JP2015191894A - Light-emitting/receiving element and sensor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting/receiving element with high sensing performance.SOLUTION: A light-emitting/receiving element 1 comprises: a one-conductivity type semiconductor substrate 2; a light-emitting element 3a formed by laminating, on an upper surface of the semiconductor substrate 2, a buffer layer 30a, a first contact layer 30b, a first cladding layer 30c, an active layer 30d, a second cladding layer 30e, and a second contact layer 30f; and a light-receiving element 3b which has a reverse conductive type semiconductor region 32 obtained by doping the upper surface side of the semiconductor substrate 2 with a reverse conductive type impurity. The buffer layer 30a is of a reverse conductive type containing the reverse conductive type impurity. The first contact layer 30b and the first cladding layer 30c are of the one-conductivity type. The second cladding layer 30e and the second contact layer 30f are of the reverse conductive type.

Description

  The present invention relates to a light receiving / emitting element in which a light receiving element and a light emitting element are arranged on the same substrate, and a sensor device using the same.

  Conventionally, there are various sensor devices that detect the characteristics of an irradiated object by irradiating the irradiated object with light from the light emitting element and receiving the regular reflection light and diffuse reflected light with respect to the light incident on the irradiated object by the light receiving element. Proposed. This sensor device is used in a wide range of fields. For example, it is used in various applications such as photo interrupters, photo couplers, remote control units, IrDA (Infrared Data Association) communication devices, optical fiber communication devices, and document size sensors. It has been.

  In such a sensor device, for example, when the light receiving element receives regular reflection light of light irradiated on the object from the light emitting element, the light receiving element can receive more accurate regular reflection light. It is preferable that the light receiving element is disposed closer to the light receiving element.

  For example, in Patent Document 1 below, an impurity is doped on one surface of a semiconductor substrate made of silicon, and a shallow pn junction region having a light receiving function and a deep pn junction region having a light emitting function are formed adjacent to each other. A light emitting element is described.

  However, when the light receiving element and the light emitting element are integrally formed on the same silicon substrate, when the light emitting element is driven, a leakage current (so-called noise current) is generated and flows into the light receiving element through the silicon substrate. There is a case. This leakage current is mixed as an error component (noise) in the output current from the light receiving element (current output according to the light receiving intensity). Therefore, the conventional light emitting / receiving element has a problem that the detection accuracy of the reflected light by the light receiving element is lowered due to the generation of such a noise current. As the light receiving element and the light emitting element are arranged closer to each other, this leakage current increases. That is, in order to receive accurate specularly reflected light by the light receiving element, it is desirable that the light emitting portion and the light receiving portion are closer, but on the other hand, the leakage current increases. For this reason, the conventional light emitting and receiving element has a problem that the detection accuracy cannot be increased.

JP-A-8-46236

  The present invention has been made in view of the above problems, and an object thereof is to provide a light emitting / receiving element having high sensing performance and a sensor device using the same.

  The light emitting / receiving element according to the present invention includes a semiconductor substrate of one conductivity type, and a buffer layer, a first contact layer, a first cladding layer, an active layer, a second cladding layer, and a second contact layer laminated on the upper surface of the semiconductor substrate. A light-emitting element; and a light-receiving element having a reverse-conductivity-type semiconductor region doped with a reverse-conductivity-type impurity on an upper surface side of the semiconductor substrate, and the buffer layer has a reverse-conductivity-type containing an impurity exhibiting a reverse-conductivity type The first contact layer and the first cladding layer are of one conductivity type, and the second cladding layer and the second contact layer are of a reverse conductivity type.

  The sensor device of the present invention is a sensor device using the above-described light receiving and emitting element, and irradiates an object to be irradiated with light from the light emitting element, and outputs the light received in response to reflected light from the object to be irradiated. It is characterized in that at least one of position information, distance information, surface information and concentration information of the object to be irradiated is detected according to an output current from the element.

  According to the light emitting / receiving element of the present invention, it is possible to provide a light emitting / receiving element and a sensor device with high sensing performance.

(A) is a top view which shows an example of embodiment of the light receiving and emitting element of this invention. (B) is a schematic sectional drawing in alignment with the 1I-1I line | wire of Fig.1 (a). (A) is sectional drawing of the light emitting element which comprises the light emitting / receiving element shown in FIG. (B) is sectional drawing of the light receiving element which comprises the light receiving and emitting element shown in FIG. It is a schematic sectional drawing which shows an example of embodiment of the sensor apparatus using the light emitting / receiving element shown in FIG. It is the figure which put together the presence or absence of the leakage current with respect to the thickness of a buffer layer, and carrier density in the light emitting / receiving element which concerns on an Example and a comparative example. In the light-receiving / emitting element which concerns on an Example and the comparative example 1, it is the figure which observed the surface state of the semiconductor layer which comprises a light emitting element. In the light-receiving / emitting element which concerns on an Example, it is a diagram which shows the mode of the emitted light intensity change with respect to the continuous electricity supply time of a light emitting element.

