Infrared photodetector and method for producing an infrared photodetector

Abstract

The invention relates to an infrared photodetector and to a method for producing an infrared photodetector, said infrared photodetector (1) having a silicon element (3), the element having a chalcogen-doped region (9) with a chalcogen concentration of at most 5∙1019 cm-3 functioning as an infrared-sensitive detection volume.

Description

[0001] Infrared photodetector and method for manufacturing an infrared photodetector

[0002] TECHNICAL FIELD

[0003] The present application relates to infrared photodetectors, i.e., photodetectors for detecting infrared radiation. The application also relates to methods for manufacturing infrared photodetectors.

[0004] BACKGROUND

[0005] Photodetectors convert received light into an electrical signal. In a semiconductor photodetector, a photon of sufficient energy generates an electron-hole pair in a semiconductor body that is electrically biased by two electrodes. The electric field generated by the two electrodes separates the generated charge carriers according to their polarity. The charge carriers thus generated by photons flow across the electrodes and induce a photocurrent in a load circuit connecting the two electrodes outside the semiconductor body. The photocurrent is a measure of the detected infrared radiation, and, for example, the photocurrent intensity can serve as a measure of the number of detected photons.

[0006] Infrared photodetectors (abbreviated as "IR photodetectors," where IR is used here and in the following as an abbreviation for "infrared") are photodetectors for detecting infrared radiation. Infrared radiation (IR radiation) is electromagnetic radiation in the wavelength range of approximately 780 nm to 1 mm and in the frequency range of approximately 300 GHz to 400 THz. Infrared photodetectors can be used, in particular, in optical data communication in the so-called O-band in the wavelength range of approximately 1260 nm to 1360 nm and in the so-called C-band in the wavelength range of approximately 1530 nm to 1565 nm. Silicon-based infrared photodetectors are of particular interest in this regard.

[0007] Silicon-based IR photodetectors can be realized, for example, using chalcogen-doped silicon; see, for example, "Extended infrared photoresponse in Te-hyperdoped Si at room temperature" (M. Wang et al., Phys. Rev. Appl. 10, p. 24054, 2018). Conventionally, such IR photodetectors are based on a silicon substrate into which a chalcogen element (e.g., tellurium) is introduced at a relatively high concentration via ion implantation. In the aforementioned article, tellurium concentrations from 0.25 atomic percent (at%) were investigated, revealing an increase in IR absorption with increasing tellurium concentration, and a tellurium concentration above 1 at% or 5 1O 20 cm -3It has been determined to be suitable for IR photodetection. The chalcogen-doped silicon substrate is conventionally subjected to sub-second thermal treatment by heat-treating it under non-equilibrium conditions, e.g., by flash lamp annealing (FLA) in the millisecond range or by pulsed laser annealing (PLA) in the nanosecond range. This process involves discontinuous energy input, resulting in local melting and subsequent rapid recrystallization of the chalcogen-doped areas on the irradiated surface of the silicon substrate. The heating remains essentially confined to the near-surface volume of the silicon substrate below the irradiated area, and the doping profile of the chalcogen doping is largely preserved even at the high doping concentrations used.Such short-term tempering processes, in which the tempering time is in the sub-second range and the treatment time is a fraction of a second, are also referred to as ultra-short-term tempering processes.

[0008] The present application aims to provide a cost-effective silicon-based infrared photodetector, particularly for use in the optical telecommunications bands O to U in the wavelength range of 1200 nm to 1700 nm, which enables improved detection of infrared radiation. The application also aims to provide cost-effective and straightforward methods for manufacturing such silicon-based infrared photodetectors.

[0009] Such infrared photodetectors and methods for manufacturing corresponding infrared photodetectors are provided by the independent claims. Advantageous embodiments are described in the dependent claims.

[0010] Features and advantages of the disclosed object will become apparent from the following detailed description and the accompanying figures. The elements and structures shown in the schematic figures are not necessarily drawn to scale. Identical reference symbols refer to identical or corresponding elements, structures, and features. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 shows a schematic cross-section through an infrared photodetector according to one embodiment.

[0012] Figure 2 shows a flowchart of a method for manufacturing an infrared photodetector according to one embodiment.

[0013] Figure 3 shows in the upper part a geometry of an infrared photodetector according to an embodiment in a top view and in the lower part a cross-section through a section of the infrared photodetector.

[0014] Figure 4 shows a doping profile for an n-doped region (Figure 4a), a doping profile for a p-doped region (Figure 4b), and two different doping profiles for a chalcogen-doped region (Figure 4c).

[0015] Figure 5 shows the dark characteristic curves of infrared photodetectors with a geometry according to Figure 3 for different configurations.

[0016] Figure 6 shows the wavelength dependence of the response of infrared photodetectors with a geometry according to Figure 3 for different configurations.

[0017] Figure ? shows a schematic cross-section through an infrared photodetector according to another embodiment.

[0018] DETAILED DESCRIPTION

[0019] Infrared photodetectors and methods for manufacturing an infrared photodetector are explained below, whereby the features described in relation to the infrared photodetectors can be applied analogously to the manufacturing methods and vice versa.

[0020] According to one aspect, a detector for capturing or detecting infrared radiation is provided, which is also referred to as a photodetector or infrared photodetector. The infrared photodetector can be specifically designed for detecting infrared radiation in the wavelength range of 1200 nm to 1700 nm (corresponding to optical telecommunications bands O to II).

[0021] The infrared photodetector comprises a silicon element. The silicon element is preferably single-crystal. Apart from the doped areas described below, the silicon element also preferably consists of undoped silicon.

[0022] A chalcogen-doped region is formed within the silicon element, meaning a region doped with a chalcogen element. The chalcogen-doped region is formed in such a way that it has a maximum chalcogen concentration of 5 to 10⁻⁵ mg / cm³. 19 cm -3 exhibits a chalcogen concentration of 5 10 19 cm -3 This corresponds to a chalcogen concentration of 0.1 atomic percent (At%) in silicon. The chalcogen-doped region can also be referred to as the chalcogen-containing region.

[0023] It has been shown that silicon with such low chalcogen concentrations of a maximum of 5 10 19 cm -3or 0.1 at% enables effective detection of infrared radiation. Because infrared photodetectors can be manufactured with such low chalcogen concentrations, they require correspondingly little material and have correspondingly shorter production times (e.g., implantation times) and manufacturing costs. It has also been shown that on silicon with such low chalcogen concentrations of at most 5 to 10⁻⁶, effective detection of infrared radiation is possible. 19 cm -3 Infrared photodetectors based on 0.1 at% or silicon-based infrared photodetectors with higher chalcogen concentrations offer better values ​​in terms of responsiveness, sensitivity and / or rectification ratio, especially at room temperature.

[0024] The chalcogen-doped region exhibits increased absorption of incident infrared radiation, whereby infrared radiation is absorbed within the chalcogen-doped region, generating electron-hole pairs. The chalcogen-doped region thus functions as a detection-sensitive area, or IR-sensitive detection volume, of the infrared photodetector. The infrared photodetector is designed such that the chalcogen-doped region is accessible to external infrared radiation (at least in one direction) from outside the photodetector, or is not shielded against such external infrared radiation (at least in one direction), so that, during the intended use of the infrared photodetector, infrared radiation to be detected can enter the chalcogen-doped region. For example,The infrared photodetector may be provided that it has a radiation entry window or radiation entry surface for receiving and introducing infrared radiation to be detected, and that the chalcogen-doped region is arranged behind the radiation entry surface (i.e., on the side of the radiation entry surface opposite the radiation entry side) such that infrared radiation incident on the radiation entry surface from the outside enters the chalcogen-doped region. In particular, it may be provided that the radiation entry surface is exposed or uncovered on the outside and is not covered, for example, by metallic layers (e.g., in the form of electrodes). The radiation entry surface may, for example, be a surface (i.e., a partial area of ​​the total outer surface) of the silicon element or silicon substrate.It is provided that the chalcogen-doped region is or will be formed adjacent to the surface of the silicon element, wherein the radiation entry surface may comprise or be defined by the surface of the chalcogen-doped region adjacent to the surface of the silicon element.

