JP4721147B1 - Biological component detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological component detection device capable of detecting a biological component with high sensitivity using an InP-based photodiode in which dark current is reduced without a cooling mechanism and light receiving sensitivity is expanded to a wavelength of 1.8 μm or more.
A light receiving layer has a multiple quantum well structure of a III-V group semiconductor, and a pn junction is formed by selectively diffusing an impurity element in the light receiving layer, and an impurity concentration in the light receiving layer is 5 × 10 ¹⁶ / cm ³ or less, the n-type impurity concentration before diffusion of the diffusion concentration distribution adjustment layer is 2 × 10 ¹⁵ / cm ³ or less, and the thickness range on the light receiving layer side has a low impurity concentration range, The biological component detection device receives light of at least one wavelength included in an absorption band of biological components having a wavelength of 3 μm or less and performs an inspection.
[Selection] Figure 3

Description

  The present invention relates to a biological component detection apparatus using a semiconductor light receiving element having light receiving sensitivity with respect to light in the near infrared region.

  Since biological components such as human blood and body fat have absorption bands in the near infrared region, near infrared spectroscopy has attracted attention as a non-invasive analysis method, and research and practical application are rapidly progressing. In particular, in recent years, attention has been focused on diabetes, obesity, etc., and the absorption spectrum bands of glucose, cholesterol, lipids, etc., which are the main components in blood sugar, are in the near infrared region. ing. In analysis by near-infrared spectroscopy, the output signal includes necessary information and large noise due to the light receiving element. For this reason, a spectroscopic method or chemometrics is used as an important method in order to extract necessary information about the output signal without relying entirely on the performance improvement of the sensor (light receiving element).

The sensors (light receiving elements) are roughly classified into an electron tube type and a solid state photodiode (PD) in the near infrared region. Among these, since the PD is small and can easily be highly integrated such as a one-dimensional array and a two-dimensional array, a lot of research and development has been performed (Non-Patent Document 1). The present invention is directed to a detection apparatus for a biological component using PD. Currently, the following PDs or PD arrays are used.
(1) PD having light receiving sensitivity up to the infrared region and light receiving sensitivity in the near infrared region, or an array thereof. Examples of such photodiodes include germanium (Ge) -based PD, lead sulfide (PbS) -based PD, HgCdTe-based PD, or a one-dimensional array and a two-dimensional array thereof.
(2) An InP-based PD having a light receiving sensitivity at a wavelength of 1.7 μm or less in the near infrared region, an InGaAs-based PD falling within the category of the InP-based PD, or an array thereof. Here, the InP-based PD refers to a PD including a light-receiving layer of a III-V group compound semiconductor formed on an InP substrate, and includes an InGaAs-based PD.

  Among the above photodiodes, (1) is often cooled to suppress noise, and for example, many are cooled and operated at a liquid nitrogen temperature (77 K) or a Peltier element. For this reason, the apparatus becomes large and the apparatus cost increases. Although it can be used even at room temperature, it has a problem that the dark current is large and the detection ability is inferior in the wavelength range of 2.5 μm or less. (2) On the other hand, the disadvantages of InP-based PD are: (I) InGaAs lattice-matched to InP has a low dark current, but the light receiving sensitivity is limited to a wavelength region of 1.7 μm or less in the near infrared region, and ( II) In extended-InGaAs in which the wavelength range where light can be received is expanded to 2.6 μm, dark current needs to be greatly cooled. Therefore, in InP-based PD, light of 2.0 μm or more, which is important in the inspection of biological components, cannot be used or needs to be cooled when used.

In living body component detection using near-infrared light, there are overwhelmingly many blood glucose levels (glucose, glucose, etc.) that are directly related to diabetes (Patent Documents 1 to 4). Detection (Patent Document 5) is performed. Moreover, in the beauty-related, the measurement by the near-infrared light of the collagen related to the wrinkle of skin is made (patent document 6). In addition, a proposal has been made to measure infrared rays in relation to the distribution of collagen and the like during corneal surgery (Patent Document 7).
In the detection of these biological components, a single element or an array type such as InGaAs, PbS, Ge, HgCdTe, or extended-InGaAs provided with a multi-step buffer layer is used for a near infrared light spectroscopic device. The light receiving wavelength range is 1 μm to 1.8 μm in the range common to all the biological component detection devices. However, it is recognized that the upper limit is about 2.0 μm or 2.5 μm.

As described above, InGaAs has a problem of increasing the light receiving sensitivity to the near-infrared long wavelength side. In order to improve this, the following measures have been proposed.
(K1) The In composition of the InGaAs light receiving layer is increased, and the lattice mismatch with the InP substrate is absorbed by the step buffer layer inserted between them and the In composition changed stepwise (Patent Document 8).
(K2) N is contained in the InGaAs light receiving layer to form a GaInNAs light receiving layer (Patent Document 9). Lattice matching with the InP substrate is satisfied by containing a large amount of N.
(K3) The wavelength of the light receiving region is increased by a type II multiple quantum well structure of GaAsSb and InGaAs (Non-patent Document 2). The lattice matching with the InP substrate is satisfied.
(K4) Two-dimensional arraying is realized by forming wet etching of element isolation grooves between light receiving elements (pixels) (Patent Document 10).
Masao Nakayama “Technology Trends of Infrared Detectors” Sensor Technology, March 1989 (Vol.9, No.3), p.61-64 R. Sidhu, "A Long-Wavelength Photodiode on InP Using Lattice-Matched GaInAs-GaAsSb Type-II Quantum Wells, IEEE Photonics Technology Letters, Vol. 17, No. 12 (2005), pp. 271-2717 JP 2002-065645 A Japanese Patent Laid-Open No. 11-216131 JP-T-2005-519682 Japanese Patent Laid-Open No. 11-128209 JP 2001-95806 A JP 2005-83901 A JP-A-10-118108 JP 2002-373999 A JP-A-9-219563 JP 2001-144278 A

In the above-described biological component detection device, a mechanism using near infrared light up to a maximum of 2.5 μm has been proposed (Patent Documents 1 to 6). If the light receiving sensitivity is good, it is preferable that the upper limit of the wavelength is large because more information can be obtained. However, in order to receive light in a range exceeding the wavelength of 1.7 μm, as described above, a light receiving element using PbS, HgCdTe, or the like has a problem of high dark current, low detection capability, and high detection resolution. Moreover, if it is cooled and used in order to enhance the detection capability, the biological component detection device becomes large and power consumption increases.
An InGaAs light receiving element lattice-matched to an InP substrate is excellent in detection capability but has a sensitivity of a wavelength of 1.7 μm or less, and is unsuitable for detection of a biological component having a larger absorption spectrum in a longer wavelength region. In particular, as in the case of a living body, when many biological components are combined to form a biological tissue, a single biological component to be detected is synthesized using two or more absorption bands derived from the biological component. It is desirable to improve the resolution. However, in the detection of biological components using two or more absorption bands, a sensitivity wavelength range of 1.7 μm or less is extremely insufficient.

On the other hand, as shown in the above (K1) to (K4), there are several candidates for the light receiving element and the light receiving element array that do not require cooling and have light receiving sensitivity on the long wavelength side in the near infrared region. However, each has the following problems.
(K1): Since the InP substrate and the light receiving layer are not completely lattice matched, the dark current due to the high lattice defect density is very high. For this reason, a sufficiently high dynamic range (S / N ratio) cannot be obtained, resulting in high noise. For this reason, dark spots (image omissions) increase.
In addition, in order to realize lattice matching for the window layer that forms the top layer of the laminate, InP cannot be used, and it is necessary to use an InAsP window layer. For this reason, depending on the biological component, the sensitivity on the short wavelength side from the near infrared region where an important absorption band is located deteriorates.
(K2): It is very difficult to obtain GaInNAs having a good crystal when N is set to about 10 at% in order to make the band gap longer wavelength while lattice matching with InP. Further, it is almost impossible to obtain GaInNAs with a thickness of about 2 μm in order to sufficiently increase the light receiving sensitivity. In short, a clear image cannot be obtained.
(K3): When impurities are introduced into the light-receiving layer having a multiple quantum well structure by a normal method, the crystallinity of the multiple quantum well structure is impaired. For this reason, the manufacturing yield decreases, the product cost increases, and it is difficult to obtain a good crystallinity. Therefore, although the light receiving wavelength range can be increased to about 2.5 μm, a clear image cannot be obtained.
(K4): In order to separate the elements by wet etching to form an array, the etchant needs to wrap around the groove sufficiently and uniformly. However, the etchant is sufficiently deep in the groove and does not wrap around uniformly and is difficult to control. For this reason, a manufacturing yield becomes low.
On the other hand, in the dry etching, damage to the light receiving element occurs. In particular, in the case of a device that receives light diffracted according to the wavelength, such as a biological component detection device, the above-described damage cannot be allowed.

If a near-infrared spectroscopy with high sensitivity can be easily performed using a photodiode that suppresses dark current without a cooling mechanism, useful information about biological components can be obtained on a daily basis. It can promote the development of many fields related to management and disease healing.
The present invention provides a biological component detection apparatus that can detect biological components with high sensitivity using an InP-based photodiode in which dark current is reduced without a cooling mechanism and light receiving sensitivity is increased to a wavelength of 1.8 μm or more. For the purpose.

