A method of passivating a cavity facet of a semiconductor laser

Abstract

The application relates to a method for passivating a cavity surface of a semiconductor laser, belonging to the field of passivating the cavity surface of a semiconductor laser. The method comprises the following steps: using a cleaving machine to cleave a sample P surface at a cleaving site to form a bar with a length of more than 3 cm; immersing the cleaved sample into a passivation liquid, placing the passivation liquid container in a constant-temperature shaking table, forming a sulfide passivation film on the sample cavity surface, then taking out the passivated sample, cleaning the sample with deionized water, and blowing dry the sample with nitrogen; the passivation liquid comprises hydrazine, ammonium sulfide and deionized water; placing the dried sample into a coating fixture, and placing the sample into a vacuum coating machine to evaporate a selenide passivation film on the front and rear cavity surfaces, then evaporating an antireflection film on the front cavity surface and a high-reflection film on the rear cavity surface. 2‑ The cavity oxide of the application can react with S 2‑ and Se 2‑ to remove the oxide, and the passivation liquid forms a sulfide passivation film on the cavity surface; Se forms a selenide passivation film on the cavity surface, so that the cavity surface is double-protected, and the surface state density is effectively reduced.

Description

Technical Field

[0001] This invention relates to a method for passivating the cavity surface of a semiconductor laser, belonging to the field of semiconductor laser cavity surface passivation technology. Background Technology

[0002] Semiconductor lasers, with their unique advantages such as high electro-optical conversion efficiency, small size, and wide emission wavelength, are widely used in industries such as industry, medicine, and the military, and their application areas are constantly expanding. Currently, most fields require semiconductor lasers to possess characteristics such as high power, high brightness, high conversion efficiency, and long lifetime. However, due to the high optical power density and large defect density at the cavity surface of semiconductor lasers, surface optical absorption and non-radiative recombination occur due to dislocations, leading to a continuous increase in the cavity surface temperature, bandgap contraction, and ultimately optical catastrophic damage (COD). Therefore, high-power, high-brightness semiconductor lasers may experience power degradation and failure during use.

[0003] Currently, methods such as plasma cleaning and high-vacuum cleavage are commonly used to address COD (Chemical Oxygen Deposition) issues. Plasma cleaning utilizes high-energy plasma to remove contaminants such as oxides and moisture from the cavity surface of semiconductor lasers, followed by the deposition of a passivation layer to reduce dangling bonds and other contaminants. The drawback of this method is that it is ineffective at low energies in removing surface contaminants, while high energies can damage the cavity surface, leading to decreased laser performance and failing to effectively remove contaminants from the semiconductor laser cavity surface. High-vacuum cleavage, on the other hand, involves cleaving the semiconductor laser chip in an ultra-high vacuum environment, followed by the deposition of a wide bandgap material. This effectively prevents oxygen and other impurities in the air from contaminating the semiconductor laser cavity surface. The disadvantage of this method is the high cost of the equipment, making it unsuitable for mass production and only suitable for laboratory research.

[0004] Chinese patent CN103022894A discloses "A cavity surface passivation film structure for a semiconductor laser and its preparation method." This method involves setting a cubic boron nitride (BN) cavity surface passivation film, placing a semiconductor laser chip with an exposed cavity surface inside the passivation cavity, and preparing the BN cavity surface passivation film by bombarding a target with Ar high-energy ions at temperatures above 800°C. The drawback of this method is that after cleaving and oscillating, the cavity surface of the semiconductor laser is placed inside the passivation cavity, resulting in a long exposure time to air. Extensive experiments have shown that an oxide layer forms on the cavity surface within a short time, increasing the surface state density. This increases the surface state density, acting as a scattering center and non-radiative recombination center for charge carriers, thus easily causing optical catastrophic damage (COD). Furthermore, the high energy of Ar ions can ablate the cavity surface, also leading to optical catastrophic damage. Therefore, this method cannot effectively remove the oxide layer; it only generates a protective layer on top of the oxide layer and cannot effectively improve the optical catastrophic phenomenon. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for passivating the cavity surface of a semiconductor laser, which can form sulfide and selenide passivation films on the cavity surface to achieve dual protection and effectively reduce the surface state density of the cavity surface.

