JP7171182B2 - Optical Densitometer - Google Patents

Description

The present invention relates to an optical density measuring device.

Among optical devices, infrared light receiving devices that output signals corresponding to received infrared rays have come to be used in the field of optical communication, the field of energy saving, and the environmental field such as gas sensors.

In addition, among optical devices, an infrared light emitting device that emits infrared light is being developed in the form of a light emitting diode that emits light by injected current.

By providing a light-emitting element and a light-receiving element in the same device and further providing an optical path between the light-emitting element and the light-receiving element, signal transmission by light exchange becomes possible in the same device. Light propagating through this optical path can be used to sense various physical quantities. One example is a gas sensor.

JP 2012-220351 A

Since the conventional device uses the space between the light emitting element and the light receiving element as an optical path (Patent Document 1), there is a problem that the device becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical density measuring apparatus that can be miniaturized.

An optical density measuring device according to one aspect of the present invention is an optical density measuring device for measuring the concentration of a gas or liquid to be measured , comprising: a substrate; a first layer formed directly and having a higher refractive index than the substrate; a light emitting element formed on the first layer and having a first semiconductor laminate; and a light-receiving element capable of receiving light emitted from the light-emitting element and having passed through the first layer , wherein the first layer includes the Between the light-emitting element and the light-receiving element, the first layer is thinner or narrower than the other portions, and is formed to have a thickness that allows light to propagate and part of the light to leak out into the environment. It has an optical path, and at least the optical path of the first layer is provided so as to be able to come into contact with the gas to be measured or the liquid to be measured .

Further, an optical density measuring device according to another aspect of the present invention is an optical density measuring device for measuring the density of a gas or liquid to be measured, comprising: a substrate; a first layer formed on a substrate and formed between the substrate and the first layer in direct contact with the substrate and the first layer, and having a lower refractive index than the first layer; a second layer, a light-emitting element formed on the first layer and having a first semiconductor laminate, and a second semiconductor laminate formed on the first layer, wherein the light-emitting element and a light-receiving element capable of receiving light emitted from the element and passing through the first layer, wherein the first layer is positioned between the light-emitting element and the light-receiving element. has an optical path that is narrower or thinner than other portions of the layer of and is formed to a thickness that allows light to propagate and part of the light to leak into the environment, and at least the first layer of The optical path is provided so as to be able to come into contact with the gas to be measured or the liquid to be measured.

According to each aspect of the present invention , the optical density measuring device is miniaturized.

It is a figure which shows the structural example of the cross section of the optical device based on the 1st structural example of this embodiment. It is a figure which shows the structural example of the cross section of the optical device based on the 2nd structural example of this embodiment. It is a figure which shows the structural example of the cross section of the optical device based on the 3rd structural example of this embodiment. It is a figure which shows the structural example of the cross section of the optical device based on the 4th structural example of this embodiment. FIG. 11 is a diagram showing a cross-sectional configuration example of a light receiving and emitting element provided in an optical device according to a fifth configuration example of the present embodiment;

Hereinafter, the present invention will be described through embodiments, but the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution of the present invention.

<Optical device>
An optical device according to this embodiment includes a substrate, a first layer formed on the substrate with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate, and formed on the first layer. and a light emitting element formed on the first layer and having a second semiconductor laminate, wherein light emitted from the light emitting element and passing through the first layer is emitted from the light emitting element. and a light-receiving element capable of receiving the

According to the optical device of this embodiment, miniaturization is possible by forming the light-emitting element, the light-receiving element, and the optical path (first layer) on the same substrate.

The refractive index of the substrate and the first layer may be obtained from the behavior of the light beam that actually travels when an infrared ray with a wavelength of 1 to 12 μm is transmitted at an appropriate angle, or the absolute value of the refractive index of the material of each layer. can be obtained from

A second layer having a refractive index different from that of the first layer may be provided between the substrate and the first layer (in this case, n1 is the refractive index of the first layer, and n1 is the refractive index of the second layer). If n2 is the refractive index and ns is the refractive index of the substrate, it is more preferable to satisfy n1>n2 and n1≧ns). By doing so, it is possible to efficiently exchange light between the light-emitting element and the light-receiving element.

<Optical density measuring device>
An optical concentration measuring apparatus according to this embodiment is an apparatus for measuring the concentration of a gas or liquid to be measured, and includes the optical device of this embodiment. At least part of the first layer provided in the optical device is provided so as to be able to come into contact with the gas to be measured or the liquid to be measured.

