CN113960814B - Silicon light modulator and method of forming the same - Google Patents
Silicon light modulator and method of forming the same Download PDFInfo
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- CN113960814B CN113960814B CN202011390878.2A CN202011390878A CN113960814B CN 113960814 B CN113960814 B CN 113960814B CN 202011390878 A CN202011390878 A CN 202011390878A CN 113960814 B CN113960814 B CN 113960814B
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction in an optical waveguide structure
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
A silicon light modulator and method of forming the same, the method comprising: providing a semiconductor substrate; etching is carried out on the surface of the semiconductor substrate to obtain a ridge structure, wherein the ridge structure is provided with a P-type doped region and an N-type doped region which are adjacent; forming a first electrode and a second electrode, wherein the first electrode comprises a plurality of first extension structures, the plurality of first extension structures cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures, and the plurality of second extension structures cover and are electrically connected with the N-type doped region; wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase. The invention can ensure the stability of characteristic impedance and the stability of microwave refractive index in the axial direction along the ridge structure, reduce impedance mismatch, match refractive index and improve modulation efficiency, thereby improving the bandwidth of the modulator.
Description
Technical Field
The invention relates to the technical field of photoelectricity, in particular to a silicon light modulator and a forming method thereof.
Background
Optical modulators are key devices for high-speed optical communications and are one of the most important integrated optical devices. It is a device that modulates the refractive index, absorption, amplitude or phase of output light by a change in voltage or electric field. The basic theory on which it is based is that various different forms of electro-optic effect, acousto-optic effect, magneto-optic effect, carrier dispersion effect, etc. Silicon optical modulators are compatible with Complementary Metal Oxide Semiconductor (CMOS) fabrication techniques, while possessing both electronic and photonic advantages.
Specifically, the silicon optical modulator can realize high-speed data modulation, is a core device of a silicon optical chip, and generally adopts a carrier depletion modulation mechanism, such as a Mach-Zehnder (MZ) modulator (Modulators) structure of a traveling wave electrode, for realizing high-speed transmission.
In the existing silicon optical modulator, a microwave signal is generally loaded on an input end, and along the direction of a modulation arm, due to the existence of microwave loss and the resistance of a metal signal wire, the driving voltage of the modulator gradually decreases along with the propagation of the microwave signal. However, the existing silicon optical modulator is easy to cause variation of electrical parameters of PN junction in transmission direction, thereby influencing modulation efficiency, device bandwidth and overall performance of the modulator.
What is needed is a method for forming a silicon optical modulator that reduces the variation of electrical parameters of the PN junction of the silicon optical modulator in the axial direction along the ridge structure, and optimizes the modulation efficiency, device bandwidth, and overall performance of the modulator.
Disclosure of Invention
The invention solves the technical problem of providing a silicon optical modulator and a forming method thereof, which can compensate the voltage attenuation of a PN junction region high-speed signal by adjusting the area of an extension structure in the axial direction along a ridge structure, thereby ensuring that the PN junction is uniformly modulated in the transmission process of the high-speed signal along a modulation arm, further ensuring the stability of characteristic impedance and the stability of microwave refractive index, reducing impedance mismatch, matching refractive index and improving modulation efficiency, and further improving the bandwidth of the modulator.
To solve the above technical problems, an embodiment of the present invention provides a method for forming a silicon optical modulator, including: providing a semiconductor substrate; etching is carried out on the surface of the semiconductor substrate to obtain a ridge structure, wherein the ridge structure is provided with a P-type doped region and an N-type doped region which are adjacent; forming a first electrode and a second electrode, wherein the first electrode comprises a plurality of first extension structures, the plurality of first extension structures cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures, and the plurality of second extension structures cover and are electrically connected with the N-type doped region; wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase; the first electrode is one of an anode electrode and a cathode electrode, and the second electrode is the other of the anode electrode and the cathode electrode.
Optionally, the greater the voltage decay ratio of the input signal along the axial direction of the ridge structure, the greater the ratio of the area increase of the first extension structure and the second extension structure.
Optionally, the P-type doped region and the N-type doped region are divided into a plurality of length regions with preset lengths along the axial direction, the plurality of first extension structures respectively correspond to the plurality of length regions of the P-type doped region one by one and cover a part of the P-type doped region in the corresponding length region, and the plurality of second extension structures respectively correspond to the plurality of length regions of the N-type doped region one by one and cover a part of the N-type doped region in the corresponding length region; wherein the length ratio of the first extension structure is gradually increased in each length region along the axial direction of the P-type doped region, and the length ratio of the second extension structure is gradually increased in each length region along the axial direction of the N-type doped region.
