Method for preparing PN junction, PN junction and modulator

Abstract

This application discloses a PN junction, a method for preparing a PN junction, and a modulator. A PN junction includes a planar waveguide layer and a plurality of waveguides arranged at intervals along a specific direction on the planar waveguide layer. The planar waveguide layer includes P-type doped regions and N-type doped regions alternately arranged in a specific direction, and a carrier depletion region in an S shape that is end-to-end along the specific direction is formed at the junction of the two regions. Each of the plurality of waveguides arranged at intervals includes a P-type doped region and an N-type doped region, and a carrier depletion region is formed at the junction of the two regions. The projections of the P-type doped regions, N-type doped regions, and carrier depletion regions of the plurality of waveguides arranged at intervals on the surface of the planar waveguide region and the projections of the corresponding regions of the planar waveguide layer on the surface of the planar waveguide region basically coincide. The PN junction has a high modulation efficiency and low optical loss. Optionally, the PN junction can be realized by inclined angle ion implantation doping, which can reduce its manufacturing cost.

Description

Technical Field

[0001] This application relates to the field of optical devices, and particularly to a method for preparing a PN junction, a PN junction, and a modulator. Background Art

[0002] An optical modulator is an important device in an optical communication system, which is used to convert an electrical signal into an optical signal. Typical optical modulators include Mach-Zehnder modulators, microring modulators, etc. A PN junction is a key component of an optical modulator, which is formed by preparing a P-type doped region and an N-type doped region on an optical waveguide. A carrier depletion region will be formed at the junction of the P-type doped region and the N-type doped region. When the value of the applied reverse voltage changes, due to the plasma dispersion effect, the optical refractive index of the material will change in the carrier depletion region of the PN junction, causing the optical phase in the waveguide to change, thus playing a modulation role.

[0003] The performance of the modulator is closely related to the performance of the PN junction. For example, the overlap size between the carrier depletion region of the PN junction and the optical mode field of the light passing through the PN junction affects the modulation efficiency of the modulator. Another example is that the structural design of the PN junction affects the optical loss degree of the modulator.

[0004] Currently, designing a PN junction and a modulator with high modulation efficiency and low optical loss is an important research topic. Summary of the Invention

[0005] This application provides a method for preparing a PN junction, a PN junction, and a modulator to achieve a PN junction and a modulator with high modulation efficiency and low optical loss.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a PN junction. The method includes three steps. In the first step, with a set of first masks as a barrier, the optical waveguide is etched along a first direction to form a grating waveguide structure on the surface of the optical waveguide. The set of first masks is a plurality of masks arranged at intervals, and the grating waveguide structure includes a plurality of waveguide blocks arranged at intervals and the thickness of the grating waveguide structure is less than the thickness of the optical waveguide. In the second step, continuing with the set of first masks as a barrier, P-type ions are injected into the optical waveguide in a first injection direction, and the angle between the first injection direction and the first direction is between (10, 80) degrees, the angle between the first injection direction and the arrangement direction of the plurality of masks is between (0, 90) or (90, 180) degrees, and the angle between the first injection direction and a second direction is between (0, 90) or (90, 180) degrees, and the second direction is perpendicular to both the arrangement direction of the plurality of masks and the first direction. In the third step, continuing with the set of first masks as a barrier, N-type ions are injected into the optical waveguide in a second injection direction to form a carrier depletion region of the PN junction at the junction of the region where the P-type ions are located and the region where the N-type ions are located. The angle between the second injection direction and the first direction is between (10, 80) degrees, the angle between the second injection direction and the arrangement direction of the plurality of masks is between (90, 180) or (0, 90) degrees, and the angle between the second injection direction and the second direction is between (90, 180) or (0, 90) degrees.

[0007] It should be noted that, for the angle between the first injection direction and the arrangement direction of the plurality of masks and the angle between the second injection direction and the arrangement direction of the plurality of masks, one is an acute angle and the other is an obtuse angle. The same is true for the angle between the first injection direction and the second direction and the angle between the second injection direction and the second direction.

[0008] It should be understood that the present application does not limit the order of the above second and third steps. By injecting ions at an inclined angle and using a single mask method to fabricate a PN junction, the process is simple and the yield of the PN junction is relatively high. In addition, the modulation efficiency of the PN junction with a grating-like waveguide structure is relatively high and the optical loss is relatively low.

[0009] Optionally, before injecting P-type ions into the optical waveguide in the first injection direction, another mask is set on the region where the N-type ions are located. Optionally, before injecting N-type ions into the optical waveguide in the second injection direction, a third mask is set on the region where the P-type ions are located. These optional implementation manners can prevent ion doping into non-target waveguide regions and can further improve the yield of PN junction fabrication.

[0010] Optionally, the angle between the second injection direction and the angle of the axisymmetric direction of the first injection direction along the first direction is less than 10 degrees. Doing so can increase the volume of the waveguide occupied by the carrier depletion region, thereby further improving the modulation efficiency of the fabricated PN junction.

[0011] In a specific implementation, the selection of the injection angle depends on the height, width, spacing, etc. of multiple waveguide arrays arranged at intervals. For example, the angle between the first injection direction and the first direction can be 45 degrees, and the angle between the second injection direction and the first direction can be 45 degrees.

[0012] In a second aspect, an embodiment of the present application provides a PN junction. The PN junction includes a planar waveguide layer and a grating-shaped waveguide layer disposed on the planar waveguide layer. The grating-shaped waveguide layer includes a plurality of waveguide blocks arranged at intervals along a first direction. The planar waveguide layer includes a first P-type doped region and a first N-type doped region; the first P-type doped region includes a plurality of first protruding regions, and the first N-type doped region includes a plurality of second protruding regions; the first protruding regions and the second protruding regions are alternately arranged along the first direction. A first carrier depletion region is formed at the junction of the first P-type doped region and the first N-type doped region, and the first carrier depletion region is in an S shape connected end to end along the first direction. Each waveguide block includes a second P-type doped region and a second N-type doped region. A second carrier depletion region is formed at the junction of each pair of the second P-type doped region and the second N-type doped region. The projection of each second P-type doped region on the upper surface of the planar waveguide layer coincides with the projection of the first P-type doped region on the upper surface of the planar waveguide layer. The projection of each second N-type doped region on the upper surface of the planar waveguide layer coincides with the projection of the first N-type doped region on the upper surface of the planar waveguide layer. The projections of the plurality of second carrier depletion regions on the upper surface of the planar waveguide layer coincide with the projection of the first carrier depletion region on the upper surface of the planar waveguide layer. It should be understood that the coincidence of projection A and projection B described in the present application means that projection A basically falls within projection B.