When at least a portion of the first layer is in contact with the gas or liquid to be measured, the variation in light propagating through the first layer as an optical path increases when the concentration of the gas or liquid to be measured changes. Therefore, it may be particularly preferable in the field of sensing.

Light emitted from the light-emitting element passes through the first layer and enters the light-receiving element. At this time, part of the light passing through the first layer is emitted as evanescent light by the gas or liquid to be measured. will be absorbed. By calculating the amount of absorption based on the signal detected by the light receiving element, it is possible to measure the concentration of the gas or liquid to be measured.

Hereinafter, each component of the optical device and the optical density measuring apparatus according to this embodiment will be described with an example.

<Substrate>
The substrate is not particularly limited as long as the first layer can be formed thereon (that is, the surface of the substrate). The substrate is specifically a silicon (Si) single crystal (refractive index of about 3.4 at a wavelength of 5 μm), a gallium arsenide (GaAs) single crystal (refractive index of about 3.3 at a wavelength of 5 μm), or an aluminum oxide single crystal. (For example, it may be made of sapphire (refractive index near wavelength of 5 μm: 1.6)). The substrate may be made of a single material (for example, Si single crystal, GaAs single crystal, sapphire, etc.), or may be made of a laminate of multiple materials. For example, a layered portion of Si and SiO ₂ in the SOI substrate may be used as the substrate (in this case, Si on SiO ₂ can be used as the first layer; Since the refractive index of layer 1 is greater than that of SiO ₂ , it shall satisfy the relation “the refractive index of the first layer is greater than the refractive index of the substrate”). Also, a semiconductor layer epitaxially grown on a semiconductor substrate such as Si or GaAs may be used as the substrate.

<First layer>
A first layer is formed on the substrate. The thickness of the first layer is 0.1 μm or more and 100 μm or less. The first layer has a higher refractive index than the substrate. A specific example of the first layer may be a layer formed of a semiconductor material containing In or Sb, or Si. Specific examples of the semiconductor material from which the first layer is formed include InSb and InAsSb.

<Second layer>
The second layer is a layer provided between the substrate and the first layer and having a different refractive index from the first layer. When the refractive index of the second layer is lower than that of the first layer, the light incident on the first layer is confined within the first layer, and the propagation loss of light in the first layer is reduced. There is

The second layer may be made of an insulating material having a resistivity of 10 kΩ·cm or more and 1 GΩ·cm or less. Specific examples of materials for forming the second layer include materials using Al, Ga, In, As, etc., and SiO ₂ . By changing the mixing ratio of the materials forming the second layer, it is possible to realize the second layer having a refractive index different from that of the first layer, which may be preferable. Also, the second layer may have a multilayer structure instead of a single layer structure. For the second layer, for example, two layers with different refractive indexes may be alternately laminated to form a mirror utilizing the interference effect of light.

<Light emitting element>
The light emitting element is formed on the first layer and has a first semiconductor laminate. A light-emitting element emits light by injected current. Types of light-emitting elements include light-emitting diodes (LEDs).

The first semiconductor lamination portion may be made of a single-crystal semiconductor material from the viewpoint of enhancing light emission efficiency. When the first semiconductor laminate is made of a semiconductor material, the first semiconductor laminate may have at least one of an n-type semiconductor layer and a p-type semiconductor layer. The configuration of the first semiconductor lamination portion includes a lamination portion in which an n-type semiconductor layer and a p-type semiconductor layer are laminated when the first semiconductor lamination portion has both an n-type semiconductor layer and a p-type semiconductor layer. Examples include a configuration having a pn junction and a configuration having a pin junction further including an i-type semiconductor layer between the n-type semiconductor layer and the p-type semiconductor layer.

If the first semiconductor layer stack comprises a semiconductor material, the first semiconductor layer stack may be made of group III or group V elements. Specific examples of Group III or Group V elements include elements that emit infrared rays in the 1 μm to 12 μm wavelength band. Specific materials for forming the first semiconductor lamination include InSb (having a refractive index of about 4), AlGaSb, InAs, InAlSb, and InAsSb. The first semiconductor laminate using these forming materials can set the emission wavelength band from several micrometers to ten and several micrometers, and is applied to gas sensors using the non-dispersive infrared (NDIR) method. can. From the viewpoint of manufacturability, it may be preferable that the first semiconductor lamination portion and the later-described second semiconductor lamination portion are made of the same material.