[0025] The infrared photodetector is designed to detect electrical charge carriers generated in the chalcogen-doped region through the absorption of infrared radiation. Specifically, the infrared photodetector is designed to detect infrared radiation based on electrical charge carriers generated in the chalcogen-doped region through the absorption of infrared radiation.

[0026] To operate the infrared photodetector, it can, in particular, have electrical contacts or electrodes by means of which the infrared photodetector can be electrically contacted. Accordingly, the infrared photodetector can be provided with a first electrode and a second electrode for electrical contact. Each of these two electrodes is in physical and electrical contact with the silicon element, with the first and second electrodes contacting the silicon element at different positions. An electrical voltage can be applied to the silicon element by means of the two electrodes, thereby generating an electric field in the silicon element.Charge carriers generated by the absorption of IR radiation in the chalcogen-doped region can be separated according to their polarity using an electric field and detected by the two electrodes, generating an electrical signal that serves as the output signal of the infrared photodetector. Specifically, charge carriers generated by the absorption of IR radiation in the chalcogen-doped region can be separated according to their polarity using an electric field and detected by the two electrodes, generating a photocurrent, which then serves as the output signal of the infrared detector.

[0027] Accordingly, the infrared photodetector can be configured to have two electrodes arranged in contact with the silicon element such that electrical charge carriers generated in the chalcogen-doped region by absorption of infrared radiation can be separated according to their polarity by means of an electric field generated by applying an electrical voltage between the two electrodes, thereby generating an electrical signal (e.g., a photocurrent flowing between the two electrodes). Furthermore, the infrared photodetector can be configured to apply a corresponding electrical voltage between the two electrodes. Additionally, the infrared photodetector can be configured to detect the generated electrical signal and, for example, to detect or capture infrared radiation to be detected based on the detected electrical signal.In particular, it may be provided that the infrared photodetector is designed to detect the photocurrent generated between the two electrodes and is designed, for example, to detect or capture infrared radiation to be detected based on the detected photocurrent.

[0028] According to one embodiment, the silicon cell has a p-doped region in addition to the chalcogen-doped region. In the p-doped region, the silicon cell is doped with foreign atoms that act as acceptors, such as boron or another element from group 3 of the periodic table.

[0029] It can be provided, in particular, that the chalcogen-doped region and the p-doped region in the silicon element are arranged to form a pn junction, for example, by placing the chalcogen-doped region and the p-doped region in direct contact with each other. In this regard, it can be provided that the first electrode is in contact with the chalcogen-doped region and the second electrode is in contact with the p-doped region, so that by applying a corresponding electrical voltage between the two electrodes, charge carriers generated in the chalcogen-doped region by absorption of IR radiation can be separated and detected according to their polarity. Chalcogens act as donors or n-type dopants in silicon, in particular as divalent donors.

[0030] According to another embodiment, the silicon cell has an n-doped region in addition to the chalcogen-doped region and the p-doped region. In the n-doped region, the silicon substrate is doped with foreign atoms that act as donors, such as phosphorus or another element from group 5 of the periodic table. In the present context, the term "n-doped region" refers to a region with n doping that is not identical to, but additionally provided to, the chalcogen-doped region, unless otherwise indicated by the context.

[0031] Accordingly, the silicon element can be provided with a chalcogen-doped region, an n-doped region, and a p-doped region, wherein the n-doped region and the p-doped region are arranged at a distance from each other. According to this embodiment, it can be provided, in particular, that the chalcogen-doped region is located at a position between the n-doped region and the p-doped region with respect to a direction defined by a connecting line between the n-doped region and the p-doped region. For example, it can be provided that the chalcogen-doped region is located between the n-doped region and the p-doped region.In the design of the silicon element with a chalcogen-doped region, an n-doped region and a p-doped region, it can in particular be provided that the first electrode is arranged in contact with the n-doped region and the second electrode is arranged in contact with the p-doped region, so that by applying a corresponding electrical voltage between the two electrodes charge carriers that were generated in the chalcogen-doped region by absorption of IR radiation can be separated and detected according to their polarity.

[0032] Each of the two electrodes consists of an electrically conductive material, wherein, for example, each of the two electrodes can be made of a metallic material and can, for example, comprise one or more metals. It can be provided that each of the electrodes has a stack of layers comprising a first layer and a second layer, wherein the first layer consists of a first metal and the second layer consists of a (different) second metal, and wherein the first layer is or will be in physical contact with the respective doped area, and the second layer is or will be in physical contact with the first layer on the side facing away from the respective doped area. It can be provided, for example, that the first metal is titanium and the second metal is gold. The first layer preferably has a smaller thickness than the second layer.

[0033] According to another aspect, a method for manufacturing an infrared photodetector with a corresponding silicon element or the use of a corresponding method for manufacturing an infrared photodetector is provided.

[0034] Such a silicon element with a corresponding chalcogen-doped region can be produced, for example, by first providing a silicon element. Preferably, the provided silicon element is a single-crystal silicon element, i.e., it consists of single-crystal silicon. More preferably, the provided silicon element is an undoped silicon element, i.e., it consists of undoped silicon (also referred to as intrinsic silicon). It can therefore be provided, in particular, that the provided silicon element is a single-crystal, undoped silicon element.

[0035] In the silicon element, a chalcogen-doped region is formed such that the chalcogen-doped region has a maximum chalcogen concentration of 5 to 10⁻⁵. 19 cm -3 exhibits. The formation of the chalcogen-doped region can be achieved in particular by introducing a respective chalcogen into the silicon element via ion implantation.

[0036] When the infrared photodetector or the silicon element is designed with a p-doped region, or with a p-doped region and an n-doped region (in addition to the chalcogen-doped region), these regions are also formed in the silicon element. This can be achieved, for example, by ion implantation of corresponding foreign elements into the silicon substrate. The chalcogen-doped region, the p-doped region, and, if applicable, the n-doped region can be formed in any order.

