JP2007081331A - Semiconductor light-receiving element, optical module, and optical monitoring components - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-receiving element capable of easily forming the position of a pn junction in a light-receiving layer. <P>SOLUTION: The light-receiving layer 21 of a semiconductor light-receiving element 11 is composed of a III-V compound semiconductor with absorption coefficient α in the wavelength λ<SB>SIG</SB>of an incident light L<SB>IN</SB>and has a thickness (t) of no less than 1.5 μm. A window layer 23 is composed of a second III-V compound semiconductor with a larger band gap than the first III-V compound semiconductor. The light-receiving layer 21 of the semiconductor light-receiving element 11, absorbs part of incident light that an incoming window 15 has received, and sends remainder as outgoing light L<SB>OUT</SB>from an outgoing window 17. The light-receiving layer 21 and window layer 23 are located between the outgoing window 17 and incoming window 15. In this embodiment, the light-receiving layer 21 is located between the window layer 23 and outgoing window 17. The pn junction 19 is arranged inside the light-receiving layer 21 and window layer 23. The product of the thickness (t) of the light-receiving layer 21 and the absorption coefficientα of the light-receiving layer 21 is no more than 0.1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light receiving element, an optical module, and an optical monitor component.

Non-Patent Document 1 describes a transmissive light-receiving element. The transmissive light receiving element absorbs a part of incident light and transmits the remaining light. For this reason, the thickness of the InGaAs light receiving layer is thin. The photodiode of this document has a transmittance of 35%, and the thickness of the light receiving layer is 1.1 micrometers. Since the transmittance is 35%, the proportion of light absorbed in the incident light is 65%. In order to reduce the transmittance, it is necessary to reduce the thickness of the light receiving layer. For example, in order to obtain a transmittance of 80%, the thickness of the light receiving layer needs to be 0.1 μm. This thickness is very thin. By using a thin light-receiving layer, the intensity of the signal light passing through the light-receiving element is prevented from becoming weak due to the high absorption rate of the light-receiving element.
SEI Technical Review, No. 154 (1999), pp. 27

The photodiode for optical communication uses a light receiving layer made of InGaAs or InGaAsP. Since these materials have a high absorption coefficient of about 10,000 cm ^{−1 with} respect to light in the 1.3 μm band or 1.55 μm band, a highly sensitive photodiode is provided.

  However, a transmissive photodiode requires a small absorption coefficient. That is, in order to manufacture a transmission type photodiode, it is required to use a thin light-receiving layer having a thickness of 1 μm or less in order to reduce the amount of light absorption in the light-receiving layer and enter the desired absorption rate range. . However, it is not easy to form a pn junction formed by thermal diffusion of a p-type impurity (for example, zinc) in the thin light receiving layer in the thin light receiving layer. Due to this variation, (1) the sensitivity characteristic of the photodiode varies, and (2) the element resistance of the photodiode increases.

  Accordingly, the present invention is to provide a transmissive light receiving element having a structure in which a pn junction can be easily formed in a light receiving layer, and to provide an optical module including the transmissive light receiving element. Furthermore, another object is to provide an optical monitor component including the transmission type light receiving element.

  According to one aspect of the present invention, a semiconductor light-receiving element has (a) a first surface and a second surface on the opposite side of the first surface, and exhibits a first conductivity type III-V A group III compound semiconductor substrate, a group III-V compound semiconductor light-receiving layer having a first conductivity type provided on the first surface of the group III-V compound semiconductor substrate, and (b) the group III-V compound semiconductor A second conductive type semiconductor region provided in the light receiving layer; (c) an incident window for receiving incident light; and an exit window for emitting a part of the incident light, wherein the incident window and the exit window are opposite to each other. The III-V compound semiconductor substrate is provided on the second surface or the III-V compound semiconductor light-receiving layer side surface so as to be located on the side surface, and the III-V compound semiconductor light receiving layer side surface. The absorption coefficient α of the -V group compound semiconductor light-receiving layer and 1.5 micrometer of the III-V compound semiconductor light-receiving layer The product of thickness t and above is 0.1 or less.

