A photodetector structure and preparation method thereof

Abstract

The present application relates to a photoelectric detector structure and a method for preparing the same. The detector structure adopts an epitaxial growth method, wherein (Al x Ga y )InAs layer or AlInAs layer is generated, the epitaxial growth is stopped within a preset time and the growth (Al x Ga y )N-type impurities are introduced into the reaction chamber of the InAs layer or the AlInAs layer, and the temperature of the reaction chamber is first reduced and then increased; the layer closest to the absorption layer in the second reflective layer is the AlInAs layer, and the growth temperature of the AlInAs layer is more than 20°C lower than that of other layers in the second reflective layer. The present application can make the reflective layer in the photodetector have a high reflectivity, improve the quantum efficiency of the photodetector, and reduce the thermal resistance of the photodetector.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communication technology, and in particular to a photoelectric detector structure and a preparation method thereof. Background Art

[0002] With the development of optical fiber communication technology, the bandwidth is getting larger and larger, the transmission distance is getting longer and longer, and the requirements for the responsiveness and sensitivity of the detector are getting higher and higher. In the structure of the photodetector, a thin absorption layer can reduce the transit time of photogenerated carriers and improve the response efficiency of the detector. However, a thin absorption layer is not conducive to confining light in the absorption area and converting it into an electrical signal, which will reduce the quantum efficiency of the detector (the ratio of the average number of photoelectrons generated per unit time at a specific wavelength to the number of incident photons). That is, the thickness of the absorption layer is a contradictory factor for the device rate and quantum efficiency.

[0003] Currently, a resonant cavity structure is used inside the detector, that is, DBR (Distributed Bragg Reflector) is designed at the bottom and top of the device. This DBR is grown alternately with two materials of low refractive index and high refractive index, and the thickness of each material layer meets 1 / 4 of the wavelength of the incident light in the semiconductor. Since the high reflectivity of DBR can confine light to the absorption area and meet the requirements of quantum efficiency, a thin absorption layer can be prepared to ensure the response efficiency of the detector.

[0004] However, the refractive index difference of DBR for the optical communication window 1310nm or 1550nm is small. In order to ensure high reflectivity, the logarithm of DBR reflector needs to be increased. However, the increase in logarithm will increase the resistance and thermal resistance of the detector, affecting the normal operation of the detector. Summary of the invention

[0005] Based on this, it is necessary to provide a detector structure and a preparation method thereof that can ensure that the DBR has high reflectivity while reducing thermal resistance in order to solve the above technical problems.

[0006] A photodetector structure, comprising a substrate, a buffer layer, a first reflection layer, a second reflection layer, an absorption layer, and a window layer stacked in sequence from bottom to top;

[0007] In some embodiments, the first reflective layer includes alternately stacked (Al x1 Ga y1 )InAs layer and AlInAs layer; the second reflective layer includes alternately stacked (Al x2 Ga y2 )InAs layer and AlInAs layer; where x1 <x2。

[0008] In some embodiments, the number of AlInAs layers in the first reflective layer is greater than or equal to the number of AlInAs layers in the second reflective layer.

[0009] In some embodiments, the total of the AlInAs layer in the first reflective layer and the AlInAs layer in the second reflective layer is greater than 40.

[0010] In some embodiments, (Al x1 Ga y1 )InAs layer, (Al x2 Ga y2 )The thickness of the InAs layer and the AlInAs layer satisfies the following formula:

[0011]

[0012] Where D is the thickness, k is an integer greater than 1, λ is the wavelength of the incident light, and Ne is (Al x1 Ga y1 )InAs layer, (Al x2 Ga y2 )The refractive index of the InAs layer and the AlInAs layer.

[0013] In some embodiments, (Al x1 Ga y1 )InAs layer and (Al x2 Ga y2 )In the InAs layer, the conditions are satisfied: 0<x1<0.5, 0<x2<0.5.

[0014] In some embodiments, (Al x1 Ga y1 )InAs layer and AlInAs layer interface, (Al x2 Ga y2 ) Delta doping is used at the interface between the InAs layer and the AlInAs layer.

