A high-speed direct modulation AlInGaAs laser BH current blocking layer structure and a preparation method thereof

Abstract

The application discloses a high-speed direct modulation AlInGaAs laser BH current blocking layer structure, which is a plurality of doping concentration layers which are epitaxially grown on both sides of a BH mesa with SiO2 as a mask strip, and the doping concentration layers comprise an InP thin layer isolation layer, a P-InP medium doping concentration layer, a P-InP low doping concentration layer, an N-InP low doping concentration layer, an N-InP high doping concentration layer and a P-InP surface cover layer; and the doping concentration layers on both sides of the BH mesa are sequentially the P-InP surface cover layer, the N-InP high doping concentration layer, the N-InP low doping concentration layer, the P-InP low doping concentration layer, the P-InP medium doping concentration layer and the InP thin layer isolation layer from top to bottom. The current blocking layer structure and method of the application reduce the accumulation of high carrier charges of the current blocking layer of the BH structure, avoid the formation of a large current blocking layer parasitic capacitance effect, and improve the application effect of the BH structure in an AlInGaAs / InP multi-quantum well high-speed modulation laser.

Description

Technical Field

[0001] This invention belongs to the field of information optoelectronics technology, specifically relating to a BH current blocking layer structure and preparation method for a high-speed direct-modulation AlInGaAs laser. Background Technology

[0002] Since its emergence, fiber optic communication technology has brought about significant changes in the fields of science and technology and society. As an important application of laser technology, laser information technology, with fiber optic communication technology as its main representative, has built the framework of modern communication networks and become an important component of information transmission; moreover, its data transmission rate is rapidly increasing, and laser chips with transmission rates of over 25Gbps are becoming the core chips of the next-generation 5G optical communication network.

[0003] In traditional communication-band laser fabrication, the active region of the InGaAsP / InP multi-quantum-well semiconductor material is commonly used to fabricate BH-DFB laser structures, leveraging its low threshold current, high linear optical output power, and good fiber coupling efficiency. However, the InGaAsP / InP multi-quantum-well material suffers from weak electron confinement due to its band structure. Consequently, the output optical power decays rapidly with increasing temperature. Furthermore, the excessively strong quantum barrier imposed by the band structure on holes with large effective band mass hinders timely and uniform hole movement during high-speed modulation, thus affecting the high-speed modulated laser signal output and failing to meet the requirements for fabricating high-speed modulated lasers with a wide temperature range and speeds exceeding 10 Gbps.

[0004] Another type of III-V semiconductor material, AlInGaAs / InP multiple quantum wells, has gradually replaced InGaAsP / InP multiple quantum wells as the active region material for fabricating high-speed modulated semiconductor lasers with a wide temperature range due to its stronger electron confinement and correspondingly lower quantum barrier for holes compared to InGaAsP / InP multiple quantum wells. However, when using AlInGaAs / InP multiple quantum well materials in the active region of lasers, the oxidation of Al makes MOCVD secondary epitaxial growth of BH structures very difficult. The high carrier charge accumulation in the current blocking layer leads to a large parasitic capacitance effect, which limits the application of the BH structure in high-speed modulation lasers with multiple quantum wells in AlInGaAs / InP. Currently, DFB lasers with active regions of AlInGaAs / InP multiple quantum well structures generally adopt the ridge waveguide (RW) structure. However, the heat dissipation performance of the RW laser structure on both sides of the waveguide is worse than that of the BH laser structure, and it cannot meet the application requirements of high-speed modulation DFB lasers with a wide temperature range, such as industrial temperature-level lasers in the fronthaul of 5G optical communication networks, which require an operating temperature range of -40℃ to 95℃. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a BH current blocking layer structure and fabrication method for a high-speed direct-modulation AlInGaAs laser. The current blocking layer structure and method of this invention reduce the accumulation of high carrier charge in the current blocking layer of the BH structure by epitaxially growing a current blocking layer structure with a specific doping concentration distribution on both sides of the BH mesa, avoids the formation of a large parasitic capacitance effect in the current blocking layer, and improves the application effect of the BH structure in high-speed modulation lasers with AlInGaAs / InP multiple quantum wells.

[0006] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0007] A high-speed direct-modulation AlInGaAs laser BH current blocking layer structure is disclosed. The current blocking layer structure is disposed on both sides of the BH mesa. The structure consists of multiple doped concentration layers epitaxially grown on both sides of the BH mesa using SiO2 as a mask. The doped concentration layers include a thin InP isolation layer, a medium doped concentration P-InP layer, a low doped concentration P-InP layer, a low doped concentration N-InP layer, a high doped concentration N-InP layer, and a surface capping layer of P-InP. The doped concentration layers on both sides of the BH mesa, from top to bottom, are the surface capping layer of P-InP, the high doped concentration N-InP layer, the low doped concentration N-InP layer, the low doped concentration P-InP layer, the medium doped concentration P-InP layer, and the thin InP isolation layer.

[0008] No dopant flow rate is set in the above-mentioned InP thin-layer isolation layer, and the thickness of the InP thin-layer isolation layer does not exceed 150 nm.

