CN116449586A - Electroabsorption modulator with germanium modulation layer and forming method thereof - Google Patents
Electroabsorption modulator with germanium modulation layer and forming method thereof Download PDFInfo
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- 229910052732 germanium Inorganic materials 0.000 title claims abstract description 157
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 title claims abstract description 157
- 238000000034 method Methods 0.000 title claims abstract description 54
- 239000000758 substrate Substances 0.000 claims abstract description 41
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 25
- 229910052710 silicon Inorganic materials 0.000 claims description 25
- 239000010703 silicon Substances 0.000 claims description 25
- 238000010521 absorption reaction Methods 0.000 claims description 16
- 238000005530 etching Methods 0.000 claims description 14
- 239000000470 constituent Substances 0.000 claims description 6
- 239000002356 single layer Substances 0.000 claims description 4
- 238000000465 moulding Methods 0.000 claims description 3
- 230000007547 defect Effects 0.000 abstract description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 25
- 238000000151 deposition Methods 0.000 description 25
- 230000000052 comparative effect Effects 0.000 description 24
- 238000005468 ion implantation Methods 0.000 description 21
- 238000000137 annealing Methods 0.000 description 13
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- 230000008569 process Effects 0.000 description 11
- 229910000577 Silicon-germanium Inorganic materials 0.000 description 10
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- 239000000377 silicon dioxide Substances 0.000 description 9
- 238000001312 dry etching Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
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- 229910002601 GaN Inorganic materials 0.000 description 2
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
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- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- G02F1/0155—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 modulating the optical absorption
- G02F1/0157—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 modulating the optical absorption using electro-absorption effects, e.g. Franz-Keldysh [FK] effect or quantum confined stark effect [QCSE]
-
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention relates to the technical field of semiconductors, in particular to an electroabsorption modulator with a germanium modulation layer and a forming method thereof; the modulator includes: the semiconductor device comprises a substrate layer, a doped layer formed on the top of the substrate layer, a buffer layer connected with the top center of the doped layer, a modulation layer formed on the top of the buffer layer, and top dielectric layers formed on the top free area and the inner side surface of the doped layer, the side surface of the buffer layer and the top and side surfaces of the modulation layer; by adding the buffer layer, the strain of the modulation layer is reduced, the working wavelength of the modulator is 1540nm-1560nm, and the defect that the working wavelength of the pure germanium electroabsorption modulator in the prior art cannot be matched with the C wave band is overcome.
Description
Technical Field
The invention relates to the technical field of semiconductor packaging materials, in particular to an electroabsorption modulator with a germanium modulation layer and a forming method thereof.
Background
Silicon photonics offers a low cost, low power consumption and high bandwidth optoelectronic solution, which is important for achieving high speed low power optical modulator integration with silicon-based optical circuits. To achieve a low power and high density interconnect system, the optical modulator requires very little capacitance. Electro-absorption modulators (EAMs) are promising because of their much smaller capacitance than silicon-based MZI-type modulators. Current pure germanium electroabsorption modulators are all Ge grown epitaxially directly on a silicon substrate, with tensile strain up to 0.2%, and the bandgap energy of germanium decreases from unstrained 0.80eV (1550 nm) to tensile strained 0.77eV (1610 nm). Therefore, most pure germanium electroabsorption modulators operate in the O-band, and in order to operate in the C-band, a new structure and process flow need to be proposed to optimize the operating wavelength, so that the pure germanium electroabsorption modulator operating wavelength is shifted to the C-band.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide an electroabsorption modulator with a germanium modulation layer and a forming method thereof, so as to solve at least one of the problems of small modulation speed and modulation bandwidth, large insertion loss, and unable matching of working wavelength with C-band in the prior art.
The invention provides an electroabsorption modulator with a germanium modulation layer, comprising:
a substrate layer comprising a back substrate and a bottom oxide dielectric layer disposed on the silicon substrate;
a doped layer formed on top of the bottom oxidation mediating layer, comprising: a hole strongly doped layer, a hole weakly doped layer, an electron strongly doped layer; the hole weakly doped layer and the electron weakly doped layer are protruded in the middle area of the top of the bottom oxidation dielectric layer and connected to form a PN junction, and are used as bottom waveguide layers; the hole strong doping layer and the electron strong doping layer are respectively arranged at two ends of the top of the bottom oxidation dielectric layer, the hole strong doping layer is connected with the hole weak doping layer, and the electron weak doping layer is connected with the electron strong doping layer;
the buffer layer is formed on the top of the PN junction;
a modulation layer formed on top of the buffer layer; comprising the following steps: a germanium hole doped layer, a germanium waveguide layer, a germanium electron doped layer; the germanium hole doping layer and the germanium electron doping layer are respectively arranged at two ends of the top of the buffer layer and are connected through the germanium waveguide layer;
and the top oxidation dielectric layer is formed on the top free region and the inner side surface of the doped layer, the side surface of the buffer layer and the top and the side surface of the modulation layer.
Preferably, the buffer layer comprises a single layer or multiple layers.
Preferably, the single-layer buffer layer is composed of one two-component compound, and the multi-layer buffer layer is composed of two-component compounds having different component contents.
Preferably, a plurality of layers of bufferingThe proportion of the two components of the two-component compound in each layer in the punching layer is changed according to the forward gradient or the reverse gradient; wherein, the general formula of the two-component compound is as follows: a is that 1-x B x Wherein A, B represents a two-component compound constituent element; x is less than or equal to 1, and represents the atomic number of the element B in the two-component compound.
Preferably, the two-component compounds have the formula: the multi-layer buffer layers are marked as follows in the molding sequence from bottom to top: a first buffer layer, …, an nth buffer layer; wherein the two-component compound of the N buffer layer has the general formula of A (1-x) N B x N The two-component compound of the N-1 buffer layer has the general formula A (1-x) N-1 B x N-1 ， x N-1 ＜ x N Or (b) x N-1 ＞ x N The method comprises the steps of carrying out a first treatment on the surface of the Wherein A, B represents a constituent element of a two-component compound, x N Representing the atomic number of the two-component compound element B of the N buffer layer, (-) 1-x ) N The atomic number of the two-component compound element a of the nth buffer layer is represented.
Preferably, the doping concentration of the germanium hole doped layer and the germanium electron doped layer is 1×10 18 cm 3 ～5×10 18 cm 3 。
Preferably, the germanium waveguide layer has a width of 100nm to 400nm and a height of 200nm to 500nm.
Preferably, the operating wavelength is 1540nm to 1560nm.
