CN111192891A - Silicon photodetector, distance measuring method and device - Google Patents
Silicon photodetector, distance measuring method and device Download PDFInfo
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The application provides a silicon photodetector, a distance measuring method and a distance measuring device, and relates to the technical field of image sensors. The silicon photodetector includes: a detector and a light-enhancing absorption array; the detector is used for receiving the optical signal and generating an electric signal; the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on the optical signal, wherein the geometric structure of the optical enhancement absorption array is obtained on the basis of the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector. The light enhancement absorption array is arranged on the surface of the detector of the silicon photodetector, so that the surface plasmon resonance phenomenon can be generated on the surface of the detector of the silicon photodetector, the integral extinction ratio of the silicon photodetector is increased, the light absorption of the silicon photodetector in a near infrared waveband is enhanced, the photoelectric conversion efficiency of the silicon photodetector in the near infrared waveband is enhanced, and the quantum efficiency is effectively improved.
Description
Technical Field
The invention relates to the technical field of image sensors, in particular to a silicon photodetector, a distance measuring method and a distance measuring device.
Background
Silicon-based materials have recently been widely used in the field of image sensors due to their compatibility with CMOS (Complementary Metal Oxide Semiconductor) manufacturing processes and low cost properties. Generally, a silicon-based material is an indirect bandgap semiconductor material, and due to a limit that its energy band gap is 1.2eV, the quantum efficiency of a silicon material-based Image Sensor (CMOS Image Sensor) in the near infrared band is greatly reduced. For a TOF (time of Flight ranging) device based on silicon, since an active light source of the TOF device is generally a near infrared band, a TOF chip has a large ranging error due to too low quantum efficiency in the band, and how to improve the quantum efficiency of a silicon-based material becomes especially important.
In the prior art, the light absorption can be increased by increasing the thickness of the epitaxial layer, thereby improving the quantum efficiency, but the method can cause the crosstalk between the pixels of the sensor chip to increase. Although the DTI (diffusion tensor imaging) can alleviate the crosstalk to some extent, the process difficulty of the whole pixel preparation process is increased by the deep DTI process. In addition, reflection can be reduced and absorption can be increased by introducing a black silicon process of a pyramid structure into the silicon surface, but the process also causes serious optical crosstalk inside the image element of the image sensor chip, and a deep DTI technology is still needed to reduce isolation crosstalk.
Disclosure of Invention
The present invention aims to provide a silicon photodetector, a distance measuring method and a distance measuring device, which are used for solving the problems of the prior art that the silicon photodetector has poor light absorption efficiency and low quantum rate, which results in low accuracy of the distance measuring result.
In order to achieve the above purpose, the technical solutions adopted in the embodiments of the present application are as follows:
in a first aspect, an embodiment of the present application provides a silicon photodetector, including: a detector and a light-enhancing absorption array;
the detector is used for receiving the optical signal and generating an electric signal;
the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on an optical signal, wherein the geometrical structure of the optical enhancement absorption array is obtained based on the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector.
Optionally, the light-enhancing absorption array comprises at least one protruding entity, or, at least one hollow cavity; the geometrical structure of the convex entity comprises a symmetrical structure or an asymmetrical structure, and the geometrical structure of the hollow cavity comprises a symmetrical structure or an asymmetrical structure.
Optionally, the geometry of the light-enhanced absorption array comprises at least an array of silicon rings, or an array of silicon cylinders.
Optionally, the light-enhanced absorption array is the silicon ring array; the inner diameter, the outer diameter and the thickness of each silicon ring are obtained according to the absorptivity of the optical signal by the detector.
Optionally, the light-enhanced absorption array is the silicon cylinder array; the radius and thickness of each silicon cylinder are obtained from the absorptivity of the optical signal by the detector.
Optionally, the absorptivity of the optical signal by the detector is calculated according to the structure of the optical enhancement absorption array, the reflectivity and the refractive index of the detector and the optical enhancement absorption array.
