TWM649964U - Thin-film vertical resonant cavity surface emitting laser element - Google Patents

Abstract

The epitaxial structure of the new thin-film vertical resonant cavity surface-emitting laser element sequentially includes N-type Metal contact layer, lower Bragg mirror layer, current limiting layer, active light emitting layer, upper Bragg mirror layer and P-type metal contact layer, P-type metal contact layer, upper Bragg mirror layer, active light emitting layer, current limiting layer, The lower Bragg reflector layer forms a cylinder on one side of the N-type metal contact layer, and the laser light generated by the active light-emitting layer between the upper Bragg reflector layer and the lower Bragg reflector layer is emitted toward the N-type metal contact layer. This new type of resonant cavity surface-emitting laser element does not have a substrate and can be thinned, thereby improving packaging flexibility and improving heat dissipation efficiency, ensuring the luminous efficiency and stability of the resonant cavity surface-emitting laser element.

Description

Thin film vertical resonant cavity surface emitting laser element

A laser element, especially a thin-film vertical resonant cavity surface-emitting laser element.

Vertical Cavity Surface Emitting Laser (VCSEL) is a laser element that emits light from the original surface. Compared with Edge Emitting Laser (EEL), it has a smaller threshold current. , symmetrical divergence angle and easy to make arrays, etc., it is currently widely used in fields such as optical sensing, optical communication and gas detection.

As shown in Figure 3, a traditional VCSEL is disposed on a substrate 51 through an epitaxial process. Relative to the substrate, from bottom to top are an N-type Distributed Bragg Reflector (DBR) layer 52, Active light emitting layer 53, current confinement layer 54, P-type DBR layer 55, etc. When current passes through the active light-emitting layer 53 to generate photons, the light wave is constructively reflected between the P-type DBR layer 55 and the N-type DBR layer 52 to form a laser, and the reflectivity of the lower N-type DBR layer 52 is slightly higher than that of the P-type DBR layer 53 , so that the laser beam passes through the light-emitting hole 540 of the current confinement layer 54 and is emitted from above the P-type DBR layer 55 . The epitaxial structure is covered with a passivation layer 56, and the metal electrode 57 forms an electrical connection with the P-type DBR layer 55 and the N-type DBR layer 52 through the passivation layer opening.

Since the VCSEL structure uses the light-emitting hole 540 formed by the current confinement layer 54 to emit light and localize the current, when the current passes through the light-emitting hole 540, the current density increases and generates more heat energy, and the thermal resistance of the substrate 51 also makes the heat energy easily Accumulated in the epitaxial structure, the temperature of the active light-emitting layer 53 rises, further causing a decrease in optical power and related reliability performance, and even causing component failure. Therefore, solving the heat dissipation problem is the most important key to improving the performance and reliability of laser components.

In view of the fact that existing VCSEL elements need to solve the heat dissipation problem generated near the current-carrying localization layer, this new type proposes a high heat dissipation thin film thermal film vertical resonant cavity surface-emitting laser element, including: an epitaxial structure, including: an upper Bragg Reflector layer; a lower Bragg reflector layer; an active light-emitting layer disposed between the upper Bragg reflector layer and the lower Bragg reflector layer; a current confinement layer disposed on the lower Bragg reflector layer close to the active light-emitting layer A surface has a light-emitting hole; an N-type metal contact layer forms ohmic contact with a surface of the lower Bragg reflector layer away from the active light-emitting layer; and a P-type metal contact layer forms an ohmic contact with the upper Bragg reflector layer A surface away from the active light-emitting layer forms an ohmic contact; wherein the P-type metal contact layer, the upper Bragg mirror layer, the active light-emitting layer, the current confinement layer, and the lower Bragg mirror layer are in the N-type metal contact One side of the layer forms a cylinder.

This new type of high heat dissipation thin film vertical resonant cavity surface-emitting laser element will remove the substrate after completing the process, so the laser light generated by the active light-emitting layer between the lower Bragg reflector layer and the upper Bragg reflector layer It can be emitted from the lower surface of the N-type metal contact layer relative to the current localization layer. Compared with the total thickness of the epitaxial layer and substrate of traditional laser elements, which is 108-160 μm, the new resonant cavity surface-emitting laser element does not have a substrate, so the volume is reduced and the thickness is thinned. After thinning, the main epitaxial layer thickness is 8-10μm, flexible and increased packaging flexibility. Furthermore, the heat energy will not be blocked by the substrate under the N-type metal contact layer, but can be easily dissipated directly from under the N-type metal contact layer, ensuring the heat dissipation performance of the thin-film vertical resonant cavity surface-emitting laser element.