[0006] The present invention adopts the following technical solution:

[0007] A method for passivating the cavity surface of a semiconductor laser includes the following steps:

[0008] (1) Use a cleaving dicing machine to cleave strips with a length of more than 3 cm at the cleaving position on the P side of the sample;

[0009] (2) Immerse the cleaved sample completely in the passivation solution, place the passivation solution container in a constant temperature shaker for a period of time to form a sulfide passivation film on the sample cavity surface, then use a dust-free clamp to take out the passivated sample, clean it with deionized water, and blow it dry with nitrogen.

[0010] The passivation solution includes hydrazine, ammonium sulfide, and deionized water. Hydrazine, also known as hydrazine, is an organic compound with the chemical formula N₂H₄. The ammonium sulfide in the passivation solution contains sulfur (S₂H₄). 2- HS - Plasma, hydrazine will react with HS - The reaction forms a higher concentration of S 2- This is beneficial for forming a thicker sulfide passivation film on the cavity surface of semiconductor lasers, thus extending the stability of the protective film.

[0011] (3) Use a dust-free clamp to load the dried sample into the coating fixture and place it in the vacuum coating machine. Evaporate a selenide passivation film on the front and rear cavity surfaces of the semiconductor laser, then evaporate an antireflection film on the front cavity surface and a high reflectivity film on the rear cavity surface.

[0012] Although sulfide passivation films protect the cavity surface, their stability is poor, providing only temporary protection. Over time, the semiconductor laser cavity surface will still be exposed to some extent. To better protect the cavity surface, Se powder is used as an evaporation source to deposit the Se powder onto the cavity surface. Under N plasma assistance, Se powder forms Se... 2- Se 2- with Ga 3+ And As 3+ Reaction (Ga 3+ As 3+ (It exists on the cavity surface in the form of Ga2O3 and As2O3) to form a selenide passivation film and prevent secondary oxidation of the cavity surface.

[0013] Preferably, in step (2), the temperature of the constant temperature shaker is 25°C, and the constant temperature shaker is preferably shaken for 100-200 minutes;

[0014] The constant temperature of the 25℃ constant temperature shaker helps to ensure the stability of the solution. The constant temperature shaker is placed on a horizontal anti-vibration table, and the shaker chamber rotates at a uniform speed, which helps to maintain the uniform concentration of the passivation solution. This ensures that the concentration and speed of the passivation solution are uniform during the passivation process, forming a uniform protective film.

[0015] Preferably, the mass ratio of hydrazine, ammonium sulfide and deionized water in the passivation solution is (1-2):(3-5):(5-10).

[0016] Preferably, in step (3), the initial vacuum degree is 6.0 × 10⁻⁶. 3 Pa, vapor deposition vacuum degree is 1.0×10 2 Pa, the electron gun operates at a voltage of 8kV and a current of 200-250mA.

[0017] Preferably, in step (3), the evaporation temperature is 200℃, nitrogen gas with a flow rate of 6-10 sccm is used as the plasma auxiliary gas, and Se powder with a purity of 99.999% is used as the evaporation source to deposit a selenide passivation film on the front and back cavity surfaces of the semiconductor laser. The evaporation time is 2-5 minutes.

[0018] Preferably, the thickness of the selenide passivation film is [missing information]. The reflectance of deposited antireflective coatings is 3%-10%, while that of high-reflection coatings is 95%.

[0019] Preferably, the cleavage length in step (1) is the cavity length of the semiconductor laser.

[0020] The cleaving and dicing machine used in this invention is model LOOMISLSD100, the constant temperature shaking incubator is model TS211C, and the vacuum coating machine is model EVA800.