<Light receiving element>
The light receiving element is formed on the first layer and has a second semiconductor laminate. From the viewpoint of improving the optical coupling property, it is sometimes preferable that the material of the second semiconductor lamination portion in contact with the first layer has a higher refractive index with respect to infrared rays with a wavelength of 5 μm than the material of the first layer. be. The portion in contact with the first layer is the bottom layer of the second semiconductor laminate. The first semiconductor lamination part and the second semiconductor lamination part may be made of the same material and have the same lamination structure. In other words, the second semiconductor lamination portion may be made of a single-crystal semiconductor material from the viewpoint of enhancing the light receiving efficiency. When the second semiconductor laminate is made of a semiconductor material, the second semiconductor laminate may have at least one of an n-type semiconductor layer and a p-type semiconductor layer. The configuration of the second semiconductor lamination portion includes a lamination portion in which an n-type semiconductor layer and a p-type semiconductor layer are laminated when the second semiconductor lamination portion has both an n-type semiconductor layer and a p-type semiconductor layer. Examples include a configuration having a pn junction and a configuration having a pin junction further including an i-type semiconductor layer between the n-type semiconductor layer and the p-type semiconductor layer. Moreover, as a configuration of the second semiconductor lamination portion, a photoconductive configuration having one of an n-type semiconductor layer, a p-type semiconductor layer, and an i-type semiconductor layer can be mentioned.

The first refractive index is the refractive index for infrared rays with a wavelength of 5 μm of the materials forming the first semiconductor lamination portion and the second semiconductor lamination portion of the portion in contact with the first layer, and the wavelength of the forming material of the first layer is 5 μm. is the second refractive index, the ratio of the first refractive index to the second refractive index is preferably 0.8 or more and 1.2 or less. In particular, when the refractive index of the second semiconductor lamination portion is lower than that of the first layer, light propagating through the first layer is efficiently absorbed by the second semiconductor lamination portion, which is preferable in some cases. be.

<Optical path>
In the optical device according to this embodiment, light can be propagated from the light-emitting element to the light-receiving element by providing a light-propagating portion between the light-emitting element and the light-receiving element. This part is called an optical path. This optical path can be formed by processing the first layer.

The light passing through the optical path may be designed to be influenced by the environment. For example, when the cross section of the optical path is finely processed by microfabrication, part of the light leaks out from the optical path into the environment, making it possible to detect and measure various changes in the atmosphere of the environment. For example, if the ambient medium (liquid or gas) absorbs certain wavelengths of light seeping out of the optical path, less light will propagate from the light emitting element to the light receiving element. This phenomenon can be used to measure the concentration of specific substances in the atmosphere of the environment. Further, by lengthening the optical path, the sensitivity to changes in the substance can be increased, and a highly sensitive concentration sensor can be realized.

<Formation technology of each layer>
The first layer, the second layer, the first semiconductor laminate and the second semiconductor laminate are formed by molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD). It can be formed using a method or an adhesion method. The first semiconductor lamination part and the second semiconductor lamination part are preferably formed using the MBE method or the MOCVD method from the viewpoint of achieving high quality. In this case, from the viewpoint of improving the crystallinity of the first semiconductor lamination portion and the second semiconductor lamination portion, the materials for forming the substrate, the first layer, and the second layer may be single crystals. may be Si single crystal, GaAs single crystal or sapphire.

Hereinafter, the optical device according to this embodiment will be described in more detail with reference to the drawings.
(First configuration example)
FIG. 1 shows a cross-sectional configuration example of an optical device 100 according to a first configuration example of the present embodiment.
As shown in FIG. 1, the optical device 100 according to the first configuration example includes a substrate 2 and a first layer formed on the substrate 2 with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate 2. 31, a light emitting element 41 formed on the first layer 31 and having a first semiconductor lamination portion 411, and a second semiconductor lamination portion 511 formed on the first layer 31 and having a light emitting element and a light receiving element 51 capable of receiving light L emitted from 41 and passing through the first layer 31 . The substrate 2 corresponds to an example of the substrate described above, the first layer 31 corresponds to an example of the first layer described above, the light emitting element 41 corresponds to an example of the light emitting element described above, and the light receiving element 51 corresponds to an example of the light emitting element described above. It corresponds to an example of a light receiving element, the first semiconductor lamination portion 411 corresponds to the above-described first semiconductor lamination portion, and the second semiconductor lamination portion 511 corresponds to the above-mentioned second semiconductor lamination portion.

