Bipolar power supply for single-photon detectors

Abstract

The present invention relates to a single-photon detector arrangement for the bipolar voltage supply of single-photon detectors using voltage converters, in particular for use with a monolithically integrated quantum random number generator (iQRNG). The present invention relates to a single-photon detector arrangement and an iQRNG based thereon, comprising at least one substrate (100) made of a semiconductor material; a first pn junction (50) formed in the substrate (100) and configured as a first single-photon detector (130), wherein an operating voltage of the first single-photon detector (130) is above a supply voltage U0 provided relative to an electrical zero potential; a first voltage converter (210) configured to invert the supply voltage U0, amplify it with a first gain factor F1 greater than or equal to 1, and provide it as a first converter voltage -U1 relative to the electrical zero potential, wherein the first pn junction (50) is connected to a first differential voltage (ΔV) 1.SPAD ) is biased with respect to the first converter voltage -U1.

Description

[0001] The present invention relates to a single-photon detector arrangement for the bipolar voltage supply of single-photon detectors using voltage converters, in particular for use in a monolithically integrated quantum random number generator (iQRNG). Technological background

[0002] Random events and the determination of probabilities play a particularly prominent role in many areas of science and technology. For example, Monte Carlo simulations and secure encryption methods rely heavily on the generation of random numbers. A general distinction is made between so-called pseudo-random numbers and true random numbers. While the former are generated using deterministic formulas by pseudo-random number generators (PRNGs), and are therefore not absolutely random, non-deterministic random number generators (TRNGs) for generating true random numbers are generally based on real, unpredictable processes such as thermal or atmospheric noise, rather than on artificially generated patterns by deterministic algorithms.However, even the results of such non-deterministic random number generators based on external parameters can, depending on the underlying random element, still tend slightly towards higher or even numbers due to weak correlations, for example, and thus enable at least a partial predictability of the random numbers generated in this way.

[0003] Quantum random number generators (QRNGs), a special subgroup of TRNGs, are based on fundamental quantum processes for random number generation and are therefore, at least theoretically, not dependent on other external factors and effects that influence statistics. Quantum random number generators thus represent the currently best available source of true random numbers. Current digital QNRGs can deliver entropy rates (i.e., a sequence of bit values ​​with maximum randomness or entropy) of up to several hundred Mbps. The generated random numbers are required in both classical encryption methods and a variety of quantum computing and quantum cryptography methods to ensure secure key exchange (Secure / Quantum Key Distribution, SKD / QKD).Therefore, non-manipulable and fast QRNGs are essential for generating secure keys in cryptography.

[0004] Due to their particularly easy implementation, many QRNGs are realized as photonic QRNGs using the random properties of photons. A simple concept for generating random numbers is the behavior of a photon, which is either reflected or transmitted at a semitransparent beam splitter independently of other photons. Another approach is to utilize the random arrival times of photons at a single-photon detector. This distribution effect, based on intrinsic, fundamentally non-deterministically computable photon statistics of the photons of a corresponding photon source, can also be used to generate truly random numbers.The random numbers can be generated, in particular, via the varying time differences between two consecutive detection events on the single-photon detector, with the arrival times generally exhibiting a distribution characteristic of the type of photon source (i.e., thermal, coherent, or non-classical photon source). The combination of a photon source suitable for random number generation with a correspondingly sensitive single-photon detector is also referred to as the entropy source of the corresponding QRNG, with random number generation being determined by the temporal sequence of the individual detection events in the entropy source.A corresponding QRNG requires at least one entropy source and can include at least one additional component for evaluating the individual detection events and / or for providing a digital random number sequence suitable for further processing based on the respective arrival times of the photons. The terms entropy source and QRNG are therefore largely used synonymously in the present application.

[0005] Typically, a single-photon detector (SPD) initially generates a detector pulse from a single incident photon. This pulse is then converted into a timestamped digital representation of the detection event in a time-to-digital converter (TDC) and can be further processed accordingly. The photon sources in QRNGs are usually laser diodes (LDs) or simple light-emitting diodes (LEDs) that are highly attenuated to the single-photon level. Their emitted photons can then be recorded as SPDs with temporal resolution by one or more particularly sensitive single-photon avalanche diodes (SPADs).Such photon sources that simultaneously emit only a single photon or a few photons are also referred to as single-photon sources (SPS) in this application. However, they do not necessarily have to be true single-photon emitters, for example, based on a single isolated two-level system.

[0006] SPADs are a type of photodetector similar to photodiodes (PDs) and avalanche photodiodes (APDs), but with significantly increased sensitivity. SPADs can be digitally read and evaluated – even within a common integrated circuit. If such an integrated detector circuit is excited by individual photons, only one electron-hole pair is generated per exciting photon in the sensor-active region (absorption region). The excited electrons are drawn to the cathode by electric fields, and the excited holes are drawn to the anode. In a SPAD, the charge carriers drift through a so-called avalanche region, within which a charge avalanche is generated by enhanced impact ionization. These are therefore highly sensitive photon receiver elements that, upon activation, store a high amount of charge (approximately 105 - 10 6 electrons) with high temporal resolution.

[0007] A SPAD is typically operated in Geiger mode above its respective breakdown voltage, whereby a single photon is detected via the generated charge avalanche and subsequently registered as a single event. To reduce the dead time during registration, active or passive suppression or quenching of further charge carrier amplification can occur immediately after the onset of the avalanche formation. In addition to the SPAD, the integrated circuit can also include a so-called single-photon counter (SPC). In this case, instead of directly outputting a single detector pulse, an immediate statistical evaluation of the temporal distribution of the individual detected single-photon events is generally performed.