  Hereinafter, an example of an embodiment of a light emitting / receiving element and a sensor device using the same will be described with reference to the drawings. In addition, the following examples illustrate embodiments of the present invention, and the present invention is not limited to these embodiments.

(Light emitting / receiving element)
A light emitting / receiving element 1 shown in FIGS. 1A and 1B is incorporated in an image forming apparatus such as a copying machine or a printer, for example, and position information, distance information, or density information of an irradiated object such as toner or media. It functions as a sensor device that detects the above.

  The light emitting / receiving element 1 includes a semiconductor substrate 2 of one conductivity type, a light emitting element 3a having a plurality of semiconductor layers stacked on the upper surface of the semiconductor substrate 2, and an impurity of opposite conductivity type doped on the upper surface side of the semiconductor substrate 2. And a light receiving element 3b having a reverse conductivity type semiconductor region 32.

The semiconductor substrate 2 is made of one conductivity type semiconductor material. There is no limitation on the impurity concentration of one conductivity type. In this example, an n-type silicon (Si) substrate containing phosphorus (P) at a concentration of 1 × 10 ¹⁷ to 2 × 10 ¹⁷ atoms / cm ³ as one conductivity type impurity is used for the silicon (Si) substrate. . Examples of the n-type impurity include, in addition to phosphorus (P), nitrogen (N), arsenic (As), antimony (Sb), bismuth (Bi), and the like, and the doping concentration is 1 × 10 ¹⁶ to 1 × 10. ²⁰ atoms / cm ³ .

  In this example, the one conductivity type is n-type, and the reverse conductivity type is p-type.

  A light emitting element 3a is arranged on the upper surface of the semiconductor substrate 2, and a light receiving element 3b is arranged corresponding to the light emitting element 3a. The light emitting element 3a functions as a light source of light that irradiates the irradiated object. Then, the light emitted from the light emitting element 3a is reflected by the irradiated object and enters the light receiving element 3b. The light receiving element 3b functions as a light detection unit that detects the incidence of light.

  As shown in FIG. 2A, the light emitting element 3 a is formed by laminating a plurality of semiconductor layers on the upper surface of the n-type semiconductor substrate 2.

  First, on the upper surface of the n-type semiconductor substrate 2, an n-type semiconductor substrate 2 and a semiconductor layer stacked on the upper surface of the n-type semiconductor substrate 2 (in this case, an n-type first contact layer described later) A buffer layer 30a for buffering the difference in lattice constant from 30b) is formed. The buffer layer 30a constitutes the n-type semiconductor substrate 2 and the light emitting element 3a by buffering the difference in lattice constant between the n-type semiconductor substrate 2 and the semiconductor layer formed on the upper surface of the n-type semiconductor substrate 2. Lattice defects such as lattice strain generated between the semiconductor layer and the semiconductor layer to be formed are reduced. As a result, lattice defects or crystal defects of the entire semiconductor layer constituting the light emitting element 3a formed on the upper surface of the n-type semiconductor substrate 2 are reduced. It has a function.

  The buffer layer 30a of this example is made of gallium arsenide (GaAs) and has a thickness of about 2 to 10 μm. More preferably, it is about 2 to 3 μm. The buffer layer 30a is important to be p-type containing impurities which are contained in GaAs and exhibit p-type. The reason will be explained later.

An n-type first contact layer 30b is formed on the upper surface of the buffer layer 30a. The n-type first contact layer 30b is formed by doping gallium arsenide (GaAs) with silicon (Si) or selenium (Se) as an n-type impurity, and the doping concentration is 1 × 10 ¹⁶ to 1 × 10 ²⁰ atoms. / Cm ³ and a thickness of about 0.8 to 1 μm.

In this example, silicon (Si) is doped as an n-type impurity at a doping concentration of 1 × 10 ¹⁸ to 2 × 10 ¹⁸ atoms / cm ³ . A part of the upper surface of the n-type first contact layer 30b is exposed, and this exposed part is connected to the light emitting element side first electrode pad 31A via the light emitting element side first electrode 31a. . In this example, although not shown, the light emitting element side first electrode pad 31A and the external power source are connected by wire bonding using a gold (Au) wire. Of course, it is also possible to select a wire such as an aluminum (Al) wire or a copper (Cu) wire instead of the gold (Au) wire.

  In this example, the light emitting element side first electrode pad 31A and the external power source are connected by wire bonding. However, instead of wire bonding, the electrical wiring is joined to the light emitting element side first electrode pad 31A by solder or the like. Alternatively, a gold stud bump may be formed on the upper surface of the light emitting element side first electrode pad 31A, and the electric wiring may be joined to the gold (Au) stud bump by solder or the like. The n-type first contact layer 30b has a function of reducing contact resistance with the light emitting element side first electrode 31a connected to the n-type first contact layer 30b.

