JP2008153311A - Semiconductor light receiving element, visual field support device and biomedical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance of an actual night vision support device, a biomedical device, etc. of an automobile by simply increasing the sensitivity in a long wavelength region, and not particularly useful in an actual night vision support device, a biomedical device, etc. Provided is a semiconductor light receiving element capable of exhibiting
A semiconductor light-receiving element 10 formed on a semiconductor substrate 1 includes a first light-receiving layer 3 made of a single-layer compound semiconductor InGaAsN and an absorption wavelength longer than the absorption edge of the first light-receiving layer. A second light receiving layer 4 having an end and having a quantum well structure (InP / InAsP).
[Selection] Figure 1

Description

  The present invention relates to a semiconductor light-receiving element used in an automobile night vision support device, a biomedical device, a foreign matter contamination detection device, and the like, and also to the visibility support device and the biomedical device.

  Near-infrared to mid-infrared light has begun to be used for imaging using cosmic light, biomedical treatment, and the like, and is particularly expected to develop in night vision assistance devices for automobiles. The basic element used in this field is a semiconductor light-receiving element having sensitivity in the above wavelength range. As an application example of such a semiconductor light-receiving element, an InGaAs light-receiving element (In atom: Ga atom = 0. 53: 0.47) (Non-Patent Document 1) and the like.

Further, a photodiode for detecting near-infrared light and mid-infrared light having a wavelength of 1.7 μm to 5 μm by using InGaAsN containing N in the light-receiving layer so that the light-receiving sensitivity is longer than the near-infrared region. Has been proposed (Patent Document 1). In addition, an (InP / InAsP) quantum well structure is used for the light receiving layer, and an avalanche photodiode (hereinafter referred to as APD) that detects light from the mid-infrared to the far-infrared (wavelength: 4 μm to 10 μm) using intersubband transition. Avalanche
Photo Diode) has also been proposed (Patent Document 2). Far-infrared light in a longer wavelength range than mid-infrared light corresponds to light emitted from a living body with body temperature, and has recently been used in night vision assistance devices for automobiles to detect people on the road at night. It has been.

The above situation can be summarized as follows. Near-infrared to far-infrared light has attracted attention from the characteristics of biopermeability, imaging with reflected light from objects of cosmic light at night, imaging with electromagnetic waves emitted from living body temperature, Development of light receiving elements and light emitting elements from the near infrared region to the far infrared region is in progress.
Marshall J. Cohen, "Near-IR imaging cameras operate at roomtemperature", LASER FOCUS WORLD June 1993 p.109 (Sensors Unlimited) JP-A-9-219563 Japanese Patent Laid-Open No. 2002-217445

  The semiconductor light receiving element described above is effective in order to have sensitivity to light in a longer wavelength range in the near infrared to far infrared range. However, there are many cases where an actual night-vision support device, a biomedical device, or the like of an actual car cannot cope with only a semiconductor light receiving element developed toward the above-mentioned target. The light receiving element using GaInNAs as the light receiving layer in Patent Document 1 has not been realized yet because crystal growth of GaInNAs itself is technically difficult. In particular, it is difficult to realize good crystallinity with a bulk crystal having a size of 0.2 μm or more, and the difficulty is particularly remarkable when the wavelength of light to be received exceeds 2 μm. Even if P and Sb are contained in GaInNAs in order to improve crystallinity, it is considered that the light receiving target light has a wavelength of 2 μm to 3 μm at most. SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor light receiving element that can be particularly useful in an actual night vision support device, a biomedical device, and the like, as well as a visibility support device and a biomedical device.

  The imaging device of the present invention is a semiconductor light receiving element formed on a semiconductor substrate. The semiconductor light-receiving element includes a first light-receiving layer made of a single layer compound semiconductor, and a second light-receiving layer having an absorption edge longer than the absorption edge of the first light-receiving layer and having a quantum well structure. It is characterized by providing.

  With this configuration, light in a wide wavelength range that could not be covered by one light receiving layer can be received by one semiconductor light receiving element. In the semiconductor light receiving element described above, either the first light receiving layer of the compound semiconductor single layer or the second light receiving layer of the quantum well structure may be located at a position far from the semiconductor substrate. Further, the epitaxial layer including the two light receiving layers may be arranged on the mounting substrate side, and epi-down mounting with the back surface of the semiconductor substrate as the light incident surface, or the semiconductor substrate with the epitaxial layer as the light incident surface, on the mounting substrate side. Epitop mounting may be used.

