additional process.

[0032] The exemplary VCSEL 10 in Figure 1 has a substrate 32 on which a laminate 16 is placed. The laminate 16 does not cover the entire substrate 32, and therefore a step is formed. The top surface 24 is formed on the higher side of the step. The upper portion 35 of the cathode 29 is located on the lower side of the step, and an ohmic contact 37 is formed between the upper portion 35 of the cathode 29 and the substrate 32. The electrical contact 26 extends from the upper portion 35 to the side surface 30 on the main element 12, and the portion of the electrical contact 26 covers a transition region 36 formed on the substrate 32.

[0033] Preferably, the anode 33 is positioned as an electrical contact 26 on the side of the VCSEL 10 opposite the cathode 29. The side portion 28 extends along the side surface 30 that extends from the substrate 32 to the laminate 16. A transition region 36 is formed on the laminate 16. The upper portion 35 extends to the light-emitting region 22. A shoulder portion 40 is formed on the lower side of the substrate 32. The shoulder portion 40 creates a corner between the side surface 30 and the surface of the shoulder portion 40. The side portion 28 reaches the corner.

[0034] Figure 2 shows a further exemplary embodiment in which the cathode 29 is mounted on the side surface 30 of the main element 12 such that it does not extend to the upper side portion 25 of the main element 12. The cathode 29 is formed by a side portion 28, and there is no upper portion. An ohmic contact 37 is located on the side surface 30 of the main element 12, and this ohmic contact 37 may be formed only on the substrate 32. Preferably, the side portion 28 does not extend to the laminate 16. The cathode 28 is configured according to the exemplary embodiment of Figure 1.

[0035] Figure 3 shows a plan view of the VCSEL 10 having side portions 28 on both sides 42. The side portions 28 are structured according to Figure 1 or Figure 2. The anode 33 and cathode 29 extend from the upper side portion 25 to the side surface 30. An elongated solder barrier 38 is positioned on the upper portion 35. The solder barrier 38 may contain titanium oxide or silicon nitride. Furthermore, a longitudinal notch may be provided along the longitudinally extending portion of the solder barrier 38. Preferably, the solder barrier 38 is positioned closer to the transition region 36 than to the opposite end 39 of the upper portion 35. Furthermore, a test contact surface 44 may be provided on the upper portion 35 so that the functionality of the VCSEL 10 can be tested in the factory after the VCSEL 10 has been manufactured.

[0036] Figure 4 shows a VCSEL array 46 having multiple light-emitting regions 22. For each light-emitting region 22, a mesa portion 14 or a separate principal element 12 may be provided, and these are arranged on the VCSEL array 46. Side portions 28 are formed on the side surface 30 of each principal element 12 or mesa portion 14. In this case, the anodes 33 are arranged alternately on opposite side surfaces 28 as side portions 28. As a mere embodiment, three principal elements 12 arranged along a virtual line are arranged on the VCSEL array 46. The side portions 28 are arranged on sides opposite each other with respect to the virtual line. The side portions 28 of two outer principal elements 12 are arranged on the same side with respect to the virtual line 47. The central principal element 12 has side portions 28 oriented in the opposite direction. The cathodes 29 of the VCSEL array 46 are located on both sides of the VCSEL array 46 and are not assigned to a single principal element 12. As a simple example, the cathode 29 is located at the longitudinal end of the VCSEL array 46.

[0037] Figures 5-9 show a first exemplary embodiment of a method for generating a VCSEL 10 or a VCSEL array 46.

[0038] Figure 5 shows that the main elements 12, separated by trenches 49, are formed on the wafer 48 during the lithography-etching process. The etching direction 50 is indicated by an arrow. Two main elements 12 are shown as examples. The ohmic contacts 37 on the upper side 25 of the anode 33 and cathode 29 are generated by metallization.

[0039] Figure 6 shows the passivation process, which involves the subsequent exposure of the anode 33 and cathode 29 by etching. Passivation is achieved, for example, by silicon nitride coating. In the upper side portion 25, the metallized portion is exposed by the etching process.