  According to this semiconductor light receiving element, the light receiving layer having a thickness t of 1.5 micrometers or more is used, and the product of the light receiving layer thickness t and the light absorption layer α is 0.1 or less. The light receiving element can be used for monitoring the power of the signal light, and it becomes easy to form a pn junction in the light receiving layer.

  In the semiconductor light receiving element according to the present invention, the product of the thickness t of the III-V compound semiconductor light receiving layer and the III-V compound semiconductor absorption coefficient α of the light receiving layer may be 0.04 or more. preferable.

  In this semiconductor light receiving element, if the product of the thickness t of the light receiving layer and the absorption coefficient α of the light receiving layer is 0.04 or more, the sensitivity of the light receiving element is sufficient for monitoring the power of the signal light.

In the semiconductor light receiving element according to the present invention, it is preferable that the absorption coefficient is 100 cm ⁻¹ or more at the wavelength of the incident light, and the absorption coefficient is 500 cm ⁻¹ or less at the wavelength of the incident light.

According to the semiconductor light-receiving elements, III-V compound semiconductors, because they have an absorption coefficient of 100 cm ^-1 or more 500 cm ^-1 or less in the range α at the wavelength of the incident light, without reducing the thickness of the absorption layer, pn junction Is easily formed in the light receiving layer.

  The semiconductor light receiving element according to the present invention may further include a III-V compound semiconductor window layer having a larger band gap than the III-V compound semiconductor light receiving layer on the III-V compound semiconductor light receiving layer. Thereby, dark current can be reduced.

The semiconductor light receiving device according to the present invention may further include a buffer layer provided between the III-V compound semiconductor substrate and the III-V compound semiconductor light receiving layer. The semiconductor light receiving element according to the present invention further includes a window layer provided on the III-V compound semiconductor light receiving layer, the window layer is made of InP, and the thickness of the window layer is 1 micrometer or more. The buffer layer is made of InP, and the carrier concentration of the buffer layer is 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ¹⁷ cm ⁻³ or less, and the III-V group compound semiconductor light receiving layer is made of InP. It is preferable to be made of an InGaAsP semiconductor lattice-matched to.

In this semiconductor light receiving element, when the carrier concentration of the InP buffer layer is less than 1 × 10 ¹⁶ cm ⁻³ , recombination of carriers generated by light absorption is delayed. When the carrier concentration of the InP buffer layer exceeds 1 × 10 ¹⁷ cm ⁻³ , the n-type dopant diffused from the InP buffer layer reaches the light receiving layer, and the characteristics of the light receiving element are deteriorated. As described above, when the carrier concentration of the InP buffer layer is about 10 ¹⁷ cm ⁻³ , carriers generated by light absorption are quickly recombined, which is advantageous for high-speed response of the light receiving element.

  Further, according to this semiconductor light receiving element, when an InGaAsP semiconductor is used for the light receiving layer, the light receiving layer can be lattice-matched to InP, and the fundamental absorption edge wavelength is 0.92 to 1.70 micrometers. It is possible to change freely within the range.

In the semiconductor light receiving element according to the present invention, the semiconductor region includes a window layer of a first conductivity type made of a second III-V compound semiconductor having a larger band gap than the first III-V compound semiconductor light receiving layer. The light receiving layer and the window layer are located between the exit window and the entrance window, the window layer is preferably made of InP, and the thickness of the window layer is preferably 1 micrometer or more. . The position of the pn junction and the impurity concentration can be easily controlled by the thicknesses of the window layer and the light receiving layer.

  In the semiconductor light-receiving element according to the present invention, the pn junction between the III-V compound semiconductor light-receiving layer and the second conductivity type semiconductor region is preferably formed by selective diffusion of zinc. Even if the pn junction is formed by selective diffusion of zinc, the pn junction is located in the light receiving layer.

  According to another aspect of the present invention, an optical module includes any one of the semiconductor light-receiving elements described above and an end face having an output window that is optically coupled to the incident window of the semiconductor light-receiving element and outputs signal light. A light emitting semiconductor laser; and an output connected to the semiconductor light receiving element and providing an intensity monitor signal from the semiconductor light receiving element. According to this optical module, the forward light of the semiconductor laser can be monitored.

