CN115986567A - Laser with double-end surface emission and preparation method thereof - Google Patents

Abstract

One aspect of the present invention provides a double-end surface light-emitting laser and a preparation method thereof. The double-end surface light-emitting laser includes: a substrate; a rear grating area formed on the substrate, and phases are symmetrically distributed on both sides of the rear grating area from near to far. area, gain area, front grating area, and modulator area; wherein, the rear grating area and the front grating area are composed of grating layers, and the grating layer surfaces of the rear grating area and the front grating area have gratings. The invention realizes the effect of doubling the laser speed and wavelength tuning performance, and provides a new solution for the optical emission chip for the optical communication system.

Description

Double end surface emitting laser and its preparation method

technical field

The invention relates to the field of semiconductor optoelectronic integrated devices, and relates to a laser, in particular to a double-end light emitting laser and a preparation method thereof.

Background technique

With the rapid development of 5G networks, optical fiber communication systems put forward higher requirements for the performance of optical transmitter chips, among which high speed and multi-wavelength coverage are two important development directions to meet the needs of the Internet. The speed of the optical transmitter chip is restricted by the physical mechanism and process precision, and it will become more and more difficult to increase the speed. To solve the speed increase, bandwidth expansion technology, external modulation technology, etc. are often used; multi-wavelength coverage is to make full use of the existing The optical fiber resources of the network meet different application scenarios of the Internet. At present, the multi-wavelength solution is mostly implemented by connecting multiple fixed-wavelength lasers in parallel or using wavelength-tunable lasers. The use of these technologies will bring many problems: the integration of the chip becomes larger, the size becomes larger, the power consumption becomes higher, and the cost increases.

Contents of the invention

(1) Technical problems to be solved

In view of this, on the one hand, the present invention provides a double-end surface-emitting laser, and on the other hand, it provides a preparation method of a double-end surface-emitting laser, which is used to at least partially solve the above problems.

(2) Technical solution

On the one hand, the present invention provides a double-end light-emitting laser, including: a substrate; a rear grating area, formed on the substrate, and a phase area, a gain area, and a front grating area are symmetrically distributed on both sides of the rear grating area from near to far. . The modulator area; wherein, the rear grating area and the front grating area are composed of a grating layer, and the surface of the grating layer in the rear grating area and the front grating area has a grating.

Optionally, the modulator region is 10-100 nm shorter than the bandgap wavelength of the gain region.

Optionally, the bandgap wavelength of the rear grating region, the front grating region and the phase region is 90-200 nm shorter than that of the gain region.

Optionally, the double-end surface-emitting laser further includes: the gain region is composed of a first lower waveguide layer, a first multi-quantum well active region, and a first upper waveguide layer stacked on the substrate in sequence; the modulator region is composed of sequentially stacked The second lower waveguide layer, the second multi-quantum well active region and the second upper waveguide layer are formed on the substrate; the inverted shallow ridge waveguide is formed on the first upper waveguide layer, the second upper waveguide layer and the grating layer , the inverted shallow ridge waveguide includes a cladding layer and an electrical contact layer from bottom to top; the P electrode is formed on the surface of the inverted shallow ridge waveguide; the N electrode is formed on the bottom of the substrate.

Optionally, the thickness of the grating layer is the total thickness of the first lower waveguide layer, the first multiple quantum well active region and the first upper waveguide layer.