[0013] Optionally, the sum of the spacing between two adjacent waveguides among the plurality of waveguide blocks and the width of any one of the waveguide blocks along the first direction is less than 500 nanometers. This can improve the wavelength range applicable to the PN junction.

[0014] Optionally, the width of the waveguide block along the first direction is less than 250 nanometers. This can reduce the proportion of the ineffective region in the PN junction, thereby preferably reducing the optical loss of the PN junction.

[0015] Specifically, the material of the first waveguide region and / or the second waveguide region includes silicon or III-V group materials.

[0016] In a specific implementation, each of the plurality of second carrier depletion regions is in an S shape. This can ensure a large coincidence degree between the carrier depletion region and the optical mode field, and improve the modulation efficiency of the PN junction.

[0017] In a specific implementation, the first carrier depletion region and the plurality of second carrier depletion regions are realized by inclined angle ion implantation doping. Adopting this method can reduce the manufacturing complexity and cost.

[0018] It should be understood that the first direction can be a straight line or a ring. That is, the plurality of waveguide blocks are arranged at intervals in a straight line or arranged at intervals in a ring.

[0019] In a third aspect, an embodiment of the present application provides a Mach-Zehnder modulator. The modulator includes a plurality of waveguides, two PN junctions as shown in the second aspect or any of its specific or optional implementation manners, two couplers, and electrodes. Wherein, both ends of each of the two PN junctions are respectively connected through a plurality of waveguides and two couplers; one of the two couplers includes an input end of the modulator, and the other of the two couplers includes an output end of the modulator; the electrodes are used to apply a voltage to the two PN junction modulators to change the phase of the light input to the two PN junctions.

[0020] In a specific implementation, the number of electrodes is two, which are respectively connected to a negative driving signal and a positive driving signal. In another implementation, the number of electrodes is five, which are respectively grounded, connected to a negative driving signal, grounded, connected to a positive driving signal, and grounded.

[0021] In a fourth aspect, an embodiment of the present application discloses a microring modulator. The microring modulator includes a PN junction as shown in the second aspect or any of its specific or optional implementation manners and two straight waveguides. Wherein, the plurality of waveguide blocks of the PN junction are arranged at intervals in a ring. The two straight waveguides are respectively located on both sides of the PN junction and the two straight waveguides are substantially parallel to each other.

[0022] In summary, the PN junction or the method for preparing the PN junction provided by the present application realizes a structure in which waveguide arrangements at intervals are disposed on a planar waveguide block, and has low optical loss. In addition, the PN junction provides a carrier depletion region similar to an S shape, providing good modulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In combination with the accompanying drawings and with reference to the following detailed description, the features, advantages and other aspects of each implementation manner of the present application will become more obvious. Several implementation manners of the present disclosure are shown herein in an exemplary rather than restrictive manner, in the drawings:

[0024] Figure 1 is a schematic structural diagram of a PN junction;

[0025] Figure 2 is a schematic diagram of a method for preparing a PN junction provided by an embodiment of the present application;

[0026] Figure 3 is Figure 2Schematic diagram of the ion implantation direction shown;

[0027] Figure 4 Top view of a possible PN junction provided by an embodiment of the present application;

[0028] Figure 5 is Figure 4 Cross-sectional view of the PN junction shown;

[0029] Figure 6 Schematic diagram of the simulation performance of a possible PN junction provided by the present application;

[0030] Figure 7 Schematic diagram of another method for preparing a PN junction provided by an embodiment of the present application;

[0031] Figure 8 Schematic diagram of another possible PN junction provided by an embodiment of the present application;

[0032] Figure 9 is Figure 8 Top view of the PN junction shown;

[0033] Figure 10 is Figure 9 First cross-sectional view of the PN junction shown;

[0034] Figure 11 is Figure 9 Second cross-sectional view of the PN junction shown;

[0035] Figure 12 Schematic diagram of another PN junction provided by an embodiment of the present application;

[0036] Figure 13 Schematic diagram of the structure of a modulator provided by an embodiment of the present application;

[0037] Figure 14 Schematic diagram of the structure of another modulator provided by an embodiment of the present application;

[0038] Figure 15 Top view of another possible PN junction provided by an embodiment of the present application;

[0039] Figure 16 is Figure 15 Cross-sectional view of the PN junction shown. Detailed implementation manners

[0040] The device forms and service scenarios described in the embodiments of the present application are for more clearly illustrating the technical solutions of the embodiments of the present invention, and do not constitute a limitation on the technical solutions provided by the embodiments of the present invention. Those of ordinary skill in the art know that with the evolution of device forms and the emergence of new service scenarios, the technical solutions provided by the embodiments of the present application are equally applicable to similar technical problems.

[0041] The technical solution proposed in this application can be applied to scenarios where optical signals are used for data communication. For example, router networks, telecommunications Ethernet networks, optical access networks, or data center networks, etc. Specifically, the technical solution proposed in this application can be used in the transmitting-side devices corresponding to any of the above networks.

[0042] It should be noted that the terms "first", "second", etc. in this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such ordinal numbers can be interchanged under appropriate circumstances so that the embodiments described here can be implemented in an order not described in this application. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Unless otherwise specified, the same or similar technical descriptions provided in the preparation method embodiments can also be applied to the device embodiments. Vice versa.