[0037] According to one embodiment, the manufacturing process also includes a thermal treatment performed after the formation of the chalcogen-doped region. For example, the thermal treatment may be carried out after chalcogen ion implantation. In a configuration of the infrared photodetector or the silicon element with a p-doped region or with a p-doped region and an n-doped region (in addition to the chalcogen-doped region), it may be particularly possible to perform the thermal treatment after the chalcogen-doped region, the p-doped region, and optionally the n-doped region have been formed in the silicon element. Accordingly, it may be possible, for example, to perform the thermal treatment after the chalcogens, the p-doped atoms, and optionally the n-doped atoms have been introduced into the silicon substrate by means of ion implantation. The thermal treatment may also be referred to as heat treatment.During the thermal treatment, the silicon element is heated to a temperature of at least 800 °C for a duration of at least 3 seconds, with the entire silicon element maintaining a temperature of at least 800 °C for this continuous period. Preferably, the silicon element is heated to a temperature of at least 900 °C for a duration of at least 5 seconds, with the entire silicon element maintaining a temperature of at least 900 °C for this continuous period. The duration is preferably a maximum of 30 seconds. Furthermore, the heat treatment is preferably carried out in such a way that no melting of the silicon element occurs during the entire heat treatment, i.e., that no melting of the silicon element takes place at any point within the silicon element.Accordingly, the heat treatment is carried out such that the temperature of the silicon element remains below its melting point throughout the entire heat treatment. For example, the temperature during the thermal treatment may be limited to a maximum of 1200 °C. Specifically, it may be stipulated that the entire silicon element, including the chalcogen-doped region, is heated to a temperature between 800 °C and 1200 °C (preferably between 900 °C and 1200 °C) for a continuous period of between 3 and 30 seconds (preferably between 5 and 30 seconds).It is provided that the silicon element is brought to a predetermined temperature (also referred to as the annealing temperature) for a predetermined period (also referred to as the annealing duration) during thermal treatment, wherein the entire silicon element is maintained at the annealing temperature for the entire annealing duration, and wherein the annealing duration is at least 3 seconds (preferably at least 5 seconds) and the annealing temperature is at least 800 °C (preferably at least 900 °C), and it may also be provided that the annealing duration is at most 30 seconds and / or the annealing temperature is at most 1200 °C. The thermal treatment is preferably carried out by means of a continuous, uninterrupted energy input into the silicon element throughout the entire thermal treatment or annealing duration. For example,It is intended that the energy input for annealing the silicon element is achieved by irradiating the silicon element with electromagnetic radiation, e.g., by irradiating the silicon with a halogen lamp or a laser. This thermal treatment can also be referred to as rapid thermal annealing (RTA). It has been shown that silicon elements produced using the aforementioned parameters for thermal treatment with a relatively long annealing time of at least 3 seconds exhibit better values ​​in terms of response, sensitivity, and / or gain compared to silicon elements produced using shorter annealing times (especially in the sub-second range), particularly in combination with the aforementioned low chalcogen concentrations.It has been shown in particular that the values ​​achievable with these parameters for IR absorption, lifetime, and the mobility of the resulting electrical charge carriers, in combination, enable particularly effective IR detection. The aforementioned heat treatment parameters also allow for the simultaneous activation of the chalcogen dopants, the p-doped dopants in the p-doped region, and the n-doped dopants in the n-doped region. Furthermore, the corresponding manufacturing process is compatible with standard methods for the fabrication of silicon-based microelectronics.

[0038] It can be provided that the thermal treatment takes place under an inert gas atmosphere, in particular under an oxygen-free atmosphere, e.g., under a nitrogen atmosphere. It can also be provided that the thermal treatment takes place under a flowing inert gas atmosphere, whereby the silicon element is exposed to a predetermined volume flow of a suitable inert gas during the thermal treatment. This prevents undesirable reactions and ensures a consistently high quality of the produced silicon substrates.

[0039] When the infrared photodetector or the silicon element is designed with a p-doped region or with a p-doped region and an n-doped region (in addition to the chalcogen-doped region), it can also be provided that first the p-doped region and / or the n-doped region is formed, followed by a thermal pretreatment, after completion of the thermal pretreatment the chalcogen-doped region is formed, and then the thermal treatment provided for after the formation of the chalcogen-doped region, as described above, is carried out. According to this embodiment, the manufacturing process thus comprises a thermal pretreatment that takes place after the formation of the p-doped region and / or the n-doped region and before the formation of the chalcogen-doped region, and a thermal treatment that takes place after the formation of the chalcogen-doped region.Thermal pretreatment can also be referred to as heat pretreatment. During thermal pretreatment (which occurs before the formation of the chalcogen-doped region), the silicon element is heated to a temperature higher than the highest temperature present during the thermal treatment (which occurs after the formation of the chalcogen-doped region).

[0040] In particular, it may be provided that during thermal pretreatment, the silicon element is heated to a predetermined temperature (also referred to as the pretreatment temperature) for a predetermined continuous period of time (also referred to as the pretreatment duration), whereby the entire silicon element is maintained at the pretreatment temperature throughout the entire pretreatment duration, and wherein the pretreatment temperature is higher than the highest temperature present during the thermal treatment. It may be provided, in particular, that the pretreatment temperature is higher than the tempering temperature. It may be provided that the pretreatment duration is at least 3 seconds (preferably at least 5 seconds) and the pretreatment temperature is at least 1000 °C (preferably at least 1100 °C).Furthermore, it may be stipulated that the pretreatment duration is a maximum of 30 seconds and / or the pretreatment temperature is lower than the melting point of silicon and, for example, a maximum of 1200 °C. In any case, the respective temperatures are set such that the highest temperature present during the thermal pretreatment (before the formation of the chalcogen-doped region) is higher than the highest temperature present during the thermal treatment (after the formation of the chalcogen-doped region).

[0041] The thermal pretreatment is preferably carried out by means of a continuous, uninterrupted energy input into the silicon element throughout the entire thermal pretreatment period. For example, the energy input for tempering the silicon element during thermal pretreatment can be achieved by irradiating the silicon element with electromagnetic radiation, e.g., by irradiating the silicon with a halogen lamp or a laser.

[0042] It has been shown that the two-stage heat treatment process described above, with a heat pretreatment after the formation of the p-doped and / or n-doped region and a heat treatment after the formation of the chalcogen-doped region, enables further improvements in response, sensitivity, and / or amplification. Such a two-stage heat treatment process allows, in particular, for a highly effective activation of the p-doped and / or n-doped and chalcogen-doped elements. The thermal pretreatment can also be carried out under an inert gas atmosphere, especially an oxygen-free atmosphere, e.g., a nitrogen atmosphere.In particular, the thermal pretreatment can be carried out under a flowing inert gas atmosphere, whereby the silicon element is exposed to a predetermined volume flow of a suitable inert gas during the thermal pretreatment. This can help prevent undesirable reactions and ensure a consistently high quality of the produced silicon substrates.

[0043] The infrared photodetector comprises a silicon element with a chalcogen-doped region, and may also include a p-doped region and, optionally, an n-doped region (in addition to the chalcogen-doped region). The chalcogen-doped region, the p-doped region, and the n-doped region are each partial volumes of the silicon element doped with the corresponding dopants.

[0044] The chalcogen concentration in the chalcogen-doped area is a maximum of 5 to 10. 19 cm -3 It is preferably provided that the silicon element does not have a chalcogen concentration exceeding 5 10 at any point. 19 cm -3 It may be provided, in particular, that the silicon element does not have a chalcogen concentration at any point that is greater than the chalcogen concentration present in the chalcogen-doped region (functioning as the detection-sensitive area sensitive to infrared radiation to be detected, or IR-sensitive detection volume of the infrared photodetector). It may also be provided, in particular, that the silicon element does not have any chalcogen doping outside this chalcogen-doped region.

[0045] When the silicon element is designed with a chalcogen-doped region and a p-doped region arranged to form a pn junction (e.g., in direct contact with each other), it can be provided that the silicon element does not have a chalcogen concentration at any point that is greater than the chalcogen concentration present in the chalcogen-doped region involved in the pn junction. According to this design, it can be provided, in particular, that the silicon element has no chalcogen doping outside the chalcogen-doped region of the pn junction, but is, for example, undoped or consists of intrinsic silicon outside the p-doped region and the chalcogen-doped region of the pn junction.It can therefore be provided, in particular, that the silicon element outside the p-doped region and the chalcogen-doped region consists exclusively of silicon and contains no other semiconductors or other foreign materials.

[0046] In a silicon element configuration comprising a spaced-apart n-doped region and a p-doped region, with a chalcogen-doped region positioned between them, it can be ensured that the silicon element does not exhibit a chalcogen concentration at any point greater than the chalcogen concentration present in the chalcogen-doped region located between the n-doped and p-doped regions. According to this configuration, it can be particularly advantageous to ensure that the silicon element is not chalcogen-doped outside the chalcogen-doped region located between the n-doped and p-doped regions, but rather is undoped or consists of intrinsic silicon outside the n-doped region, the p-doped region, and the chalcogen-doped region located between them.It can therefore be provided, in particular, that the silicon element outside the n-doped region, the p-doped region and the chalcogen-doped region consists exclusively of silicon and contains no other semiconductors or other foreign materials.