[0015] The present application further provides a method for preparing a photodetector structure, comprising the following steps:

[0016] epitaxially growing a buffer layer on the substrate;

[0017] A first reflective layer is epitaxially grown on the buffer layer. The first reflective layer includes (Al x1 Ga y1 )InAs layer and AlInAs layer;

[0018] A second reflective layer is epitaxially grown on the first reflective layer. The second reflective layer includes (Al x2 Ga y2)InAs layer and AlInAs layer; where x1 <x2;

[0019] An absorption layer and a window layer are epitaxially grown in sequence on the second reflection layer.

[0020] In some embodiments, when the first reflective layer is epitaxially grown on the buffer layer, the process further includes: x1 Ga y1 )InAs layer is generated within a preset time, epitaxial growth is stopped and the growth (Al x1 Ga y1 )InAs layer, N-type impurities are introduced into the reaction chamber, and the temperature of the reaction chamber first decreases and then increases; x1 Ga y1 )InAs layer is formed, an AlInAs layer is grown; within a preset time after the AlInAs layer is formed, epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; outside the preset time after the AlInAs layer is formed, (AlInAs layer) is grown x1 Ga y1 )InAs layer.

[0021] In some embodiments, when the second reflective layer is epitaxially grown on the first reflective layer, the process further includes: x2 Ga y2 )InAs layer is generated within a preset time, epitaxial growth is stopped and the growth (Al x2 Ga y2 )InAs layer, N-type impurities are introduced into the reaction chamber, and the temperature of the reaction chamber first decreases and then increases; x2 Ga y2 )InAs layer is formed, an AlInAs layer is grown; within a preset time after the AlInAs layer is formed, epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; outside the preset time after the AlInAs layer is formed, (AlInAs layer) is grown x2 Ga y2 )InAs layer.

[0022] In some embodiments, the layer closest to the absorption layer in the second reflection layer is an AlInAs layer, and the growth temperature of the AlInAs layer closest to the absorption layer is at least 20° C. lower than the growth temperature of other layer materials in the second reflection layer.

[0023] The above-mentioned photodetector structure has a first reflection layer and a second reflection layer respectively disposed between the buffer layer and the absorption layer, wherein the first reflection layer comprises (Al x1 Ga y1 )InAs layer and AlInAs layer, the second reflective layer includes alternately stacked (Alx2 Ga y2 ) The InAs layer and the AlInAs layer, where x1 < x2, that is, the (Al x Ga y ) In the InAs closer to the absorption layer, the Al component content is higher than that of the (Al x Ga y ) InAs farther from the absorption layer. The (Al x Ga y ) InAs farther from the absorption layer has a lower Al component content. The refractive index difference between the (Al x Ga y ) InAs and the AlInAs is large, and the reflectivity of the formed reflective layer is high, ensuring a high reflectivity and avoiding increasing the number of pairs of DBR mirrors. At the same time, the (Al x Ga y ) InAs farther from the absorption layer has a lower Al component content. The (Al x Ga y ) InAs absorbs light with a longer wavelength, and may absorb the light spilling out from the absorption region due to the band-tail effect of the semiconductor, weakening the reflection effect of the reflective layer. Moreover, the closer the Al component content is to 0.5, the higher the thermal resistance value generated by the material. The (Al x Ga y ) InAs closer to the absorption layer has a higher Al component content, which can reduce the absorption of the light spilling out from the absorption region and reduce the thermal resistance of the detector. In summary, the two reflective layers with different A components cooperate with each other, and the overall composite reflective layer can achieve the effect of improving the reflection effect and reducing the thermal resistance at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Description of the reference numerals:

[0026] Figure 1 It is a schematic structural diagram of a photodetector in an embodiment;

[0027] Figure 2 It is a schematic structural diagram of a photodetector in an embodiment;

[0028] Figure 3 It is a schematic structural diagram of a photodetector in an embodiment;

[0029] Figure 4Schematic diagram of the preparation process of the optoelectronic detector structure in an embodiment;

[0030] Figure 5 Schematic diagram of the preparation process of the optoelectronic detector structure in an embodiment. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] As described in the background art, in order to balance the high response efficiency and high quantum efficiency in the optoelectronic detector, a DBR for reflecting incident light is provided in the internal structure of the existing detector. However, for the optical communication windows of 1310 nm or 1550 nm, the required number of DBR pairs is relatively large, and at the same time, it will cause an increase in resistance and thermal resistance, which is not conducive to the normal operation of the detector.