[0043] It should be understood that the number of masks and the number of waveguide blocks included in the grating waveguide in the drawings of this application are only examples. The actual design can be carried out according to specific requirements, and this application does not make any limitations in this regard.

[0044] Unless otherwise specified, the specific descriptions of some technical features in one embodiment can also be applied to explain the corresponding technical features mentioned in other embodiments. For example, the examples of the materials of the waveguides. Another example is the function, name, or the relationship of the carrier depletion regions in different regions of the carrier depletion region. In addition, in order to more clearly reflect the relationship between the components in different embodiments, this application uses the same or similar reference numerals to represent the components with the same or similar functions in different embodiments. It should be understood that the two ion types in this application can be replaced with each other. Specifically, the region doped with P-type ions can be replaced with the region doped with N-type ions; correspondingly, the region doped with N-type ions can be replaced with the region doped with P-type ions.

[0045] The optical modulator is an important device in the optical communication system and is used to convert an electrical signal into an optical signal. The PN junction is an important part of the optical modulator. Figure 1 It is a schematic structural diagram of a PN junction. As Figure 1As shown, the PN junction 100 includes a P-type doped region 102, an N-type implanted region 101, and a carrier depletion region 103. Among them, the P-type doped region 102 includes a planar waveguide region 102-1 and a ridge waveguide region 102-2. Similarly, the N-type doped region 101 includes a planar waveguide region 101-1 and a ridge waveguide region 101-2. It should be understood that the planar waveguide region 102-1 and the planar waveguide region 101-1 can also be referred to as the planar waveguide regions of the PN junction 100, and the ridge waveguide region 102-2 and the waveguide region 101-2 can also be referred to as the ridge waveguide regions of the PN junction.

[0046] Figure 1 A schematic diagram of the light propagating along the waveguide direction (reference numeral 204) and a schematic diagram of the optical mode field (reference numeral 205) are given. It should be understood that the optical mode field refers to the electric field distribution of the light stably transmitted in the waveguide. When the light propagates in the PN junction 100 along the direction 204, the phase of the light will change due to the different voltage values applied to the PN junction 100, thereby realizing the modulation of the light. The modulation efficiency and the optical loss are two important performance parameters of the PN junction. The modulation efficiency of the PN junction is related to the overlapping size of the carrier depletion region and the optical mode field. Generally, if the overlapping degree of the carrier depletion region and the optical mode field is high, then the range of the modulation phase of the PN junction is larger, and thus the modulation efficiency is higher. For the PN junction 100 as Figure 1 shown, along the light propagation direction 204, the coincidence of the carrier depletion region 103 and the optical mode field 205 is small (equal to the cross-sectional size of the carrier depletion region). Therefore, Figure 1 the modulation efficiency of the PN junction shown is low. The optical loss refers to the degree of reduction of the light transmission power in the PN junction. As Figure 1 shown, during the light propagation process, in addition to passing through the carrier depletion region 103 that plays a modulation role, it also passes through part of the P-type doped region and the N-type doped region, and its power will decrease, that is, the optical loss is large.

[0047] Therefore, the present application provides a new method for preparing a PN junction, a PN junction, and a modulator. Through the grating waveguides arranged at intervals, the method for preparing a PN junction and the PN junction provided by the present application can effectively improve the modulation efficiency of the PN junction and reduce the optical loss. Correspondingly, the modulator using the PN junction disclosed in the present application has a great improvement in modulation efficiency and loss.

[0048] Figure 2 It is a schematic diagram of a method for preparing a PN junction provided by an embodiment of the present application. As Figure 2 shown, the method 300 for preparing a PN junction includes three steps (301, 303, and 305). It should be understood that the order of steps 303 and 305 can be interchanged.

[0049] Step 301: Using a set of masks 500 as a barrier, etch the optical waveguide along the first direction to form a grating waveguide structure on the surface of the optical waveguide;

[0050] Specifically, the first direction is Figure 2 the direction indicated by the z-axis arrow shown. The set of masks 500 is a plurality of masks arranged at intervals. Specifically, these masks are arranged at intervals along Figure 2 the direction indicated by the y-axis arrow shown. Correspondingly, when the etching of the optical waveguide along the first direction is completed, a planar waveguide layer 401 and a grating waveguide structure 402 that is not etched due to the mask barrier are formed. Similar to the arrangement of the masks, the grating waveguide structure 402 includes a plurality of waveguide blocks arranged at intervals. The interval of the waveguide blocks is determined by the interval of the set of masks 500. As Figure 2 shown, the thickness of the grating waveguide structure 402 is less than the thickness of the optical waveguide 400. It should be understood that after step 301, the optical waveguide 400 includes a planar waveguide layer 401 and a plurality of waveguide blocks (i.e., grating waveguide structure) 402 arranged at intervals. For simplicity of subsequent description, the optical waveguide 400 after step 301 is abbreviated as the etched optical waveguide 400. The waveguide material includes but is not limited to silicon, gallium arsenide, or indium phosphide and other group III-V materials.

[0051] It should be noted that the grating waveguide can also be referred to as a grating-shaped waveguide, which refers to a set of waveguide blocks arranged at intervals along a predetermined direction in this application.

[0052] Step 303: Continuing to use a set of masks 500 as a barrier, inject P-type ions into the etched optical waveguide 400 in the first injection direction 601. The angle between the first injection direction 601 and the first direction (such as Figure 2 the z-axis direction shown) is between (0, 90) degrees, the angle between the first injection direction 601 and the arrangement direction of the plurality of waveguide blocks is between (0, 90) or (90, 180) degrees, and the angle between the first injection direction 601 and the second direction is between (0, 90) or (90, 180) degrees. The second direction is a direction perpendicular to both the first direction and the arrangement direction of the plurality of waveguide blocks;

[0053] Exemplarily, as Figure 2 shown, the second direction, the arrangement direction of the plurality of waveguide blocks, and the first direction are represented by the x, y, and z axes respectively. In this embodiment, the x, y, and z axes are perpendicular to each other in pairs, and the directions are the horizontal direction to the right, the light propagation direction, and the etching direction (i.e., the first direction) respectively. It should be understood that this direction schematic is only for explaining the relative position relationship between the first injection direction 601 and the etched optical waveguide 400, and does not limit the method of preparing the PN junction or the PN structure obtained by this preparation method. For example, the light propagation direction can be along the reverse direction of the y-axis.