[0047] The aforementioned designs minimize interference effects and, with a simple setup, enable or additionally support IR radiation detection with good response, high sensitivity and / or good amplification.

[0048] In the chalcogen-doped, n-doped, and p-doped regions, the silicon substrate is doped with different foreign elements. The chalcogen elements are those of group 16 of the periodic table, with tellurium, selenium, and / or sulfur being preferably used as chalcogens. The chalcogen concentration values ​​given for the chalcogen-doped region can therefore refer specifically to the concentration of the chalcogen atoms tellurium, selenium, and / or sulfur in the chalcogen-doped region. Preferably, the chalcogen-doped region contains only a single chalcogen element (e.g., tellurium). It can be provided, in particular, that the chalcogen present in the chalcogen-doped region is tellurium, and that the chalcogen concentration is determined by the tellurium concentration.Furthermore, it is preferably provided that in the chalcogen-doped region the concentration of oxygen atoms is smaller than the concentration of the chalcogen atoms tellurium, selenium and / or sulfur, wherein, for example, in the chalcogen-doped region the concentration of oxygen atoms is at most 10% or at most 1% of the concentration of the chalcogen atoms tellurium, selenium and / or sulfur.

[0049] According to one embodiment, the chalcogen concentration in the chalcogen-doped area is a maximum of 5 to 10. 18 cm -3 (which corresponds to a chalcogen concentration of 0.01 at%), preferably a maximum of 5 10 17 cm -3 (which corresponds to a chalcogen concentration of 0.001 at%). Such low chalcogen concentrations allow for significant improvements in response, sensitivity, and amplification.

[0050] According to another embodiment, the chalcogen concentration in the chalcogen-doped area is a maximum of 5 to 10⁻⁵. 16 cm -3 (or 0.0001 at.-%), preferably a maximum of 1-10 16 cnr 3 (or 0.00002 at%), and is therefore within the range of the solubility of chalcogens in silicon. Such low chalcogen concentrations, close to or below the chalcogen solubility in silicon, enable, in particular, infrared photodetectors with high thermal stability.

[0051] According to one embodiment, the dopant concentration or particle density of the dopant in the n-doped region (provided in addition to the chalcogen-doped region) and / or in the p-doped region is a maximum of 10 18 cm -3 Accordingly, the particle density of donors in the n-doped region and / or the particle density of acceptors in the p-doped region is at most 10 18 cm -3Such low dopant concentrations can, especially in combination with chalcogen concentrations of at most 5 to 10⁻⁵, lead to adverse effects. 16 cm -3 , to suppress unwanted leakage currents and, for example, to reduce dark current.

[0052] In an embodiment of the silicon element comprising an n-doped region and a p-doped region arranged at a distance from each other, and a chalcogen-doped region positioned between the n-doped and p-doped regions with respect to a direction defined by a connecting line between them, the chalcogen-doped region is located at a position between the n-doped and p-doped regions (e.g., between the n-doped and p-doped regions). According to one embodiment, the chalcogen-doped region is arranged at a distance from the n-doped region and / or from the p-doped region. Accordingly, it can be provided that a region of the silicon element (e.g., an unmodified section of the provided silicon element) is arranged between the chalcogen-doped region and the n-doped region, and / or that a region of the silicon element (e.g., a p-doped region) is arranged between the chalcogen-doped region and the p-doped region.B. an unmodified section of the provided silicon element). In particular, it can be provided that an undoped region of the silicon element is arranged between the chalcogen-doped region and the n-doped region, and / or that an undoped region of the silicon element is arranged between the chalcogen-doped region and the p-doped region. Accordingly, it can be provided, for example, that the chalcogen-doped region is connected to the n-doped region by means of an unmodified or undoped region of the silicon element such that the unmodified or undoped region is arranged directly adjacent to the chalcogen-doped region and the n-doped region between the chalcogen-doped region and the n-doped region. Alternatively or additionally, it can be provided, for example, that the chalcogen-doped region is connected to the n-doped region by means of an unmodified or undoped region of the silicon element such that the unmodified or undoped region is arranged directly adjacent to the chalcogen-doped region and the n-doped region.The undoped region of the silicon element is connected to the p-doped region in such a way that the unchanged, or undoped, region is directly adjacent to the chalcogen-doped region and the p-doped region is located between the chalcogen-doped region and the p-doped region. This spacing of the chalcogen-doped region enables a reduction in noise and an improvement in the NEP value (where NEP stands for "noise-equivalent power") and thus in the sensitivity of the infrared photodetector.

[0053] According to a further embodiment, the infrared photodetector has or is formed with an insulating layer made of an electrically insulating material (e.g., a SiC>2 layer), wherein the silicon element with the respective doped regions (i.e., with the chalcogen-doped region and optionally the p-doped region and optionally the n-doped region) is or is arranged on the insulating layer. Accordingly, the silicon element and the insulating layer are or are arranged in a SOI structure (where SOI stands for "silicon-on-insulator"). By means of such an SOI structure, interferences that affect infrared detection can be prevented or reduced, thereby contributing to improved measurement.The infrared photodetector and the fabrication method have been described above with reference to a single chalcogen-doped region, a single p-doped region, and a single n-doped region (in addition to the chalcogen-doped region). However, the infrared photodetector or silicon element may also be designed to have multiple chalcogen-doped regions, multiple p-doped regions, and multiple n-doped regions, configured, arranged, and electrically contacted according to the above descriptions.

[0054] The concentrations of the respective foreign atoms or dopants in the silicon element (such as the chalcogen concentration in the chalcogen-doped region, the concentration of donors in the n-doped region, and the concentration of acceptors in the p-doped region) can be expressed, for example, as particle density in cm³. -3or can also be expressed as a mole fraction in the unit atomic percent (At%). The particle density, which can also be called number density, indicates the number of each dopant atom per volume in a correspondingly doped volume of the silicon cell. The mole fraction in atomic percent indicates the percentage of each dopant atom in relation to the total number of atoms in a correspondingly doped volume of the silicon cell. Since an undoped silicon crystal contains approximately 5 10 22 Silicon atoms per cm 3 exhibits, i.e., a particle density of ns, = 5-10 22 cm -3 This corresponds to a particle density no of the dopants of no = 5 1O 20 cm -3 a dopant concentration of 1 at.%. For the conversion between atomic percent values ​​and particle density values ​​of the respective dopant concentration in the silicon substrate, it should be assumed that 1 at.% corresponds to a particle density of 5 1O 20 cm -3This corresponds to a given dopant concentration, which can also be referred to as the dopant content.

[0055] The described features enable the development of infrared photodetectors with good responsiveness, sensitivity, and / or rectification ratios, particularly at room temperature. These infrared photodetectors can operate without cooling or be used to detect infrared radiation without cooling. It is therefore possible to design the infrared photodetector without a cooling device. Furthermore, these infrared photodetectors can operate without cooling even at temperatures above 0 °C (e.g., at room temperature of 20 °C and above) or be used to detect infrared radiation at such temperatures without cooling.Infrared photodetectors can be used, in particular, for optical data communication in the wavelength range of 1200 nm to 1700 nm (corresponding to optical telecommunications bands O to II), especially for data communication in the O-band in the wavelength range of approximately 1260 nm to 1360 nm and in the C-band in the wavelength range of approximately 1530 nm to 1565 nm. Accordingly, a data communication device for data communication in the infrared wavelength range (especially in the wavelength range of 1200 nm to 1700 nm) is provided, which includes an infrared photodetector according to one of the embodiments described above and is designed to receive data in the corresponding wavelength range by means of the infrared photodetector. The data communication device can, for example, be a data receiving device. The data communication device can, for example, be a telecommunications device.