[0008] Statistical analysis performed in parallel with random number generation can, for example, be used to further secure the random number generation process against potential attacks. Particularly in the case of non-integrated photonic QRNGs constructed from individual components, the required transmission paths within the system offer a wide range of attack possibilities. Therefore, to increase security, such systems are implemented as compactly as possible and isolated from their external environment. In addition to avoiding potential attack scenarios, another advantage of such compact QRNGs is that natural influences from outside the system that may impair random number generation can also be minimized to the greatest extent possible.Accordingly, compact QRNGs based on photon noise are therefore primarily provided as hybrid component systems (hybrid integrated QRNGs or hiQRNGs), in which a SPS and a SPAD are connected as independent elements, for example, via planar waveguide structures or free-space coupling. However, various approaches for fully monolithically integrated QRNGs in a common substrate (monolithically integrated QNRGs or iQRNGs) are also known.

[0009] In both of these integration approaches, a suitable PLC, a highly sensitive PLC, and the associated control and evaluation electronics are typically combined in a single module. However, these components generally have very different requirements for the supply voltage to be provided. For example, in some embodiments of an iQRNG, the PLC can be a light-emitting avalanche Zener diode operated at an operating point below or close to the breakdown voltage, which is therefore also referred to as a Zener avLED. Zener avLEDs, for example in silicon BCD technology (e.g., 130 nm technology), typically have breakdown voltages < 10 V, so that an operating voltage of approximately 5 V to 10 V (e.g., approximately 7 V) is required for the PLC.However, for a SPAD also implemented using silicon BCD technology, the required operating voltage can be at least a factor of 2 higher (typically between 20 V and 30 V). For example, for a SPAD with a breakdown voltage at room temperature of approximately 17 V and an applied overvoltage of approximately 5 V during operation, the required operating voltage is approximately 22 V, which cannot be significantly reduced by simple design or layout measures. In contrast, there are the requirements for the operating voltage of the associated control and evaluation electronics, which in the silicon BCD technology mentioned as an example is typically around 2 V to 3 V. Thus, the individual voltage values ​​generally differ considerably, in the example mentioned by a factor of approximately 8 to 10 relative to a typically provided low supply voltage of approximately 2 V to 3 V.

[0010] While it is possible in principle to supply the corresponding voltage values ​​separately from separately provided power supplies, for the simplest and most compact implementation of iQRNGs, it is preferable to supply only a single external supply voltage and derive all further required voltage values ​​from this base voltage by conversion. For practical reasons, a supply voltage with an existing voltage level is preferred. Typically, these are discretely defined voltage levels of 1.8 V, 2.5 V, or 3.3 V.

[0011] In the state of the art, charge pumps are primarily used for this purpose in integrated circuits. However, other concepts for DC-DC conversion are also known, such as so-called boost converters. The latter will not be explicitly mentioned in the following, as their circuit components are generally impossible or very difficult to integrate. Integrated circuits for voltage conversion are referred to below as voltage converters. Voltage converters are specifically intended to be charge pumps, but the methods described are equally applicable to other voltage converter concepts or even mixed voltage converter concepts.

[0012] Charge pumps for increasing an input voltage are state of the art and are known, for example, from US Pat. No. 4,214,174 A. With a simple configuration, a corresponding input voltage can be almost doubled. However, depending on the circuit design, forward losses amounting to the diode voltage of the diodes used or the threshold voltage of the transistors used occur. To achieve higher voltages, several stages of charge pumps can be cascaded. However, since the area required and power dissipation also increase with each additional stage, the achievable voltage cannot be selected to be arbitrarily high. Charge pumps that invert an input voltage are also known in the state of the art and can also be implemented using simple means. A corresponding converter circuit can be found, for example, in Bloch et al. (M. Bloch, C. Lauterbach, and W. Weber).“High efficiency charge pump circuit for negative high voltage generation at 2 V supply voltage.” Proceedings of the 24th European Solid-State Circuits Conference. IEEE, 1998.).

[0013] The high supply voltages required to operate single-photon detectors, especially SPADs used as SPDs in integrated iQRNGs, cannot be efficiently and effectively realized with a conventional power supply by cascading multiple charge pumps due to their large area requirements and increasing power dissipation. The differences in the operating voltage requirements, which differ by a factor of approximately 8 to 10, pose a technical challenge.

[0014] The technical challenge to be solved is therefore to provide high operating voltages from a low supply voltage without incurring high power losses and requiring a large amount of space. In particular, to reduce the absolute terminal potentials, the operating voltages should be provided directly within an iQRNG and without separate power supplies. Description of the invention

[0015] The object of the invention is achieved by the subject matter of the independent patent claims. Preferred developments are the subject matter of the respective subclaims.

[0016] One aspect of the present invention relates to a single-photon detector arrangement comprising a substrate made of a semiconductor material; a first pn junction formed in the substrate and configured as a first single-photon detector, wherein an operating voltage of the first single-photon detector is above a supply voltage U0 provided with respect to an electrical zero potential (e.g., mass, ground, general substrate, or reference potential); a first voltage converter configured to invert the supply voltage U0 (inverting voltage converter), to amplify it with a first gain factor F1 greater than or equal to 1, and to provide it as a first converter voltage -U1 with respect to the electrical zero potential, wherein the first pn junction is biased with a first differential voltage with respect to the first converter voltage -U1.

