JP2011216706A - Infrared sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared sensor obtaining a larger output voltage while suppressing an increase in the number of connection stages of a photodiode.SOLUTION: The infrared sensor 1 extracts infrared energy by converting it into an electric signal, and includes a light receiving unit 2 converting the infrared energy to the electric signal, and a magnet 7, a magnetic body 6, and a lead frame 3 generating a magnetic field acting to exert Lorentz force to charges excited by receiving the infrared energy by the light receiving unit 2. The Lorentz force is exerted in a direction orthogonal to a charge moving direction by the magnet 7, the magnetic body 6, and the lead frame 3.

Description

  The present invention relates to an infrared sensor that detects infrared rays using an infrared detection element such as a photodiode, and more particularly to an infrared sensor that can obtain a high output voltage from the infrared detection element.

  Currently, there are infrared sensors that detect infrared rays using infrared detection elements. For such an infrared sensor, a semiconductor photodiode is known as a quantum infrared detection element. A quantum infrared detection element is an element configured to detect an electrical phenomenon caused by light energy, and is known to have high detection sensitivity and excellent response speed. Moreover, the semiconductor photodiode has sensitivity to infrared rays having a wavelength equal to or less than the wavelength corresponding to the band gap energy of the semiconductor.

  The semiconductor photodiode has a diode structure having a PN junction or a PIN junction, and electron and hole pairs are generated in a depletion layer existing in the PN junction or the PIN junction by infrared photons. The generated electron and hole pairs are distributed and accumulated according to the inclination of the valence band and the conduction band. As a result, the P-type semiconductor is charged on the positive side and the N-type semiconductor is charged on the negative side. An electromotive voltage is generated between the semiconductor and the semiconductor.

  Infrared rays having a wavelength region close to visible light have a large amount of energy, and a large output voltage can be obtained even with a single detection element. On the other hand, in recent years, there has been an increasing demand for infrared sensors capable of detecting longer wavelength infrared rays. Examples of such infrared sensors that are in demand include sensors that determine the approach of a human body (hereinafter referred to as human sensors). The human sensor is required to detect infrared rays centered around a wavelength of 10 μm emitted by the human body.

  Since the infrared energy in the wavelength region required for the human sensor is very weak, a single photodiode cannot obtain a sufficient output voltage. In such a case, it is conceivable to connect a plurality of photodiodes in series and obtain an output voltage that is multiple times that number. By connecting a plurality of photodiodes, a large voltage can be obtained as a whole even if the electromotive voltage of one photodiode is small.

  By the way, a PEM (Photo electromagnetic) sensor is known as an infrared detecting element having a structure other than a PN junction or a PIN junction. The PEM sensor is described in Non-Patent Document 1, for example. As shown in FIG. 10, the PEM sensor includes the infrared light receiving unit 2, the minus side electrode 40, the plus side electrode 41, and a magnetic field generation unit (not shown). In FIG. 10, the reference numeral 25 denotes electrons and the reference numeral 26 denotes holes.

When the PEM sensor receives infrared rays, electrons 25 and holes 26 are excited inside the element. At this time, the closer to the surface of the light receiving surface, the larger the amount of received infrared light, so that more electrons 25 and holes 26 are excited. Therefore, the concentration of electrons 25 and holes 26 in the infrared sensor is highest on the light receiving surface as shown in FIG. 11, and the concentration decreases as the depth increases, causing concentration gradients in electrons 25 and holes 26. The electrons 25 and holes 26 excited by receiving infrared rays try to diffuse in the depth direction (z direction in FIG. 11) due to this concentration gradient, but the magnetic flux in the y direction generated by the magnetic field generating means. Is applied, Lorentz force acts on the electron 25 in the -x direction and the hole 26 in the opposite direction to the + x direction. As a result, the electrons 25 are separated to the − side electrode 40 side and the holes 26 are separated to the + side electrode 41 side, and an electromotive voltage is generated between the electrodes 40 and 41.
The photodiode takes out excited electrons and holes to the outside by using the slope of the valence band and the conduction band. On the other hand, the PEM sensor takes out electrons and holes using the Lorentz force by a magnetic field.