[0033] For the above reasons, in one embodiment, as Figure 1 shown, an optoelectronic detector structure is provided, which sequentially includes a substrate 10, a buffer layer 20, a first reflective layer 30, a second reflective layer 40, an absorption layer 50, and a window layer 60. Among them, the first reflective layer 30 includes alternately stacked (Al x1 Ga y1 )InAs layers 31 and AlInAs layers 32, and the second reflective layer includes alternately stacked (Al x2 Ga y2 )InAs layers 41 and AlInAs layers 42, where x1 < x2.

[0034] In the above optoelectronic detector structure, a first reflective layer and a second reflective layer are respectively provided between the buffer layer and the absorption layer. The first reflective layer includes alternately stacked (Al x1 Ga y1 )InAs layers and AlInAs layers, and the second reflective layer includes alternately stacked (Al x2 Ga y2 )InAs layers and AlInAs layers, where x1 < x2, that is, the Al component content in the (Al x Ga y )InAs close to the absorption layer is higher than the Al component content in the (Al x Ga y )InAs far from the absorption layer. The Al component content in the (Al x Ga y )InAs far from the absorption layer is relatively low, and the (Al x Ga y)InAs and AlInAs have a large difference in refractive index, so the reflective layer formed has a high reflectivity, which ensures a high reflectivity and avoids increasing the number of DBR reflectors. x Ga y )InAs has a low Al content. x Ga y )InAs absorbs light with a longer wavelength, and may absorb the light overflowing from the absorption region due to the band tail effect of the semiconductor, weakening the reflection effect of the reflective layer. In addition, the closer the Al component content is to 0.5, the higher the thermal resistance value generated by the material. x Ga y ) The Al content in InAs is relatively high, which can reduce the absorption of the overflow light in the absorption area and reduce the thermal resistance of the detector. In summary, the two reflection layers with different Al components cooperate with each other, and the overall composite reflection layer can achieve the effect of improving the reflection effect while reducing the thermal resistance.

[0035] Specifically, the substrate 10 is an InP substrate. The substrate 10 is N-type doped, and the doping concentration of the substrate 10 is 3*10 18 cm -3 ~7*10 18 cm -3 , such as 3*10 18 cm -3 , 4*10 18 cm -3 , 5*10 18 cm -3 , 6*10 18 cm -3 ,7*10 18 cm -3 wait.

[0036] The buffer layer 20 is an InP buffer layer. The buffer layer 20 is N-type doped, and the doping concentration of the buffer layer 20 is 10 18 cm -3 ~3*10 18 cm -3 , such as 10 18 cm -3 , 1.5*10 18 cm -3 , 2*10 18 cm -3 , 2.5*10 18 cm -3 , 3*10 18 cm -3The buffer layer 20 is epitaxially grown with the same material as the substrate 10 to avoid the mismatch of lattice constant and thermal expansion coefficient between the substrate and the epitaxial layer grown on the substrate, buffer the stress caused by direct contact between the substrate and the epitaxial layer, and thus improve the quality of the epitaxial layer.

[0037] The first reflective layer 30 and the second reflective layer 40 are N-type doped. The first reflective layer 30 and the second reflective layer 40 are a distributed Bragg reflector (DBR). DBR is a periodic structure composed of a low refractive index material and a high refractive index material alternately stacked. Since electromagnetic waves with frequencies falling within the energy gap range of semiconductor materials cannot penetrate, the reflectivity of the Bragg reflector can be as high as 99%. In this embodiment, the first reflective layer 30 and the second reflective layer 40 can be used to reflect photons in the incident band, limit the spillover of incident light entering the absorption layer 30, and achieve more efficient light absorption efficiency.