The biological component detection device of the present invention is a device for detecting a biological component using light in the near infrared region. This device includes a light-receiving element made of a III-V group semiconductor that receives light in the near-infrared region, the light-receiving element has a light-receiving layer having a multiple quantum well structure formed on an InP substrate, and the band gap wavelength of the light-receiving layer Is 1.8 μm or more and 3 μm or less, and includes a diffusion concentration distribution adjusting layer of a III-V compound semiconductor in contact with the surface of the light receiving layer opposite to the InP substrate, and the band gap energy of the diffusion concentration distribution adjusting layer is It is smaller than InP. In the light receiving element, a pn junction is formed by selective diffusion of the impurity element that reaches the light receiving layer through the diffusion concentration distribution adjusting layer, and the concentration of the impurity element in the light receiving layer is 5 × 10 ¹⁶ / cm ³ or less. The n-type impurity concentration before diffusion of the adjustment layer is 2 × 10 ¹⁵ / cm ³ or less, and the diffusion concentration distribution adjustment layer has a low impurity concentration range in the thickness range on the light receiving layer side. Then, the transmitted light or reflected light from the living body is detected by receiving light of at least one wavelength of 3 μm or less with a light receiving element.

With the above configuration, the multiple quantum well structure having a band gap energy corresponding to the near infrared region is not destroyed by reducing the impurity concentration to 5 × 10 ¹⁶ cm ⁻³ or less, that is, the crystallinity Can be formed without impairing. Then, the impurities for forming the pn junction of the light receiving element are selectively diffused, that is, are introduced so as to be limited in a planar manner from the periphery to the inside and separated into individual light receiving elements. For this reason, it is easy to form each light receiving element with high accuracy, and it is not necessary to provide an element isolation groove, so that a light receiving element with a low dark current can be formed. For this reason, it is possible to receive light with high sensitivity without cooling at a wavelength of 3 μm or less. Since there are a number of absorption bands of biological components (molecules) at a wavelength of 0.9 μm to 3 μm, the biological component detection device can detect the plurality of absorption bands simultaneously. Thereby, the detection accuracy can be improved.

By making the band gap energy of the diffusion concentration distribution adjustment layer smaller than InP, the electrical resistance can be kept low even if the impurity concentration in the thickness range on the light receiving layer side of the diffusion concentration distribution adjustment layer is lowered, and therefore the response It can contribute to prevention of speed reduction. More specifically, the reason why the band gap energy of the diffusion concentration distribution adjusting layer is made smaller than the band gap energy of the InP substrate is as follows.
(1) When a near-infrared light-receiving layer is formed of a III-V group compound semiconductor, band gap energy larger than the band gap energy of the light-receiving layer may be used for the window layer. In view of this, the same material as the semiconductor substrate is often used. It is assumed that the band gap energy of the diffusion concentration distribution adjusting layer is smaller than the band gap energy of the window layer and larger than the band gap energy of the light receiving layer. If the band gap energy of the light receiving layer is smaller, the diffusion concentration distribution adjusting layer absorbs the target light and reduces the light receiving sensitivity of the light receiving layer when the structure having the epitaxial layer surface as the incident surface is adopted. is there.
(2) By using a material having a smaller band gap energy than a material having a large band gap energy normally used for the window layer, even if the impurity concentration is lowered, the degree of increase in electric resistance or the degree of decrease in electric conductivity is reduced. Can be small. As a result, it is possible to suppress a decrease in response speed in the voltage application state as described above.

  Here, “detection” refers to preparing a calibration curve of a predetermined component (relationship between the concentration of the predetermined component and the intensity or absorbance of light at that wavelength) in advance, and obtaining the concentration or content rate of the predetermined component. It is also possible to use a method that does not use such a calibration curve. The above pn junction should be interpreted broadly as follows. In the light receiving layer, an impurity region (referred to as an i region) in which the impurity concentration in a region on the side opposite to the side where the impurity element is introduced by selective diffusion is low enough to be regarded as an intrinsic semiconductor is referred to as the impurity introduced by diffusion. It also includes a bond formed between the region and the i region. That is, the pn junction may be a pi junction or an ni junction, and further includes a case where the p concentration or the n concentration in the pi junction or ni junction is very low.

In the diffusion concentration distribution adjusting layer, the concentration of the impurity element is 1 × 10 ¹⁸ / cm ³ or more on the surface opposite to the surface in contact with the light receiving layer, and 2 × 10 ¹⁶ / cm ³ on the light receiving layer side. And a region between the two regions and having a thickness smaller than that of the two regions and an impurity element concentration of greater than 2 × 10 ¹⁶ / cm ^{3 and} less than 1 × 10 ¹⁸ / cm ^3. Can be. As a result, it is possible to ensure good crystallinity of the multiple quantum well structure while suppressing the interface resistance of the electrode located on the top side of the surface or enabling ohmic contact. As described above, the problem of an increase in electrical resistance or a decrease in electrical conductivity due to a low impurity concentration in the portion in the diffusion concentration distribution adjusting layer is that the band gap energy of the diffusion concentration distribution adjusting layer is set to be higher than that corresponding to InP. It can be reduced by making it smaller.

  The light receiving layer may have a type II quantum well structure. Thus, when electromagnetic waves are absorbed, a transition from a high valence band layer to a low conductive band layer is possible, and it is easy to obtain light receiving sensitivity to light in a longer wavelength region.

  The light receiving layer may have a (InGaAs / GaAsSb) multiple quantum well structure or a (GaInNAs (P, Sb) / GaAsSb) multiple quantum well structure. Here, (GaInNAs (P, Sb) / GaAsSb) means (GaInNAsP / GaAsSb), (GaInNAsSb / GaAsSb), (GaInNAsPSb / GaAsSb), or (GaInNAs / GaAsSb). As a result, it is possible to easily obtain a light receiving element having excellent crystallinity and low dark current by using the materials and techniques accumulated so far.

  The above InP substrate can be an off-angle substrate tilted by 5 ° to 20 ° from (100) in the [111] direction or the [11-1] direction. As a result, it is possible to obtain a stacked body including a light-receiving layer having a multiple quantum well structure with a small defect density and excellent crystallinity. As a result, it is possible to obtain a light receiving element array and a detection device in which dark current is suppressed and there are few dark spots.

  The impurity element can be zinc (Zn), and the diffusion concentration distribution adjusting layer can be formed of InGaAs. Thereby, the diffusion concentration distribution adjusting layer can be formed of a material that is less dependent on the impurity concentration of the electric resistance and does not increase the electric resistance so much even if the impurity concentration is low. Suppressing the increase in electrical resistance prevents response speed deterioration. Moreover, the impurity zinc has an abundant track record of selective diffusion so far, and a diffusion region can be formed with high accuracy. For this reason, in the diffusion concentration distribution adjusting layer, the high concentration impurity on the upper side on the diffusion introduction side is set to a lower concentration on the lower side on the light receiving layer side, and the electric resistance on the lower side can be prevented from being increased. For this reason, it is possible to prevent a region having a high impurity concentration from being formed in the light receiving layer having the quantum well structure. As a result, a light-receiving element having a quantum well structure with good crystallinity can be obtained without deteriorating responsiveness. The band gap energy of InGaAs is 0.75 eV.

  An InP window layer can be provided on the diffusion concentration distribution adjusting layer. The formation of the window layer by InP does not impair the crystallinity of the internal semiconductor multilayer structure. Therefore, when a structure having the epitaxial layer as the incident surface side is adopted, absorption of near infrared light on the incident side from the light receiving layer, etc. This effectively works to suppress dark current. In addition, the technology for forming a passivation film on the crystal surface of InP is more technically established than the technology for forming a passivation film on the surface of InGaAs, for example, when it is formed on another crystal surface. Current leakage can be easily suppressed.

  Lattice matching degree (| Δa / a |: where a is a lattice constant between any of the InP substrate, each layer constituting the quantum well structure of the light receiving layer, the diffusion concentration distribution adjusting layer, and the InP window layer. , Δa can be 0.002 or less. With this configuration, it is possible to obtain a light receiving layer having excellent crystallinity using a commonly available InP substrate. For this reason, in the near-infrared light-receiving element or light-receiving element array having a wavelength of 1.8 μm or more, dark current can be significantly reduced.

  The above-described light receiving element can have a structure in which it is arrayed one-dimensionally or two-dimensionally. The light receiving element array includes a plurality of light receiving elements, a common semiconductor stacked structure, and an impurity element is selectively diffused in the light receiving layer for each light receiving element, and is arranged one-dimensionally or two-dimensionally. According to this configuration, since the light receiving element is formed by each impurity diffusion region, it is not necessary to provide an element isolation groove. Therefore, it is possible to form a light receiving element array that can be easily formed with high accuracy and can reduce the dark current.