  According to another aspect of the present invention, an optical module includes any one of the semiconductor light-receiving elements described above and a surface-emitting type semiconductor laser having an emission window that outputs signal light, and the emission of the semiconductor light-receiving element. The window, the entrance window, and the surface emitting semiconductor laser are arranged along a predetermined axis, and the entrance window of the semiconductor light receiving element is between the surface emitting semiconductor laser and the exit window of the semiconductor light receiving element. positioned. According to this optical module, the forward light of the surface emitting semiconductor laser can be monitored.

  Still another aspect of the present invention relates to an optical monitor component for monitoring signal light. The optical monitor component includes a first optical transmission line having one end and another end that are positioned on a support member and receive signal light, and one end that is positioned on the support member and provides monitored signal light. A second optical transmission line having the other end, and the second optical transmission line located on the support member between the other end of the first optical transmission line and the other end of the second optical transmission line. One of the semiconductor light receiving elements. According to this optical monitor component, there is little decrease in signal light for monitoring.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there is provided a transmissive light receiving element having a structure in which a pn junction can be easily formed in a light receiving layer, and an optical module including the light receiving element is provided. An optical monitor component including the light receiving element is provided.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the semiconductor light receiving element, the optical module, and the optical monitor component of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 is a drawing relating to a semiconductor light receiving element according to the present embodiment. The semiconductor light receiving element 11 includes a semiconductor region 13. Semiconductor region 13 includes an entrance window 15 for receiving the incident light _{L IN,} and the exit window 17 for emitting outgoing light _{L OUT,} and a pn junction 19. The semiconductor region 13 includes a light receiving layer 21 and a window layer 23. Receiving layer 21 is made III-V compound semiconductor having an absorption coefficient α at a wavelength lambda _SIG of the incident light _{L IN,} it has a 1.5 micrometer or more in thickness t. The window layer 23 is made of a second III-V compound semiconductor having a larger band gap than the first III-V compound semiconductor. The light receiving layer 21 of the semiconductor light receiving element 11 absorbs part of the incident light received by the incident window 15, and the remaining emitted light L _OUT is emitted from the emission window 17. The light receiving layer 21 and the window layer 23 are located between the exit window 17 and the entrance window 15. In the present embodiment, the light receiving layer 21 is located between the window layer 23 and the emission window 17. The pn junction 19 is provided in the light receiving layer 21 and the window layer 23. The product of the thickness t of the light receiving layer 21 and the absorption coefficient α of the light receiving layer 21 is 0.1 or less. The light receiving layer 21 and the window layer 23 are of the first conductivity type. The second conductivity type semiconductor region 25 is provided such that the light receiving layer 21 and the window layer 23 and the second conductivity type semiconductor region 25 form a pn junction 19.

  According to the semiconductor light receiving element 11, the light receiving layer 21 having a thickness t of 1.5 micrometers or more is used, and the product of the thickness t of the light receiving layer 21 and the absorption coefficient α of the light receiving layer 21 is 0.1. As described below, the light receiving element 11 can be used for monitoring the power of the signal light, and the pn junction 19 can be easily formed in the light receiving layer 21.

  In the semiconductor light receiving element 11, the semiconductor region 13 includes a light receiving layer 21 and a reverse conductivity type semiconductor region 25. The semiconductor region 25 forms the pn junction 19 with the light receiving layer 21 and the window layer 23. When the light receiving layer 21 and the window layer 23 are n-type, the semiconductor region 25 is p-type, and the semiconductor region 25 serves as an anode region.

  In the semiconductor light receiving element 11, the thickness of the window layer 23 is preferably 1 micrometer or more, and the pn junction 19 is preferably formed by selective diffusion of zinc. In the semiconductor light receiving element 11, the pn junction 19 is formed in the light receiving layer 21 even if the selective diffusion of zinc is used for forming the pn junction. This zinc is thermally diffused using, for example, the insulating film 27 having the opening 27a as a mask.