[0040] In Figure 7, the side surface 30 within the trench 49 is coated with a metal such as gold, forming the side portions 28 of the cathode 29 and anode 33. The corresponding upper portion 35 is also formed. An adhesive layer for the metallized portion can be provided by creating a seed layer applied by sputter deposition or atomic layer deposition. The cathode 29 and anode 33 can be generated by this metallized portion. The final shape of the electrical contacts can be predetermined by a lithography mask.

[0041] In Figure 8, a solder barrier 38 is additionally applied and positioned on the upper portion 35.

[0042] In Figure 9, the trenches 49 are further deepened by a plasma etching process using a lithography mask until the substrate 32 is separated by this separation process, so that the main elements 12 are separated from each other.

[0043] A second exemplary embodiment of a method for generating a VCSEL 10 or a VCSEL array 46 is shown in Figures 10-15.

[0044] In Figure 10, the main element 12 is defined by etched trenches 49 defined by a lithography mask. In addition to the trenches 49, a portion 50 is formed which will be sacrificed in a subsequent process. This portion 50 extends to the trenches 49.

[0045] In Figure 11, passivation is applied according to Figure 6, and the etching process exposes the previously created metal contacts.

[0046] According to Figure 12, the trench 49 is completely filled with a metal such as gold.

[0047] As a result, the side surface 30 is covered with metal.

[0048] After the trench 49 is completely filled with metal and the side surface 30 is covered, an isotropic etching process is performed along the axis of the lamination direction 18 according to Figure 13, thereby creating an opening 52 in the portion 50 that is perpendicular to the layers of the laminate.

[0049] Next, as shown in Figure 14, an anisotropic etching process is performed to enlarge the opening 52. Gallium arsenide and silicon nitride can be anisotropically etched.

[0050] Finally, the separation process corresponding to the process in Figure 9 is performed by plasma etching as shown in Figure 15.

[0051] Figure 16 shows a schematic diagram of the electrical circuit board 54 on which the two VCSELs 10 are located.

[0052] Figure 16A shows a VCSEL 10 corresponding to an exemplary embodiment of the preceding figure. In this exemplary embodiment, the laser axis 60 on which the laser light substantially propagates is oriented parallel to the axis of the stacking direction 18. In this case, the laser axis 60 is oriented perpendicular to the electrical circuit board 54. The light-emitting region 22 is located on the side of the VCSEL 10 opposite to the electrical circuit board 54. The side portions 28 of the electrical contacts 26 are positioned on the side surface 30 and oriented perpendicular to the main extending direction of the electrical circuit board 54. The side portions 28 are positioned in the region of the electrical conductor track 56 to which they are soldered. The cathode 29 is soldered to the solder contact of the conductor track 56 assigned to the cathode 29. The anode 33 is soldered to the solder contact of a portion of the conductor track 56 assigned to the conductor track 56 assigned to the anode 33. The solder forms a meniscus-shaped solder joint 58 at the corner between the conductor track 56 and the side portion 28. The solder joint 58 may be concave in the form of a groove, as shown in Figure 16A, or alternatively, convex. The side portions 28 are located on both sides of the VCSEL 10, as is merely an embodiment. Alternatively, the side portions 28 may be located on the same side surface 30 of the VCSEL 10, or on side surfaces separated by a common corner.

[0053] In the exemplary embodiment of Figure 16B, the VCSEL 10 is oriented so that the laser axis 60 is parallel to the main extending surface of the electrical circuit board 54. The electrical contacts 26 are positioned between the conductor track 56 and the main element 12 of the VCSEL 10, and the solder preferably forms a flat solder joint 58. Due to the inclined position of the VCSEL 10 and the stacking direction 18, which is oriented parallel to the main extending surface of the electrical circuit board 54, the laser light from the light-emitting region 22 propagates substantially parallel to the electrical circuit board 54. In an alternative embodiment of Figure 16B, the side portion 28 may be mounted on the side surface 30 of the VCSEL 10, which is oriented perpendicular to the main extending surface of the electrical circuit board 54, thereby creating a concave or convex solder joint 58 at the corner between the conductor track 56 and the side portion 28.