Another aspect of the present invention provides a method for manufacturing the above-mentioned double-end surface emitting laser, including: sequentially forming a first lower waveguide layer, a first multi-quantum well active region, and a first upper waveguide layer on a substrate; Prepare the first _SiO2 strip structure from an upper waveguide layer; etch away the first lower waveguide layer covered by the first _SiO2 strip structure, the first multi-quantum well active region and the first upper waveguide layer, and grow the second The second lower waveguide layer, the second multi-quantum well active region and the second upper waveguide layer; the first _SiO2 strip structure is removed and the second _SiO2 strip structure is prepared on the first upper waveguide layer and the second upper waveguide layer; Etching away the first _lower waveguide layer covered by the second SiO strip structure, the first multi-quantum well active region, the first upper waveguide layer, the second lower waveguide layer, the second multi-quantum well active region and the first multi-quantum well active region The second upper waveguide layer is connected to the growing grating layer; the grating is prepared on the surface of the grating layer; the cladding layer and the electrical contact layer are formed on the surface of the first upper waveguide layer, the second upper waveguide layer and the grating layer, and the cladding layer and the electrical contact layer are prepared. Inverting the shallow ridge waveguide; performing photolithography and ion implantation on the electrical contact layer; preparing a P electrode on the inverted shallow ridge waveguide and an N electrode at the bottom of the substrate.

Optionally, preparing the first _SiO2 strip structure on the first upper waveguide layer includes: growing a _SiO2 layer on the first upper waveguide layer;

The first SiO ₂ strip structure is prepared in the gain region and the gain region by photolithography and wet etching.

Optionally, removing the first _SiO2 strip structure and preparing the second _SiO2 strip structure on the first upper waveguide layer and the second upper waveguide layer includes: removing the first _SiO2 strip structure by etching; The SiO ₂ layer is grown on the layer and the first upper waveguide layer; the second SiO ₂ strip structure is prepared in the modulator area, the modulator area, the gain area and the gain area by photolithography and wet etching.

Optionally, etch away the first lower waveguide layer covered by the first _SiO2 strip structure, the first multi-quantum well active region and the first upper waveguide layer and etch away the second _SiO2 Strip structure covered The first lower waveguide layer, the first multi-quantum well active region, the first upper waveguide layer, the second lower waveguide layer, the second multi-quantum well active region and the second upper waveguide layer include: using CH ₄ and H ₂ Perform RIE etching; after etching, the substrate is cleaned with trichlorethylene, acetone, and ethanol; H ₂ SiO ₄ and H ₂ O ₂ are used to etch the etched defects.

Optionally, performing photolithography on the electrical contact layer and performing ion implantation includes: etching an isolation trench pattern on the electrical contact layer; etching the electrical isolation trench and performing He ion implantation.

(3) Beneficial effects

The present invention integrates two wavelength tunable electro-absorption lasers back to back, shares the distributed Bragg grating area, emits laser light from two end faces, realizes the effect of doubling the speed and wavelength tuning performance, and reduces the power consumption of the Bragg grating area at the same time. A solution for a new light emitting chip is provided for an optical communication system.

Description of drawings

Fig. 1 schematically shows the flow chart of the preparation method of the double end surface emitting laser provided by the present invention;

FIG. 2 schematically shows a schematic diagram of step S1 of the method for preparing a double-end surface emitting laser provided by the present invention;

FIG. 3 schematically shows a top view of step S2 of the method for manufacturing a double-end surface emitting laser provided by the present invention;

FIG. 4 and FIG. 5 schematically show a schematic diagram of step S3 of the method for manufacturing a double-end surface emitting laser provided by the present invention;

Fig. 6 schematically shows a schematic diagram of step S4 of the preparation method of a double-end surface emitting laser provided by the present invention;

Fig. 7 and Fig. 8 schematically show the schematic diagram of the step S5 of the preparation method of the double end surface emitting laser provided by the present invention;

FIG. 9 schematically shows a schematic diagram of step S6 of the method for preparing a double-end surface emitting laser provided by the present invention;

FIG. 10 schematically shows a schematic diagram of step S7 of the method for manufacturing a double-end surface emitting laser provided by the present invention;

FIG. 11 schematically shows a schematic diagram of step S8 of the method for preparing a double-end surface emitting laser provided by the present invention;