[0009] The doping concentration range of the aforementioned P-InP medium doping concentration layer is 5E17cm. -3 -7E17cm -3 The thickness of the medium doping concentration layer of P-InP is 20%-30% of the depth of the BH mesa.

[0010] The doping concentration of the low-doped P-InP layer mentioned above is no higher than 3E17cm. -3 The thickness of the low-doping concentration layer of P-InP is not less than 20% of the depth of the BH mesa.

[0011] The doping concentration of the aforementioned low-doped N-InP layer is no higher than 3E17cm. -3 The thickness of the low-doping concentration N-InP layer is not less than 20% of the depth of the BH mesa.

[0012] The doping concentration of the aforementioned high-doped N-InP layer is not less than 2E18cm. -3 The thickness of the high doping concentration N-InP layer is 20%-30% of the depth of the BH mesa.

[0013] The doping concentration of the P-InP surface coating is not less than 8E17cm. -3 The thickness of the high doping concentration layer of P-InP does not exceed 5% of the depth of the BH mesa.

[0014] A method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser, the method specifically includes the following steps:

[0015] The first step is to deposit a SiO2 dielectric layer on the wafer surface of the AlInGaAs laser, and then perform photolithography on the SiO2 dielectric layer to form multiple parallel photolithographic mask strips. Finally, the SiO2 strip film is etched out by ICP-RIE dry etching.

[0016] The second step is to use an etching solution to etch the SiO2 strip film to form BH mesa, and then clean the surface of the BH mesa.

[0017] The third step is to place the cleaned BH mesa on the wafer surface into the MOCVD epitaxial growth chamber, and grow current blocking layer structures on both sides of the BH mesa in the MOCVD epitaxial growth chamber by metal-organic chemical vapor deposition (MOCVD).

[0018] The fourth step, after the current barrier layer structure has been grown, is to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box using the mechanical transfer device of the MOCVD system, thus completing the fabrication of the current barrier layer structure.

[0019] The wafer structure of the AlInGaAs laser in the first step above includes an N-InP wafer substrate and an N-InP buffer layer, an AlInGaAs multi-quantum-well active region, a P-InP grating isolation layer, a P-InGaAs P grating layer, a P-InP isolation layer, and a P-InGaAs surface layer. The N-InP wafer substrate is sequentially grown with the N-InP buffer layer, the AlInGaAs multi-quantum-well active region, the P-InP grating isolation layer, the P-InGaAs P grating layer, the P-InP isolation layer, and the P-InGaAs surface layer.

[0020] In the first step described above, the SiO2 dielectric layer is deposited on the P-InGaAs surface layer using the PECVD method. The thickness of the SiO2 dielectric layer is 200 nm. The photolithography mask strips are perpendicular to the grating strips inside the wafer. The width of the photolithography mask strips ranges from 4.3 to 4.5 μm. The spacing between the photolithography mask strips is 250 μm. The width of the SiO2 strip film is 4.0 to 4.2 μm.

[0021] After the SiO2 strip film etching is completed, the wafer surface is cleaned with photoresist solvent, and then an oxygen ion cleaner is used to remove the residual photoresist on the wafer surface.

[0022] The etching solution in the second step above is a mixture of hydrobromic acid, hydrogen peroxide and water. The depth of the BH mesa is 2.0-3.0 μm. During etching, the BH mesa passes through the AlInGaAs multi-quantum-well active region and enters the N-InP wafer substrate region.

[0023] The specific steps for cleaning the surface of the BH countertop are as follows:

[0024] S21, the wafer with the etched BH mesa is immersed in acetone and isopropanol organic solvents in sequence, and the immersion time of the wafer in acetone and isopropanol organic solvents is 3 minutes each.

[0025] S22, After the wafer is soaked in organic solvent, it is cleaned with deionized water for no less than 5 minutes, and then the water on the surface of the wafer is dried with a pure N2 gun.

[0026] S23, immerse the wafer in concentrated sulfuric acid solution for 5 minutes, then remove the wafer from the concentrated sulfuric acid solution and clean it with deionized water for no less than 5 minutes. Use a pure N2 gun to blow dry the remaining water on the surface of the wafer.

[0027] S24, the cleaned wafer is transferred into the wafer glove box and the pressure is evacuated to a low level. Then, the wafer is transferred from the wafer glove box into the MOCVD epitaxial growth chamber through the mechanical transfer device of the MOCVD system for subsequent epitaxial growth.

[0028] The specific steps for epitaxial growth of the current blocking layer structure on both sides of the wafer BH mesa in the third step above are as follows:

[0029] S31, the wafer transferred into the MOCVD epitaxial growth chamber is evacuated to a low pressure and maintained at a low pressure, and H2 is introduced into the MOCVD epitaxial growth chamber as the carrier gas for epitaxial growth, and then the MOCVD epitaxial growth chamber is heated.

[0030] S32, when the temperature of the MOCVD epitaxial growth chamber reaches 200℃, 500 sccm of PH3 gas is introduced into the MOCVD epitaxial growth chamber.

