Back incidence avalanche photodetector and manufacturing method thereof

Abstract

The invention provides a back incidence avalanche photodetector and a manufacturing method thereof, and the detector comprises a substrate which comprises a front surface and a back surface which are oppositely disposed; the etching barrier layer is located on the front face of the substrate, and a groove for exposing the etching barrier layer is formed in the back face of the substrate; the epitaxial structure is located on the etching barrier layer, and the epitaxial structure comprises an upper electrode contact layer; the upper electrode layer is located on the epitaxial structure; and the DBR reflector is located in the groove and located at the bottom of the etching barrier layer. The groove for exposing the etching barrier layer is formed in the back surface of the substrate, and the DBR is formed in the groove, so that the length of the whole resonant cavity can be accurately controlled, the resonance enhancement effect is generated by adjusting the length of the resonant cavity, the external quantum efficiency of the back incidence avalanche photodetector is improved, and the reliability of the back incidence avalanche photodetector is improved. And the responsivity and the rate of the back incident avalanche photodetector are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors, and in particular to a back-incident avalanche photoelectric detector and a manufacturing method thereof. Background Art

[0002] As the requirements for detector transmission rate become higher and higher, traditional normal incidence detectors cannot further reduce the table size while ensuring the incident light coupling efficiency, and as the thickness of the absorption region decreases, the responsiveness of the device further decreases.

[0003] Avalanche Photo Diode (APD) using back-incident scheme generally evaporates an anti-reflection film on the back or etches a focusing microlens on the back substrate to enhance the absorption of incident light. However, with the development of information technology, the speed requirements are getting higher and higher, and these two technical solutions cannot meet the requirements of high responsiveness and high speed. Summary of the invention

[0004] The object of the present invention is to provide a back-incident avalanche photodetector and a manufacturing method thereof, so as to improve the responsiveness and rate of the back-incident avalanche photodetector.

[0005] In order to solve the above technical problems, according to a first aspect of the present invention, a back-incident avalanche photodetector is provided, comprising:

[0006] A substrate, the substrate comprising a front side and a back side arranged opposite to each other;

[0007] An etch stop layer is located on the front side of the substrate, and a groove exposing the etch stop layer is formed on the back side of the substrate;

[0008] An epitaxial structure, located on the etch stop layer, the epitaxial structure comprising an upper electrode contact layer;

[0009] an upper electrode layer, located on the epitaxial structure; and

[0010] The DBR reflector is located in the groove and at the bottom of the etching stop layer.

[0011] Optionally, the material of the etch stop layer includes InAlAs.

[0012] Optionally, the epitaxial structure further includes a first lower electrode contact layer, a second lower electrode contact layer, a multiplication layer, a charge layer and an absorption layer which are sequentially located on the etch stop layer, and the upper electrode contact layer is located on the absorption layer.

[0013] Optionally, the material of the substrate includes InP, the material of the first lower electrode contact layer includes N-type doped InP, the material of the second lower electrode contact layer includes N-type doped InAlAs, the material of the multiplication layer includes InAlAs, the material of the charge layer includes P-type doped InAlAs, the material of the absorption layer includes InGaAs, the material of the upper electrode contact layer includes P-type doped InGaAs, and the material of the upper electrode layer includes gold, platinum, titanium-gold alloy or platinum-gold alloy.

[0014] Optionally, the DBR reflector includes a silicon nitride layer and a silicon oxide layer stacked in sequence, wherein the silicon nitride layer is close to the etching stop layer.

[0015] In order to solve the above technical problems, according to a second aspect of the present invention, a method for manufacturing a back-incident avalanche photodetector is provided, comprising the following steps:

[0016] Providing a substrate, the substrate comprising a front side and a back side arranged opposite to each other;

[0017] An etching stop layer, an epitaxial structure and an upper electrode layer are sequentially formed on the front surface of the substrate, wherein the epitaxial structure includes an upper electrode contact layer;

[0018] Etching the back side of the substrate until a portion of the etching stop layer is exposed to form a groove; and

[0019] A DBR reflector is formed on the surface of the etching stop layer exposed in the groove.