Preferably, the buffer layer includes: a group III, group V and group IV semiconductor compound, and a group IV, group V and group V semiconductor compound.
A method of forming an electroabsorption modulator having a germanium modulation layer, comprising:
step 1: preparing doped layers with different doping concentrations on the substrate layer;
step 2: etching the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer, and preparing a bottom waveguide layer in the connecting area of the hole weakly doped layer and the electron weakly doped layer;
step 3: forming a buffer layer on top of the bottom waveguide layer;
step 4: forming an original modulation layer on top of the buffer layer;
step 5: and forming a germanium hole doped layer, a germanium waveguide layer and a germanium electron doped layer with different doping concentrations on the original modulation layer.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) The invention reduces the strain of the modulation layer by adding the buffer layer, so that the working wavelength of the modulator is changed from 1540nm to 1560nm, the modulation speed is changed from 40Gbps to 56Gbps, the modulation bandwidth is changed from 55GHz to 67GHz, and the insertion loss is changed from 4.0dB to 7.9 dB; the defect that the working wavelength of the pure germanium electroabsorption modulator cannot be matched with the C wave band in the prior art is overcome.
(2) The invention is characterized in that the buffer layers are arranged according to a reverse gradient, and the buffer layers are exemplarily and sequentially marked as follows from bottom to top: a first buffer layer, …, an nth buffer layer; the general formula of the two-component compound of the N buffer layer is as follows: a% 1-x ) N B x N The general formula of the two-component compound of the N-1 buffer layer is as follows: a% 1-x ) N-1 B x N-1 And (2) and x N-1 ＜ x N the method comprises the steps of carrying out a first treatment on the surface of the Wherein A, B represents a constituent element of a two-component compound, A is silicon or an element close to silicon in the periodic table, and B is germanium or an element close to germanium in the periodic table; x is x N The atomic number of the two-component compound element B representing the nth buffer layer; ( 1-x ) N The atomic number of the two-component compound element a of the nth buffer layer; through the arrangement, the invention can obtain larger working wavelength, modulation speed and modulation bandwidth and smaller insertion loss.
(3) According to the invention, the hole weakly doped layer and the electron weakly doped layer are arranged on the bottom waveguide layer of the doped layer, so that the modulation speed and the modulation bandwidth are improved, the insertion loss is reduced, and the control sensitivity is further improved.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the embodiments of the invention particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a schematic illustration of preparing doped layers with different doping concentrations on a substrate layer in one embodiment of the invention;
FIG. 2 is a schematic diagram of an etch preparation of a bottom waveguide layer in one embodiment of the present invention;
FIG. 3 is a schematic diagram of forming a buffer layer on top of a bottom waveguide layer in one embodiment of the present invention;
FIG. 4 is a schematic diagram of forming an original modulation layer on top of a buffer layer according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of forming a germanium hole doped layer, a germanium waveguide layer, and a germanium electron doped layer with different doping concentrations in an original modulation layer according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an electrode grown on an electron strongly doped layer and a hole strongly doped layer according to an embodiment of the present invention;
fig. 7 is a schematic diagram of the finished electro-absorption modulator of comparative example 9 of the present invention.
Reference numerals
A substrate layer 1; a doped layer 2; a buffer layer 3; a modulation layer 4; a top oxide dielectric layer 5; an original modulation layer 6; an electrode 7; a substrate 101; a bottom oxide dielectric layer 102; a hole heavily doped layer 201; an electron strongly doped layer 202; a hole weakly doped layer 203; an electron weakly doped layer 204; germanium hole doped layer 401; germanium waveguide layer 402; germanium electron doped layer 403.
Detailed Description
The following detailed description of preferred embodiments of the invention is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the invention, are used to explain the principles of the invention and are not intended to limit the scope of the invention.
For better description of the technical solution of the present invention, the following terms are described:
SOI refers to placing a thin layer of silicon on an insulating substrate and transistors will be fabricated on the thin layer of silicon known as SOI. Compared with a common wafer structure, the device on the SOI structure can reduce junction capacitance and leakage current, improve switching speed, reduce power consumption, realize high-speed and low-power-consumption operation, and is particularly suitable for submicron and nanoscale chip structures.
Parasitic capacitance: the capacitor characteristics of inductance, resistance, chip pins and the like under the high-frequency condition are not obvious, and the equivalent value is increased under the high-frequency condition; resistance, inductance, or IC chip, all take into account their equivalent capacitance at high frequencies.
Chemical Mechanical Polishing (CMP): under a certain pressure and in the presence of polishing liquid, the polished wafer moves relatively to the polishing pad, and the surface of the polished wafer meets the requirements of high planarization, low surface roughness and low defects by means of the high organic combination of the mechanical grinding action of the nano abrasive and the chemical action of various chemical reagents.
The invention discloses an electroabsorption modulator with a germanium modulation layer, comprising:
a substrate layer 1 including a back substrate 101 and a bottom oxidation medium 102 disposed on the back substrate 101;
doped layer 2, formed on top of the bottom oxide dielectric layer 102, comprises: a hole strongly doped layer 201, a hole weakly doped layer 203, an electron weakly doped layer 204, an electron strongly doped layer 202; hole weakly doped layer 203 and electron weakly doped layer 204 protrude and connect in the middle area of the top of the bottom oxidation mediating layer 102 to form a PN junction, and serve as a bottom waveguide layer; the hole strong doping layer 201 and the electron strong doping layer 202 are respectively arranged at two ends of the top of the bottom oxidation dielectric layer 102, the hole strong doping layer 201 is connected with the hole weak doping layer 203, and the electron weak doping layer 204 is connected with the electron strong doping layer 202;
a buffer layer 3 formed on top of the PN junction;
a modulation layer 4 formed on top of the buffer layer 3; comprising the following steps: germanium hole doped layer 401, germanium waveguide layer 402, germanium electron doped layer 403; the germanium hole doped layer 401 and the germanium electron doped layer 403 are respectively arranged at two ends of the top of the buffer layer 3 and are connected through the germanium waveguide layer 402;
and a top oxidation dielectric layer 5 formed on the top free region and the inner side of the doped layer 2, the side of the buffer layer 3, and the top and side of the modulation layer 4.
Regarding the modulation principle of the electroabsorption modulator, it should be noted that: the light beam with a specific wavelength is transmitted to the silicon waveguide through the external grating coupler, the bottom waveguide layer and the germanium waveguide are of an upper-lower structure, the light in the silicon waveguide can be coupled to the germanium waveguide through evanescent coupling, and then the light beam is modulated in the germanium waveguide; after being modulated, the material enters a modulation area formed by the modulation layer and the bottom waveguide layer, and then is oscillated and propagated between the modulation layer and the bottom waveguide layer.