The first layer 31 , the light emitting element 41 and the light receiving element 51 are formed on the substrate 2 .

The optical device 100 also includes an electrode 11 a formed on the light emitting element 41 , an electrode 11 b formed on the first layer 31 and adjacent to the light emitting element 41 , and an electrode 11 b formed on the light receiving element 51 . and an electrode 12b formed on the first layer 31 and adjacent to the light receiving element 51 . The light emitting element 41 has a mesa shape with a trapezoidal cross section. The electrode 11 a is arranged on the upper surface of the light emitting element 41 . The light receiving element 51 has a mesa shape with a trapezoidal cross section, like the light emitting element 41 . The electrode 12 a is arranged on the upper surface of the light receiving element 51 . The electrodes 11 a and 11 b are used to supply current to the light emitting element 41 . The electrodes 12 a and 12 b are used to extract electrical signals from the light receiving element 51 .

The light emitting element 41 and the light receiving element 51 may have a PN structure or a PIN photodiode structure, or may have a photoconductor structure formed of the same type of semiconductor. When the light-receiving element 51 has a photoconductor structure, it is necessary to apply a bias to the light-receiving element 51 so that the light incident on the light-receiving element 51 does not generate an electromotive force.

The first layer 31 in the first configuration example provides electrical connection between the electrode 11b and the light emitting element 41, electrical connection between the light receiving element 51 and the electrode 12b, and propagation of the light L from the light emitting element 41 to the light receiving element 51. It has three roles. Also, although not shown in FIG. 1, in the case of application to gas/liquid concentration measurement, a part of the first layer may be processed to be elongated or thin in order to increase the measurement sensitivity.

(Second configuration example)
FIG. 2 shows a cross-sectional configuration example of an optical device 200 according to a second configuration example of the present embodiment. Components having the same action and function as those of the optical device 100 according to the first configuration example are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 2, the optical device 200 according to the second configuration example includes a substrate 2 and a first layer formed on the substrate 2 with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate 2. 32, a light emitting element 42 formed on the first layer 32 and having a first semiconductor lamination portion 421, and a light emitting element 42 formed on the first layer 32 and having a second semiconductor lamination portion 521; and a light receiving element 52 capable of receiving light L emitted from 42 and passing through the first layer 32 . The first layer 32 corresponds to an example of the above-described first layer, the light-emitting element 42 corresponds to an example of the above-described light-emitting element, the light-receiving element 52 corresponds to an example of the above-described light-receiving element, and the first semiconductor The laminated portion 421 corresponds to the above-described first semiconductor laminated portion, and the second semiconductor laminated portion 521 corresponds to the above-described second semiconductor laminated portion.

The light emitting element 42 in the second configuration example is different in shape from the light emitting element 41 in the first configuration example. The light emitting element 42 has a stepped mesa shape. The light emitting element 42 has two upper surfaces with different heights with respect to the first layer 32 . Of these two upper surfaces, the electrode 11a is arranged on the upper surface higher than the first layer 32, and the electrode 11b is arranged on the upper surface lower than the first layer 32. are placed.

Electrode 11 b is formed without direct contact with first layer 32 . In the second configuration example, the electrodes 11 a and 11 b electrically connected to the light emitting element 42 are formed only on the light emitting element 42 .

The light receiving element 52 in the second configuration example is different in shape from the light receiving element 51 in the first configuration example. The light receiving element 52 has a stepped mesa shape. The light receiving element 52 has two upper surfaces having different heights with respect to the first layer 32 . Of these two upper surfaces, the electrode 12a is arranged on the upper surface higher than the first layer 32, and the electrode 12b is arranged on the upper surface lower than the first layer 32. are placed. Therefore, the electrode 12b is formed without direct contact with the first layer 32. As shown in FIG. In the second configuration example, the electrodes 12 a and 12 b electrically connected to the light receiving element 52 are formed only on the light receiving element 52 .