[0020] Optionally, the method for forming the epitaxial structure includes: using an epitaxial process to sequentially form a first lower electrode contact layer, a second lower electrode contact layer, a multiplication layer, a charge layer and an absorption layer on the etch stop layer, and forming the upper electrode contact layer on the absorption layer.

[0021] Optionally, after forming the etching stop layer and the epitaxial structure on the front surface of the substrate and before forming the upper electrode layer, the method further includes:

[0022] Sequentially etching the upper electrode contact layer, the absorption layer, the charge layer, the multiplication layer, and the second lower electrode contact layer to expose a portion of the first lower electrode contact layer;

[0023] An upper electrode layer is formed on the remaining upper electrode contact layer, and a lower electrode layer is formed on the exposed first lower electrode contact layer.

[0024] Optionally, the upper electrode contact layer, the absorption layer, the charge layer, the multiplication layer and the second lower electrode contact layer are etched in sequence using a wet etching process.

[0025] Optionally, a dry etching process is used to etch the back side of the substrate.

[0026] In the back-incident avalanche photodetector and its manufacturing method provided by the present invention, an etching stop layer, an epitaxial structure and an upper electrode layer are formed on the front side of the substrate, the back side of the substrate is etched until a portion of the etching stop layer is exposed to form a groove, a DBR reflector is formed on the surface of the etching stop layer exposed in the groove, and the upper electrode layer serves as a top reflector and forms a resonant cavity with the DBR reflector. The present invention etches the back side of the substrate until the etching stop layer is exposed, thereby being able to accurately control the length of the entire resonant cavity, and by adjusting the length of the resonant cavity, a resonance enhancement effect is generated, thereby improving the external quantum efficiency of the back-incident avalanche photodetector, and improving the responsiveness and rate of the back-incident avalanche photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a back-incident avalanche photodetector provided in one embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the relationship between the responsivity of a back-incident avalanche photodetector and the film thickness of an etching stop layer provided by an embodiment of the present invention.

[0029] Figure 3 It is a flow chart of a method for manufacturing a back-incident avalanche photodetector provided in one embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 10-substrate; 20-etching stop layer; 30-epitaxial structure; 31-first lower electrode contact layer; 32-second lower electrode contact layer; 33-multiplication layer; 34-charge layer; 35-absorption layer; 36-upper electrode contact layer; 40-upper electrode layer; 50-DBR reflector; 60-lower electrode layer. DETAILED DESCRIPTION

[0032] The calculation formula for the external quantum efficiency of the photodetector (Resonant Cavity Enhanced, RCE) is:

[0033]

[0034] Among them, R t is the reflectivity of the top reflector, R b is the reflectivity of the DBR reflector (i.e. the bottom reflector), α is the absorption coefficient of the absorption layer material to the central wavelength light, d is the thickness of the absorption layer, is the phase loss of light when it enters the top reflector and the DBR reflector. From the above formula, we can see that the reflectivity of the upper and lower reflectors Rt and R b It has a decisive influence on the size of the external quantum efficiency of the resonant cavity photodetector; at the same time, the external quantum efficiency also depends on the product of the absorption coefficient α of the absorption layer material for the central wavelength light and the thickness d of the absorption layer αd; the phase difference caused by the reflection of the light field between the two reflecting mirrors also affects the external quantum efficiency.

[0035] In the above formula, the reflection phase shift caused by the light wave reflecting back and forth once in the resonant cavity is when (m is a positive integer), that is, when the wavelength satisfies the following expression:

[0036]

[0037] The light wave will oscillate back and forth between the reflectors of the resonant cavity, producing a resonance enhancement effect, which greatly enhances the absorption of the light field by the absorption layer. The external quantum efficiency of the detector in this wavelength range will reach its maximum value:

[0038]

[0039] REC detectors have requirements for the entire cavity length L. Only when the cavity length L and the incident wavelength λ meet a specific relationship can the resonance enhancement effect be produced. However, for back-incident detectors, the thickness of the thinned substrate cannot be accurately controlled, so the resonance enhancement effect cannot be produced, and the absorption of incident light cannot be improved through resonance enhancement.

