JP5624286B2 - Ultraviolet light detection element and ultraviolet light detection device - Google Patents

Description

  The present invention relates to an ultraviolet light detection element and an ultraviolet light detection device that measure only an ultraviolet light component in light that is naturally exposed to humans.

It is well known that the amount of oxygen in the earth's atmosphere decreases and the amount of CO ₂ increases as humans burn large amounts of fossil fuels. The latter is well-known as a warming gas, but the decrease in the amount of oxygen causes a phenomenon that holes are often opened in the ozone layer that is generated by the ultraviolet light (UV light) of sunlight hitting oxygen in the atmosphere. . This is called the ozone hole.

  With the creation of an ozone hole, white people who live in high latitudes, especially in northern Europe and are not resistant to ultraviolet light, are directly exposed to skin cancer. Further, it is known that ultraviolet light causes deterioration of the skin in the long term even if it does not have such a great influence on the living body. These are well known because the skin of the buttocks that is hardly exposed to sunlight is very beautiful and the skin of the faces of people living in the Takayama region is particularly rough.

  Considering the above situation, knowing how much you have been exposed to ultraviolet light has the cosmetic advantage that you can get a guide on how to take measures to keep your skin healthy. In the long term, it will be the basis for clarifying the relationship between the amount of ultraviolet light and the occurrence of skin cancer and taking preventive measures.

  Erythema and blackening as a response of the human body to ultraviolet rays do not occur by irradiation with only ultraviolet rays. Actually, it is said to be a complex immune reaction caused by simultaneous irradiation with visible light and infrared light. For this reason, if there is an apparatus capable of selectively detecting only ultraviolet rays with high sensitivity under irradiation of light including ultraviolet rays, there is no doubt that it will be a powerful tool for developing care products for ultraviolet light.

Some ultraviolet detection devices use a so-called photoconductive sensor element that detects ultraviolet rays applied to the light receiving unit by a change in the amount of photoinduced current in the light receiving unit. This is a Si semiconductor having a detection sensitivity for visible light having a wavelength in the range of 400 nm to 650 nm, and Al _x Ga _1-x N (0) which has no detection sensitivity for the visible light and the like and noise light in the infrared region. <= X <= 1) The thing etc. which used the semiconductor and the diamond semiconductor as a solid material of a light-receiving part are considered conventionally. The photodetection principle of these photoconductive sensor elements is to generate electron-hole pairs in the semiconductor by irradiating the semiconductor of the light-receiving part with energy with a band gap or more, and this carrier is applied to the externally applied voltage. Is taken out to an external circuit and detected as a photoinduced current amount.

  These are generally called MSM (metal / semiconductor / metal) type light receiving elements. For example, as shown in Patent Document 1, the surface of a diamond single crystal substrate is subjected to hydrogenation treatment, and this hydrogenation treatment is performed. An ultraviolet sensor has been proposed in which positive and negative electrodes are formed in a comb shape on the surface. The amount of ultraviolet rays is measured by absorbing ultraviolet rays with a diamond single crystal substrate and detecting the amount of photoinduced current.

JP 2008-96151 A

  However, in the above configuration, ultraviolet rays are absorbed by the diamond between the electrodes, and there are cases where ultraviolet rays cannot be detected in the region where the electrodes are formed, and the detection efficiency decreases. Further, in order to form an electrode on the surface of the diamond after the production of the diamond, if the surface state of the diamond is caused by adhesion of moisture in the outside air or organic molecules, the contact resistance with the electrode is affected. For this reason, there has been a problem that large variations occur in electrical characteristics such as current-voltage characteristics for each element. In particular, when a material having a high surface chemical activity is used for the ultraviolet light absorption layer, the variation becomes large.

  The present invention has been made to solve the above-described problems, and an ultraviolet light detection element and an ultraviolet light element that can detect ultraviolet light in as wide an area as possible and reduce variations in electrical characteristics of each element. An object of the present invention is to provide a photodetector.

In order to achieve the above object, an ultraviolet light detection element according to the present invention includes a substrate, an ultraviolet light absorption layer that absorbs ultraviolet light disposed on the substrate, and ultraviolet light absorbed by the ultraviolet light absorption layer. And an electrode for measuring a current generated based on the detection electrode unit for detecting a current from the ultraviolet light absorption layer and an extraction electrode unit for extracting the detected current to the outside. The electrode is composed of a pair of a comb-like positive electrode and a negative electrode, the detection electrode part is alternately arranged with strip-like positive and negative electrodes, and the detection electrode part is the ultraviolet The main feature is that the ultraviolet light absorption layer is embedded in the light absorption layer and has irregularities corresponding to the alternately arranged positive and negative electrodes .