As described above, no attempt has been made to cover a wide wavelength range with a single semiconductor light receiving element, and no great utility has been recognized. According to the semiconductor light receiving element having the above-described configuration, it is possible to provide a night view assisting device for automobiles that is excellent in economy and reduced in size and is useful.

  Further, the first light receiving layer is positioned farther from the compound semiconductor substrate than the second light receiving layer, and impurities are introduced from the surface of the epitaxial layer so as to reach the first light receiving layer. Pn junctions may be formed. With this configuration, for example, by using the silicon oxide film used as a mask when introducing impurities as a passivation film, it is possible to efficiently suppress an increase in dark current and obtain a highly reliable semiconductor light receiving element. it can. In the case of this configuration, the first light receiving layer is located farther from the semiconductor substrate than the second light receiving, but may be epi-up mounted or epi-down mounted.

  A layer that scatters and transmits light is provided at a position closer to the light incident surface than the second light receiving layer, or the light is scattered and reflected at a position farther from the light incident surface than the second light receiving layer. A layer can be provided. With this configuration, the light receiving sensitivity in the second light receiving layer having the quantum well structure can be improved.

  The compound semiconductor substrate can be an InP substrate. With this configuration, InGaAsN-based crystals (InGaAsN, InGaAsNSb, InGaAsNP, etc.) lattice-matched to the InP substrate can be used for the first light receiving layer, and light in a wide range of near infrared light can be received. Become. Further, by removing the window layer in the epi-up mounting and by removing the InP substrate in the epi-down mounting, absorption of visible light can be prevented and the sensitivity in the visible range can be provided.

  In addition, the absorption edge of the first light receiving layer can be set in a wavelength range of 1.7 μm to 3 μm. With this configuration, the light receiving sensitivity region of the first light receiving layer can be set to a mid-infrared region and a range that covers a shorter wavelength region than the mid-infrared region. For example, when this semiconductor light-receiving element is used in an automobile night vision assistance device, in addition to the range covered by the first light-receiving layer (imaging by reflected light of space light), the cover of the second light-receiving layer A night vision assistance device having sensitivity in a very wide wavelength range in combination with a range to be received (for example, reception of cosmic light and reception of far-infrared region) can be manufactured using one semiconductor light receiving element. Also, by removing the InP substrate or window layer according to epi-down mounting or epi-up mounting, the first light-receiving layer can cover even visible light {detection of light emitted by signal lamps (red, yellow, blue)}. Is possible. As described above, no attempt has been made to cover a wide wavelength range with a single semiconductor light receiving element, and no great utility has been recognized.

  The film thickness of the first light receiving layer can be set to 0.1 μm or more. With this configuration, it is possible to increase the thickness of the first light receiving layer that is the i layer, increase the chance of light reception, and increase the light receiving sensitivity.

  The first light receiving layer can be any one of InGaAsN, InGaAsNSb, and InGaAsNP. With this configuration, an InGaAsN-based crystal lattice-matched to the InP substrate can be used for the first light receiving layer, and a light receiving layer having sensitivity in a wide range in the mid-infrared region can be easily obtained. The light-receiving layer has a narrow band gap due to the inclusion of N, and can receive light in a longer wavelength range.

  In addition, the second light receiving layer may receive light by intraband transition. With this configuration, it is possible to easily detect light in a long wavelength region that cannot be detected by the first light receiving layer in the second light receiving layer. Since the subband structure is formed in the quantum well structure, light having a long wavelength region with low energy is received at the transition between subbands (inside the band).

  The second light receiving layer can have one or more well layers. With this configuration, it is possible to increase the chance of receiving light in the long wavelength region that cannot be detected by the first light receiving layer, and to increase the light receiving sensitivity in the long wavelength region.