[0021] For any details not covered in this invention, please refer to the prior art.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention employs sulfide and selenide passivation of the cavity surface. First, the surface is placed in a passivation solution for a certain period, ensuring that the semiconductor laser cavity surface is not exposed to air for extended periods, thus improving the cleanliness of the cavity surface and forming a sulfide passivation film. Then, nitrogen plasma-assisted deposition (NPD) is used to deposit Se powder, preventing damage to the cavity surface from high-energy ions and effectively removing contaminants to form a selenide passivation film. Finally, an antireflection film and a high-reflectivity film are deposited. This method of using selenide passivation to passivate the semiconductor cavity surface effectively protects it, preventing air contamination and significantly improving the lifespan of the semiconductor laser. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a passivation liquid container according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a sample with a sulfide passivation film and a selenide passivation film according to an embodiment of the present invention;

[0026] Among them, 1-constant temperature shaker, 2-passivation liquid container, 3-passivation liquid, 4-sample, 5-horizontal anti-vibration table, 6-sulfide passivation film, 7-selenide passivation film, 8-antireflection film, 9-high reflectivity film. Detailed implementation method:

[0027] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments. However, this description is not limited thereto. All aspects not described in detail in the present invention are based on conventional techniques in the field.

[0028] Example 1:

[0029] A method for passivating the cavity surface of a semiconductor laser includes the following steps:

[0030] (1) Use a cleaving dicing machine to cleave strips with a length of 4 cm at the cleaving position on the P side of the sample;

[0031] (2) Immerse the cleaved sample 4 completely in the passivation solution 3, place the passivation solution container 2 in the constant temperature shaker 1 for a period of time, and form a sulfide passivation film 6 on the cavity surface of the sample 4. Then, use a dust-free clamp to take out the passivated sample, clean it with deionized water, and blow it dry with nitrogen.

[0032] Passivation solution 3 includes hydrazine, ammonium sulfide, and deionized water. Hydrazine, also known as hydrazine, is an organic compound with the chemical formula N₂H₄. Ammonium sulfide in the passivation solution contains sulfur (S). 2- HS - Plasma, hydrazine will react with HS - The reaction forms a higher concentration of S 2- This is beneficial for forming a thicker sulfide passivation film on the cavity surface of semiconductor lasers, thus extending the stability of the protective film.

[0033] (3) Use a dust-free clamp to load the dried sample 4 into the coating fixture and place it in the vacuum coating machine. Evaporate a selenide passivation film 7 on the front and rear cavity surfaces of the semiconductor laser, then evaporate an antireflection film 8 on the front cavity surface and a high reflectivity film 9 on the rear cavity surface.

[0034] Although sulfide passivation films protect the cavity surface, their stability is poor, providing only temporary protection. Over time, the semiconductor laser cavity surface will still be exposed to some extent. To better protect the cavity surface, Se powder is used as an evaporation source to deposit the Se powder onto the cavity surface. Under N plasma assistance, Se powder forms Se...2- Se 2- with Ga 3+ And As 3+ Reaction (Ga 3+ As 3+ (It exists on the cavity surface in the form of Ga2O3 and As2O3) to form a selenide passivation film and prevent secondary oxidation of the cavity surface.

[0035] Example 2:

[0036] A method for passivating the cavity surface of a semiconductor laser, as described in Example 1, except that in step (2), the temperature of the constant temperature shaker 1 is 25°C and the shaking time of the constant temperature shaker 1 is 150 minutes;

[0037] The constant temperature of the 25℃ constant temperature shaker helps to ensure the stability of the solution. The constant temperature shaker is placed on a horizontal anti-vibration table, and the shaker chamber rotates at a uniform speed, which helps to maintain the uniform concentration of the passivation solution. This ensures that the concentration and speed of the passivation solution are uniform during the passivation process, forming a uniform protective film.