  In the ultraviolet light detection apparatus of the present invention, the ultraviolet light detection element is installed on a support base, and a reflection structure for condensing the ultraviolet light on the ultraviolet light detection element is formed on the support base. This is the main feature.

  According to the present invention, among the electrodes for measuring ultraviolet light, the detection electrode portion for detecting the current from the ultraviolet light absorbing layer is buried in the ultraviolet light absorbing layer. Therefore, the contact surface with the detection electrode portion in the ultraviolet light absorption layer is not directly exposed to the outside air, and the state of the contact surface with the electrode can be maintained in a uniform state for each element.

It is a figure which shows the cross section of the ultraviolet light detection element which concerns on this invention. It is a figure which shows the cross section of the ultraviolet light detection element which concerns on this invention. It is a top view of the ultraviolet light detection element which concerns on this invention. It is a figure which shows the other structural example of the ultraviolet light detection element which concerns on this invention. It is a figure which shows the measurement current for every sample at the time of ultraviolet light irradiation in the ultraviolet light detection element which concerns on this invention, and the ultraviolet light detection element of a conventional structure. It is the figure which compared the current-voltage characteristic with the ultraviolet light detection element which concerns on this invention, and the ultraviolet light detection element of a conventional structure. FIG. 7 is a diagram showing the current-voltage characteristic curves of FIG. 6 collectively by changing the scale of the current axis. It is a figure which shows the difference in an electric current-voltage characteristic by the case where an ultraviolet-light absorption layer and an electrode are in ohmic contact, and the case where a Schottky contact is carried out. It is a figure which shows the actual structural example of electrode arrangement | positioning. It is a figure which shows the etching gap which generate | occur | produces after producing a comb-shaped electrode. It is a figure which shows the current-voltage characteristic at the time of using Ni and Ti for an electrode. It is a figure which shows the current-voltage characteristic at the time of using Pt and Al for an electrode. It is a figure which shows the current-voltage characteristic of using soda-lime glass and an alkali free for a board | substrate. It is a figure which shows the sunlight spectrum outside the atmosphere and the atmosphere, and the light reception sensitivity of an ultraviolet light detection element. It is a figure which shows the relationship between a band gap equivalent wavelength and Mg content rate of MgZnO. It is a figure which shows the X-ray-diffraction measurement result of an ultraviolet light absorption layer. It is a figure which shows the structural example of the ultraviolet light detection device in which the ultraviolet light detection element which concerns on this invention was installed. It is a figure which shows the structural example of the ultraviolet light detection apparatus using an ultraviolet light detection device. It is a figure which shows the structural example of the ultraviolet-light detection apparatus with an openable / closable lid. It is a figure which shows the example of a form of a strip-shaped electrode.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic and different from the actual ones. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.

  The ultraviolet light detection apparatus of the present invention basically includes an ultraviolet light detection element including a substrate, an ultraviolet light absorption layer that absorbs ultraviolet light, and an electrode that measures current generated in the ultraviolet light absorption layer.

  First, as an example of the ultraviolet light detection element, a configuration as shown in FIGS. 3 is a plan view of the ultraviolet light detection element as seen from above, FIG. 1 shows a cross section taken along the line AA in FIG. 3, and FIG. 2 shows a cross section taken along the line BB in FIG. Note that FIG. 3 is shown with the protective film 5 removed for the sake of clarity.

  An electrode 2 and an electrode 3 are formed on the substrate 1. When the electrode 2 is a positive electrode, the electrode 3 corresponds to a negative electrode, and when the electrode 2 is a negative electrode, the electrode 3 corresponds to a positive electrode. The electrode 2 and the electrode 3 are formed in a comb shape as shown in FIG. The comb-shaped electrode 2 includes a strip-shaped detection electrode portion 2a and a common extraction electrode portion 2b, and a plurality of detection electrode portions 2a are integrally formed on the extraction electrode portion 2b. The comb-shaped electrode 3 is also composed of a strip-shaped detection electrode portion 3a and a common extraction electrode portion 3b. The extraction electrode portion 3b is integrally formed with a plurality of detection electrode portions 3a. . In the embodiment of FIGS. 1 to 3, four detection electrode portions 2a and four detection electrode portions 3a are formed. Moreover, the detection electrode part 2a and the detection electrode part 3a are arrange | positioned so that it may not mutually overlap.