In the second configuration example, an electrode 11b is formed on the light emitting element 42 and an electrode 12b is formed on the light receiving element 52. FIG. Therefore, unlike the first layer 31 in the first configuration example, the first layer 32 in the second configuration example provides electrical connection between the electrode 11b and the light emitting element 42 and between the light receiving element 52 and the electrode 12b. Does not serve as an electrical connection. The first layer 32 has one role of propagating the light L from the light emitting element 42 to the light receiving element 52 .

(Third configuration example)
FIG. 3 shows a cross-sectional configuration example of an optical device 300 according to a third configuration example of the present embodiment. Components having the same action and function as those of the optical device 100 according to the first configuration example are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 3, the optical device 300 according to the third configuration example includes a substrate 2 and a first layer formed on the substrate 2 with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate 2. 33, a light emitting element 41 formed on the first layer 33 and having a first semiconductor lamination portion 411, and a light emitting element 41 formed on the first layer 33 and having a second semiconductor lamination portion 531; and a light receiving element 53 capable of receiving the light L emitted from 41 and passing through the first layer 33 . The first layer 33 corresponds to an example of the first layer described above, the light receiving element 53 corresponds to an example of the light receiving element described above, and the second semiconductor laminate portion 531 corresponds to the second semiconductor laminate portion described above. do.

In the optical device 300 , an LED having a photodiode structure is used as the light emitting element 41 and a photoconductor is used as the light receiving element 53 .

In the light receiving element 53 , current mainly flows in the direction parallel to the surface of the substrate 3 in the second semiconductor lamination portion 531 . The light receiving element 53 is formed on the surface of the first layer 33 formed on the substrate 3 and is formed in a mesa shape having a trapezoidal cross section. The electrodes 12 a and 12 b are arranged on the upper surface of the light receiving element 53 , that is, on the flat surface of the second semiconductor laminated portion 531 and substantially parallel to the first layer 33 . In the optical device 300, when a bias is applied through the electrodes 12a and 12b, the resistance of the light receiving element 53 (more specifically, the second semiconductor laminate 531) changes depending on the intensity of light incident from the first layer 33. . Therefore, the optical device 300 can extract the change in voltage or current due to this bias as a photoelectric conversion signal.

In the third configuration example, the electrode 11 a is formed on the light emitting element 41 , the electrode 11 b is formed on the first layer 33 , and the electrodes 12 a and 12 b are formed on the light receiving element 52 . For this reason, unlike the first layer 32 in the second configuration example, the first layer 33 in the third configuration example has a role of electrical connection between the electrode 11b and the light emitting device 41, but does not function as the light receiving device 53. It does not have a role of electrical connection with the electrode 12b. Therefore, the first layer 33 has two roles: electrical connection between the electrode 11 b and the light emitting element 41 and propagation of the light L from the light emitting element 42 to the light receiving element 52 .

(Fourth configuration example)
FIG. 4 shows a cross-sectional configuration example of an optical device 400 according to a fourth configuration example of the present embodiment. Components having the same action and function as those of the optical device 200 according to the second configuration example are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 4, the optical device 400 according to the fourth configuration example includes a substrate 2 and a first layer formed on the substrate 2 with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate 2. 32, a light emitting element 42 formed on the first layer 32 and having a first semiconductor lamination portion 421, and a light emitting element 42 formed on the first layer 32 and having a second semiconductor lamination portion 521; and a light receiving element 52 capable of receiving light L emitted from 42 and passing through the first layer 32 . Furthermore, the optical device 400 comprises a second layer 7 having a refractive index different from that of the first layer 32 between the substrate 2 and the first layer 32 . The second layer corresponds to an example of the second layer described above.

In the optical device 400 , the second layer 7 is formed on the substrate 2 and the first layer 32 is formed on the second layer 7 . The substrate 2, the second layer 7 and the first layer 32 may be composed of SOI substrates. In this case, the substrate 2 is composed of a silicon substrate, the second layer 7 is composed of an insulating layer, and the first layer 32 is composed of a semiconductor layer.

The second layer 7 has the role of reflecting light L passing through the first layer 32 . If the second layer 7 has a lower refractive index for light with a wavelength of 1 μm to 12 μm than the first layer 32 , the light L incident on the first layer 32 from the light emitting element 42 is confined in the first layer 32 . In some cases, this is preferable because the light propagation loss in the first layer 32 is reduced.

Also, the second layer 7 may have a multi-layer structure instead of a single-layer structure.