  The light emitting element side first electrode 31a and the light emitting element side first electrode pad 31A are made of, for example, gold (Au) antimony (Sb) alloy, gold (Au) germanium (Ge) alloy, Ni-based alloy, or the like. Is formed with a thickness of about 0.5 to 5 μm. At the same time, the light emitting element side first electrode 31a and the light emitting element side first electrode pad 31A are formed on the insulating layer 8 formed so as to cover the upper surface of the n-type first contact layer 30b from the upper surface of the semiconductor substrate 2. Therefore, the semiconductor layers other than the semiconductor substrate 2 and the n-type contact layer 30b are electrically insulated.

The insulating layer 8 is formed of, for example, an inorganic insulating film such as silicon nitride (SiN _x ) or silicon oxide (SiO ₂ ), an organic insulating film such as polyimide, and the thickness is about 0.1 to 1 μm. Yes.

An n-type first cladding layer 30c is formed on the upper surface of the n-type first contact layer 30b, and the n-type first cladding layer 30c functions to confine holes in an active layer 30d described later. have. The n-type first cladding layer 30c is formed by doping aluminum gallium arsenide (AlGaAs) with n-type impurities such as silicon (Si) or selenium (Se), and the doping concentration is 1 × 10 ¹⁶ to 1 × 10 ^20. The thickness is about atoms / cm ³ and the thickness is about 0.2 to 0.5 μm. In this example, silicon (Si) is doped as an n-type impurity at a doping concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁷ atoms / cm ³ .

  An active layer 30d is formed on the upper surface of the n-type first cladding layer 30c. The active layer 30d emits light when carriers such as electrons and holes are concentrated and recombined. Function as. The active layer 30d is made of aluminum gallium arsenide (AlGaAs) containing no impurities, and has a thickness of about 0.1 to 0.5 μm. The active layer 30d in this example is a layer that does not contain impurities, but may be a p-type active layer that contains p-type impurities or an n-type active layer that contains n-type impurities. The band gap should be smaller than the band gap of the n-type first cladding layer 30c and the p-type second cladding layer 30e described later.

A p-type second cladding layer 30e is formed on the upper surface of the active layer 30d, and has a function of confining electrons in the active layer 30d. In the p-type second cladding layer 30e, aluminum gallium arsenide (AlGaAs) is doped with p-type impurities such as zinc (Zn), magnesium (Mg), or carbon (C), and the doping concentration is 1 × 10 ^16. The thickness is about 1 × 10 ²⁰ atoms / cm ³ and the thickness is about 0.2 to 0.5 μm. In this example, zinc (Zn) is doped as a p-type impurity at a doping concentration of 1 × 10 ^{19 to} 5 × 10 ²⁰ atoms / cm ³ .

A p-type second contact layer 30f is formed on the upper surface of the p-type second cladding layer 30e. In the p-type second contact layer 30f, aluminum gallium arsenide (AlGaAs) is doped with p-type impurities such as zinc (Zn), magnesium (Mg), or carbon (C), and the doping concentration is 1 × 10 ^16. The thickness is about 1 × 10 ²⁰ atoms / cm ³ and the thickness is about 0.2 to 0.5 μm.

  The p-type second contact layer 30f is connected to the light emitting element side second electrode pad 31B via the light emitting element side second electrode 31b. Similarly to the light emitting element side first electrode pad 31A, the light emitting element side second electrode pad 31B is electrically connected to an external power supply by wire bonding. Variations in the connection method and bonding form are the same as in the case of the first electrode pad 31A on the light emitting element side. The p-type second contact layer 30f has a function of reducing the contact resistance with the light emitting element side second electrode 31b connected to the p-type second contact layer 30f.

  A cap layer having a function of preventing oxidation of the p-type second contact layer 30f may be formed on the upper surface of the p-type second contact layer 30f. The cap layer may be formed of, for example, gallium arsenide (GaAs) that does not contain impurities, and the thickness thereof may be about 0.01 to 0.03 μm.

  The light emitting element side second electrode 31b and the light emitting element side second electrode pad 31B are made of, for example, gold (Au) or aluminum (Al) and nickel (Ni), chromium (Cr) or titanium (Ti) as an adhesion layer. It is formed of a combined AuNi, AuCr, AuTi, AlCr alloy or the like, and its thickness is about 0.5 to 5 μm. The light emitting element side second electrode 31b and the light emitting element side second electrode pad 31B are arranged on the insulating layer 8 formed so as to cover the upper surface of the p-type second contact layer 30f from the upper surface of the semiconductor substrate 2. Therefore, the semiconductor layers other than the semiconductor substrate 2 and the p-type second contact layer 30f are electrically insulated.