[0040] In view of the above problems, the present invention provides a back-incident avalanche photodetector and a preparation method thereof, which can accurately control the length of the entire resonant cavity, thereby producing a resonance enhancement effect by adjusting the length of the resonant cavity, thereby improving the external quantum efficiency of the back-incident avalanche photodetector and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0041] Specifically, the present invention provides a back-incident avalanche photodetector, comprising: a substrate, the substrate comprising a front side and a back side arranged opposite to each other; an etch stop layer, located on the front side of the substrate; a groove exposing the etch stop layer is formed on the back side of the substrate; an epitaxial structure, located on the etch stop layer, the epitaxial structure comprising an upper electrode contact layer; an upper electrode layer, located on the epitaxial structure; and a DBR reflector, located in the groove and at the bottom of the etch stop layer.

[0042] Correspondingly, the present invention also provides a method for manufacturing a back-incident avalanche photodetector, comprising: providing a substrate, the substrate comprising a front side and a back side arranged opposite to each other; sequentially forming an etch stop layer, an epitaxial structure and an upper electrode layer on the front side of the substrate, the epitaxial structure comprising an upper electrode contact layer; etching the back side of the substrate until a portion of the etch stop layer is exposed to form a groove; and forming a DBR reflector on the surface of the etch stop layer exposed in the groove.

[0043] In the back-incident avalanche photodetector and its manufacturing method provided by the present invention, an etching stop layer, an epitaxial structure and an upper electrode layer are formed on the front side of the substrate, the back side of the substrate is etched until a portion of the etching stop layer is exposed to form a groove, a DBR reflector is formed on the surface of the etching stop layer exposed in the groove, and the upper electrode layer serves as a top reflector and forms a resonant cavity with the DBR reflector. The present invention etches the back side of the substrate until the etching stop layer is exposed, thereby being able to accurately control the length of the entire resonant cavity, and by adjusting the length of the resonant cavity, a resonance enhancement effect is generated, thereby improving the external quantum efficiency of the back-incident avalanche photodetector, and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0044] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0045] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense that includes "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense that includes "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense that includes "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0046] Figure 1is a schematic diagram of the structure of a back-incident avalanche photodetector provided by an embodiment of the present invention. Figure 1 As shown, the back-incident avalanche photodetector provided by the embodiment of the present invention comprises:

[0047] A substrate 10, wherein the substrate 10 includes a front surface S1 and a back surface S2 that are oppositely disposed;

[0048] An etch stop layer 20 is located on the front side S1 of the substrate 10, and a groove 11 exposing the etch stop layer 20 is formed on the back side S2 of the substrate 10;

[0049] An epitaxial structure 30, located on the etch stop layer 20, the epitaxial structure 30 includes an upper electrode contact layer 36;

[0050] an upper electrode layer 40 , located on the epitaxial structure 30 ; and

[0051] The DBR reflector 50 is located in the groove 11 and at the bottom of the etching stop layer 20 .

[0052] In the embodiment of the present invention, the upper electrode layer 40 serves as a top reflector and forms a resonant cavity with the DBR reflector 50. Since the substrate 10 between the upper electrode layer 40 and the DBR reflector 50 has been removed, the thickness of the etch stop layer 20 and the epitaxial structure 30 can be precisely controlled, so that the length of the entire resonant cavity can be precisely controlled. By adjusting the length of the resonant cavity, a resonance enhancement effect is generated, thereby improving the external quantum efficiency of the back-incident avalanche photodetector, and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0053] In one embodiment of the present invention, the substrate 10 is an insulating substrate, and the material of the substrate 10 includes but is not limited to InP. The material of the etching stop layer 20 includes but is not limited to InAlAs.