Optionally, when the thickness of each silicon ring in the silicon ring array is 20nm, the outer diameter is 280nm, and the inner diameter is 170nm, for 940nm optical signals, the distance between the silicon rings is 1500 nm.
Optionally, when the thickness of the silicon cylinder is 20nm and the radius is 180nm, for 940nm of the optical signal, the distance between the silicon rings is 1400 nm.
In a second aspect, an embodiment of the present application further provides a distance measuring method applied to the silicon photodetector described in the first aspect, where the method includes:
generating an electrical signal according to an optical signal received by the silicon photodetector;
acquiring signal parameters output by the detector according to the electric signals;
and calculating the distance between the detector and the target object according to the signal parameters.
In a third aspect, an embodiment of the present application further provides a ranging apparatus, which is applied to the ranging method in the second aspect, and the apparatus includes: the device comprises a signal generating module, an obtaining module and a calculating module;
the signal generation module is used for generating an electric signal according to the optical signal received by the silicon photodetector;
the acquisition module is used for acquiring signal parameters output by the detector according to the electric signals;
and the calculation module is used for calculating the distance between the detector and the target object according to the signal parameters.
The beneficial effect of this application is:
the embodiment of the application provides a silicon photodetector, a distance measurement method and a distance measurement device, wherein the silicon photodetector comprises a detector and a light-enhanced absorption array; the detector is used for receiving the optical signal and generating an electric signal; the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on the optical signal, wherein the geometric structure of the optical enhancement absorption array is obtained on the basis of the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector. The light enhancement absorption array is arranged on the surface of the detector of the silicon photodetector, so that the surface plasmon resonance phenomenon can be generated on the surface of the detector of the silicon photodetector, the integral extinction ratio of the silicon photodetector is increased, the light absorption of the silicon photodetector in a near infrared band is enhanced, the photoelectric conversion efficiency of the silicon photodetector in the near infrared band (especially to the near infrared band with the wavelength of about 900 nm) is enhanced, and the quantum efficiency is effectively improved.
The geometrical structure of the light-enhanced absorption array can comprise a silicon ring array or a silicon cylinder array. When the geometric structure of the light-enhanced absorption array is a silicon ring array, the thickness of each silicon ring in the silicon ring array is 20nm, the outer diameter is 280nm, and the inner diameter is 170nm, for 940nm optical signals, the distance between the silicon rings is 1500nm, the light absorption effect of the silicon photodetector is good, so that the photoelectric conversion efficiency is high, and the quantum rate is high. When the geometric structure of the light enhancement absorption array is a silicon cylinder array, the thickness of the silicon cylinder is 20nm, the radius of the silicon cylinder is 180nm, and for 940nm optical signals, when the distance between silicon rings is 1400nm, the light absorption effect of the silicon photodetector is good, so that the photoelectric conversion efficiency is high, and the quantum rate is high.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic top view of a silicon photodetector according to an embodiment of the present application;
FIG. 2 is a schematic side view of a silicon photodetector according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a light-enhanced absorption array according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of waveforms illustrating the effect on detector optical properties in the presence/absence of an enhanced absorption array according to embodiments of the present disclosure;
FIG. 5 is a schematic diagram of waveforms illustrating variations in different optical properties of a detector with/without an enhanced absorption array according to an embodiment of the present disclosure;
FIG. 6 is a waveform illustrating a variation in geometry of a photo-enhanced absorption array and a variation in optical properties of a detector according to an embodiment of the present disclosure;
FIG. 7 is a schematic diagram of waveforms illustrating variations in the spacing of the geometric structures and optical properties of the detector in the photo-enhanced absorption array at a specific size according to an embodiment of the present disclosure;
FIG. 8 is a schematic structural diagram of another light-enhancing absorption array provided in the embodiments of the present application;
FIG. 9 is a schematic diagram of waveforms illustrating the effect on detector optical properties in the presence/absence of an enhanced absorption array according to an embodiment of the present disclosure;
FIG. 10 is a schematic diagram of waveforms illustrating variations in different optical properties of another detector with/without an enhanced absorption array according to an embodiment of the present disclosure;
FIG. 11 is a schematic diagram of waveforms illustrating the dimensional change of a photo-enhanced absorption array and the change of optical properties of a detector according to an embodiment of the present application;
FIG. 12 is a schematic diagram showing waveforms of variations in the geometrical spacing and optical properties of the detector in the photo-enhanced absorption array at another specific size according to the embodiments of the present application;
fig. 13 is a schematic flowchart of a distance measuring method according to an embodiment of the present disclosure;
fig. 14 is a schematic structural diagram of a distance measuring device according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic top view of a silicon photodetector according to an embodiment of the present application; fig. 2 is a schematic side view of a silicon photodetector according to an embodiment of the present disclosure. Please refer to fig. 1 and 2 for understanding. The silicon photodetector includes: a detector and a light-enhancing absorption array; the detector 110 is used for receiving the optical signal and generating an electrical signal; the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on the optical signal, wherein the geometric structure of the optical enhancement absorption array is obtained on the basis of the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector.