  A living body part to be inspected can be irradiated with light from a supercontinuum light source (SC light source) or a light emitting diode (LED) to receive transmitted light or reflected light from the living body part. Usually, a halogen lamp is used as a light source. However, since the halogen lamp generates heat, there is a case where heat and discomfort may be felt by irradiation. On the other hand, since the SC light source and the LED do not generate heat, they are suitable as a measurement light source for living bodies. The living body component detection apparatus of the present invention performs calculations based on the light received by the light receiving element or the light receiving element array, including the case of the SC light source, the LED, and the case of a normal halogen lamp. It is usual to provide a control unit for calculating the concentration of the contained component.

  An imaging device including a two-dimensional array of the light receiving elements is provided, and a distribution image of components contained in a living body to be detected can be formed by the imaging device. Thereby, it is possible to obtain a distribution image of the predetermined component in the object which is easy to understand sensuously.

The living body is irradiated with light in the above wavelength range, the reflected light from the living body or the transmitted light from the living body is received, and glucose, glucose, hemoglobin, cholesterol, albumin, active oxygen contained in the living body, At least one component of fat and collagen can be detected. This makes it easy to know the sugar and cholesterol concentrations in human blood. As a result, it is possible to know the status of diabetic patients and their reserves, which reach several tens of percent of the nation, on a daily basis with high accuracy, and to stop the progress of treatment and disease. In addition, since the component concentration of blood vessels and blood can be easily obtained, it is useful for prevention of adult diseases such as cerebral infarction and myocardial infarction. Objective data can be easily obtained for symptoms such as metabolic syndrome, which can be said to be a pre-stage state of the above-mentioned diseases, and measures can be easily taken.
Furthermore, the lack of collagen related to the generation of wrinkles and the like of the corner of the eye can be easily confirmed as a distribution image by a near-infrared imaging device. It can be used to detect many skin-related components including collagen.

  A light-splitting unit that separates the light and is located on the light irradiation side of the detection part or after the detection part when viewed from the irradiation side, and a plurality of light-receiving elements or light-receiving element arrays that are positioned according to the split wavelength And a control unit that calculates based on a result of light received by the light receiving element or the light receiving element array and calculates a component concentration of the living body. As a result, simultaneous reception of multiple wavelengths can be performed quickly and accurately. The spectroscopic section is preferably formed of a diffraction grating or the like. Further, the control unit includes a storage unit, an input unit from the outside, and the like, and a calibration curve for the target wavelength may be input and stored in advance.

  According to the biological component detection apparatus of the present invention, it is possible to detect biological components with high sensitivity using an InP-based light receiving element that reduces dark current without a cooling mechanism and expands the light receiving sensitivity to a wavelength of 1.8 μm or more. .

(Embodiment 1-Structure of semiconductor light receiving element array)
FIG. 1 is a cross-sectional view showing a light receiving element 10 according to an embodiment of the present invention. According to FIG. 1, the light receiving element 10 has a group III-V semiconductor laminated structure (epitaxial wafer) having the following configuration on the InP substrate 1.
(InP substrate 1 / InP buffer layer 2 / Light-receiving layer 3 / InGaAs diffusion concentration distribution adjusting layer 4 / InP window layer 5 having a multiple quantum well structure of InGaAs or GaInNAs and GaAsSb)
In the p-type region 6 located so as to reach the light-receiving layer 3 having the multiple quantum well structure from the InP window layer 5, the p-type impurity Zn is selectively diffused from the opening of the selective diffusion mask pattern 36 of the SiN film. Formed with. The fact that diffusion is introduced into the periphery of the light receiving element 10 in a limited manner in a planar manner can be achieved by diffusion using the selective diffusion mask pattern 36 of the SiN film.

  A p-side electrode 11 made of AuZn is provided in the p-type region 6, and an n-side electrode 12 made of AuGeNi is provided in ohmic contact with the back surface of the InP substrate 1. In this case, the InP substrate 1 is doped with n-type impurities to ensure a predetermined level of conductivity. An antireflection film 35 made of SiON is provided on the back surface of the InP substrate 1 so that light can enter from the back surface side of the InP substrate.

In the light-receiving layer 3 having a multiple quantum well structure, a pn junction is formed at a position corresponding to the boundary front of the p-type region 6, and a reverse bias voltage is applied between the p-side electrode 11 and the n-side electrode 12. As a result, a depletion layer is formed more widely on the side where the n-type impurity concentration is low (n-type impurity background). The background in the light-receiving layer 3 having the multiple quantum well structure is about 5 × 10 ¹⁵ / cm ³ or less in terms of n-type impurity concentration (carrier concentration). The position 15 of the pn junction is determined by the intersection of the background (n-type carrier concentration) of the light-receiving layer 3 of the multiple quantum well and the concentration profile of the p-type impurity Zn. That is, the position shown in FIG.

In the diffusion concentration distribution adjusting layer 4, the concentration of the p-type impurity selectively diffused from the surface 5 a of the InP window layer 5 sharply decreases from the high concentration region on the InP window layer side to the light receiving layer side. Therefore, in the light receiving layer 3, an impurity concentration of 5 × 10 ¹⁶ / cm ³ or less can be easily realized. In FIG. 2, the lower Zn concentration in the light receiving layer 3 is realized to be about 1 × 10 ¹⁶ / cm ³ or lower.

  Since the light receiving element 10 targeted by the present invention seeks to have light receiving sensitivity from the near infrared region to the long wavelength side, a material having a band gap energy larger than the band gap energy of the light receiving layer 3 is used for the window layer. It is preferable to use it. For this reason, InP, which is a material having a band gap energy larger than that of the light receiving layer and having a good lattice matching, is usually used for the window layer. InAlAs having substantially the same band gap energy as InP may be used.

(Points of light receiving element array of this embodiment)
The feature of this embodiment is that it is composed of the following elements.
1. In the multi-quantum well structure, when impurities are introduced at a high concentration by selective diffusion, the structure is destroyed, so it is necessary to suppress the introduction of impurities by selective diffusion. Usually, the concentration of the p-type impurity to be diffused and introduced is required to be 5 × 10 ¹⁶ / cm ³ or less.

2. A diffusion concentration distribution adjusting layer 4 made of InGaAs is provided on the light receiving layer 3 in order to stably obtain the low p-type impurity concentration with good reproducibility in actual production. In the diffusion concentration distribution adjusting layer 4, when the thickness range on the light receiving layer side becomes a low impurity concentration as described above, the electrical conductivity in the low impurity concentration range decreases or the electrical resistance increases. When the electrical conductivity in the low impurity concentration range in the diffusion concentration distribution adjusting layer 4 is lowered, the responsiveness is lowered and, for example, a good moving image cannot be obtained. However, when the diffusion concentration distribution adjusting layer is formed of a material having a band gap energy smaller than the band gap energy equivalent to InP, specifically, a group III-V semiconductor material having a band gap energy of less than 1.34 eV, Even at low concentrations, the electrical conductivity is not significantly reduced. Examples of the III-V group semiconductor material that satisfies the requirements of the diffusion concentration distribution adjusting layer include InGaAs.
The reason why the impurity concentration of the light receiving layer is 5 × 10 ¹⁶ / cm ³ or less will be described in more detail. When the Zn concentration in the light receiving layer 3 exceeds 1 × 10 ¹⁷ cm ^{−3 because} the depth of selective diffusion of the p-type impurity (Zn) is increased, the InGaAs that constitutes the quantum well layer in the higher concentration portion. And GaAsSb atoms enter each other and are disturbed, destroying the superlattice structure. The crystal quality of the destroyed portion is lowered, and the device characteristics are deteriorated, such as an increase in dark current. Here, the Zn concentration is usually measured by SIMS analysis (Secondary Ion Mass Spectroscopy), but it is difficult to analyze the concentration of 10 ¹⁷ cm ⁻³ or 10 ¹⁶ cm ^−3. Large measurement error occurs. The detailed description above is a discussion of the Zn concentration with double or half accuracy, but it comes from this measurement accuracy. Therefore, for example, it is difficult to discuss the difference between 5 × 10 ¹⁶ / cm ³ and 6 × 10 ¹⁶ / cm ^{3 in} terms of measurement accuracy, and there is no great meaning.

  When a material having a narrow band gap energy is used for the diffusion concentration distribution adjusting layer, an increase in electrical resistance can be suppressed even if the impurity concentration is low. Since the response speed to reverse bias voltage application or the like is considered to be determined by the CR time constant due to the capacitance and electric resistance, the response speed can be shortened by suppressing the increase in electric resistance R as described above.

3. In this embodiment, the multiple quantum well structure is of type II. In the type I quantum well structure, in the case of a light receiving element that has a light receiving sensitivity in the near infrared region while sandwiching a semiconductor layer having a small band gap energy between semiconductor layers having a large band gap energy, a semiconductor layer having a small band gap energy is used. The upper limit wavelength (cutoff wavelength) of the light receiving sensitivity is determined by the band gap. That is, transition of electrons or holes due to light is performed in a semiconductor layer having a small band gap energy (direct transition). In this case, the material for extending the cutoff wavelength to a longer wavelength region is very limited in the III-V compound semiconductor. On the other hand, in the type II quantum well structure, when two different semiconductor layers having the same Fermi energy are alternately stacked, the conduction band of the first semiconductor and the valence band of the second semiconductor are obtained. The upper limit of the wavelength (cutoff wavelength) of the light receiving sensitivity is determined. That is, transition of electrons or holes by light is performed between the valence band of the second semiconductor and the conduction band of the first semiconductor (indirect transition). For this reason, the energy of the valence band of the second semiconductor is made higher than that of the first semiconductor, and the energy of the conduction band of the first semiconductor is made lower than the energy of the conduction band of the second semiconductor. By doing so, it is easier to realize a longer wavelength of light receiving sensitivity than in the case of direct transition in one semiconductor.