[0054] The epitaxial structure 30 includes a first lower electrode contact layer 31, a second lower electrode contact layer 32 and an upper electrode contact layer 36 sequentially located on the etching stop layer 20, and a multiplication layer 33, a charge layer 34 and an absorption layer 35 are formed between the second lower electrode contact layer 32 and the upper electrode contact layer 36.

[0055] In one embodiment, on the second lower electrode contact layer 32, the multiplication layer 33, the charge layer 34 and the absorption layer 35 are stacked in sequence from bottom to top. In another embodiment, on the second lower electrode contact layer 32, the absorption layer 35, the charge layer 34 and the multiplication layer 33 are stacked in sequence from bottom to top. In this embodiment, on the second lower electrode contact layer 32, the multiplication layer 33, the charge layer 34 and the absorption layer 35 are stacked in sequence from bottom to top. Since the multiplication layer 33 is a high electric field region, arranging the multiplication layer 33 on a side close to the substrate 10 is beneficial to the heat dissipation performance of the back-incident avalanche photodetector, and improves the working performance and reliability of the back-incident avalanche photodetector.

[0056] The upper electrode contact layer 36 and the first lower electrode contact layer 31 and the second lower electrode contact layer 32 are used to respectively realize ohmic contact between the upper electrode layer and the lower electrode layer (which will be described later) to ensure good electrical performance of the device. The absorption layer 35 utilizes the principle of carrier energy level transition to realize infrared photon absorption to convert the photons incident into the back-incident avalanche photodetector into photogenerated carriers to realize photoelectric conversion. The multiplication layer 33 utilizes the collision ionization characteristics of the material under high electric field to make the photogenerated re-use spontaneous collision ionization to realize gain. The charge layer 34 is used to adjust the electric field between the multiplication layer 33 and the absorption layer 35.

[0057] In one embodiment of the present invention, the material of the first lower electrode contact layer 31 includes but is not limited to N-type doped InP, the material of the second lower electrode contact layer 32 includes but is not limited to N-type doped InAlAs, the material of the multiplication layer 33 includes but is not limited to InAlAs, the material of the charge layer 34 includes but is not limited to P-type doped InAlAs, the material of the absorption layer 35 includes but is not limited to InGaAs, and the material of the upper electrode contact layer 36 includes but is not limited to P-type doped InGaAs.

[0058] The back side of the substrate 10 is formed with a groove 11 exposing the etching stop layer 20. The cross-sectional size of the bottom of the groove 11 (i.e., the side close to the etching stop layer 20) may be greater than or equal to the cross-sectional size of the upper electrode layer 40. The cross-sectional size refers to Figure 1 The cross section of the groove 11 ( Figure 1 The cross-section in the horizontal direction shown in the figure can be in any suitable shape such as a rectangle, a square, a trapezoid, or a Figure 1 In the convex shape shown, the groove 11 has two cross-sectional dimensions, and the cross-sectional dimension near the bottom is smaller than the cross-sectional dimension near the top, but it is certainly not limited to this.

[0059] The DBR reflector 50 includes a silicon nitride layer and a silicon oxide layer stacked in sequence, wherein the silicon nitride layer is close to the etch stop layer 20. The DBR reflector 50 is located in the groove 11 and at the bottom of the etch stop layer 20, that is, the DBR reflector 50 is formed on the etch stop layer 20 at the bottom of the groove 11, for example, the silicon nitride layer is formed first and then the silicon oxide layer is formed.

[0060] In one embodiment of the present invention, the back-incident avalanche photodetector further includes a lower electrode layer 60, and the length of the first lower electrode contact layer 31 is greater than the length of the second lower electrode contact layer 32 ( Figure 1 , that is, the second lower electrode contact layer 32 covers a portion of the first lower electrode contact layer 31 , and the lower electrode layer 60 is located on the first lower electrode contact layer 31 not covered by the second lower electrode contact layer 32 .