FIG. 12 schematically shows a schematic diagram of step S9 of the method for manufacturing a double-end surface emitting laser provided by the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Referring to FIG. 12, FIG. 12 schematically shows a schematic structural view of a double-end surface emitting laser provided by the present invention. The present invention provides a double-end surface emitting laser, including: a substrate; a rear grating region, formed on the substrate, and a rear On both sides of the grating area, there are phase area, gain area, front grating area, and modulator area symmetrically distributed in order from near to far; among them, the rear grating area and the front grating area are composed of grating layers, and the grating layers of the rear grating area and the front grating area The surface has a grating; the phase region is composed of the same material as the grating layer; the gain region is composed of the first lower waveguide layer, the first multi-quantum well active region and the first upper waveguide layer stacked on the substrate; the modulator The region is composed of the second lower waveguide layer, the second multi-quantum well active region and the second upper waveguide layer stacked on the substrate in sequence. As shown in Figure 12, areas 1 and 5 are the modulator area, areas 2 and 6 are the rear grating area, areas 3 and 7 are the laser gain area, areas 4 and 8 are the phase area, and area 9 is the rear grating area. are distinguished by dotted lines. Among them, the thicknesses of the first lower waveguide layer, the first multi-quantum well active region, the first upper waveguide layer and the second lower waveguide layer, the second multi-quantum well active region and the second upper waveguide layer are independently optimized according to performance; The thickness of the grating layer is the total thickness of the first lower waveguide layer, the first multi-quantum well active region and the first upper waveguide layer.

In the dual-end surface light-emitting laser provided by the present invention, two wavelength-tunable electro-absorption lasers are integrated together, share the distributed Bragg grating area, and emit laser light from two end surfaces, thereby achieving the effect of doubling the speed and wavelength tuning performance.

In one embodiment of the present invention, the bandgap wavelength of the modulator region is 10-100 nm shorter than that of the gain region. The bandgap wavelength of the rear grating region, front grating region and phase region is 90-200nm shorter than that of the gain region. The bandgap wavelength of the modulator is short, and the reverse bias is applied during operation, the absorption spectrum is red-shifted, and the laser light generated by the laser is absorbed; while the bandgap wavelength of the grating area and the phase area is short, when the laser light generated by the laser passes through these areas, the laser light Not absorbed.

In yet another embodiment of the present invention, the double-end surface light-emitting laser further includes: an inverted shallow ridge waveguide formed on the first upper waveguide layer, the second upper waveguide layer and the grating layer, and the inverted shallow ridge waveguide includes a package from bottom to top. Layer, electrical contact layer; P electrode, formed on the surface of the inverted shallow ridge waveguide; N electrode, formed on the bottom of the substrate.

Referring to FIG. 1, FIG. 1 schematically shows another aspect of the present invention also provides a flow chart of a method for manufacturing a double-end surface emitting laser as described above, including:

S1, sequentially forming a first lower waveguide layer 11, a first multiple quantum well active region 12, and a first upper waveguide layer 13 on the substrate 10;

S2. Prepare a first _SiO2 strip structure 14 on the first upper waveguide layer 13;

S3, etch away the first lower waveguide layer 11 covered by the first _SiO2 strip structure 14, the first multi-quantum well active region 12 and the first upper waveguide layer 13, and grow the second lower waveguide layer 15, the second waveguide layer Two multi-quantum well active regions 16 and a second upper waveguide layer 17;

S4, removing the first SiO ₂ strip structure 14 and preparing a second SiO ₂ strip structure 18 on the first upper waveguide layer 13 and the second upper waveguide layer 17;

S5, etch away the first lower waveguide layer 11 covered by the second _SiO2 strip structure 18, the first multi-quantum well active region 12, the first upper waveguide layer 13, the second lower waveguide layer 15, the second multi-quantum well The quantum well active region 16 and the second upper waveguide layer 17 are connected to the growth grating layer 19;

S6, preparing a grating 20 on the surface of the grating layer 19;

S7, forming a cladding layer 21 and an electrical contact layer 22 on the surfaces of the first upper waveguide layer 13, the second upper waveguide layer 17, and the grating layer 19, and preparing a layer-inversion shallow ridge waveguide for the cladding layer 21 and the electrical contact layer 22;

S8, performing photolithography and ion implantation on the electrical contact layer 22;

S9 , preparing the P electrode 24 on the inverted shallow ridge waveguide and the N electrode 25 at the bottom of the substrate 10 .