Specifically, the wavelength of the modulator that can be modulated is related to the material, size and structure of the modulating layer, for example, an electroabsorption modulator of pure germanium is a Ge that is directly epitaxially grown on a silicon substrate with a silicon substrate as a backing substrate, and has a tensile strain of up to 0.2%, and due to the strain, the band gap energy of the Ge is reduced from unstrained 0.80eV 1550nm to tensile strain 0.77eV1010nm.
Specifically, modulation layer modulation includes: when the hole strong doping layer and the electron strong doping layer are loaded with reverse modulation electric signals, the light absorption coefficient of the modulation layer to the light beam changes along with the change of the modulation electric signals, and the light power of the light beam after passing through the modulation area correspondingly changes, so that the electro-optic modulation of the light beam is realized.
Specifically, the invention introduces a buried oxide layer (bottom oxide dielectric layer) between the back substrate and the doped layer, namely, the back substrate and the buried oxide layer form an SOI process substrate layer, and has the following advantages: the dielectric isolation of components in the integrated circuit can be realized, and the parasitic latch-up effect in the CMOS circuit is thoroughly eliminated; the integrated circuit made of the material also has the advantages of small parasitic capacitance, high integration density, high speed, simple process and small short channel effect.
Specifically, the backing substrate is silicon, and the bottom oxidation dielectric layer is silicon dioxide.
Specifically, the doped layer is silicon.
The doped layer is made of silicon, can be compatible with the SOI technology, is convenient for selecting SOI wafers from the market, and expands the application range.
Specifically, the doping concentration of the hole strong doping layer and the electron strong doping layer is 1×10 19 cm 3 ～3×10 19 cm 3 。
Specifically, the doping of the hole strong doping layer and the electron strong doping layer can realize ohmic contact between the strong doping layer and the external electrode, so that the energy consumption is reduced, and the control sensitivity of the external voltage is improved; the doping concentration of the hole strong doping layer and the electron strong doping layer is too large to diffuse, so that two overlapping areas are generated with the lightly doped area, and absorption loss is increased.
Specifically, the doping concentration of the hole strong doping layer and the electron strong doping layer can be: 1X 10 19 cm 3 、1.2×10 19 cm 3 、1.4×10 19 cm 3 、1.5×10 19 cm 3 、1.6×10 19 cm 3 、1.8×10 19 cm 3 、2.0×10 19 cm 3 、2.2×10 19 cm 3 、2.4×10 19 cm 3 、2.5×10 19 cm 3 、2.6×10 19 cm 3 、2.8×10 19 cm 3 、2.9×10 19 cm 3 、3×10 19 cm 3 。
Specifically, the doping concentration of the electron weakly doped layer and the hole weakly doped layer is 4×10 18 cm 3 ～6×10 18 cm 3 。
The doping benefits of the hole weakly doped layer and the electron weakly doped layer are as follows: the carrier quantity is increased, and the modulation rate is improved; forming an electric field under the action of an externally applied bias voltage; the doping concentration of the electron weakly doped layer and the hole weakly doped layer exceeds a limiting range, the doping concentration is too high and can be diffused, and further two overlapping areas are generated with the heavily doped area, so that absorption loss can be increased.
Specifically, the doping concentration of the electron weakly doped layer and the hole weakly doped layer may be: 4X 10 18 cm 3 、4.2×10 18 cm 3 、4.4×10 18 cm 3 、4.5×10 18 cm 3 、4.6×10 18 cm 3 、4.8×10 18 cm 3 、5.0×10 18 cm 3 、5.2×10 18 cm 3 、5.4×10 18 cm 3 、5.5×10 18 cm 3 、5.6×10 18 cm 3 、5.8×10 18 cm 3 、5.9×10 18 cm 3 、6×10 18 cm 3 。
Specifically, the cross-sectional size of the modulation layer is 200nm to 500nm×200nm to 500nm.
Preferably, the germanium hole doped layer and the germanium electron doped layer have the same size, are symmetrically arranged relative to the germanium waveguide layer, and have the same height as the germanium waveguide layer.
Preferably, the doping concentration of the germanium hole doped layer and the germanium electron doped layer is 1×10 18 cm 3 ～5×10 18 cm 3 。
Specifically, the doping concentration of the germanium hole doping layer and the germanium electron doping layer may be: 1X 10 18 cm 3 、1.2×10 18 cm 3 、1.5×10 18 cm 3 、1.8×10 18 cm 3 、2.2×10 18 cm 3 、2.5×10 18 cm 3 、2.8×10 18 cm 3 、3.0×10 18 cm 3 、3.2×10 18 cm 3 、3.3×10 18 cm 3 、3.5×10 18 cm 3 、3.8×10 18 cm 3 、4.0×10 18 cm 3 、4.2×10 18 cm 3 、4.4×10 18 cm 3 、4.6×10 18 cm 3 、4.8×10 18 cm 3 、5.0×10 18 cm 3 。
The germanium hole doped layer and the germanium electron doped layer are doped, so that the two doped layers and the germanium waveguide layer can form a PIN junction, and the specific function is as follows: a built-in electric field caused by the PIN junction is arranged in the modulation area; when a modulated electrical signal is reversely loaded on the PIN junction, a built-in electric field in the modulated layer changes along with the change of the modulated electrical signal, when the modulated electrical signal is increased, the built-in electric field is increased, the absorption of the light beam by the modulated layer is increased, when the modulated electrical signal is reduced, the built-in electric field is reduced, and the absorption of the light beam by the modulated layer is reduced.
It should be noted that, too low doping concentration of the germanium hole doped layer and the germanium electron doped layer may cause too small number of carriers in the modulation layer, affecting the modulation rate; too high a carrier concentration increases its absorption loss.
Preferably, the germanium waveguide layer has a width of 100nm to 400nm and a height of 200nm to 500nm.
Specifically, the germanium waveguide layer width is 100nm, 150nm, 160nm, 180nm, 200nm, 220nm, 230nm, 250nm, 260nm, 280nm, 300nm, 320nm, 340nm, 350nm, 360nm, 380nm, 390nm, 400nm.
Specifically, the germanium waveguide layer has a height of 200nm, 250nm, 260nm, 280nm, 200nm, 320nm, 330nm, 350nm, 360nm, 380nm, 400nm, 420nm, 440nm, 450nm, 460nm, 480nm, 490nm, 500nm.