Preferably, the III-V compound semiconductor of the light receiving layer 21 includes indium, gallium, arsenic, and phosphorus as at least constituent elements. The wavelength band that includes the wavelength lambda _SIG of the incident light _{L IN,} 1.55 micrometer band, there is a 1.3 micrometer band and the like. The material of the window layer 23 is made of InP, for example. In the semiconductor light receiving element 11, the light receiving layer 21 is preferably made of an InGaAsP semiconductor lattice-matched to InP. According to this semiconductor light receiving element 11, when an InGaAsP semiconductor is used for the light receiving layer 21, the light receiving layer 21 can be lattice-matched to InP, and the fundamental absorption edge wavelength is changed from 0.92 micrometers to 1.70 micrometers. It can be changed freely within the range of meters.

In the semiconductor light receiving element 11, the semiconductor region 13 includes a buffer layer 29. The buffer layer 29 is provided between the exit window 17 and the entrance window 15. The buffer layer 29 can be made of, for example, InP. If the carrier concentration of this InP buffer layer is less than 1 × 10 ¹⁶ cm ⁻³ , recombination of carriers generated by light absorption is delayed. When the carrier concentration of the InP buffer layer exceeds 1 × 10 ¹⁷ cm ⁻³ , the n-type dopant diffused from the InP buffer layer reaches the light receiving layer 21 and the characteristics of the semiconductor light receiving element 11 are deteriorated. As described above, when the carrier concentration of the InP buffer layer is about 10 ¹⁷ cm ⁻³ , carriers generated by light absorption are quickly recombined, which is advantageous for high-speed response of the light receiving element.

  The semiconductor region 13 includes a substrate 31. A buffer layer 29 is provided on the surface 31 a of the substrate 31. An electrode 33 is provided on the back surface 31 b of the substrate 31. An antireflection film 35 such as a SiON film is provided on the emission window 17. On the entrance window 15, an antireflection film 37 such as a SiON film is provided, and an electrode 39 is located. For example, when the InP substrate 31 exhibits n conductivity and the second conductivity type semiconductor region 25 exhibits p conductivity, the electrode 33 functions as a cathode electrode and the electrode 39 functions as an anode electrode. The electrode 33 has an opening 33a through which signal light passes. The electrode 39 has an opening 35a through which signal light passes.

An example of the semiconductor light receiving element 11 is:
Substrate 31: InP substrate buffer layer 29: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Light-receiving layer 21: n-type GaInAsP (carrier concentration: 1-3 × 10 ¹⁵ cm ⁻³ )
Window layer 23: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Semiconductor region 25: zinc diffusion region anode electrode 39: AuZn
Cathode electrode 33: AuGeNi
It is.

  FIG. 2 is a drawing showing the wavelength dependence of the absorptance of an InGaAsP film having a thickness of 4 micrometers. FIG. 3 is a drawing showing the wavelength dependence of the absorption rate of an InGaAs film having a thickness of 4 micrometers.

Referring to Figure 2, in this InGaAsP film, basic to the absorption edge wavelength lambda _InGaAsP, the absorption rate indicates a substantially constant high value, greater than the fundamental absorption edge wavelength lambda _InGaAsP and the absorption rate decreases monotonously _Therefore, at a wavelength sufficiently larger than the fundamental absorption edge wavelength λ _InGaAsP , the absorptance becomes a very small value. The fundamental absorption edge wavelength λ _InGaAsP of InGaAsP having this composition is, for example, 1.42 micrometers. The wavelength λ _SIG of the signal light in the 1.55 micrometer band is longer than the fundamental absorption edge wavelength λ _InGaAsP .

Referring to FIG. 3, in this InGaAs layer, basic to the absorption edge wavelength lambda _InGaAs, the absorption rate indicates a substantially constant high value, greater than the fundamental absorption edge wavelength lambda _InGaAs and the absorption rate decreases monotonously _Therefore, at a wavelength sufficiently larger than the fundamental absorption edge wavelength λ _InGaAs , the absorptance becomes a very small value. The fundamental absorption edge wavelength λ _InGaAs of InGaAs having this composition is, for example, 1.67 micrometers. The wavelength λ _SIG of the signal light in the 1.55 micrometer band is shorter than the fundamental absorption edge wavelength λ _InGaAs .