Wherein, step S2 includes: growing a SiO ₂ layer on the first upper waveguide layer 13; preparing the first SiO ₂ strip structure 14 in the gain region 3 and the gain region 7 by photolithography and wet etching.

Step S4 includes: removing the first _SiO2 strip structure 14 by etching; growing a _SiO2 layer on the second upper waveguide layer 17 and the first upper waveguide layer 13; 5 and gain region 3 and gain region 7 to prepare the second SiO ₂ strip structure 18.

Steps S3 and S5 include: performing RIE etching with CH ₄ and H ₂ ; cleaning the substrate 10 with trichlorethylene, acetone, and ethanol respectively after etching; using H ₂ SiO ₄ and H ₂ O ₂ to etch the etched defect.

Step S8 includes: etching an isolation trench pattern on the electrical contact layer 22; etching the electrical isolation trench and performing He ion implantation.

The following will be described in conjunction with specific embodiments.

S1, select the N-type indium phosphide substrate 10, and utilize organometallic compound vapor deposition (MOCVD) to sequentially grow the InGaAsP lower waveguide layer 11 (bandgap wavelength is 1200nm), the multi-quantum well active region 12 (bandgap) on the substrate The wavelength is 1550nm), and the upper waveguide layer 13 (the bandgap wavelength is 1200nm). The growth temperature is 680°C, the growth pressure is 100mbar, the thickness of the upper and lower waveguide layers is 90nm, 5 compressive strain well layers, each layer thickness is 5nm, and 6 tensile strain barrier layers, each layer thickness is 9nm. The source region 12 is sandwiched by the lower waveguide layer 11 and the upper waveguide layer 13 to form a sandwich structure. as shown in picture 2.

S2, grow a 150nm thick SiO ₂ layer on the upper waveguide layer 13, the growth temperature is 300°C, and the growth pressure is 100Pa; and a 1μm thick photoresist mask is used to etch a 30μm wide layer using buffered oxide etching solution (BOE). The first SiO ₂ strip structure 14 is used to protect the gain region of the laser, and its top view is shown in FIG. 3 .

S3. Use the RIE method to etch and remove the InGaAsP material outside the mask of the laser gain region (3 and 7 regions), the reaction etching pressure is 0.067mbar, the power is 150W, the reaction gas is CH4:H ₂ =18:45, etch The time is 5 minutes, as shown in Figure 4. Clean the substrate 10 with trichlorethylene, acetone and ethanol respectively, etch away the remaining InGaAsP material after RIE etching with H ₂ SiO ₄ and H ₂ O ₂ , dry the substrate and soak it in concentrated H ₂ SiO ₄ solution 20 seconds for surface passivation; then rinse with deionized water and dry; use MOCVD to grow InGaAsP lower waveguide layer 15 (bandgap wavelength is 1200nm), multiple quantum well active region 16 (bandgap wavelength is 1500nm), The upper waveguide layer 17 (with a bandgap wavelength of 1200 nm). The growth temperature is 680°C, the growth pressure is 100mbar, the thickness of the upper and lower waveguide layers is 90nm, 5 compressive strain well layers, each layer thickness is 9nm, and 6 tensile strain barrier layers, each layer thickness is 5nm, as shown in Figure 5 Show.

S4, etch away the first _SiO2 strip structure 14, grow the _SiO2 layer again, use photolithography and wet etching to get the second _SiO2 strip structure 18 with a width of 20 μm in the laser gain region and modulator region, as shown in Figure 6 shown.