The first layer, the light-emitting element and the light-receiving element provided above the second layer 7 are not limited to the first layer 32, the light-emitting element 42 and the light-receiving element 52 in the second configuration example. It may be one layer 31, the light emitting element 41 and the light receiving element 51, or the first layer 33, the light emitting element 41 and the light receiving element 53 in the third configuration example.

(Fifth configuration example)
FIG. 5 shows a specific configuration example of a light-emitting element and a light-receiving element provided in the optical device according to this embodiment. The first semiconductor lamination part of the light emitting element and the second semiconductor lamination part of the light receiving element may be made of the same material and have the same lamination structure. In the fifth configuration example, a configuration example of the light-emitting element and the light-receiving element when the first semiconductor lamination portion and the second semiconductor lamination portion have the same lamination structure will be described. In the fifth configuration example, the light-emitting element and the light-receiving element are collectively referred to as "photoelectric conversion element".

As shown in FIG. 5, the optical device includes a photoelectric conversion element 40 in which semiconductor layers having different materials and/or compositions and different dopants are stacked. The photoelectric conversion element 40 has a semiconductor lamination portion 21 having a PIN structure. The semiconductor laminated portion 21 corresponds to the first semiconductor laminated portion when the photoelectric conversion element 40 is a light emitting element, and corresponds to the second semiconductor laminated portion when the photoelectric conversion element 40 is a light receiving element. The semiconductor lamination portion 21 is formed in a mesa shape having steps. The semiconductor lamination portion 21 is formed on the n-layer 219 formed on the first layer 32 of the composite substrate (not shown), the n-barrier layer 217 formed on the n-layer 219 , and the n-barrier layer 217 . an active layer 215 , a p-barrier layer 213 formed on the active layer 215 , and a p-layer 211 formed on the p-barrier layer 213 .

The active layer 215 is a layer that absorbs or emits infrared rays. When the photoelectric conversion element 40 is, for example, a light receiving element, the active layer 215 functions as a layer that absorbs infrared rays. On the other hand, when the photoelectric conversion element 40 is, for example, a light-emitting element, the active layer 215 functions as a layer that emits infrared rays. The active layer 215 can change the emission wavelength band and the light reception wavelength band by changing the bandgap. As an example, when the active layer 215 is made of InSb, the peak wavelengths of the light emission wavelength band and the light reception wavelength band are around 5 μm.

The n-barrier layer 217 and the p-barrier layer 213 may be set to have a bandgap larger than that of the active layer 215 . Then, when the photoelectric conversion element 40 is operated as a light receiving element, a high S/N ratio can be realized due to the effect of preventing diffusion of carriers, and when the photoelectric conversion element 40 is operated as a light emitting element, an effect due to carrier confinement can be realized. Luminous efficiency can be improved. Also, the p barrier layer 213 and the n barrier layer 217 may have different band offsets. In general, the band offsets of the p barrier layer 213 and the n barrier layer 217 affect the luminous efficiency (when the photoelectric conversion element 40 operates as a light emitting element) and the light receiving efficiency (when the photoelectric conversion element 40 operates as a light receiving element) of the semiconductor lamination portion 21. operation) is set by the material forming the active layer 215 so as to be optimal.

The p-layer 211 is a layer made of a p-type semiconductor. The p-layer 211 operates as a hole extraction layer when the photoelectric conversion element 40 operates as a light receiving section. On the other hand, the p-layer 211 is used as a hole injection layer when the photoelectric conversion element 40 operates as a light emitting section. The n-layer 219 is made of an n-type semiconductor. The n-layer 219 corresponds to an example of the portion of the first semiconductor lamination portion in contact with the first layer when the photoelectric conversion element 40 is a light-emitting element, and corresponds to the first layer when the photoelectric conversion element 40 is a light-receiving element. It corresponds to an example of the portion of the second semiconductor lamination portion in contact with the layer. The n layer 219 operates as an electron extraction layer when the photoelectric conversion element 40 operates as a light receiving element. On the other hand, the n-layer 219 is used as an electron injection layer when the photoelectric conversion element 40 operates as a light-emitting element.

The photoelectric conversion element 40 has an insulating layer (passivation layer) 23 provided to partially cover the semiconductor lamination portion 21 . The insulating layer 23 has a role of ensuring insulation of the side surface of the photoelectric conversion element 40 , that is, the side surface of the semiconductor lamination portion 21 . Specific materials that can be used to form insulating layer 23 include, for example, silicon nitride, silicon oxide, and alumina.