[0017] The single-photon detector is preferably a single-photon avalanche diode (SPAD). This refers to detectors that, due to their particularly high sensitivity with high amplification and low (dark) noise, are in principle capable of detecting and proving single photons.

[0018] In contrast to the prior art, the first single-photon detector is thus bipolarly wired with respect to a supply voltage U0 provided relative to an electrical zero potential (e.g., a substrate-related zero voltage). A required high operating voltage is thus realized by both positive and negative voltage potentials with an absolute voltage lower than the operating voltage.

[0019] Since the first pn junction is biased with a first differential voltage with respect to the first converter voltage -U1, the high gain factors required compared to the electrical zero potential with conventional power supplies can be reduced to provide a specific required operating voltage. With a low supply voltage, a maximum of approximately half the otherwise required voltage gain can be achieved, i.e. in the example mentioned at the beginning with a required gain of a factor of 8 to 10, the required gain can be reduced to approximately a factor of 4 to 5 by bipolar wiring of the pn junction, whereby a corresponding gain of both the provided supply voltage and the first converter voltage -U1 compared to the electrical zero potential is required.However, even when implemented with two independent voltage converters, the area consumption and power loss are still lower than when implemented with a single voltage converter that amplifies by a factor of 8 to 10.

[0020] The substrate may preferably be a silicon substrate, wherein the single-photon detector arrangement may preferably be constructed using a modern and particularly widely applicable bipolar CMOS-DMOS technology (BCD technology).

[0021] The magnitude of the first amplification factor F1 depends not only on the magnitude of the provided supply voltage U0 but also, in particular, on the respective voltage requirements of the single-photon detector array and other circuit components to be supplied. Preferably, the first amplification factor F1 is in a range between approximately 2 and 3 and / or between approximately 4 and 5. Assuming, for example, a supply voltage of approximately 2 V to 3 V, this results in first converter voltages -U1 in the range of approximately -4 V to -9 V or -8 V to -15 V. Such relatively low amplification factors can be efficiently and effectively implemented using cascaded voltage converters. A voltage converter can also be configured to simultaneously provide several converter voltages of different magnitudes.

[0022] In particular, the present invention enables a reduction in space consumption by selecting suitable components with a lower voltage / insulation class, which also enables a complete or partial replacement of the coupling capacitors in charge pumps from the otherwise conventional MOM (metal-oxide-metal, MOM) class to the MOS (metal-oxide-semiconductor, MOS) class. By reducing the number of pump stages in charge pumps as voltage converters, the power losses can be reduced compared to direct amplification from a provided supply voltage. The concept of a bipolar circuit is fundamentally applicable to a variety of single-photon detector embodiments (e.g., conventional nSPADs or pSPADs) when the substrate-related operating voltage is too high or the provided supply voltage is too low.This is especially true when purely unipolar concepts may not be sufficient to provide the operating voltage (above the breakdown voltage) of the single-photon detectors used.

[0023] Preferably, the first differential voltage results from the difference between the supply voltage U0 and the first converter voltage -U1. With a supply voltage U0 of, for example, 2 V provided relative to the electrical zero potential and an operating voltage of 22 V required to operate the first single-photon detector (relative to the electrical zero potential, e.g., a substrate-related zero voltage), a bias voltage of the first pn junction with a first converter voltage -U1 of -20 V relative to the provided supply voltage U0 would also be possible. In this simple case, the first gain factor F1 can already be reduced from 11 times to 10 times the provided supply voltage U0. A bipolar power supply can thus significantly reduce the requirements for the required gain and thus the area consumption and power dissipation of the voltage converters used.

[0024] Preferably, the single-photon detector arrangement further comprises a second voltage converter configured to amplify the provided supply voltage U0 with a second amplification factor F2 greater than 1 and to provide it as a second converter voltage U2 relative to the electrical zero potential, wherein the first differential voltage results from the magnitude of the difference between the second converter voltage U2 and the first converter voltage -U1. In contrast to the previously described embodiment, the first pn junction is thus not biased relative to the supply voltage U0, but rather relative to a supply voltage U0 amplified by the second amplification factor F2 as the second converter voltage U2.

[0025] The second amplification factor F2 is preferably in a range between approximately 2 and 3 and / or between approximately 4 and 5. With the described circuitry, the level of the first amplification factor F1 can be reduced accordingly by a higher second amplification factor F2 while the requirements for the operating voltage of the first single-photon detector remain the same. A maximum reduction in the amplification requirements can be achieved with a bipolar circuit with approximately the same level of the first amplification factor F1 and the second amplification factor F2. The second voltage converter can be designed independently of the first voltage converter. However, it can also be a related voltage converter arrangement which can provide both the first converter voltage U1 and the second converter voltage U2. The first and second voltage converters can thus also be formed by a common voltage converter arrangement ora common voltage converter can be realized.

[0026] Preferably, the differential voltage for biasing the first pn junction is designed symmetrically or asymmetrically with respect to the electrical zero potential. A symmetrical design has the advantage that, with a high required operating voltage of the first single-photon detector and a relatively low supply voltage, the required gains can be kept as low as possible. However, even with an implementation using only the first voltage converter, the required overall gain can be roughly halved if the supply voltage is too low but still relatively high.For example, with a provided supply voltage of 11 V relative to the electrical zero potential and a required operating voltage of the first single-photon detector of 22 V, a sufficiently high first converter voltage -U1 of -11 V relative to the electrical zero potential can be provided by a single inverting first voltage converter with a first gain factor F1 equal to 1. The total gain factor of 2 required in this case can thus be achieved simply by inverting the provided supply voltage.