Optionally, one or more of the following is satisfied: in each length region of the P-type doped region, the ratio of the length of the first extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal; in each length region of the N-type doped region, the ratio of the length of the second extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal.
Optionally, the first electrode is electrically connected to the third concentration doped region of the P-type doped region, and the second electrode is electrically connected to the third concentration doped region of the N-type doped region.
Optionally, the first extension structure and the second extension structure are both T-shaped structures, and the length of the first end of the T-shaped structure is greater than the length of the second end; the second end of the first extension structure covers and is electrically connected with the P-type doped region, and the second end of the second extension structure covers and is electrically connected with the N-type doped region; the direction of the length is parallel to the axial direction.
Optionally, the silicon optical modulator is a mach-Zeng Degui optical modulator, and the axial direction of the ridge structure is the modulation arm direction of the mach-Zeng Degui optical modulator.
To solve the above technical problem, an embodiment of the present invention provides a silicon optical modulator, including: the ridge structure is obtained by etching the surface of the semiconductor substrate and is provided with a P-type doped region and an N-type doped region which are adjacent to each other; the first electrode comprises a plurality of first extension structures which cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures which cover and are electrically connected with the N-type doped region; wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase; the first electrode is one of an anode electrode and a cathode electrode, and the second electrode is the other of the anode electrode and the cathode electrode.
Optionally, the greater the voltage decay ratio of the input signal along the axial direction of the ridge structure, the greater the ratio of the area increase of the first extension structure and the second extension structure.
Optionally, the P-type doped region and the N-type doped region are divided into a plurality of length regions with preset lengths along the axial direction, the plurality of first extension structures respectively correspond to the plurality of length regions of the P-type doped region one by one and cover a part of the P-type doped region in the corresponding length region, and the plurality of second extension structures respectively correspond to the plurality of length regions of the N-type doped region one by one and cover a part of the N-type doped region in the corresponding length region; wherein the length ratio of the first extension structure is gradually increased in each length region along the axial direction of the P-type doped region, and the length ratio of the second extension structure is gradually increased in each length region along the axial direction of the N-type doped region.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
In the embodiment of the invention, the electrode comprising the extension structure is formed, the extension structure covers and is respectively and electrically connected with the P-type doped region and the N-type doped region, the area of the extension structures is gradually increased along the axial direction of the ridge structure, and the voltage attenuation of the PN junction area high-speed signal can be compensated by adjusting the area of the extension structure along the axial direction of the ridge structure, so that the PN junction is uniformly modulated in the transmission process of the high-speed signal along the modulation arm, the stability of characteristic impedance and the stability of microwave refractive index are further ensured, the impedance mismatch is reduced, the refractive index matching is improved, the modulation efficiency is further improved, and the bandwidth of the modulator is further improved.
Further, the greater the voltage attenuation ratio of the input signal is along the axial direction of the ridge structure, the greater the area increasing ratio of the first extending structure and the second extending structure is, so that the degree of the area increasing of the extending structure can be determined according to the voltage attenuation condition of the input signal, and the scheme in the embodiment of the invention is implemented, the impedance mismatch is reduced, the modulation efficiency is improved, and the bandwidth of the modulator is further improved.
Further, the P-type doped region and the N-type doped region are divided into a plurality of length regions with preset lengths along the axial direction, the plurality of first extension structures are respectively in one-to-one correspondence with the plurality of length regions of the P-type doped region and cover a part of the P-type doped region in the corresponding length region, the plurality of second extension structures are respectively in one-to-one correspondence with the plurality of length regions of the N-type doped region and cover a part of the N-type doped region in the corresponding length region, the length ratio of the first extension structures is gradually increased in each length region along the axial direction of the P-type doped region, and the length ratio of the second extension structures is gradually increased in each length region along the axial direction of the N-type doped region. By adopting the scheme of the embodiment of the invention, the length increase degree of the extension structure can be better controlled by adopting the length period, so that the impedance mismatch is further reduced, the modulation efficiency is improved, and the bandwidth of the modulator is further improved.