The photoelectric conversion element 40 has a metal layer 25 . A portion of metal layer 25 is embedded in contact hole 251 formed in a portion of insulating layer 23 on p layer 211 and exposing at least a portion of p layer 211 . This connects the metal layer 25 to the p-layer 211 . Another part of the metal layer 25 is embedded in a contact hole 252 formed in a part of the insulating layer 23 on the n-layer 219 and exposing a part of the n-layer 219 . Metal layer 25 is thereby connected to n layer 219 . Thus, metal layer 25 is provided to connect n layer 219 and p layer 211 . However, the metal layer 25 does not connect the n-layer 219 and the p-layer 211 that constitute one semiconductor lamination portion 21 . The metal layer 25 connects the n-layer 219 (or p-layer 211) forming one semiconductor lamination portion 21 and the p-layer 211 (or n-layer 219) forming another semiconductor lamination portion 21, and It serves at least one purpose for electrical connection with the outside world (devices or circuits other than optical devices).

If p-layer 211 and n-layer 219 are layers formed of at least one of indium (In) and antimony (Sb), metal layer 25 may be formed of gold (Au). Further, when metal layer 25 is made of Au, a titanium (Ti) layer may be provided at the interface between metal layer 25 and p-layer 211 and n-layer 219 . In this case, the adhesion between the p-layer 211 and the n-layer 219 and the metal layer 25 can be improved, and a highly reliable infrared device can be realized.

The optical density measuring device according to the present embodiment includes the first to fourth configuration examples of the present embodiment, in which at least a part of the first layer is provided so as to be able to come into contact with the gas to be measured or the liquid to be measured in the environment. The optical devices 100, 200, 300, and 400 according to the configuration example, the power supply circuit connected to the electrodes 11a and 11b of the optical devices 100, 200, 300, and 400 for applying voltage to the light emitting elements 41 and 42, and the electrode 12a. , 12b and output from the light-receiving elements 51, 52, and 53 to detect the concentration of the measured gas or liquid, and a control circuit for controlling these power supply circuits and detection circuits. at least

Further, in the optical density measuring device according to the present embodiment, at least a part of the first layer is provided so as to be able to come into contact with the gas to be measured or the liquid to be measured in the environment. an optical device, a power supply circuit connected to the metal layer 25 of the photoelectric conversion element 40 as the light emitting element of the optical device for applying a voltage to the photoelectric conversion element 40, and a light receiving element connected to the metal layer 25. It comprises at least a detection circuit that detects the concentration of the gas or liquid to be measured using an electrical signal output from the photoelectric conversion element 40, and a control circuit that controls the power supply circuit and the detection circuit.

The optical device according to the example of this embodiment has the same shape as the optical device according to the fifth configuration example. Therefore, the optical device according to this embodiment will be described with reference to FIG. An optical device according to an example of the present embodiment includes an SOI substrate having an insulating layer (that is, a second layer (not shown)) made of SiO ₂ as a substrate, and a photoelectric conversion element 40 formed on the SOI substrate. I have. The substrate diameter of this SOI substrate is 100 mm, the thickness of the first layer 32 is 15 μm, the thickness of the second layer is 5 μm, and the thickness of the third layer (not shown) is 600 μm. Further, the photoelectric conversion element 40 includes an n-layer 219 having a thickness of 1 μm formed of InSb doped with 7×10 ¹⁸ cm ⁻³ of tin (Sn), and an AlInSb layer doped with 3×10 ¹⁸ cm ⁻³ of tin (Sn). an n-barrier layer 217 with a thickness of 0.02 μm made of Zn, an active layer 215 with a thickness of 2 μm made of InSb doped with zinc (Zn) at 6×10 ¹⁶ cm ⁻³ , and zinc (Zn) with a thickness of 3×10 It has a p-barrier layer 213 with a thickness of 0.02 μm made of AlInSb doped with ¹⁸ cm ⁻³ and a p-layer 211 with a thickness of 0.5 μm made of InSb doped with Zn at 2×10 ¹⁸ cm ⁻³ . ing. The n-layer 219, n-barrier layer 217, active layer 215, p-barrier layer 213 and p-layer 211 are deposited by molecular beam epitaxial growth (MBE). In order to form the photoelectric conversion element 40 in a stepped mesa shape, selective wet etching was performed using HCl+H ₂ O ₂ +H ₂ O). Thereafter, an insulating layer 23 was formed from silicon nitride using a P-CVD (Plasma Assisted Chemical Vapor Deposition) apparatus to fabricate an optical device. Further, a metal layer 25 having a structure of Au/Pt/Ti (Ti, Pt and Au are laminated in this order) was formed using an electron beam vapor deposition apparatus.