In general, the light intensity I after light having an intensity I (0) is transmitted through a substance having an absorption coefficient α and a thickness t is expressed by the following equation.
I = I (0) × exp (−α × t)
The ratio A of light transmitted through the light receiving layer is expressed by the following equation.
A = I / I (0) = exp (−α × t)
If the product of α and t is 0.04 to 0.1, A is 0.9 to 0.96. That is, the amount of light absorbed by the light receiving layer is 4% to 10%, and 90 to 96% of light is transmitted. When 100% of light is absorbed by the light receiving layer, the sensitivity of the photodiode is 0.9 A / W to 1 A / W. When the absorptance is 4% to 10%, the sensitivity of the photodiode is 30 to 100 mW / A. This sensitivity value is sufficient for use as a power monitor. In the light receiving layer of this embodiment, the product of the absorption coefficient (α) and the thickness (t) at the wavelength of the received light is 0.04 to 0.1, and the thickness t is 1.5 micrometers or more. The absorption coefficient α of the light receiving layer is determined. According to the photodiode, the absorption coefficient of the III-V compound semiconductors for light-receiving layer α is preferably in the range of 100 cm ^-1 or more 500 cm ^-1 or less at the wavelength of the incident light. Within this range, it becomes easy to form the position of the pn junction in the light receiving layer without reducing the thickness of the light receiving layer.

Materials that can be used for the light receiving layer of a photodiode for a typical wavelength band of an optical signal are, for example,
1.55 micrometer band: GaInAsP (photoluminescence wavelength: 1.42 micrometers)
1.3 micrometer band: GaInAsP (photoluminescence wavelength: 1.17 micrometers)
It is. The photoluminescence wavelength of the light receiving layer is larger than the wavelength of the signal light received by the photodiode.

  In the prior art document (SEI technical review), InGaAsP (photoluminescence wavelength: 1.42 micrometers) is used as a photodiode in the 1.3 micrometer band.

The absorption coefficient α is from 100 cm ⁻¹ to 500 cm ⁻¹ , for example,
When α = 100, α × t = 0.04: t = 4 micrometers α = 100, α × t = 0.10: t = 10 micrometers α = 500, α × t = 0.04 Case: When t = 0.8 micrometers α = 500, α × t = 0.10: Since t = 2 micrometers, the thickness t can be increased up to a maximum of 10 micrometers.

FIG. 4A is a diagram schematically illustrating a photodiode that receives signal light having a wavelength shorter than the fundamental absorption edge wavelength of the light receiving layer. This photodiode 41 is
(Basic absorption edge wavelength: 1.67 micrometers, signal light wavelength: 1.55 micrometers)
Substrate 43: InP substrate buffer layer 45: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Light receiving layer 47: n-type GaInAs (carrier concentration: 1 to 3 × 10 ¹⁵ cm ⁻³ )
Thickness: 0.8 micrometer Window layer 51: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Semiconductor region 53: zinc diffusion region anode electrode 55: AuZn
Cathode electrode 57: AuGeNi
It is.

FIG. 4B is a schematic diagram showing a photodiode in which the P ⁺ anode region is located in the InP window layer due to shallow zinc diffusion. In this photodiode, since the p ⁺ region is formed in the InP window layer, a low concentration p layer is formed in the InP window layer, and this low concentration p layer increases the resistance. FIG. 4C is a schematic diagram showing a photodiode in which the P ⁺ anode region is located in the InP window layer for zinc diffusion at a substantially expected depth. FIG. 4D is a schematic diagram showing a photodiode in which the P ⁺ anode region is located in the InP buffer layer due to deep zinc diffusion. In this photodiode, because of the deep Zn diffusion region, the P ⁺ region exceeds the light receiving layer.
A pn junction is formed in the InP buffer layer, so that the desired sensitivity of the photodiode cannot be obtained.