4. As described above, by selective diffusion using the selective diffusion mask pattern, the p-type impurity is diffused and introduced into the periphery from the periphery of the light receiving element in a planar manner, so that the pn junction is the light receiving element. It is not exposed on the end face of As a result, leakage of photocurrent is suppressed.

FIG. 3 is a sectional view showing a light receiving element array 50 in which a plurality of the light receiving elements 10 are arranged on an epitaxial wafer including a common InP substrate. It is characterized in that a plurality of light receiving elements 10 are arranged without element isolation grooves. As described in 4. above, the p-type region 6 is limited to the inside of each light receiving element, and is reliably separated from the adjacent light receiving elements. The light receiving layer 3 is formed with a multiple quantum well structure, the diffusion concentration distribution adjusting layer 4 is disposed on the light receiving layer 3, and the p-type impurity concentration in the light receiving layer 3 is 5 × 10 ¹⁶ / cm ³ or less. This is the same as the light receiving element 10 in FIG.

Next, a method for manufacturing the light receiving element 10 shown in FIG. 1 will be described. An InP buffer layer 2 or InGaAs buffer layer 2 having a thickness of 2 μm is formed on the n-type InP substrate 1. Next, the light receiving layer 3 having a multiple quantum well structure of (InGaAs / GaAsSb) or (GaInNAs / GaAsSb) is formed. The composition of InGaAs is In _0.53 Ga _0.47 As and the composition of GaAsSb is GaAs _0.52 Sb _0.48 so as to lattice match with InP. As a result, the degree of lattice matching (| Δa / a |: where a is a lattice constant and Δa is a lattice constant difference between them) is 0.002 or less. The thickness of the InGaAs layer (or GaInNAs layer) forming the unit quantum well structure is 5 nm, and the number of pairs (the number of repetitions of the unit quantum well) is 300. Next, an InGaAs layer having a thickness of 1 μm is epitaxially grown on the light receiving layer 3 as a diffusion concentration distribution adjusting layer 4 at the time of introducing Zn diffusion, and finally, an InP window layer 5 having a thickness of 1 μm is epitaxially grown. Both the light receiving layer 3 and the diffusion concentration distribution adjusting layer 4 are preferably epitaxially grown by MBE (Molecular Beam Epitaxy) method. The InP window layer 5 may be epitaxially grown by the MBE method, or after the diffusion concentration adjusting layer 4 is grown, the InP window layer 5 may be taken out from the MBE apparatus and epitaxially grown by the MOVPE (Metal Organic Vapor Phase Epitaxy) method. .

The InP buffer layer 2 or the InGaAs buffer layer 2 may be non-doped, or may be doped with an n-type dopant such as Si at about 1 × 10 ¹⁷ / cm ³ . The light-receiving layer 3 having a multiple quantum well structure of GaInNAs / GaAsSb, the InGaAs diffusion concentration distribution adjusting layer 4 and the InP window layer 5 are preferably non-doped, but a very small amount of n-type dopant such as Si (for example, 2 × 10 ¹⁵ / cm 2). ^{About 3} ) Doping may be performed. Further, a high-concentration n-side electrode forming layer for forming an n-side electrode doped with n-type dopant by about 1E18 cm ⁻³ may be inserted between the InP substrate 1 and the buffer layer 2. The InP substrate 1 may be a Fe-doped semi-insulating InP substrate. In this case, an n-side electrode forming layer doped with n-type dopant of about 1 × 10 ¹⁸ / cm ³ is inserted between the semi-insulating InP substrate 1 and the buffer layer 2.

An optical device is manufactured using a laminated structure (epitaxial wafer) including the InP substrate 1 described above. Using the SiN mask pattern 36 formed on the surface 5a of the InP window layer 5, Zn is selectively diffused from the opening so as to reach the light receiving layer 3 having the InGaAs / GaAsSb (or GaInNAs / GaAsSb) multiple quantum well structure. A p-type region 6 is formed. The front tip of the p-type region 6 forms a pn junction 15. At this time, a high concentration region having a Zn concentration of about 1 × 10 ¹⁸ / cm ³ or more is limited to the InGaAs diffusion concentration distribution adjusting layer 4. That is, the high-concentration impurity distribution continues from the surface 5a of the InP window layer 5 in the depth direction to the InGaAs diffusion concentration distribution adjustment layer 4, and further 5 × at a deeper position in the diffusion concentration distribution adjustment layer 4. It decreases to 10 ¹⁶ / cm ³ or less. The Zn concentration distribution in the vicinity of the pn junction 15 is a distribution indicating an inclined junction.

  The one-dimensional or two-dimensional array of the light-receiving elements 10, that is, the light-receiving element array shown in FIG. 3 is planarly selected so that Zn is selectively diffused without performing mesa etching for element separation (inside the peripheral edge of the light-receiving element). The adjacent light receiving elements are separated from each other by diffusion limited to the periphery. That is, the Zn selective diffusion region 6 is a main part of one light receiving element 10 and forms one pixel, but a region where Zn is not diffused separates each pixel. For this reason, it is possible to suppress dark current without being damaged by crystals accompanying the mesa etching.

  When a pn junction is formed by selective diffusion of impurities, since the diffusion proceeds not only in the depth direction but also in the lateral direction (direction perpendicular to the depth), there is a concern that the element spacing cannot be narrowed beyond a certain level. It is expressed in reference 10. However, when the selective diffusion of Zn is actually performed, in the structure in which the InP window layer 5 is provided on the outermost surface and the InGaAs diffusion concentration distribution adjusting layer 4 is disposed below, the lateral diffusion is performed in the depth direction. It was confirmed to be within the same level or lower. That is, in the selective diffusion of Zn, Zn spreads in the lateral direction with respect to the opening diameter of the mask pattern, but the extent is small, and as shown schematically in FIGS. Only.

FIG. 4 is a cross-sectional view showing a light receiving element 110 in Reference Example 1 different from the present invention. The light receiving element 110 of Reference Example 1 has the following laminated structure.
(InP substrate 101 / InP or InGaAs buffer layer 102 / (GaInNAs / GaAsSb) light-receiving layer 103 / InP window layer 105 having a multiple quantum well structure)
The p-type region 106 is formed by selective diffusion so as to reach the light receiving layer 103 from the surface 105a of the InP window layer 105 using a selective diffusion mask pattern. A pn junction 115 is formed at the tip of the p-type region 106. The difference is that there is no diffusion concentration distribution adjustment layer as compared with the laminated structure in the embodiment of the present invention. That is, the light receiving layer 103 having a multiple quantum well structure is disposed immediately below the InP window layer 105.

Without the diffusion concentration distribution adjusting layer, as shown in FIG. 5, for example, the Zn concentration distribution has a high concentration up to the light receiving layer 103 having a multiple quantum well structure. That is, a high impurity concentration region of 1 × 10 ¹⁸ / cm ³ exceeding 5 × 10 ¹⁶ / cm ³ is formed in the multiple quantum well structure. When high concentration impurities are introduced into the multiple quantum well structure, the structure is destroyed and the dark current is greatly increased. Conversely, in order to prevent such a high concentration impurity region from being formed in the multiple quantum well structure, a diffusion concentration distribution adjusting layer is provided to perform selective diffusion.

However, there is room for the following concept to be established in the selective diffusion of Zn.
(1) The diffusion introduction time is limited to a short time so that the high concentration region does not enter the multiple quantum well structure 103.
(2) The thickness of the InP window layer 105 is increased so that the role of the diffusion concentration distribution adjusting layer is shared by the InP window layer 105.
FIG. 6 is a cross-sectional view showing the light receiving element 110 in Reference Example 2 for studying the cases (1) and (2). The light receiving element 110 of the reference example 2 has substantially the same laminated structure as the light receiving element of the reference example 1, but the thickness of the InP window layer 105 is larger than that of the reference example 1, and corresponds to the case of (2) above. However, it is possible to consider the case of (1). In the stacked structure of FIG. 6, the Zn concentration distribution shown in FIG. 7 is obtained as a result of selective diffusion so that a high concentration region of Zn is not formed in the multiple quantum well structure 103. In the case of the Zn concentration distribution shown in FIG. 7, in the InP window layer 105, the Zn concentration sharply decreases from a high concentration to a low concentration, and in the InP window layer 105 on the light receiving layer side, 1 × 10 ¹⁶ / cm. ^{About 3} low-concentration impurity regions are formed.