[0061] The upper electrode layer 40 and the lower electrode layer 60 are both metal thin film electrodes, and the metal material may be gold, platinum, titanium-gold alloy or platinum-gold alloy, but is not limited thereto. The upper electrode layer 40 covers the upper electrode contact layer 36 to realize electrical extraction of the upper electrode contact layer 36, and the lower electrode layer 60 covers a portion of the first lower electrode contact layer 31 to realize electrical extraction of the first lower electrode contact layer 31.

[0062] In this embodiment, the upper electrode layer 40 also serves as a top reflector, and forms a resonant cavity with the DBR reflector 50. That is, in addition to being used to realize the electrical lead-out of the upper electrode contact layer 36, the upper electrode layer 40 also serves as the top reflector of the back-incident avalanche photodetector, so that the photons entering the back-incident avalanche photodetector that are not completely absorbed by the absorption layer 35 are reflected and then return to the absorption layer 35 for secondary absorption, so that the incident light is reflected back and forth multiple times in the entire resonant cavity to form resonance, so as to improve the working performance of the back-incident avalanche photodetector.

[0063] As an example, the thickness range of the etch stop layer 20 is 150nm~350nm, the thickness range of the first lower electrode contact layer 31 is 100nm~300nm, the thickness range of the second lower electrode contact layer 32 is 100nm~300nm, the thickness range of the multiplication layer 33 is 80nm~100nm, the thickness range of the charge layer 34 is 50nm~70nm, the thickness range of the absorption layer 35 is 200nm~400nm, the thickness range of the upper electrode contact layer 36 is 40nm~60nm, the thickness range of the upper electrode layer 40 is 80nm~120nm, the thickness range of the silicon nitride layer is 100nm~200nm, and the thickness of the silicon oxide layer is 200nm~250nm. In this embodiment, the thickness of the etching stop layer 20 is preferably 250nm, the thickness of the first lower electrode contact layer 31 is preferably 200nm, the thickness of the second lower electrode contact layer 32 is preferably 200nm, the thickness of the multiplication layer 33 is preferably 90nm, the thickness of the charge layer 34 is preferably 60nm, the thickness of the absorption layer 35 is preferably 300nm, the thickness of the upper electrode contact layer 36 is preferably 50nm, and the thickness of the upper electrode layer 40 is preferably 100nm.

[0064] In one embodiment, the back-incident avalanche photodetector provided by the present invention is compared with the back-incident avalanche photodetector in the prior art in which the substrate is not etched and an anti-reflection film (AR film) is formed on the back side of the substrate, and the responsivity of the back-incident avalanche photodetector is calculated by the transfer matrix (TMM). Among them, in the present invention, the thickness and refractive index of each layer of the back-incident avalanche photodetector are: the thickness of the substrate 10 is 120μm, and the refractive index is 3.18; the thickness of the first lower electrode contact layer 31 is 200nm, and the refractive index is 3.18; the thickness of the second lower electrode contact layer 32 is 200nm, and the refractive index is 3.25; the thickness of the multiplication layer 33 is 90nm, and the refractive index is 3.25; the thickness of the charge layer 34 is 60nm, and the refractive index is 3.25; the thickness of the absorption layer 35 is 30nm, and the refractive index is 3.61+0.18i; the thickness of the upper electrode contact layer 36 is 50nm, and the refractive index is 3.61+0.18i; the thickness of the upper electrode layer 40 is 100nm, and the refractive index is 0.41+8.46i; the thickness of the silicon nitride layer in the DBR reflector 50 is 163nm, and the refractive index is 2; the thickness of the silicon oxide layer is 226, and the refractive index is 1.44. In the prior art, the only difference from the above conditions is that there is no etching stopper layer 20 and DBR reflector 50, and no groove is formed in the substrate 10. An anti-reflection film is formed on the back of the substrate 10. The thickness of the anti-reflection film is 163nm and the refractive index is 2.

