Preparation process and structure of high-reliability low-noise vertical laser

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a preparation process and structure of a high-reliability low-noise vertical laser, and the preparation process comprises the steps: selecting a substrate with the lattice direction of [1 0] 2-15 degrees offset [1 0]; two arc-shaped grooves are etched in the layer structure of the substrate, an opening is formed between the ends of the two arc-shaped grooves, and the direction of the opening is in the crystal orientation [0 < 0 > 1]; the oxidation limiting layer is oxidized, and a quasi-circular oxidation hole is formed between the two arc-shaped grooves; covering the opening and the surface of the device with a passivation protection film; filling the opening, connecting the metal circular ring through the opening position, and leading a P-pole current injection point to the peripheral area; and etching the surface passivation layer at the top of the light-emitting region to form an elliptical embossment with the ratio of the short axis to the long axis being 1: 1-1: 2. The opening is designed to face the [0 < 0 > 1] lattice direction, the final oxidation shape of the device is similar to a circle, and the reliability is improved. Elliptical embossments are etched on the surface passivation film, the relative intensity noise is reduced, and the transmission quality is effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor lasers, and in particular to a preparation process and structure of a high-reliability, low-noise vertical laser. Background Art

[0002] High-speed vertical-cavity surface-emitting lasers (VCSELs) play a vital role in the development of large data centers and supercomputers due to their compact size, low power consumption, low cost, and high speed. The increasing data throughput demands higher-speed, lower-noise VCSELs in data centers and supercomputer systems.

[0003] Oxide-confined VCSELs (VCSELs) are used in mass production due to their low cost, low power consumption, and low threshold. The main process steps for producing oxide holes in existing VCSELs include wafer epitaxial growth, during which trenches are etched into the epitaxially grown layer structure to form a columnar (usually cylindrical) active area terrace. The oxide confinement layer must be exposed to the sidewalls of the active area terrace. Etched trenches typically come in two forms: closed trenches and open trenches, both of which are common in current VCSEL etching processes.

[0004] The sidewalls of the active area platform are oxidized laterally along the oxidation restriction layer, and the unoxidized area in the middle forms an oxidation hole, which is the light output hole and current injection area of ​​the VCSEL; then the surface is passivated.

[0005] The oxide aperture shape of conventional oxide-confined VCSELs is designed to be as close to circular as possible to ensure uniform current injection and reduce device failure due to oxide layer cracking. However, this near-circular oxide aperture results in unselective competition between the two orthogonal polarization states in the transverse mode, exacerbating relative intensity noise and significantly impacting high-speed transmission performance. Summary of the Invention

[0006] In order to reduce noise and improve transmission performance, the present application provides a preparation process and structure of a high-reliability, low-noise vertical laser.

[0007] One of the objectives of this application is to provide a process for preparing a high-reliability, low-noise vertical laser, using the following technical solution: A process for preparing a high-reliability, low-noise vertical laser, comprising: S1, select a substrate with a lattice direction of [1 0 0] 2-15° offset from [1 1 0]; S2. Etching two opposite arc-shaped grooves on the layer structure of the substrate, forming an opening between the ends of the two arc-shaped grooves, and the direction of the opening is along the crystal direction [0 0 1]; S3, oxidizing the oxidation restriction layer in the layer structure, forming a circular oxidation hole between the two arc-shaped grooves; S4, covering the opening and the surface of the device with a passivation protective film to form a surface passivation layer; S5, filling the opening to form a dielectric filling layer, and connecting a metal ring through the opening position to guide the P-pole current injection point to the peripheral area to form a P-side ohmic contact layer; S6. Etching the surface passivation layer on the top of the light-emitting area into an elliptical relief with a short-to-long axis ratio of 1:1-1:2 to form a polarization control layer.

[0008] By adopting the above technical solutions, in order to ensure structural stability and prevent the coating stress from causing the oxide layer to crack, which affects reliability, non-closed trenches are mostly used. The non-closed trench structure results in a non-circular oxidation aperture, which leads to uneven current injection and excessive local current density, resulting in device failure. Conventionally, the non-closed trench structure is made into a quasi-circular oxidation aperture, and a barrier layer needs to be set in part of the trench sidewall area to actively correct the difference in oxidation rate in each direction. This process is extremely complex and unstable.

[0009] While retaining the non-closed grooves, the present invention orients the arc-shaped groove openings in the [0 0 1] lattice direction. The resulting oxidized device shape is quasi-circular, significantly improving reliability compared to non-circular oxidized shapes. Furthermore, an elliptical relief pattern with a short-to-long axis ratio of 1:1-1:2 is etched into the surface passivation film. This modulates the polarization characteristics of the emitted light, reduces relative intensity noise, and effectively improves transmission quality.

[0010] Preferably, the relief in step S6 is etched along the crystal direction [0 1 1] [0 -1 1].

[0011] Preferably, the method further includes step S7, using an evaporation process to form a metal ring on the top of the light-emitting area of ​​the device as a current injection area.