Further, the ratio of the length of the first extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal in each length region of the P-type doped region, and the ratio of the length of the second extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal in each length region of the N-type doped region.
Drawings
FIG. 1 is a flow chart of a method of forming a silicon optical modulator in accordance with an embodiment of the present invention;
FIG. 2 is a top view of a silicon optical modulator in accordance with an embodiment of the present invention;
FIG. 3 is a cross-sectional view taken along the cutting line A1-A2 in FIG. 2;
fig. 4 is a top view of another silicon optical modulator in an embodiment of the invention.
Detailed Description
As described above, in the conventional silicon optical modulator, a microwave signal is generally applied to an input terminal, and a driving voltage of the modulator is gradually reduced along a modulation arm direction due to the microwave loss and the existence of the resistance of the metal signal line itself as the microwave signal propagates. However, existing silicon optical modulators have problems of reduced bandwidth and lower modulation efficiency.
The inventor of the invention finds through research that as the driving voltage is reduced, the RC constant of a PN junction region along the transmission direction of the waveguide is also changed, so that the characteristic impedance and the group refractive index of the modulator are changed, the characteristic impedance is changed to cause impedance mismatch, the reflection problem is caused, the eye diagram quality is deteriorated, and the extinction ratio is reduced; the change of the group refractive index can bring group velocity mismatch, the signal can not be effectively modulated, and the bandwidth is reduced; meanwhile, due to gradual reduction of the driving voltage, the capacitance change amount modulated along the axial direction gradually decreases, so that the phase change integral gradually saturates, and the modulation efficiency is reduced.
In the embodiment of the invention, the electrode comprising the extension structure is formed, the extension structure covers and is respectively and electrically connected with the P-type doped region and the N-type doped region, the area of the extension structures is gradually increased along the axial direction of the ridge structure, and the voltage attenuation of the PN junction area high-speed signal can be compensated by adjusting the area of the extension structure along the axial direction of the ridge structure, so that the PN junction is uniformly modulated in the transmission process of the high-speed signal along the modulation arm, the stability of characteristic impedance and the stability of microwave refractive index are further ensured, the impedance mismatch is reduced, the refractive index matching is improved, the modulation efficiency is further improved, and the bandwidth of the modulator is further improved.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a flowchart of a method for forming a silicon optical modulator according to an embodiment of the present invention. The method of forming a silicon optical modulator may include steps S11 to S13:
step S11: providing a semiconductor substrate;
Step S12: etching is carried out on the surface of the semiconductor substrate to obtain a ridge structure, wherein the ridge structure is provided with a P-type doped region and an N-type doped region which are adjacent;
step S13: forming a first electrode and a second electrode, wherein the first electrode comprises a plurality of first extension structures, the plurality of first extension structures cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures, and the plurality of second extension structures cover and are electrically connected with the N-type doped region; wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase.
The first electrode is one of an anode electrode and a cathode electrode, and the second electrode is the other of the anode electrode and the cathode electrode.
The above steps are explained below with reference to fig. 2 and 3.
Referring to fig. 2 and 3 in combination, fig. 2 is a top view of a silicon optical modulator in accordance with an embodiment of the present invention, and fig. 3 is a cross-sectional view along cut line A1-A2 in fig. 2.
In a specific implementation, a semiconductor substrate is provided, and etching is performed on a surface of the semiconductor substrate to obtain the ridge structure 100.
Specifically, the semiconductor substrate may be obtained by forming a silicon material layer on a surface of an initial semiconductor substrate.
Further, the initial semiconductor substrate may be a silicon substrate, or the material of the initial semiconductor substrate may further include germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the initial semiconductor substrate may further be a silicon substrate on an insulator or a germanium substrate on an insulator, or a substrate grown with an epitaxial layer (Epi layer).
Further, the silicon optical modulator may be a Mach-Zeng Degui optical modulator, and the modulation arm of the Mach-Zeng Degui optical modulator may include the ridge structure 100. The axial direction of the ridge structure 100 may be the modulation arm direction of the mach-Zeng Degui optical modulator.
It should be noted that the ridge structure 100 may include a concave portion obtained after etching, and a convex protrusion portion, where the protrusion portion is used to form a ridge optical waveguide after doping ions, so as to transmit an input optical signal.