It should be noted that, the doped layers with different dimensions (mainly the width of the germanium waveguide layer) can affect the light absorption coefficient of the germanium waveguide layer and the capacitance resistance in simulation, where the light absorption coefficient affects the modulation effect of the device, and the capacitance Resistance (RC) can affect the modulation bandwidth of the modulator, and the modulation bandwidth is an important performance index of the modulator: in general, the wider the modulation bandwidth, the greater the reaction modulator modulation range.
Preferably, the modulating layer has a rectangular cross section.
Preferably, the germanium waveguide layer is highly planar with respect to the germanium hole doped layer and the germanium electron doped layer.
The cross section of the modulation layer is rectangular, so that the overflow of light in all directions of the cross section can be reduced, the light can be better limited in the modulation layer, and the light loss in the modulation process is reduced.
Preferably, the buffer layer comprises one or more layers.
Preferably, the single-layer buffer layer is composed of one two-component compound, and the multi-layer buffer layer is composed of two-component compounds with different component contents.
The proportion of two components of the two-component compounds in each layer in the multilayer buffer layer is changed according to a forward gradient or a reverse gradient; wherein, the general formula of the two-component compound is as follows:
specifically, the multi-layer buffer layer is marked as follows in the molding sequence from bottom to top: a first buffer layer, …, an nth buffer layer; the general formula of the two-component compound of the N buffer layer is A 1-x ) N B x N The general formula of the two-component compound of the N-1 buffer layer is A # 1-x ) N-1 B x N-1 ， x N-1 ＜ x N Or (b) x N-1 ＞ x N The method comprises the steps of carrying out a first treatment on the surface of the Wherein A, B represents a constituent element of a two-component compound, A is silicon or an element close to silicon in the periodic table, and B is germanium or an element close to germanium in the periodic table; x is x N The atomic number of the two-component compound element B representing the nth buffer layer;
( 1-x ) N the atomic number of the two-component compound element a of the nth buffer layer is represented.
Specifically, the strain can be reduced by changing the ratio of the two components of the two-component compound in each layer of the multi-layer buffer layer according to a forward gradient or a reverse gradient.
Preferably, the method comprises the steps of, x N-1 ＞ x N i.e. the B component is reduced in the multi-layer buffer layer from bottom to top.
The reverse gradient buffer layer has better strain eliminating effect under the same condition; the thickness of the reverse gradient buffer layer is smaller than that of the forward gradient buffer layer under the same condition of reducing the stress effect.
Specifically, the buffer layer includes: a group III, group V and group IV semiconductor compound, and a group IV, group V and group V semiconductor compound.
Preferably, the buffer layer includes: the semiconductor is any one of a silicon germanium semiconductor, a silicon carbide semiconductor and a silicon nitride semiconductor.
Preferably, the germanium silicide semiconductor buffer layer is selected, and the reason is that: on the one hand, the energy band width of silicon is larger, and the energy band width of the germanium-silicon alloy can be adjusted according to the different silicon contents; on the other hand, germanium-silicon semiconductors can well reduce the strain of the bottom and germanium waveguide layers.
It should be noted that, in the prior art, pure germanium electroabsorption modulators are all Ge grown epitaxially directly on a silicon substrate, which has a tensile strain of up to 0.2%, and the band gap energy of germanium is reduced from unstrained 0.80ev 1550nm to tensile strained 0.77ev1010nm due to the presence of the strain. Therefore, most pure germanium electroabsorption modulators operate in the O-band, and in order to operate in the C-band, the invention provides a buffer layer to reduce or even eliminate the strain created by the germanium modulation layer.
Preferably, the electroabsorption modulator can modulate the wavelength of light to 1540nm-1560nm.
Preferably, different areas of the hole weakly doped layer and the electron weakly doped layer are selectively etched, so that the height of the joint of the hole weakly doped layer and the electron weakly doped layer with the buffer layer is flush with that of the hole strongly doped layer and the electron strongly doped layer, PN junction joint areas of the hole weakly doped layer and the electron weakly doped layer are protruded, and a bottom waveguide layer is formed.
Specifically, except for the areas where the hole weakly doped layer and the electron weakly doped layer are connected with the buffer layer, etching the hole weakly doped layer and the electron weakly doped layer, and forming a concave structure on the hole weakly doped layer and the electron weakly doped layer, so that PN junction connection areas corresponding to projections of the hole weakly doped layer, the electron weakly doped layer and the buffer layer are protruded relative to the concave structure, and a bottom waveguide layer is formed.
Preferably, the top of the hole strong doping layer and the top of the electron strong doping layer are provided with electrodes 7; the top oxidation dielectric layer 5 is lower than the electrode 7 in height, so that the protruding part of the electrode 7 is convenient to connect with an external power supply.
Preferably, the top oxidation mediating layer is selected from the group consisting of silica: on one hand, the silicon dioxide dielectric constant can be utilized to carry out passivation insulation treatment on the surface of the germanium layer; on the other hand, silicon oxide is used as an upper coating layer of the modulation layer, the doping layer and the buffer layer, so that the stress of each layer connected with the silicon oxide can be balanced.
In another aspect, the invention discloses a method for forming an electroabsorption modulator with a germanium modulation layer, as shown in fig. 1-6, comprising the steps of:
step 1: preparing doped layers 2 with different doping concentrations on a substrate layer 1;
step 2: etching the hole weakly doped layer 203 and the electron weakly doped layer 204 in the middle region of the doped layer 2, and preparing a bottom waveguide layer in the connecting region of the two layers;
step 3: forming a buffer layer 3 on top of the bottom waveguide layer;
step 4: forming an original modulation layer 6 on top of the buffer layer 3;
step 5: a germanium hole doped layer 401, a germanium waveguide layer 402, a germanium electron doped layer 403 having different doping concentrations are formed in the original modulation layer 6.
Specifically, in step 1, a doped base layer with different doping concentrations is prepared on a substrate layer by ion implantation.
Specifically, the preparation of the doped layers with different doping concentrations in step 1 includes:
s101: depositing a doped base layer on the substrate layer;
s102: forming a low doped region by low dose ion implantation;
s103: forming a high doped region in a specific region of the low doped region by high-dose ion implantation;
s104: and (5) carrying out high-temperature annealing treatment to obtain doped layers with different doping concentrations.
Specifically, the method for depositing the doped base layer is ion implantation.