10: Epitaxial structure

10’:Cylinder

11:N-type metal contact layer

12: Lower Bragg mirror layer

13:Current confinement layer

130: Luminous hole

14:Active luminescent layer

141:N type space layer

142:Multiple quantum well space layer

143:P type space layer

15: Upper Bragg mirror layer

16:P-type metal contact layer

21: First metal electrode

210: First metal layer

22: Second metal electrode

23: Photosensitive polymer materials

31: First passivation layer

311:First opening

312:Second opening

32: Second passivation layer

41:Substrate

42:N-type buffer layer

43: Epitaxial sacrificial layer

51:Substrate

52: Lower Bragg mirror layer

53:Active luminescent layer

54:Current confinement layer

55: Upper Bragg mirror layer

56: Passivation layer

57:Metal electrode

Figure 1 is a side cross-sectional view of the new thin-film vertical resonant cavity surface-emitting laser element.

Figures 2A to 2F are cross-sectional views of the manufacturing process of the new thin-film vertical resonant cavity surface-emitting laser element.

Figure 3 is a side cross-sectional view of a conventional vertical resonant cavity surface-emitting laser element.

Please refer to Figure 1. The new thin-film vertical resonant cavity surface-emitting laser element of the present invention includes an epitaxial structure 10. The epitaxial structure 10 sequentially includes an N-type metal contact layer 11 and a Bragg reflector from bottom to top. Mirror layer 12, a current confinement layer 13, an active light emitting layer 14, an upper Bragg reflector layer 15 and a P-type metal contact layer 16. The active light-emitting layer 14 is located between the upper Bragg reflector layer 15 and the lower Bragg reflector layer 12, and the current confinement layer 13 is located on a surface of the lower Bragg reflector layer 12 close to the active light-emitting layer 14, and has a light-emitting hole 130 to allow the current to flow. The energy flows from the active light-emitting layer 14 to the lower Bragg reflector layer 12, and causes the light energy generated by the active light-emitting layer 14 to be emitted through the lower Bragg reflector layer 12 after being resonated by the upper Bragg reflector layer 15 and the lower Bragg reflector layer 12. .

The N-type metal contact layer 11 forms an ohmic contact with a surface of the lower Bragg mirror layer 12 away from the active light-emitting layer 14 , while the P-type metal contact layer 16 forms an ohmic contact with a surface of the upper Bragg mirror layer 15 away from the active light-emitting layer 14 .

Among them, the P-type metal contact layer 16, the upper Bragg mirror layer 15, the active light-emitting layer 14, the current confinement layer 13, and the lower Bragg mirror layer 12 form a cylinder 10' on one side of the N-type metal contact layer 11. The cylinder 10' is a basic light-emitting unit. An array including a plurality of substrate light-emitting units can be disposed simultaneously on the N-type metal contact layer 11 during the manufacturing process to serve as a light-emitting module of a laser device.

In the present invention, the reflectivity of the upper Bragg reflector layer 15 is greater than the reflectivity of the lower Bragg reflector layer 12 , so that the laser is emitted from below the lower Bragg reflector layer 12 . When the upper Bragg mirror layer 15 and the lower Bragg mirror layer 12 have the same energy system design, for example, if they are both Al _x Ga _1-x As/GaAs mirror layers, the number of mirror pairs of the upper Bragg mirror layer 15 is greater than The number of mirror layer pairs of the lower Bragg mirror layer 12. For example, the number of mirror layer pairs of the upper Bragg reflector layer 15 is 35 to 40 pairs, and the reflectivity is greater than 99.8%. The number of mirror layer pairs of the lower Bragg reflector layer 12 is 15 to 21 pairs, and the reflectivity is less than 99.6%. .

Preferably, the thin-film vertical resonant cavity surface-emitting laser element further includes a first metal electrode 21 and a second metal electrode 22. The first metal electrode 21 is disposed on the N-type metal contact layer 11 facing the cylinder 10'. One side is electrically connected to the N-type metal contact layer 11 , and the second metal electrode 22 is disposed on the outside of the cylinder 10 ′ and is electrically connected to the P-type metal contact layer 16 . In addition, it further includes a photosensitive polymer material 23 disposed between the first metal electrode 21 and the second metal electrode 22 to electrically isolate the first metal electrode 21 and the second metal electrode 22 . The actual shapes of the first metal electrode 21, the second metal electrode 22 and the photosensitive polymer material 23 are determined by the wiring design of the semiconductor device, and the present invention is not limited thereto.

Preferably, the thin-film vertical resonant cavity surface-emitting laser element further includes a first passivation layer 31 . The first passivation layer 31 covers the cylinder 10' and the part of the surface of the N-type metal contact layer 11 that is not covered by the cylinder 10'. The first passivation layer 31 has a first opening 311 and a second opening 312. The first opening 311 partially exposes part of the surface of the P-type metal contact layer 16, and the second opening 312 partially exposes the N-type metal contact layer 11. s surface. The first metal electrode 21 is electrically connected to the N-type metal contact layer 11 through the first opening 311 , and the second metal electrode 22 is electrically connected to the P-type metal contact layer 16 through the first opening 311 . In other words, the first passivation layer 31 is located between the outside of the cylinder 10' and the N-type metal contact layer 11 and the first metal electrode 21 and the second metal electrode 22.