[0038] The absorption layer 50 is a GaInAs absorption layer, and the absorption layer 50 is a non-doped layer. The absorption layer 50 can realize the conversion of optical signals into electrical signals, which mainly utilizes the photoconductivity effect of semiconductor materials, that is, under the action of light, the semiconductor material absorbs the incident photon energy. If the photon energy is greater than or equal to the bandgap width of the semiconductor material, electron-hole pairs are excited, so that the carrier concentration increases and the conductivity of the semiconductor increases.

[0039] The window layer 60 is an InP window layer, and the window layer 60 is P-type doped. The window layer 60 is used to first receive the incident light wave entering the photodetector.

[0040] In the above embodiments, impurities are doped on each epitaxial layer to improve the conductivity of the material, reduce the resistance value, and help carriers diffuse or drift to form current.

[0041] In one embodiment, 0<x1<0.5, 0<x2<0.5. For example, (Al x1 Ga y1 ) The Al composition of the InAs layer 31 is 0.172, the Ga composition is 0.301, and the In composition is 0.53. x2 Ga y2 )The Al composition of the InAs layer 41 is 0.221, the Ga composition is 0.252, and the In composition is 0.53.

[0042] In one embodiment, (Al x1 Ga y1 )The interface between the InAs layer 31 and the AlInAs layer 32, (Al x2 Ga y2)The interface between the InAs layer 41 and the AlInAs layer 42 is Delta doped.

[0043] Among them, Delta doping means that the concentration of doped impurities in the growth direction shows the law of Delta function (impulse function), which is specifically manifested as the doped impurities are only distributed in (Al x1 Ga y1 )The interface between the InAs layer 31 and the AlInAs layer 32 and (Al x2 Ga y2 )The interface between the InAs layer 41 and the AlInAs layer 42, and the doping concentration in other areas is 0.

[0044] In the above embodiment, high-concentration impurities are doped between the interfaces of the two semiconductor materials of the first reflective layer 30 and the second reflective layer 40, and the carrier concentration inside the semiconductor material is increased, which is beneficial to improving the conductivity between the material interfaces, and effectively reducing the increase in device internal resistance caused by the composite structure composed of multiple pairs of first reflective layers 30 and second reflective layers 40, reducing the heating of the device under large current, and forming a high-performance and reliable APD detector.

[0045] In one embodiment, the number of AlInAs layers 32 in the first reflective layer is greater than or equal to the number of AlInAs layers 42 in the second reflective layer. For example, the number of AlInAs layers 32 in the first reflective layer 30 is 34, that is, the number of pairs of the first reflective layer is 34, and the number of AlInAs layers 42 in the second reflective layer 40 is 10, that is, the number of pairs of the first reflective layer is 10.

[0046] In the above embodiment, since in the first reflective layer 30 (Al x1 Ga y1 ) The Al component of the InAs layer 31 is low, so the electrical resistance and thermal resistance generated by the first reflective layer 30 are low, and (Al x1 Ga y1 ) The refractive index difference between the InAs layer 31 and the AlInAs layer 32 is large, so the reflectivity of the first reflective layer 30 is high. In the detector reflective layer, since the number of logarithms of the first reflective layer 30 is greater than that of the second reflective layer 40, the reflective layer composed of the first reflective layer 30 and the second reflective layer 40 mainly exhibits the same performance as the first reflective layer 30, and the photodetector can achieve the effects of high reflectivity and low thermal resistance.

[0047] In one embodiment, the total number of AlInAs layers 32 in the first reflective layer and AlInAs layers 42 in the second reflective layer is greater than 40, such as 40, 45, 50, 55, 60, etc.

[0048] In the above embodiment, the total number of AlInAs layers 32 in the first reflection layer and AlInAs layers 42 in the second reflection layer is specified, which can ensure that the first reflection layer 30 and the second reflection layer 40 have high reflectivity that meets the performance requirements of the detector.

[0049] In one embodiment, (Al x1 Ga y1 )InAs layer 31, (Al x2 Ga y2 )The thickness of the InAs layer 41, the AlInAs layer 32 and the AlInAs layer 42 satisfies the following formula:

[0050]

[0051] Where D is the thickness, k is an integer greater than 1, λ is the wavelength of the incident light, and Ne is (Al x1 Ga y1 )InAs layer 31, (Al x2 Ga y2 )The refractive index of the InAs layer 41, the AlInAs layer 32 and the AlInAs layer 42.