When a low-concentration impurity region of about 1 × 10 ¹⁶ / cm ³ is formed in the InP window layer 105, the electrical resistance increases in that region as described above, and the response speed decreases. For this reason, a material having a band gap energy that is large enough to form the window layer, specifically, the InP window layer 105 that is a typical material thereof cannot play the role of the diffusion concentration distribution adjusting layer. This is the same for the cases (1) and (2). Therefore, it is preferable to use a material having a band gap energy equal to or lower than InP, specifically, less than 1.34 eV, for the diffusion concentration adjusting layer. That is, even in a low concentration impurity region, it is necessary to use a material such as InGaAs in which the decrease in electrical conductivity is relatively small and the increase in electrical resistance is relatively small.

Embodiment 2 Structure of Imaging Device (Component Distribution Image Forming Device) in Biological Component Detection Device
FIG. 8 is a diagram showing an outline of an imaging device (light receiving element array) included in the biological component detection device in Embodiment 2 of the present invention. Optical parts such as lenses are omitted. FIG. 9 is a diagram for explaining the light receiving element array 50 in the imaging device or the detection device (image sensor) 70 described above. FIG. 10 is a diagram showing one light receiving element in the light receiving element array 50 of FIG. 9. In FIG. 8, in this imaging device 70, the light receiving element 10 formed on the common InP substrate 51 is so-called epi down mounted with the epitaxial layer side facing the multiplexer 71 having the function of a mounting substrate. The p-side electrode 11 electrically connected to the p-type region 6 of the epitaxial layer of each light receiving element 10 and the n-side electrode 12 provided on the common n-type InP substrate 51 (1) are connected to the multiplexer 71. Then, an electric signal is sent to the multiplexer, and the multiplexer 71 receives the electric signal from each light receiving element and performs a process of forming an entire image of the object. The n-side electrode 12 and the p-side electrode 11 are electrically connected to the multiplexer 71 via solder bumps 12b and 11b, respectively. Incident light is introduced through an AR (Anti-Reflection) film 35 formed on the back surface of the InP substrate 51, and is received by a pn junction 15 that is an interface between the p-type region 6 and the light-receiving layer 3. The p-type region 6 is introduced from an opening of a SiN Zn diffusion mask 36 that also serves as a protective film. The Zn diffusion mask pattern 36 is left as it is together with the protective SiON film pattern 43 formed thereon. The structure of the light receiving element array and each light receiving element will be described in detail below with reference to FIGS. 9 and 10.

  In FIG. 9, the light receiving elements 10 of the light receiving element array 50 are provided on a common InP substrate 51 (1). A current signal generated by receiving light in the SWIR band by each light receiving element is sent to the multiplexer 71 that also serves as a mounting board as described above, and image forming processing is performed. The number of pixels is changed while changing the size and pitch of each light receiving element and the size of the array. The light receiving element array 50 shown in FIG. 9 has 90,000 pixels. The light receiving element 10 shown in FIG. 10 has a plurality of epitaxial films formed on the InP substrate 1, and a p-type impurity introduction diffusion mask 36 used for forming the p-type region 6 is provided. I'm leaving. A p-type electrode 11 is connected to the p-type region 6 and connected to wiring of a mounting substrate such as the multiplexer 71 by solder bumps or the like.

  FIG. 11 is a cross-sectional view for explaining an epi-up mounted light receiving element, unlike the epi-down light receiving element shown in FIG. In the present invention, the light receiving element in the imaging apparatus may be either epi-down mounting or epi-up mounting. The light receiving element 10 is formed on an n-type InP substrate 1 in order from the bottom: n-type InP buffer layer 2 / light-receiving layer 3 / diffusion concentration distribution adjusting layer 4 / InP window layer 5 / diffusion mask 36 / antireflection film (AR Membrane (Anti-Reflection) 35 is located. The p-type region 6 is formed from the InP window layer 5 to the pn junction 15 in the light receiving layer 3 through the diffusion concentration distribution adjusting layer 4. The n-side electrode 12 is located on the back surface of the n-type InP substrate, and the p-side electrode 11 is located on the surface of the InP window layer 5 in the p-type region 6 and is electrically connected to the wiring electrode 27. In the present embodiment, the light receiving layer 3 receives light in the wavelength range of 1.0 μm to 3.0 μm. Specifically, the light receiving layer 3 is formed by the above-described type II multiple quantum well structure.

  The light receiving element shown in FIG. 11 is epi-up mounted as described above, and light is incident from the epitaxial layer, that is, the InP window layer 5 side. As described above, the light receiving element in the present embodiment may be either epi-up mounting or epi-down mounting. As shown in FIG. 12, the light-receiving element may be epi-down mounting and receive light from the back side of the InP substrate 1. In the case of the epi-down mounted light receiving element 10 in FIG. 12, an AR film 35 is applied to the back surface of the InP substrate 1. The diffusion mask 36 of SiN also serving as the diffusion concentration adjusting layer 4, the InP window layer 5, the p-side electrode 11 and the protective film is provided in the same manner as in the case of epi-up mounting. In the case of the epi-down mounting shown in FIG. 12, since InP such as an InP substrate is transparent to SWIR band light, the SWIR band light reaches the pn junction 15 of the light receiving layer 3 without being absorbed. Also in the structure of FIG. 12, the light receiving layer is formed by the above-described type II multiple quantum well structure. This also applies to the following examples of the present invention unless otherwise specified.

  The p-side electrode 11 and the n-side electrode 12 may be arranged at positions facing each other with the InP substrate 1 interposed therebetween as shown in FIG. 11, or the same side of the InP substrate 1 as shown in FIG. You may arrange | position in the position of. In the case of the structure shown in FIG. 12, each light receiving element 10 of the light receiving element array 50 shown in FIG. 9 and the integrated circuit are electrically connected by flip chip mounting. In the light receiving element having the structure shown in FIGS. 11 and 12, the light reaching the pn junction 15 is absorbed to generate a current signal, which is converted into an image of one pixel through the integrated circuit as described above.

  The InP substrate 1 is preferably an off-angle substrate inclined from 5 to 20 degrees in the [111] direction or the [11-1] direction from (100). More preferably, it is inclined from 10 to 15 degrees from (100) to the [111] direction or the [11-1] direction. By using such a large off-angle substrate, the n-type InP buffer layer 2, the type II quantum well structure light-receiving layer 3, the InGaAs diffusion concentration distribution adjusting layer 4 and the InP window layer having a small defect density and excellent crystallinity are used. 5 can be obtained. As a result, it is possible to obtain a light receiving element array and a detection device in which dark current is suppressed and there are few dark spots. For this reason, it is possible to obtain a light receiving layer that greatly improves the performance of the device that receives weak SWIR band space light and images it. That is, the action of the light receiving element formed using the off-angle substrate is particularly useful for improving the quality of an image pickup apparatus that receives and picks up space light.

  The large off angle as described above has never been proposed for the InP substrate, and has been confirmed for the first time by the present inventors, and is important for growing a good crystalline epitaxial film on the InP substrate. Is an element. For example, when a compound semiconductor containing N, for example, GaInNAs, is included in the light-receiving layer 3 having the above-described quantum well structure, which can emit and receive light in a very long wavelength region, a large off angle as described above. Unless an InP substrate is used, in practice, it is impossible to form a good epitaxial layer that can withstand practical use. That is, unless an InP substrate having a large off-angle as described above is used, a compound semiconductor containing N, such as GaInNAs, suppresses dark current and does not become a light-receiving layer with reduced dark spots. As a result, a clear image cannot be obtained using weak SWIR band space light. In addition to GaInNAs given as an example above, the off-angle of the InP substrate is the same in GaInNAsP and GaInNAsSb in that a large angle range as described above is necessary to obtain good crystallinity.

  The light receiving element 10 shown in FIGS. 11 and 12 includes an InGaAs diffusion concentration adjusting layer 4 and an InP window layer 5 positioned so as to cover the light receiving layer 3. Since the lattice constant of the light receiving layer 3 is the same as the lattice constant of the InP substrate 1, the InGaAs diffusion concentration adjusting layer 4 and the InP window layer 5 that are well-established by reducing the dark current are formed on the light receiving layer 3. be able to. For this reason, dark current can be suppressed and element reliability can be improved.

(Embodiment 3: Biological component detection device (1)-blood glucose level: measurement by reflected light-)
FIG. 13 is a diagram showing a biological component detection apparatus 100 according to Embodiment 3 of the present invention. FIG. 14 is a diagram showing a probe in the biological component detection apparatus 100 of FIG. It is important for diabetic patients to know their own blood glucose level, which is reduced by insulin administration in response to an increase in blood glucose level. For this reason, patients measure blood glucose levels on a daily basis, but it is preferable for patients to be able to accurately measure noninvasively without collecting blood.
The noninvasive blood glucose level measurement is based on the fact that the glucose concentration in the skin tissue has a high positive correlation with the glucose concentration in the blood, and the glucose concentration in the skin tissue is used as the blood glucose level. Since the glucose concentration in the skin tissue is as small as several tens to several hundreds mg / dl, it is necessary to irradiate the skin with near-infrared light and to capture the light transmitted through or diffusely reflected through the skin tissue with high accuracy. .