  In the light emitting element 3a configured as described above, by applying a bias between the light emitting element side first electrode pad 31A and the light emitting element side second electrode pad 31B, the active layer 30d emits light, and Functions as a light source.

As shown in FIG. 2B, the light receiving element 3b includes a p-type semiconductor region 32 and an n-type semiconductor substrate by providing a p-type reverse conductive semiconductor region 32 on the upper surface of the n-type semiconductor substrate 2. 2 to form a pn junction. The p-type reverse conductivity type semiconductor region 32 is formed by diffusing p-type impurities in the n-type semiconductor substrate 2 at a high concentration. Examples of the p-type impurity include zinc (Zn), magnesium (Mg), carbon (C), boron (B), indium (In), and selenium (Se), and the doping concentration is 1 × 10 ¹⁶ to 1. X10 ²⁰ atoms / cm ³ . In this example, boron (B) is diffused as a p-type impurity so that the thickness of the p-type reverse conductivity type semiconductor region 32 is about 0.5 to 3 μm.

  The p-type semiconductor region 32 is electrically connected to the light-receiving element-side first electrode pad 33A via the light-receiving-element-side first electrode 33a, and the n-type semiconductor substrate 2 includes a light-receiving-element-side second electrode pad. 33B is electrically connected.

  Since the light receiving element side first electrode 33a and the light receiving element side first electrode pad 33A are disposed on the upper surface of the n-type semiconductor substrate 2 with the insulating layer 8 interposed therebetween, they are electrically insulated from the n-type semiconductor substrate 2. Has been. On the other hand, the light receiving element side second electrode pad 33 </ b> B is disposed on the upper surface of the n-type semiconductor substrate 2.

  The light receiving element side first electrode 33a, the light receiving element side first electrode pad 33A, and the light receiving element side second electrode pad 33B are, for example, gold (Au) antimony (Sb) alloy, gold (Au) germanium (Ge) alloy, or Ni-based. Using an alloy or the like, the thickness is about 0.5 to 5 μm.

  In the light receiving element 3b configured as described above, when light enters the p-type reverse conductivity type semiconductor region 32, a photocurrent is generated by the photoelectric effect, and this photocurrent is transmitted to the light receiving element side first electrode pad 33A. It functions as a light detection part by taking out via. It is preferable to apply a reverse bias between the light receiving element side first electrode pad 33A and the light receiving element side second electrode pad 33B because the light detection sensitivity of the light receiving element 3b is increased.

  Here, the arrangement of the light emitting element side first electrode pad 31A, the light emitting element side second electrode pad 31B, the light receiving element side first electrode pad 33A, and the light receiving element side second electrode pad 33B will be described.

  In the case of this example, the light emitting element side second electrode pad 31B is disposed on the upper surface of the semiconductor substrate 2 between the light emitting element 3a and the light receiving element 3b with the insulating layer 8 interposed therebetween. The light emitting element side first electrode pad 31A and the light emitting element side second electrode pad 31B include the light receiving element side first electrode pad 33A and the light receiving element side second electrode pad 33B so as to sandwich the light emitting element 3a. The light emitting element side second electrode pad 31B is disposed so as to sandwich the light receiving element 3b. The light emitting element side first electrode pad 31A and the light receiving element side first electrode pad 33A are disposed on the upper surface of the semiconductor substrate 2 via the insulating layer 8, and the light receiving element side second electrode pad 33B is disposed on the upper surface of the semiconductor substrate 2. .

  The light emitted from the light emitting element 3a toward the light receiving element 3b is disposed by arranging the light emitting element side second electrode pad 31B on the upper surface of the semiconductor substrate 2 between the light emitting element 3a and the light receiving element 3b via the insulating layer 8. Is blocked by a wire bonding nail head bonded to the upper surface of the light emitting element side second electrode pad 31B. Therefore, it can suppress that the light which the light emitting element 3a emits is irradiated to the light receiving element 3b directly, and can implement | achieve a light receiving / emitting element with high sensing performance.

  In this example, the light emitting element side second electrode pad 31B is disposed on the upper surface of the semiconductor substrate 2 between the light emitting element 3a and the light receiving element 3b via the insulating layer 8, but the light emitting element side first electrode pad 31A, Either the light receiving element side first electrode pad 33A or the light receiving element side second electrode pad 33B may be disposed. Note that when the light receiving element side second electrode pad 33B is disposed, the light receiving element side second electrode pad 33B is disposed on the upper surface of the semiconductor substrate 2 without the insulating layer 8 interposed therebetween.

  In this example, one light emitting element 3a and one light receiving element 3b are provided, but either one or both may be plural.

  The light emitting element side second electrode pad 31B may not be positioned between the light emitting element 3a and the light receiving element 3b. In this case, the light emitting element 3a and the light receiving element 3b can be disposed close to each other, and the light receiving / emitting element 1 can be reduced in size.