[0052] In the above embodiment, according to formula (1), when the reflection center peaks of the first reflection layer 30 and the second reflection layer 40 change, the thickness of each layer of material can be adjusted accordingly.

[0053] For example, (Al x1 Ga y1 )The band gap wavelength of the InAs layer 31 is 1287nm, (Al x2 Ga y2 )The band gap wavelength of the AlInAs layer 41 is 1204nm. According to the above formula (1), the thickness of the first reflective layer 30 and the second reflective layer 40 is adjusted so that the central reflection peak of the overall reflective layer formed by the first reflective layer 30 and the second reflective layer 40 is 1300nm. In this embodiment, the thickness of the AlInAs layer 32 and the AlInAs layer 42 can be adjusted to 100.5nm. x1 Ga y1 )The thickness of the InAs layer 31 is 93 nm, (Al x2 Ga y2 )The thickness of the InAs layer 41 is 95 nm.

[0054] In one embodiment, Figure 2 As shown, the photodetector structure further includes an ohmic contact layer 70, which is used for contact connection with the metal electrode to facilitate the output of current. Exemplarily, the ohmic contact layer 70 is a P-type doped GaInAsP layer.

[0055] In the above-mentioned photodetector structure, the incident light is first received by the window layer 60, and the incident light enters the absorption layer 50 for conversion of photoelectric signals. Among them, the incident light overflowing from the absorption layer 50 will be reflected by the first reflection layer 30 and the second reflection layer 40 with high reflectivity into the absorption layer 50 to continue to complete the photoelectric conversion. After the photogenerated carriers excited by the incident light in the absorption layer 30 migrate in the internal structure of the detector, they pass through the ohmic contact layer 70 and finally reach the electrodes at both ends of the detector to complete the detector's response to the light signal. Among them, the metal electrode is connected to the ohmic contact layer 70 at the top of the structure. Since the contact resistance between the ohmic contact layer 70 and the metal electrode is very small compared with other semiconductor epitaxial layers, when current flows, the voltage drop on the ohmic contact layer 70 is much smaller than the voltage drop of the semiconductor device itself, and will not cause a significant change in the equilibrium carrier concentration inside the semiconductor.

[0056] In one embodiment, Figure 3 As shown, the photodetector structure may further include a charge layer 80 and a multiplication layer 90. Exemplarily, the charge layer 80 is an N-type doped InP layer, and the multiplication layer is an undoped InP layer. The charge layer 80 is grown after the window layer 60, and the multiplication layer 90 is grown after the charge layer 80.

[0057] In the above embodiment, the charge layer 80 is used to control the electric field of the absorption layer 50 and the multiplication layer 90, so that the electric field of the multiplication layer is high enough to cause the avalanche multiplication effect. The electric field of the absorption layer is low enough to suppress the leakage current and completely deplete the depletion region of the avalanche photodetector. The multiplication layer 90 is used to cause the photogenerated carriers entering the layer region to undergo an avalanche multiplication effect, that is, the carriers converted from the absorption layer 50 provide a strong electric field, so that the photogenerated carriers that obtain energy collide with atoms and ionize, further generating more photogenerated carriers, achieving the effect of amplifying the current, so that the sensitivity and responsiveness of the photodetector of this embodiment are higher.

[0058] In one embodiment, a photodetector structure includes N-type doping with a concentration of 5*10 18 cm -3 The InP substrate is 10, and the concentration of N-type doping is 2*10 18 An InP buffer layer 20, an N-type doped first reflective layer 30, an N-type doped second reflective layer 40, an undoped GaInAs absorption layer 50, an N-type doped InP charge layer 80, an undoped InP multiplication layer 90, a P-type doped InP window layer 60 and a P-type doped GaInAsP ohmic contact layer 70.

[0059] The first reflective layer 30 includes alternately stacked (Al 0.172 Ga 0.301)InAs layer 31 and AlInAs layer 32, the second reflective layer includes alternately stacked (Al 0.221 Ga 0.252 )InAs layer 41 and AlInAs layer 42.