[0054] Figure 3 ForFigure 2 Schematic diagram of the ion implantation direction as shown. As Figure 3 shown, the implantation direction 601 forms an angle with each of the three axes respectively. It should be noted that the angle mentioned in this application refers to the angle formed between two directed lines (vectors). Specifically, the implantation direction 601 forms an angle 601-1 with the z-axis, an angle 601-3 with the y-axis, and an angle 601-2 with the x-axis. In this embodiment, the first implantation direction 601 needs to satisfy the following conditions to achieve P-type ion implantation at an inclined angle: the angle 601-1 is between (0, 90) degrees, and both the angles 601-3 and 601-2 satisfy being between (0, 90) or (90, 180) degrees. It should be understood that in Figure 3 , an example where the angle 601-3 is between (90, 180) degrees and the angle 601-2 is between (0, 90) degrees. This application does not limit the specific angles used during preparation, as long as the conditions for the aforementioned inclined angle implantation are met.

[0055] Generally, the angle 601-1 is between (10, 80) degrees to form a carrier depletion region with a relatively large overlapping area with the optical field after all preparation steps are completed. For example, when the angle 601-1 is 45 degrees, a PN junction with a relatively high modulation efficiency can be formed. It should be understood that the selection of the first implantation direction angle depends on factors such as the spacing, height, width of the waveguide block, and / or the mask thickness, etc.

[0056] Step 305: Continuing to use a set of masks 500 as a barrier, injecting N-type ions into the etched optical waveguide 400 in the second implantation direction 602 to form a carrier depletion region of the PN junction at the junction of the region where the P-type ions are located and the region where the N-type ions are located. The angle between the second implantation direction 602 and the first direction (such as Figure 2 the z direction shown) is between (0, 90) degrees, the angle between the second implantation direction 602 and the arrangement direction of the multiple waveguide blocks is between (90, 180) or (0, 90) degrees, and the angle between the first implantation direction 602 and the second direction (such as Figure 2 the x direction shown) is between (90, 180) or (0, 90) degrees.

[0057] Taking Figure 3 as an example to illustrate the second implantation direction 602 and its relationship with the first implantation direction 601. As Figure 3As shown, the injection direction 602 forms an angle with each of the three axes. Specifically, the injection direction 602 forms an angle 602-1 with the z-axis, an angle 602-3 with the y-axis, and an angle 602-2 with the x-axis. In this embodiment, the first injection direction 602 needs to satisfy the following conditions to achieve N-type ion implantation at an inclined angle: the angle 602-1 is between (0, 90) degrees, and both the angles 602-3 and 602-2 satisfy being between (90, 180) or (0, 90) degrees. It should be understood that in Figure 3 there is an example where the angle 602-3 is between (0, 90) and the angle 602-2 is between (90, 180) degrees. This application does not limit the specific angles used in the preparation, as long as the conditions for the aforementioned inclined angle implantation are satisfied.

[0058] It should be noted that in this example, the angles between the second injection direction 602 and the x-axis and the first injection direction 601 and the x-axis are respectively between (90, 180) degrees and between (0, 90) degrees. In other examples, their relationship may be reversed, that is, they may be between (0, 90) degrees and between (90, 180) degrees respectively. That is to say, these two angles follow the relationship that one is an acute angle and the other is an obtuse angle. The angles between the second injection direction 602 and the y-axis and the first injection direction 601 and the y-axis also have a similar relationship, which will not be elaborated here.

[0059] Generally, similar to the angle 601-1, the angle 602-1 is between (10, 80) degrees to form a carrier depletion region with a relatively large overlapping area with the optical field after all the preparation steps are completed. For example, the angle 602-1 is 45 degrees to form a PN junction with a relatively high modulation efficiency. It should also be noted that in order to form a carrier depletion region with better performance, the second injection direction 602 and the first injection direction 601 present a certain relationship, that is: the angle between the second injection direction 602 and the axisymmetric direction of the first injection direction 601 along the first direction is less than 10 degrees. The advantage of doing this is that a PN junction carrier depletion region with a relatively high degree of coincidence with the optical field can be formed, thereby obtaining a better modulation efficiency. As Figure 3 shown, the direction 603 is the axisymmetric direction of the first injection direction 601 along the z direction. The angle between the second injection direction 602 and the axisymmetric direction of the first injection direction 601 along the first direction being less than 10 degrees can be understood as the angle 603-1 between the second injection direction 602 and the direction 603 being less than 10 degrees. For example, 5 degrees; or for another example, the second injection direction 602 and the first injection direction 601 are in an axisymmetric relationship.

[0060] It should also be noted that the carrier depletion region can also be referred to as an effective modulation region, a carrier depletion region, a PN junction barrier region, or a PN junction blocking layer, etc. This application does not limit this.