First, the principle that the light-enhancing absorption array increases the absorption of the light signal by the detector needs to be explained to facilitate better understanding of the technical points of the present invention.
Alternatively, a surface plasmon phenomenon is explained first, and the surface plasmon is collective oscillation formed under the interaction of free charges on the surface of the material with an external electric field and an optical field, and propagates along the surface of the material. For a bulk material (approximately 10 wavelengths greater in size), the frequency of oscillation is shown in equation 1:
wherein ω isspFrequency, ω, of surface plasmonspFor this purpose the plasma oscillation frequency of the material, epsilonmAnd εdThe complex dielectric constants of the material and the surrounding medium, respectively.
For the structure of the material surface propagation similar to the incident light wavelength (about 0.1-10 times wavelength), the oscillation of the surface plasmon is limited to the reciprocating oscillation on the object surface. The oscillation frequency is related to the size, geometry, material, wavelength of incident light, etc. of the object. The stronger the localized surface plasmon resonance, the stronger its near field enhancement, and the more energy will be localized in the near field, either transferred to nearby materials or dissipated as heat, resulting in an increase in its extinction cross-section. For a sphere, its extinction cross-section σextCan be expressed as the following equation 2:
wherein c is the speed of light, V is the volume of the sphere, εdIs the dielectric constant of the surrounding medium, epsilon'mOmega and epsilon "m(ω) represents the real and imaginary parts of the dielectric constant of the sphere material, i.e.. epsilon.)m(ω)＝ε'm(ω)+iε”m(ω). So when epsilon'm(ω)+2εdAt 0, its extinction cross-section is largest, meaning that the most energy is localized at the structure surface rather than being reflected or transmitted.
That is, in this application scheme, through set up the light enhancement absorption array on silicon light detector's detector surface, can produce surface plasmon resonance phenomenon on silicon light detector's detector surface to increased the holistic extinction proportion of silicon light detector, strengthened the light absorption of silicon light detector at near-infrared wave band, strengthened the photoelectric conversion efficiency of silicon light detector at near-infrared wave band, thereby effectively promote quantum efficiency.
As shown in fig. 1, the light-enhanced absorption array may include different structures, and optionally, the structure of the light-enhanced absorption array may be determined according to the wavelength band information of the light signal received by the silicon photodetector and the optical properties of the material of the detector under the light signal. The determination of the geometry of the light-enhancing absorbing array can be understood by the following specific examples.
Alternatively, fig. 1 only shows an exemplary shape of each structure in the light-enhanced absorption array, that is, a circle, and in an actual arrangement process, the shape of each structure in the light-enhanced absorption array may not be limited to a circle, but may also be various polygons such as a circle, a square, a pentagon, and a hexagon.