  Here, the detection electrode portions 2a and 3a corresponding to the strip-shaped portions of the comb-shaped electrode need only be alternately nested, and can be configured as follows. For example, as shown to Fig.20 (a), it does not need to be a rectangular parallelepiped type, You may make it form in a waveform shape and have a curved part. Further, as shown in FIG. 20B, the detection electrode portions 2a and 3a may be rounded at the tip. Next, as shown in FIG. 20C, the electrode widths of the detection electrode portions 2a and 3a may not be constant, and the distance between the electrodes may not be constant. Further, as shown in FIG. 20C, the length of the electrode may not be constant. In the present invention, including all of the above forms, it is called a strip-shaped detection electrode portion.

  An ultraviolet light absorption layer 4 is laminated on the electrodes 2 and 3. The ultraviolet light absorption layer 4 is composed of a material that absorbs ultraviolet light and generates electrons and holes, and is composed of, for example, a semiconductor layer having a photoelectric effect. Here, what is characteristic is that the electrodes are not arranged on the surface of the ultraviolet light absorption layer as in the conventional configuration, but the detection electrode portions 2a and 3a electrodes that directly detect carriers in contact with the ultraviolet light absorption layer 4 are: It is embedded in the ultraviolet light absorption layer 4.

  As can be seen from FIGS. 1 to 3, the surfaces of the detection electrode portion 2 a and the detection electrode portion 3 a that are in contact with the ultraviolet light absorption layer 4 in the regions of the electrodes 2 and 3 are all covered with the ultraviolet light absorption layer 4. It is formed so as not to be exposed. In addition, the ultraviolet light absorption layer 4 is laminated on a part of the extraction electrode portions 2b and 3b on the side close to the detection electrode portions 2a and 3a. As described above, the electrode is not disposed at all on the surface of the ultraviolet light absorption layer 4.

  A wire 6 is bonded to a region not covered with the ultraviolet light absorption layer 4 on the extraction electrode portions 2b and 3b. The extraction electrode portions 2b and 3b are electrode portions for extracting the current based on the generated electrons and holes when the ultraviolet light is absorbed by the ultraviolet light absorption layer 4, and this current is output to the outside by the wire 6. Take out. For this reason, it is necessary to apply a DC bias between the electrode 2 and the electrode 3, and a DC power source is connected as shown in FIG. The bias voltage can be varied. In order to extract the detection current to the outside, the electrodes 2 and 3 may be die-bonded to the external connection electrodes or the like with a soldering agent without using the wire 6.

The ultraviolet light absorbing layer 4 is desirably made of a material having high resistance and selectively absorbing only ultraviolet light. High resistance is desirable because it is necessary to distinguish between carriers generated by ultraviolet light and currents generated by a bias applied to the element. In order to satisfy these requirements, examples of the oxide material include ZnO, MgZnO, TiO ₂ , SrTiO ₂ , and InGaNZnO. Further, InGaN, AlGaN, GaN or the like may be used. These are materials having a band gap that does not absorb light in the visible light region, and are materials having a high resistance value. In this example, Mg _X Zn _1-X O (0 ≦ X ≦ 0.6) was used.

On the other hand, the substrate 1 is desirably a high-resistance material that does not absorb ultraviolet light and is transparent and does not generate extra current. For example, glass can be used. The protective film 5 has a waterproof, moisture-proof, scratch-proof function, etc., and SiN, SiO ₂ or the like is used. Generally, since SiN is superior in waterproofness, it is often used, but since the ultraviolet light detection device of the present invention absorbs and detects ultraviolet light, colored SiN is not preferable, it is desirable to use SiO _2. Note that the protective film 5 may not be formed.

  Further, as shown in FIG. 1, since the ultraviolet light absorption layer 4 is laminated on the detection electrode portions 2a and 3a, the surface of the ultraviolet light absorption layer 4 is usually uneven with the detection electrode portions 2a and 3a. It becomes the shape along. Further, since the protective film 5 is laminated on the ultraviolet light absorbing layer 4 on which the unevenness is formed, the surface of the protective film 5 is usually formed with unevenness along the unevenness of the detection electrode portions 2a and 3a. Will be. These irregularities work advantageously when guiding ultraviolet light into the ultraviolet light absorbing layer 4. If there are no irregularities, total reflection tends to occur due to the difference in refractive index between the air layer and the ultraviolet light absorption layer 4 or the protective film 5, but the incidence angle of ultraviolet light varies due to the irregularities. The total reflection can be reduced and the detection efficiency of ultraviolet light is increased.