[0065] For the back-incident avalanche photodetector provided by the prior art, under the above conditions, the responsivity is only 0.56 A / W. Figure 2 is a schematic diagram of the relationship between the responsivity of the back-incident avalanche photodetector and the film thickness of the etching stop layer provided by an embodiment of the present invention, please refer to Figure 2 As shown, the horizontal axis is the thickness of the etching stop layer, in nm, and the vertical axis is the responsivity, in A / W. Under the above conditions of fixed film thickness and refractive index, as the thickness of the etching stop layer 20 increases, the responsivity first increases and then decreases. When the thickness of the etching stop layer is 250nm, the responsivity is the highest, about 0.85A / W, which is higher than the responsivity of the back-incident avalanche photodetector in the prior art. Figure 2 It can be seen that when the thickness of the etch stop layer is between 225nm and 275nm, its responsivity is greater than 0.56A / W of the prior art. Of course, the thickness of the etch stop layer is not limited to this, and the thickness of the etch stop layer can be determined according to the actual thickness of the other layers of the back-incident avalanche photodetector, so that the responsivity of the back-incident avalanche photodetector is the highest.

[0066] In the back-incident avalanche photodetector provided by the present invention, an etch stop layer 20, an epitaxial structure 30 and an upper electrode layer 40 are formed on the front side of a substrate 10, a groove 11 exposing the etch stop layer 20 is formed on the back side of the substrate 10, a DBR reflector 50 is located in the groove 11 and at the bottom of the etch stop layer 20, and the upper electrode layer 40 serves as a top reflector and forms a resonant cavity with the DBR reflector 50. Since there is no substrate 10 in the resonant cavity, there is no need to thin the substrate 10 and control the thickness of the substrate 10, so that the length of the entire resonant cavity can be accurately controlled, and a resonance enhancement effect is generated by adjusting the length of the resonant cavity, thereby improving the external quantum efficiency of the back-incident avalanche photodetector, and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0067] Correspondingly, the present invention also provides a method for manufacturing a back-incident avalanche photodetector, which is used to manufacture the back-incident avalanche photodetector as described above.

[0068] Figure 3 FIG. 1 is a flow chart of a method for manufacturing a back-incident avalanche photodetector according to an embodiment of the present invention. Figure 3 As shown, a method for manufacturing a back-incident avalanche photodetector provided by an embodiment of the present invention comprises the following steps:

[0069] S1: providing a substrate, wherein the substrate comprises a front side and a back side arranged opposite to each other;

[0070] S2: forming an etching stop layer, an epitaxial structure and an upper electrode layer in sequence on the front surface of the substrate, wherein the epitaxial structure includes an upper electrode contact layer;

[0071] S3: etching the back side of the substrate until a portion of the etching stop layer is exposed to form a groove; and

[0072] S4: forming a DBR reflector on the surface of the etching stop layer exposed in the groove.

[0073] Next, we will combine Figure 1 and Figure 3 The method for manufacturing the back-incident avalanche photodetector provided in the embodiment of the present invention is described in detail.

[0074] In step S1 , a substrate 10 is provided. The substrate 10 includes a front side S1 and a back side S2 that are oppositely disposed.

[0075] The substrate 10 is an insulating substrate, and the material of the substrate 10 includes but is not limited to InP. The substrate 10 includes a front side S1 and a back side S2 that are oppositely disposed.

[0076] In step S2 , an etching stop layer 20 , an epitaxial structure 30 and an upper electrode layer 40 are sequentially formed on the front surface S1 of the substrate 10 , wherein the epitaxial structure 30 includes an upper electrode contact layer 36 .

[0077] In one embodiment of the present invention, the epitaxial structure 30 includes a first lower electrode contact layer 31, a second lower electrode contact layer 32, a multiplication layer 33, a charge layer 34, an absorption layer 35 and an upper electrode contact layer 36 which are sequentially stacked from bottom to top.

[0078] An etching stop layer 20, a first lower electrode contact layer 31, a second lower electrode contact layer 32, a multiplication layer 33, a charge layer 34, an absorption layer 35 and an upper electrode contact layer 36 are sequentially formed on the front surface of the substrate 10. The above layers can be formed on the substrate 10 by epitaxial process, but it is not limited thereto.