Specifically, the low dose ion implantation dose is: 4X 10 18 cm 3 ～6×10 18 cm 3 。
Specifically, the ion implantation dose of the high dose is: 1X 10 19 cm 3 ～3×10 19 cm 3 。
Specifically, etching the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer in the step 2 includes:
s201: marking patterns to be etched on the hole weakly doped layer and the electron weakly doped layer by using a mask;
s202: and etching the doped layer based on the marked pattern to obtain a hole weakly doped layer and an electron weakly doped layer with target shapes, wherein the connecting areas of the hole weakly doped layer and the electron weakly doped layer protrude to form a bottom waveguide layer.
Specifically, dry etching is used in step S202.
Specifically, the dry etching includes: plasma etching and reactive ion etching.
Specifically, in step 3, forming a buffer layer includes:
s301: depositing a top oxidation dielectric layer for the first time in the etched area;
s302: marking a pattern to be etched on the top oxidation dielectric layer by using a mask;
s303: etching a top oxidation dielectric layer of a top area of the waveguide layer based on the marked graph to obtain a concave area matched with the target shape of the buffer layer;
s304: and growing a buffer layer in the concave area by chemical vapor deposition.
Specifically, in step S301, a top oxide dielectric layer is grown using thin film deposition.
Preferably, step S301 further includes a CMP process for growing a silicon oxide layer by thin film deposition.
It will be appreciated that the thickness of the thin film deposited top oxide dielectric layer is difficult to control precisely, and that the uniformity of thickness across the area is poor and CMP processing is required to achieve precise dimensions.
Specifically, in step S301, the first thin film deposition grows a top oxide dielectric layer higher than a bottom waveguide layer, and a depth for further depositing and obtaining a modulation layer on top of the bottom waveguide layer is reserved.
Specifically, dry etching is used in step S303.
Specifically, the dry etching includes: plasma etching and reactive ion etching.
Specifically, step S304 further includes high-temperature annealing the buffer layer.
Specifically, step S304 further includes CMP processing for the buffer layer.
Specifically, in step 4, an original modulation layer is formed on top of the buffer layer, including:
s401: depositing a top oxidizing medium layer for the second time on the buffer layer and the top oxidizing medium layer;
s402: marking a pattern to be etched on the top oxidation dielectric layer by using a mask;
s403: etching a top oxidation dielectric layer of a top area of the buffer layer based on the marked pattern to obtain a concave area matched with the target shape of the original modulation layer;
s404: and growing an original modulation layer in the concave area by chemical vapor deposition.
Specifically, the growing of the original modulation layer in step S404 includes: the original modulation layer is prepared by two-step epitaxial growth at different temperatures by chemical vapor deposition.
Specifically, in step S401, the top oxide dielectric layer is grown by thin film deposition for the second deposition of the top oxide dielectric layer.
Preferably, step S301 further includes a CMP process for growing a silicon oxide layer by thin film deposition.
It will be appreciated that the thickness of the thin film deposited top oxide dielectric layer is difficult to control precisely, and that the uniformity of thickness across the area is poor and CMP processing is required to achieve precise dimensions.
Specifically, in step S401, the height of the top oxide dielectric layer grown by the second thin film deposition is higher than that of the buffer layer, and the depth of the modulation layer deposited further on top of the buffer layer is reserved.
Specifically, the growing of the original modulation layer in step S404 includes:
s4041: epitaxially growing the original modulation layer to the thickness of A1 at the temperature T1, and continuously epitaxially growing the original modulation layer to the thickness of A2 at the temperature T2, wherein A2 is more than A1, and T2 is more than T1;
s4042: annealing treatment;
s4043: the thickness after annealing was reduced to A3 by CMP treatment, and A2 > A3 > A1.
Specifically, the thickness range of A1 is 150 nm-300 nm; a2 has a thickness range of 600 nm-1000 nm; a3 has the thickness range of 200 nm-500 nm; the temperature range of T1 is 300-500 ℃; the temperature range of T2 is 700-1000 ℃.
The two-step method is used for growing the original modulation layer, which is helpful for obtaining the high-quality germanium modulation layer.
Specifically, the annealing treatment condition in the step S4042 is 600-1000 ℃ and the treatment is carried out for 30-60 min.
Specifically, in step 5, a germanium hole doped layer, a germanium waveguide layer and a germanium electron doped layer with different doping concentrations are formed on the original modulation layer, which includes:
s501: ion implantation and annealing are carried out on the original modulation layer to form a transverse PIN junction;
s502: and depositing and growing a top oxidation dielectric layer on the PIN junction and the original top oxidation dielectric layer for the third time.
Preferably, the ion implantation concentration of the germanium hole doped layer and the germanium electron doped layer is 1×10 18 cm 3 ～5×10 18 cm 3 。
Preferably, the ion implantation concentration of the germanium hole doped layer and the germanium electron doped layer is 1×10 18 cm 3 、1.2×10 18 cm 3 、1.5×10 18 cm 3 、1.8×10 18 cm 3 、2.2×10 18 cm 3 、2.5×10 18 cm 3 、2.8×10 18 cm 3 、3.0×10 18 cm 3 、3.2×10 18 cm 3 、3.3×10 18 cm 3 、3.5×10 18 cm 3 、3.8×10 18 cm 3 、4.0×10 18 cm 3 、4.2×10 18 cm 3 、4.4×10 18 cm 3 、4.6×10 18 cm 3 、4.8×10 18 cm 3 、5.0×10 18 cm 3 。
Specifically, step 5 further includes forming a top dielectric layer on the top free region and the inner side of the doped layer, the side of the buffer layer, and the top and side of the modulation layer.
Specifically, the top dielectric layer is formed by: CMP to target dimensions after chemical vapor deposition.
Specifically, the top dielectric layer further comprises an electrode grown on the electron strongly doped layer and the hole strongly doped layer after forming, and specifically comprises the following steps:
s601: identifying a desired pattern using the mask;
s602: forming a contact hole between the electron strongly doped layer and the hole strongly doped layer through UV lithography and dry etching processes;
s603: and depositing a metal electrode and performing patterning treatment to obtain the metal electrode with the target shape.
In step S603, the metal electrode comprises a Ti/TiN/Al metal electrode, wherein the Ti electrode is connected with an external power supply; the Al electrode is connected with the electron/hole strong doping layer.
The Ti/TiN/Al metal electrode is connected with the electron strong doping layer and the hole strong doping layer, has lower contact potential barrier and improves the electric control sensitivity.