  Here, the reason why it is important that the buffer layer 30a of this example includes p-type impurities and exhibits p-type will be described.

  In general, the buffer layer is provided to buffer a difference in lattice constant between the semiconductor substrate positioned above and below the buffer layer and the semiconductor layer, and therefore does not include impurities that cause lattice distortion.

  It is also considered effective to increase the resistance of the buffer layer from the viewpoint of suppressing leakage current. That is, when a bias is applied to the n-type first contact layer and the p-type second contact layer, current is prevented from flowing from the n-type first contact layer to the semiconductor substrate via the buffer layer. For this purpose, it is effective to increase the resistance of the buffer layer. In order to increase the resistance of the buffer layer, it is common to use an i layer without impurities.

  However, actually, a leakage current was generated even when the buffer layer was formed non-doped. As a result of intensive studies by the inventor on such a phenomenon, a certain amount is exceeded, contrary to the technical common sense that “impurities are not included in order to increase the resistance of the buffer layer and not to generate lattice distortion”. It has been found that the generation of leakage current (leakage current) can be suppressed by including p-type impurities and making the conductivity type of the buffer layer 30a p-type (reverse conductivity type). Hereinafter, the mechanism will be described in detail.

  The following factors can be considered for the leakage current. First, the drive current reaches the semiconductor substrate 2 through the buffer layer 30a as the light emitting element 3a is driven. Next, dark current from the light receiving element 3b flows to the light emitting element 3a side through the semiconductor substrate 2 and the buffer layer 30a.

Here, even if the resistance value is designed to be high when the buffer layer 30a is formed, the leakage current cannot be suppressed. This is presumed to be due to the light from the active layer 30d entering the buffer layer 30a and the resistance value of the buffer layer 30a changing. For this reason, even if the resistance value of the buffer layer 30a alone is adjusted, in the light emitting / receiving element 1 in which the light emitting element 3a and the light receiving element 3b are integrally formed on the semiconductor substrate 2, the generation of leakage current cannot be completely suppressed. .

  Therefore, by forming an electron barrier between the buffer layer 30a, the one-conductivity-type semiconductor substrate 2, and the first contact layer 30b, the light-emitting element 3a can be stably provided regardless of the driving of the light-emitting element 3a. And the semiconductor substrate 2 can be electrically separated. In other words, by designing the buffer layer 30a to have a reverse conductivity type, the semiconductor substrate 2, the buffer layer 30a, and the first contact layer 30b are configured to form an npn transistor or two diodes connected in opposite directions. By doing so, it was considered that the light emitting element 3a and the semiconductor substrate 2 could be electrically separated.

  Here, the inventor makes the buffer layer 30a short of one conductivity type element to have a reverse conductivity type without containing an impurity, and has a reverse conductivity type by containing a reverse conductivity type impurity. And the characteristics were compared. As a result, it has been found that the leak current cannot be suppressed in the former case, and the leak current can be suppressed for the first time in the latter case. This is presumably because the electron barrier necessary for suppressing the leakage current is insufficient in the former case, and a sufficient impurity density is required as in the latter case. Even in the latter case, it was confirmed that the quality of the semiconductor layer formed thereon was not adversely affected.

  In particular, when Zn is used as an impurity to be included in the buffer layer 30a, the leakage current can be suppressed even when the thickness of the buffer layer 30a is reduced, and the quality of the semiconductor layer formed thereon is also improved. Can be held. Further, by using Zn, even if the amount of doping is increased and the carrier density is increased, the atomic radius is not large, so that the influence of quality on the semiconductor layer formed thereon can be reduced.

  Thus, it is important that the buffer layer 30a has a reverse conductivity type by containing an impurity of a reverse conductivity type.

Note that the reverse conductivity type impurity concentration of the buffer layer 30a may be approximately the same as that of the semiconductor substrate 2 and the first contact layer 30b. This is because the electron barrier can be increased. Specifically, it may be 1.0 × 10 ¹⁶ atoms / cm ³ or more.

The dislocation density of the buffer layer 30a is preferably 1 × 10 ⁷ / cm ² or less. This is because, since the buffer layer 30a is doped with a p-type impurity in order to make the buffer layer 30a have a p-type polarity, lattice defects tend to increase in the buffer layer 30a. However, since the buffer layer 30a is provided to perform lattice matching between the semiconductor substrate 2 and the first contact layer 30b, it is formed on the buffer layer 30a as well as lattice matching if the number of lattice defects increases. The number of defects also increases in the semiconductor layers such as the first contact layer 30b, the first cladding layer 30c, the active layer 30d, the second cladding layer 30e, and the second contact layer 30f, which adversely affects the light emission characteristics of the light emitting element. It is to become.