  The electrodes 2 and 3 are arranged so as to be in contact with the substrate 1 and the ultraviolet light absorption layer 4 is used to fill the detection electrode portions 2a and 3a. However, as shown in FIG. Anyway. The surroundings of the detection electrode portions 2a and 3a are configured to be encased in the ultraviolet light absorption layer 4. In this case, since the electrode can be arranged on the film surface side where light absorption is larger, a large photo-induced current can be obtained. Moreover, since it is far from the dissimilar interface (glass / ZnO), the variation factor is reduced.

  FIG. 9 is a configuration example of a pattern in which comb-shaped electrodes 2 and 3 are actually formed. On the upper side, the arrangement pitch of the detection electrode portions 2a, 3a is 20 μm, and on the lower side, the pitch is 10 μm. FIG. 10 shows an enlarged view of the portion surrounded by these dotted lines. When the detection electrode portions 2a and 3a are formed, if the pitch is small, it is desirable to form the electrode pattern by etching in order to manufacture with high accuracy. Further, when etching the ultraviolet light absorbing layer, etching etching may occur near the substrate 1 or the electrode as shown in FIG. Due to this etching failure, when the ultraviolet light absorption layer 4 is laminated only on the detection electrode portions 2a and 3a, the ultraviolet light absorption layer 4 does not cleanly join the detection electrode portions 2a and 3a and the substrate 1, and the ultraviolet light absorption layer 4 There is a risk that will peel off. Therefore, as in the present embodiment, the peeling electrode portions 2b and 3b are fabricated such that a part of the extraction electrode portions 2b and 3b is laminated with the ultraviolet light absorption layer 4, thereby preventing this peeling.

  As in the present invention, several ultraviolet light detection elements having a configuration in which the detection electrode portions 2a and 3a are embedded in the ultraviolet light absorption layer 4 were produced. In addition, several conventional ultraviolet light detection elements in which electrodes are formed in the conventional configuration described in FIG. 1 of Patent Document 1, that is, exposed on the surface of the ultraviolet light absorption layer, were manufactured. And the fluctuation | variation of these ultraviolet light detection states was compared. The ultraviolet light detection element of the present invention is referred to as a buried electrode type, and the conventional ultraviolet light detection element is referred to as a surface electrode type.

  For the ultraviolet light absorbing layer, ZnO was used for both the buried electrode type and the surface electrode type. Ti was used for the comb electrodes, and glass was used for the substrate on which the ultraviolet light absorption layer was formed. Then, a plurality of buried electrode types and surface electrode types were produced, and the variation in electrical characteristics of each element was examined. FIG. 5 shows the measurement of the value of the current flowing through the element by irradiating each type of ultraviolet light detecting element with ultraviolet light having a wavelength of 365 nm at a certain intensity.

  FIG. 5A shows a buried electrode type element, but it can be said that the measurement current of the ultraviolet light is almost the same for 11 samples and there is almost no fluctuation. FIG. 5B shows a surface electrode type element, but the fluctuation of the measurement current of ultraviolet light is very large for 45 samples. Thus, it can be seen that the buried electrode type of the present invention is preferable to the conventional surface electrode type element because the fluctuation of the ultraviolet light detection current for each manufactured element is much smaller.

  On the other hand, for the buried electrode type and the surface electrode type, the current-voltage characteristic (IV characteristic) when irradiated with ultraviolet light having a wavelength of 365 nm, and the current-voltage characteristic of dark current when not irradiated with ultraviolet light, as described above. IV characteristics) were compared. The intensity of ultraviolet light was kept constant, and the IV characteristics were measured by changing the bias. This is shown in FIG.

  6A shows a buried electrode, and FIG. 6B shows a surface electrode type. In FIG. 6, a graph (upper curve) described as UV ON is an IV characteristic at the time of ultraviolet light irradiation, and a dark current when the graph described as UV OFF (lower curve) is not irradiated with light at all. IV characteristics. Comparing these, as can be seen, both the IV characteristics at the time of ultraviolet light irradiation and the IV characteristics of the dark current have a larger variation for each element in the surface electrode type. FIG. 7 shows a diagram in which the most extreme examples of this difference are collectively displayed and the scale of the current value on the vertical axis is enlarged.