[0031] S33, when the temperature of the MOCVD epitaxial growth chamber reaches 400℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 400℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again.

[0032] S34, when the temperature of the MOCVD epitaxial growth chamber reaches 500℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 500℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again.

[0033] S35, when the temperature of the MOCVD epitaxial growth chamber reaches 620℃, after the temperature of the MOCVD epitaxial growth chamber is kept constant at 620℃ for 30 minutes, saturated TMI gas is introduced into the MOCVD epitaxial growth chamber at this temperature to epitaxially grow an InP thin isolation layer at the bottom of the BH mesa of the wafer. The growth rate of the InP thin isolation layer is 0.3nm / sec.

[0034] S36, After the InP thin isolation layer epitaxial growth is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and introduce DEZn saturated gas into the MOCVD epitaxial growth chamber to epitaxially grow a medium-doped P-InP layer at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 5E17cm⁻¹. -3 The growth rate of the P-InP medium doping concentration layer is 0.3 nm / sec;

[0035] S37, after the epitaxial growth of the medium-doped P-InP layer is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, adjust the flow rate of the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber, and epitaxially grow a low-doped P-InP layer at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 2E17cm⁻¹. -3 The growth rate of the low-doped P-InP layer was 0.3 nm / sec;

[0036] S38, after the epitaxial growth of the low-doped P-InP layer is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and switch the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber to Si2H6 gas. Epitaxially grow a low-doped N-InP layer at the bottom of the BH mesa of the wafer, so that the N-type doping concentration of N-InP is 2E17cm⁻¹. -3 The growth rate of the low-doped N-InP layer was 0.3 nm / sec;

[0037] S39, after the low-doped N-InP layer is epitaxially grown, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, adjust the Si2H6 gas flow rate introduced into the MOCVD epitaxial growth chamber, and epitaxially grow a high-doped N-InP layer at the bottom of the BH mesa of the wafer, so that the N-type doping concentration of N-InP is 3E18cm⁻¹. -3 The growth rate of the N-InP high-doped-concentration layer was 0.3 nm / sec;

[0038] S40, after the high-doped N-InP layer is epitaxially grown, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and switch the Si2H6 gas introduced into the MOCVD epitaxial growth chamber to DEZn saturated gas. Epitaxially grow a P-InP surface capping layer on the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 7E17cm⁻¹. -3 The growth rate of the P-InP surface capping layer is 0.3 nm / sec;

[0039] S41, After the epitaxial growth of the P-InP surface capping layer is completed, shut off other gases to the MOCVD epitaxial growth chamber, retain the PH3 and H2 gases introduced into the MOCVD epitaxial growth chamber, and cool the MOCVD epitaxial growth chamber; when the temperature of the MOCVD epitaxial growth chamber drops to 200℃, shut off the PH3 gas introduced into the MOCVD epitaxial growth chamber.

[0040] S42, when the temperature of the MOCVD epitaxial growth chamber drops to 50°C, the mechanical transfer device of the MOCVD system is used to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box, and then the wafer is transferred out from the wafer glove box to complete the epitaxial growth of the current barrier layer structure on both sides of the BH mesa of the wafer.

[0041] A high-speed direct-modulated AlInGaAs laser, which includes the aforementioned BH current blocking layer structure.

[0042] Based on the above technical solutions, the present invention patent's BH current blocking layer structure and preparation method for a high-speed direct-modulated AlInGaAs laser has achieved the following technical advantages through practical application:

[0043] 1. The present invention discloses a BH current blocking layer structure for a high-speed direct-modulated AlInGaAs laser. By epitaxially growing a current blocking layer structure with a specific doping concentration distribution on both sides of the BH mesa, the accumulation of high carrier charge in the current blocking layer of the BH structure is reduced, the formation of a large parasitic capacitance effect of the current blocking layer is avoided, and the application effect of the BH structure in high-speed modulated lasers with multiple quantum wells of AlInGaAs / InP is improved.

[0044] 2. The present invention discloses a method for fabricating a high-speed direct-modulation AlInGaAs laser BH current blocking layer structure. This method involves first cleaning the surface of an Al-containing wafer with an organic solvent to remove trace amounts of organic residue. Then, the wafer is immersed in a concentrated sulfuric acid solution, which removes the oxidized Al layer and simultaneously passivates it, reducing the chemical reactivity of the Al layer molecules on the wafer surface and inhibiting the reaction between the Al layer and oxygen in the air. This improves the quality and efficiency of subsequent epitaxial growth of the BH structure. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the current blocking layers formed on both sides of the BH mesa in a high-speed direct-modulation AlInGaAs laser BH current blocking layer structure according to the present invention.

[0046] Figure 2 This is a schematic diagram of the SiO2 strip film etched on the wafer surface in the BH current blocking layer structure of a high-speed direct modulated AlInGaAs laser according to the present invention.

[0047] Figure 3 This is a diagram of the BH mesa structure formed by etching a SiO2 strip film in the BH current blocking layer structure of a high-speed direct-modulated AlInGaAs laser according to the present invention.