[0060] (Al 0.172 Ga 0.301 )The interface between the InAs layer 31 and the AlInAs layer 32, (Al 0.221 Ga 0.252 )The interface between the InAs layer 41 and the AlInAs layer 42 is Delta doped.

[0061] The number of AlInAs layers 32 of the first reflective layer 30 is 34, that is, the number of pairs of the first reflective layer is 34. The number of AlInAs layers 42 of the second reflective layer 40 is 10, that is, the number of pairs of the first reflective layer is 10.

[0062] The thickness of the AlInAs layer 32 and the AlInAs layer 42 are both 100.5 nm. 0.172 Ga 0.301 )The thickness of the InAs layer 31 is 93 nm, (Al 0.221 Ga 0.252 )The thickness of the InAs layer 41 is 95 nm.

[0063] Based on the same inventive concept, the present application also provides a preparation method for realizing the above structure. The following is a specific implementation of the preparation method of the above structure. The listed parameters are for reference only and should be adjusted according to the actual conditions of the equipment during actual operation to obtain the best results.

[0064] In one embodiment, Figure 4 As shown, the preparation method comprises the following steps:

[0065] S401, providing a substrate.

[0066] For example, the concentration is 5*10 18 cm -3 InP is used as a substrate, and the substrate is placed in a reaction chamber of a first metal organic compound chemical vapor deposition device. The reaction conditions are set as follows: the reaction chamber pressure is 50Mbar, the growth temperature is 670°C, H2 is used as a carrier gas, and the reaction source gases include trimethyl indium (TMIn), trimethyl gallium (TMGa), trimethyl aluminum (TMAl), diethyl zinc (DeZn), silane (SiH4), arsine (AsH3) and phosphine (PH3).

[0067] S402, epitaxially growing a buffer layer on the substrate.

[0068] Exemplarily, the buffer layer is an InP buffer layer, and the buffer layer is N-type doped;

[0069] S403, epitaxially growing a first reflective layer on the buffer layer, the first reflective layer comprising alternately stacked (Al x1 Ga y1 )InAs layer and AlInAs layer, and the first reflective layer is N-type doped.

[0070] S404, epitaxially growing a second reflective layer on the first reflective layer, the second reflective layer comprising alternately stacked (Al x2 Ga y2 )InAs layer and AlInAs layer, and the second reflective layer is N-type doped, where x1 <x2。

[0071] Exemplarily, the first reflective layer includes (Al 0.172 Ga 0.301 )InAs layer and AlInAs layer, the second reflective layer includes (Al 0.221 Ga 0.252 )InAs layer and AlInAs layer.

[0072] S405 , epitaxially growing an absorption layer on the second reflective layer in sequence.

[0073] Exemplarily, a non-doped GaInAs absorption layer is epitaxially grown on the second reflective layer.

[0074] S406 , epitaxially growing a window layer and an ohmic contact layer on the absorption layer.

[0075] Exemplarily, epitaxially growing a window layer and an ohmic contact layer on an absorption layer includes the following steps: continuing to epitaxially grow an N-type doped InP window layer and an N-type doped GaInAsP ohmic contact layer on the GaInAs absorption layer; after completing the epitaxial growth of the ohmic contact layer, taking out the epitaxial wafer and placing the epitaxial wafer in a reaction chamber of a second metal organic compound chemical vapor deposition device; and performing P-type doping on the window layer and the ohmic contact layer on the epitaxial wafer.

[0076] Specifically, the reaction source gas in the reaction chamber includes diethyl zinc (DeZn) and phosphine (PH3). P-type doping of the window layer and the ohmic contact layer on the epitaxial wafer includes: increasing the temperature of the reaction chamber to decompose the DeZn and replace it with the silicon dopant in the grown epitaxial wafer to form a P-type doped InP window layer and a P-type doped GaInAsP ohmic contact layer.

[0077] In one embodiment, if Figure 5 As shown, the preparation method comprises the following steps:

[0078] S501, providing a substrate.