  In order to measure a small amount of glucose concentration with high accuracy, it is effective to use two or more absorption bands in the near-infrared absorption band of glucose. Glucose has a number of absorption bands in the wavelength range of 1 μm to 3 μm. However, as long as a conventional InGaAs array is used, near infrared light with a wavelength of 1.7 μm or less can be measured with high accuracy. High-precision measurements were not possible for light in the absorption band. As shown in FIG. 13, by using the detection device 70 shown in FIG. 8, it is possible to receive light with a wavelength expanded to 3.0 μm. In addition, by aligning the diffraction grating 91 and the light receiving element array 50, the absorption spectrum of glucose can be performed once (one chance) of irradiation and light reception. Therefore, it becomes easy to measure the glucose concentration using an absorption band having a wavelength of 1.8 μm or more, and a trace amount of glucose in the skin can be measured accurately and easily.

  There are the following factors for improving the measurement accuracy of the glucose concentration. The stability of spectrum measurement can be increased by suppressing fluctuations in absorbance and baseline as much as possible. Elements on the apparatus that change the spectrum to be measured include fluctuations in the positional relationship between components such as the light source and the light receiving element unit, and changes in environmental temperature over time. In order to correct these variations, it is common to measure a reference signal reflected from a reference plate such as a ceramic plate separately from the biological signal and use it as a reference light. For this reason, in order to perform spectrum measurement stably, it is important that stable measurement of the reference signal is possible.

Taking FIG. 13 as an example, near-infrared light in the measurement of the detection site takes the following path.
Light source 73-> diffuser plate 74-> irradiation optical fiber 81-> sensing unit (probe) 83-> detection site-> sensing unit (probe) 83-> information-equipped optical fiber 82-> diffraction grating (spectrometer) 91-> detection device 70-> concentration calculation Microcomputer 85b
When taking the above-mentioned path, a probe with an irradiation optical fiber and an information mounting optical fiber is applied to a detection site (skin). On the other hand, in the measurement of the reference signal, only the above-mentioned detection site is replaced with the reference plate. An operation of pressing the probe away from the skin and pressing it against the reference plate is performed. Based on the reference signal and the biological signal, the concentration calculating microcomputer calculates the glucose concentration.

  The measurement of the reference signal by the above method involves variations in the position reproduction between the probe and the reference plate and the occurrence of a measurement time difference between the reference signal and the biological signal. Repeating the above operation for each measurement makes the reference signal stable. Make measurement difficult. For this reason, conventionally, instability of spectrum measurement due to reference signal fluctuation cannot be sufficiently corrected, and it has been difficult to accurately perform glucose concentration analysis. The probe 83 shown in FIG. 14 eliminates the instability of the reference signal measurement. Without measuring the reference plate, the optical fiber 84 that directly connects the irradiation optical fiber 81 and the information mounting optical fiber 82 is arranged, and the switches SW1, SW2, and SW3 are arranged respectively. As a result, there is no variation in the position reproduction between the probe and the reference plate, and the measurement time difference between the reference signal and the biological signal is reduced. The switches SW1, SW2, and SW3 may be manually operated or may be automatic switches that are automatically turned on / off in response to an instruction from the microcomputer 85b.

(Embodiment 4: Biological component detection device (2)-blood glucose level: measurement by transmitted light-)
FIG. 15 is a diagram showing a biological component detection apparatus 100 according to Embodiment 4 of the present invention. In FIG. 15, the above-described detection device 70 is used for the light receiving unit, and the concentration measurement is performed using an absorption band located in the long wavelength region of glucose in the near infrared region, which is the same as in the third embodiment. The present embodiment is different from the third embodiment in that the glucose concentration is obtained by measuring near infrared light transmitted through the living body. The example shown in FIG. 15 receives light transmitted through a human finger, but can obtain information on many biological tissues such as skin, muscle, and blood.

The measurement of the reference signal is performed by the transmitted light of the reference plate that is retracted when the living body (finger) is inserted and is inserted when the living body is retracted. Although the thickness of the reference plate depends on the material of the reference plate, it is preferable to make it thin so that the amount of transmitted light is sufficient. The reference plate is moved by the actuator 75 so that variations in position and posture (angle) do not occur.
Instead of using the reference plate as described above, as shown in FIG. 14, an optical fiber 84 that bypasses and connects the irradiation optical fiber 81 and the information mounting optical fiber 82 is arranged, and each optical fiber 81, 82 and 84 may be provided with switches.

(Embodiment 5: Biological component detection device (3)-blood glucose level: measurement by transmitted light-)
FIG. 16 is a diagram showing a biological component detection apparatus 100 according to Embodiment 5 of the present invention. This biological component detection apparatus 100 is characterized in that a biological charging groove 77a is provided in a part of the housing 77, and a blood glucose level is detected using transmitted light of the biological body inserted in the biological charging groove 77a. There is. The living body part to be inserted is assumed to be the tip of the shoulder, for example, an arm or a palm, and can be the living body inserting groove 77a having the maximum size among them. It may be a living body insertion groove 77a specializing in the earlobe.

The path of near infrared light is as follows.
Light source 73-> condensing lens 87-> reflecting mirror 76-> condensing lens 87-> irradiation optical fiber 81-> detection site-> light receiving end 82a-> press-adjusting actuator 82b-> information-equipped optical fiber 82-> condensing lens 87-> diffraction grating 91 → detection device 70 (see FIG. 8)
The lower part of the little finger when making a hand sword with a palm can transmit light without interposing a bone, which is effective in measuring blood sugar level. The living body insertion groove 77a is not particularly required to be focused on the palm portion below the little finger, and can be aligned by the pressure adjusting actuator 82b or the like. As a result, the patient can easily and accurately measure the blood glucose level.
The light receiving element array 50 in the detection device 70 can receive light up to a long wavelength region in the near infrared region, and the measurement accuracy is improved as in the third and fourth embodiments. As the light source, a halogen lamp or the like is preferably used, but in the case of this biological component detection apparatus 100, it is preferable to use a continuum light source or an LED that generates little heat.

(Embodiment 6: Biological component detection device (4)-Blood glucose level: Accuracy improvement by multiple sampling with one probe-)
FIG. 17 is a diagram showing the biological component detection apparatus 100 according to Embodiment 6 of the present invention. FIG. 18 is an enlarged view of a probe portion in the biological component detection apparatus 100 of FIG. In the biological component detection apparatus 100, information is obtained from reflected light by irradiating the detection site (skin) with near infrared light. At that time, the irradiation light and the probe are single as shown in FIG. 18, but three light receiving end portions 61, 62 and 63 are accommodated in the probe 83. Near-infrared light received by these three light receiving end portions 61, 62, 63 propagates through different information-equipped optical fibers 82. When the light is split by the diffraction grating 91 and received by the detection device 70 (see FIG. 8), the selection switch 66 separately splits the light that has been captured and propagated by the light receiving end portions 61, 62, and 63. Receive light. A feature of the present embodiment is that a plurality of light receiving end portions are accommodated in one probe, and reflected light is taken in at a plurality of positions to perform spectroscopy and analysis. A prism, an optical fiber, or the like can be used for the light receiving end.

Near-infrared light applied to the skin diffuses through the surface layer in the skin, and then exits to the outside, where it is captured by the light receiving end. By performing multiple acquisitions or multiple samplings, the near-infrared light path in the skin at the detection site is averaged rather than a special one. The reliability of the blood glucose level data can be greatly improved by averaging the paths in the skin surface layer. In order to obtain such a multiple sampling effect with certainty, the distance d between the light receiving ends is preferably about 1 mm or more, for example.
The biological component detection apparatus 100 shown in FIG. 17 can show a spectrum from a wavelength of 1 μm to 3 μm for each light of the light receiving end portions 61, 62, and 63. The computing unit (microcomputer) 85 can obtain the biological component concentration using the same plurality of wavelengths or a plurality of different wavelengths for the light from each light receiving end. As a biological component, not only blood glucose level but also cholesterol, albumin, hemoglobin, bilirubin and the like can be detected with high accuracy.

(Embodiment 7: biological component detection apparatus (5) -body fat-)
FIG. 19 is a diagram showing a biological component detection apparatus 100 according to Embodiment 7 of the present invention. In the present embodiment, the biological component is body fat. Since body fat has a plurality of absorption bands in the near infrared region, it can be detected by a near infrared spectrum. Pressure is applied to the detection of body fat. In FIG. 19, a probe 83 is fitted into a table 95, and a living body (finger) is placed on the probe 83. An irradiation optical fiber 81 and an information mounting optical fiber 82 are attached to the probe 83. A pressure is applied to the finger by an air bag 96. The airbag 96 is housed in a housing 97, and air is charged and discharged through an air pipe 69. Based on the pressure gauge 68, the microcomputer 85 can appropriately operate the air pump 69, send air from the air pipe 69 to the airbag 96, and apply pressure to the finger.