[0027] In other cases, however, an asymmetrical design of the differential voltage may also be advantageous. This is particularly the case if the voltage converter is to supply additional components with voltage requirements that differ from the operating voltage of the first single-photon detector. An asymmetrical design may also be preferable if additional circuit properties (e.g., capacitances and resistances within the circuit) must be taken into account.

[0028] The single-photon detector arrangement preferably further comprises a second pn junction formed in the substrate and configured as a second single-photon detector, wherein a first region located directly between the first pn junction and the second pn junction is electrically conductive. The second single-photon detector can, in particular, be configured as a single-photon avalanche diode (SPAD). Since the two pn junctions are electrically connected to one another via the first region, the pn junctions in the first region have a common electrical potential. In order for both to function as independent single-photon detectors, they must be coupled to the first region with the same polarity.

[0029] Preferably, an operating voltage of the second single-photon detector is above the supply voltage U0, and the second single-photon detector is biased with a second differential voltage relative to a common electrical potential in the first region. The second differential voltage can result, in particular, from the magnitude of a difference between two provided voltages, i.e., the supply voltage U0, the first converter voltage -U1, the second converter voltage U2, or other provided voltages. This means that the first and second single-photon detectors are each biased with a differential voltage relative to the common electrical potential in the first region.

[0030] Preferably, the second pn junction is formed below the first pn junction. This means that the pn junctions are arranged vertically one above the other in the substrate. The first pn junction and the second pn junction can preferably be deep pn junctions provided in a BCD process. These can be created, for example, by partially forming p-doped regions in a deep n-layer (n-type buried layer, NBL) of a substrate (or with swapped charge types).

[0031] A further aspect of the present invention relates to a monolithically integrated quantum random number generator (iQRNG) comprising a single-photon detector arrangement according to the invention, wherein a third pn junction configured as a photon source is formed above the first pn junction, wherein an intermediate region located directly between the first pn junction and the third pn junction is electrically conductive. Since the two pn junctions are electrically connected to one another via the intermediate region, the pn junctions in the intermediate region have a common electrical potential. In order for both elements to function as independently operated elements, they must be coupled to the intermediate region with the same polarity.

[0032] Preferably, the third pn junction is biased with a third differential voltage relative to a common electrical potential in the intermediate region. The third differential voltage can result, in particular, from the magnitude of a difference between two provided voltages, i.e., the supply voltage U0, the first converter voltage -U1, the second converter voltage U2, or other provided voltages. This means that the photon source and the first single-photon detector are each biased with a differential voltage relative to the common electrical potential in the intermediate region.

[0033] The photon source is preferably a single-photon source (SPS), configured to provide only a single photon or a few photons simultaneously. Such photon sources that provide only a single photon or a few photons simultaneously are also referred to as single-photon emitters (SPS) in this application. However, they do not necessarily have to be true single-photon emitters, for example, based on a single isolated two-level system; rather, conventional light sources (e.g., silicon LEDs) can also be configured as (quasi-)SPSs by appropriately attenuating the emission or the supplied current.

[0034] The photon source is preferably a simple diode junction, an avalanche diode, or a single-photon avalanche diode (SPAD), each configured as an emitter or quasi-emitter. The photon source can be formed in or from a direct semiconductor material (e.g., a III / V semiconductor) or, preferably, in or from an indirect semiconductor material (e.g., silicon). The formation of radiating pn junctions is known to those skilled in the art. By supplying them with only a low current and possibly additionally significantly attenuating the intensity of the generated radiation using optical filters and absorbers, these pn junctions can be utilized for QRNG applications. With appropriate attenuation, operation as a PLC is even possible.The formation in or from an indirect semiconductor material offers the particular advantage that photon generation is greatly hampered in such materials for energetic reasons and thus the effective photon generation rate is only low even with easily controllable currents during activation and operation as a PLC is possible without any additional attenuation measures.

[0035] It is also known that, under certain circumstances, photon generation and thus radiation emission can occur even in non-radiative pn junctions (e.g., pn junctions in indirect semiconductors). However, the electro-optical conversion rate is generally so low that these rather randomly generated photons can usually be neglected in the design of conventional circuits. In combination with a highly sensitive detector, such extremely weakly radiating pn junctions can also be used as photon sources in an iQRNG. What has been said for non-radiative pn junctions applies accordingly to avalanche diodes and SPADs, which are also typically assumed to be non-radiative. By appropriately selecting the operating parameters, low photon emission can also be observed and used for QRNG applications.In all of the examples mentioned, the main focus is on providing a stable photon flux with only an extremely low intensity.

[0036] The photon source can preferably be a light-emitting avalanche Zener diode (Zener avLED) operating at an operating point below or close to the breakdown voltage. The Zener avLED preferably has a breakdown voltage of <10 V, more preferably a breakdown voltage of <8 V, and even more preferably a breakdown voltage of <7 V. This type of single-photon source allows for a high single-photon rate at a relatively low operating voltage, even below and in the range of the Zener breakdown voltage. This makes Zener avLEDs particularly suitable for use as a single-photon source in an iQRNG according to the invention.