FIG. 5A is a drawing schematically showing a photodiode that receives signal light having a wavelength longer than the fundamental absorption edge wavelength of the light receiving layer. This photodiode 61 is
(Basic absorption edge wavelength: 1.42 micrometers, signal light wavelength: 1.55 micrometers)
Substrate 43: InP substrate buffer layer 63: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Light receiving layer 65: n-type GaInAsP (carrier concentration: 1 to 3 × 10 ¹⁵ cm ⁻³ )
Thickness: 1.5 micrometer window layer 67: n-type InP (carrier concentration: 1 to 5 × 10 ¹⁵ cm ⁻³ )
Semiconductor region 69: zinc diffusion region anode electrode 55: AuZn
Cathode electrode 57: AuGeNi
It is.

  5B to 5D are diagrams illustrating an example of a photodiode having the structure of a light receiving element according to this embodiment. Since the photodiode shown in FIG. 5A can have a light receiving layer thicker than the photodiode shown in FIG. 4A, the sensitivity of the photodiode is large even if the zinc diffusion depth varies. There is no variation. The inventor's experiment shows that a pn junction can be stably formed in the light receiving layer using zinc diffusion if the thickness is 1.5 micrometers or more. Therefore, the product of the absorption coefficient (α) and the thickness (t) with respect to the wavelength of the received light is 0.04 to 0.1, and the thickness of the light receiving layer is set to α and 1.5 μm or more. Set t.

  As described above, since the thickness of the light receiving layer can be 1.5 micrometers or more, a pn junction by zinc diffusion can be formed in the light receiving layer. Therefore, even when the bias voltage is low, the depletion layer spreads in the light receiving layer and the expected sensitivity can be obtained.

(Second Embodiment)
FIG. 6 shows an optical module according to the second embodiment. The optical module 71 includes a semiconductor light receiving element 11 and a semiconductor laser 73. The semiconductor laser 73 has an emission window 73a that outputs the signal light L _SIG0 and generates signal light in an optical communication wavelength band such as light in the 1.55 micrometer band. In the present embodiment, the semiconductor laser 73 can be a surface emitting semiconductor laser.

The exit window 17 and the entrance window 15 of the semiconductor light receiving element 11 and the semiconductor laser 73 are arranged along a predetermined axis Ax. The incident window 15 of the semiconductor light receiving element 11 is located between the semiconductor laser 73 and the emission window 17 of the semiconductor light receiving element 11. This arrangement is provided, for example, by the following structure. The semiconductor laser 73 is provided on the stem 75. A support member 79 is provided on the stem 75 so as to cover the semiconductor laser 73. On the support member 79, the semiconductor light receiving element 11 is located. The support member 79 has an opening 79 a through which the signal light L _SIG from the emission window 73 a of the semiconductor laser 73 passes. The signal light L _SIG0 is incident on the incident window 15 of the semiconductor light receiving element 11. The light receiving layer of the semiconductor light receiving element 11 absorbs a part of the signal light L _SIG0 to generate a signal for monitoring, and the remainder of the signal light L _SIG0 is emitted from the emission window 17 of the semiconductor light receiving element 11. . A lens holder 77 is provided on the stem 75, and the lens holder 77 holds a lens 77a. The stem 75 and the lens holder 77 form a cavity for hermetically sealing the semiconductor laser 73 and the semiconductor light receiving element 11. The semiconductor laser 73, the semiconductor light receiving element 11, and the lens 77 are arranged along a predetermined axis Ax. With this arrangement, the exit window 17 of the semiconductor light receiving element 11 is optically coupled to the lens 77. Therefore, the signal light L _SIG1 from the emission window 17 of the semiconductor light receiving element 11 is incident on the lens 77a. An output 81 of the optical module 71 is connected to the semiconductor light receiving element 11 and provides an intensity monitor signal _SMON1 from the semiconductor light receiving element 11. As the semiconductor laser 73, an edge emitting semiconductor laser can be used instead of the surface emitting semiconductor laser.

  According to this optical module, the front light from the semiconductor laser can be monitored.

(Third embodiment)
FIG. 7 is a view showing an optical monitor component according to the third embodiment. The optical monitor component 91 includes a first optical transmission path 93, a second optical transmission path 95, and the semiconductor light receiving element 11. The first optical transmission path 93 is positioned on the support member 97 and has one end 93a and the other end 93b that receive the signal light L _SIG2 . The second optical transmission line 95 has one end 95a and the other end 95b that are positioned on the support member 97 and provide the monitored signal light L _SIG3 . The semiconductor light receiving element 11 is positioned between the other end 93 b of the first optical transmission path 93 and the other end 95 b of the second optical transmission path 95 on the support member 97. The first optical transmission line 93 and the second optical transmission line 95 can be, for example, optical fibers.