[0048] Figure 4This is a cross-sectional SEM image of the BH current blocking layer structure of a high-speed direct-modulated AlInGaAs laser according to the present invention.

[0049] The specific explanations of the reference numerals in the attached figures are as follows:

[0050] 1. Undoped InP thin layer; 2. P-InP medium doping concentration layer; 3. P-InP low doping concentration layer; 4. N-InP low doping concentration layer; 5. N-InP high doping concentration layer; 6. P-InP surface capping layer; 7. N-InP substrate and N-InP buffer layer; 8. AlInGaAs multi-quantum-well active region; 9. P-InP grating isolation layer; 10. P-InGaAs grating layer; 11. P-InP isolation layer; 12. P-InGaAs surface layer; 13. SiO2 etched film layer; 14. Grating strip; 15. SiO2 strip film; 16. Main alignment notch; 17. Sub-alignment notch. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0052] like Figure 1 As shown, this invention pertains to a high-speed direct-modulation AlInGaAs laser BH current blocking layer structure. The current blocking layer structure is disposed on both sides of the BH mesa. This structure consists of multiple doped concentration layers epitaxially grown on both sides of the strip-shaped BH mesa using SiO2 as a mask. The doped concentration layers include an InP thin isolation layer 1, a P-InP medium doped concentration layer 2, a P-InP low doped concentration layer 3, an N-InP low doped concentration layer 4, an N-InP high doped concentration layer 5, and a P-InP surface capping layer 6. The doped concentration layers on both sides of the BH mesa are arranged from top to bottom in the following order: The structure consists of a P-InP surface capping layer 6, a high-doped N-InP layer 5, a low-doped N-InP layer 4, a low-doped P-InP layer 3, a medium-doped P-InP layer 2, and an InP thin-film isolation layer 1. By epitaxially growing a current-blocking layer structure with a specific doping concentration distribution on both sides of the BH mesa, the accumulation of high carrier charge in the current-blocking layer of the BH structure is reduced, avoiding the formation of a large parasitic capacitance effect in the current-blocking layer, thus improving the application effect of the BH structure in high-speed modulated lasers with AlInGaAs / InP multiple quantum wells.

[0053] In this process, no dopant flow rate is set in the InP thin-layer isolation layer 1, and the thickness of the InP thin-layer isolation layer 1 does not exceed 150 nm.

[0054] The doping concentration range of the intermediate doping concentration layer 2 of P-InP is 5E17cm. -3 -7E17cm -3 The thickness of the medium doping concentration layer 2 of P-InP is 20%-30% of the depth of the BH mesa.

[0055] The doping concentration of the low-doped P-InP layer 3 is no higher than 3E17cm. -3 The thickness of the low doping concentration layer 3 of P-InP is not less than 20% of the depth of the BH mesa.

[0056] The doping concentration of N-InP low-doping layer 4 is no higher than 3E17cm. -3 The thickness of the low-doping-concentration N-InP layer 4 is not less than 20% of the depth of the BH mesa.

[0057] The doping concentration of the high-doped N-InP layer 5 is not less than 2E18cm. -3 The thickness of the high-doped N-InP layer 5 is 20%-30% of the depth of the BH mesa.

[0058] The doping concentration of the P-InP surface coating 6 is not less than 8E17cm. -3 The thickness of the high doping concentration N-InP layer 5 does not exceed 5% of the depth of the BH mesa.

[0059] like Figure 1-3 As shown, a method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser is disclosed, which specifically includes the following steps:

[0060] The first step is to deposit a SiO2 dielectric layer 13 on the wafer surface of the AlInGaAs laser, and then perform photolithography on the SiO2 dielectric layer 13 to form multiple parallel photolithographic mask strips. Finally, the SiO2 strip film 15 is etched out by ICP-RIE dry etching on the photolithographic mask strips.

[0061] The second step is to use an etching solution to etch the SiO2 strip film 15 to form a BH platform, and then clean the surface of the BH platform.

[0062] The third step is to place the cleaned BH mesa on the wafer surface into the MOCVD epitaxial growth chamber, and grow current blocking layer structures on both sides of the BH mesa in the MOCVD epitaxial growth chamber by metal-organic chemical vapor deposition (MOCVD).

[0063] The fourth step, after the current barrier layer structure has been grown, is to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box using the mechanical transfer device of the MOCVD system, thus completing the fabrication of the current barrier layer structure.

[0064] The wafer structure of the AlInGaAs laser in the first step includes an N-InP wafer substrate and an N-InP buffer layer 7, an AlInGaAs multi-quantum-well active region 8, a P-InP grating isolation layer 9, a P-InGaAs P grating layer 10, a P-InP isolation layer 11, and a P-InGaAs surface layer 12. The N-InP wafer substrate is sequentially grown with the N-InP buffer layer, the AlInGaAs multi-quantum-well active region 8, the P-InP grating isolation layer 9, the P-InGaAs P grating layer 10, the P-InP isolation layer 11, and the P-InGaAs surface layer 12.

