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    • 专利摘要:
    The inventive photosensor for the detection of infrared radiation in the wavelength range of 1 to 1000 micrometers consists of a semiconductor substrate (55) with a highly doped interaction volume (3) for the incident radiation. At the edge of this heavily doped region is placed an extended gate electrode (4) made of a conductive material on an insulating layer. On the other side of the gate electrode (4) another highly doped semiconductor region is placed, which acts as a charge collector. By free carrier absorption in the interaction volume (3) incident photons impart their energy to mobile charge carriers. In the case of free electrons, the gate electrode (4) is biased slightly below the reset voltage of the interaction volume (3) so that the electrons carrying the added energy of the absorbed photons predominantly to the transition from the interaction volume across the gate electrode region the charge collector volume whose potential has been set sufficiently high so that the collected free electrons remain in this semiconductor region. The collected free charge carriers are detected electronically with known circuits for measuring electric current or charge packets. A plurality of such infrared photosensor devices may be arranged in one or two-dimensional arrangements to form line or image sensors.
    公开号:CH709726B1
    申请号:CH01428/15
    申请日:2014-03-31
    公开日:2018-05-15
    发明作者:Seitz Peter
    申请人:Hamamatsu Photonics Kk；
    IPC主号:
    专利说明:

    Description TECHNICAL FIELD The present invention relates to a method and apparatus for detecting infrared radiation in the wavelength range of 1 to 1000 micrometers, using a known semiconductor manufacturing process. More particularly, the invention relates to an infrared photosensor that can be fabricated using a silicon process, such as those widely used for silicon-based CMOS (complementary metal oxide semiconductor devices).
    Background Art The detection of electromagnetic radiation is one of the most important detection tasks in science, technology and consumer electronics. Silicon is the fundamental semiconductor of microelectronics and is well-suited for the fabrication of highly sensitive photosensors - from point detectors to multi-megapixel image sensors - covering a broad spectral range from soft X-ray to near-infrared. This corresponds to a sensitive wavelength range of about 1 nm to the cutoff wavelength of silicon of about 1100 nm. Due to the growing importance of infrared radiation for diagnostic and non-contact chemical fingerprinting purposes, there is a rapidly growing demand for photosensors in the infrared spectral range Wavelength over 1 micrometer are sensitive, where conventional silicon photosensors are no longer sensitive.
    A widely used method for detecting infrared radiation is the use of pyroelectric materials capable of spontaneously changing their electrical polarization as a function of temperature, for example as described by J. Fraden in "Handbook of Modern Sensors", 3rd Edition, Springer 2004. This polarization change can be detected as a current or voltage change using known electronic measurement circuits. Due to the difficulty of processing most pyroelectric materials, only a limited number of photosensing elements (pixels) are fabricated on a single detector device, typically between one and several hundred pixels (pixels).
    In a thermopile, a larger number of infrared-sensitive pixels with thermoelectric material systems prepared, as described for example by J. Fraden in "Handbook of Modern Sensors", 3rd edition, Springer 2004. They consist of a combination of two different types of semiconductor materials, a so-called thermocouple. Due to the Seebeck effect, such a thermocouple will produce a voltage as a function of a temperature differential across the device. A thermopile sensor is formed of several hundred to several thousand thermocouple pixels on the same device.
    Even a larger number of infrared pixels-up to several hundred thousand pixels on a device-can be made with microbolometer arrangements, as described, for example, in J. Fraden in Handbook of Modern Sensors, 3rd Edition, Springer 2004. Each Pixel consists of a heat-insulated heat absorber on a conductive material showing a large change in resistance as a function of temperature. Microbolometer sensors can be operated without cooling. However, because their working principle depends on device heating, the sensitivity of microbolometers is quite limited and it is impossible to get close to one-photon sensitivity.