[0037] Further aspects of the present invention are disclosed in the dependent claims or in the following description of the drawings. Short description of the characters

[0038] The invention is explained in more detail below using an exemplary embodiment and the accompanying drawings. The figures show: Fig. 1 shows an exemplary embodiment of an iQRNG according to the invention with three pn junctions arranged one above the other and requiring two different operating voltages; Fig. 2 an equivalent circuit diagram for the Fig. 1 shows the arrangement of pn junctions; Fig. 3 a state-of-the-art unipolar power supply for an iQRNG; Fig. 4 shows an exemplary first embodiment of a bipolar voltage supply according to the invention in an iQRNG; Fig. 5 shows an exemplary second embodiment of a bipolar voltage supply according to the invention in an iQRNG; Fig. 6 shows an exemplary third embodiment of a bipolar voltage supply according to the invention in an iQRNG; Fig. 7 shows an exemplary embodiment of a bipolar voltage supply according to the invention in a single-photon detector arrangement; and Fig. 8 an inventive bias voltage of the pn junctions with different differential voltages. Detailed description of the invention

[0039] Detailed embodiments will now be described, illustrated by way of example in the accompanying drawings. The effects and features of these embodiments will be described with reference to the accompanying drawings. In the drawings, like reference numerals designate like elements, and redundant descriptions are omitted. The present disclosure may be embodied in various forms and should not be construed as limited only to the embodiments shown herein. Rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art.

[0040] Therefore, methods, elements, and techniques that are not necessary for a person skilled in the art to fully understand the aspects and features of the present disclosure may not be described. In the drawings, the relative sizes of elements, layers, and regions may be exaggerated for clarity.

[0041] As used herein, the term "and / or" includes all combinations of one or more of the listed elements. Furthermore, the use of "may" in describing embodiments of the present disclosure refers to "one or more embodiments of the present disclosure." In the following description of embodiments, the singular terms may also include the plural, unless the context clearly indicates otherwise.

[0042] Although the terms "first" and "second" are used to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the present disclosure. Terms such as "at least one of," when preceded by a list of elements, modify the entire list, not just the individual elements of the list.

[0043] Terms such as "substantially," "approximately," and similar terms are used as approximations rather than degrees, and are intended to account for inherent variations in measured or calculated values ​​that will be recognized by those skilled in the art. When the term "substantially" is used in connection with a characteristic that can be expressed by a numerical value, the term "substantially" means a range of at least + / - 5% of the value centered on the value.

[0044] Fig. 1 shows an exemplary embodiment of an iQRNG 200 according to the invention with three pn junctions 50, 52, 60 arranged one above the other and requiring two different operating voltages. A single-photon detector arrangement according to the invention comprises a substrate 100 made of a semiconductor material; a first pn junction 50 formed in the substrate 100 and configured as a first single-photon detector 130, wherein an operating voltage of the first single-photon detector 130 (e.g. 1st SPAD) is above a supply voltage U0 provided with respect to an electrical zero potential; a first voltage converter 210 configured to invert the supply voltage U0, to amplify it with a first amplification factor F1 greater than or equal to 1, and to provide it as a first converter voltage -U1 with respect to the electrical zero potential, wherein the first pn junction 50 is provided with a first differential voltage ΔV 1.SPADwith respect to the first converter voltage -U1. The first differential voltage ΔV 1.SPAD can, for example, result from the magnitude of the difference between the supply voltage U0 and the first converter voltage -U1.

[0045] Widely shown is a second voltage converter 220, configured to amplify the provided supply voltage U0 with a second amplification factor F2 greater than 1 and to provide it as a second converter voltage U2 with respect to the electrical zero potential, wherein the first differential voltage ΔV 1.SPAD can result from the amount of the difference between the second converter voltage U2 and the first converter voltage -U1.

[0046] A second pn junction 52 is formed in the substrate 100 and configured as a second single-photon detector 140 (e.g., 2nd SPAD), wherein a first region 22 located directly between the first pn junction 50 and the second pn junction 52 is electrically conductive. The second single-photon detector 140 is supplied with a second differential voltage ΔV 2.SPAD biased with respect to a common electrical potential in the first region 22. The second differential voltage ΔV 2.SPAD can result in particular from the magnitude of a difference between two provided voltages, ie the supply voltage U0, the first converter voltage -U1, the second converter voltage U2, or further provided voltages. This means that the first and second single-photon detectors 130, 140 are each provided with a difference voltage ΔV 1.SPAD , ΔV 2.SPADbiased, which results with respect to the common electrical potential in the first region 22.

[0047] The second pn junction 52 is formed below the first pn junction 50. A third pn junction 60, configured as a photon source 120, is formed above the first pn junction 50, wherein an intermediate region located directly between the first pn junction 50 and the third pn junction 60 is electrically conductive. The third pn junction 60 is supplied with a third differential voltage ΔV avLED biased with respect to a common electrical potential in the intermediate region. The third differential voltage ΔV avLEDcan result in particular from the magnitude of a difference between two provided voltages, ie the supply voltage U0, the first converter voltage -U1, the second converter voltage U2, or other provided voltages. This means that the photon source 120 and the first single-photon detector 130 are each supplied with a differential voltage ΔV avLED , ΔV 1.SPAD biased, which results with respect to the common electrical potential in the intermediate region. The photon source 120 can, in particular, be a light-emitting avalanche Zener diode (Zener-avLED) operated at an operating point below or close to the breakdown voltage.