To further illustrate the advancement of the present invention, the following examples and comparative examples are set forth:
example 1
The embodiment discloses a forming method of an electroabsorption modulator with a germanium modulation layer, comprising the following steps:
step 1: preparing a hole weakly-doped layer, an electron weakly-doped layer, a hole strongly-doped layer and an electron strongly-doped layer on the substrate layer; the ion implantation dosage of the hole weakly doped layer and the electron weakly doped layer is 5 multiplied by 10 18 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The ion implantation dosage of the hole strong doping layer and the electron strong doping layer is 2 multiplied by 10 19 cm 3 Annealing after ion implantation; the substrate layer is a silicon substrate and a silicon oxide dielectric layer;
step 2: plasma etching is adopted for the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer, and a bottom waveguide layer is prepared in the connecting area of the hole weakly doped layer and the electron weakly doped layer;
step 3: depositing a top oxidation dielectric layer for the first time in the etched area; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the waveguide layer based on the marked graph to obtain a concave area matched with the target shape of the buffer layer; chemical vapor deposition is carried out on the concave area to grow a buffer layer; the top oxidation dielectric layer is silicon dioxide; the buffer layer comprises four layers of silicon germanium with the same layer thickness and different combination ratios, and the silicon germanium ratio is respectively as follows according to the arrangement sequence of the buffer layer from top to bottom: 0.1:0.9, 0.3:0.7, 0.6:0.4, 0.8:0.2.
Step 4: depositing a top oxidizing medium layer for the second time on the buffer layer and the top oxidizing medium layer; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the buffer layer based on the marked pattern to obtain a concave area matched with the target shape of the original modulation layer; growing an original modulation layer in the concave region by chemical vapor deposition, depositing to 200nm at a low temperature of 400 ℃, depositing to 1000nm at a high temperature of 850 ℃, annealing for 30min, and performing CMP treatment to 300nm; the top oxidation dielectric layer is silicon dioxide;
step 5: forming germanium electron doped layers with germanium hole doped layers with different doping concentrations on the original modulation layer through ion implantation; the germanium waveguide layer was not ion implanted and the germanium waveguide layer had height and width dimensions of 300nm by 200nm.
Step 6: forming a contact hole with the electrode on the electron/hole strong doping layer through UV lithography and dry etching processes; and depositing Al, tiN, ti in sequence to prepare the Ti/TiN/Al metal electrode.
The embodiment discloses an electroabsorption modulator with a germanium modulation layer, which is prepared by the method, and comprises the following steps: a substrate layer, a doped layer, a buffer layer, a modulation layer and a top oxidation dielectric layer which are sequentially formed from bottom to top; the modulation layer includes: a germanium hole doped layer, a germanium waveguide layer, a germanium electron doped layer; the germanium hole doping layer and the germanium electron doping layer are respectively arranged at two ends of the top of the buffer layer and are connected through the germanium waveguide layer; the top oxidation dielectric layer is formed on the top free region and the inner side surface of the doped layer, the side surface of the buffer layer, the top and the side surface of the modulation layer.
The doping concentration of the hole strong doping layer and the electron strong doping layer is 2 multiplied by 10 19 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The doping concentration of the electron weakly doped layer and the hole weakly doped layer is 5 multiplied by 10 18 cm 3 。
The cross-sectional dimensions of the modulation layer were 300nm by 300nm.
The germanium hole doped layer and the germanium electron doped layer have the same size, are symmetrically arranged relative to the germanium waveguide layer, have the same height as the germanium waveguide layer, and have the doping concentration of 2 multiplied by 10 18 cm 3 。
Example 2
The embodiment discloses a forming method of an electroabsorption modulator with a germanium modulation layer, comprising the following steps:
step 1: preparing a hole weakly-doped layer, an electron weakly-doped layer, a hole strongly-doped layer and an electron strongly-doped layer on the substrate layer; the ion implantation dosage of the hole weakly doped layer and the electron weakly doped layer is 4 multiplied by 10 18 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The ion implantation dosage of the hole strong doping layer and the electron strong doping layer is 1 multiplied by 10 19 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the Annealing after ion implantation; the substrate layer is a silicon substrate and a silicon oxide dielectric layer;
step 2: the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer are etched by using reactive ions, and a bottom waveguide layer is prepared in the connecting area of the hole weakly doped layer and the electron weakly doped layer;
step 3: depositing a top oxidation dielectric layer for the first time in the etched area; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the waveguide layer based on the marked graph to obtain a concave area matched with the target shape of the buffer layer; chemical vapor deposition is carried out on the concave area to grow a buffer layer; the top oxidation dielectric layer is silicon dioxide; the buffer layer comprises six layers of silicon germanium with the same thickness and different combination ratios, and the silicon germanium ratio is respectively as follows according to the arrangement sequence of the buffer layer from top to bottom: 0.1:0.9, 0.2:0.8, 0.3:0.7, 0.5:0.5, 0.6:0.4, 0.8:0.2.
Step 4: depositing a top oxidizing medium layer for the second time on the buffer layer and the top oxidizing medium layer; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the buffer layer based on the marked pattern to obtain a concave area matched with the target shape of the original modulation layer; growing an original modulation layer in the concave region by chemical vapor deposition, depositing to 150nm at the low temperature of 300 ℃, depositing to 600nm at the high temperature of 700 ℃, and performing CMP treatment to 200nm after annealing; the top oxidation dielectric layer is silicon dioxide;
step 5: forming germanium electron doped layers with germanium hole doped layers with different doping concentrations on the original modulation layer through ion implantation; the germanium waveguide layer was not ion implanted and the germanium waveguide layer had height and width dimensions of 200nm x 100nm.
Step 6: forming a contact hole with the electrode on the electron/hole strong doping layer through UV lithography and dry etching processes; and depositing Al/TiN/Ti in sequence to prepare the Ti/TiN/Al metal electrode.
The embodiment discloses an electroabsorption modulator with a germanium modulation layer, which is prepared by the method, and comprises the following steps: a substrate layer, a doped layer, a buffer layer, a modulation layer and a top oxidation dielectric layer which are sequentially formed from bottom to top; the modulation layer includes: a germanium hole doped layer, a germanium waveguide layer, a germanium electron doped layer; the germanium hole doping layer and the germanium electron doping layer are respectively arranged at two ends of the top of the buffer layer and are connected through the germanium waveguide layer; the top oxidation dielectric layer is formed on the top free region and the inner side surface of the doped layer, the side surface of the buffer layer, the top and the side surface of the modulation layer.
The doping concentration of the hole strong doping layer and the electron strong doping layer is 1 multiplied by 10 19 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the Electron weakly doped layer and hole weakly doped layer with doping concentration of 4×10 18 cm 3 。
The cross-sectional dimensions of the modulation layer were 200nm by 200nm.