    This limitation can be overcome with infrared detecting devices based on the photoelectric effect as described by B.E.A. Saleh and M.C. Teich, "Fundamentals of Photonics", 2nd Edition, John Wiley and Sons, 2007. In a first type of photoelectric devices, the external photoelectric effect in metals and semiconductors is exploited in vacuum. If an incident photon with sufficient energy is absorbed by an electron in the photoelectric material, this stimulated electron can overcome the attraction of the metal so that the electron can leave the material and enter the vacuum space. In this vacuum, the liberated electron can be supplied with additional energy, often by acceleration in a high-voltage electric field, so that each individual electron can be reliably detected.
    In order to simplify the production of an infrared sensor and to reduce the production costs, attempts are made to avoid the use of a vacuum. This can be achieved with the internal photoelectric effect exploited by semiconductor material systems. These materials show a bandgap structure in their energy diagram with a fully filled valence band and a completely empty conduction band at absolute temperature zero. If the energy of an incident electron is greater than the bandgap - the energy difference between the conduction band and the valence band - then the incident photon can be absorbed by the semiconductor material and generate a pair of mobile charges, an electron in the conduction band, and a hole in the valence band , In this way, the incident radiation modifies the electrical conduction properties in the semiconductor material, which can be detected with electrical circuitry. In photoconductive sensors, the change of an effective resistance is measured as a function of the intensity of the incident radiation. In photovoltaic sensors, the photo-generated charge pairs move in an electric field, creating an electrostatic potential change across the device as a function of the intensity of the incident radiation. The photosensors with the highest sensitivity based on the internal photo effect consist of depleted semiconductor regions using either reverse bias photodiodes, such as those used in CMOS image sensors, or MOS (Metal Oxide Semiconductor) structures, such as charge-coupled devices - Charge Coupled Device (CCD) image sensors or Pho-togate image sensors used generates. In these sensitive photosensors, the devices are biased at a certain reverse potential and then left electrically floating. The photogenerated carriers reduce the voltage across the device in proportion to the intensity of the incident radiation. This voltage change can be detected electrically with a room temperature readout equivalent to less than one electron RMS, as described, for example, by Ch. Lotto and P. Seitz in US Pat. No. 8,119,972 B2 "A solid state image sensing device having a low pass filter for limiting signal Frequencies passing through the output node of an inverting amplifier ».
    All these sensitive radiation detectors using the external or internal photoelectric effect have in common that they can not detect incident photons whose energy is too low to either overcome the effective work function in the case of the external photo effect or moving charge pairs to generate the band gap in the case of the internal photo effect. Consequently, these sensitive photodetectors have a so-called cutoff wavelength λ0 above which they are no longer sensitive. The cutoff wavelength λο is inversely proportional to the minimum energy Emin required to generate mobile carriers due to the photoeffect, λο = hxc / Emin, Planck constant h, and the vacuum light velocity c. This implies that the photoelectric effect is unsuitable for the detection of electromagnetic radiation in the ultra-long wavelength infrared spectral range.
    This limitation of absent infrared sensitivity can be overcome with a semiconductor device according to the HIP (Homojunction Internal Photoemission) principle as described by A.G.U. Perera et al. in Homojunction internal photoemission far-infrared detectors; Photoresponse Performance analysis, J. Applied Physics Volume 77, pages 915-923, 1995. A HIP detector consists of a vertical array of a heavily doped semiconductor region on the surface of the device, followed by a lightly doped (or intrinsic) region. In the highly doped region, a large number of free charge carriers are present and these can interact with the incoming electromagnetic radiation by free carrier absorption (FCA, Free Carrier Absorption). A free carrier can absorb the energy of an incident photon, resulting in a photostimulated carrier. These photostimulated charge carriers lose their energy quite rapidly through various inelastic and elastic scattering processes over a characteristic distance L, the so-called scattering length. In a HIP device, a potential barrier is formed between the heavily doped and the lightly doped semiconductor region, parallel to the surface of the HIP device. If a photostimulated carrier is produced which is less than the scattering length L from the potential barrier, and if the energy of the photostimulated carrier is sufficiently high, then the carrier can overcome the potential barrier, it is transported vertically through the lightly doped region into the semiconductor, where it can be detected with any of the electronic circuits known from the literature. Such HIP photosensors, for example made of silicon or germanium, have been used to detect infrared radiation having a wavelength greater than 200 microns.