[0048] The three pn junctions 50, 52, 60 can thus be configured, in particular, to form a light-emitting avalanche Zener diode (Zener-avLED) operating at an operating point below or close to the breakdown voltage as the photon source 120, a first single-photon detector 130 as the first single-photon avalanche diode (1st SPAD), and a second single-photon detector 140 as the second single-photon avalanche diode (2nd SPAD). In particular, the three pn junctions 50, 52, 60 can be arranged vertically one above the other in a common BCD substrate 100 made of a semiconductor material (e.g., silicon) using BCD technology. Preferably, the photon source 120 is configured as a single-photon source (SPS), so that only single or a few photons 128 are provided simultaneously.

[0049] Preferably, the BCD substrate 100 comprises a carrier substrate; and an epitaxial layer grown on the carrier substrate, wherein a deep pn junction 50 located in the epitaxial layer was created between the carrier substrate and the epitaxial layer by diffusion of dopants introduced into a surface of the carrier substrate below the epitaxial layer. Preferably, the first single-photon detector 130 forms an avalanche region in a region around the deep pn junction 50 and comprises an absorption region (PW / HPW) with a high-voltage p-type well HPW and a p-type well PW for converting photons into electron-hole pairs, wherein the absorption region (PW / HPW) is directly adjacent to the regions of a deep n-layer NBL (n-type buried layer) and a deep p-layer PBL (n-type buried layer) forming the deep pn junction 50."n-type buried layer"). The fully developed high-voltage p-well (HPW) enables optimal connection of the deep pn junction 50 from the anode side.

[0050] It is preferred that the deep pn junction 50 is formed at least partially between a deep n-layer NBL as cathode 132 and a deep p-layer PBL directly adjoining the deep n-layer NBL, the absorption region (PW / HPW) directly adjoins the deep p-layer PBL and is formed substantially as a p-region (optionally comprising an intrinsic region), and a p + -Area P +The anode 134 is formed directly adjacent to the absorption region (PW / HPW). However, the forward directions and thus the arrangement of the anode and cathode terminals of the individual pn junctions can also be arranged differently. In particular, the individual pn junctions can each be formed inverted with respect to their respective forward directions, so that the deep pn junction 50 is formed at least partially between a deep p-layer PBL as the anode and a deep n-layer NBL as the cathode, which directly adjoins the deep p-layer PBL.

[0051] In the exemplary embodiment shown, the respective anodes 124 and 134 of the photon source 120 and the first single-photon detector 130 are combined. These can then be electrically contacted, for example, via a common second metallization MET2 on the surface O of the substrate 100. A common and continuous second metallization MET2 can also achieve shading to shield the entire installation space below. The associated cathodes 122 and 132 of the photon source 120 and the first single-photon detector 130 are each designed individually, for example, and can be electrically contacted via an associated first metallization MET1. In the exemplary embodiment shown, the cathode 132 of the first single-photon detector 130 is combined with the cathode 142 of the second single-photon detector 140 and can also be electrically contacted via the associated first metallization MET1.The associated anode 144 of the second single-photon detector 140 is also designed separately and can be electrically contacted via the associated first metallization MET1. The iQRNG 200 according to the invention can preferably be designed as a circular structure (corresponding to a spatial rotation of the depicted representation plane around an imaginary central axis in the vertical direction). However, other configurations of the depicted structure are also possible.

[0052] Fig. 2 shows an equivalent circuit diagram for the Fig. 1. The equivalent circuit diagram represents a general arrangement and is not limited to the arrangement shown in Fig. 1. The forward directions and thus the arrangement of the anode and cathode terminals of the individual pn junctions can also be arranged differently. In particular, the individual pn junctions can be inverted with respect to their respective forward directions. The vertical structure is supplied at the top via a first terminal C. avLED (Cathode connection, see cathode 122 in Fig. 1) and at the bottom via a second connection SX (anode connection, see anode 144 in Fig. 1), whereby the second connection SX can be guided over the substrate. The area between the photon source avLED and the first single-photon avalanche diode 1. SPAD is connected via a common anode connection (see common anode 124, 134 in Fig. 1). Furthermore, the area between the first single-photon avalanche diode 1. SPAD and the second single-photon avalanche diode 2. SPAD is connected via a common SPAD cathode terminal C SPAD (cf. common cathode 132, 142 in Fig. 1). Via these connections, the individual pn junctions can be supplied with different voltages, whereby if the second single-photon avalanche diode is omitted, the SPAD cathode connection C SPAD coincides with the second terminal SX (which in this embodiment must then be designed as a cathode terminal).

[0053] Fig. Figure 3 shows a unipolar power supply according to the state of the art for an iQRNG. In particular, the iQRNG can be a Fig. 2 corresponding structure. In this and the following figures, it is assumed that voltage converters are charge pumps. However, this is not intended to represent a fundamental restriction to charge pumps; in particular, all other corresponding voltage converters should be included in the examples shown instead of the charge pumps shown. In the voltage supply shown, a supply voltage U0 provided with respect to an electrical zero potential is amplified unipolarly via two voltage converters (charge pumps 2 and 4) with different amplification factors (F2 and F4) greater than or equal to 1 to the respectively required converter voltages (U2 and U4). The provided converter voltages (U2 and U4) can then be used to bias the individual pn junctions of the iQRNG with respect to the electrical zero potential.Due to the typically required high values ​​for the gain factors (F2 and F4), such a unipolar power supply has the technical disadvantages already described in detail above.