[0061] After the above three preparation steps, a PN junction with better modulation efficiency and lower optical loss can be obtained. The following describes the PN junction prepared by the Figure 2 shown preparation steps with more examples of the drawings. Figure 4 FIG. is a top view of a possible PN junction provided by an embodiment of the present application. Specifically, the PN junction 700 includes a planar waveguide layer 401, a grating waveguide structure 402, and a carrier depletion region (not shown in the figure). The spaced arrangement of the multiple waveguides of the grating waveguide structure 402 reduces the optical loss brought by light when passing through the PN junction, and improves the corresponding performance of the PN junction. The planar waveguide layer 401 includes a P-type doping region 401-1 and an N-type doping region 401-2. Similarly, each of the multiple waveguides included in the grating waveguide structure 402 also includes a P-type doping region and an N-type doping region, and the reference numerals in Figure 4 are 402-1 and 402-2 respectively. It should be understood that the P-type doping region can also be referred to as a P region, a P ion doping region, a P-type ion region, or a region where P-type ions are located, etc., and the present application does not limit this name. Similarly, the N-type doping region can also be referred to as an N region, an N ion doping region, an N-type ion region, or a region where N-type ions are located, etc. It should be noted that in the planar waveguide layer, both the P region and the N region have multiple protruding regions and are alternately arranged along the arrangement direction of the multiple waveguides included in the grating waveguide structure 402. Inside the grating waveguide structure 402, the distribution of the P region and the N region is similar to the distribution of the P region and the N region of the planar layer. It should be noted that the carrier depletion region ( Figure 4 not shown in the figure) is located at the junction of the P region and the N region. As shown in the top view of the example in Figure 4 , the carrier depletion region has a distribution similar to an S shape connected end to end in the planar waveguide layer; it has a distribution similar to an S shape in each waveguide of the grating waveguide structure 402. It should be noted that the cross-sectional shape of the carrier depletion region in the planar waveguide layer in any plane parallel to the x-axis and the y-axis is similar to the Figure 4 shown top view. Similarly, the cross-sectional shape of the carrier depletion region in the grating waveguide structure in the plane parallel to the x-axis and the y-axis is similar to the Figure 4 shown top view. It should be understood that Figure 4 is only a schematic diagram, and other deformations of a similar S shape are also within the scope of the present application. In addition, the present application Figures 8 - 9 also gives other possible examples, which can be seen in the relevant drawings and descriptions and will not be elaborated here.

[0062] Figure 5 is Figure 4 a cross-sectional schematic diagram of the shown PN junction. To illustrate the performance of the PN junction, Figure 5 a schematic diagram (205) of the optical field distribution is shown. Specifically, Figure 5 is a cross-sectional schematic diagram of the PN junction 700 taken along the Figure 4 shown A-A' position. As shown inFigure 5 As shown, the PN junction 700 includes a planar waveguide layer 401 (401-1 and 401-2), a grating waveguide structure 402 (402-1 and 402-2), and a carrier depletion region 403. For the description of the planar waveguide layer 401 and the grating waveguide structure 402, please refer to Figures 2 - 4 , which will not be elaborated here. Figure 6 It is a schematic diagram of the simulation performance of a possible PN junction provided by this application. Figure 6 It is a partial simulation schematic diagram of the PN junction, including one waveguide of multiple waveguides of a part of the planar waveguide layer 401 and the grating waveguide layer 402, and the carrier depletion region 403 of this waveguide. As Figure 6 shown, the carrier depletion region 403 occupies more than 50% of this waveguide, that is to say, the effective area (modulation region) of this waveguide is larger. In addition, looking along the optical field direction, the ineffective area (that is, the non-carrier depletion region) is smaller.

[0063] Combined with Figure 4 the top view of the carrier depletion region, Figure 5 the cross-sectional view, and Figure 6 the simulation performance diagram in Figure 4 , it can be seen that Figure 5 the projection of the carrier depletion region shown in and the optical field have a large overlapping area at the interface shown in , which can better improve the modulation efficiency of the PN junction.

[0064] It should be understood that the modulation efficiency not only depends on the overlapping degree of the carrier depletion region and the optical field at the Figure 5 cross-section shown in , but also depends on the overlapping degree of the two in the light propagation direction. Combined with Figure 4 and Figure 5 , it can be seen that the PN junction fabricated by using the Figure 2 shown PN junction fabrication method also has a good overlapping degree with the optical mode field in the light propagation direction. In addition, the ineffective area of this PN junction is small and the optical loss is also low.

[0065] In summary, using the Figure 2 shown PN junction fabrication method can fabricate a PN junction with low optical loss and good modulation efficiency. In addition, compared with the method of separately performing optical waveguide etching and ion doping through multiple different masks, Figure 2 the embodiment shown in only uses one mask to complete optical waveguide etching and doping simultaneously, with a simple process and low implementation difficulty, which is beneficial to reducing the fabrication cost of the PN junction. Performing multiple masks will introduce a certain alignment error, resulting in the shift of the positions of the P region and the N region, affecting the modulation efficiency of the PN junction. Through simulation, it is found that the modulation efficiency of the PN junction may be reduced by more than 40%, which greatly affects the processing yield of the PN junction (that is, the proportion of the fabricated PN junctions that meet the expected performance, also known as the yield). Figure 2The PN junction preparation method shown only uses one mask, avoiding the introduction of alignment errors, thereby effectively improving the yield and reducing the preparation cost of the PN junction.

[0066] Figure 7 It is a schematic diagram of another PN junction preparation method provided by an embodiment of the present application. As Figure 7 shown, the preparation method 800 includes five steps, namely steps 301, 802, 303, 804, and 305. Steps 301, 303, and 305 are basically the same as Figure 2 three steps therein, and for specific reference, see Figure 2 the relevant description thereof, which will not be elaborated here. Step 802 is to place the mask 901 above the doped N-type ion region 401-2 as shown in Figure 5 before P-type ion doping is performed on the etched optical waveguide 400. Similarly, step 805 is to place the mask 902 above the doped P-type ion region 401-1 as shown in Figure 5 before N-type ion doping is performed on the etched optical waveguide 400. The advantage of placing these two masks (901 and 902) is that it can reduce the ion doping into non-corresponding doping regions during the ion doping process. For example, the mask 901 can prevent P-type ion doping from entering the N-type doping region 401-2. Correspondingly, the mask 902 can prevent N-type ion doping from entering the P-type doping region 401-1. Doing so can further improve the yield of the PN junction and further reduce the manufacturing cost.

[0067] Figure 7 The beneficial effects brought by the PN junction preparation method shown are the same as those of the PN junction preparation method shown in Figure 2 , that is, the modulation efficiency and optical loss performance of the fabricated PN junction are also better improved, which will not be elaborated here. In addition, Figure 7 the preparation method shown can further improve the yield of the PN junction.