    However, the HIP infrared photosensors suffer from two major disadvantages: (1) the potential barrier which must overcome stimulated charges is permanently determined by the materials used to make the HIP photosensor; it can be determined by the work function of a particular metal or it is determined by the doping concentration of the lightly doped semiconductor volume. Consequently, the cutoff wavelength can not be electrically matched to such HIP photosensors. (2) The incident infrared photons produce stimulated carriers that must diffuse vertically through the heavily doped conversion region before they reach the lightly doped semiconductor volume where they can be detected. Since stimulated carriers in highly doped semiconductors have a very short lifetime before thermalization, their diffusion length in the heavily doped semiconductor is limited to short distances on the order of nanometers. Consequently, the effective quantum efficiency of such a HIP photosensor is very small compared to photosensors which exploit the photoelectric effect in depleted semiconductor regions.
    Citation list [0011] PTL 1: US Patent No. 8,119,972 B2 Non-Patent Literature NPL 1: "Handbook of Modern Sensors", 3rd Edition, J. Fraden, Springer 2004 NPL 2: "Fundamentals of Photonics », 2nd edition, BEA Saleh and M.C. Teich, John Wiiey and Sons, 2007 NPL 3: "Homojunction internal photoemission far-infrared detectors: photoresponse performance analysis", J. Applied Physics, Volume 77, pages 915-924, 1995
    Summary of the Invention Technical Problem In order to overcome the limitations of these known methods and devices, the present invention describes a semiconductor photosensor device for infrared radiation in the wavelength range of 1 to 1000 micrometers, which utilizes free carrier absorption in a heavily doped semiconductor volume. The cutoff wavelength of the infrared photosensor according to the present invention can be arbitrarily adjusted by selecting a voltage on a gate electrode. The transport of stimulated carriers is sideways, resulting in improved quantum efficiency compared to conventional HIP infrared photosensors.
    The present invention overcomes the limitations of infrared photosensors described above by providing a photosensor device for sensitive detection of infrared radiation in the wavelength range of 1 to 1000 microns. It consists of a semiconductor substrate with a highly doped interaction volume for the incident infrared radiation. At the edge of this heavily doped region is placed an extended gate electrode made of a conductive material on an insulating layer. On the other side of the gate electrode another highly doped semiconductor region is placed, which acts as a charge collector. By free carrier absorption in the interaction volume, incident infrared photons transmit their energy to mobile charge carriers. If the mobile carriers are free electrons, the gate electrode is biased slightly below the backscatter voltage of the interaction volume, so that the electrons carrying the added energy of the absorbed photons predominantly make the transition from the interaction volume over the gate electrode region to the charge collector volume, whose potential has been set sufficiently high so that the collected free electrons remain in this semiconductor region. The collected free charge carriers are detected electronically with known circuits for the measurement of electric current or charge packets. A variety of such photosensor devices may be arranged in 1- or 2-dimensional arrays to form line or area sensors for infrared radiation. Solution to the Problem An object of the present invention relates to a photosensor for detecting infrared radiation in the wavelength range of 1 to 1000 microns. The photosensor includes a main portion of a semiconductor substrate; a highly doped interaction volume for the incoming radiation in the semiconductor substrate; an adjacent gate electrode including a conductive material on an insulating layer, the adjacent gate electrode being an extended structure adjacent to the interaction volume; and an adjacent heavily doped collector region acting as a charge collector, the collector region consisting essentially of a heavily doped semiconductor region and an expanded structure adjacent to the gate electrode. In the photosensor, the interaction volume is biased to a first voltage VB, the collector region is electrically biased to a second voltage Vs which is higher than the first voltage VB if photostimulated electrons are to be collected and which is smaller than the first voltage, if photoreceptive holes are to be collected, the incident photons transmit their energy by free carrier absorption to mobile charge carriers in the interaction volume, producing photostimulated electrons if the free carriers are electrons or photostimulated holes are produced if the free carriers are holes, and the Gate electrode is biased to a third voltage VG, so that a potential barrier is generated for the photostimulated charge carriers in the interaction volume, so that the energy mediated by the incident photons is sufficient to allow the photostimulated L can overcome the potential barrier, and the photostimulated charge carriers can be collected in the collector region for subsequent electronic detection.