Further, the ridge structure 100 may be ion implanted to obtain the P-type doped region 110 and the N-type doped region 120 adjacent to each other. The P-doped region 110 and the N-doped region 120 sequentially include a first concentration doped region 111 (121), a second concentration doped region 112 (122), and a third concentration doped region 113 (123) from adjacent positions.
In one embodiment of the present invention, the doping concentration from the first concentration doping region 111 (121) to the third concentration doping region 113 (123) may be sequentially increased.
Specifically, the first concentration doped region 111 of the P-type doped region 110 and the first concentration doped region 121 of the N-type doped region 120 have the smallest doping concentration, which may be also referred to as a lightly doped region. Since the first concentration doped region 111 is adjacent to the first concentration doped region 121, a PN junction may be formed at an adjacent position. In one implementation of the embodiment of the present invention, the width of the first doped region 111 (121) in the etched region may also be referred to as a middle doped ridge margin.
It should be noted that, along the axial direction of the ridge structure, the modulation uniformity of the PN junction is an important factor for ensuring the stability of the characteristic impedance and the stability of the microwave refractive index. However, in the prior art, microwave loss and voltage attenuation exist in the transmission process of the high-speed traveling wave signal, and as the driving voltage is reduced, the RC constant of the PN junction region along the transmission direction of the waveguide is also changed, so that the problems of refractive index mismatch, impedance mismatch and modulation efficiency reduction are caused.
The second concentration doped region 112 of the P-type doped region 110 has a higher doping concentration than the first concentration doped region 111, and the second concentration doped region 122 of the N-type doped region 120 has a higher doping concentration than the first concentration doped region 121, and the second concentration doped region 112 of the P-type doped region 110 and the second concentration doped region 122 of the N-type doped region 120 may be also referred to as middle doped regions.
It should be noted that the second concentration doped region 112 (122) may comprise multiple levels of doping, for example, a first level doping adjacent to the first concentration doped region 111 (121) and a second level doping adjacent to the third concentration doped region. The doping concentration of the first-stage doping may be greater than the doping concentration of the first-stage doping region 111 (121), the doping concentration of the second-stage doping may be greater than the doping concentration of the first-stage doping, and the doping concentration of the second-stage doping may be less than the doping concentration of the third-stage doping region 113 (123), so that in the case of multi-stage doping, the doping concentrations of the first-stage doping region 111 (121), the second-stage doping region 112 (122), and the third-stage doping region 113 (123) increase in order from adjacent positions.
In embodiments of the present invention, by providing the second concentration doped region 112 (122) to include multiple levels of doping, it is possible to help optimize the resistance performance without being limited to only one concentration of doping.
The doping concentration of the third concentration doped region 113 of the P-type doped region 110 is higher than the doping concentration of the second concentration doped region 112, and the doping concentration of the third concentration doped region 123 of the N-type doped region 120 is higher than the doping concentration of the second concentration doped region 122, and the third concentration doped region 113 of the P-type doped region 110 and the third concentration doped region 123 of the N-type doped region 120 may be also referred to as heavy doped regions.
In the silicon optical modulator shown in fig. 3, a first electrode 140 and a second electrode 150 may be further formed, the first electrode being electrically connected to the P-type doped region 110, the second electrode being electrically connected to the N-type doped region, wherein the first electrode 140 is one of an anode electrode and a cathode electrode, and the second electrode 150 is the other of the anode electrode and the cathode electrode.
Further, the first electrode 140 may be electrically connected to the third concentration doped region 113 of the P-type doped region 110. Further, the first electrode 140 may be an anode electrode.
The cathode electrode 150 may be electrically connected to the third concentration doped region 123 of the N-type doped region 120. Further, the second electrode 150 may be a cathode electrode.
In the embodiment of the invention, the anode electrode and the cathode electrode are arranged, so that the electrical performance of the silicon light modulator can be controlled by the external input voltage, and the consistency with the existing silicon light modulator comprising a double-electrode structure can be improved.
Specifically, the first electrode 140 may include a plurality of first extension structures 141, and the plurality of first extension structures 141 cover and electrically connect the P-type doped region 110.
It should be noted that, in the example of the mach-Zeng Degui optical modulator illustrated in fig. 3, since the mach-Zeng Degui optical modulator has two branches, each including the adjacent P-type doped region 110 and N-type doped region 120, but only a single electrode is connected, it is understood that the first extension structure 141 of the first electrode 140 may be disposed to be connected to only the P-type doped region 110 of the first branch, and the second extension structure 151 of the second electrode 150 may be connected to only the N-type doped region (not shown) of the second branch. However, for the modulators in which adjacent P-type doped regions and N-type doped regions are respectively connected to electrodes, the plurality of first extension structures cover and electrically connect to the P-type doped regions, and the plurality of second extension structures cover and electrically connect to the N-type doped regions.