The support member 97 includes a support portion 97a for supporting the first optical transmission path 93, and the optical fiber as an example of the first optical transmission path 93 includes the first support surface 94a and the second optical transmission path 93. It is supported by the support surface 94b. The support member 97 includes a support portion 97b for supporting the second optical transmission path 95, and the optical fiber as an example of the second optical transmission path 95 includes the first support surface 96a and the second optical transmission path 95. It is supported by the support surface 96b. The first support part 97a and the second support part 97b can be grooves including two support surfaces, for example, V-shaped grooves. Further, the support member 97 has a support portion 97 c for positioning the semiconductor light receiving element 11 between the other end 93 b of the first optical transmission path 93 and the other end 95 b of the second optical transmission path 95 on the support member 97. In the present embodiment, the support portion 97c is a first for positioning the semiconductor light receiving element 11 between the other end 93b of the first optical transmission path 93 and the other end 95b of the second optical transmission path 95. It has a side surface 98a, a second side surface 98b, and a bottom surface 98c. By this support portion 97 c, the incident window of the semiconductor light receiving element 11 is optically coupled to the other end 93 b of the first optical transmission path 93. Further, the exit window of the semiconductor light receiving element 11 is optically coupled to the other end 95 b of the second optical transmission path 95. The optical monitor component 91 provides a monitor signal _IMON2 corresponding to the intensity of the signal light transmitted through the optical transmission lines 93 and ₉₅ . Thereby, the optical monitor component 91 can monitor the signal light S _SIG2 . The signal light L _SIG2 is provided to the control unit 99. An optical amplifier 101 is optically coupled to the optical monitor component 91. The control unit 99 generates S _CON that controls the optical amplifier 101 in response to the monitor signal I _MON2 .

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. For example, this element structure can be realized by using a Fe-doped semi-insulating InP substrate. In this structure, electrodes can be formed on the same side, and mounting becomes easy. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1 is a drawing relating to a semiconductor light receiving element according to the present embodiment. FIG. 2 is a drawing showing the wavelength dependence of the absorptance of an InGaAsP film having a thickness of 4 micrometers. FIG. 3 is a drawing showing the wavelength dependence of the absorption rate of an InGaAs film having a thickness of 4 micrometers. FIG. 4A is a diagram schematically illustrating a photodiode that receives signal light having a wavelength shorter than the fundamental absorption edge wavelength of the light receiving layer. FIG. 4B is a schematic diagram showing a photodiode in which the P + anode region is located in the InP window layer due to shallow zinc diffusion. FIG. 4C is a schematic diagram showing a photodiode in which the P + anode region is located in the InP window layer for zinc diffusion at a substantially expected depth. FIG. 4D is a schematic diagram showing a photodiode in which the P + anode region is located in the InP buffer layer for deep zinc diffusion. FIG. 5A is a drawing schematically showing a photodiode that receives signal light having a wavelength longer than the fundamental absorption edge wavelength of the light receiving layer. 5B to 5D are diagrams illustrating an example of a photodiode having the structure of a light receiving element according to this embodiment. FIG. 6 shows an optical module according to the second embodiment. FIG. 7 is a view showing an optical monitor component according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Semiconductor light receiving element, 13 ... Semiconductor region, _LIN ... Incident light, _LOUT ... Outgoing light, 15 ... Incident window, 17 ... Outgoing window, 19 ... pn junction, 21 ... Light receiving layer, 23 ... Window layer, (lambda) _SIG ... wavelength of incident light, 25 ... second conductive type semiconductor region, 27 ... insulating film, 29 ... buffer layer, 31 ... substrate, 33 ... electrode, 35 ... antireflection film, 37 ... antireflection film, 39 ... electrode, λ _InGaAsP , λ _InGaP ... fundamental absorption edge wavelength, α ... absorption coefficient of the light receiving layer, t ... thickness of the light receiving layer, 41 ... photodiode, 43 ... substrate, 45 ... buffer layer, 47 ... light receiving layer, 51 ... window layer, 53 ... Semiconductor region, 55 ... Anode electrode, 57 ... Cathode electrode, 61 ... Photodiode, 63 ... Buffer layer, 65 ... Light receiving layer, 67 ... Window layer, 69 ... Semiconductor region, 71 ... Optical module, 73 ... Semiconductor laser, L _SIG0 Signal light 73a Semiconductor laser exit window 75 Stem 79 Support member 77 Lens holder 77a Lens 91 Light monitor component 93 First light transmission path 95 Second light Transmission path 97: Support member, 93a, 93b ... End of first optical transmission path, 95a, 95b ... End of second optical transmission path, 97a, 97b, 97c ... Support section, 94a, 94b, 96a, 96b ... support surface, 98a, 98b ... side, 98c ... bottom, 99 ... _{controller, I MON2 ...} monitor signal, 101 ... optical amplifier, _{S CON ...} control signal