[0079] In one embodiment of the present invention, after forming the epitaxial structure 30, that is, after forming the upper electrode contact layer 36, the process further includes: sequentially etching the upper electrode contact layer 36, the absorption layer 35, the charge layer 34, the multiplication layer 33 and the second lower electrode contact layer 32 to expose a portion of the first lower electrode contact layer 31. Figure 1 As shown, the upper electrode contact layer 36, the absorption layer 35, the charge layer 34, the multiplication layer 33 and the edge of the second lower electrode contact layer 32 are sequentially etched until the edge of the first lower electrode contact layer 31 is exposed. Exemplarily, a wet etching process may be used to perform etching in sequence, and of course, any suitable process such as dry etching, plasma etching, etc. may also be used to etch each film layer.

[0080] Exemplarily, a mask layer is first formed on the upper electrode contact layer 36, the mask layer is etched to form a patterned mask layer, the upper electrode contact layer 36, the absorption layer 35, the charge layer 34, the multiplication layer 33 and the second lower electrode contact layer 32 are sequentially etched using the patterned mask layer as a mask, and then the patterned mask layer is removed. The mask layer may be a photoresist layer or a hard mask layer such as silicon nitride or silicon oxide.

[0081] Then, an upper electrode layer 40 is formed on the remaining upper electrode contact layer 36 , and a lower electrode layer 60 is formed on the exposed first lower electrode contact layer 31 .

[0082] Exemplarily, a metal material may be deposited by any suitable process such as a chemical vapor deposition process, and then etched to form the upper electrode layer 40 and the lower electrode layer 60. The upper electrode layer 40 and the lower electrode layer 60 may be formed simultaneously, or the upper electrode layer 40 or the lower electrode layer 60 may be formed first, and then the lower electrode layer 60 or the upper electrode layer 40 may be formed. Afterwards, a suitable high-temperature annealing is performed so that the lower electrode layer 60 forms a good ohmic contact with the first lower electrode contact layer 31, and the upper electrode layer 40 forms a good ohmic contact with the upper electrode contact layer 36.

[0083] In step S3 , the back side S2 of the substrate 10 is etched until a portion of the etch stop layer 20 is exposed to form a groove 11 .

[0084] The substrate 10 is etched from the back side S2 of the substrate 10 until the etch stop layer 20 is exposed. The etch stop layer 20 serves as a barrier layer for this etching. The etching stops on the etch stop layer 20. A groove 11 exposing the etch stop layer 20 is formed on the back side S2 of the substrate 10, that is, the substrate 10 at the bottom of the groove 11 is completely removed. In this embodiment, dry etching may be used, for example, inductively coupled plasma etching (ICP Etching) may be used to etch the back side S2 of the substrate 10.

[0085] In step S4 , a DBR reflector 50 is formed on the surface of the etch stop layer 20 exposed in the groove 11 .

[0086] In this embodiment, the DBR reflector 50 may be formed by any suitable process such as physical vapor deposition process, chemical vapor deposition process, atomic layer deposition process, etc. The DBR reflector 50 covers the etch stop layer 20 exposed at the bottom of the groove 11 .

[0087] The upper electrode layer 40 serves as a top reflector and forms a resonant cavity with the DBR reflector 50. Since there is no substrate 10 between the upper electrode 40 and the DBR reflector 50, the length of the entire resonant cavity can be accurately controlled. By adjusting the length of the resonant cavity, a resonance enhancement effect is generated, thereby improving the external quantum efficiency of the back-incident avalanche photodetector and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0088] In summary, in the back-incident avalanche photodetector and its manufacturing method provided by the present invention, an etch barrier layer, an epitaxial structure and an upper electrode layer are formed on the front side of the substrate, the back side of the substrate is etched until a portion of the etch barrier layer is exposed to form a groove, a DBR reflector is formed on the surface of the etch barrier layer exposed in the groove, and the upper electrode layer serves as a top reflector and forms a resonant cavity with the DBR reflector. The present invention etches the back side of the substrate until the etch barrier layer is exposed, thereby being able to accurately control the length of the entire resonant cavity, and produce a resonance enhancement effect by adjusting the length of the resonant cavity, thereby improving the external quantum efficiency of the back-incident avalanche photodetector, and improving the responsiveness and rate of the back-incident avalanche photodetector.