    In the above photosensor, a portion of the interaction volume may adjoin at least one side of the gate electrode and the collector region. The collector region may be surrounded by the gate electrode, which is surrounded by a region in the interaction volume. The collector region may have a rectangular structure, a circular structure or a polygon structure.
    The above photosensor may further comprise an amplifier or a circuit connected to the collector region, wherein the amplifier or the circuit detects the second voltage Vs and produces an output voltage Vout. The amplifier or circuit may include a reset switch that resets the collector region to the second voltage Vs. The reset switch can reset the collector region periodically. The amplifier or circuit may include a sense node and a source follower transistor, wherein the sense node is reset to the second voltage Vs by the reset switch and connected to a gate of the source follower transistor.
    Advantageous Effects of Invention This invention can provide a photosensor for highly sensitive detection of infrared radiation over a wide, adjustable spectral range.
    Brief Description of the Drawings The invention will be better understood and other objects than the above will become apparent when the following detailed description is considered. This description makes reference to the accompanying drawings, in which:
    Fig. 1 shows a cross section of an infrared photosensor according to the present invention. In the lower part of the figure, the lateral distribution of surface potential ε> s (the electrostatic potential at the surface of the semiconductor) is shown for the case that the free carriers in the interaction region are electrons, and the potential νλ of the incident infrared photons is larger as the gate potential difference VB-VG.
    Fig. 2 shows a cross section of the infrared photosensor according to the present invention. In the lower part of the figure, the lateral distribution of the surface potential εs (the electrostatic potential at the surface of the semiconductor) is shown for the case where the free carriers in the interaction region are electrons, and where the potential νλ of the incident infrared photons is smaller than the gate potential difference VB-VG.
    Fig. 3 shows the plan view of a preferred embodiment of the infrared photosensor according to the present invention. It consists of a linear arrangement of a highly doped interaction volume bounded on both sides by collector structures.
    Fig. 4 is a plan view of another preferred embodiment of the infrared photosensor according to the present invention. It consists of a two-dimensional arrangement of rectangular collector structures in a highly doped interaction volume.
    Fig. 5 shows the top view of another preferred embodiment of the infrared photosensor according to the present invention. It consists of a two-dimensional arrangement of circular collector structures in a highly doped interaction volume.
    Fig. 6 shows an exemplary circuit for continuously reading the current from the collector structure. It consists of a transimpedance amplifier that converts an input current into a signal voltage.
    Fig. 7 shows an exemplary circuit for the readout of charge carriers in the collector structure. It consists of a charge integrator with reset switch.
    FIG. 8 shows another exemplary circuit for reading charge carriers in the collector structure. It consists of a source follower with a reset switch connected to the sense node.
    Fig. 9 shows an exemplary circuit for the readout of charge carriers in the collector structure, which offers an increased dynamic range. It consists of a source follower with a reset switch connected to the sense node and a current source also connected to the sense node through which a programmable compensation current can flow.
    Fig. 10 shows a preferred embodiment of the circuit in Fig. 9 for the readout of charge carriers in the collector structure, which offers an increased dynamic range. It consists of a source follower with a reset switch connected to the sense node and a single transistor operating in a saturated mode as a current source also connected to the sense node. This transistor acts as a programmable current source through which the compensation current Ic can flow.
    DESCRIPTION OF EMBODIMENTS The present invention provides a photosensor for the highly sensitive detection of infrared radiation in the broad spectral range of 1 to 1000 microns.