[0065] like Figure 2 As shown, in the first step, the SiO2 dielectric layer 13 is deposited on the P-InGaAs surface layer 12 using the PECVD method. The thickness of the SiO2 dielectric layer 13 is 200 nm. The photolithography mask strips are perpendicular to the grating strips 14 inside the wafer. The photolithography process uses the main alignment notch 16 and the secondary alignment notch 17 of the wafer as alignment marks. The width of the photolithography mask strips ranges from 4.3 to 4.5 μm, the spacing between the photolithography mask strips is 250 μm, and the width of the SiO2 strip film 15 is 4.0 to 4.2 μm.

[0066] After the SiO2 strip film 15 is etched, the wafer surface is cleaned with photoresist solvent, and then an oxygen ion cleaner is used to remove the residual photoresist on the wafer surface.

[0067] like Figure 3 As shown, the etching solution in the second step is a mixture of hydrobromic acid, hydrogen peroxide and water. The depth of the BH mesa is 2.0-3.0 μm. During etching, the BH mesa passes through the AlInGaAs multi-quantum-well active region 8 and enters the N-InP wafer substrate region.

[0068] The specific steps for cleaning the surface of a BH countertop are as follows:

[0069] S21, the wafer with the etched BH mesa is immersed in acetone and isopropanol organic solvents in sequence, and the immersion time of the wafer in acetone and isopropanol organic solvents is 3 minutes each.

[0070] S22, After the wafer is soaked in organic solvent, it is cleaned with deionized water for no less than 5 minutes, and then the water on the surface of the wafer is dried with a pure N2 gun.

[0071] S23, immerse the wafer in concentrated sulfuric acid solution for 5 minutes, then remove the wafer from the concentrated sulfuric acid solution and clean it with deionized water for no less than 5 minutes. Use a pure N2 gun to blow dry the remaining water on the surface of the wafer.

[0072] S24, the cleaned wafer is transferred into the wafer glove box and the pressure is evacuated to a low level. Then, the wafer is transferred from the wafer glove box into the MOCVD epitaxial growth chamber through the mechanical transfer device of the MOCVD system for subsequent epitaxial growth.

[0073] The surface cleaning process for BH (Bright H) wafers involves first cleaning the Al-containing wafer surface with an organic solvent to remove trace amounts of organic residue. Then, the wafer is immersed in a concentrated sulfuric acid solution, which removes the oxidized Al layer and simultaneously passivates it, reducing the chemical reactivity of the Al molecules on the wafer surface and inhibiting the reaction between the Al layer and oxygen in the air. This improves the quality and efficiency of subsequent epitaxial growth of the current barrier layer structure in the BH structure.

[0074] The specific steps for epitaxial growth of the current blocking layer structure on both sides of the wafer BH mesa in the third step are as follows:

[0075] S31, the wafer transferred into the MOCVD epitaxial growth chamber is evacuated to a low pressure and maintained at a low pressure, and H2 is introduced into the MOCVD epitaxial growth chamber as the carrier gas for epitaxial growth, and then the MOCVD epitaxial growth chamber is heated.

[0076] S32, when the temperature of the MOCVD epitaxial growth chamber reaches 200℃, 500 sccm of PH3 gas is introduced into the MOCVD epitaxial growth chamber.

[0077] S33, when the temperature of the MOCVD epitaxial growth chamber reaches 400℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 400℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again.

[0078] S34, when the temperature of the MOCVD epitaxial growth chamber reaches 500℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 500℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again.

[0079] S35, when the temperature of the MOCVD epitaxial growth chamber reaches 620℃, after the temperature of the MOCVD epitaxial growth chamber is kept constant at 620℃ for 30 minutes, saturated TMI gas is introduced into the MOCVD epitaxial growth chamber at this temperature to epitaxially grow an InP thin isolation layer 1 at the bottom of the BH mesa of the wafer. The growth rate of the InP thin isolation layer 1 is 0.3nm / sec.

[0080] S36, after the InP thin isolation layer 1 is epitaxially grown, the temperature of the MOCVD epitaxial growth chamber is maintained at 620℃. DEZn saturated gas is introduced into the MOCVD epitaxial growth chamber to epitaxially grow a medium-doped P-InP layer 2 at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 5E17cm. -3 The growth rate of the P-InP medium doping concentration layer 2 is 0.3 nm / sec;

[0081] S37, after the epitaxial growth of the medium-doped P-InP layer 2 is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, adjust the flow rate of the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber, and epitaxially grow the low-doped P-InP layer 3 at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 2E17cm⁻¹. -3 The growth rate of the low-doped P-InP layer 3 was 0.3 nm / sec;

[0082] S38, after the epitaxial growth of the low-doped P-InP layer 3 is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and switch the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber to Si2H6 gas. Epitaxially grow the low-doped N-InP layer 4 on the bottom of the BH mesa of the wafer, so that the N-type doping concentration of N-InP is 2E17cm⁻¹. -3 The growth rate of the low-doped N-InP layer 4 was 0.3 nm / sec;