  The absorption edge of the second light receiving layer can be in the range of wavelengths of 3 μm to 10 μm. With this configuration, the second light-receiving layer shares light in the mid-infrared to far-infrared region, and together with the first light-receiving layer, can receive light in a wide range that has never been considered before. It becomes possible. For example, when this semiconductor light-receiving element is used in an automobile night vision support device, it has nighttime sensitivity in a very wide wavelength range from (imaging by reflected light of cosmic light) to (imaging by far-infrared light emitted by human body temperature). The visual field support device can be manufactured using one semiconductor light receiving element. Furthermore, by removing the InP substrate or window layer according to epi down mounting or epi up mounting, the first light receiving layer can cover even visible light {detection of light emitted by signal lights (red, yellow, blue)}. Can do. As described above, no attempt has been made to cover a wide wavelength range with a single semiconductor light receiving element, and no great utility has been recognized.

  In the semiconductor light receiving element, the semiconductor substrate or the window layer positioned so as to sandwich the first and second light receiving layers between the semiconductor substrate and the semiconductor substrate can be removed. With this structure, as described above, depending on whether the semiconductor light receiving element has an epi-down mounting structure or an epi-up mounting structure, the InP substrate or window layer that absorbs visible light is removed, and visible light is received. Sensitivity can be increased.

  A plurality of electrodes arranged in an array arranged for each pixel region can be provided on the back surface opposite to the light incident surface of the semiconductor light receiving element. With this configuration, an electrode for each pixel region arranged in an array collects current generated by light reception, and two-dimensional distribution of light reception, that is, imaging can be performed. The pixel region may have a structure surrounded by vertical and horizontal grooves to prevent crosstalk.

  The semiconductor light receiving element has a pin diode structure, and the first and second light receiving layers can be undoped layers. With this configuration, a light absorption region of an undoped layer or intrinsic (i layer: intrinsic) can be formed thick, and the sensitivity of light absorption in a wide wavelength range that has not been recognized conventionally can be increased. In addition, a very high breakdown voltage performance can be obtained by forming a thick depletion layer over the entire thick i layer. Also in this configuration, the semiconductor light-receiving element may be epi-down mounted or epi-top mounted.

The semiconductor light receiving element described above is an avalanche photodiode (APD: Avalanche).
Photo Diode). With this configuration, it is possible to greatly increase the sensitivity of a semiconductor light receiving element in a wavelength range that has not been recognized in the past due to the current gain resulting from avalanche amplification. Even in the case of a planar structure, the same effect can be obtained by providing a guard ring.

  A visual field support device (including a night vision support device for automobiles) or a biomedical device according to the present invention is characterized by using any one of the semiconductor light receiving elements described above. With this configuration, for example, when this semiconductor light receiving element is used in a biomedical device, by performing processing such as removal of the InP substrate or window layer, (sensitivity to the visible range emitted by blood in each organ of the human body) to (each Using a single semiconductor light-receiving element, a biomedical examination apparatus having sensitivity in a very wide wavelength range from imaging of transmitted organs using near-infrared light) to (imaging of far-infrared light caused by the temperature of each part of the organ) Can be produced. The same applies to the visual field support device, and a night vision support device having sensitivity in a very wide wavelength range from (imaging by reflected light of cosmic light) to (imaging by far infrared light generated by human body temperature) is a single semiconductor. It can be manufactured using a light receiving element. Furthermore, by removing the InP substrate or window layer according to epi down mounting or epi up mounting, the first light receiving layer can cover even visible light {detection of light emitted by signal lights (red, yellow, blue)}. Can do. The visual field support device having the above-described function can be particularly useful in night vision support for automobiles. As described above, no attempt has been made to cover a wide wavelength range with one semiconductor light receiving element, and its usefulness has never been recognized. According to the semiconductor light-receiving element having the above-described configuration, it is possible to provide a biomedical device that is excellent in economy and reduced in size and beneficial to the user. Above all, information useful for the biomedical device can be easily obtained, and the value of the biomedical device can be improved.