International Publication No. 2005-27228 Pamphlet

High-Operating-Temperature Infrared Photodetectors, p. 180

As described above, when an attempt is made to extract a large electromotive voltage by increasing the number of connection stages of photodiodes having PN junctions or PIN junctions, naturally, the number of photodiodes provided in the infrared sensor and the wiring connecting the diodes The number of increases. In such a structure, since all photodiodes are connected in series, for example, when foreign matter adheres in the manufacturing process, even if a part of the wiring is disconnected or the photodiode is not properly formed, an electromotive voltage is generated. May not be able to be taken out. That is, increasing the number of connection stages of photodiodes has the advantage that a large voltage can be easily extracted, but has the disadvantage of reducing the reliability of the infrared sensor.
The present invention has been made in view of such a point, and an object thereof is to provide an infrared sensor capable of obtaining a larger output voltage while suppressing an increase in the number of photodiodes connected.

In order to solve the above-described problems, an infrared sensor of the present invention is an infrared sensor that converts infrared energy into an electrical signal and extracts it, and a light receiving unit that converts infrared energy into the electrical signal (for example, the light receiving shown in FIG. 1). Part 2) and magnetic field generating means for generating a magnetic field that acts to apply a Lorentz force to the charges excited by receiving the infrared energy by the light receiving part (for example, the magnet 7 and the magnetic material shown in FIG. 1) 6 and a lead frame 3), wherein the magnetic field generating means generates a magnetic field that applies a Lorentz force in a direction orthogonal to a direction in which the electric charge moves.
The infrared sensor according to the present invention further includes a converging unit (for example, the lead frame 3 shown in FIG. 1) for converging the magnetic field generated by the magnetic field generating unit on the light receiving surface of the infrared light receiving unit. It is desirable to provide.

According to the present invention, Lorentz force is applied in a direction orthogonal to the direction of charge movement, so that the electrical resistance in the sensor is increased and the electromotive voltage of the output signal given by the product of the resistance value and the photocurrent is increased. Can do. For this reason, this invention can provide the infrared sensor which can obtain a bigger output voltage.
Further, according to the present invention, in the above-described invention, the magnetic field can be converged on the light receiving surface of the infrared light receiving unit, so that the electrical resistance in the sensor can be further increased and a larger output voltage can be obtained. .

It is a figure for demonstrating the structure of the infrared sensor of Embodiment 1. FIG. It is a figure for demonstrating the infrared rays light-receiving part 2 shown in FIG. It is a figure for demonstrating an infrared sensor. FIG. 2 shows a state of magnetic flux generated by the magnet shown in FIG. It is a figure for demonstrating the mode inside the infrared sensor which received the infrared energy of one Embodiment of this invention. It is another figure for demonstrating the mode inside the infrared sensor which received the infrared energy of one Embodiment of this invention. It is another figure for demonstrating the mode inside the infrared sensor which received the infrared energy of one Embodiment of this invention. It is a figure for demonstrating the infrared sensor of Embodiment 2 of this invention. It is a figure for demonstrating the state of the magnetic flux of the infrared rays light reception part vicinity of Embodiment 2. FIG. It is a figure for demonstrating a well-known PEM sensor. It is a figure for demonstrating the density distribution of the electron and the hole in the PEM sensor shown in FIG.

Hereinafter, Embodiment 1 and Embodiment 2 of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIGS. 1A and 1B are diagrams for explaining the configuration of the infrared sensor of the first embodiment. 1A is a top view of the infrared sensor, and FIG. 1B is a cross-sectional view taken along a broken line AA ′ shown in FIG. As shown in FIG. 1, the infrared sensor 1 according to the first embodiment includes an infrared light receiving unit 2, a magnetic lead frame 3, a wire 4 for taking out an electromotive voltage, and a resin 5 that packages the light receiving unit. Become. Further, a magnet 7 as a magnetic field generating means and a magnetic body 6 for connecting the lead frame 3 and the magnet 7 are provided. The notations S and N in the figure represent the polarity of the magnet. The lead frame 3 must be arranged so that one side thereof coincides with the N pole side of the magnet and the other side thereof coincides with the S pole side of the magnet.