[0056] The following detailed description refers to the accompanying figures. The figures show, among other things, specific embodiments for realizing the invention. In addition to the embodiments shown and described in the figures, further embodiments exist. Structural and / or logical modifications to the embodiments shown and explained in the figures are possible without deviating from the claimed subject matter. In particular, features of the embodiments shown and explained in the figures can be combined with one another, unless otherwise indicated by the context. Directional terms such as "front," "back," "bottom," "top," etc., are used with reference to the orientation of the described figures.

[0057] Figure 1 shows a cross-section through an infrared photodetector 1 according to one embodiment. The infrared photodetector 1 has a silicon element 3 in the form of a silicon substrate 3. The silicon substrate 3 has an n-doped region 5, a p-doped region 7, and a chalcogen-doped region 9 arranged between the n-doped region 5 and the p-doped region 7.

[0058] In the n-doped region 5, the silicon substrate 3 is doped with a foreign element acting as a donor, e.g., phosphorus. In the p-doped region, the silicon substrate 3 is doped with a foreign element acting as an acceptor, e.g., boron. According to exemplary embodiments, the doping concentration in the n-doped region and / or in the p-doped region can be a maximum of 10 18 cm -3 amounts.

[0059] In the chalcogen-doped region 9, the silicon substrate 3 is doped with a chalcogen element (e.g., tellurium), whereby the chalcogen concentration (e.g., the tellurium concentration) in the chalcogen-doped region 9 is at most 5 10 19 cm -3 is. According to exemplary embodiments, it can preferably be provided that the chalcogen concentration in the chalcogen-doped area 9 is a maximum of 5 10 18 cm -3 , preferably a maximum of 5 10 17 cm -3 , is. According to further exemplary embodiments, it can be provided in particular that the chalcogen concentration in the chalcogen-doped area 9 is a maximum of 5 10 16 cm -3 is preferably a maximum of T 10 16 cm -3 It may be provided, in particular, that the chalcogen is tellurium, and that the chalcogen concentration is given by the tellurium concentration.

[0060] Silicon substrate 3 does not exhibit a chalcogen concentration at any point that is greater than the chalcogen concentration present in the chalcogen-doped region 9. In fact, silicon substrate 3 exhibits no chalcogen doping whatsoever outside of the chalcogen-doped region 9. Silicon substrate 3 is a single-crystal silicon substrate that is undoped, or intrinsically pure, outside of the n-doped region 5, the p-doped region 7, and the chalcogen-doped region 9.

[0061] The chalcogen-doped region 9 is located at a distance from the n-doped region 5 and at a distance from the p-doped region 7. An undoped section of silicon substrate 3 is located between the chalcogen-doped region 9 and the n-doped region 5. An undoped section of silicon substrate 3 is also located between the chalcogen-doped region 9 and the p-doped region 7.

[0062] The infrared photodetector 1 also has an insulating layer 10 made of an electrically insulating material, wherein the silicon element 3 with the chalcogen-doped region 9, the p-doped region 7 and the n-doped region 5 is arranged on the insulating layer 10. In this case, the electrically insulating material is, for example, SiO2, so that the insulating layer 10 is an SiO2 layer.

[0063] The infrared photodetector 3 has a first electrode 11 arranged in physical and electrical contact with the n-doped region 5 and a second electrode 13 arranged in physical and electrical contact with the p-doped region 7. Both the n-doped region 5 and the p-doped region 7 border the surface of the silicon substrate 3, with the first electrode 11 being applied to the surface of the n-type region 5 bordering the surface of the silicon substrate 3, and the second electrode 13 being applied to the surface of the p-type region 7 bordering the surface of the silicon substrate 3. The two electrodes 11 and 13 are made of a metallic material and are designed for electrical contact and operation of the infrared photodetector 3.

[0064] The chalcogen-doped region 9 also borders the surface of the silicon substrate 3. The section of the silicon substrate 3 surface located between the first electrode 11 and the second electrode 13 serves as a radiation entry surface 15 for receiving and allowing infrared radiation to be detected. The radiation entry surface 15 thus comprises the area of ​​the chalcogen-doped region 9 adjacent to the surface of the silicon substrate 3. The radiation entry surface 15 is exposed or uncovered on the outside, so that infrared radiation incident on the central section of the radiation entry surface 15 enters the chalcogen-doped region 9 and is at least partially absorbed there, generating electron-hole pairs. The radiation entry surface 15 can also be referred to as the radiation entry window 15 of the infrared photodetector 3.By means of an electrical voltage applied across the two electrodes 11, 13 and the electric field generated thereby, the charge carriers produced in this way can be separated according to their polarity in a known manner and tapped off via the electrodes by generating a photocurrent, the current strength of which can serve as a measure of the detected infrared radiation.

[0065] The infrared photodetector 1 is designed to detect electric charge carriers generated in the chalcogen-doped region 9 by absorption of infrared radiation. In particular, the infrared photodetector 1 is designed to detect infrared radiation to be detected, based on electric charge carriers generated in the chalcogen-doped region 9 by absorption of infrared radiation.

[0066] The infrared photodetector 1 is configured, in particular (e.g., by means of an evaluation device not shown), to apply an electrical voltage between the two electrodes 11, 13 such that charge carriers generated in the chalcogen-doped region 9 by absorption of infrared radiation are separated according to their polarity by means of the electric field induced by the voltage in the silicon substrate 3 and flow away via the electrodes 11, 13, forming a photocurrent. In this regard, it can be provided, in particular, that the first electrode 11, which contacts the n-doped region 5, is subjected to a positive voltage potential relative to the second electrode 13, which contacts the p-doped region 7, e.g., by connecting the first electrode 11 to the positive terminal of a voltage source provided for this purpose and the second electrode 13 to the negative terminal of the voltage source.The infrared photodetector 1 is also designed (e.g. by means of the evaluation unit) to detect the photocurrent as a measure of the detected infrared radiation and is thus designed to detect the infrared radiation based on the detected photocurrent.

[0067] Figure 2 shows a flowchart of a process for manufacturing the infrared photodetector 1 according to Figure 1.

[0068] In a first process step 17, the silicon substrate 3 with the insulating layer 10 is provided, wherein the silicon substrate 3 is, for example, a single-crystal and undoped silicon substrate 3.

[0069] In the silicon substrate 3, the n-doped region 5, the p-doped region 7, and the chalcogen-doped region 9 are formed, for example, by ion implantation of corresponding foreign elements into the silicon substrate 3. As an example, in a second process step 19, the n-doped region 5 is formed by implantation of phosphorus ions or other donor ions into the silicon substrate 3; in a third process step 21, the p-doped region 7 is formed by implantation of boron ions or other acceptor ions into the silicon substrate 3; and in a fourth process step 23, the chalcogen-doped region 9 is formed by implantation of tellurium ions or other chalcogen ions into the silicon substrate 3. The chalcogen-doped region 9 can also be referred to as the chalcogen-containing region 9.

[0070] In a fifth process step 25, the silicon substrate 3, which is provided with the chalcogen-doped region 9, undergoes a thermal treatment. Specifically, the silicon substrate 3, which is provided with the n-doped region 5, the p-doped region 7, and the chalcogen-doped region 9, undergoes a thermal treatment. During the thermal treatment, the silicon substrate 3, which is provided with the n-doped region 5, the p-doped region 7, and the chalcogen-doped region 9, is heated to a temperature of at least 800 °C and preferably at most 1200 °C for a period of at least 3 seconds and preferably at most 30 seconds. As an example, the silicon substrate 3 is heated to a temperature of 1100 °C for a period of 7 seconds, whereby the temperature of the silicon element 3 remains below its melting point throughout the entire thermal treatment.The thermal treatment preferably takes place under an inert gas atmosphere, e.g. under a flowing nitrogen atmosphere.