    The present invention further provides an infrared photosensor that can be fabricated with an industry standard semiconductor process, such as the widely available silicon-based CMOS processes.
    The present invention also provides an infrared photosensor whose cutoff wavelength can be selected rapidly and selectably with a voltage.
    The present invention further provides an infrared photosensor having such a small footprint that one and two-dimensional infrared image sensors can be produced using an industry standard semiconductor process, resulting in an infrared sensor having at least 1 megapixel per square centimeter.
    The present invention further provides an infrared photosensor capable of discriminating between photocurrents produced by incident infrared photons and currents generated either by thermal excitation (so-called dark currents) or photocurrents generated by incident visible photons, this discrimination by suitable electrical operation of the device is made without the need for additional optical filters.
    For these reasons, the present invention is achieved with a semiconductor device shown in Fig. 1. It consists of a lightly doped or intrinsic semiconductor substrate 55 (main area 1), which is biased to a substrate voltage Vsub through the heavily doped contact area 2. In the substrate 55, an interaction volume 3 is formed as a highly doped semiconductor volume of the opposite type as the main region 1 of the substrate 55. The interaction volume 3 can be reset to a bias potential VB by a bias switch 8. Adjacent to the interaction volume 3 is placed an extended gate electrode 4 consisting of a conductive layer on which an insulating layer is formed. The gate electrode 4 is connected to the gate voltage VG. On the other side of the gate electrode 4, a collector region 5 is formed as a heavily doped semiconductor region of the same type as the interaction volume 3. The collector region 5 is connected to an amplifier 6 (amplifier circuit) which detects the signal potential Vs and produces the output voltage Vout. Incident photons 7 interact with the free charge carriers in the interaction volume 3, transfer their energy to free carriers and stimulate them into a higher energy state.
    Without loss of generality, it is assumed below that the free charge carriers are electrons, in which case the interaction volume 3 and the collector volume 5 are n + type and the main region of the substrate 55 is either p-type or intrinsic. The interaction volume 3 is biased by switch 8 to the intermediate bias voltage VB. The substrate voltage VSUb is adjusted so that no net current flows between the interaction volume 3 and the main region 1 of the substrate 55. The gate voltage VG is selected smaller than the bias voltage VB, so that an electrostatic barrier having a potential difference of (VB-VG) for the free electrons in the interaction volume 3 is generated. Due to thermal excitation of the free electrons in the interaction volume 3, some of these thermally excited (stimulated) electrons have sufficient energy to overcome the potential barrier, so that they can diffuse through gate region 4 and be collected in the collector region 5.
    [The collector region 5 is biased by a high positive voltage Vs to prevent the collected electrons from returning to the interaction region. Free electrons which overcome the potential barrier due to thermal excitation represent a temperature-dependent dark current of the photosensor according to the present invention.
    Incident photons interact in the interaction region 3 with the free electrons due to the free carrier absorption (FCR) effect, as for example by PY Yu and M. Cardona in "Fundamentals of Semiconductors", 4. Edition, Springer, 2010 described. The absorption coefficient due to the FCA is proportional to the doping concentration of the interaction region and to the square of the wavelength of the incident photons. In doped semiconductors, the absorption of electromagnetic radiation from FCA is dominated above the cutoff wavelength. In heavily doped silicon, FCA is the dominant absorption mechanism in the wavelength range of 1.1 microns to at least 1000 microns.
    When an incident photon of wavelength λ interacts with a free electron through FCA, the photon mediates its energy E = hxc / λ to the free electron. This corresponds to an excited (stimulated) energy state of the electron with a potential difference of νλ = E / q = h χ ο / (λ χ q) in the potential diagram of FIG. 1, where q denotes the unit charge q equal to 1.602 χ 1CT19 As.
    If this potential difference νλ is at least as large as the potential barrier (VB-VG) generated by the gate electrode, then the stimulated electron can overcome the potential barrier, it can diffuse through the gate region, and then into collected in the collector region 5, where it contributes to the signal charge. In this operating mode, the photocurrent is independent of the gate voltage VG as long as νλ is greater than the potential barrier (VB-VG). This is the preferred mode of operation if the device is cooled to such low temperatures that the dark current density is comparable or less than the photocurrent.