By providing an optical path (that is, the _first layer 32) in which the light-emitting element 42 and the light-receiving element 52 using the above structure are configured as shown in FIG. It was confirmed that the output signal of the element 52 changed.

100, 200, 300, 400 Optical Device 2 Substrate 31, 32, 33 First Layer 41, 42 Light Emitting Element 51, 52, 53 Light Receiving Element 7 Second Layer 11a, 11b, 12a, 12b Electrode 211 p Layer 213 p barrier layer 215 active layer 217 n-barrier layer 219 n-layers 251, 252 contact holes 411, 421 first semiconductor lamination 511, 521, 531 second semiconductor lamination L light

Claims (8)

An optical concentration measuring device for measuring the concentration of a gas or liquid to be measured,
a substrate;
a first layer directly formed on the substrate with a thickness of 0.1 μm or more and 100 μm or less and having a higher refractive index than the substrate;
a light emitting element formed on the first layer and having a first semiconductor laminate;
a light-receiving element formed on the first layer and having a second semiconductor lamination portion and capable of receiving light emitted from the light-emitting element and passing through the first layer;
comprising an optical device comprising
The first layer is narrower or thinner than other portions of the first layer between the light emitting element and the light receiving element, and can propagate light and leak part of the light into the environment. having an optical path formed as thick as possible,
At least the optical path of the first layer is provided so as to be in contact with the gas to be measured or the liquid to be measured.
Optical Densitometer . An optical concentration measuring device for measuring the concentration of a gas or liquid to be measured,
a substrate;
a first layer formed on the substrate with a thickness of 0.1 μm or more and 100 μm or less;
a second layer formed between the substrate and the first layer in direct contact with the substrate and the first layer and having a lower refractive index than the first layer;
a light emitting element formed on the first layer and having a first semiconductor laminate;
a light-receiving element formed on the first layer and having a second semiconductor lamination portion and capable of receiving light emitted from the light-emitting element and passing through the first layer;
comprising an optical device comprising
The first layer is narrower or thinner than other portions of the first layer between the light emitting element and the light receiving element, and can propagate light and leak part of the light into the environment. having an optical path formed as thick as possible,
At least the optical path of the first layer is provided so as to be in contact with the gas to be measured or the liquid to be measured.
Optical Densitometer . 3. The optical density measuring device according to claim 2, wherein the second layer is made of an insulating material having a resistivity of 10 kΩ·cm or more and 1 GΩ·cm or less. The optical density measuring device according to any one of claims 1 to 3, wherein the substrate is made of silicon single crystal, gallium arsenide single crystal, or aluminum oxide single crystal. 5. The material according to any one of claims 1 to 4, wherein the material of the second semiconductor lamination portion in contact with the first layer has a higher refractive index for infrared rays with a wavelength of 5 μm than the material of the first layer. An optical densitometer as described. The optical density measuring device according to any one of claims 1 to 5, wherein the first semiconductor lamination part and the second semiconductor lamination part have at least one of an n-type semiconductor layer and a p-type semiconductor layer. When the first semiconductor lamination portion and the second semiconductor lamination portion have both the n-type semiconductor layer and the p-type semiconductor layer, i between the n-type semiconductor layer and the p-type semiconductor layer. 7. The optical density measuring device of claim 6, further comprising a semiconductor layer. The first semiconductor lamination part and the second semiconductor lamination part are formed of the same material and have the same lamination structure,
The first refractive index is the refractive index for infrared rays with a wavelength of 5 μm of the material of the first semiconductor laminate portion and the second semiconductor laminate portion in the portion in contact with the first layer, and the wavelength of the material of the first layer 1 to 4, 6 or 7, wherein the ratio of the first refractive index to the second refractive index is 0.8 or more and 1.2 or less, where the refractive index for infrared rays of 5 μm is the second refractive index. The optical density measuring device according to any one of 1.

Images