S5. Use RIE method to etch away the InGaAsP material other than the second SiO ₂ strip structure 18, the reaction etching pressure is 0.067mbar, the power is 150W, the reaction gas is CH ₄ : H ₂ =18:45, and the etching time is 5 minutes, as shown in Figure 7. Clean the substrate 10 with trichlorethylene, acetone, and ethanol respectively, etch away the remaining InGaAsP material after RIE etching with H ₂ SiO ₄ and H ₂ O ₂ , and dry the substrate 10 in a concentrated H ₂ SiO ₄ solution Soak for 20 seconds to passivate the surface; then rinse with deionized water and dry; use MOCVD to connect the grating regions (2, 6 and 9 regions) and the phase region (4 and 8 regions) grating layer 19 before and after growth, using InGaAsP material , the growth temperature is 630°C, the growth pressure is 100mbar, and its bandgap wavelength (1400nm) is smaller than the laser emission wavelength, as shown in Figure 8.

S6. Fabricate a grating 20 on the surface of the grating layer 19 in the front and rear grating regions (regions 2, 6 and 9), as shown in FIG. 9 .

S7. MOCVD growth of P-type Zn-doped InP cladding layer 21 (1500nm thick) and InGaAs electrical contact layer 22 (200nm thick) on the surface of the first upper waveguide layer 13, the second upper waveguide layer 17 and the grating layer 19, the growth temperature is 630°C and a growth pressure of 100mbar. On the cladding layer 21 and the electrical contact layer 22, use a 1 μm photoresist to photoetch a 3 μm strip mask, and use an etching solution _Br2 :HBr _: H2O=1:25:80 (etching time is 40 seconds) ) and HCl:H ₂ O=9:1 (etching time is 3 minutes) to produce an inverted shallow ridge waveguide structure, the cross-sectional view is shown in FIG. 10 .

S8. Use a 3 μm thick photoresist to photoetch an isolation trench pattern on the electrical contact layer 22, etch with an etching solution H ₂ SiO ₄ : _{H 2} O ₂ :H ₂ O=3:1:1 for 10 seconds, and etch out each area At the same time, He ion implantation 23 is performed on the isolation trench, the implantation energy is 200KeV, and the implantation dose is 10 ¹⁴ cm ^-2 , so as to realize electrical isolation between each functional area, as shown in Figure 11 Show.

S9. Fabricate a P-surface electrode 24 on the electrode contact layer 22, fabricate an N-surface electrode 25 at the bottom after the substrate 10 is thinned, as shown in FIG. 11 .

The above specific embodiments have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included within the protection scope of the present invention.

Claims (10)