[0071] Instead of the single-stage heat treatment process described above, an alternative two-stage heat treatment process can be provided such that, in an intermediate step arranged between the third process step 21 and the fourth process step 23, the silicon substrate 3, provided with the n-doped region 5 and the p-doped region 7, undergoes thermal pretreatment before the formation of the chalcogen-doped region 9, and in the fifth process step 25, the silicon substrate 3, provided with the chalcogen-doped region 9, undergoes thermal treatment. When the process is designed with such a two-stage heat treatment process, the silicon substrate 3 is heated to a temperature higher during the thermal pretreatment in the intermediate step than the highest temperature present during the thermal treatment in the fifth process step 25. As an example, according to this alternative, the silicon substrate 3 can be heated to a temperature higher than the highest temperature present during the thermal treatment in the fifth process step 25.B. It may be provided that the silicon substrate 3 (not yet provided with the chalcogen-doped region 9) is heated to a temperature of 1100 °C for a period of 7 seconds during the thermal pretreatment carried out in the intermediate step, and that the silicon substrate 3 (provided with the chalcogen-doped region 9) is heated to a temperature of 900 °C for a period of 7 seconds during the thermal treatment carried out in the fifth process step 25. In a configuration of the process with such a two-stage heat treatment process, the thermal pretreatment and the thermal treatment preferably take place under an inert gas atmosphere, e.g., under a flowing nitrogen atmosphere.

[0072] In a sixth process step 27, the first electrode 11 is applied to the surface of the n-conducting region 5 adjacent to the surface of the silicon substrate 3, and the second electrode 13 is applied to the surface of the p-conducting region 7 adjacent to the surface of the silicon substrate 3.

[0073] Furthermore, the features described for the infrared photodetector 3 with reference to Figure 1 apply analogously to the method for manufacturing such an infrared photodetector described with reference to Figure 2. The infrared photodetector 3 can be designed without a cooling device and, in particular, can also be operated without cooling at temperatures above 0 °C (e.g., at room temperature of 20 °C and above) or used to detect infrared radiation at such temperatures without cooling.

[0074] The infrared photodetector 3 can be used, in particular, for optical data communication in the wavelength range of 1200 nm to 1700 nm, especially in the O-band in the wavelength range of approximately 1260 nm to 1360 nm and in the C-band in the wavelength range of approximately 1530 nm to 1565 nm. For example, the infrared photodetector 3 can be provided as a component of a data communication device for data communication in the infrared wavelength range (especially in the wavelength range of 1200 nm to 1700 nm, e.g., in the O-band in the wavelength range of approximately 1260 nm to 1360 nm and in the C-band in the wavelength range of approximately 1530 nm to 1565 nm), wherein the data communication device is configured to receive data in the corresponding wavelength range by means of the infrared photodetector 3.

[0075] Figure 3 shows in the upper part a geometry of an infrared photodetector 1 according to one embodiment in a top view, and in the lower part a section parallel to the xyz-plane of the depicted Cartesian xyz coordinate system through a section of this infrared photodetector 1 along section line 29. The infrared photodetector 3 according to Figure 3 is a planar area detector with a total area of ​​0.09 cm². 2The infrared photodetector 1 comprises a silicon substrate 3 with an n-doped region 5, a p-doped region 7, and a chalcogen-doped region 9. The infrared photodetector 1 also has a first electrode 11 arranged in contact with the n-doped region 5 and a second electrode 13 arranged in contact with the p-doped region 7. Outside the n-doped region 5, the p-doped region 7, and the chalcogen-doped region 9, the silicon substrate 3 is undoped or intrinsically pure. The silicon substrate 3 is also single-crystal. Analogous to the embodiment according to Figure 1, the infrared photodetector 1 according to Figure 3 can also be provided with an insulating layer of an electrically insulating material (e.g., a SiO2 layer) covering the entire surface of the silicon substrate 3 on the side facing away from the electrodes 11 and 13 (not shown in Figure 3).

[0076] In the embodiment shown in Figure 3, the first electrode 11 and the second electrode 13 are designed as so-called interdigital electrodes, i.e., as a pair of comb-shaped electrodes arranged in an interlocking or toothed manner. Each of the two electrodes 11, 13 is thus comb-shaped with several electrode sections extending from a common connecting section, such an electrode section also being referred to as an electrode finger.

[0077] Below the first electrode 11 (at least below the electrode fingers of the first electrode 11), the silicon substrate 3 is n-doped; below the second electrode 13 (at least below the electrode fingers of the second electrode 13), the silicon substrate 3 is p-doped, resulting in interlocking n-doped and p-doped regions. In the region midway between the first electrode 11 and the second electrode 13 (at least between the electrode fingers of the first electrode 11 and the electrode fingers of the second electrode 13), the silicon substrate 3 is chalcogen-doped.

[0078] The infrared photodetector 1 according to Figure 3 was characterized metrologically for two different chalcogen dopings. Figure 4 shows the implantation profiles used for the characterized infrared photodetectors 1 based on SRIM simulations (where SRIM stands for "Stopping and Range of Ions in Materials").

[0079] Figure 4a shows the doping profile for the n-doped region 5, where n-doping with phosphorus (P) was performed. For the n-doping, phosphorus ion implantation was carried out in three steps with different implantation parameters, namely implantation with an energy of 20 keV and an areal density of 5 × 10⁻¹⁰ 15 cm -2 , an implantation with an energy of 45 keV and an areal density of 8 10 13 cm -2 , and an implantation with an energy of 80 keV and an areal density of 3 10 14 cm -2 This results in phosphorus doping with a higher doping level, with a maximum doping concentration of approximately 1 × 10⁻⁶. 21 cm -3 in a near-surface region and a subsequent lower doping level extending to a depth of approximately 200 nm with a maximum doping concentration of approximately 2.5–10 19 cm -3The higher doping level near the surface serves to form a better ohmic contact with the first electrode 11. Figure 4a shows the resulting phosphorus concentration as a function of the implantation depth.

[0080] Figure 4b shows the doping profile for the p-doped region 7, where p-doping with boron (B) was performed. For the p-doping, boron ion implantation was carried out in three steps with different implantation parameters, namely implantation with an energy of 7 keV and an areal density of 5 10 15 cm -2 , an implantation with an energy of 32 keV and an areal density of 3 10 14 cm -2 , and an implantation with an energy of 15 keV and an areal density of 1 - 10 14 cm -2 This results in boron doping with a higher doping level, with a maximum doping concentration of approximately 1-10 21 cm -3in a near-surface region and a subsequent lower doping level extending to a depth of approximately 200 nm with a maximum doping concentration of approximately 2.5–10 19 cm -3 , where the higher doping level near the surface serves to form a better ohmic contact with the second electrode 13. Figure 4b shows the resulting boron concentration as a function of the implantation depth.

[0081] Chalcogen doping was carried out using tellurium (Te), with two different variants for tellurium doping being investigated, which are shown in Figure 4c.

[0082] For the first doping variant, tellurium was implanted in two steps with different implantation parameters, namely an implantation with an energy of 50 keV and an areal density of 1.25-10 14 cm -2, and an implantation with an energy of 150 keV and an areal density of 3.12-10 14 cm -2 This results in tellurium doping with a doping concentration of approximately 5 10 µm extending to a depth of approximately 100 nm. 19 cm- 3This corresponds to a tellurium concentration of approximately 0.1 at% in silicon. In Figure 4c, the upper characteristic curve labeled "0.1 at%" shows the resulting tellurium concentration as a function of the implantation depth. For this doping profile with a near-surface tellurium doping of approximately 0.1 at%, an infrared photodetector 1 with a geometry according to Figure 3 was fabricated and investigated. In this geometry, the n-region 5, the p-region 7, and the electrode fingers each have a width of a = 15 pm, the chalcogen-doped region 9 also has a width of b = 15 pm, and there is a distance of c = 60 pm between the n-doped region 5 and the p-doped region 7. The infrared photodetector 1 according to this first doping variant with a near-surface tellurium doping of approximately 0.1 at% and the geometry described above is also referred to as the 0.1% configuration.