[0038] Example 3:

[0039] A method for passivating the cavity surface of a semiconductor laser, as described in Example 2, except that the mass ratio of hydrazine, ammonium sulfide and deionized water in the passivation solution is (1-2):(3-5):(5-10).

[0040] Example 4:

[0041] A method for passivating the cavity surface of a semiconductor laser, as described in Example 1, except that in step (3), the initial vacuum level is 6.0 × 10⁻⁶. 3 Pa, vapor deposition vacuum degree is 1.0×10 2 Pa, the electron gun operates at a voltage of 8kV and a current of 225mA.

[0042] The evaporation temperature was 200℃, nitrogen gas with a flow rate of 8ccm was used as the plasma-assisted gas, and Se powder with a purity of 99.999% was used as the evaporation source to deposit selenide passivation films on the front and back cavity surfaces of the semiconductor laser. The evaporation time was 3.5 minutes.

[0043] The thickness of the selenide passivation film is The reflectance of deposited antireflective coatings is 3%-10%, while that of high-reflection coatings is 95%.

[0044] Example 5:

[0045] A method for passivating the cavity surface of a semiconductor laser, as described in Example 1, except that the cleavage length in step (1) is the cavity length of the semiconductor laser.

[0046] Example 6:

[0047] A method for passivating the cavity surface of a semiconductor laser, as described in Example 1, except that a constant temperature shaker 1 rotates at a constant speed and is placed on a horizontal anti-vibration table 5.

[0048] Example 7:

[0049] A method for passivating the cavity surface of a semiconductor laser, as described in Example 1, except that the cleaving and dicing machine used is a LOOMISLSD100, the constant temperature shaking incubator is a TS211C, and the vacuum coating machine is an EVA800.

[0050] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for passivating the cavity surface of a semiconductor laser, characterized in that, Includes the following steps: (1) Use a cleaving dicing machine to cleave strips with a length of 3 cm or more at the cleaving position on the P side of the sample; (2) Immerse the cleaved sample completely in the passivation solution, place the passivation solution container in a constant temperature shaker for a period of time to form a sulfide passivation film on the sample cavity surface, and then use a dust-free clamp to take out the passivated sample, clean it with deionized water, and blow it dry with nitrogen. The passivation solution includes hydrazine, ammonium sulfide and deionized water; the mass ratio of hydrazine, ammonium sulfide and deionized water in the passivation solution is (1-2):(3-5):(5-10); (3) Use a dust-free clamp to load the dried sample into the coating fixture and place it in the vacuum coating machine. Evaporate a selenide passivation film on the front and rear cavity surfaces of the semiconductor laser, then evaporate an antireflection film on the front cavity surface and a high reflectivity film on the rear cavity surface. In step (2), the temperature of the constant temperature shaker is 25°C, and the constant temperature shaker is preferably shaken for 100-200 minutes; In step (3), the initial vacuum degree is 6.0 × 10⁻⁶. 3 Pa, vapor deposition vacuum degree is 1.0×10 2 Pa, the electron gun operates at a voltage of 8kV and a current of 200-250mA; In step (3), the evaporation temperature is 200℃, nitrogen gas with a flow rate of 6-10 sccm is used as the plasma auxiliary gas, and Se powder with a purity of 99.999% is used as the evaporation source to deposit selenide passivation film on the front and back cavity surfaces of the semiconductor laser. The evaporation time is 2-5 minutes. The thickness of the selenide passivation film is 30-70 Å, the reflectance of the deposited antireflection film is 3%-10%, and the reflectance of the high reflectance film is 95%.

2. The method for passivating the cavity surface of a semiconductor laser according to claim 1, characterized in that, In step (1), the cleavage length is the cavity length of the semiconductor laser.

3. The method for passivating the cavity surface of a semiconductor laser according to claim 1, characterized in that, In step (2), the constant temperature shaker rotates at a constant speed and is placed on a horizontal anti-vibration table.

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