[0012] Preferably, the distances between the two openings in S2 are different.

[0013] Preferably, in S5 , the opening is filled with styrene as a filling medium through an electroplating process.

[0014] By adopting the above technical solution, external parasitic capacitance is reduced.

[0015] Preferably, the material of the surface passivation layer in S4 is SiNx.

[0016] By adopting the above technical solution, the stress of SiNx is lowered, and the internal stress is reduced.

[0017] Another object of the present application is to provide a high-reliability, low-noise vertical laser structure, which adopts the following technical solutions: A high-reliability, low-noise vertical laser structure is manufactured by the above-mentioned high-reliability, low-noise vertical laser preparation process, including a substrate, a layer structure is provided on the substrate, the layer structure includes a light-emitting area, a circular oxide hole is provided in the center of the light-emitting area, the layer structure includes a surface passivation layer located on the top, and an elliptical surface relief is etched on the surface passivation layer located in the light-emitting area.

[0018] By adopting the above technical solution, high-reliability quasi-circular oxidation aperture technology can be taken into account while polarization state control can be achieved, and high-reliability, low-noise vertical cavity surface emitting laser manufacturing can be achieved at extremely low cost and price.

[0019] Preferably, the layer structure includes an N-side DBR layer, an N-type restriction layer, an active area, a P-type restriction layer, an oxidation restriction layer, a P-type DBR layer, an ion implantation layer, a dielectric filling layer and a surface passivation layer, which are arranged in sequence from bottom to top. An N-side electrode is also provided on the substrate. The ion implantation layer is located on the outside of the P-type DBR layer in the light-emitting area, and a P-side ohmic contact layer is provided on the top of the light-emitting area.

[0020] By adopting the above technical solution, the effective thickness of the non-conductive area on the oxide layer is increased, the parasitic capacitance of the device is reduced, and the high-speed characteristics of the device are improved.

[0021] In summary, this application has the following beneficial technical effects: The high-reliability quasi-circular oxide aperture technology can achieve polarization state control at the same time, and can realize high-reliability and low-noise vertical cavity surface emitting laser manufacturing at extremely low cost and price. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a cross-sectional view of the laser in Example 1; Figure 2 FIG. 4 is a top view of the laser in Example 1. FIG.

[0023] Description of reference numerals: 1. Substrate; 2. N-side electrode; 3. N-type DBR layer; 4. N-type confinement layer; 5. Active area; 6. P-type confinement layer; 7. Oxide confinement layer; 8. P-type DBR layer; 9. Ion implantation layer; 10. Dielectric filling layer; 11. Surface passivation layer; 12. P-side ohmic contact layer; 13. Polarization control layer; 14. Arc groove; 15. Opening; 16. Oxide hole. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with all the accompanying drawings.

[0025] Example 1: This application discloses a method for preparing a high-reliability, low-noise vertical laser. Figure 1 and Figure 2 , including the following steps: S1, selecting a substrate 1 with a lattice direction of [1 0 0] 2-15° offset from [1 1 0]; wherein the material of the substrate 1 is GaAs; S2. Etching two opposing arc-shaped grooves 14 on the layer structure of the substrate 1 by a dry etching process. An opening 15 is formed between the ends of the two arc-shaped grooves 14, and the direction of the opening 15 is along the crystal direction [0 0 1]. The two openings 15 are different in size, that is, the width of one opening 15 is larger than the width of the other opening 15; S3. Through a wet oxidation process, the oxidation restriction layer 7 in the layer structure is oxidized, and the high Al layer exposed in the arc-shaped groove 14 reacts, so that a circular oxidation hole 16 is formed between the two arc-shaped grooves 14; the opening 15 is along the crystal direction

[001] . Since the chemical bond properties of the crystal directions

[001] and [0-10] are consistent, a circular oxidation hole 16 can be stably obtained; S4, through a dielectric thin film deposition process, a low-stress SiNx passivation protective film is formed on the opening 15 of the arc-shaped trench 14 and the surface of the device to form a surface passivation layer 11; S5. Fill the opening 15 with styrene-cyclobutene material through an electroplating process to form a dielectric filling layer 10 to improve heat dissipation capability. At the same time, connect a metal ring through the opening 15 to guide the P-pole current injection point to the peripheral area. S6. Etching the passivation film on the top of the light-emitting area along the crystal direction [0 1 1] [0 -1 1] to form an elliptical relief with a short-to-long axis ratio of 1:1-1:2 to form a polarization control layer 13 by a dry etching process; S7. Using an evaporation process, a metal ring is formed on the top of the light-emitting region of the device as a current injection region. S8, through the dry etching process, leak out the N-side electrode 2, and use the evaporation process to form the N-pole current injection area. The above steps S1-S8 only represent the content and number of steps, and do not represent the order of the steps.

[0026] The arc-shaped groove 14 and its opening 15 are designed to face the [0 0 1] lattice direction, resulting in a circular shape for the oxidation hole 16. This effectively improves reliability compared to non-circular oxidation shapes. Using a SiNx dry etching process, the surface passivation film is etched into an elliptical relief pattern with a short-to-long axis ratio of 1:1-1:2. This modulates the polarization characteristics of the emitted light, reduces relative intensity noise, and effectively improves transmission quality.