    The device can also be operated with little or no cooling, and its operating mode for this case is shown in Figure 2: the potential νλ. the photostimulated electron is smaller than the potential barrier (VB-VG). In this case, free electrons contributing to the dark current as well as to the photocurrent must be thermally excited to overcome the potential barrier represented by (VB-VG). For this reason, the total photocurrent IP is given as the sum of three components, dark current Id, plus photocurrent Iv generated by incident photons having energy below the semiconductor cutoff wavelength, plus the signal photocurrent I s produced by incident infrared photons: lp = lb + lv + ls. Because both currents ld and ls depend on the thermal excitation for the electrons to overcome the potential barriers, they are proportional to each other, that is, ls = Α (λ) χP | r χ ld, where the intensity P | R of the incident Infrared radiation and the proportionality constant Α (λ) of the wavelength λ of the incident infrared photons depend. While both currents ld and ls depend exponentially on the gate voltage difference (VB-VG), the photocurrent lv does not depend on it. For this reason, it is possible to determine lv as the contribution to the total device current, which is independent of the gate voltage, by measuring the total current for two or more different gate voltages and by calculating the constant part in the current. Therefore, the proportion of incident radiation whose wavelength is below the cutoff wavelength of the semiconductor can be measured without the need for additional optical filters.
    In any case, the raw output signal of the amplifier 6 consists of the sum of signal currents plus temperature-dependent dark currents. The net signal is obtained by determining the difference between the raw output signal and the dark current contribution. A preferred way to determine the dark current is to provide an additional photosensor according to the present invention as a reference component, the surface of which is completely covered with a material that is impermeable to the incident electromagnetic radiation. For this reason, the total current measured by this component is only due to the dark current, and if the temperature of the reference component is the same as the uncovered measurement component, then the dark current in the measurement component is also known.
    The de-excitation (relaxation) time of free charge carriers in highly doped semiconductors is very small; in silicon, it is of the order of 1ps. Consequently, there is a scattering length L over which an excited carrier loses its photostimulation energy; in silicon, this scattering length in highly doped silicon is on the order of 1 nm. Only free electrons that act with incident photon interactions that are located at a distance less than L away from the gate electrode have a chance to overcome the potential barrier. This is shown in FIGS. 1 and 2. It is therefore desirable to make the width of the interaction region as small as possible in order to obtain a large quantum efficiency of the resulting photosensor. Preferred embodiments of the infrared photosensor according to the present invention are shown in Figs. 3, 4 and 5: In Fig. 3, there is shown a stripe-like arrangement of the photosensor 50a having a long and thin interaction region 10 on either side of the gate electrode 11 and collector region 12 is limited. As shown in the figure, the inner part of the interaction region 10, which is farther than the distance L from the electrodes 11, does not contribute to the photosignal, and is substantially inactive in our photosensor.
    In Fig. 4, the photosensor 50b is shown with a two-dimensional array of small rectangular collector regions 22 which are surrounded by gate electrodes 21 in a larger interaction region 20. The signal from all the collector regions 22 is added together so that photosensors of arbitrary area can be realized without losing sensitivity.
    As shown in Fig. 5, the photosensor 50c may be realized with small collector regions 32 surrounded by gate electrodes 31, alternatively circular structures. This embodiment provides constant electric field conditions around the perimeter of the gate electrodes, thereby preventing any high field areas at corners.
    Free charge carriers collected in the collector regions are detected by known electronic circuits. Preferred embodiments of an amplifier circuit 6, shown symbolically in Figs. 1 and 2, are shown in Figs. 6 to 10: Fig. 6 shows a transimpedance amplifier circuit 6a used for the continuous measurement of a current I generated by the collector region connected to the input of this circuit is provided. This transimpedance amplifier circuit 6a holds the collector region at a potential Vs and at its output provides a voltage Vout = R χ I which is proportional to the input current I, where R is the resistance of the feedback loop.