According to the semiconductor light receiving element, the visual field support device, and the biomedical device of the present invention, it has light receiving sensitivity in a wide range including the near infrared region, and can be particularly useful.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a semiconductor light receiving element 10 according to Embodiment 1 of the present invention. In FIG. 1, an InP buffer layer 2 containing n-type impurity Si is disposed on an n-type InP substrate 1. On the InP buffer layer 2, an undoped InGaAsN layer 3 as a first light receiving layer is disposed, and on the InGaAs layer 3, a second light receiving layer (undoped InP layer / undoped InAsP layer) is used as a period. A repeating quantum well layer 4 is formed. A p-type InP window layer 5 containing a p-type impurity Be is disposed on the quantum well layer 4. The surface of the p-type InP window layer 5 is processed to have a fine concavo-convex structure, and a layer 9 that scatters and reflects light is provided. An n-part electrode 11 made of AuGeNi is in ohmic contact with the n-type InP substrate, and a p-part electrode 12 made of AuZn is in ohmic contact with the p-type InP window layer 5. Since the back surface of the n-type InP substrate 1 serves as the light incident surface S, that is, epi-down mounting, the n-part electrode 11 has a limited coverage area on the back surface of the n-type InP substrate 1 and is annular. Yes. Note that the layer 9 that scatters and reflects the light having the above-described concavo-convex structure has a very low light receiving sensitivity for light passing through the epitaxial layer vertically in the quantum well layer 4 and improves the light receiving sensitivity for obliquely incident light. Is provided in order to be able to. Instead of the layer 9 that scatters and reflects the light of the concavo-convex structure located behind the quantum well layer 4, the transmitted light is scattered to the light incident surface side from the quantum well layer 4, and the light is scattered and transmitted. You may provide the layer to do.

  Since the first light receiving layer 3 is formed of an InGaAsN layer, it has light receiving sensitivity in the near-infrared region on the long wavelength side and the middle wavelength region on the long wavelength region side, and is visible by performing predetermined processing. Can also have sensitivity in the area. That is, by forming an InGaAs layer containing nitrogen, the light receiving sensitivity is extended to a long wavelength region, and has a light receiving sensitivity from the visible region (with predetermined processing) to a predetermined infrared region (wavelength 2 μm to 5 μm). It becomes possible. The InGaAsN layer may be an InGaAsNSb layer or an InGaAsNP layer. This is because the InGaAsN-based compound semiconductor layer has light receiving sensitivity from the visible region to the infrared region. However, when targeting visible light, it is necessary to remove the InP substrate or the window layer in accordance with epi-down mounting or epi-up mounting so that the visible light sufficiently reaches the light receiving layer.

  The quantum well layer 4 as the second light receiving layer has an absorption edge at a wavelength of 3 μm to 10 μm, and has a light receiving sensitivity with respect to light on a short wavelength side from this wavelength range (middle infrared range to far infrared range). Have. Since the second light receiving layer 4 absorbs light by the in-band transition of the quantum well structure, it can receive light in a longer wavelength region than the interband transition of the compound semiconductor single layer. For this reason, as described above, the second light receiving layer 4 can have light receiving sensitivity to light in a long wavelength range up to a wavelength of 3 μm to 10 μm.

  By arranging the first and second light receiving layers, the light receiving sensitivity for light in the visible region (requires removal of the visible light absorbing layer that hinders sufficient arrival of visible light to the light receiving layer) to light in the far infrared region is one. The semiconductor light receiving element has. The semiconductor light-receiving element including the two light-receiving layers as described above has not been proposed so far for general use or for a specific use with limited use. 1 has a structure in which the second light receiving layer 4 is located farther than the first light receiving layer 3 when viewed from the semiconductor substrate 1, and light is applied to the InP window layer 5. A layer 9 for scattering and reflecting is provided and mounted epi-down.

Next, a method for manufacturing the semiconductor light receiving element 10 will be described. To deposit an epitaxial film on the n-type InP substrate 1, MBE (Molecular
Beam Epitaxy (molecular beam epitaxial growth) method was used. As raw materials, In, Ga, As, P, Si, and Be were supplied from solid sources, respectively. The layer thickness, carrier concentration, etc. of each epitaxial layer shown in FIG. 2 are as follows.
(N-type InP buffer layer 2):
Layer thickness 1.5 μm, carrier concentration 5e15 cm ⁻³
(Undoped InGaAsN layer 3):
Layer thickness 2.5 μm, carrier concentration 1e15 cm ⁻³
The undoped InGaAsN layer 3 is undoped, but has a carrier concentration higher than zero as described above.
(Undoped quantum well layer 4):
(Undoped InP layer thickness 10 nm / InAsP layer thickness 6 nm) × 50 periods (InP window layer 5):
Layer thickness 0.6 μm, carrier concentration 5e15 cm ⁻³