The germanium hole doped layer and the germanium electron doped layer have the same size, are symmetrically arranged relative to the germanium waveguide layer, have the same height as the germanium waveguide layer, and have the doping concentration of 1 multiplied by 10 18 cm 3 。
Example 3
The embodiment discloses a forming method of an electroabsorption modulator with a germanium modulation layer, comprising the following steps:
step 1: preparing a hole weakly-doped layer, an electron weakly-doped layer, a hole strongly-doped layer and an electron strongly-doped layer on the substrate layer; the ion implantation dosage of the hole weakly doped layer and the electron weakly doped layer is 6 multiplied by 10 18 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The ion implantation dosage of the hole strong doping layer and the electron strong doping layer is 3 multiplied by 10 19 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the Annealing after ion implantation; the substrate layer is a silicon substrate and a silicon oxide dielectric layer;
step 2: plasma etching is adopted for the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer, and a bottom waveguide layer is prepared in the connecting area of the hole weakly doped layer and the electron weakly doped layer;
step 3: depositing a top oxidation dielectric layer for the first time in the etched area; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the waveguide layer based on the marked graph to obtain a concave area matched with the target shape of the buffer layer; chemical vapor deposition is carried out on the concave area to grow a buffer layer; the top oxidation dielectric layer is silicon dioxide; the buffer layer comprises seven layers of silicon carbide with the same layer thickness and different combination ratios, and the carbon-silicon ratios are respectively as follows according to the sequence of the buffer layer from bottom to top: 0.1:0.9, 0.2:0.8, 0.3:0.7, 0.5:0.5, 0.6:0.4, 0.8:0.2, 0.9:0.1.
Step 4: depositing a top oxidizing medium layer for the second time on the buffer layer and the top oxidizing medium layer; marking a pattern to be etched on the top oxidation dielectric layer by using a mask; etching a top oxidation dielectric layer of a top area of the buffer layer based on the marked pattern to obtain a concave area matched with the target shape of the original modulation layer; growing an original modulation layer in the concave region by chemical vapor deposition, depositing to 300nm at the low temperature of 500 ℃, depositing to 1000nm at the high temperature of 1000 ℃, and performing CMP treatment to 500nm after annealing; the top oxidation dielectric layer is silicon dioxide;
step 5: forming germanium electron doped layers with germanium hole doped layers with different doping concentrations on the original modulation layer through ion implantation; the germanium waveguide layer was not ion implanted and the germanium waveguide layer had height and width dimensions of 500nm by 400nm.
Step 6: forming a contact hole with the electrode on the electron/hole strong doping layer through UV lithography and dry etching processes; and sequentially depositing Ti/TiN/Al to prepare the Ti/TiN/Al metal electrode.
The embodiment discloses an electroabsorption modulator with a germanium modulation layer, which is prepared by the method, and comprises the following steps: a substrate layer, a doped layer, a buffer layer, a modulation layer and a top oxidation dielectric layer which are sequentially formed from bottom to top; the modulation layer includes: a germanium hole doped layer, a germanium waveguide layer, a germanium electron doped layer; the germanium hole doping layer and the germanium electron doping layer are respectively arranged at two ends of the top of the buffer layer and are connected through the germanium waveguide layer; the top oxidation dielectric layer is formed on the top free region and the inner side surface of the doped layer, the side surface of the buffer layer, the top and the side surface of the modulation layer.
The doping concentration of the hole strong doping layer and the electron strong doping layer is 3 multiplied by 10 19 cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The doping concentration of the electron weakly doped layer and the hole weakly doped layer is 6 multiplied by 10 18 cm 3 。
The cross-sectional dimensions of the modulation layer were 500nm by 500nm.
The germanium hole doped layer and the germanium electron doped layer have the same size, are symmetrically arranged relative to the germanium waveguide layer, have the same height as the germanium waveguide layer, and have the doping concentration of 5 multiplied by 10 18 cm 3 。
Example 4
This embodiment discloses a method for forming an electroabsorption modulator having a germanium modulation layer, which is unique from embodiment 1 in that: the buffer layer comprises five layers of gallium nitride with different combination ratios, and the ratio of the gallium nitride is respectively as follows according to the arrangement sequence of the buffer layer from bottom to top: 0.1:0.9, 0.3:0.7, 0.5:0.5, 0.8:0.2, 0.9:0.1.
Example 5
This embodiment discloses a method for forming an electroabsorption modulator having a germanium modulation layer, which is unique from embodiment 1 in that: the buffer layer comprises four layers of silicon germanium with the same layer thickness and different combination ratios, and the silicon germanium ratio is respectively as follows according to the sequence of the buffer layer from bottom to top: 0.1:0.9, 0.3:0.7, 0.6:0.4, 0.8:0.2.
Example 6
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the buffer layer is only provided with a layer of silicon germanium, and the molar ratio of the silicon germanium is as follows: 0.5:0.5.
Comparative example 1
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the buffer layer thickness of comparative example 1 was replaced by an increase in the electron weakly doped layer and the hole weakly doped layer by an equal amount without providing a buffer layer.
Comparative example 2
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the original modulation layer was formed to 1000nm in one step at 400 c, annealed for 30min and then CMP to 300nm, the remaining conditions being the same as in example 1.
Comparative example 3
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the original modulation layer was formed to 1000nm in one step at 850 c, annealed for 30min and then CMP to 300nm, the remaining conditions being the same as in example 1.
Comparative example 4
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: depositing to 200nm at 400 ℃ with the same low temperature as in example 1, depositing to 300nm at 850 ℃ with the high temperature of example 1, annealing, and carrying out no CMP treatment process; the other conditions were the same as in example 1.
Comparative example 5
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the modulation layer width was 100nm, and the other conditions were the same as in example 1.
Comparative example 6
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the modulation layer width was 500nm, and the other conditions were the same as in example 1.
Comparative example 7
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the modulation layer height was 100nm, and the other conditions were the same as in example 1.
Comparative example 8
The embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, the only difference is: the modulation layer height was 600nm, and the other conditions were the same as in example 1.
Comparative example 9
This embodiment discloses an electroabsorption modulator with germanium modulation layer and its forming method, compared with embodiment 1, as shown in fig. 7, the only difference is: the doped layer is not provided with a hole weakly doped layer and an electron weakly doped layer, the region between the hole strongly doped layer and the electron strongly doped layer is not doped, and the other conditions are the same as in example 1.