Preferably, the thin-film vertical resonant cavity surface-emitting laser element further includes a second passivation layer 32. The second passivation layer 32 is disposed on a surface of the lower Bragg reflector layer 12 to protect the lower Bragg reflector layer 12. surface.

The manufacturing process of the new thin-film vertical resonant cavity surface-emitting laser element of the present invention will be further explained below in Figures 2A to 2F, so as to make the structure of the thin-film vertical resonant cavity surface-emitting laser element clearer.

Please refer to FIG. 2A. First, an N-type buffer layer 42, an epitaxial sacrificial layer 43, an N-type metal contact layer 11, a lower Bragg mirror layer 12, and Active light emitting layer 14 , upper Bragg mirror layer 15 and P-type metal contact layer 16 . Preferably, the substrate 41 is a gallium arsenide (GaAs) substrate. The epitaxial structure of the epitaxial sacrificial layer 43 is, for example, aluminum arsenide (AlAs), and its thickness is 15~30 nm.

Among them, the active light-emitting layer 14 is a composite layer, including an N-type space layer 141, a multiple quantum well space layer 142 and a P-type space layer 143 from bottom to top. In other words, the multiple quantum well space layer 142 is provided between the P-type space layer 143 and the N-type space layer 141 .

It should be noted that in the present invention, the “upper” direction refers to the direction in which the surface of the substrate 41 undergoes the epitaxial process faces, while the “lower” direction refers to the opposite direction of the upper direction.

Please refer to FIG. 2B . The first platform etching (MESA etching) process is performed on the multi-layer epitaxial structure on the substrate 41 . The surface of the P-type metal contact layer 16 is etched to the lower Bragg mirror layer 12 without penetrating the lower Bragg. The mirror layer 12 is reflected to form a cylinder 10'. Further, an oxidation process is performed, and a fixed-depth oxidation process is performed from the side of the cylinder 10' to the junction of the lower Bragg reflector layer 12 and the active light-emitting layer 14, so that the lower Bragg reflector layer 12 is close to the surface of the active light-emitting layer 14. The current confinement layer 13 is formed from the outside to the inside, and the unoxidized portion in the middle of the surface of the lower Bragg reflector layer 12 close to the active light-emitting layer 14 is the light-emitting hole 130 .

Referring to FIG. 2C , a second platform etching is performed on the lower Bragg reflector layer 12 , and the etching continues from the surface of the lower Bragg reflector layer 12 retained in the first platform etching process to the N-type metal contact layer 11 surface, forming a second circular segment with a wider surface close to the N-type metal contact layer 11 cylinder. Furthermore, a first passivation layer 31 is provided. The first passivation layer 31 covers the partial surface of the N-type metal contact layer 11 facing the cylinder 10' and not covered by the cylinder 10' and the cylinder 10'.

Referring to FIG. 2D , an etching process is performed on the first passivation layer 31 to form a first opening 311 and a second opening 312 . The first opening 311 partially exposes part of the surface of the P-type metal contact layer 16 . The two openings 312 partially expose part of the surface of the N-type metal contact layer 11 .

Referring to FIG. 2E , a first metal electrode 21 and a second metal electrode 22 are patterned and spaced apart from each other. The first metal electrode 21 is electrically connected to the N-type metal contact layer 11 through the first metal layer 210 , and the second metal electrode 22 is electrically connected to the P-type metal contact layer 16 . For example, the first metal electrode 21 covers the outside of a part of the cylinder 10' and covers the second opening 312 and the first metal layer 210 therein, so as to be electrically connected to the N-type metal contact layer through the first metal layer 210, and The second metal electrode 22 is wrapped around the outside of another part of the cylinder 10' and covers the first opening 311 to be electrically connected to the P-type metal contact layer. Furthermore, a photosensitive polymer material 23 is disposed between the first metal electrode 21 and the second metal electrode 22 to complete the electrical isolation between the first metal electrode 21 and the second metal electrode 22 .

Referring to FIG. 2F , the epitaxial sacrificial layer 43 together with the substrate 41 is removed from the surface of the N-type metal contact layer 11 away from the cylinder 10'. Preferably, this step involves etching the epitaxial sacrificial layer 43 with a chemical solution such as hydrofluoric acid (HF), so that the substrate 41 is peeled off from the surface of the N-type metal contact layer 11 away from the cylinder 10'. In this way, the epitaxial structure 10 and the substrate 41 are separated, thereby completing the thinning of the laser element. The N-type buffer layer 42 protects the surface of the substrate 41 so that the substrate 41 can be reused.