[0027] Example 2: This application discloses a structure of a high-reliability, low-noise vertical laser, which is prepared by the above-mentioned embodiment. Figure 1 and Figure 2The invention comprises a substrate 1 made of GaAs, wherein the lattice direction of the commercial substrate 1 is [1 0 0] 2-15° deviated from [1 1 0]. A layer structure is provided on the substrate 1, and the layer structure includes a light-emitting area, and a circular oxide hole 16 is provided in the center of the light-emitting area.

[0028] An N-side electrode 2 is provided on the substrate 1 and is made of Au, Ge, Ni or Au.

[0029] The layer structure includes the following arranged from bottom to top: N-type DBR layer 3, made of GaAs or AlAs, using AlAs as a heat dissipation layer to improve reliability; N-type confinement layer 4, made of AlGaAs Active area 5, material is InGaAs or AlGaAs strained quantum well structure P-type confinement layer 6, made of AlGaAs P-type DBR layer 8, made of GaAs or AlGaAs Oxidation restriction layer 7, made of AlGaAs; The ion implantation layer 9 is located outside the P-type DBR layer 8 in the light emitting area and does not exceed the active area 5. It increases the effective thickness of the non-conductive area on the oxide layer, reduces the parasitic capacitance of the device, and improves the high-speed characteristics of the device. The dielectric filling layer 10 is made of styrene-propylcyclobutene to reduce external parasitic capacitance; The surface passivation layer 11, made of SiNx, provides passivation and protection. An elliptical relief with a short-to-long axis ratio of 1:1-1:2 is etched along the [0 1 1] [0 -1 1] direction on the surface passivation layer 11 located outside the light-emitting area, forming the polarization control layer 13. A P-face ohmic contact layer 12 is provided on top of the light-emitting area.

[0030] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A process for preparing a high-reliability, low-noise vertical laser, characterized in that: include, S1, select a substrate (1) with a lattice direction of [1 0 0] 2-15° offset from [1 1 0]; S2, etching two opposite arc-shaped grooves (14) on the layer structure of the substrate (1), forming an opening (15) between the ends of the two arc-shaped grooves (14), and the direction of the opening (15) is along the crystal direction [0 0 1]; S3, oxidizing the oxidation restriction layer (7) in the layer structure, so that a circular oxidation hole (16) is formed between the two arc-shaped grooves (14); S4, covering the opening and the device surface with a passivation protective film to form a surface passivation layer (11); S5, filling the opening (15) to form a dielectric filling layer (10), and at the same time connecting a metal ring through the position of the opening (15) to lead the P-pole current injection point to the peripheral area to form a P-side ohmic contact layer (12); S6, etching the surface passivation layer (11) on the top of the light-emitting area to form an elliptical relief with a short-to-long axis ratio of 1:1-1:2 to form a polarization control layer (13).

2. The process for preparing a high-reliability, low-noise vertical laser according to claim 1, characterized in that: The relief in step S6 is etched along the crystal direction [0 1 1] [0 -1 1].

3. The process for preparing a high-reliability, low-noise vertical laser according to claim 1, characterized in that: The method also includes step S7, using an evaporation process to form a metal ring on the top of the light-emitting area of ​​the device as a current injection area.

4. The process for preparing a high-reliability, low-noise vertical laser according to claim 1, characterized in that: The distances between the two openings (15) in S2 are different.

5. The process for preparing a high-reliability, low-noise vertical laser according to claim 1, characterized in that: In S5, the opening (15) is filled by electroplating process using phenylcyclobutene as a filling medium.

6. The process for preparing a high-reliability, low-noise vertical laser according to claim 1, characterized in that: The material of the surface passivation layer (11) in S4 is SiNx.

7. A structure of a high reliability and low noise vertical laser, characterized in that: A high-reliability, low-noise vertical laser is manufactured by a preparation process according to any one of claims 1 to 6, comprising a substrate (1), a layer structure being provided on the substrate (1), the layer structure comprising a light-emitting area, a circular-shaped oxidation hole (16) being provided at the center of the light-emitting area, the layer structure comprising a surface passivation layer (11) located on the top, an elliptical surface relief being etched on the surface passivation layer (11) located in the light-emitting area.

8. The structure of a high reliability and low noise vertical laser according to claim 7, characterized in that: The layer structure comprises, arranged in order from bottom to top, an N-side DBR layer (3), an N-type restriction layer (4), an active region (5), a P-type restriction layer (6), an oxidation restriction layer (7), a P-type DBR layer (8), an ion implantation layer (9), a dielectric filling layer (10) and a surface passivation layer (11); an N-side electrode (2) is also provided on the substrate (1); the ion implantation layer (9) is located outside the P-type DBR layer (8) in the light-emitting region; and a P-side ohmic contact layer (12) is provided on the top of the light-emitting region.

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