In summary, the silicon photodetector provided in this embodiment includes a detector and a light-enhanced absorption array; the detector is used for receiving the optical signal and generating an electric signal; the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on the optical signal, wherein the geometric structure of the optical enhancement absorption array is obtained on the basis of the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector. The light enhancement absorption array is arranged on the surface of the detector of the silicon photodetector, and the surface plasmon resonance phenomenon can be generated on the surface of the detector of the silicon photodetector, so that the integral extinction ratio of the silicon photodetector is increased, the light absorption of the silicon photodetector in a near infrared waveband is enhanced, the photoelectric conversion efficiency of the silicon photodetector in the near infrared waveband is enhanced, the quantum efficiency is effectively improved, the array is arranged in a sensor, and the working efficiency and accuracy of the sensor are guaranteed.
Optionally, the light-enhancing absorbing array comprises at least one protruding entity, or, at least one hollow cavity; the geometrical structure of the convex solid body comprises a symmetrical structure or an asymmetrical structure, and the geometrical structure of the hollow cavity comprises a symmetrical structure or an asymmetrical structure.
Optionally, when the convex solid or the hollow cavity is a non-circular or non-regular polygon, the geometric structure of the convex solid or the hollow cavity is an asymmetric structure, and when the convex solid or the hollow cavity is a circular or regular polygon, the geometric structure of the convex solid or the hollow cavity is a symmetric structure. In particular, whether the geometrical structure of the convex solid or the hollow cavity is a symmetrical structure or an asymmetrical structure, the absorption of the light signal by the detector can be enhanced.
Optionally, the geometry of the light-enhancing absorption array comprises at least an array of silicon rings, or, an array of silicon cylinders.
In the embodiments of the present application, the geometric structure of the light-enhanced absorption array is exemplified by a silicon ring array or a silicon cylinder array.
Fig. 3 is a schematic structural diagram of a light-enhanced absorption array according to an embodiment of the present disclosure. Alternatively, as shown in FIG. 3, the light-enhancing absorbing array is a silicon ring array; the inner diameter, the outer diameter and the thickness of each silicon ring are obtained according to the absorptivity of the detector to light signals, a dimensional design basis is provided through absorptivity simulation or experimental value optimization, the highest efficiency of light quantum conversion after light absorption of the whole array in the using process is guaranteed, the refractive index or the transmissivity of the detector can indirectly reflect the absorptivity of the detector, for example, the array enhancing method is used for reducing at least one value of the transmissivity or the refractive index, and then the higher absorptivity is obtained.
Fig. 4 is a waveform diagram illustrating the influence of the light with/without the enhanced absorption array on the optical properties of the detector according to the embodiment of the present application. Fig. 5 is a schematic diagram of waveforms of different optical properties of a detector with/without an optical enhancement absorption array according to an embodiment of the present disclosure.
The above waveform schematic diagram can be obtained by performing simulation on performance parameters and the like of the detector provided with the light-enhanced absorption array by using finite element software (COMSOL Multiphysics), where the optical properties of the detector may include: reflectance, transmittance, absorbance, and absolute absorbance. The absolute absorption rate is an absorption rate without taking reflection into consideration. Optionally, the absorbance of the optical signal by the detector is calculated according to the structure of the optical enhancement absorption array, the reflectivity and the refractive index of the detector and the optical enhancement absorption array.
Specifically, fig. 4(1) is a waveform diagram illustrating the reflectivity, transmittance, absorptance and absolute absorptance of a detector in the case of a non-light-enhanced absorption array; fig. 4(2) is a waveform diagram illustrating reflectivity, transmissivity, absorptivity and absolute absorptivity of the detector under the condition of the light-enhanced absorption array. In fig. 4(1) and 4(2), curve 1 represents transmittance, curve 2 represents reflectance, curve 3 represents absorptance, and curve 4 represents absolute transmittance.
As can be derived from fig. 4, the reflectivity and transmission of the detector are reduced with the light-enhanced absorbing array relative to that without the light-enhanced absorbing array; the absorption rate and absolute absorption rate of the detector are increased relative to those of the absorption array without light enhancement. That is, after the detector surface of the silicon photodetector of the present application is provided with the light enhancement absorption array, the detector absorbs light signals more strongly, so that the photoelectric conversion efficiency can be effectively improved, and the quantum efficiency is further improved.