[0068] Figure 8 It is another possible PN junction structure diagram provided by an embodiment of the present application. As Figure 8 shown, the PN junction 900 includes a P-type doped region 901 of the planar waveguide layer, an N-type doped region 902 of the planar waveguide layer, a P-type doped region 903 of the grating waveguide layer, an N-type doped region 904 of the grating waveguide layer, and a carrier depletion region (not shown in the figure). Specifically, the PN junction 900 is a two-layer structure, and through the existing preparation process, or the PN junction preparation method shown in Figure 2 or Figure 7 , the structure shown in Figure 8 is realized. The grating waveguide layer includes a plurality of waveguides arranged along the light propagation direction. The junction of the P-type doped region and the N-type doped region is the carrier depletion region. The following combines the attached Figures 9 - 11, further description of the carrier depletion region.

[0069] Figure 9 is Figure 8 a top view of the PN junction shown. As Figure 9 shown, the projection of the P-type doping region 903 of the grating waveguide layer on the surface of the planar waveguide layer coincides with the projection of the P-type doping region 901 of the planar waveguide layer on the surface of the planar waveguide layer. It should be noted that in this application, coincidence means that the smaller region in two projection regions on the same plane basically falls within the larger region. Coincidence can also be referred to as substantially coincident. It should be understood that the relationship between the two P-type doping regions (903 and 901) can also be described as: the projection of the P-type doping region 903 of the grating waveguide layer on the surface of the planar waveguide layer falls within the projection of the P-type doping region 901 of the planar waveguide layer on the surface of the planar waveguide layer. Similarly, the two N-type doping regions (904 and 902) have a similar relationship. Specifically, the projection of the N-type doping region 904 of the grating waveguide layer on the surface of the planar waveguide layer coincides with the projection of the N-type doping region 902 of the planar waveguide layer on the surface of the planar waveguide layer. Similarly, the projection of the carrier depletion region formed in the grating waveguide layer on the upper surface of the planar waveguide layer coincides with the projection of the carrier depletion region formed in the planar waveguide layer on the upper surface of the planar waveguide layer.

[0070] It should be noted that due to the limitations of the manufacturing process, the same type of doping regions may not be completely coincident, and there may be a small amount of non-coincident regions at the edges. Similarly, the carrier depletion regions in the upper and lower layers may not be completely coincident, and there may be non-coincident parts due to doping processes or other manufacturing errors. It should be understood that the situation of having a small amount of non-coincident regions or non-fully overlapping parts also belongs to the coincidence relationship described in this application.

[0071] As Figure 9As shown, d’ is an example of the distance between two adjacent waveguides. In this example, d’ is the sum of the width d of the waveguide in the optical propagation direction and the gap size between two adjacent waveguides, which is also called the period. Generally, the period d’ needs to be less than the wavelength passing through the grating waveguide. Usually, the distance between two adjacent waveguides in the grating waveguide layer is less than or equal to 1.6 micrometers (μm), for example, d’ < 1.6 μm. In a possible implementation, the distance between two adjacent waveguides in the grating waveguide layer is less than 500 nanometers (nm), for example, d’ < 500 nm. Such a design can cover a relatively wide wavelength range and expand the applicable scenarios of the PN junction. Usually, the width of a waveguide in the grating waveguide layer in the optical propagation direction is less than or equal to 800 nm, that is, d ≤ 800 nm. In a possible implementation, d is half of d’, for example: if d’ is 500 nm, then d is 250 nm. Such a design can balance the ratio between the carrier dissipation region and the gap between two adjacent waveguides, so as to minimize optical loss while ensuring the modulation efficiency. It should be understood that the distance between two adjacent waveguides can be measured by other methods, such as measuring the distance between the central axes of the two waveguides or other methods. Regarding this, this application does not make any limitations.

[0072] As Figure 9 shown, both the P-type doped region 901 and the N-type doped region 902 have protruding regions, and these protruding regions are arranged alternately in the optical propagation direction. The junction between the two doped regions is the carrier depletion region (not shown in the figure). Similar Figure 4 , Figure 9 to the junction shown can also be in an S-shaped distribution. Depending on the width of the waveguide block on the grating waveguide region in the optical propagation direction, the junction can also be in a straight-line distribution or a distribution similar to a straight line. Compared with the latter, the optical field of the carrier depletion region in the S-shaped distribution has a greater overlap, and the modulation efficiency may be relatively higher. However, compared with the prior art, both distribution forms of the carrier depletion region have better improvements in modulation efficiency. It should be understood that Figure 9 only the schematic diagram of the junction region is given, and the form of this junction region can also be replaced with the form shown in Figure 4 .

[0073] Figure 10 is Figure 9 the first cross-sectional view of the PN junction shown. Figure 11 is Figure 9 the second cross-sectional view of the PN junction shown. Specifically, Figure 10 and Figure 11 are cross-sectional views along the B-B’ position and the C-C’ position respectively. For what has been described in Figures 8 - 9The parts that appear, namely 901 - 904, will not be elaborated here. The P - type doped region 1001 includes the P - type doped region 901 of the planar waveguide layer and the P - type doped region 903 of the grating waveguide layer. The N - type doped region 1002 includes the N - type doped region 902 of the planar waveguide layer and the P - type doped region 904 of the grating waveguide layer. It should be understood that the P - type doped region 1001 and the N - type doped region 1002 are formed by ion doping on a piece of waveguide. The division of the figures in this application is only for describing the different characteristics of each region.

[0074] Figure 10 and Figure 11 show schematic diagrams of the carrier depletion regions at two different cross - sectional positions. Among them, Figure 10 the shown carrier depletion region 1003 is closer to the N - type doped region, Figure 11 and the cross - sectional area of the shown carrier depletion region 1004 is the largest. Combining Figures 9 - 11 it can be seen that the coincidence degree of the carrier depletion region along the light propagation direction and the optical mode field is relatively high. Therefore, Figure 9 the modulation efficiency of the shown PN junction is relatively high. In addition, the design of the grating waveguide structure arranged at intervals results in a lower optical loss of the PN junction.