[0083] For the second doping variant, tellurium ion implantation was performed in two steps with different implantation parameters, this time with an energy of 50 keV and an areal density of 1.25-10 11 cm -2 , and an implantation with an energy of 150 keV and an areal density of 3.12-10 11 cm -2 This results in tellurium doping with a doping concentration of approximately 5 10 µm extending to a depth of approximately 100 nm. 16 cm- 3This corresponds to a tellurium concentration of approximately 0.0001 at% in silicon. In Figure 4c, the lower characteristic curve labeled "0.0001 at%" shows the resulting tellurium concentration as a function of the implantation depth. For this doping profile with a near-surface tellurium doping of approximately 0.0001 at%, an infrared photodetector 1 with a geometry according to Figure 3 was fabricated and investigated, in which the n-region 5, the p-region 7, and the electrode fingers each have a width of a = 15 pm, the chalcogen-doped region 9 has a width of b = 5 pm, and there is a distance of c = 15 pm between the n-doped region 5 and the p-doped region 7. The infrared photodetector 1 according to this second doping variant with a near-surface tellurium doping of approximately 0.0001 at% and the geometry described above is also referred to as the 0.0001% configuration.

[0084] To fabricate the corresponding versions of the infrared photodetector 1, an undoped or intrinsic silicon substrate 3 was first provided, and then the respective n-doped regions 5, p-doped regions 7, and chalcogen-doped regions 9 were formed by ion implantation with the parameters described above. Subsequently, the silicon substrate 3 doped in this way underwent thermal treatment to activate the three dopants phosphorus, boron, and tellurium. Following the thermal treatment, the first electrode 11 and the second electrode were deposited, each electrode being formed as a two-layer stack consisting of a 10 nm thick titanium layer and a 120 nm thick gold layer. The titanium layer was first deposited onto the n-doped region 5 or the p-doped region 7, and then the gold layer was deposited onto the titanium layer.

[0085] For the 0.1% configuration of the infrared photodetector 1 with a near-surface tellurium doping of approximately 0.1 at%, two different heat treatment variants of the doped silicon substrate 3 were investigated.

[0086] For the first heat treatment variant, the doped silicon substrate 3 was annealed using pulsed laser annealing (PLA), by irradiating the side of the silicon substrate 3 with the doped regions 5, 7, 9 using a pulsed laser with an energy density of 1.1 J / cm². 2The surface was scanned. In this process, only a near-surface region of the silicon substrate 3 is briefly heated and melted locally for 30 nanoseconds, whereas no significant global heating of the entire silicon substrate 3 occurs, and, for example, the side of the silicon substrate 3 facing away from the laser radiation remains essentially at room temperature. The infrared photodetector 1 produced with this first heat treatment variant using PLA, with a near-surface tellurium doping of approximately 0.1 at%, is also referred to as the 0.1% PLA configuration.

[0087] For the second heat treatment variant, the entire doped silicon substrate 3 was heated to a temperature of 1100 °C for a continuous period of 7 seconds using rapid thermal annealing (RTA). This was achieved by irradiating the silicon substrate 3 from its doped side with halogen lamps. The infrared photodetector 1 produced using this second heat treatment variant via RTA, with a near-surface tellurium doping of approximately 0.1 at%, is also referred to as the 0.1% RTA configuration.

[0088] For the 0.0001% configuration of the infrared photodetector 1 with a near-surface tellurium doping of approximately 0.0001 at%, only the second heat treatment variant was investigated; that is, the entire doped silicon substrate 3 was heated to a temperature of 1100 °C for a period of 7 seconds using RTA, as described above. The infrared photodetector 1 with a near-surface tellurium doping of approximately 0.0001 at% produced using this second heat treatment variant via RTA is also referred to as the 0.0001% RTA configuration.

[0089] Figure 5 shows the dark current characteristics for the infrared photodetectors 1 according to the three aforementioned configurations. These dark current characteristics represent the measured dark current (i.e., the electric current measured without light) as a function of the applied voltage. For positive voltages, the first electrode 11, and thus the n-region 5, is connected to the negative terminal of a voltage source, while the second electrode 13, and thus the p-region 5, is connected to the positive terminal of the voltage source (forward bias). For negative voltages, the first electrode 11, and thus the n-region 5, is connected to the positive terminal of a voltage source, while the second electrode 13, and thus the p-region 5, is connected to the negative terminal of the voltage source (reverse bias).Figure 5a shows the dark characteristic curve for the infrared photodetectors 1 according to the 0.1% PLA configuration (represented in Figure 5a by the dashed line labeled "0.1% PLA") and according to the 0.1% RTA configuration (represented in Figure 5a by the solid line labeled "0.1% RTA"). Figure 5b shows the dark characteristic curve for the infrared photodetectors 1 according to the 0.0001% RTA configuration (labeled "0.0001% RTA" in Figure 5b). Based on the currents measured at voltages of +1 V and -1 V, the infrared photodetector 1 in the 0.1% PLA configuration exhibits a rectification ratio of 937 at a dark current density of 1.7–10⁻¹⁰. 4 A / cm 2The gain, or gain ratio, indicates the ratio between the current measured at a forward voltage of +1V and the current measured at a reverse voltage of -1V. The dark current density indicates the current density per unit area of ​​the detector (in this case, 0.09 cm²). 2 The infrared photodetector 1 in the 0.1% RTA configuration, however, exhibits a higher gain of 1167 based on the currents measured at a voltage of +1 V and -1 V, with a lower dark current density of 1.8–10⁻¹⁰. 5 A / cm 2 on.

[0090] The infrared photodetector 1 in the 0.0001% RTA configuration, in turn, exhibits a gain of 333 at a dark current density of 3.3-10⁻¹⁰ based on the currents measured at a voltage of +1 V and -1 V. 3 A / cm 2The lower gain and higher dark current density are attributed to the high boron and phosphorus concentrations, as well as the smaller distance of 5 pm between the n-region 5 and the p-region 7 and the chalcogen-doped region 9 in the 0.0001% configuration. Surface leakage currents are considered the primary cause, resulting from the increased diffusion coefficients of the boron and phosphorus atoms present at the annealing temperature of 1100 °C during RTA. This can be counteracted, for example, by using lower doping concentrations in the n-region 5 and the p-region 7, such as by using a maximum phosphorus concentration of 10 in the n-doped region 5. 18 cm -3 is formed and the p-doped region 7 has a boron concentration of at most 10 18 cm -3 is being trained.

[0091] Figure 6 shows the responsiveness of the infrared photodetectors 1 for the 0.1% RTA configuration and the 0.0001% RTA configuration as a function of the wavelength incident on the infrared photodetector 1 for a sub-region of the infrared spectrum. The responsiveness indicates the ratio between the electric current induced by infrared radiation incident on the infrared photodetector at a given applied voltage and the radiant power of the incident infrared radiation.