[0079] S502, epitaxially growing a buffer layer on the substrate.

[0080] S503, epitaxially growing a first reflective layer on the buffer layer, the first reflective layer comprising alternately stacked (Al x1 Ga y1 )InAs layer and AlInAs layer, and the first reflective layer is N-type doped.

[0081] S504, epitaxially growing a second reflective layer on the first reflective layer, the second reflective layer comprising alternately stacked (Al x2 Ga y2 )InAs layer and AlInAs layer, and the second reflective layer is N-type doped, where x1 <x2。

[0082] S505 , epitaxially growing an absorption layer on the second reflective layer in sequence.

[0083] Exemplarily, a non-doped GaInAs absorption layer is epitaxially grown on the second reflective layer.

[0084] S506 , continuing to epitaxially grow an N-type doped InP charge layer and a non-doped InP multiplication layer on the absorption layer.

[0085] S507 , epitaxially growing a window layer and an ohmic contact layer on the multiplication layer.

[0086] In the above embodiment, the charge layer is used to control the electric field of the absorption layer and the multiplication layer, so that the electric field of the multiplication layer is high enough to cause the avalanche multiplication effect. The electric field of the absorption layer is low enough to suppress the leakage current and completely deplete the depletion region of the avalanche photodetector. The multiplication layer is used to cause the photogenerated carriers entering the layer region to undergo an avalanche multiplication effect, that is, the carriers converted from the absorption layer provide a strong electric field, so that the photogenerated carriers that obtain energy collide with atoms and ionize, further generating more photogenerated carriers, achieving the effect of amplifying the current, so that the sensitivity and responsiveness of the photodetector of this embodiment are higher.

[0087] In one embodiment, epitaxially growing a first reflective layer on the buffer layer comprises: x1 Ga y1 )InAs layer is generated within a preset time, epitaxial growth is stopped and the growth (Al x1 Ga y1 )InAs layer, N-type impurities are introduced into the reaction chamber, and the temperature of the reaction chamber first decreases and then increases; x1 Ga y1)InAs layer is formed, an AlInAs layer is grown; within a preset time after the AlInAs layer is formed, epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; outside the preset time after the AlInAs layer is formed, (AlInAs layer) is grown x1 Ga y1 )InAs layer.

[0088] In one embodiment, epitaxially growing the second reflective layer on the first reflective layer comprises: x2 Ga y2 )InAs layer is generated within a preset time, epitaxial growth is stopped and the growth (Al x2 Ga y2 )InAs layer, N-type impurities are introduced into the reaction chamber, and the temperature of the reaction chamber first decreases and then increases; x2 Ga y2 )InAs layer is formed, an AlInAs layer is grown; within a preset time after the AlInAs layer is formed, epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; outside the preset time after the AlInAs layer is formed, (AlInAs layer) is grown x2 Ga y2 )InAs layer.

[0089] Exemplarily, the preset time is 1 to 10 seconds, such as 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, etc. The longer the preset time, the more N-type impurities are introduced, the higher the doping concentration between the epitaxial layer interfaces, the lower the interface resistance, and thus the less heat is generated when the detector passes a large current.

[0090] The temperature difference of the reaction chamber temperature reduction does not exceed 80°C, such as 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc.

[0091] In one embodiment, the layer closest to the absorption layer in the second reflection layer is an AlInAs layer, and the growth temperature of the AlInAs layer closest to the absorption layer is more than 20° C. lower than the growth temperature of other layer materials in the second reflection layer.

[0092] Specifically, the growth temperature of the AlInAs layer closest to the absorption layer is lower than the growth temperature of other layer materials in the second reflection layer, for example, 20° C., 30° C., 40° C., etc.

[0093] In the above embodiments, the structure of the photodetector is prepared by an epitaxial method, which is conducive to growing epitaxial layers of different materials and different thicknesses.