  In the above-described example, the potential difference between the semiconductor substrate 2 and the first contact layer 30b is not mentioned, but there may be a potential difference between them. As such a potential difference, for example, by applying a bias voltage in order to make the light receiving element 3b function efficiently, the potential of the semiconductor substrate 2 rises, and the first contact layer 30b functions as a cathode electrode of the light emitting element 3a. May be connected to a reference potential.

  In such a case, with the conventional configuration, the potential of the semiconductor substrate 2 changes due to a change in the resistance value of the buffer layer 30a, thereby changing the bias voltage, which may cause an error in the output from the light receiving element 3b. is there.

  However, according to the light emitting / receiving element 1, even if there is a potential difference between the semiconductor substrate 2 and the first contact layer 30b, by interrupting the current between the semiconductor substrate 2 and the first contact layer 30b, The potential of the semiconductor substrate 2 can be kept constant. Thereby, the light receiving and emitting element 1 with high light detection accuracy can be provided.

(Modification)
In the above-described example, description has been made using an example in which no inclusion is present between the buffer layer 30a and the first contact layer 30b or between the first contact layer 30b and the first cladding layer 30c. A reflection film that reflects light having a wavelength generated at 30d toward the active layer 30d may be included. In that case, the amount of light transmitted to the buffer layer 30a can be reduced. As a result, while suppressing a decrease in the resistance value of the buffer layer 30a due to light absorption, the current passing through the buffer layer 30a can be cut off even when the resistance value is decreased. Even in this case, the light emitting / receiving element 1 with high light detection accuracy can be provided.

As such a reflection film, a so-called DBR (Distributed Bragg Reflector) in which layers having different refractive indexes having a thickness of ¼ of the wavelength of light to be reflected are laminated may be used.

(Manufacturing method of light emitting / receiving element)
Next, an example of a method for manufacturing the light emitting / receiving element 1 will be described.

First, an n-type silicon (Si) substrate doped with phosphorus (P) as an n-type impurity is prepared as the n-type semiconductor substrate 2. The impurity concentration of phosphorus (P) in this example is a concentration of 1 × 10 ¹⁷ to 2 × 10 ¹⁷ atoms / cm ³ . Examples of the n-type impurity include, in addition to phosphorus (P), nitrogen (N), arsenic (As), antimony (Sb), bismuth (Bi), and the like, and the doping concentration is 1 × 10 ¹⁶ to 1 × 10. ²⁰ atoms / cm ³ .

Next, a diffusion blocking film S (not shown) made of silicon oxide (SiO ₂ ) is formed on the n-type semiconductor substrate 2 using a conventionally known thermal oxidation method.

  An opening for forming a p-type semiconductor region 32 by a conventionally known wet etching method after applying a photoresist on the diffusion blocking film S, exposing and developing a desired pattern by a conventionally known photolithography method. Sa (not shown) is formed in the diffusion barrier film S. The opening Sa does not necessarily have to penetrate the diffusion blocking film S.

Then, a polyboron film (PBF) is applied on the diffusion barrier film S. Subsequently, boron (B) contained in the polyboron film (PBF) is diffused into the inside of the n-type semiconductor substrate 2 through the opening Sa of the diffusion blocking film S using a thermal diffusion method, A p-type semiconductor region 32 is formed. At this time, for example, the thickness of the polyboron film (PBF) is set to 0.1 to 1 μm, and thermal diffusion is performed at a temperature of 700 to 1200 ° C. in an atmosphere containing nitrogen (N ₂ ) and oxygen (O ₂ ). Thereafter, the diffusion blocking film S is removed.

Next, a natural oxide film formed on the surface of the n-type semiconductor substrate 2 is formed by heat-treating the semiconductor substrate 2 in a reaction furnace of a MOCVD (Metal-organic Chemical Vapor Deposition) apparatus. Remove. This heat treatment is performed, for example, at a temperature of 1000 ° C. for about 10 minutes.

Then, using the MOCVD method, each semiconductor layer (buffer layer 30a, first contact layer 30b, first cladding layer 30c, active layer 30d, second cladding layer 30e, second contact layer 30f) constituting the light emitting element 3a is used. ) Are sequentially stacked on the semiconductor substrate 2. Buffer layer 30
At the time of film formation of a, for example, Zn is introduced into a carrier gas introduced into the MOCVD apparatus to form a film, thereby obtaining a reverse conductivity type. Then, a photoresist is applied on the laminated semiconductor layer L (not shown), a desired pattern is exposed and developed by a conventionally known photolithography method, and then a light emitting element 3a is formed by a conventionally known wet etching method. To do. The etching is performed a plurality of times so that a part of the upper surface of the first contact layer 30b is exposed. Thereafter, the photoresist is removed.