In the embodiment of the present invention, the areas of the plurality of first extension structures 141 are gradually increased and the areas of the plurality of second extension structures 151 are gradually increased along the axial direction of the ridge structure 100.
Wherein the length of the extension structure increases in a direction from an optical signal input direction to an optical signal output direction.
In the embodiment of the invention, the electrode comprising the extension structure is formed, the extension structure covers and is electrically connected with the P-type doped region and the N-type doped region respectively, and the extension structures are arranged along the axial direction of the ridge structure 100, so that the areas of the extension structures are gradually increased, and the voltage attenuation of the high-speed signal of the PN junction region can be compensated by adjusting the areas of the extension structures along the axial direction of the ridge structure 100, thereby ensuring that the PN junction is uniformly modulated in the transmission process of the high-speed signal along the modulation arm, further ensuring the stability of characteristic impedance and the stability of microwave refractive index, reducing impedance mismatch, matching refractive index and improving modulation efficiency, and further improving the bandwidth of the modulator.
It can be appreciated that the technical scheme in the embodiment of the invention has lower design complexity and lower cost, does not need to introduce an additional control circuit and electrical compensation, and can effectively improve the performance of the modulator.
It should be noted that, in the embodiment of the present invention, the etching process may be performed first to obtain the ridge structure 100, and then ion implantation may be performed; the semiconductor substrate after ion implantation can be etched to obtain a ridge structure.
Further, the larger the voltage attenuation ratio of the input signal is in the axial direction of the ridge structure 100, the larger the area of the first extension structure 141 and the second extension structure 151 is.
Specifically, the high-speed traveling wave signal has microwave loss and voltage attenuation in the transmission process, so that the driving voltage is smaller as the driving voltage is far away from the input direction of the optical signal.
The first extension structures 141 may have equal widths and are smaller than or equal to the width of the P-type doped region 110, and may also be larger than the width of the P-type doped region 110; the second extension structures 151 may have equal widths and are all smaller than or equal to the width of the N-type doped region 120, and may also be larger than the width of the N-type doped region 120; wherein the direction of the width is perpendicular to the axial direction.
In the embodiment of the present invention, by setting the voltage attenuation ratio of the input signal to be greater along the axial direction of the ridge structure 100, the area of the first extension structure 141 and the area of the second extension structure 151 are increased more, so that the extent of the increase of the area of the extension structure can be determined according to the voltage attenuation condition of the input signal, and then the scheme in the embodiment of the present invention is implemented, so as to reduce impedance mismatch, improve modulation efficiency, and further improve the bandwidth of the modulator.
Further, the first extension structure 141 and the second extension structure 151 may each be a T-shaped structure, where a length of a first end of the T-shaped structure is greater than a length of a second end of the T-shaped structure, and the second end of the first extension structure covers and is electrically connected to the P-type doped region, and the second end of the second extension structure covers and is electrically connected to the N-type doped region; the direction of the length is parallel to the axial direction.
Taking the first extension structure 141 in fig. 2 as an example, the second end of the T-shaped structure is a narrow end on the left side, and the length of the second end is smaller; the first end of the T-shaped structure is the wide end on the right side, and the length of the T-shaped structure is larger.
Referring to fig. 4, fig. 4 is a top view of another silicon optical modulator in an embodiment of the invention. The P-type doped region and the N-type doped region are divided into a plurality of length regions L with preset lengths along the axial direction, the plurality of first extension structures 141 respectively correspond to the plurality of length regions L of the P-type doped region one by one and respectively cover a part of the P-type doped region in the corresponding length region L, and the plurality of second extension structures 151 respectively correspond to the plurality of length regions L of the N-type doped region one by one and respectively cover a part of the N-type doped region in the corresponding length region L; wherein, in each length region L along the axial direction of the P-type doped region, the length ratio of the first extension structure 141 is gradually increased, and in each length region L along the axial direction of the N-type doped region, the length ratio of the second extension structure 151 is gradually increased.