Experimental example
The photoelectric modulation performance test was performed on examples 1 to 6 and comparative examples 1 to 9, and the test results were as follows:
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conclusion of experiment:
from the above table, it can be seen that: examples 1-3 and 5 can realize the change of working wavelength from 1550nm to 1560nm, the change of modulation speed from 40Gbps to 56Gbps, the change of modulation bandwidth from 55GHz to 67GHz, and the change of insertion loss from 4.0dB to 7.9 dB.
As can be seen from comparison of examples 1 and 5, the buffer layer reverse gradient arrangement has a larger operating wavelength, modulation speed and modulation bandwidth than the forward gradient arrangement, and the insertion loss is smaller.
Comparative example 1 and comparative example 1 show that comparative example 1 without a buffer layer has a smaller operating wavelength and a larger loss.
As can be seen from comparative example 1 and comparative examples 2 and 3, the modulator obtained by the method for preparing a modulation layer according to example 1 has a larger operating wavelength, modulation speed and modulation bandwidth, and has a smaller insertion loss. As can be seen from comparative examples 1 and 4, the modulator obtained by the method for preparing a modulation layer according to example 1 has a larger operating wavelength, modulation speed and modulation bandwidth, and has a smaller insertion loss.
As is clear from comparative example 1 and comparative examples 5 and 6, the modulation layer width is too large or too small, and the modulation speed, modulation bandwidth and insertion loss are deteriorated to some extent.
As is clear from comparative example 1 and comparative examples 7 and 8, the modulation layer height was too large or too small, and the modulation speed, modulation bandwidth and insertion loss were deteriorated to some extent.
As can be seen from comparative examples 1 and 9, the arrangement of the hole weakly doped layer and the electron weakly doped layer helps to optimize the modulation speed, the modulation bandwidth and the insertion loss, and improves the control sensitivity.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. An electro-absorption modulator having a germanium modulation layer, comprising:
a substrate layer comprising a back substrate and a bottom oxide dielectric layer disposed on the silicon substrate;
a doped layer formed on top of the bottom oxidation mediating layer, comprising: a hole strongly doped layer, a hole weakly doped layer, an electron strongly doped layer; the hole weakly doped layer and the electron weakly doped layer are protruded in the middle area of the top of the bottom oxidation dielectric layer and connected to form a PN junction, and are used as bottom waveguide layers; the hole strong doping layer and the electron strong doping layer are respectively arranged at the two ends of the top of the bottom oxidation dielectric layer, the hole strong doping layer is connected with the hole weak doping layer, and the electron weak doping layer is connected with the electron strong doping layer;
the buffer layer is formed on the top of the PN junction;
a modulation layer formed on top of the buffer layer; comprising the following steps: a germanium hole doped layer, a germanium waveguide layer, a germanium electron doped layer; the germanium hole doping layer and the germanium electron doping layer are respectively arranged at two ends of the top of the buffer layer and are connected through the germanium waveguide layer;
and the top oxidation dielectric layer is formed on the top free region and the inner side surface of the doped layer, the side surface of the buffer layer and the top and the side surface of the modulation layer.
2. The electro-absorption modulator of claim 1, wherein the buffer layer comprises a single layer or multiple layers.
3. The electro-absorption modulator of claim 2, wherein the single buffer layer is comprised of one two-component compound and the multiple buffer layers are comprised of two-component compounds of different component content.
4. The electro-absorption modulator according to claim 3, wherein the ratio of the two components of each layer of the two-component compound in the multi-layer buffer layer is changed according to a forward gradient or a reverse gradient; wherein, the general formula of the two-component compound is as follows: a is that 1-x B x Wherein A, B represents a two-component compound constituent element; x is less than or equal to 1, and represents the atomic number of the element B in the two-component compound.
5. The electro-absorption modulator according to claim 4, wherein the two-component compound formula is: the multi-layer buffer layers are marked as follows in the molding sequence from bottom to top: a first buffer layer, …, an nth buffer layer; the two-component compound of the N buffer layer has the general formula A (1-x) N B x N The two-component compound of the N-1 buffer layer has the general formula A (1-x) N-1 B x N-1 ， x N-1 ＜ x N Or (b) x N-1 ＞ x N The method comprises the steps of carrying out a first treatment on the surface of the Wherein A, B represents a constituent element of a two-component compound,x N representing the atomic number of the two-component compound element B of the N buffer layer, (-) 1-x ) N The atomic number of the two-component compound element a of the nth buffer layer is represented.
6. The electro-absorption modulator of claim 1, wherein the doping concentration of the germanium-hole doped layer and the germanium-electron doped layer is 1 x 10 18 cm 3 ～5×10 18 cm 3 。
7. The electro-absorption modulator of claim 6, wherein the germanium waveguide layer has a width of 100nm to 400nm and a height of 200nm to 500nm.
8. The electro-absorption modulator of claim 7, wherein the operating wavelength is 1540nm to 1560nm.
9. The electro-absorption modulator of claim 1, wherein the buffer layer comprises: a group III, group V and group IV semiconductor compound, and a group IV, group V and group V semiconductor compound.
10. A method of forming an electroabsorption modulator having a germanium modulation layer, comprising:
step 1: preparing doped layers with different doping concentrations on the substrate layer;
step 2: etching the hole weakly doped layer and the electron weakly doped layer in the middle area of the doped layer, and preparing a bottom waveguide layer in the connecting area of the hole weakly doped layer and the electron weakly doped layer;
step 3: forming a buffer layer on top of the bottom waveguide layer;
step 4: forming an original modulation layer on top of the buffer layer;
step 5: and forming a germanium hole doped layer, a germanium waveguide layer and a germanium electron doped layer with different doping concentrations on the original modulation layer.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117389071A (en) * | 2023-12-13 | 2024-01-12 | 众瑞速联（武汉）科技有限公司 | PN junction doped structure, low-loss electro-optical modulator and preparation method thereof |
| CN117406472A (en) * | 2023-12-14 | 2024-01-16 | 希烽光电科技(南京)有限公司 | Silicon light modulator |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117389071A (en) * | 2023-12-13 | 2024-01-12 | 众瑞速联（武汉）科技有限公司 | PN junction doped structure, low-loss electro-optical modulator and preparation method thereof |
| CN117389071B (en) * | 2023-12-13 | 2024-03-29 | 众瑞速联（武汉）科技有限公司 | PN junction doped structure, low-loss electro-optical modulator and preparation method thereof |
| CN117406472A (en) * | 2023-12-14 | 2024-01-16 | 希烽光电科技(南京)有限公司 | Silicon light modulator |
| CN117406472B (en) * | 2023-12-14 | 2024-03-22 | 希烽光电科技(南京)有限公司 | Silicon light modulator |
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