  After the epitaxial layer was formed and the epitaxial substrate of FIG. 2 was obtained, the semiconductor light receiving element shown in FIG. 1 was manufactured by the following procedure. First, wet etching was performed on the surface of the p-type InP window layer 5 to form a layer 9 that scatters and reflects light of the concavo-convex structure. As the etchant for wet etching, a mixed solution of phosphoric acid, hydrogen peroxide solution, and water was used. Subsequently, the p-part electrode 12 made of AuZn was formed on the surface of the p-type InP window layer 5 provided with the layer 9 that scatters and reflects the light having the concavo-convex structure. In addition, an n-shaped electrode 11 having an annular shape was formed on the back surface of the n-type InP substrate 1 in consideration of the fact that the back surface becomes the light incident surface S.

  In the semiconductor light receiving element 10 shown in FIG. 1, a positive potential is applied to the n-part electrode 11, and a negative potential lower than the positive potential is applied to the p-part electrode 12, that is, a reverse bias voltage is applied, and the p-type InP window layer 5 is applied. In the state where the depletion layer is formed in the undoped region (InGaAs layer 3 and quantum well layer 4) between the n-type InP buffer layer 2 and the n-type InP buffer layer 2, the light input is waited. This state can be paraphrased as a state in which a depletion layer is formed in the i-type region of the pin diode. When light enters the standby state from the light incident surface, carriers are excited in the conduction band by the photoelectric effect to form electron-hole pairs in the depletion layer, and a current gain of avalanche amplification resulting from impact ionization can be obtained. .

  In the undoped layer (or i layer), the undoped InGaAsN layer 3 as the first light receiving layer has a thickness of 2.5 μm and is sufficiently thicker than 0.1 μm, and the undoped quantum well layer as the second light receiving layer The number of layers (number of periods) of 4 is 50 periods, which is sufficiently larger than 3 layers (3 periods). Because of the sufficiently thick undoped layers 3 and 4 as described above, the light incident on the semiconductor light receiving element 10 passes through a region that may be received for a long time (that is, due to an increase in the light receiving opportunity). Efficiency, that is, light receiving sensitivity can be increased.

  FIG. 3 shows a configuration in which p-part electrodes 12 are arrayed so that imaging can be performed using the semiconductor light-receiving device shown in FIG. 1 as a basic unit (pixel) (a semiconductor light-receiving device including an electrode having such an array configuration). FIG. In this array arrangement, grooves 33 are provided in the vertical and horizontal directions on the light emitting side, the area surrounded by the grooves 33 is a pixel area, and the p-part electrodes 12 are arranged in each pixel area, collecting the avalanche current in each pixel, Form the brightness. The luminance of these pixels forms an image. 3 shows a structure in which the n-part electrode 11 is provided in a ring shape corresponding to each pixel on the light incident surface S facing the plane on which the p-part electrode 12 is arranged. In this case, it is not necessary to provide one pixel for each pixel, and a common n-part electrode may be provided. For example, when the vertical and horizontal grooves 33 are provided at a pitch of 25 μm, 160,000 pixels are formed within 10 mm × 10 mm.

  As described above, the first light-receiving layer 3 is composed of an InGaAsN layer, the second light-receiving layer 4 is a quantum well structure, and an in-band transition is used, so that a visible region (requires predetermined processing) to a far-infrared region. Can have light receiving sensitivity. As a result, as shown in FIG. 4, for example, when used in an automobile night vision support device, the signal color (red, blue, yellow), imaging by reflection of space light, Imaging with the far-infrared light emitted becomes possible. As a result, in rainy weather, human infrared imaging with rubberized raincoats is impossible to image with far-infrared light, but it is possible to image with reflection of space light, preventing human imaging even in rainy weather where accidents are likely to occur. I can't. Conversely, in places where space light is difficult to reach, such as in tunnels, imaging with far-infrared light emitted by a living body becomes possible. Such high flexibility that can be adapted to many situations is very beneficial in the case of night vision assistance devices for automobiles where it is best to ensure safety and can greatly increase the value of the device. .