As shown in fig. 4, in the adjacent optical signal input direction, in the length region L, the length D1 of the extension structure is smaller, and the length D2 of the remaining region is larger; in the vicinity of the optical signal output direction, the length D1 of the extension structure is larger in the length region L, and the length D2 of the remaining region is smaller.
Wherein the remaining area D2 may be equal to the length D1 of the length area L-extension structure.
Further, in each length region L of the P-type doped region, the ratio of the length of the first extension structure 141 to the length of the remaining region is positively correlated with the voltage decay ratio of the input signal; in each length region L of the N-type doped region, the ratio of the length of the second extension structure 151 to the length of the remaining region is positively correlated with the voltage decay ratio of the input signal.
Wherein the ratio of the length of the extension structure to the length of the remaining area may be equal to D1/D2.
In the embodiment of the present invention, the ratio of the length of the first extension structure 141 to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal, which is disposed in each length region of the P-type doped region; in each length region L of the N-type doped region, the ratio of the length of the second extension structure 151 to the length of the remaining region is positively related to the voltage attenuation ratio of the input signal, so that the degree of the length increase of the extension structure in each length period can be more accurately determined according to the voltage attenuation condition of the input signal in each length period, thereby further effectively reducing impedance mismatch, improving modulation efficiency, and further improving the bandwidth of the modulator.
In the embodiment of the present invention, the P-type doped region and the N-type doped region are divided into a plurality of length regions L with preset lengths along the axial direction, the length ratio of the first extension structure 141 is gradually increased in each length region L along the axial direction of the P-type doped region, and the length ratio of the second extension structure 151 is gradually increased in each length region L along the axial direction of the N-type doped region. By adopting the scheme of the embodiment of the invention, the length increase degree of the extension structure can be better controlled by adopting the length period, so that the impedance mismatch is further reduced, the modulation efficiency is improved, and the bandwidth of the modulator is further improved.
In an embodiment of the present invention, a silicon optical modulator is also disclosed, as shown in fig. 3 and fig. 4, which may include: a ridge structure 100, wherein the ridge structure 100 is obtained by etching the surface of a semiconductor substrate, and the ridge structure 100 is provided with a P-type doped region and an N-type doped region which are adjacent to each other; a first electrode 140 and a second electrode 150, the first electrode 140 including a plurality of first extension structures 141, the plurality of first extension structures 141 covering and electrically connecting the P-type doped region 110, the second electrode 150 including a plurality of second extension structures 151, the plurality of second extension structures 151 covering and electrically connecting the N-type doped region 120; wherein, along the axial direction of the ridge structure 100, the areas of the plurality of first extension structures 141 are gradually increased, and the areas of the plurality of second extension structures 151 are gradually increased; the first electrode 140 is one of an anode electrode and a cathode electrode, and the second electrode 150 is the other of the anode electrode and the cathode electrode.
Further, the larger the voltage attenuation ratio of the input signal is in the axial direction of the ridge structure 100, the larger the area of the first extension structure 141 and the second extension structure 151 is.
Further, the P-type doped region and the N-type doped region are divided into a plurality of length regions L with preset lengths along the axial direction, the plurality of first extension structures 141 respectively correspond to the plurality of length regions L of the P-type doped region one by one and respectively cover a part of the P-type doped region in the corresponding length region L, and the plurality of second extension structures 151 respectively correspond to the plurality of length regions L of the N-type doped region one by one and respectively cover a part of the N-type doped region in the corresponding length region L; wherein, in each length region L along the axial direction of the P-type doped region, the length ratio of the first extension structure 141 is gradually increased, and in each length region L along the axial direction of the N-type doped region, the length ratio of the second extension structure 151 is gradually increased.
In the embodiment of the invention, the electrode comprising the extension structure is formed, the extension structure covers and is electrically connected with the P-type doped region and the N-type doped region respectively, and the extension structures are arranged along the axial direction of the ridge structure 100, so that the areas of the extension structures are gradually increased, and the voltage attenuation of the high-speed signal of the PN junction region can be compensated by adjusting the areas of the extension structures along the axial direction of the ridge structure 100, thereby ensuring that the PN junction is uniformly modulated in the transmission process of the high-speed signal along the modulation arm, further ensuring the stability of characteristic impedance and the stability of microwave refractive index, reducing impedance mismatch, matching refractive index and improving modulation efficiency, and further improving the bandwidth of the modulator.