The near infrared light path is as follows.
Light source 73 → irradiation optical fiber 81 → probe 83 → finger → probe 83 → information-equipped optical fiber 82 → diffraction grating 91 → detector 70 (see FIG. 8) → microcomputer 85
The pressure applied to the finger can be known with the pressure gauge 68, and the body fat ratio can be known for each pressure. Furthermore, conventionally, an absorption peak of 1.21 μm has been exclusively used for detection of body fat by near infrared light. As described above, by using the light receiving element array 50 (see FIGS. 3 and 8) in the detection device 70, the light receiving range can be expanded up to a wavelength of 3 μm, so that an absorption peak in a longer wavelength range up to 3 μm is obtained. It is possible to detect the body fat percentage with higher accuracy.

(Embodiment 8: Biological component detection device (6)-Detection of collagen distribution in cornea-)
Here, it is proposed that the biological component detection apparatus according to the present invention is useful for detection of collagen distribution in the cornea of an eye particularly sensitive to light in a living body, rather than solving a specific problem. The cornea is mainly composed of collagen and tissue fluid. This collagen is an important component for cosmetic purposes, and the absorption band is distributed in a large range of 1 μm to 3 μm. Therefore, it is suitable for detection by the light receiving element array 50 or the imaging device 70 of the present invention shown in FIG. 3 or FIG.
FIG. 20 is a diagram showing a biological component detection apparatus (eye collagen distribution image forming apparatus) 100 according to Embodiment 8 of the present invention. Although how the eyes are visible is not determined solely by the cornea, it is necessary to know the state of the cornea.
The concave mirror 76 is preferably one having a high reflectivity for near-infrared light, for example, one made of gold (Au). The concave mirror 76 is positioned not on the front of the eye but on the side, and reflects the light emitted from the cornea so that an image of the cornea is formed on the imaging device 70. The filter 72 preferably transmits 1 μm to 3 μm of light belonging to the collagen absorption band. The microcomputer 85b of the control unit 85 forms a collagen distribution image in the cornea C based on the output signal of the pixel of the imaging device 70 and displays it on the display device 85c. As the imaging device 70 according to the present invention, for example, the one shown in FIG. 8 is preferably used. Since the dark current is low and the sensitivity is high up to the long wavelength side, a clear collagen distribution image with a high S / N ratio can be obtained. For this reason, it is useful for understanding the action of collagen in the eye.

  Since the eye is very sensitive to light, it is preferable not to use the light source 73 if possible. FIG. 21 is a diagram showing the intensity distribution of SWIR cosmic light. For example, the peak I of the spectrum of this SWIR cosmic light can be used as the light source. The wavelength of peak I is in the vicinity of 1.4 μm, and is close to the absorption band of collagen. Therefore, in FIG. 21, the SWIR space light can be substituted with the exception of the light source 73. Alternatively, even if the artificial light source 73 is used, the light may be limited to the near infrared region, and the peak value may be set to, for example, twice the peak intensity of the SWIR space light. Eye safe is reliably realized by using the SWIR space light as a light source. As described above, the reason why the SWIR space light or the light source having a low intensity level can be used is that the dark current of the imaging device 70 according to the present invention can be reduced. That is, a clear image can be formed even with a weak signal.

(Embodiment 9: Biological component detection device (7) —Detection of corneal collagen distribution in cornea correction surgery)
A method of performing precise cornea correction surgery by evaporating the cornea using an ArF excimer laser is known. Such corneal correction surgery has advantages such as good controllability of the correction amount, automated surgery, excellent stability, less post-operative infectious side effects, and less decrease in corneal strength. Yes. However, while the above corneal correction surgery is effective in clinical trial results for weak and moderate myopia, increasing the number of times the central cornea is irradiated with an ArF excimer laser increases the corneal surface of the biological fluid. The leaching of the cornea becomes noticeable and the corneal transpiration does not progress. For this reason, there is a problem in that the amount of correction scheduled for high myopia cannot be obtained, and the success rate of the operation is deteriorated. When the cornea was irradiated with an ArF excimer laser, when nitrogen gas was blown to remove mushroom-like sprays generated from the cornea surface during transpiration, there was a problem that the surface was dried and the smoothening of the transpiration surface deteriorated.

  As described above, the wet state of the corneal surface during surgery is an important factor affecting the quality of transpiration, and it is necessary to monitor the wet state of the corneal surface during surgery. At the time of corneal transpiration by irradiation with ArF excimer laser, collagen absorbs the laser and transpiration mainly, and the tissue fluid occupying about 80% of the cornea leaches out from the remaining cornea, and the composition of the portion changes to change the ArF excimer laser. Changes in absorption. The ArF excimer laser spent for the transpiration of collagen is converted into vibration and rotation of collagen molecules, resulting in a temperature rise. For this reason, infrared light having an intensity proportional to the fourth power of the temperature is emitted. It has been proposed that the wet state of the cornea can be detected by monitoring this infrared light (Patent Document 7). In this method, since only one infrared waveform corresponds to the entire cornea C, only information on the average wet state of the entire cornea can be obtained. However, in actuality, the leaching of the tissue fluid occurs in islands in one cornea, so it is preferable to have information on the wet state at each position of the cornea.

  By using the imaging device 70 or the light receiving element two-dimensional array 50 according to the present invention, it is possible to clearly obtain information on the collagen concentration at each position of the cornea. The transition of collagen distribution over the entire cornea when leaching occurs transiently during surgery can be detected. Obviously, such detection provides valuable information on the state of the cornea. In this case, the pulse width of the pulse laser is on the order of 10 ns, and it is important to detect the collagen distribution during the subsequent several ms to 1000 ms. After an ArF excimer laser shot, a corneal transpiration mushroom cloud-like spray is generated in about 10 ns. The collagen distribution on the corneal surface is traced on the order of several ms to several tens of ms so as not to be affected by the spray as much as possible. Need to be detected.

  FIGS. 22 and 23 are diagrams for explaining an apparatus for detecting the collagen distribution in the cornea during the operation in the ninth embodiment of the present invention. The light source 73 is disposed so as not to overlap an emission portion of an ArF excimer laser (not shown). In FIG. 22, the optical system is configured to form an image of the cornea on the imaging device 70 or the light receiving element two-dimensional array 50. The output voltage of the pixel or the light receiving element is small (darker) in the cornea where the collagen is high, and the output voltage is high (brighter) in the portion where the collagen is low. Immediately after the ArF excimer laser shot, the waveform (time transition) of the output voltage of each pixel of the imaging device 70 or the light receiving element two-dimensional array 50 is input to and stored in the processing device 85b included in the control unit 85. The pixels of the imaging device 70 or the light receiving elements 10 in the two-dimensional array are associated with each position of the cornea C finely divided as shown in FIG.

  The imaging device 70 according to the present invention can form pixels with a density that is too high to medically grasp the collagen distribution at each position of the cornea. In addition, crosstalk between adjacent pixels is small, and dark current can be very small. Further, as described above, the response time can be shortened by forming the diffusion concentration distribution adjusting layer from InGaAs. For this reason, it is possible to obtain an output voltage waveform at each pixel with high tracking and high accuracy. If all the waveforms of such pixels are collected and the collagen distribution concentration is plotted on the map of the cornea, the leaching state of the entire cornea immediately after the ArF excimer laser shot can be grasped.

(Embodiment 10: Biological component detection device (8)-Collagen distribution image of face-)
The collagen distribution image on the face is important cosmetically. For example, when wrinkles are formed at the edges of the lips and the corners of the eyes, the collagen concentration is considered to be low (Patent Document 6). There is a possibility that the correlation between the high collagen concentration and the skin with no wrinkles is high. The configuration of imaging device 70 in the present embodiment is the same as that in Embodiment 8 or 9, and is not shown.
By using the imaging device 70 according to the present invention, a clear collagen distribution image of the face can be obtained. Further, as described above, eye-safety is a problem in capturing a collagen distribution image of the face. Since the imaging device 70 according to the present invention can obtain a clear image even with a weak signal, SWIR space light can be used without using a light source. Even when a light source is used, a light source with low emission intensity can be used. For this reason, it is easy to overcome the eye-safe problem.

-Example of the structure of the semiconductor light receiving element array-
To what extent the element spacing or pixel pitch of the light receiving element array of the present invention can be reduced was verified by an example using the light receiving element array shown in FIG. The light receiving element interval or the pixel pitch is the width of the non-opening portion of the SiN selective diffusion mask pattern 36 as shown in FIG. After selective diffusion of Zn, the p-side electrode 11 was formed of AuZn, and the n-side electrode 12 was formed of AuGeNi. In the case of FIG. 3, since an Fe-doped semi-insulating substrate is used for the InP substrate 1, the n-side electrode 12 is provided in the buffer layer 2 of high concentration impurities. However, as shown in FIG. When n is used, an n-side electrode may be provided on the back surface of the substrate, or an n-side electrode may be provided on the n-type semiconductor layer (for example, buffer layer 2) adjacent to the substrate on the front surface side of the substrate. In this embodiment, a dark current was measured by applying a reverse bias voltage of 5 V between the p-side electrode 11 and the n-side electrode 12 of the light receiving element array of FIG. The InP window layer 5 has a thickness of 0.6 [mu] m and 1.6 [mu] m, and the element spacing is 7 [mu] m to 20 [mu] m over a range of 7 [mu] m to 20 [mu] m. . The thickness of the diffusion concentration distribution adjusting layer 4 was 1 μm.