  For example, when used in a biomedical device (endoscope, etc.), the color and bleeding status of an organ are determined by receiving light in the visible range (requires predetermined processing), and the transmitted light (reflected in the near infrared range) The shape of the organ adjacent to the endoscope insertion site can be grasped by light or transmitted light from an external light source, and the organ temperature distribution can be grasped by far-infrared light. When the semiconductor light-receiving element of the present invention is used in a biomedical endoscope or the like, a large amount of information can be obtained about a patient's organ in one examination or one endoscopic operation, and the examination or surgery is successful. Can give a big weapon.

(Embodiment 2)
FIG. 5 is a cross-sectional view showing the semiconductor light receiving element 10 according to the second embodiment of the present invention. In the semiconductor light receiving element 10 according to the present embodiment, (1) the first light receiving layer 3 of the compound semiconductor single layer is located farther from the semiconductor substrate 1 than the second light receiving layer 4 having the quantum well structure. And (2) epi-up mounting using the light incident surface S on the epitaxial layer side is characterized. In the second light receiving layer 4 having the quantum well structure, since the light receiving sensitivity of vertically incident light is low, a layer 19 that scatters and transmits light is provided.

  The above-described epitaxial layer can be manufactured under the same conditions as in the first embodiment. The layer 19 that scatters and transmits light can be formed using a commercially available material or the like. With the above configuration, as in the first embodiment, one semiconductor light receiving element has light receiving sensitivity with respect to light in the visible region (requires predetermined processing) to far infrared region. As a result, it can be applied to a device that can be used with high flexibility that can be adapted to many situations. For example, in the case of a night vision assistance device for automobiles in which it is important to ensure safety, it is very beneficial. The value of the device can be greatly increased. The same applies to the case where it is used in a biomedical device.

  FIG. 6 is a cross-sectional view showing a semiconductor light receiving element 10 in which a layer 9 that scatters and reflects light of an uneven structure is provided on the back surface of the semiconductor substrate 1 without using a layer that scatters and transmits light. 5 is a modification of the semiconductor light receiving element shown in FIG. Light that is transmitted through the first light-receiving layer 3 without being received by the first light-receiving layer 3 has a low light-receiving sensitivity by the light-receiving layer having the quantum well structure, so that most of the light is not received. It passes through the light receiving layer 4. After being transmitted, the light on the back surface of the semiconductor substrate 1 is scattered and reflected by the reflecting layer 9 to be scattered light, and returns to the second light receiving layer 4 having the quantum well structure. Since the reflected return light is scattered light, it is received by the second light receiving layer 4 having the quantum well structure. In the case of reflected return light, if light that can be received by the first light receiving layer 3 is included in the light transmitted without being received by the second light receiving layer of the quantum well structure, the reflected return light is once again included. Can receive light. For this reason, it is possible to increase the light receiving efficiency. Also in the semiconductor light receiving element 10 having the structure of FIG. 6, it is possible to obtain the same function and effect as the semiconductor light receiving element shown in FIG.

(Embodiment 3)
FIG. 7 is a diagram showing a semiconductor light receiving element according to the third embodiment of the present invention. In the semiconductor light-receiving element 10 shown in FIG. 7, (1) p-type impurities are diffused and introduced into the first light-receiving layer 3 of the compound semiconductor single layer from the window layer 5 side, and a p-type diffusion region 15 is formed. This is characterized in that a pn junction is formed. Similarly to the second embodiment, the first light receiving layer 3 of the compound semiconductor single layer is located farther from the semiconductor substrate 1 than the second light receiving layer 4 having the quantum well structure, and the epitaxial layer. Another feature is that epi-up mounting with the light incident surface S on the side is made.

  When the pn junction having the planar structure is formed, the p-type impurity is usually diffused and introduced from the mask opening using the silicon oxide film as a mask. Since the silicon oxide film is excellent in stability, the entire passivation film 17 of the semiconductor light receiving element is made of a silicon oxide film while leaving a predetermined portion and supplementing the silicon oxide film with a portion other than the predetermined portion. Form. As a result, a semiconductor light-receiving element having a low dark current and excellent reliability including durability can be obtained as compared with a semiconductor light-receiving element other than a semiconductor light-receiving element having a pn junction having a planar structure, for example. .