  Curve S1 drawn by connecting white circles in FIG. 7 shows IV characteristics (corresponding to UV ON in FIG. 6B) when the surface electrode type element is irradiated with ultraviolet light, and is drawn by connecting white circles. Curve S1 shows the IV characteristic of the dark current of the surface electrode type element (corresponding to UV OFF in FIG. 6B). A curve I1 shows an IV characteristic (corresponding to UV ON in FIG. 6A) when the buried electrode type element is irradiated with ultraviolet light, and a curve I2 shows the dark current IV of the buried electrode type element. Characteristics (corresponding to UV OFF in FIG. 6A) are shown. From this figure, it can be clearly seen that the surface electrode type element has a larger variation in IV characteristics for each element in both the ultraviolet light irradiation state and the ultraviolet light off state. It is not suitable for photodetection devices.

  Next, the ultraviolet light absorption layer 4 and the electrodes 2 and 3 are configured to be in ohmic contact. In this embodiment, the portions of the detection electrode portions 2a and 3a and the extraction electrode portions 2b and 3b that are in contact with the ultraviolet light absorption layer 4 form ohmic contact.

  As shown in FIG. 8, when the ultraviolet light absorption layer 4 and the electrodes 2 and 3 are in ohmic contact, the relationship between the detected current and the voltage when the ultraviolet light amount is increased or decreased is as shown by a solid line. And has a proportional relationship. However, in the case of Schottky contact, as indicated by the dotted line, the detection current and the voltage do not form a proportional relationship, and thus a detection current proportional to the ultraviolet light amount cannot be obtained. Further, in the region where the detection current hardly changes, when there is a switching point between the ON and OFF of the ultraviolet light, it is difficult to distinguish ON / OFF distinction. Therefore, in order to measure the difference in the amount of ultraviolet light depending on the detected current amount, it is important to make ohmic contact.

In the case where Mg _X Zn _1-X O (0 ≦ X ≦ 0.6) is used for the ultraviolet light absorption layer 4, a metal that is likely to be in ohmic contact with this MgZnO is examined, as shown in FIGS. It was. In FIGS. 11 and 12, the detected current characteristic when irradiated with ultraviolet light having a wavelength of 365 nm is indicated by ON (solid line), and the dark current (dotted line) characteristic is indicated by OFF.

  FIG. 11A shows the case where nickel (Ni) is used for the electrodes 2 and 3. In the case of Ni, although the OFF characteristic curve is close to the lower limit of measurement, ON-OFF distinction is attached. The work function of Ni is 5.15 eV (electron volts). FIG. 11B shows the case where titanium (Ti) is used for the electrodes 2 and 3. In the case of Ti, the ON / OFF distinction is sufficient. The work function of Ti is 4.33 eV.

  On the other hand, FIG. 12A shows a case where platinum (Pt) is used for the electrodes 2 and 3. In the case of Pt, ON / OFF distinction is sufficient. The work function of Pt is 5.65 eV. However, since it is easy to peel off, it is not preferable as an electrode material. FIG. 12B shows the case where aluminum (Al) is used for the electrodes 2 and 3. In the case of Al, it is difficult to distinguish between ON and OFF. Al is said to be in ohmic contact with ZnO, but is not suitable for this device. The work function of Al is 4.28 eV.

In summary, the following contents can be defined in consideration of not only ohmic contact but also factors such as difficulty of peeling. When Mg _X Zn _1-X O (0 ≦ X ≦ 0.6) is used for the ultraviolet light absorption layer 4, the work functions of the electrodes 2 and 3 are in the range of 4.3 eV or more and 5.2 eV or less. It is necessary to use an electrode material.

It is desirable to use glass for the substrate 1 for the reasons described above. However, there are various types of glass, and it is desirable to select as follows. FIG. 13 shows the detection current characteristics of the ultraviolet light detection element when soda lime glass is used for the substrate 1 and when non-alkali glass is used. 1 to 3, Mg _X Zn _1-X O (0 ≦ X ≦ 0.6) is used for the ultraviolet light absorption layer 4, and Ti is used for the electrodes 2 and 3. It was. UV ON (solid line) describes the IV characteristic of the detected current when irradiated with ultraviolet light, and Dark (dotted line) describes the IV characteristic of the dark current.

    FIG. 13A shows a case in which soda lime glass is used for the substrate 1, and an element that makes it difficult to determine whether ultraviolet light is on or off appears and varies. On the other hand, FIG. 13B shows a case where non-alkali glass widely used for liquid crystal displays is used for the substrate 1, and UV light can be discriminated sufficiently between ON and OFF. There are no variations. Thus, in order to keep the electrical characteristics of the element stable, it is desirable to use an alkali-free glass for the substrate 1.