[0075] It should be understood that Figure 8 the shown grating waveguide structure is arranged along a certain straight - line direction. In a specific implementation, the grating waveguide structure can also be arranged in an annular interval. Specifically, refer to Figures 15 - 16 for the relevant description and it will not be elaborated here.

[0076] Figure 12 This is a schematic diagram of another PN structure provided by an embodiment of the present application. As Figure 12 shown, the PN junction 1100 includes the PN junction 700 as Figure 4 shown, a P + doped region 1101, and an N + doped region 1102. Among them, the ion concentration of the P + doped region is higher than that of the P - type doped region in the PN junction 700 and is adjacent to the P - type doped region in the PN junction 700, and is used for electrode connection. Similarly, the ion concentration of the N + doped region is higher than that of the N - type doped region in the PN junction 700 and is adjacent to the N - type doped region in the PN junction 700, and is used for electrode connection. It should be understood that the PN junction 700 in this embodiment can be replaced by the PN junctions in the aforementioned other embodiments, such as Figure 8 the PN junction shown. The beneficial effects of the PN junction in this embodiment are similar to those of the aforementioned embodiments and will not be elaborated here.

[0077] Figure 13 This is a schematic diagram of the structure of a modulator provided by an embodiment of the present application. As Figure 13As shown, the modulator 1200 is a Mach-Zehnder modulator, which includes two couplers 1201-A and 1201-B, two PN junctions (1100-A and 1100-B), multiple electrodes (not shown in the figure), and multiple sections of waveguides (not labeled in the figure). Specifically, one end of the coupler 1201-A is the input end of the modulator, and the other two ends of the coupler 1201-A are respectively coupled to the PN junction 1100-A and the PN junction 1100-B through waveguides. The PN junction 1100-A and the PN junction 1100-B are coupled to the coupler 1201-B through waveguides, and the coupler 1201-B provides the output end of the modulator. Among them, the two PN junctions are Figure 12 the PN junctions 1100 shown. By applying a reverse bias voltage to the two PN junctions through the electrodes, the light split by the coupler 1201-A and entering the two PN junctions can be modulated to obtain two optical signals. Then, these two optical signals are combined by the coupler 1201-B and output.

[0078] In a possible implementation, the number of the multiple electrodes is two, which are respectively used to access the negative driving signal and the positive driving signal. For example, the two electrodes can be located on both sides of the two PN junctions. In another implementation, the number of the multiple electrodes is five, which are respectively used for grounding, accessing the negative driving signal, grounding, accessing the positive driving signal, and grounding. For example, four of the five electrodes can be distributed on both sides of the two PN junctions, and the other electrode is located between the two electrodes. It should be noted that the relative positions of the electrodes and the PN junctions described in this embodiment are only examples, and the electrodes can be placed in other ways in specific implementations.

[0079] Figure 14 This is a schematic structural diagram of another modulator provided by the embodiment of the present application. As Figure 14 shown, the modulator 1300 is a microring modulator, which includes a ring waveguide type PN junction 1400 and two waveguides (1301 and 1302). Specifically, the two waveguides 1301 and 1302 are respectively arranged on both sides of the ring waveguide type PN junction 1400, and the two waveguides are parallel. The two waveguides form four ports of the modulator, and its working principle is well-known common sense to those skilled in the art and will not be elaborated here. It should be understood that the basic parallel relationship in the present application includes a strict parallel relationship or a parallel relationship with a slight error but does not affect the performance of the modulator. This error may be introduced due to the manufacturing process or other reasons.

[0080] Next, in combination with the attached Figures 15 - 16 , the ring waveguide type PN junction 1400 will be further described. Figure 15 This is a top view of another possible PN junction provided by the embodiment of the present application. Figure 16 It is Figure 15 a cross-sectional view of the PN junction structure shown. Specifically, Figure 16 along the D-D' direction forFigure 15 Cross-sectional view of the PN junction shown

[0081] As Figure 15 shown, the top view schematic of the ring waveguide type PN junction 1400 is similar to the top view schematic of the PN junction shown in Figure 4 or Figure 8 shown, and is divided into two layers (a planar waveguide layer and a grating-like waveguide layer with multiple waveguide blocks arranged at intervals), and the carrier depletion region has a similar S-shaped distribution or a similar linear distribution (not shown in the figure). Different from the aforementioned two PN junction embodiments, Figure 15 the waveguides arranged at intervals in the upper layer of the ring waveguide type PN junction 1400 shown are arranged in a ring shape. The ring shape in the present application can be a circular ring shape, an elliptical shape, a racetrack shape, etc. The present application does not limit this. It should be noted that the P-type doping region and the N-type doping region of the ring waveguide type PN junction 1400 are also similar. As Figure 16 shown, the ring waveguide type PN junction 1400 includes a P-type doping region 1401, an N-type doping region 1402, and a carrier depletion region (1403-A and 1403-B). Specifically, the P-type doping region 1401 is divided into two layers. In the cross-sectional view shown in Figure 16 the lower layer includes 1401-1 and 1401-3, and the upper layer includes 1401-2 and 1401-4. Similarly, the N-type doping region 1402 is divided into two layers. In the cross-sectional view, the lower layer includes 1402-1, and the upper layer includes 1402-2. Figures 15 - 16 The ring waveguide type PN junction shown can be realized by a conventional vertical ion doping process, and its optical loss and modulation efficiency performance are better than those of the PN junction shown in Figure 1 shown.

[0082] It should be understood that Figure 15 the planar waveguide layer shown is circular. In actual implementation, the planar waveguide layer can also be of other structures, such as square or elliptical, etc. The present application does not limit this.

[0083] Exemplarily, the regions (P+ doping region and N+ doping region) of the ring waveguide type PN junction 1400 for connecting two electrodes can be respectively arranged on 1402-1 (i.e., above the planar waveguide layer and within the ring waveguide) and 1401 (i.e., above the planar waveguide layer and outside the ring waveguide). The present application does not limit the specific design of the electrodes.

[0084] It should be noted that the above two types of modulators can be used as optical switches or optical filters, and the present application does not limit this.