[0092] Figure 6a shows the wavelength dependence of the response of the infrared photodetector 1 for the 0.1% RTA configuration at an applied voltage of -1 V (represented in Figure 6a by the solid line labeled "-1 V") and at an applied voltage of -4 V (represented in Figure 6a by the dashed line labeled "-4 V"). The infrared photodetector 1 in the 0.1% RTA configuration exhibits a response of 1.7–10⁻¹⁰ for a wavelength of 1500 nm at an applied voltage of -1 V. 3 A / W and for an applied voltage of -4 V a response time of 6.5- 10' 3 A / W. In contrast, a corresponding infrared photodetector 1 in the 0.1% PLA configuration for a wavelength of 1500 nm and an applied voltage of -1 V exhibits a response time of 2.2–10⁻¹⁰. 5 A / W and a response rate of 2.0-10 for an applied voltage of -4 V -4A / W (not shown). Thus, these values ​​for the 0.1% RTA configuration are more than an order of magnitude higher than for the 0.1% PLA configuration. Furthermore, the infrared photodetector 1 in the 0.1% RTA configuration exhibits a quantum efficiency of 1.4–10⁻⁶ for a wavelength of 1500 nm and an applied voltage of -1 V. -3 on, whereas a corresponding infrared photodetector 1 in the 0.1% PLA configuration for a wavelength of 1500 nm for an applied voltage of -1 V only has a quantum efficiency of 1.8-10 -5 This value is therefore almost two orders of magnitude higher for the 0.1% RTA configuration than for the 0.1% PLA configuration. Quantum efficiency is a measure of the ratio between the number of charge carriers detected by the detector when photons are irradiated and the number of photons.

[0093] Figure 6b shows the wavelength dependence of the response of the infrared photodetector 1 for the 0.0001% RTA configuration for an applied voltage of -1 V (represented in Figure 6b by the solid line labeled "-1 V") and for an applied voltage of -4 V (represented in Figure 6b by the dashed line labeled "-4 V"). The infrared photodetector 1 in the 0.0001% RTA configuration exhibits a response of 2.5–10⁻¹⁰ μm for a wavelength of 1500 nm and an applied voltage of -1 V. 4 A / W and a response rate of 1.3-10 for an applied voltage of -4 V -2A / W, with the latter corresponding to the highest value for the characterized configurations. The 0.0001% RTA configuration shown in Figure 6b exhibits a rather gradual decrease in response with increasing wavelength across the considered wavelength range, whereas the 0.1% RTA configuration shows a steeper decrease.

[0094] For the configurations described, the noise-equivalent power (also known as NEP values) was determined for a wavelength of 1550 nm and a bandwidth of 70 Hz. This NEP value is a measure of the radiated power incident on the detector at a wavelength of 1550 nm for which the resulting output signal has a signal-to-noise ratio of 1 at an output bandwidth of 70 Hz. The NEP value is a measure of the sensitivity of the infrared photodetector, with a lower NEP value corresponding to higher sensitivity. Infrared photodetector 1 in the 0.1% RTA configuration exhibits an NEP value of 3.2–10⁻¹⁰ for the specified parameters. 8 W Hz' 05 on, whereas the infrared photodetector 1 in the 0.1% PLA configuration yielded a NEP value of 2.2 10' for the specified parameters. 6 W Hz' 05The infrared photodetector 1 in the 0.1% RTA configuration thus exhibits a NEP value that is more than two orders of magnitude smaller than that of the 0.1% PLA configuration, and therefore a higher sensitivity.

[0095] The infrared photodetectors 1 according to Figures 1 and 3 have a planar structure. In contrast, Figure 7 shows a cross-section through an infrared photodetector 1 according to an embodiment with a vertical structure. The infrared photodetector 1 according to Figure 7 has a silicon element in the form of a silicon substrate 3, wherein the upper section of the silicon substrate 3 is doped with a chalcogen (e.g., tellurium) to form a chalcogen-doped region 9, and wherein the lower section of the silicon substrate 3 is doped with a foreign element (e.g., phosphorus) acting as a donor to form a p-doped region 7. The chalcogen concentration in the chalcogen-doped region 9 is a maximum of 5 10 19 cm-3 . According to exemplary embodiments, it can also preferably be provided according to the embodiment shown in Figure 7 that the chalcogen concentration in the chalcogen-doped area 9 is a maximum of 5 10 18 cm -3 , preferably a maximum of 5 10 17 cm -3 , is. According to further exemplary embodiments, it can be provided in particular that the chalcogen concentration in the chalcogen-doped area 9 is a maximum of 5 10 16 cm -3 is, preferably a maximum of T10 16 cm -3 It may be provided, in particular, that the chalcogen concentration in the chalcogen-doped region 9 corresponds to or does not exceed the solubility of the chalcogen element present in the chalcogen-doped region 9 in silicon (under standard conditions with a temperature of 273.15 K and an ambient pressure of 1 bar).

[0096] In the infrared photodetector 1 according to Figure 7, the chalcogen-doped region and the p-doped region are arranged in direct contact with each other, forming a pn junction. The infrared photodetector 1 according to Figure 7 has two electrodes 11 and 13, with the first electrode 11 being in contact with the chalcogen-doped region 9 and the second electrode 13 being in contact with the p-doped region 7. At least the first electrode 11 is transparent to infrared radiation, e.g., by means of a corresponding structuring or by being made of a material transparent to infrared radiation.

[0097] In contrast to the infrared photodetector 1 according to Figures 1 and 3, the infrared photodetector 1 according to Figure 7 does not have an additional n-doped region besides the chalcogen-doped region 9. Otherwise, the explanations given with reference to the infrared photodetector 1 according to Figure 1 apply analogously with regard to the manufacture (in particular with regard to the thermal treatment), the operation and the use of the infrared detector according to Figure 7, so that reference is made in this respect to the explanations with reference to Figures 1 and 2.

[0098] List of reference symbols used

[0099] I Infrared photodetector

[0100] 3 Silicon substrate 5 n-doped region

[0101] 7 p-doped region

[0102] 9 chalcogen-doped area

[0103] 10 Insulating layer / SiCh layer

[0104] II first electrode 13 second electrode

[0105] 15 Radiation entry area / Radiation entry barrier

[0106] 17. Process step of providing the silicon substrate

[0107] 19. Procedure step of forming the n-doped region 5

[0108] 21. Process step of forming the p-doped region 7 23. Process step of forming the chalcogen-doped region 9

[0109] 25th process step of the thermal treatment

[0110] 27. Procedure step of the electrode formation 11, 13

[0111] 29 Section line

Claims

Patent claims 1. Infrared photodetector (1) for detecting infrared radiation, comprising a silicon element (3) with a chalcogen-doped region (9) with a chalcogen concentration of at most 5 10 19 cm -3 .

2. Infrared photodetector according to claim 1, wherein the chalcogen concentration in the chalcogen-doped region (9) is at most 5 10 16 cm -3 corresponds.

3. Infrared photodetector according to claim 1 or 2, wherein the silicon element (3) has a p-doped region (7).

4. Infrared photodetector according to claim 3, wherein the silicon element (3) has an n-doped region (5) in addition to the chalcogen-doped region (9).

5. Infrared photodetector according to claim 4, wherein the n-doped region (5) is arranged at a distance from the chalcogen-doped region (9) and / or the p-doped region (7) is arranged at a distance from the chalcogen-doped region (9).

6. Infrared photodetector according to claim 5, wherein the silicon element (3) is undoped in the region between the n-doped region (5) and the chalcogen-doped region (9) and / or in the region between the p-doped region (7) and the chalcogen-doped region (9).

7. Infrared photodetector according to one of claims 1 to 6, further comprising an insulating layer made of an electrically insulating material, wherein the silicon element is arranged on the insulating layer.

8. Method for manufacturing an infrared photodetector (1), comprising providing a silicon element (3) and forming a chalcogen-doped region (9) in the silicon element (3) such that the chalcogen-doped region (9) has a chalcogen concentration of at most 5 10 19 cm -3 exhibits.

9. The method of claim 8, wherein the silicon element (3) with the chalcogen-doped region (9) is subjected to a thermal treatment such that the silicon element is heated to a temperature of at least 800°C for a duration of at least 3 seconds. is brought.

10. The method of claim 9, wherein the duration is at least 5 seconds and / or the temperature is at least 900 °C.

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