  FIG. 2 is a diagram for explaining the infrared light receiving unit 2 shown in FIG. As shown in FIG. 2, the infrared light receiver 2 includes a quantum PIN photodiode 30 formed on a semi-insulating gallium arsenide (GaAs) substrate 31. The member indicated by 34 in the figure is a wiring. The infrared light receiver 2 shown in FIG. 2 is packaged as shown in FIG. 3 to constitute an infrared sensor. Infrared rays are incident on the infrared sensor from the GaAs substrate 31 side as indicated by arrows in the figure.

The magnet 7 is preferably a rare earth magnet such as a samarium-cobalt (SmCo) magnet or a neodymium magnet. Rare earth magnets are known as capable of generating a stronger magnetic field.
4A and 4B show the state of the magnetic flux 10 generated by the magnet 7 shown in FIG. 1, where FIG. 4A is a top view and FIG. 4B is a cross-section of FIG. FIG. The magnetic flux 10 generated by the magnet 7 is converged in the vicinity of the infrared light receiving unit 2 by the magnetic body 6 and the lead frame 3 of the magnetic body, and a high magnetic flux density can be obtained in the vicinity of the infrared light receiving unit 2.

Next, the inside of the infrared sensor that receives infrared energy will be described with reference to FIGS. FIG. 5 shows a state where there is no magnetic field inside the infrared sensor. FIG. 6 shows a state where a magnetic field is present inside the infrared rays.
5 and 6 are cross-sectional perspective views of the infrared light receiving unit 2. The infrared light receiving unit 2 is configured by sequentially providing an N layer 22, a light absorption layer 21, and a P layer 20 on a GaAs substrate 31, a negative electrode 24 on the N layer 22, and a positive electrode 23 on the P layer 20. Has been. Reference numeral 25 denotes electrons, reference numeral 26 denotes holes, and arrows x, y, and z are coordinate axes that indicate directions.

  As shown in FIG. 5, when a magnetic field is not generated, infrared rays are incident from the z direction, that is, from the GaAs substrate 31 side. Electrons 25 and holes 26 are excited by infrared rays. The excited electrons 25 and holes 26 flow in the directions indicated by arrows A1 and A2 in FIG. 5 along the inclination of the energy band of the semiconductor, that is, electrons flow to the N layer side (+ z direction). It flows to the P layer side (-z direction).

  On the other hand, when a magnetic field is generated as shown in FIG. 6, among the charges (electrons 25 and holes 26) excited by the received infrared energy, the electrons 25 are in the + z direction, i. An attempt is made to move along the line A1, but since a magnetic flux in the x direction exists, a Lorentz force in the direction of the arrow A1 '(+ y direction) orthogonal to the arrow A1 is received. As a result, it moves along the arrow line A3 obtained by combining the arrow line A1 and the arrow line A1 '. As described above, when a magnetic field in the x direction exists, the electrons 25 move obliquely on the yz plane as indicated by a solid arrow A3.

  Further, the hole 26 moves in the -z direction as indicated by an arrow A2 when there is no magnetic field generating means. However, when a magnetic field in the z direction is applied as shown in FIG. 6, the hole 26 tries to move along the −z direction, that is, along the arrow A2 due to the inclination of the conduction band, but there is a magnetic flux in the x direction. Therefore, it receives the Lorentz force in the direction of the arrow A2 ′ (+ y direction) orthogonal to the arrow A2. As a result, it moves along the arrow line A4 obtained by combining the arrow line A2 and the arrow line A2 '. As described above, when there is a magnetic field in the x direction, the holes 26 also move obliquely on the yz plane as indicated by the solid arrow A4.