Finally, a second passivation layer 32 is provided on the exposed surface of the N-type metal contact layer 11 after the substrate 41 is removed to protect the surface of the N-type metal contact layer 11 to complete the novel thin-film vertical resonant cavity surface-emitting laser. element.

In summary, the present invention is a thin-film vertical resonant cavity surface-emitting laser element without a substrate. There is no other material barrier under the N-type metal contact layer 11 except the second passivation layer 32 as a protective layer, so it can emit light during active operation. The current localization layer 13 at the interface between the layer 14 and the lower Bragg mirror layer 12 The heat energy can be effectively dissipated from below the N-type metal contact layer 11 . Furthermore, the first metal electrode 21 and the second metal electrode 22 cover the cylinder 10' of the epitaxial structure 10 as a support material for the entire element, and the thermal energy generated in the cylinder 10' can also be generated by the first metal The electrode 21 and the second metal electrode 22 dissipate heat through transmission, ensuring the heat dissipation efficiency of the resonant cavity surface-emitting laser element.

The above descriptions are only embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above in the form of embodiments, they are not intended to limit the present invention. Any skilled person familiar with the art will not Without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make slight changes or modifications to equivalent embodiments with equivalent changes. However, as long as the content of the technical solution of the present invention is not departed from, the technical content of the present invention shall be modified based on the technical essence of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the new technical solution.

10: Epitaxial structure

10’:Cylinder

11:N-type metal contact layer

12: Lower Bragg mirror layer

13:Current confinement layer

130: Luminous hole

14:Active luminescent layer

141:N type space layer

142:Multiple quantum well space layer

143:P type space layer

15: Upper Bragg mirror layer

16:P-type metal contact layer

21: First metal electrode

22: Second metal electrode

23: Photosensitive polymer materials

31: First passivation layer

32: Second passivation layer

Claims (8)

A thin-film vertical resonant cavity surface-emitting laser element, including: an epitaxial structure, including: an upper Bragg reflector layer; a lower Bragg reflector layer; an active light-emitting layer, arranged on the upper Bragg reflector layer and below between the Bragg reflector layers; a current confinement layer, which is disposed on a surface of the lower Bragg reflector layer close to the active light-emitting layer and has a light-emitting hole; an N-type metal contact layer, which is away from the lower Bragg reflector layer. A surface of the active light-emitting layer forms ohmic contact; and a P-type metal contact layer forms ohmic contact with a surface of the upper Bragg reflector layer away from the active light-emitting layer; wherein, the P-type metal contact layer, the upper Bragg reflector layer The mirror layer, the active light-emitting layer, the current confinement layer, and the lower Bragg reflector layer form a cylinder on one side of the N-type metal contact layer. The thin-film vertical resonant cavity surface-emitting laser element according to claim 1, further comprising: a first metal electrode, disposed on a side of the N-type metal contact layer facing the cylinder, and connected with the N-type metal electrode The contact layer is electrically connected to a second metal electrode, which is disposed outside the cylinder and is electrically connected to the P-type metal contact layer. The thin-film vertical resonant cavity surface-emitting laser element as described in claim 2 further includes: A photosensitive polymer material is disposed in the gap between the first metal electrode and the second metal electrode. The thin-film vertical resonant cavity surface-emitting laser element according to claim 1, wherein the reflectivity of the upper Bragg reflector layer is greater than that of the lower Bragg reflector layer. The thin-film vertical resonant cavity surface-emitting laser element as described in claim 2 further includes: a first passivation layer covering the surface of the cylinder and the N-type metal contact layer that is not covered by the cylinder, and has a first opening and a second opening, the first opening partially exposes the surface of the N-type metal contact layer, and the second opening partially exposes the surface of the P-type metal contact layer; wherein, the first opening partially exposes the surface of the N-type metal contact layer; A metal electrode is electrically connected to the N-type metal contact layer through the first opening, and the second metal electrode is electrically connected to the P-type metal contact layer through the second opening. The thin-film vertical resonant cavity surface-emitting laser element according to claim 1 further includes: a second passivation layer disposed on a surface of the N-type metal contact layer away from the lower Bragg mirror layer. The thin-film vertical resonant cavity surface-emitting laser element according to any one of claims 1 to 6, wherein the number of mirror layer pairs of the upper Bragg reflector layer is greater than the number of mirror layer pairs of the lower Bragg reflector layer. . The thin-film vertical resonant cavity surface-emitting laser element according to any one of claims 1 to 6, wherein the active light-emitting layer further includes: a P-type space layer; an N-type space layer; and A multiple quantum well space layer is provided between the P-type space layer and the N-type space layer.

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