In addition, when Mg _X Zn _1-X O (0 ≦ X ≦ 0.6) is used for the ultraviolet light absorption layer 4 and it is fabricated by sputtering as will be described later, it does not have a specific crystal orientation. . The term “not having a specific crystal orientation” means a structure other than a single crystal whose crystal axes are all aligned, and includes a polycrystalline structure, an amorphous structure, and the like.

  This is shown in FIG. MgZnO was produced by sputtering as the ultraviolet light absorption layer 4, and MgZnO was measured by XRD (X-ray diffraction). The vertical axis represents the XRD intensity (count), and the horizontal axis represents the angle 2θ (degrees). As is well known, θ represents the angle of the sample with respect to the incident X-ray. As can be seen from FIG. 16, the intensity is not particularly high at a specific angle θ, and 1000 counts are not counted at all angles. In a crystal having a specific orientation, about 100,000 counts are counted for a specific angle. Therefore, FIG. 16 also shows that it does not have a specific crystal orientation.

  When there is no specific crystal orientation as described above, there are the following effects. For example, a semiconductor having a wurtzite structure, such as a ZnO-based compound, is distorted due to a difference in lattice constant between a substrate and a ZnO-based compound layer or a stacked semiconductor layer, and a piezoelectric field (due to stress) is generated based on the strain. Generated electric field). This becomes a problem particularly when stacked in the c-axis direction. Problems such as a piezo electric field are undesirable because they affect the ultraviolet light detection current characteristics. However, such a piezo electric field is not generated when a specific crystal orientation is not provided.

FIG. 14 shows the relationship between the solar spectrum and the light receiving sensitivity when the ultraviolet light detection element according to the present invention is irradiated with ultraviolet light. In FIG. 14, the horizontal axis represents wavelength (nm), the left vertical axis represents light receiving sensitivity (A / W), and the right vertical axis represents irradiation energy density (mW · cm ⁻² · nm ⁻¹ ). The light receiving sensitivity is represented by a ratio between the amount of incident light (watts) to the element and the photocurrent (ampere) flowing through the element.

  As shown in the figure, the ultraviolet light region is further classified into ultraviolet light A (wavelength greater than 320 nm and less than or equal to 400 nm), ultraviolet light B (wavelength greater than 280 nm and less than or equal to 320 nm), and ultraviolet light C (wavelength less than 280 nm). The

By the way, the light receiving sensitivity of the ZnO-based ultraviolet light detecting element is a noise level of the measuring apparatus in a range exceeding the wavelength of 400 nm, and is substantially zero. In particular, in the wavelength range of ultraviolet light A and ultraviolet light B having a wavelength of 400 nm or less, it has a high sensitivity of 10 ⁻² A / W or more.

  The sunlight spectrum shows the spectrum of sunlight in the atmosphere and sunlight outside the atmosphere. A solid curve indicated as 50% indicates the light receiving sensitivity of the ultraviolet light detecting element when the Mg content X is 50%. A solid curve indicated as 57% indicates the light receiving sensitivity of the ultraviolet light detection element when the Mg content X is 57%. Thus, in the sunlight in the atmosphere, spectral components having a short wavelength in the ultraviolet light region disappear due to absorption in the air, and there are no spectral components in the ultraviolet light C region. Therefore, if the sensitivity of the ZnO-based ultraviolet light detection element can be set as shown by the solid line in the figure, sunlight in the atmosphere cannot be detected.

If the Mg content of the MgZnO semiconductor is increased too much, the crystal structure may change and the direct transition semiconductor may be lost, but as can be seen from FIG. 14, the characteristics are maintained even when the Mg content X is 57%. The upper limit of X of Mg _X Zn _1-X O can be 60% or less.

FIG. 15 is a graph showing the relationship between the X value of Mg _X Zn _1-X O and the band gap equivalent wavelength (nm) with respect to the Mg content. The band gap equivalent wavelength is related to the absorption wavelength point (nm) of the semiconductor. The larger the value of X, the shorter the absorption wavelength of Mg _X Zn _1-X O. As can be seen from FIG. 15 and FIG. 14, the light receiving sensitivity region of the ultraviolet light detection element can be changed by changing the Mg content _{X of} Mg _X Zn _1-X O. Further, if two ultraviolet light detection elements of MgZnO and ZnO, or two ultraviolet light detection elements having different Mg contents X are arranged, the ultraviolet light amounts of the ultraviolet light A and the ultraviolet light B can be distinguished.