From the above, since the electric charge movement path is bent by applying the magnetic field, the resistance value of the infrared sensor increases. The electromotive voltage of the infrared sensor is the product of resistance and photocurrent (current generated by charges excited by infrared rays). Therefore, according to the first embodiment, the electromotive voltage of the infrared sensor can be increased by the amount of increase in the resistance value.
The first embodiment is not limited to the configuration described above. For example, in the configuration described above, a case where a magnetic field having a magnetic flux in the x direction has been described, but the first embodiment is not limited to a configuration in which the magnetic flux generates a magnetic field in the x direction. For example, as shown in FIG. 7, even when a magnetic field whose magnetic flux is in the y direction is generated, the resistance movement of the infrared sensor increases because the charge movement path is bent by the influence of the Lorentz force. The voltage can be increased.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. In the second embodiment, in addition to the infrared sensor of the first embodiment, “field-of-view restriction” for determining the detection area of the infrared sensor is set. Such Embodiment 2 is applied when, for example, it is desired to detect whether a detection target (for example, a human body) exists within a predetermined detection area using an infrared sensor.
FIGS. 8A, 8B, and 8C are diagrams for explaining the infrared sensor according to the second embodiment. FIG. 8A is a top view of the infrared sensor, and FIG. ) Is a cross-sectional view taken along the arrow line BB ′ in FIG. Note that, in the drawings shown in the second embodiment, the configurations described in the first embodiment are denoted by the same reference numerals as in the drawings shown in the first embodiment, and the description thereof is partially omitted.

  In the second embodiment, as shown in FIGS. 8A and 8B, the field limiters 8 and 9 are arranged on the infrared sensor 1. The field limiting body 8 is made of a magnetic material on two sides of the infrared sensor 1 facing each other. On the other two sides, a field limiting body 9 made of a nonmagnetic material is disposed. The magnet 7 is arranged outside the field-of-view restricting body 8 made of a magnetic material so that the N pole and the S pole face each other. With this configuration, it is possible to detect only infrared radiation from the area indicated by the FOV shown in FIG. 8C, and to detect whether there is an infrared detection target in this area. Is possible.

FIGS. 9A and 9B are views for explaining the state of magnetic flux in the vicinity of the infrared light receiving portion 2 of the infrared sensor 1, wherein FIG. 9A is a top view and FIG. 9B is a diagram. It is sectional drawing of (a). The magnetic flux 10 generated from the magnet 7 is converged in the vicinity of the infrared light receiving unit 2 by the field limiter 8 made of a magnetic material and the lead frame 3 in the infrared sensor 1. For this reason, the magnetic flux density in the vicinity of the infrared light receiving unit 2 is further increased.
Due to the increase in magnetic flux density, a larger Lorentz force acts on electrons and holes excited when receiving infrared light. The movement path of electrons and holes is bent by the Lorentz force, and the resistance value of the infrared sensor increases as described above. As the resistance value increases, the electromotive voltage of the infrared sensor increases as compared to the case where no magnetic field is present in the infrared sensor.

  The present invention can be applied to all infrared sensors provided with quantum infrared detection elements.

DESCRIPTION OF SYMBOLS 1 Infrared sensor 2 Infrared light-receiving part 3 Lead frame 4 Wire 5 Resin 6 Magnetic body 7 Magnet 20 P layer 21 Light absorption layer 22 N layer 23, 41 + side electrode 24, 40-side electrode 25 Electron 26 Hole 31 GaAs substrate

Claims (2)

An infrared sensor that converts infrared energy into an electrical signal and extracts it,
A light receiving unit for converting infrared energy into the electrical signal;
Magnetic field generating means for generating a magnetic field that acts to apply a Lorentz force to the electric charge excited by the light receiving unit receiving infrared energy;
With
The infrared sensor according to claim 1, wherein the magnetic field generating means generates a magnetic field that applies a Lorentz force in a direction orthogonal to a direction in which the electric charge moves.   The infrared sensor according to claim 1, further comprising a converging unit that converges the magnetic field generated by the magnetic field generating unit on a light receiving surface of the infrared light receiving unit.

Images