For the principles, specific implementations and advantages of the silicon optical modulator, reference should be made to the foregoing description of the method for forming the silicon optical modulator, which is not repeated herein.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (10)
1. A method of forming a silicon optical modulator, comprising:
Providing a semiconductor substrate;
Etching is carried out on the surface of the semiconductor substrate to obtain a ridge structure, wherein the ridge structure is provided with a P-type doped region and an N-type doped region which are adjacent;
forming a first electrode and a second electrode, wherein the first electrode comprises a plurality of first extension structures, the plurality of first extension structures cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures, and the plurality of second extension structures cover and are electrically connected with the N-type doped region;
Wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase;
the first electrode is one of an anode electrode and a cathode electrode, and the second electrode is the other of the anode electrode and the cathode electrode.
2. The method of forming a silicon optical modulator of claim 1,
The larger the voltage attenuation ratio of the input signal is along the axial direction of the ridge structure, the larger the area increase ratio of the first extension structure and the second extension structure is.
3. The method of forming a silicon optical modulator according to claim 1 or 2, wherein,
The P-type doped region and the N-type doped region are divided into a plurality of length regions with preset lengths along the axial direction, the plurality of first extension structures are respectively in one-to-one correspondence with the plurality of length regions of the P-type doped region and cover a part of the P-type doped region in the corresponding length region, and the plurality of second extension structures are respectively in one-to-one correspondence with the plurality of length regions of the N-type doped region and cover a part of the N-type doped region in the corresponding length region;
wherein the length ratio of the first extension structure is gradually increased in each length region along the axial direction of the P-type doped region, and the length ratio of the second extension structure is gradually increased in each length region along the axial direction of the N-type doped region.
4. A method of forming a silicon optical modulator according to claim 3, wherein one or more of the following is satisfied:
In each length region of the P-type doped region, the ratio of the length of the first extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal;
In each length region of the N-type doped region, the ratio of the length of the second extension structure to the length of the remaining region is positively correlated with the voltage attenuation ratio of the input signal.
5. The method of forming a silicon optical modulator of claim 1,
The first electrode is electrically connected to the third concentration doped region of the P-type doped region, and the second electrode is electrically connected to the third concentration doped region of the N-type doped region.
6. The method of claim 1, wherein the first extension structure and the second extension structure are each a T-shaped structure, a length of a first end of the T-shaped structure being greater than a length of a second end;
The second end of the first extension structure covers and is electrically connected with the P-type doped region, and the second end of the second extension structure covers and is electrically connected with the N-type doped region;
the direction of the length is parallel to the axial direction.
7. The method of claim 1, wherein the silicon optical modulator is a mach-Zeng Degui optical modulator and the axial direction of the ridge structure is the modulation arm direction of the mach-Zeng Degui optical modulator.
8. A silicon optical modulator, comprising:
the ridge structure is obtained by etching the surface of the semiconductor substrate and is provided with a P-type doped region and an N-type doped region which are adjacent to each other;
The first electrode comprises a plurality of first extension structures which cover and are electrically connected with the P-type doped region, and the second electrode comprises a plurality of second extension structures which cover and are electrically connected with the N-type doped region;
Wherein, along the axial direction of the ridge structure, the areas of the plurality of first extension structures gradually increase, and the areas of the plurality of second extension structures gradually increase;
the first electrode is one of an anode electrode and a cathode electrode, and the second electrode is the other of the anode electrode and the cathode electrode.
9. The silicon optical modulator of claim 8 wherein the silicon optical modulator is configured to,
The larger the voltage attenuation ratio of the input signal is along the axial direction of the ridge structure, the larger the area increase ratio of the first extension structure and the second extension structure is.
10. The silicon optical modulator according to claim 8 or 9, wherein,
The P-type doped region and the N-type doped region are divided into a plurality of length regions with preset lengths along the axial direction, the plurality of first extension structures are respectively in one-to-one correspondence with the plurality of length regions of the P-type doped region and cover a part of the P-type doped region in the corresponding length region, and the plurality of second extension structures are respectively in one-to-one correspondence with the plurality of length regions of the N-type doped region and cover a part of the N-type doped region in the corresponding length region;
wherein the length ratio of the first extension structure is gradually increased in each length region along the axial direction of the P-type doped region, and the length ratio of the second extension structure is gradually increased in each length region along the axial direction of the N-type doped region.
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