    First, FIG. 17 shows an embodiment of a packaged ultraviolet light detection device including the ultraviolet light detection element of the present invention. FIG. 17A is a plan view seen from above, and FIG. 17B is a cross-sectional view taken along the line C-C in FIG.

  Reference numeral 20 denotes an ultraviolet light detection element according to the present invention, which has, for example, the structure shown in FIGS. The ultraviolet light detection element 20 is disposed in the recess of the support base 21. Connection electrodes 22 and 23 are formed in the recesses of the support base 21 to extract externally detected photocurrents. The connection electrodes 22 and 23 are provided corresponding to the positive electrode and the negative electrode of the ultraviolet light detection element 20, and are connected to each other by wires or the like. The support base 21 is provided with a reflection structure for ultraviolet light in order to concentrate ultraviolet light on the ultraviolet light detection element and increase detection efficiency. Here, the connection electrodes 22 and 23 are plated with silver white metal such as Ag. As another reflective structure, the concave portion of the package 21 may be formed like a concave mirror, and the surface may be coated with a reflective film.

  FIG. 18 shows a configuration example of an ultraviolet light detection apparatus that discriminates the amount of ultraviolet light A and ultraviolet light B from each other. FIG. 18 is a plan view of the ultraviolet light detection apparatus. Ultraviolet light detection devices 50 and 60 as shown in FIG. 17 are attached to the bottom surface of a resin case (housing) 37 with an adhesive or the like. Although not shown, a bias is applied to the ultraviolet light detection elements installed in the ultraviolet light detection devices 50 and 60. Further, the battery 34 and the received light amount integrating circuit 35 are attached to the bottom surface of the case 37 with an adhesive or the like. Here, for example, 50 is a ZnO-based ultraviolet light detection device, and 60 is a MgZnO-based ultraviolet light detection device.

  The battery 34 is a power source for the received light amount integrating circuit 35, and supplies a voltage via the wiring 31. The received light amount integrating circuit 35 is for integrating the amount of ultraviolet light received by the ultraviolet light detection devices 50 and 60. A current proportional to the amount of received light flows through the ultraviolet light detection devices 50 and 60, but the current value and power are proportional. Therefore, the received light amount integrating circuit 35 calculates the product (watt × time) of the power and the time when the current is detected. Further, the electric power is calculated by the received light amount integrating circuit 35 via the wirings 32 and 33 for taking out the current flowing through the ultraviolet light detection devices 50 and 60.

  Here, the total amount of light is calculated via the wiring 32, the amount of light having a wavelength of, for example, the ultraviolet light B or less is calculated via the wiring 33, and these are subtracted to obtain only the amount of light in the wavelength region of the ultraviolet light A. calculate.

  On the surface of the case 37, a received light amount display unit 36 formed of a reflective LCD (liquid crystal) is provided. The reason why the received light amount display unit 36 is a reflective LCD is to facilitate visual recognition outdoors. The upper surface of the case 37 has an opening for taking in light such as sunlight. The amount of ultraviolet light integrated by the received light amount integrating circuit 35 is displayed on the received light amount display unit 36 via a wiring (not shown). The case 37 does not need to be a square, and may be formed in a shape that is easy to design, such as a circle, a triangle, or a fan shape.

  Here, the influence on the human body is different between the ultraviolet light A and the ultraviolet light B, and the ultraviolet light A has a longer wavelength and reaches the back of the epidermis cells, causing the skin to lose its gloss and the like through the degradation of collagen. .

  Ultraviolet light B is absorbed only near the epidermis because of its short wavelength, but short wavelength increases energy and triggers sunburn phenomenon and skin cancer. Since the ultraviolet light C hardly reaches the surface of the earth due to absorption of the ozone layer, the ultraviolet light A and the ultraviolet light B have a substantial effect.

  In particular, ultraviolet light A passes through glass and the like, so it has a great influence in the room and has a deep penetration into the skin. It is being recognized as a good UV. As described above, since there is a difference in the action of the ultraviolet light A and the ultraviolet light B on the human body, it is significant to distinguish and measure the amount of the light and discriminate the difference in the effect.

Next, a method for manufacturing the ultraviolet light detection element and the ultraviolet light detection device described above will be briefly described. Glass was used for the substrate 1, titanium was used for the electrodes 2 and 3, and Mg _X Zn _1-X O was used for the ultraviolet light absorption layer 4.

  An electrode made of Ti is formed in a comb shape on a glass substrate to a thickness of about 50 nm to 300 nm. This step may be a lift-off method or an etching method. When the width of the detection electrode portion of the comb-shaped electrode is approximately 5 μm or less, the etching method is desirable from the viewpoint of ensuring reproducibility.