[0094] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0095] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A photodetector structure, characterized in that: It includes a substrate, a buffer layer, a first reflection layer, a second reflection layer, an absorption layer, and a window layer stacked in sequence from bottom to top; The first reflective layer includes alternately stacked (Al x1 Ga y1 )InAs layer and AlInAs layer; the second reflective layer comprises alternately stacked (Al x2 Ga y2 )InAs layer and AlInAs layer; Among them, x1 <x2; The number of AlInAs layers in the first reflective layer is greater than or equal to the number of AlInAs layers in the second reflective layer; The x1 Ga y1 )InAs layer and the interface of the AlInAs layer, the (Al x2 Ga y2 )The interface between the InAs layer and the AlInAs layer is Delta doped.

2. The structure according to claim 1, characterized in that: The total number of AlInAs layers in the first reflective layer and the number of AlInAs layers in the second reflective layer is greater than 40.

3. The structure according to claim 1, characterized in that: The x1 Ga y1 )InAs layer, the (Al x2 Ga y2 )The thickness of the InAs layer and the AlInAs layer satisfies the following formula: ， Wherein, D is the thickness, k is an integer greater than 1, is the wavelength of the incident light, Ne is the (Al x1 Ga y1 )InAs layer, the (Al x2 Ga y2 )The refractive index of the InAs layer and the AlInAs layer.

4. The structure according to claim 1, characterized in that 0<x1<0.5, 0<x2<0.

5.

5. The structure according to claim 1, characterized in that: The photodetector structure further includes an ohmic contact layer, which is disposed on the window layer and is used for contact connection with the metal electrode.

6. The structure according to claim 5, characterized in that The photodetector structure further includes a charge layer and a multiplication layer, wherein the charge layer is disposed on the absorption layer, and the multiplication layer is disposed on the charge layer.

7. A method for preparing a photodetector structure, characterized in that: include: epitaxially growing a buffer layer on the substrate; A first reflective layer is epitaxially grown on the buffer layer, wherein the first reflective layer comprises (Al x1 Ga y1 )InAs layer and AlInAs layer; A second reflective layer is epitaxially grown on the first reflective layer, wherein the second reflective layer comprises (Al x2 Ga y2 )InAs layer and AlInAs layer; wherein, x1 < x2; the number of AlInAs layers in the first reflective layer is greater than or equal to the number of AlInAs layers in the second reflective layer; the interfaces between the (Al x1 Ga y1 )InAs layer and the AlInAs layer, and the interfaces between the (Al x2 Ga y2 )InAs layer and the AlInAs layer are subjected to delta doping; An absorption layer and a window layer are epitaxially grown in sequence on the second reflection layer.

8. The preparation method according to claim 7, characterized in that: The step of epitaxially growing a first reflective layer on the buffer layer comprises: In the (Al x1 Ga y1 )InAs layer is generated within a preset time, epitaxial growth is stopped, and the growth of the (Al x1 Ga y1 ) N-type impurities are introduced into the reaction chamber of the InAs layer, and the temperature of the reaction chamber is first reduced and then increased; In the (Al x1 Ga y1 ) growing the AlInAs layer for a preset time after the InAs layer is generated; Within a preset time after the AlInAs layer is generated, the epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; After the AlInAs layer is formed, the AlInAs layer is grown for a predetermined period of time. x1 Ga y1 )InAs layer.

9. The preparation method according to claim 7, characterized in that: The epitaxially growing the second reflective layer on the first reflective layer comprises: In the (Al x2 Ga y2 )InAs layer is generated within a preset time, epitaxial growth is stopped, and the growth of the (Al x2 Ga y2 ) N-type impurities are introduced into the reaction chamber of the InAs layer, and the temperature of the reaction chamber is first reduced and then increased; In the (Al x2 Ga y2 ) growing the AlInAs layer for a preset time after the InAs layer is generated; Within a preset time after the AlInAs layer is generated, the epitaxial growth is stopped, and N-type impurities are introduced into the growth reaction chamber, and the temperature of the reaction chamber is first reduced and then increased; After the AlInAs layer is formed, the AlInAs layer is grown for a predetermined period of time. x2 Ga y2 )InAs layer.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The layer closest to the absorption layer in the second reflection layer is the AlInAs layer, and the growth temperature of the AlInAs layer closest to the absorption layer is lower than that of other layers in the second reflection layer by more than 20° C.

Images