[0089] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A back-incident avalanche photodetector, characterized in that: include: A substrate, the substrate comprising a front side and a back side arranged opposite to each other; An etch stop layer is located on the front side of the substrate, and a groove exposing the etch stop layer is formed on the back side of the substrate; An epitaxial structure, located on the etch stop layer, the epitaxial structure comprising an upper electrode contact layer; An upper electrode layer, located on the epitaxial structure; as well as The DBR reflector is located in the groove and at the bottom of the etching stop layer.

2. The back-incident avalanche photodetector according to claim 1, characterized in that: The material of the etch stop layer includes InAlAs.

3. The back-incident avalanche photodetector according to claim 1, characterized in that: The epitaxial structure further includes a first lower electrode contact layer, a second lower electrode contact layer, a multiplication layer, a charge layer and an absorption layer which are sequentially located on the etch stop layer, and the upper electrode contact layer is located on the absorption layer.

4. The back-incident avalanche photodetector according to claim 3, characterized in that: The material of the substrate includes InP, the material of the first lower electrode contact layer includes N-type doped InP, the material of the second lower electrode contact layer includes N-type doped InAlAs, the material of the multiplication layer includes InAlAs, the material of the charge layer includes P-type doped InAlAs, the material of the absorption layer includes InGaAs, the material of the upper electrode contact layer includes P-type doped InGaAs, and the material of the upper electrode layer includes gold, platinum, titanium-gold alloy or platinum-gold alloy.

5. The back-incident avalanche photodetector according to claim 1, characterized in that: The DBR reflector includes a silicon nitride layer and a silicon oxide layer stacked in sequence, wherein the silicon nitride layer is close to the etching stop layer.

6. A method for manufacturing a back-incident avalanche photodetector, characterized in that: The following steps are involved: Providing a substrate, the substrate comprising a front side and a back side arranged opposite to each other; An etching stop layer, an epitaxial structure and an upper electrode layer are sequentially formed on the front surface of the substrate, wherein the epitaxial structure includes an upper electrode contact layer; Etching the back side of the substrate until a portion of the etching stop layer is exposed to form a groove; and A DBR reflector is formed on the surface of the etching stop layer exposed in the groove.

7. The method for manufacturing a back-incident avalanche photodetector according to claim 6, characterized in that: The method for forming the epitaxial structure includes: using an epitaxial process to sequentially form a first lower electrode contact layer, a second lower electrode contact layer, a multiplication layer, a charge layer and an absorption layer on the etch stop layer, and forming the upper electrode contact layer on the absorption layer.

8. The method for manufacturing a back-incident avalanche photodetector according to claim 7, characterized in that: After forming the etching stop layer and the epitaxial structure on the front side of the substrate and before forming the upper electrode layer, the method further comprises: Sequentially etching the upper electrode contact layer, the absorption layer, the charge layer, the multiplication layer, and the second lower electrode contact layer to expose a portion of the first lower electrode contact layer; An upper electrode layer is formed on the remaining upper electrode contact layer, and a lower electrode layer is formed on the exposed first lower electrode contact layer.

9. The method for manufacturing a back-incident avalanche photodetector according to claim 8, characterized in that: The upper electrode contact layer, the absorption layer, the charge layer, the multiplication layer and the second lower electrode contact layer are etched in sequence using a wet etching process.

10. The method for manufacturing a back-incident avalanche photodetector according to claim 6, characterized in that: The back side of the substrate is etched using a dry etching process.

Images