  Next, an MgZnO film is formed by sputtering. The film thickness is desirably 100 nm or more. If the film thickness is too thin, the MgZnO film cannot sufficiently absorb ultraviolet light. Here, as shown in FIG. 4, when surrounding the comb-shaped electrode with an ultraviolet light absorbing layer, an MgZnO film is first formed to a predetermined thickness by sputtering. Thereafter, as described above, an electrode made of Ti is formed in a comb shape to a thickness of about 50 nm to 300 nm. Next, an MgZnO film is formed again by sputtering.

  Next, in order to secure the wire bonding region of the comb-shaped electrode, the MgZnO film covering the end of the comb-shaped electrode is removed by etching with diluted hydrochloric acid. Although dry etching may be used, residues are easily left in the ZnO-based material, so that wet etching is easy.

  Grind and thin the glass substrate. Although there is no particular problem even if it is not thinned, it is preferable to make a thin-shaped ultraviolet light detection device because the package can be thinned if the element is thinned.

    The ultraviolet light detection element completed as described above is packaged, for example, by die bonding with Ag paste, epoxy resin or the like on a support base as shown in FIG. Thereafter, the element and the package side electrode are connected by a wire.

  The packaged device is mounted on a printed board as shown in FIG. The printed circuit board is mounted on a housing, and a lid is attached to complete the ultraviolet light detection device.

  The configuration of the ultraviolet light detection apparatus of the present invention can be applied to a wide range of devices such as a handy type UV detector, an SPF analyzer, a flame sensor, and a spark sensor.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 2a Detection electrode part 2b Extraction electrode part 3 Electrode 3a Detection electrode part 3b Extraction electrode part 4 Ultraviolet absorption layer 5 Protective film 6 Wire

Claims (14)

A substrate,
An ultraviolet light absorbing layer that absorbs ultraviolet light disposed on the substrate;
An electrode for measuring a current generated based on ultraviolet light absorbed by the ultraviolet light absorbing layer,
The electrode includes a detection electrode portion for detecting a current from the ultraviolet light absorption layer and a take-out electrode portion for taking out the detected current to the outside, and the electrode is a comb-shaped positive electrode The detection electrode unit is formed by alternately arranging strip-shaped positive electrodes and negative electrodes, and the detection electrode unit is embedded in the ultraviolet light absorption layer and the ultraviolet light absorption layer. Has an unevenness corresponding to the alternately arranged positive and negative electrodes .   The ultraviolet light detection element according to claim 1, wherein the electrode is disposed in contact with the substrate. The ultraviolet light detection element according to claim 1, wherein a protective film having unevenness corresponding to the unevenness of the ultraviolet light absorbing layer is formed on the ultraviolet light absorbing layer. The ultraviolet light detection element according to any one of claims 1 to 3, wherein the ultraviolet light absorption layer is laminated on a part of the extraction electrode portion of the electrode. The ultraviolet detection element according to claim 1, wherein the electrode forms an ohmic contact with the ultraviolet light absorption layer. The ultraviolet light absorbing layer is made of Mg. _X Zn _1-X The ultraviolet light detection element according to claim 1, wherein the ultraviolet light detection element is configured by O (0 ≦ X ≦ 0.6). The ultraviolet detection element according to claim 6, wherein the electrode is made of a material having a work function of 4.3 eV or more and 5.2 eV or less. The ultraviolet detection element according to claim 1, wherein the substrate is made of glass. The ultraviolet light detection element according to claim 1, wherein the ultraviolet light absorption layer does not have a specific crystal orientation. The ultraviolet light detection element of any one of Claims 1-9 is installed in a support base, The reflection structure for condensing ultraviolet light to this ultraviolet light detection element is formed in the said support base. An ultraviolet light detection device characterized by comprising: The ultraviolet light detection apparatus according to claim 10, wherein the reflection structure is a structure in which a surface of a connection electrode formed on the support base is plated with a silver-white metal. 12. The ultraviolet light detection device according to claim 10, comprising two ultraviolet light detection elements that detect two different wavelength regions in the wavelength region of ultraviolet light. The ultraviolet light detection apparatus according to claim 10, further comprising a reflective liquid crystal display that displays a result of detecting ultraviolet light by the ultraviolet light detection element. The ultraviolet light detection device according to any one of claims 10 to 13, wherein the ultraviolet light detection element is housed in a housing, and the housing includes an openable / closable lid. .

Images