  FIG. 7 shows a single-pixel semiconductor light-receiving element 10. However, as shown in FIG. 3, the present invention may be applied to a semiconductor light-receiving element in which a large number of pixel regions are formed by providing vertical and horizontal grooves. However, there are many application opportunities. In this case, since the end surface of the epitaxial layer of the semiconductor light receiving element is covered with the silicon oxide film without being exposed, it is possible to obtain a semiconductor light receiving element having a highly reliable high-density pixel region.

  Even in a semiconductor light-receiving element including a first light-receiving layer having a planar structure pn junction, the p-type diffusion region 15 only occupies a thin layer of the first light-receiving layer 15, and most of the remaining first The light receiving layer 3 is undoped. For this reason, when a reverse bias voltage is applied, the depletion layer protrudes from the pn junction to the undoped region, enters a state including the second light receiving layer, and waits for light reception. Therefore, even the semiconductor light receiving element 10 having the structure shown in FIG. 7 can form an avalanche photodiode and obtain the high current gain described in the first embodiment and the like. By providing the first and second light receiving layers, it is possible to obtain the same effects as those described in the first embodiment.

  In the first to third embodiments of the present invention, the case of being used for detection in the visible region (requires predetermined processing) to the far infrared region has been described. However, the semiconductor light receiving element of the present invention is not necessarily from the visible region to the far infrared region. It need not be used only for detecting light. It does not include the visible region or the far infrared region, and may be used to detect infrared light in a wide range (near infrared region to mid infrared region).

Next, the effect of this invention was verified by the Example. As an example of the present invention, the semiconductor light receiving element 10 shown in FIG. 1 was used. For comparison, the semiconductor light-receiving element having the structure of FIG. 9 having the single-layer compound semiconductor as the light-receiving layer, the semiconductor light-receiving element having the structure of FIG. 8 as Comparative Example A, and the light-receiving layer having the quantum well structure is illustrated. It was set as Comparative Example B. The laminated structures of the present invention example and the comparative example are shown below.
Example of the present invention (FIG. 1): p-part electrode 12 / layer 9 for scattering and reflecting light / p-type window layer 5 / quantum well structure of undoped InP and InGaAsP 4 / undoped InGaAsN light-receiving layer 3 / n-type InP buffer Layer 2 / n part electrode 11 (epi-down mounting)
Comparative Example A (FIG. 8): p-part electrode 112 / p-type window layer 105 / undoped InGaAsN light-receiving layer 103 / n-type InP buffer layer 102 / n-type InP substrate 101 / n-part electrode 111 (epi-down mounting)
Comparative Example B (FIG. 9): p-part electrode 112 / layer 109 for scattering and reflecting light / p-type window layer 105 / quantum well structure of undoped InP and InGaAsP / n-type InP buffer layer 102 / n-type InP substrate 101 / n electrode 111 (epi-down mounting)

(Experiment 1: Light sensitivity to wavelengths of 2.5 μm and 3.5 μm)
In Experiment 1, the sensitivity was compared at wavelengths of 2.5 μm and 3.5 μm using an infrared light source. The results are shown in Table 1.

  According to Table 1, Comparative Example A has sufficiently high detection sensitivity for infrared light with a wavelength of 2.5 μm and also has detection sensitivity in the visible range, but for infrared light with a wavelength of 3.5 μm. It has almost no detection sensitivity. Comparative Example B has sufficiently high detection sensitivity for infrared light having a wavelength of 3.5 μm, but has almost no detection sensitivity for infrared light having a wavelength of 2.5 μm. On the other hand, the semiconductor light receiving element of the example of the present invention has high detection sensitivity with respect to light having wavelengths of 2.5 μm and 3.5 μm.

(Experiment 2: -Sensitivity spectrum from near infrared region to infrared region)
Sensitivity spectra in the near-infrared region to the infrared region of the semiconductor light-receiving elements of the present invention example, comparative example A, and comparative example B were measured. The measurement results are shown in FIG. According to FIG. 10, Comparative Example A has a sensitivity up to a wavelength of 2.5 μm, and Comparative Example B has a sensitivity only in the vicinity of a wavelength of 3.5 μm. On the other hand, the example of the present invention has high detection sensitivity continuously from the short wavelength region to the wavelength of 3.5 μm without interruption. For this reason, as described above, it is possible to have high detection sensitivity in a wide range of infrared region and visible region, and it is possible to give powerful utility to an automobile night vision support device, a biomedical device, and the like.