  Next, the insulating layer 8 is formed so as to cover the exposed surface of the light emitting element 3a and the upper surface of the semiconductor substrate 2 (including the p-type semiconductor region 32) by using a conventionally known thermal oxidation method, sputtering method, plasma CVD method or the like. Form. Subsequently, after applying a photoresist on the insulating layer 8 and exposing and developing a desired pattern by a conventionally known photolithography method, a light emitting element side first electrode 31a and a light emitting element side first electrode 31a to be described later are formed by a conventionally known wet etching method. The openings for connecting the light emitting element side second electrode 31b and the light receiving element side first electrode 33a to the n-type first contact layer 30b, the p-type second contact layer 30f, and the p-type semiconductor region 32 are insulated. Layer 8 is formed. Thereafter, the photoresist is removed.

  Next, after applying a photoresist on the insulating layer 8 and exposing and developing a desired pattern by a conventionally known photolithography method, the first light emitting element side first is used by using a conventionally known resistance heating method or sputtering method. An alloy film for forming the electrode 31a, the light emitting element side first electrode pad 31A, the light receiving element side first electrode 33a, the light receiving element side first electrode pad 33A, and the light receiving element side second electrode pad 33B is formed. Then, using a known lift-off method, the photoresist is removed, and the light emitting element side first electrode 31a, the light emitting element side first electrode pad 31A, the light receiving element side first electrode 33a, and the light receiving element side first electrode pad. 33A and the light receiving element side second electrode pad 33B are formed in a desired shape. Similarly, the light emitting element side second electrode 31b and the light emitting element side second electrode pad 33B are respectively formed by the same process.

(Sensor device)
Next, the sensor device 100 including the light emitting / receiving element 1 will be described. Hereinafter, a case where the light emitting / receiving element 1 is applied to a sensor device that detects the position of the toner T (object to be irradiated) attached on the intermediate transfer belt V in an image forming apparatus such as a copier or a printer will be described as an example. I will explain.

  As shown in FIG. 3, the sensor device 100 of this example is arranged so that the surface on which the light emitting element 3 a and the light receiving element 3 b of the light receiving and emitting element 1 are formed faces the intermediate transfer belt V. Then, light is emitted from the light emitting element 3 a to the intermediate transfer belt V or the toner T on the intermediate transfer belt V. In this example, the prism P1 is disposed above the light emitting element 3a and the prism P2 is disposed above the light receiving element 3b, and the light emitted from the light emitting element 3a is refracted by the prism P1 and is transferred to the intermediate transfer belt V or the intermediate transfer belt V. It enters the toner T on the transfer belt V. The regular reflected light L2 with respect to the incident light L1 is refracted by the prism P2 and received by the light receiving element 3b. A photocurrent is generated in the light receiving element 3b according to the intensity of the received light, and this photocurrent is detected by an external device through the light receiving element side first electrode 33a and the like.

  In the sensor device 100 of this example, the photocurrent according to the intensity of the regular reflection light from the intermediate transfer belt V or the toner T can be detected as described above. Therefore, for example, it is possible to detect whether or not the toner T is located at a predetermined location according to the photocurrent value detected by the light receiving element 3b. That is, the position of the toner T can be detected. Note that the intensity of the specularly reflected light also corresponds to the density of the toner T. Therefore, the density of the toner T can be detected according to the magnitude of the generated photocurrent. Similarly, the intensity of the specularly reflected light also corresponds to the distance from the light emitting / receiving element 1 to the toner T, and therefore the distance between the light receiving / emitting element 1 and the toner T is detected according to the magnitude of the generated photocurrent. It is also possible.

  According to the sensor device 100 of this example, the above-described effects of the light emitting / receiving element 1 can be achieved.

  In the above example, the sensor device 100 is used to detect the toner concentration and distance, but surface information such as unevenness information of the irradiated object can also be sensed.

  As mentioned above, although the example of specific embodiment of this invention was shown, this invention is not limited to this, A various change is possible within the range which does not deviate from the summary of this invention.

  The light emitting / receiving element 1 shown in FIG. 1 was manufactured, and the leakage current between the light emitting element 3a and the semiconductor substrate 2 was measured.

  Specifically, an n-type Si substrate was used as the semiconductor substrate 2, and a GaAs-based semiconductor layer was stacked to form the light emitting element 3a. In the light receiving element 3 b, the reverse conductivity type semiconductor region 32 is formed by diffusing B in the semiconductor substrate 2.

Here, as an example, the buffer layer 30a has a thickness of 2.5 μm to 5.0 μm and an impurity concentration of 1.0 × 10 ¹⁶ atoms / cm ^{3 to} 1.0 × 10 ¹⁹ atoms / cm ³ .

In addition, as Comparative Example 1, the buffer layer was 2.5 μm thick and formed non-doped, and as Comparative Example 2, the buffer layer thickness was 2.5 μm to 3 μm, and the carrier density of one conductivity type (n-type) was It formed as 1.0 * 10 < ¹⁶ > atoms / cm < ³ > -1.0 * 10 < ¹⁷ > atoms / cm < ³ >. Further, as Comparative Example 3, the purpose is to alleviate the strain caused by lattice defects generated near the semiconductor substrate or the interface between the semiconductor layer and the buffer layer and the strain caused by lattice defects generated in the buffer layer after the buffer layer is formed undoped. As a result of heat treatment, a p-type product was formed by evaporating As.