[0054] Fig. Figure 4 shows an exemplary first embodiment of a bipolar power supply according to the invention for an iQRNG. In contrast to the unipolar power supply according to Fig. 3, two further converter voltages (-U1, -U3) are provided via two additional voltage converters (charge pumps 1 and 3), whereby the additional voltage converters (charge pumps 1 and 3) invert the supply voltage U0 (they are therefore inverting charge pumps) and amplify it with gain factors (F1 and F3) greater than or equal to 1. The provided converter voltages (-U1, U2, -U3 and U4) can then be individually combined with one another to bias the individual pn junctions of the iQRNG by generating suitable differential voltages. In the exemplary embodiment shown, a first differential voltage between the first and fourth converter voltages (-U1 and U4), a second differential voltage between the first and second converter voltages (-U1 and U2) and a third differential voltage between the second and third converter voltages (U2 and -U3) are provided to bias the individual pn junctions of the iQRNG.This embodiment allows both a symmetrical and an asymmetrical voltage supply of the two SPAD pn junctions of the iQRNG with respect to the electrical zero potential.

[0055] Fig. Figure 5 shows an exemplary second embodiment of a bipolar power supply according to the invention for an iQRNG. The second embodiment essentially corresponds to that according to Fig. 4, whereby in this example a total of four voltage converters (charge pumps 1 to 4) are also present. However, the provided converter voltages (-U1, U2, -U3 and U4) do not have to be provided exclusively from the supply voltage U0; rather, the converter voltage of a first voltage converter can also be used as the input voltage for a downstream second voltage converter instead of the supply voltage U0 (cascaded arrangement). Such an amplifier concept also enables the provision of relatively high voltages with a modular design of the individual voltage converters. In the exemplary embodiment shown, the second converter voltage (U2) of the second voltage converter (charge pump 2) is inverted by the first voltage converter (charge pump 1) and amplified to the first converter voltage (-U1) with a first gain factor (F1) greater than or equal to 1.This embodiment also allows both a symmetrical and an asymmetrical voltage supply of the two SPAD pn junctions of the iQRNG with respect to the electrical zero potential.

[0056] Fig. Figure 6 shows an exemplary third embodiment of a bipolar power supply according to the invention for an iQRNG. The third embodiment represents a simplified version of the first embodiment according to Fig. 4. Only two voltage converters (charge pumps 1 and 2) are required. This design only allows for an asymmetric voltage supply to the two SPAD pn junctions of the iQRNG with respect to the electrical zero potential.

[0057] Fig. 7 shows an exemplary embodiment of a bipolar voltage supply according to the invention in a single-photon detector arrangement according to the invention. The first voltage converter (charge pump 1) is configured to invert a supply voltage U0 provided with respect to an electrical zero potential, to amplify it with a first gain factor F1 greater than or equal to 1, and to provide it as a first converter voltage -U1 with respect to the electrical zero potential. The pn junction configured as a SPAD is biased with a differential voltage with respect to the first converter voltage -U1. The first differential voltage results from the absolute value of the difference between the supply voltage U0 and the first converter voltage -U1.

[0058] Fig. Figure 8 shows an inventive bias voltage of the pn junctions with different differential voltages ΔV avLED , ΔV 1.SPAD , ΔV 2.SPADOn the left side, the above-mentioned exemplary embodiment is shown again according to Fig. 1 described equivalent circuit diagram according to Fig.2. However, the equivalent circuit shown is not limited to this specific embodiment of an iQRNG and is intended to encompass a variety of possible circuit arrangements in which high operating voltages for operating an integrated single-photon detector are to be generated from a small supply voltage without high power losses or a large area requirement. In the specific example, two different operating voltage levels are to be provided from a small supply voltage. However, the presented concept for the bipolar voltage supply of single-photon detectors is also applicable for more than two different operating voltage levels for operating one or a plurality of single-photon detectors to be supplied, with or without additional voltage levels for further circuit elements and components to be supplied.Accordingly, the specified voltage values ​​for the photon source avLED, the first single-photon detector 1. SPAD and the optional second single-photon detector 2. SPAD are to be understood as examples only.

[0059] Based on the values ​​given for the concrete embodiment mentioned above, two alternative power supply concepts are explained in more detail below.

[0060] In the symmetrical design, the 1st SPAD (with the highest voltage level) is supplied with voltages of equal magnitude but opposite polarity to the electrical zero potential via the anode terminal (-11 V) and the SPAD cathode terminal C SPAD (+11 V). A required operating voltage of the photon source avLED (with a lower higher voltage level) can then be achieved by simply providing a small negative voltage at the first terminal C avLED(approx. -4 V). Alternatively, the photon source avLED can also be supplied via a current control. The optional 2nd SPAD from the above-mentioned embodiment can be supplied by providing a voltage applied to the SPAD cathode terminal C. SPAD The voltage applied to the second terminal SX (-11 V) is symmetrically inverted to provide the required operating voltage (in this example, the same as the first SPAD). The second SPAD can also be switched independently of the first SPAD using the voltage applied to the second terminal SX.

[0061] In the asymmetrical version, the 1st SPAD (with the highest voltage level) is supplied with voltages of different values ​​and polarity via the anode terminal (-7 V) and the SPAD cathode terminal C SPAD(+15 V). In this case, the required operating voltage of the photon source avLED (with a lower higher voltage level) can be obtained by connecting the first terminal C avLED with the electrical zero potential (0 V / GND). Alternatively, the photon source avLED can also be supplied via current regulation. The optional 2nd SPAD from the aforementioned embodiment can then also be supplied with the required operating voltage by providing the voltage also applied to the anode connection anode at the second connection SX (-7 V). In this embodiment, too, the 2nd SPAD can be switched independently of the 1st SPAD via the voltage applied to the second connection SX. The negative bias of the substrate typically does not pose a problem for the area below the SPADs, as this is generally insulated from the environment and other electronic elements.