Specifically, fig. 5(1) is a graph showing a waveform of a change in transmittance in the presence/absence of the absorption enhancing array; FIG. 5(2) is a graph showing the variation of reflectivity with/without the enhanced absorption array; FIG. 5(3) is a graph showing the variation of absorbance with/without an enhanced absorption array; fig. 5(4) is a waveform diagram showing the variation of absolute absorption rate in the case of the absorption array with/without light enhancement. In fig. 5(1), 5(2), 5(3), 5(4), curves 1 and 2 all represent non-light-enhanced absorption arrays and light-enhanced absorption arrays.
Wherein, at a wavelength of 940nm, the changes of the reflectivity, the transmissivity, the absorptivity and the absolute absorptivity are shown in the following table 1:
it can further be shown that in the presence of the light-enhancing absorption array, the reflectivity and transmissivity of the detector are reduced and the absorption and absolute absorption are improved.
Fig. 6 is a waveform diagram illustrating a geometric dimension variation of a photo-enhanced absorption array and an optical property variation of a detector according to an embodiment of the present disclosure. Fig. 6(1) is a schematic diagram of the geometric size variation and transmittance variation waveforms of the photo-enhanced absorption array; FIG. 6(2) is a schematic diagram showing the geometrical size variation and reflectivity variation waveforms of the photo-enhanced absorption array; FIG. 6(3) is a waveform illustrating the variation of the geometrical dimension and the variation of the absolute absorption rate of the photo-enhanced absorption array; fig. 6(4) is a schematic diagram of the geometrical dimension variation and absorption rate variation waveforms of the photo-enhanced absorption array. Wherein, the geometric dimension change of the light-enhanced absorption array is correspondingly generated for the optical signal with the wavelength of 940 nm.
Through numerical simulation and theoretical calculation, it can be seen that when the parameters of the inner diameter and the outer diameter of each silicon ring in the light-enhanced absorption array are changed, the light reflectivity, the light transmissivity and the light absorptivity of the light-enhanced absorption array are different from each other at the wavelength of 940nm, and the light reflectivity, the light transmissivity and the light absorptivity are in an up-and-down state. Wherein, when the outer diameter radius is 280nm, the absorbance (0.755) and the absolute absorbance (0.523) reach maximum values.
Optionally, in some embodiments, the spacing between each of the geometric structures in the light-enhancing absorption array also affects the light absorption rate of the detector to some extent. Taking the photo-enhanced absorption array as an example of a silicon ring array, when the distance between every two silicon rings in the photo-enhanced absorption array is changed, the absorption rate and the absolute absorption rate of the detector for infrared light are changed, and different silicon ring distances correspond to different resonance wavelengths. Through numerical simulation and theoretical calculation, the absorption intensity of infrared light with the wavelength of 940nm is calculated when the distance between the silicon rings is changed.
Fig. 7 is a waveform illustrating variations in the geometrical spacing and optical properties of the detector in the photo-enhanced absorption array at a specific size according to an embodiment of the present disclosure. Wherein, the thickness of the silicon ring in the photo-enhanced absorption array is 20nm, the outer diameter is 280nm, and the inner diameter is 170nm, that is, fig. 7 is a schematic diagram of the variation waveform of the absorption rate and the absolute absorption rate of the photo-enhanced absorption array for the infrared light with wavelength 940nm when the thickness of the silicon ring in the photo-enhanced absorption array is 20nm, the outer diameter is 280nm, and the inner diameter is 170 nm. Where curve 1 represents the absorbance and curve 2 represents the absolute absorbance.
When the reflection generated by the surface of the detector is considered, the interval between the silicon rings in the light enhancement absorption array is 600-1520nm, when the interval is 1500nm, the absorptivity of the detector for 940nm wavelength infrared light reaches the maximum and is 62.46%, and when the reflection generated by the surface of the detector is not considered, the absolute absorptivity of the detector for 940nm wavelength infrared light is close to 84.49%.