  In Comparative Examples 1 to 3, a leak current was generated, whereas in the examples, no leak current was generated. In addition, when the resistance value between the 1st contact layer 30b of the light emitting element 3a concerning Example and the semiconductor substrate 2 was measured, all became overrange and it confirmed that the high resistance value was implement | achieved.

  FIG. 4 shows the results of confirming the presence or absence of leakage current by changing the thickness of the buffer layer and the carrier density of the buffer layer in the light emitting elements of the example and the comparative example. As is clear from FIG. 4, it can be confirmed that the light emitting device of the example can suppress the leakage current. Furthermore, it was confirmed that the light emitting element of the example can suppress the leakage current even when the buffer layer 30a is thin. In addition, it was confirmed that when the carrier density is low even if the buffer layer is p-type, the electron barrier becomes small and leakage current is generated.

  Moreover, the surface morphology of the surface of the light emitting element 3a in an Example and the light emitting element in the comparative example 1 was confirmed. Specifically, the magnification was set to 50 and observed with an optical microscope (Nomarski differential interference microscope). As an example, the observation sample was observed under the following four conditions with respect to the film thickness and carrier density of the buffer layer 30a.

Condition 1: film thickness 2.5 μm, carrier density 4.0 × 10 ¹⁷ atoms / cm ³
Condition 2: Film thickness 2.5 μm, carrier density 4.0 × 10 ¹⁸ atoms / cm ³
Condition 3: Film thickness: 3.0 μm, carrier density: 4.0 × 10 ¹⁷ atoms / cm ³
Condition 4: Film thickness: 3.0 μm, carrier density: 4.0 × 10 ¹⁸ atoms / cm ³
The result is shown in FIG. As is clear from FIG. 5, the surface state of the example was not different from that of Comparative Example 1. From this, it was confirmed that even when impurities were contained in the buffer layer 30a, no defects or the like were generated in the semiconductor layer formed thereon in this example.

  Further, the light emitting element 3a in the example was continuously energized, and the change rate of the light emission intensity was obtained. Specifically, the state of change in light emission intensity when energized at 10 mA for 1000 min was examined. As a result, as shown in FIG. 6, the rate of change was 6.1%, and it was confirmed that the general standard of 10% or less was satisfied. From this, it was confirmed that even when impurities were contained in the buffer layer 30a, the semiconductor layer formed thereon was not affected in this example, and the light emitting element 3a having a stable light emission intensity was realized.

DESCRIPTION OF SYMBOLS 1 Light emitting / receiving element 2 Semiconductor substrate 3a Light emitting element 3b Light receiving element 30a Buffer layer 30b First contact layer 30c First clad layer 30d Active layer 30e Second clad layer 30f Second contact layer 31A Light emitting element side first electrode pad 31B Light emitting element Side second electrode pad 31a Light emitting element side first electrode 31b Light emitting element side second electrode 32 Reverse conductivity type semiconductor region (p type semiconductor region)
33A Light-receiving-element-side first electrode pad 33B Light-receiving-element-side second electrode pad 33a Light-receiving-element-side first electrode 33b Light-receiving-element-side second electrode 100 Sensor device

Claims (5)

A semiconductor substrate of one conductivity type, a light emitting device in which a buffer layer, a first contact layer, a first cladding layer, an active layer, a second cladding layer, and a second contact layer are stacked on an upper surface of the semiconductor substrate; A light receiving element having a reverse conductivity type semiconductor region doped with an impurity of reverse conductivity type on the upper surface side;
The buffer layer has a reverse conductivity type including an impurity exhibiting a reverse conductivity type,
The light receiving and emitting element, wherein the first contact layer and the first cladding layer are of one conductivity type, and the second cladding layer and the second contact layer are of a reverse conductivity type.   The light receiving and emitting element according to claim 1, wherein the buffer layer is a GaAs-based semiconductor layer and contains Zn as the impurity. The light receiving and emitting element according to claim 1, wherein the buffer layer has a carrier density of 1 × 10 ¹⁶ / cm ² or more and a film thickness of 4 μm or less. 4. The light emitting / receiving element according to claim 1, wherein a dislocation density of the buffer layer is 1 × 10 ⁷ / cm ² or less. A sensor device using the light emitting and receiving element according to claim 1,
The irradiation object is irradiated with light from the light emitting element, and the position information, distance information, and surface information of the irradiation object are output according to the output current from the light receiving element that is output according to the reflected light from the irradiation object. And a sensor device for detecting at least one of density information.