[0083] S39, after the low-doped N-InP layer 4 is epitaxially grown, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, adjust the Si2H6 gas flow rate introduced into the MOCVD epitaxial growth chamber, and epitaxially grow a high-doped N-InP layer 5 at the bottom of the BH mesa of the wafer, so that the N-type doping concentration of N-InP is 3E18 cm⁻¹. -3 The growth rate of the N-InP high-doped layer 5 was 0.3 nm / sec;

[0084] S40, after the high-doped N-InP layer 5 is epitaxially grown, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and switch the Si2H6 gas introduced into the MOCVD epitaxial growth chamber to DEZn saturated gas. Epitaxially grow the P-InP surface capping layer 6 on the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 7E17cm⁻¹. -3 The growth rate of the P-InP surface capping layer 6 is 0.3 nm / sec;

[0085] S41, After the epitaxial growth of the P-InP surface capping layer 6 is completed, the other gases supplied to the MOCVD epitaxial growth chamber are shut off, while the PH3 and H2 gases supplied to the MOCVD epitaxial growth chamber are retained, and the MOCVD epitaxial growth chamber is cooled down; when the temperature of the MOCVD epitaxial growth chamber drops to 200℃, the PH3 gas supplied to the MOCVD epitaxial growth chamber is shut off.

[0086] S42, when the temperature of the MOCVD epitaxial growth chamber drops to 50°C, the mechanical transfer device of the MOCVD system is used to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box, and then the wafer is transferred out from the wafer glove box to complete the epitaxial growth of the current barrier layer structure on both sides of the BH mesa of the wafer.

[0087] like Figure 4 As shown, a high-speed directly modulated AlInGaAs laser contains the aforementioned BH current blocking layer structure. Figure 4 The image shows a cross-section of an AlInGaAs multi-quantum BH-DFB laser containing the aforementioned BH structure, magnified 20,000 times after surface staining. The SEM image reveals a very smooth and complete epitaxial growth interface between the current-blocking layers on both sides of the BH mesa and the Al layer on the side, without any epitaxial voids caused by Al layer oxidation. Furthermore, the P-InP channel between the N-InP in the current-blocking layer of the BH and the protrusion on the P-side of the active region on the mesa side is controlled to approximately 0.1 μm, effectively suppressing the current leakage effect in the P-InP channel of the BH-DFB laser. With the same laser cavity length, the laser of this invention exhibits a similar threshold current and slope efficiency of output optical power to the conventional InGaAsP multi-quantum-well BH-DFB laser. This demonstrates that the present invention effectively suppresses interface defects and internal losses caused by Al layer oxidation in the BH structure.

[0088] In the current blocking layer of a BH structure, a reverse P / N junction is commonly used to block current on both sides of the BH mesa. Therefore, when the semiconductor materials on both sides of the P / N junction operate under reverse bias, they must have a small electron / hole depletion layer thickness to prevent localized breakdown due to reverse voltage. This requires the semiconductor materials on both sides of the P / N junction to have a sufficiently high doping concentration. However, the charge Q on both sides of the P / N junction must satisfy…

[0089]

[0090] Where V is the reverse bias voltage, V0 is the built-in potential of the P / N junction, i.e., the Fermi level difference across the P / N junction, and N... A It is the doping concentration of the P-type semiconductor material, N DThis refers to the doping concentration of the N-type semiconductor material. Therefore, a higher doping concentration in the P / N junction will result in a larger amount of charge accumulating on both sides of the P / N junction; the parasitic capacitance C on both sides of the P / N junction satisfies...

[0091]

[0092] Therefore, under the same reverse bias voltage V and P / N junction built-in potential V0, the amount of charge generated is proportional to the size of the parasitic capacitance.

[0093] Therefore, ordinary BH barrier layer structures will inevitably produce a large parasitic capacitance effect, which is not conducive to the application of laser high modulation.