In summary, in order to enhance the absorption of the silicon photodetector for near infrared light, the distance between the silicon photodetector and the light-enhanced absorption array needs to be calculated when the light-enhanced absorption array is fabricated, and different wavelengths have their corresponding size distances, and the absorption for the required infrared light is reduced when the distance is larger or smaller than the distance. The computational logic may also be preset in the machine, particularly during design and fabrication, for computer aided manufacturing purposes.
As can be seen from the analysis of the above simulation experiment results, in this embodiment, when the thickness of each silicon ring in the silicon ring array is 20nm, the outer diameter is 280nm, and the inner diameter is 170nm, and for 940nm optical signals, the distance between the silicon rings is 1500nm, the light absorption effect of the silicon photodetector is better, so that the photoelectric conversion efficiency is higher, and the quantum rate is higher.
Optionally, the light-enhancing absorbing array is a silicon cylindrical array; the radius and thickness of each silicon cylinder are obtained according to the absorptivity of the detector to the optical signal.
Fig. 8 is a schematic structural diagram of another light-enhanced absorption array provided in an embodiment of the present application. Alternatively, as shown in fig. 8, the light-enhancing absorbing array is a silicon cylindrical array; wherein, the radius and the thickness of each silicon cylinder are obtained according to the absorptivity of the detector to the optical signal.
Fig. 9 is a waveform diagram illustrating the influence of the light on the optical properties of a detector in the presence/absence of an enhanced absorption array according to an embodiment of the present disclosure. Fig. 10 is a schematic diagram of waveforms of different optical properties of another detector provided in the embodiments of the present application with/without an optical enhancement absorption array.
In particular, the study procedure is similar to that when the light-enhanced absorption array is a silicon ring array. FIG. 9(1) is a graph showing the reflectivity, transmissivity, absorptivity and absolute absorptivity waveforms of a detector in the absence of a light-enhanced absorption array; fig. 9(2) is a waveform diagram illustrating reflectivity, transmissivity, absorptivity and absolute absorptivity of the detector in the presence of the light-enhanced absorption array. In fig. 9(1) and 9(2), curve 1 represents transmittance, curve 2 represents reflectance, curve 3 represents absorptance, and curve 4 represents absolute absorptance.
As can be derived from fig. 9, the reflectivity and transmission of the detector are reduced with the light-enhanced absorbing array relative to that without the light-enhanced absorbing array; the absorption rate and absolute absorption rate of the detector are increased relative to those of the absorption array without light enhancement.
FIG. 10(1) is a graph showing the waveform of transmittance with/without the presence of the optical enhancement absorption array; FIG. 10(2) is a graph showing the variation of reflectivity with/without the enhanced absorption array; FIG. 10(3) is a graph showing the variation of absorbance with/without an enhanced absorption array; fig. 10(4) is a waveform diagram showing the variation of absolute absorption rate in the case of the absorption array with/without light enhancement. In fig. 10(1), 10(2), 10(3), 10(4), curves 1 and 2 all show non-light-enhanced absorption arrays and light-enhanced absorption arrays.
Wherein, at a wavelength of 940nm, the changes of the reflectivity, the transmissivity, the absorptivity and the absolute absorptivity are shown in the following table 2:
it can also be shown that in the presence of the light-enhancing absorption array, the reflectivity and transmissivity of the detector are reduced and the absorptivity and absolute absorptivity are improved.
Fig. 11 is a waveform diagram illustrating a geometric dimension variation and a detector optical property variation of another photo-enhanced absorption array according to an embodiment of the present disclosure. Fig. 11(1) is a schematic diagram of the geometric size variation and transmittance variation waveforms of the photo-enhanced absorption array; FIG. 11(2) is a schematic diagram showing the geometrical size variation and reflectivity variation waveforms of the photo-enhanced absorption array; FIG. 11(3) is a waveform illustrating the variation of the geometrical dimension and the variation of the absolute absorption rate of the photo-enhanced absorption array; fig. 11(4) is a schematic diagram of the geometrical dimension variation and absorption rate variation waveforms of the photo-enhanced absorption array. Wherein, the geometric dimension change of the light-enhanced absorption array is correspondingly generated for the optical signal with the wavelength of 940 nm.