Claims

1. A VCSEL (10) for emitting laser light, having a main element (12) having a mesa portion (14) having a stack of layers (19) having different functions stacked in the stacking direction (18), a light-emitting region (22) formed on the top surface (24) of the mesa portion (14), the laser light generated in the active layer (20) in the stack emerging from the light-emitting region (22), and an electrical contact (26) for supplying electrical energy to the active layer (20) VCSEL (10), provided on the main element (12), wherein at least one side portion (28) of an electrical contact (26) is positioned on the side surface (30) of the main element (12), the side surface (30) is oriented in a direction transverse to the layer (19), and the side portions (28) of the electrical contacts, which are configured as a cathode (29) and an anode (33), are mounted on the same side surface (30) of the main element (12).

2. The VCSEL (10) according to claim 1, characterized in that the top surface (24) is oriented so as to be perpendicular to the stacking direction (18).

3. The VCSEL (10) according to claim 1 or 2, characterized in that an insulating layer (31) is attached between the side portion (28) and the side surface (30) of the electrical contact (26).

4. The VCSEL (10) according to claim 1 or 2, characterized in that the electrical contact (26) extends from its side portion (28) to the upper side (25) of the main element (12) outside the upper Bragg mirror of the mesa portion (14).

5. The VCSEL (10) according to claim 1 or 2, characterized in that a chamfered or rounded portion is formed in the transition portion (36) between the side surface (30) and the top surface (24), and a portion of the electrical contact (26) is arranged on the transition portion (36).

6. The VCSEL (10) according to claim 1 or 2, characterized in that a solder barrier (38) is formed on the electrical contact (26) on the top surface (24) of the mesa portion (14), preventing solder from flowing from the side portion (28) to the light-emitting region (22).

7. The VCSEL (10) according to claim 1 or 2, characterized in that the electrical contact (26) is formed only on the side surface (30) and does not extend to the top surface (24).

8. A VCSEL array (46) having a VCSEL (10) preferably according to claim 1 or 2, wherein each of the main elements (12) has at least two main elements (12), and each main element (12) has at least one side portion (28) of an electrical contact (26) on its side surface (30).

9. An electrical circuit board (54) having a VCSEL (10) according to claim 1 or 2, wherein the side portion (28) of the VCSEL (10) is located within the area of ​​the conductor track (56) of the electrical circuit board (54) such that the side portion (28) can be soldered onto the solder contacts of the electrical circuit board (54).

10. The electrical circuit board (54) according to claim 9, characterized in that at least one side portion (28) of the solder joint (58) is oriented perpendicular to the conductor track (56) and / or is placed on the conductor track (56).

11. A method for generating a VCSEL (10) according to claim 1 or 2, characterized in that a main element (12) having a mesa portion (14) is placed on a wafer (48), a trench (49) is formed next to the main element (12), the trench generates a side surface (30) on the main element (12), and the side surface (30) is provided with a side portion (28) of an electrical contact (26) assigned to the mesa portion (14).

12. The method according to claim 11, characterized in that the trench (49) is formed between two main elements (12), the side surface (30) is coated, the two main elements (12) are separated from each other by separating and cutting along the trench (49), and the separating and cutting leaves the side portion (28) on the side surface (30).

13. The method according to claim 11, characterized in that the trench (49) is completely filled with metal, and thereby the side surface (30) is also covered with metal.

14. The method according to claim 13, characterized in that, after the trench (49) is filled, a portion adjacent to the trench (49) that reaches the trench (49) is removed so that the mesa portion (14) having the metal-covered side surface (30) is exposed, and as a result the metal can come into contact with it.

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