    Fig. 7 shows a charge integrator circuit 6b capable of integrating the charge Q accumulated in the collector region. Integration takes place on the capacitor C in the feedback loop of the operational amplifier, resulting in an output voltage Vout = Q / C , Once an integration period is completed, the output voltage is read from an external circuit and the charge integrator circuit is reset by closing the reset switch in the feedback loop with the reset signal. In this way, the collector region is periodically reset to the potential Vs.
    Fig. 8 shows a source follower circuit 6c capable of measuring the charge Q accumulated in the collector region with high sensitivity. Charge integration takes place in the capacitor C connected to the sense node. Before charge integration starts, the sense node is reset to the potential Vs by closing the reset switch connected to the sense node with the VreSer signal. Integration of the charge Q on the capacitor C results in a voltage signal given by V = Q / C on the sense node electrically connected to the gate of the source follower transistor. The source of the source follower transistor is connected through a resistor R to the ground potential and the drain is connected to the power supply voltage VDD. At the output of the source follower circuit, a voltage Vout is produced which is substantially the same as the gate voltage minus an offset voltage VT, that is Vout = Q / C-VT.
    Fig. 9 shows the schematic diagram of an electronic circuit 6d offering an increased dynamic range of the current measurement based on the source follower circuit shown in Fig. 8. Such an increased dynamic range is desirable in cases where the dark current is a significant portion of that of the
    权利要求:
    Claims (9)
    [1]
    Photosensor device according to the present invention measured total current. This increased dynamic range can be achieved with a programmable power source in series with photosensor device. In this way, a compensation current Ic can be subtracted from the total current measured with the device. If this total current is close to the dark current, the influence of the dark current on the net signal current is significantly reduced and thus the dynamic range of the device is correspondingly increased. Fig. 10 shows a preferred embodiment of the enlarged dynamic range circuit 6e shown schematically in Fig. 9. The programmable current source is implemented with a single transistor operated in saturation mode, that is, the current through this transistor is substantially independent of the source-drain voltage, and the compensation current Ic can be programmed with the gate voltage. The infrared photosensor according to this invention can be implemented with commercially available semiconductor processes, such as a photosensitive structure with dimensions in the micrometer range, similar in size to photosensitive areas in known silicon-based photosensors for the visible and near-infrared spectral range. Preferred embodiments of the charge detecting circuits for infrared sensors according to this invention are also very similar to the photo charge detecting circuits used in known silicon based photosensors for the visual and near-infrared spectral range. Thus, a complete infrared sensor according to this invention has a comparable footprint as known pixels of silicon-based photosensors for the visible and near-infrared spectral regions. For this reason, it is possible to manufacture a plurality of infrared photosensors according to this invention on the same piece of a semiconductor. In particular, one-dimensional infrared line sensors and two-dimensional infrared image sensors can be fabricated with pixel densities comparable to those obtained for silicon-based lines and image photosensors for the visible and near-infrared spectral regions. As described above, the photosensor according to this invention includes a main region of a semiconductor substrate, a highly doped interaction volume for the incident radiation in the semiconductor substrate, an adjacent gate electrode containing a conductive material on an insulating layer, the adjacent gate electrode having a is an extensive structure adjacent to the interaction volume, and an adjacent highly doped collector region acting as a charge collector, the collector region consisting essentially of a heavily doped semiconductor region and being an expanded structure adjacent to the gate electrode. The interaction volume is electrically biased to a first voltage VB, the collector region is electrically biased to a second voltage Vs higher than the first voltage VB if photostimulated electrons are to be collected, and lower than the first voltage VB if photostimulated Holes are to be collected. The incident photons transmit their energy by free carrier absorption to mobile carriers in the interaction volume, producing photostimulated electrons, in the case that the free carriers are electrons, or photostimulated holes