Through numerical simulation and theoretical calculation, it can be seen that when the inner and outer diameter parameters of the light enhancement absorption array are changed, the light reflectivity, the light transmissivity and the light absorptivity of the light enhancement absorption array are different from each other at the wavelength of 940nm, and the light reflectivity, the light transmissivity and the light absorptivity are in an up-and-down state. The absolute absorbance (0.723) can be significantly enhanced when the outer diameter radius is 80nm, and the absorbance (relative absorbance) reaches the highest (0.812) when the outer diameter radius is 240 nm.
FIG. 12 is a waveform illustrating variations in the geometrical spacing and optical properties of the detector in the photo-enhanced absorption array at another specific dimension according to an embodiment of the present disclosure. Wherein, the thickness of the silicon cylinder in the optical enhancement absorption array is 20nm, and the radius is 180nm, that is, fig. 12 is a schematic diagram of variation waveforms of the absorption rate and the absolute absorption rate of the optical enhancement absorption array for 940nm wavelength infrared light when the thickness of the silicon cylinder in the optical enhancement absorption array is 20nm and the radius is 180 nm. Where curve 1 represents the absorbance and curve 2 represents the absolute absorbance.
When the reflection generated on the surface of the detector is considered, when the distance between the silicon cylinders in the light enhancement absorption array is 1220nm, the absorption rate of the detector to 940nm wavelength infrared light reaches the maximum value, which is 79.45%; when the silicon cylinders in the light-enhanced absorption array have the same size and reflection generated on the surface of the detector is not considered, when the distance between the silicon cylinders in the light-enhanced absorption array is 1400nm, the absolute absorption rate of the detector to 940nm wavelength infrared light is maximum and is 94.76%.
As can be seen from the analysis of the simulation experiment result performed on the silicon cylindrical array by using the light-enhanced absorption array, in this embodiment, the thickness of the silicon cylindrical array is 20nm, the radius is 180nm, and for 940nm optical signals, when the distance between the silicon rings is 1400nm, the light absorption effect of the silicon photodetector is good, so that the photoelectric conversion efficiency is high, and the quantum rate is high.
In summary, the silicon photodetector provided in the embodiment of the present application includes a detector and a light-enhanced absorption array; the detector is used for receiving the optical signal and generating an electric signal; the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on the optical signal, wherein the geometric structure of the optical enhancement absorption array is obtained on the basis of the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector. The light enhancement absorption array is arranged on the surface of the detector of the silicon photodetector, so that the surface plasmon resonance phenomenon can be generated on the surface of the detector of the silicon photodetector, the integral extinction ratio of the silicon photodetector is increased, the light absorption of the silicon photodetector in a near infrared waveband is enhanced, the photoelectric conversion efficiency of the silicon photodetector in the near infrared waveband is enhanced, and the quantum efficiency is effectively improved.
The geometrical structure of the light-enhanced absorption array can comprise a silicon ring array or a silicon cylinder array. When the geometric structure of the light-enhanced absorption array is a silicon ring array, the thickness of each silicon ring in the silicon ring array is 20nm, the outer diameter is 280nm, and the inner diameter is 170nm, for 940nm optical signals, the distance between the silicon rings is 1500nm, the light absorption effect of the silicon photodetector is good, so that the photoelectric conversion efficiency is high, and the quantum rate is high. When the geometric structure of the light enhancement absorption array is a silicon cylinder array, the thickness of the silicon cylinder is 20nm, the radius of the silicon cylinder is 180nm, and for 940nm optical signals, when the distance between silicon rings is 1400nm, the light absorption effect of the silicon photodetector is good, so that the photoelectric conversion efficiency is high, and the quantum rate is high.