1. A kind of laser with double end face, is characterized in that, comprises: Substrate (10); A rear grating area (9) is formed on the substrate, and phase areas (4, 8), gain areas (3, 7), front Grating area (2, 6), modulator area (1, 5); Wherein, the rear grating area (9) and the front grating area (2, 6) are composed of a grating layer (19), and the surface of the grating layer (19) has a grating (20). 2. The double-end surface emitting laser according to claim 1, characterized in that the bandgap wavelength of the modulator region (1, 5) is 10-100 nm shorter than that of the gain region (3, 7). 3. The double-end surface emitting laser according to claim 1, characterized in that, the rear grating region (9), the front grating region (2, 6), the phase region (4, 8) and the gain region The bandgap wavelengths of (3, 7) are 90 to 200 nm shorter than those of (3, 7). 4. The double-end surface emitting laser according to claim 1, wherein the double-end surface emitting laser further comprises: The gain region (3, 7) consists of a first lower waveguide layer (11), a first multi-quantum well active region (12) and a first upper waveguide layer ( 13) Composition; The modulator region (1, 5) consists of a second lower waveguide layer (15), a second multi-quantum well active region (16) and a second upper waveguide layer stacked on the substrate (10) in sequence (17) constitute; The inverted shallow ridge waveguide is formed on the first upper waveguide layer (13), the second upper waveguide layer (17) and the grating layer (19), and the inverted shallow ridge waveguide includes cladding ( 21), electrical contact layer (22); The P electrode (24) is formed on the surface of the inverted shallow ridge waveguide; The N electrode (25) is formed on the bottom of the substrate (10). 5. the double end surface light emitting laser device according to claim 4, is characterized in that, described grating layer (19) thickness is described the first lower waveguide layer (11), the first multi-quantum well active region (12) and The total thickness of the first upper waveguide layer (13). 6. A method for preparing a double-end surface emitting laser according to any one of claims 1 to 5, characterized in that it comprises: sequentially forming a first lower waveguide layer (11), a first multiple quantum well active region (12) and a first upper waveguide layer (13) on a substrate (10); Preparing a first SiO _strip structure (14) at the first upper waveguide layer (13); Etching away the first lower waveguide layer (11), the first multi-quantum well active region (12) and the first upper waveguide layer (13) covered by the first SiO _strip structure (14) and Butt growing the second lower waveguide layer (15), the second multi-quantum well active region (16) and the second upper waveguide layer (17); removing the first _SiO2 strip structure (14) and preparing a second _SiO2 strip structure (18) on the first upper waveguide layer (13) and the second upper waveguide layer (17); Etching away the first _lower waveguide layer (11), the first multi-quantum well active region (12), the first upper waveguide layer (13) covered by the second SiO strip structure (18), The second lower waveguide layer (15), the second multi-quantum well active region (16) and the second upper waveguide layer (17) are connected to the growth grating layer (19); preparing a grating (20) on the surface of the grating layer (19); A cladding layer (21), an electrical contact layer (22) is formed on the surfaces of the first upper waveguide layer (13), the second upper waveguide layer (17) and the grating layer (19), and the cladding layer (21), The electrical contact layer (22) prepares layer inverted shallow ridge waveguides; performing photolithography and ion implantation on the electrical contact layer (22); A P electrode (24) is prepared on the inverted shallow ridge waveguide and an N electrode (25) is prepared at the bottom of the substrate (10). 7. The preparation method according to claim 6, characterized in that preparing the _first SiO strip structure (14) at the first upper waveguide layer (13) comprises: growing _{a SiO} layer on the first upper waveguide layer (13); The first _SiO2 strip structure (14) is prepared in the gain region (3) and the gain region (7) by photolithography and wet etching. 8. The preparation method according to claim 6, characterized in that, the first SiO _strip structure (14) is removed and the first upper waveguide layer (13) and the second upper waveguide layer ( 17) preparing the second _SiO2 strip structure (18) comprising: Etching and removing the first SiO ₂ strip structures (14); growing _a SiO layer on the second upper waveguide layer (17) and the first upper waveguide layer (13); The second _SiO2 strip structure (18) is prepared in the modulator area (1) and the modulator area (5) and the gain area (3) and the gain area (7) by photolithography and wet etching. 9. The preparation method according to claim 6, characterized in that, the etching removes the first lower waveguide layer (11) covered by the first SiO _strip structure (14), the first multilayer The quantum well active region (12) and the first upper waveguide layer (13) and the first lower waveguide layer (11) and the first lower waveguide layer (11) covered by the second _SiO2 strip structure (18) are removed by etching. A multi-quantum well active region (12), a first upper waveguide layer (13), a second lower waveguide layer (15), a second multiquantum well active region (16) and a second upper waveguide layer (17) include : RIE etching with CH ₄ and H ₂ ; After the etching, the substrate (10) is cleaned with trichlorethylene, acetone, and ethanol; The etched defects were etched with H ₂ SiO ₄ and H ₂ O ₂ . 10. The preparation method according to claim 6, characterized in that, performing photolithography and ion implantation on the electrical contact layer (22) comprises: Photoetching an isolation trench pattern on the electrical contact layer (22); Etch electrical isolation trenches and perform He ion implantation.

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