The results are shown in FIG. According to FIG. 25, when the thickness of the InP window layer 5 is as thin as 0.6 μm, the dark current can be 1 × 10 ⁻¹⁰ A (ampere) even if the element interval or the pixel pitch is reduced to 5 μm. . When the thickness of the InP window layer 5 is 1.6 μm, as described above, the diffusion of Zn in the lateral direction spreads, and it cannot be set to 1 × 10 ⁻¹⁰ A unless the element spacing exceeds 7 μm. However, according to this example, it was confirmed that the element spacing could be 5 μm by reducing the thickness of the InP window layer 5 to 0.6 μm and disposing the diffusion concentration distribution adjusting layer.

Regarding the action of the diffusion concentration distribution adjusting layer 4, the concentration distribution of Zn in the depth direction was verified by SIMS (Secondary Ion Mass Spectroscopy) analysis. FIG. 26 shows the concentration distribution of Zn in the depth direction. According to FIG. 26, the peak value of the Zn pileup is suppressed to 5 × 10 ¹⁶ cm ⁻³ or less at the interface between the InGaAs diffusion concentration distribution adjusting layer 4 and the light receiving layer 3. For this reason, at the pn junction formed at the intersection of the n-type carrier concentration background of the light-receiving layer 3 and the Zn concentration (marked with a circle in the figure), the Zn concentration can be surely lowered, crystallinity, etc. Can be prevented. The arrangement of the diffusion concentration distribution adjusting layer 4 allows the multiple quantum well structure of the light receiving layer to have its original function.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  The present invention can make a significant contribution in the fields of health and beauty because it can easily perform high-precision inspections compared to existing devices due to the breakthrough performance improvement of InP-based PDs.

It is sectional drawing which shows the light receiving element in Embodiment 1 of this invention. It is a figure which shows Zn density distribution in the light receiving element of FIG. It is sectional drawing which shows the light receiving element array in Embodiment 1 of this invention. It is sectional drawing of the light receiving element of the reference example 1 different from this invention. It is a figure which shows Zn density distribution in the light receiving element of FIG. It is sectional drawing of the light receiving element of the reference example 2 different from this invention. It is a figure which shows Zn density distribution in the light receiving element of FIG. It is a figure which shows the outline | summary of the imaging device in Embodiment 2 of this invention. It is a figure which shows the light receiving element array of the imaging device of FIG. It is a figure which shows one light receiving element in the light receiving element array of FIG. It is sectional drawing of the light receiving element of epi-up mounting. It is sectional drawing of the light receiving element of epi down (flip chip) mounting. It is a figure which shows the biological component detection apparatus (1) in Embodiment 3 of this invention. It is an enlarged view of the probe of the biological component detection apparatus of FIG. It is a figure which shows the biological component detection apparatus (2) in Embodiment 4 of this invention. It is a figure which shows the biological component detection apparatus (3) in Embodiment 5 of this invention. It is a figure which shows the biological component detection apparatus (4) in Embodiment 6 of this invention. It is an enlarged view of the probe of the biological component detection apparatus of FIG. It is a figure which shows the biological component detection apparatus (5) in Embodiment 7 of this invention. It is a figure which shows the biological component detection apparatus (6) in Embodiment 8 of this invention. It is a figure which shows SWIR space light spectrum and the sensitivity distribution of the light receiving element of the example of the present invention. It is a figure which shows the biological component detection apparatus (7) in Embodiment 9 of this invention. It is a figure which shows the position on the cornea from which collagen is detected. It is a fragmentary sectional view of the light receiving element array used for the example. It is a figure which shows the relationship between the dark current measured in the Example, and element spacing. It is a figure which shows the depth direction density | concentration distribution of Zn in an Example.

  DESCRIPTION OF SYMBOLS 1 InP board | substrate, 2 Buffer layer, 3 Light reception layer of multiple quantum well structure, 4 Diffusion density distribution adjustment layer, 5 InP window layer, 5a The surface of a window layer, 6 p-type area | region, 10 Light receiving element, 11 p side electrode, 12 n-side electrode, 12b solder bump, 15 pn junction, 35 antireflection film, 36 selective diffusion mask pattern, 27 wiring electrode, 43 SiON film, 50 light receiving element array, 51 InP substrate, 61, 62, 63 light receiving end, 66 Selection switch, 67 air pump, 68 pressure gauge, 69 air piping, 70 imaging device (detection device), 71 multiplexer (mounting board), 72 filter, 73 light source, 74 diffuser plate, 75 actuator, 76 concave mirror, 77 housing, 77a Living body insertion groove, 81 irradiation optical fiber, 82 information-equipped optical fiber, 82a light receiving end, 82b pressure adjustment Adjusting actuator, 83 probe, 84 optical fiber, 85 control unit, 85b microcomputer (calculation unit, CPU), 85c display unit (output device), 87, 87a, 87b condenser lens, 91 diffraction grating (spectrometer), 95 table 96 air bag, 100 biological component detection device, C cornea, E eye.

Claims (13)

A device for detecting a component of a living body using light in the near infrared region,
A light receiving element made of a III-V semiconductor that receives light in the near infrared region,
The light receiving element has a light receiving layer having a multiple quantum well structure formed on an InP substrate,
The band gap wavelength of the light receiving layer is 1.8 μm or more and 3 μm or less,
In contact with the surface of the light-receiving layer opposite to the InP substrate, a III-V group semiconductor diffusion concentration distribution adjusting layer is provided,
The band gap energy of the diffusion concentration distribution adjusting layer is smaller than InP,
In the light receiving element, a pn junction is formed by selective diffusion of an impurity element that reaches the light receiving layer through the diffusion concentration distribution adjusting layer,
The concentration of the impurity element in the light receiving layer is 5 × 10 ¹⁶ / cm ³ or less,
The n-type impurity concentration before diffusion of the diffusion concentration distribution adjusting layer is 2 × 10 ¹⁵ / cm ³ or less, the diffusion concentration distribution adjusting layer has a low impurity concentration range in the thickness range on the light receiving layer side,
The living body component detection apparatus characterized in that the transmitted light or reflected light from the living body is detected by receiving light of at least one wavelength of 3 μm or less by the light receiving element. The diffusion concentration distribution adjusting layer has a concentration of the impurity element of 1 × 10 ¹⁸ / cm ³ or more on the surface opposite to the surface in contact with the light receiving layer and 2 × 10 on the light receiving layer side. A region of ¹⁶ / cm ³ or less and a thickness between the two regions and smaller than the two regions, the concentration of the impurity element being greater than 2 × 10 ¹⁶ / cm ^{3 and} from 1 × 10 ¹⁸ / cm ³ The biological component detection device according to claim 1, wherein the biological component detection device has a small area.   The biological component detection device according to claim 1, wherein the light receiving layer has a type II quantum well structure.   4. The biological component detection device according to claim 3, wherein the light receiving layer has an (InGaAs / GaAsSb) multiple quantum well structure or a (GaInNAs (P, Sb) / GaAsSb) multiple quantum well structure.   5. The InP substrate according to claim 1, wherein the InP substrate is an off-angle substrate inclined by 5 ° to 20 ° from (100) to a [111] direction or a [11-1] direction. The biological component detection apparatus according to 1.   The biological component detection apparatus according to claim 1, wherein the impurity element is zinc (Zn), and the diffusion concentration distribution adjustment layer is formed of InGaAs.   The biological component detection apparatus according to claim 1, further comprising an InP window layer on the diffusion concentration distribution adjustment layer.   Lattice matching degree (| Δa / a |: where a is a lattice constant between the InP substrate, each layer constituting the quantum well structure of the light receiving layer, the diffusion concentration distribution adjusting layer, and the InP window layer. , Δa is a lattice constant difference between each other) is 0.002 or less.   The biological component detection device according to claim 1, wherein the light receiving elements are arrayed one-dimensionally or two-dimensionally.   2. The detection part of the living body is irradiated with light from a supercontinuum light source (SC light source) or a light emitting diode (LED), and transmitted light or reflected light from the detection part is received. The biological component detection apparatus according to any one of 9.   The image pickup apparatus including a two-dimensional array of the light receiving elements is provided, and a distribution image of components contained in the living body to be examined is formed by the image pickup apparatus. The biological component detection apparatus described.   Irradiating the living body with light in the wavelength range, receiving reflected light from the living body or transmitted light from the living body, and containing glucose, glucose, hemoglobin, cholesterol, albumin, active oxygen contained in the living body The biological component detection device according to claim 1, wherein at least one component of fat, fat, and collagen is detected. A spectroscopic unit that divides light and is located on the light irradiation side of the detection site or after the detection site when viewed from the irradiation side, and a plurality of light receiving elements positioned according to the spectrally separated wavelengths, or The biological component according to claim 12, comprising: a light receiving element array; and a control unit that calculates a component concentration of the living body by performing calculation based on a result of light received by the light receiving element or the light receiving element array. Detection device.

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