Fig. 13 is a schematic flowchart of a distance measuring method according to an embodiment of the present application, and optionally, the distance measuring method employs the silicon photodetector described above, and an execution subject of the method may be the silicon photodetector. As shown in fig. 13, the method may include:
and S101, generating an electric signal according to the optical signal received by the silicon photodetector.
And S102, acquiring signal parameters output by the detector according to the electric signals.
And S103, calculating the distance between the detector and the target object according to the signal parameters.
Optionally, when the distance measuring method is performed by using the silicon photodetector, the implementation principle and technical effect thereof are similar to those of the silicon photodetector, and are not described herein again.
Fig. 14 is a schematic structural diagram of a distance measuring device according to an embodiment of the present disclosure, where the distance measuring device may include a signal generating module 201, an obtaining module 202, and a calculating module 203.
A signal generating module 201, configured to generate an electrical signal according to a light signal received by the silicon photodetector;
the acquisition module 202 is used for acquiring signal parameters output by the detector according to the electric signals;
and the calculating module 203 is used for calculating the distance between the detector and the target object according to the signal parameters.
When the apparatus is used to execute the method provided by the foregoing embodiment, the implementation principle and technical effect are similar, and are not described herein again.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A silicon photodetector, comprising: a detector and a light-enhancing absorption array;
the detector is used for receiving the optical signal and generating an electric signal;
the optical enhancement absorption array is arranged on the surface of the detector and used for increasing the absorption of the detector on an optical signal, wherein the geometrical structure of the optical enhancement absorption array is obtained based on the waveband information of the optical signal and the optical properties of the material of the detector in the optical signal, and the optical properties at least comprise the refractive index or the absorption rate of the detector.
2. The silicon photodetector of claim 1, wherein the light-enhancing absorption array comprises at least one convex solid, or at least one hollow cavity; the geometrical structure of the convex entity comprises a symmetrical structure or an asymmetrical structure, and the geometrical structure of the hollow cavity comprises a symmetrical structure or an asymmetrical structure.
3. The silicon photodetector of claim 1, wherein the geometry of the optically enhanced absorption array comprises at least an array of silicon rings or an array of silicon cylinders.
4. The silicon photodetector of claim 3, wherein the light-enhancing absorption array is the silicon ring array; the inner diameter, the outer diameter and the thickness of each silicon ring are obtained according to the absorptivity of the optical signal by the detector.
5. The silicon photodetector of claim 3, wherein the light-enhancing absorbing array is the silicon cylindrical array; the radius and thickness of each silicon cylinder are obtained from the absorptivity of the optical signal by the detector.
6. The silicon photodetector of claim 1, wherein the absorptivity of the optical signal by the detector is calculated from the structure of the photo-enhanced absorption array, the reflectivity and the refractive index of the detector and the photo-enhanced absorption array.
7. The silicon photodetector of claim 4, wherein each silicon ring in the array of silicon rings has a thickness of 20nm, an outer diameter of 280nm, and an inner diameter of 170nm, and wherein the silicon rings are spaced apart 1500nm for 940nm of the optical signal.
8. The silicon photodetector of claim 5, wherein the silicon cylinders have a thickness of 20nm and a radius of 180nm, and wherein the silicon rings are 1400nm apart for 940nm of the optical signal.
9. A method of measuring distance applied to the silicon photodetector as claimed in any one of claims 1 to 8, the method comprising:
generating an electrical signal according to an optical signal received by the silicon photodetector;
acquiring signal parameters output by the detector according to the electric signals;
and calculating the distance between the detector and the target object according to the signal parameters.
10. A ranging apparatus applied to the ranging method of claim 9, the apparatus comprising: the device comprises a signal generating module, an obtaining module and a calculating module;
the signal generating module is used for generating an electric signal according to the optical signal received by the silicon photodetector;
the acquisition module is used for acquiring signal parameters output by the detector according to the electric signals;
and the calculation module is used for calculating the distance between the detector and the target object according to the signal parameters.
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