are produced, in the case that the free carriers are holes. The gate electrode is biased to a third voltage VG such that a potential barrier for the photostimulated carriers in the interaction volume is generated such that the energy mediated by the incident photons is sufficient for the photostimulated carriers to overcome the potential barrier and the photostimulated carriers in the interaction Collector area can be collected for subsequent electronic detection. In a preferred embodiment, the infrared photosensor according to the present invention can be manufactured with a silicon as a base material, using the manufacturing methods used for CMOS devices. Reference number [0048] 1 ... substrate; 2 ... contact region; 3 ... interaction volume; 4 ... gate electrode; 5 ... collector region; 6 ... amplifier; 7 ... incident photon; 8 ... switch; 50, 50a, 50b, 50c ... Photosensor; 55 ... semiconductor substrate. claims
    A photosensor for detecting infrared radiation in the wavelength range of 1 to 1000 microns, wherein the infrared photosensor can be manufactured with an industry standard semiconductor process, resulting in an infrared sensor of at least 1 megapixel per square centimeter and whose cutoff wavelength can be selected quickly and selectively with a voltage, comprising: a main portion (1) of a semiconductor substrate (55); a highly doped interaction volume (3) for the incident radiation into the semiconductor substrate (55); an adjacent gate electrode (4) containing a conductive material on an insulating layer, the conductive material being an expanded structure adjacent to the interaction volume (3); and a highly doped collector region (5) adjacent to the gate electrode and acting as a charge collector, the collector region (5) consisting essentially of a heavily doped semiconductor region and an expanded structure adjacent to the gate electrode (4), a bias switch (8) connected to the interaction volume (3) and arranged to bias the interaction volume (3) with a first electrical voltage VB, an amplifier (6) or a circuit connected to the collector region (5) and arranged to electrically bias the collector region (5) to a second voltage Vs higher than the first voltage VB if photostimulated electrons are to be collected, and which is smaller than the first voltage VB if photostimulated holes are to be collected; Electrode (4) is biased to a third voltage VG, so that a potential barrier for the photostimulated charge carriers in d an interaction region can be generated such that the energy mediated by the incident photons is sufficient for the photostimulated carriers to overcome the potential barrier and for the photostimulated carriers in the collector region to be collected for subsequent electronic detection,
    [2]
    The photosensor according to claim 1, wherein a region of the interaction volume (3) is adjacent to the gate electrode (4) on at least one side so that the interaction volume (3) and the collector region (5) are separated from each other by the gate electrode (4).
    [3]
    A photosensor according to claim 1, wherein the collector region (5) is surrounded by the gate electrode (4) surrounded by a region of the interaction volume (3).
    [4]
    4. The photosensor according to claim 3, wherein the collector region (5) has a rectangular structure, a circular structure or a polygon structure.
    [5]
    A photosensor according to any one of claims 1 to 4, wherein the amplifier (6) or the circuit detects the second voltage Vs and produces an output voltage Vout.
    [6]
    A photosensor according to claim 5, wherein the amplifier (6) or the circuit includes a reset switch which resets the collector region (5) to the second voltage Vs.
    [7]
    A photosensor according to claim 6, wherein the reset switch is arranged to periodically reset the collector region (5).
    [8]
    A photosensor according to any one of claims 5 to 7, wherein the amplifier (6) or the circuit includes a sense node and a source follower transistor, wherein the sense node can be reset to the second voltage Vs from the reset switch and connected to a gate of the source. Subsequent transistor is connected.
    [9]
    A photosensor according to any one of claims 5 to 7, wherein the sense node is connected to a programmable current source capable of subtracting an offset current from the signal current accumulated in the collector region, this programmable current source providing an increased dynamic range of the photosensor, since a substantial portion of the dark current can be subtracted from the signal current prior to its electronic detection.
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    JP6178429B2|2017-08-09|
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    法律状态:
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    PCT/JP2014/060042|WO2014163205A1|2013-04-04|2014-03-31|Semiconductor photosensor for infrared radiation|
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