  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.

  Since the semiconductor light receiving element of the present invention has a sufficiently high detection sensitivity in a visible wavelength range and a predetermined wavelength range in the infrared range, it can be used for a night vision support device of a car, a biomedical device, etc. Usefulness can be greatly increased.

It is a figure which shows the semiconductor light receiving element in Embodiment 1 of this invention. It is a figure which shows the epitaxial laminated structure of the semiconductor light receiving element of FIG. It is sectional drawing which shows the array arrangement | sequence of the semiconductor light receiving element of FIG. It is a figure for demonstrating the effect of the semiconductor light receiving element in Embodiment 1 of this invention. It is a figure which shows the semiconductor light receiving element in Embodiment 2 of this invention. It is a figure which shows the modification of the semiconductor light receiving element of FIG. It is a figure which shows the semiconductor light receiving element in Embodiment 3 of this invention. It is a figure which shows the semiconductor light receiving element of the comparative example A of an Example. It is a figure which shows the semiconductor light receiving element of the comparative example B of an Example. It is a figure which shows the sensitivity spectrum of the semiconductor light receiving element of the example of the present invention, comparative example A, and comparative example B.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 InP board | substrate, 2 InP buffer layer, 3 1st light receiving layer (compound semiconductor single layer), 4 2nd light receiving layer (quantum well structure), 5 InP window layer, 9 Layer which scatters and reflects light, 10 Semiconductor light-receiving element, 11 n-part electrode, 12 p-part electrode, 15 p-type diffusion region, 17 passivation film, 19 layer that scatters and transmits light, 33 groove, S light incident surface.

Claims (16)

A semiconductor light receiving element formed on a semiconductor substrate,
A first light-receiving layer made of a single-layer compound semiconductor;
A semiconductor light-receiving element comprising: a second light-receiving layer having an absorption edge having a longer wavelength than the absorption edge of the first light-receiving layer and having a quantum well structure.   The first light-receiving layer is located farther from the semiconductor substrate than the second light-receiving layer, and impurities are introduced from the surface of the epitaxial layer so as to reach the first light-receiving layer. The semiconductor light receiving element according to claim 1, wherein a junction is formed.   A layer that scatters and transmits light is provided at a position closer to the light incident surface than the second light receiving layer, or light is scattered at a position farther than the second light receiving layer from the light incident surface. The semiconductor light receiving element according to claim 1, further comprising a reflective layer.   The semiconductor light receiving element according to claim 1, wherein the semiconductor substrate is an InP substrate.   5. The semiconductor light receiving element according to claim 1, wherein an absorption edge of the first light receiving layer is in a wavelength range of 1.7 μm to 3 μm.   The semiconductor light-receiving element according to claim 1, wherein the first light-receiving layer has a thickness of 0.1 μm or more.   The semiconductor light receiving element according to claim 1, wherein the first light receiving layer is one of InGaAsN, InGaAsNSb, and InGaAsNP.   The semiconductor light receiving element according to claim 1, wherein the second light receiving layer receives light by intraband transition.   The semiconductor light-receiving element according to claim 1, wherein the second light-receiving layer has one or more well layers.   10. The semiconductor light receiving element according to claim 1, wherein an absorption edge of the second light receiving layer is in a wavelength range of 3 μm to 10 μm.   The window layer positioned so as to sandwich the semiconductor substrate or the first and second light-receiving layers between the semiconductor substrate and the semiconductor substrate is removed. The semiconductor light receiving element as described.   The semiconductor light-receiving element according to claim 1, further comprising a plurality of electrodes arranged in an array arranged for each pixel region on a back surface opposite to a light incident surface of the semiconductor light-receiving element.   The semiconductor light-receiving element according to claim 1, wherein the semiconductor light-receiving element has a pin diode structure, and the first and second light-receiving layers are undoped layers.   The semiconductor light receiving element according to claim 1, wherein the semiconductor light receiving element is an avalanche photodiode.   A field-of-view support apparatus using the semiconductor light-receiving element according to claim 1.     A biomedical device using the semiconductor light-receiving element according to claim 1.

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