[0062] Relative to a preferred supply voltage with values ​​between 2 V and 3 V, a bipolar power supply according to the invention for single-photon detectors significantly reduces the requirements for providing higher voltages, particularly for operating SPADs integrated into a semiconductor substrate. While the supply voltages of conventional power supplies differ by a factor of approximately 8 to 10, these requirements can be roughly halved with a bipolar power supply according to the invention, whereby the higher supply voltages provided from the base voltage differ by only a factor of approximately 4 to 5 in the case shown. This enables the use of simpler multi-stage charge pumps to generate higher supply voltages, although a corresponding inversion of the provided supply voltage must be performed. List of reference symbols 22 first area (e.g. NBL) 32 second area (e.g. PBL) 50 first pn junction (e.g. upper pn junction of a double structure) 52 second pn junction (e.g. lower pn junction of a double structure) 60 third pn junction (e.g. light-emitting pn junction) 100 substrate 120 / avLED photon source (e.g. single photon source, SPS, especially Zener-avLED) 122 / C avLED Cathode (n + , photon source) 124 / Anode Anode (p + , photon source) 128 photons 130 / 1. SPAD first single-photon detector (e.g. single-photon avalanche diode, SPAD) 132 / C SPAD Cathode (n + , first single-photon detector) 134 / Anode Anode (p + , first single-photon detector) 140 / 2. SPAD second single-photon detector (e.g. single-photon avalanche diode, SPAD) 142 / C SPADCathode (n + , second single-photon detector) 144 / SX Anode (p + , second single-photon detector) 200 QRNG (integrated Quantum Random Number Generator) 210 first voltage converter (e.g. charge pump) 220 second voltage converter (e.g. charge pump) NBL deep n-layer (n-type buried layer) PBL deep p-layer (p-type buried layer) H(V)PW high-voltage p-type well H(V)NW high-voltage n-type well PW p-well PBODY p-doped region (p-type body) NEPI weakly n-doped or (approximately) intrinsic epitaxial region MET1, MET2 metallization CONT Contact VIA1 Via STI isolation area (“shallow trench isolation”) poly polysilicon layer P + p + -Area N + n + -Area O Surface (substrate, e.g. BCD substrate) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 4 214 174 A

[0012] Cited non-patent literature

[0000] M. Bloch, C. Lauterbach, and W. Weber. “High efficiency charge pump circuit for negative high voltage generation at 2 V supply voltage.” Proceedings of the 24th European Solid-State Circuits Conference. IEEE, 1998

[0012]

Claims

[1] Single photon detector arrangement, comprising: a substrate (100) made of a semiconductor material; a first pn junction (50) formed in the substrate (100) and configured as a first single-photon detector (130), wherein an operating voltage of the first single-photon detector (130) is above a supply voltage U0 provided with respect to an electrical zero potential; a first voltage converter (210) configured to invert the supply voltage U0, to amplify it with a first amplification factor F1 greater than or equal to 1 and to provide it as a first converter voltage -U1 with respect to the electrical zero potential, wherein the first pn junction (50) is connected to a first differential voltage (ΔV 1.SPAD ) is biased with respect to the first converter voltage -U1. [2] Single photon detector arrangement according to claim 1, wherein the first differential voltage (ΔV 1.SPAD) results from the difference between the supply voltage U0 and the first converter voltage -U1. [3] Single-photon detector arrangement according to claim 1, further comprising a second voltage converter (220) configured to amplify the provided supply voltage U0 with a second amplification factor F2 greater than 1 and to provide it as a second converter voltage U2 with respect to the electrical zero potential, wherein the first differential voltage (ΔV 1.SPAD ) results from the magnitude of the difference between the second converter voltage U2 and the first converter voltage -U1. [4] Single photon detector arrangement according to one of the preceding claims, wherein the first differential voltage (ΔV 1.SPAD ) is symmetrical or asymmetrical with respect to the electrical zero potential. [5] Single-photon detector arrangement according to one of the preceding claims, further comprising a second pn junction (52) formed in the substrate (100) and configured as a second single-photon detector (140), wherein a first region (22) located directly between the first pn junction (50) and the second pn junction (52) is electrically conductive. [6] Single-photon detector arrangement according to claim 5, wherein an operating voltage of the second single-photon detector (140) is above the supply voltage U0 and the second single-photon detector (140) is connected to a second differential voltage (ΔV 2.SPAD ) is biased with respect to a common electrical potential in the first region (22). [7] Single photon detector arrangement according to claim 5 or 6, wherein the second pn junction (52) is formed below the first pn junction (50). [8] Monolithically integrated quantum random number generator, iQRNG, comprising a single-photon detector arrangement according to one of the preceding claims, wherein a third pn junction (60) configured as a photon source (120) is formed above the first pn junction (50), wherein an intermediate region located directly between the first pn junction (50) and the third pn junction (60) is electrically conductive. [9] iQRNG according to claim 8, wherein the third pn junction (60) is connected to a third differential voltage (ΔV avLED ) is biased with respect to a common electrical potential in the intermediate region. [10] iQRNG according to claim 8 or 9, wherein the photon source (120) is a light-emitting avalanche Zener diode, Zener-avLED, operated at an operating point below or near the breakdown voltage.

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