[0094] Thus, this invention proposes an optimized semiconductor doping concentration on both sides of the P / N junction to effectively reduce the parasitic capacitance of the BH current blocking layer structure; low-doped P-type and N-type semiconductor doping layers with a concentration of 3E17cm⁻¹ are used on both sides of the reverse P / N junction interface formed on the side of the BH mesa. -3 Furthermore, undoped materials can even be used in this region; the thickness of these two P-type and N-type semiconductor doped layers accounts for a certain thickness of the reverse P / N junction region, which is more than 40% of the depth of the BH mesa; an N-type high-doped layer (>2E18cm) is added on top of the N-type low-doped layer. -3 This ensures that under a certain reverse bias voltage, a thick reverse depletion layer can be effectively suppressed, thus preventing reverse voltage breakdown of the P / N junction and affecting the normal operation of the laser. The choice of a medium-doped P-type layer is primarily because the dopant in P-type III-V materials is zinc (Zn), which easily diffuses into the AlInGaAs multi-quantum well active region of the laser at epitaxial growth temperatures. This would reduce the luminous efficiency of the active region. Therefore, a medium-doped P-type layer is used below the low-doped P-type layer. A thin, undoped InP layer with a certain thickness is added below the P-type moderately doped layer to prevent reverse voltage breakdown. This thin layer is adjacent to the side of the BH mesa and is added to reduce the diffusion of Zn dopant from the P-type InP layer into the AlInGaAs multi-quantum well active region of the BH mesa, thus reducing the impact on the luminous efficiency of the laser's active region. Above the N-type high-doped layer is a thin P-InP surface capping layer, which is the top layer of the current blocking layers on both sides of the BH. In the next step of MOCVD epitaxial growth of the BH laser structure, P-InP / P-InGaAs resistive contact layers for laser P-type lasers will be continuously epitaxially grown on its surface. This P-InP layer provides a good surface material transition layer for the next step of MOCVD epitaxial growth.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser, wherein the current blocking layer structure is disposed on both sides of the BH mesa, characterized in that, This structure is based on Multiple doped concentration layers are epitaxially grown on both sides of the BH mesa, which is a mask strip. The doped concentration layers include a thin InP isolation layer, a medium doped P-InP layer, a low doped P-InP layer, a low doped N-InP layer, a high doped N-InP layer, and a P-InP surface capping layer. The doped concentration layers on both sides of the BH mesa, from top to bottom, are the P-InP surface capping layer, the high doped N-InP layer, the low doped N-InP layer, the low doped P-InP layer, the medium doped P-InP layer, and the thin InP isolation layer.

2. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, No dopant flow rate is set in the InP thin-layer isolation layer, and the thickness of the InP thin-layer isolation layer does not exceed 150 nm.

3. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, The doping concentration range of the medium doping concentration layer of the P-InP is 5E17. -7E17 The thickness of the medium doping concentration layer of P-InP is 20%-30% of the depth of the BH mesa.

4. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, The doping concentration of the low-doped P-InP layer is no higher than 3E17. The thickness of the low-doping concentration layer of P-InP is not less than 20% of the depth of the BH mesa.

5. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, The doping concentration of the low-doped N-InP layer is no higher than 3E17. The thickness of the low-doping concentration N-InP layer is not less than 20% of the depth of the BH mesa.

6. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, The doping concentration of the high-doped N-InP layer is not less than 2E18. The thickness of the high doping concentration N-InP layer is 20%-30% of the depth of the BH mesa.

7. The BH current blocking layer structure for a high-speed direct-modulation AlInGaAs laser according to claim 1, characterized in that, The doping concentration of the surface coating layer of P-InP is not less than 8E17. The thickness of the high doping concentration layer of P-InP does not exceed 5% of the depth of the BH mesa.

8. A method for fabricating a BH current blocking layer structure for a high-speed direct-modulated AlInGaAs laser, used to fabricate the BH current blocking layer structure as described in any one of claims 1-7, characterized in that, The method specifically includes the following steps: The first step is to deposit a layer on the wafer surface of the AlInGaAs laser. Dielectric layer, and for Multiple parallel photomask strips are photolithographically etched onto the dielectric layer, and then the photomask strips are etched using ICP-RIE dry etching. Strip film; The second step is to use a corrosive liquid to... The strip film is etched to form the BH platform, and the BH platform is then cleaned. The third step is to place the cleaned BH mesa on the wafer surface into the MOCVD epitaxial growth chamber, and grow current blocking layer structures on both sides of the BH mesa in the MOCVD epitaxial growth chamber by metal-organic chemical vapor deposition (MOCVD). The fourth step, after the current barrier layer structure has been grown, is to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box using the mechanical transfer device of the MOCVD system, thus completing the fabrication of the current barrier layer structure.

9. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 8, characterized in that, The wafer structure of the AlInGaAs laser in the first step includes an N-InP wafer substrate and an N-InP buffer layer, an AlInGaAs multi-quantum-well active region, a P-InP grating isolation layer, a P-InGaAs P grating layer, a P-InP isolation layer, and a P-InGaAs surface layer. The N-InP wafer substrate is sequentially grown with the N-InP buffer layer, the AlInGaAs multi-quantum-well active region, the P-InP grating isolation layer, the P-InGaAs P grating layer, the P-InP isolation layer, and the P-InGaAs surface layer.

10. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 8, characterized in that, The first step The dielectric layer was deposited on the P-InGaAs surface layer using the PECVD method. The dielectric layer thickness is 200 nm. The photomask strips are perpendicular to the grating strips inside the wafer. The width of the photomask strips ranges from 4.3 to 4.5 μm, and the spacing between the photomask strips is 250 μm. The width of the strip film is 4.0-4.2μm.

11. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 10, characterized in that, The After the strip-shaped film etching is completed, the wafer surface is cleaned with photoresist solvent, and then an oxygen ion cleaner is used to remove the residual photoresist on the wafer surface.

12. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 8, characterized in that, The etching solution in the second step is a mixture of hydrobromic acid, hydrogen peroxide and water. The depth of the BH mesa is 2.0-3.0 μm. During etching, the BH mesa passes through the AlInGaAs multi-quantum-well active region and enters the N-InP wafer substrate region.

13. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 12, characterized in that, The specific steps for cleaning the BH countertop are as follows: S21, the wafer with the etched BH mesa is immersed in acetone and isopropanol organic solvents in sequence, and the immersion time of the wafer in acetone and isopropanol organic solvents is 3 minutes each. S22, After the wafer is soaked in the organic solvent, it is cleaned with deionized water for at least 5 minutes, followed by cleaning with pure water. The gun dries the water remaining on the surface of the wafer; S23, immerse the wafer in concentrated sulfuric acid solution for 5 minutes, then remove the wafer from the concentrated sulfuric acid solution and rinse with deionized water for at least 5 minutes. The gun dries the water remaining on the surface of the wafer; S24, the cleaned wafer is transferred into the wafer glove box and the pressure is evacuated to a low level. Then, the wafer is transferred from the wafer glove box into the MOCVD epitaxial growth chamber through the mechanical transfer device of the MOCVD system for subsequent epitaxial growth.

14. The method for fabricating a BH current blocking layer structure for a high-speed directly modulated AlInGaAs laser according to claim 8, characterized in that, The specific steps for epitaxial growth of the current blocking layer structure on both sides of the wafer BH mesa in the third step are as follows: S31, the wafer transferred into the MOCVD epitaxial growth chamber is evacuated to a low pressure and maintained at a low pressure, while air is introduced into the MOCVD epitaxial growth chamber. The MOCVD epitaxial growth chamber is then heated using the carrier gas for epitaxial growth. S32, when the temperature of the MOCVD epitaxial growth chamber reaches 200℃, 500 sccm of oxygen is introduced into the MOCVD epitaxial growth chamber. gas; S33, when the temperature of the MOCVD epitaxial growth chamber reaches 400℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 400℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again. S34, when the temperature of the MOCVD epitaxial growth chamber reaches 500℃, the temperature of the MOCVD epitaxial growth chamber is kept constant at 500℃ for 30 minutes, and then the temperature of the MOCVD epitaxial growth chamber is increased again. S35, when the temperature of the MOCVD epitaxial growth chamber reaches 620℃, after the temperature of the MOCVD epitaxial growth chamber is kept constant at 620℃ for 30 minutes, saturated TMI gas is introduced into the MOCVD epitaxial growth chamber at this temperature to epitaxially grow an InP thin isolation layer at the bottom of the BH mesa of the wafer. The growth rate of the InP thin isolation layer is 0.3nm / sec. S36, After the InP thin isolation layer epitaxial growth is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and introduce DEZn saturated gas into the MOCVD epitaxial growth chamber to epitaxially grow a medium-doped P-InP layer at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 5E17. The growth rate of the P-InP medium doping concentration layer is 0.3 nm / sec; S37, after the epitaxial growth of the medium-doped P-InP layer is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, adjust the flow rate of the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber, and epitaxially grow a low-doped P-InP layer at the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 2E17. The growth rate of the low-doped P-InP layer was 0.3 nm / sec; S38, after the low-doped P-InP layer epitaxial growth is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃, and control the switching of the DEZn saturated gas introduced into the MOCVD epitaxial growth chamber to be... Gas is used to epitaxially grow a low-doped N-InP layer at the bottom of the BH mesa of the wafer, so that the N-type doping concentration of N-InP is 2E17. The growth rate of the low-doped N-InP layer was 0.3 nm / sec; S39, After the low-doped N-InP layer has been epitaxially grown, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃ and adjust the airflow into the MOCVD epitaxial growth chamber. Gas flow rate is used to epitaxially grow a high-doped N-InP layer at the bottom of the BH mesa of the wafer, achieving an N-type doping concentration of 3E18 for the N-InP. The growth rate of the N-InP high-doped-concentration layer was 0.3 nm / sec; S40, after the high-doped N-InP layer epitaxial growth is completed, maintain the temperature of the MOCVD epitaxial growth chamber at 620℃ and control the switching of the gas supply in the MOCVD epitaxial growth chamber. The gas is DEZn saturated gas. A P-InP surface capping layer is epitaxially grown on the bottom of the BH mesa of the wafer, so that the P-type doping concentration of P-InP is 7E17. The growth rate of the P-InP surface capping layer is 0.3 nm / sec; S41, After the epitaxial growth of the P-InP surface capping layer is completed, shut off all other gases supplied to the MOCVD epitaxial growth chamber, while maintaining the gas supply to the MOCVD epitaxial growth chamber. and Gas was introduced to cool the MOCVD epitaxial growth chamber; when the temperature of the MOCVD epitaxial growth chamber dropped to 200℃, the gas supply to the MOCVD epitaxial growth chamber was shut off. gas; S42, when the temperature of the MOCVD epitaxial growth chamber drops to 50°C, the mechanical transfer device of the MOCVD system is used to transfer the wafer from the MOCVD epitaxial growth chamber to the wafer glove box, and then the wafer is transferred out from the wafer glove box to complete the epitaxial growth of the current barrier layer structure on both sides of the BH mesa of the wafer.

15. A high-speed directly modulated AlInGaAs laser, characterized in that, The laser contains the BH current blocking layer structure as described in any one of claims 1-14.

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