[0085] Finally, it should be noted that the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims described above.

Claims

1. A method for preparing a PN junction, characterized in that, the method comprises: using a set of first masks as a barrier, etching an optical waveguide along a first direction to form a grating waveguide structure on the surface of the optical waveguide, the set of first masks being a plurality of masks arranged at intervals, the grating waveguide structure comprising a plurality of waveguide blocks arranged at intervals and the thickness of the grating waveguide structure being less than the thickness of the optical waveguide; using the set of first masks as a barrier, injecting P-type ions into the optical waveguide in a first injection direction, the angle between the first injection direction and the first direction being between (10, 80) degrees, the angle between the first injection direction and the arrangement direction of the plurality of masks being between (0, 90) or (90, 180) degrees, and the angle between the first injection direction and a second direction being between (0, 90) or (90, 180) degrees, the second direction being perpendicular to both the arrangement direction of the plurality of masks and the first direction; using the set of first masks as a barrier, injecting N-type ions into the optical waveguide in a second injection direction to form a carrier depletion region of the PN junction at the junction of the region where the P-type ions are located and the region where the N-type ions are located, the angle between the second injection direction and the first direction being between (10, 80) degrees, wherein: when the angle between the first injection direction and the arrangement direction of the plurality of masks is between (0, 90) degrees, the angle between the second injection direction and the arrangement direction of the plurality of masks is between (90, 180) degrees, or when the angle between the first injection direction and the arrangement direction of the plurality of masks is between (90, 180) degrees, the angle between the second injection direction and the arrangement direction of the plurality of masks is between (0, 90) degrees; when the angle between the first injection direction and the second direction is between (0, 90) degrees, the angle between the second injection direction and the second direction is between (90, 180) degrees, or when the angle between the first injection direction and the second direction is between (90, 180) degrees, the angle between the second injection direction and the second direction is between (0, 90) degrees.

2. The preparation method according to claim 1, characterized in that, the method further comprises: before injecting P-type ions into the optical waveguide in the first injection direction, arranging a second mask on the region where the N-type ions are located.

3. The preparation method according to claim 1, characterized in that, the method further comprises: before injecting N-type ions into the optical waveguide in the second injection direction, arranging a third mask on the region where the P-type ions are located.

4. The preparation method according to any one of claims 1-3, characterized in that, the angle between the second injection direction and the angle of the axisymmetric direction of the first injection direction along the first direction is less than 10 degrees.

5. The preparation method according to any one of claims 1-3, characterized in that, the angle between the first injection direction and the first direction is 45 degrees, and the angle between the second injection direction and the first direction is 45 degrees.

6. A PN junction, characterized in that, The PN junction includes a first waveguide region and a second waveguide region, where: The first waveguide region is disposed on the second waveguide region, and the first waveguide region includes a plurality of third waveguides arranged at intervals in a first direction; The second waveguide region includes a first P-type doped region and a first N-type doped region. The first P-type doped region includes a plurality of first protruding regions, and the first N-type doped region includes a plurality of second protruding regions. The first protruding regions and the second protruding regions are alternately arranged in the first direction. A first carrier depletion region is formed at the junction of the first P-type doped region and the first N-type doped region, and the first carrier depletion region is in an S shape with its head and tail connected in the first direction; Each of the plurality of third waveguides includes a second P-type doped region and a second N-type doped region, and a second carrier depletion region is formed at the junction of the second P-type doped region and the second N-type doped region of each waveguide of the plurality of third waveguides; The projection of the plurality of second P-type doped regions on the upper surface of the second waveguide region coincides with the projection of the first P-type doped region on the upper surface of the second waveguide region, the projection of the plurality of second N-type doped regions on the upper surface of the second waveguide region coincides with the projection of the first N-type doped region on the upper surface of the second waveguide region, and the projection of the plurality of second carrier depletion regions on the upper surface of the second waveguide region coincides with the projection of the first carrier depletion region on the upper surface of the second waveguide region.

7. The PN junction according to claim 6, wherein, the sum of the interval between two adjacent waveguides of the plurality of third waveguides and the width of any one of the plurality of third waveguides in the first direction is less than 500 nanometers.

8. The PN junction according to claim 6, wherein, the width of any one of the plurality of third waveguides in the first direction is less than 250 nanometers.

9. The PN junction according to any one of claims 6-8, wherein, the material of the first waveguide region and / or the second waveguide region includes silicon or III-V group materials.

10. The PN junction according to any one of claims 6-8, wherein, each of the plurality of second carrier depletion regions is in an S shape.

11. The PN junction according to any one of claims 6-8, wherein, the first carrier depletion region and the plurality of second carrier depletion regions are achieved by inclined angle ion implantation doping.

12. The PN junction according to any one of claims 6-8, wherein, the first direction is a straight line or a ring.

13. A Mach-Zehnder modulator, wherein, the Mach-Zehnder modulator includes a plurality of waveguides, two PN junctions according to any one of claims 6-12, two couplers and electrodes, where: Both ends of each PN junction are respectively connected through the plurality of waveguides and the two couplers; One of the two couplers includes the input end of the Mach-Zehnder modulator, and the other of the two couplers includes the output end of the Mach-Zehnder modulator; The electrode is used to apply a voltage to the two PN junctions to change the phase of the light input to the two PN junctions.

14. The Mach-Zehnder modulator according to claim 13, wherein, the number of the electrodes is two, and the two electrodes are respectively connected to a negative driving signal and a positive driving signal.

15. The Mach-Zehnder modulator according to claim 13, wherein, the number of the electrodes is five, and the five electrodes are respectively grounded, connected to a negative driving signal, grounded, connected to a positive driving signal, and grounded.

16. A microring modulator, wherein, the microring modulator includes the PN junction according to any one of claims 6-12 and two straight waveguides, the multiple third waveguides of the PN junction are arranged in a ring at intervals, and the two straight waveguides are respectively located on both sides of the PN junction and the two straight waveguides are parallel to each other.

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