Claims (10)

A group III-V compound semiconductor substrate having a first surface and a second surface opposite to the first surface and exhibiting a first conductivity type;
A III-V compound semiconductor light receiving layer provided on the first surface of the III-V compound semiconductor substrate and exhibiting a first conductivity type;
A second conductivity type semiconductor region provided in the III-V compound semiconductor light-receiving layer;
An incident window for receiving incident light and an exit window for emitting a part of the incident light,
The entrance window and the exit window are provided on the second surface of the group III-V compound semiconductor substrate or the surface on the side of the group III-V compound semiconductor light receiving layer so that the surfaces are opposite to each other. And
The product of the absorption coefficient α of the III-V compound semiconductor light-receiving layer at the wavelength of the incident light and the thickness t of 1.5 μm or more of the III-V compound semiconductor light-receiving layer is 0.1 or less. A semiconductor light receiving element characterized by the above.   The product of the thickness t of the III-V compound semiconductor light-receiving layer and the absorption coefficient α of the III-V compound semiconductor light-receiving layer is 0.04 or more. Semiconductor light receiving element. The absorption coefficient is 100 cm ⁻¹ or more at the wavelength of the incident light,
3. The semiconductor light receiving element according to claim 1, wherein the absorption coefficient is 500 cm ⁻¹ or less at a wavelength of the incident light. 4.   The III-V compound semiconductor light receiving layer further comprises a III-V compound semiconductor window layer having a larger band gap than the III-V compound semiconductor light receiving layer. The semiconductor light receiving element described in any one of.   The semiconductor according to claim 1, further comprising a buffer layer provided between the III-V compound semiconductor substrate and the III-V compound semiconductor light receiving layer. Light receiving element. Further comprising a window layer provided on the III-V compound semiconductor light receiving layer,
The window layer is made of InP;
The window layer has a thickness of 1 micrometer or more;
The buffer layer is made of InP,
The buffer layer has a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or more, 1 × 10 ¹⁷ cm ⁻³ or less,
6. The semiconductor light receiving element according to claim 5, wherein the III-V compound semiconductor light receiving layer is made of an InGaAsP semiconductor lattice-matched to InP.   7. The pn junction between the III-V compound semiconductor light receiving layer and the second conductivity type semiconductor region is formed by selective diffusion of zinc. 8. Semiconductor light receiving element. A semiconductor light receiving element according to any one of claims 1 to 7;
An edge emitting semiconductor laser having an exit window optically coupled to the entrance window of the semiconductor light receiving element and outputting signal light;
An optical module comprising: an output connected to the semiconductor light receiving element and providing an intensity monitor signal from the semiconductor light receiving element. A semiconductor light receiving element according to any one of claims 1 to 7;
A surface emitting semiconductor laser having an exit window for outputting signal light,
The exit window and the entrance window of the semiconductor light receiving element and the surface emitting semiconductor laser are arranged along a predetermined axis,
The optical module, wherein the entrance window of the semiconductor light receiving element is located between the surface emitting semiconductor laser and the exit window of the semiconductor light receiving element. An optical monitor component for monitoring signal light,
A first optical transmission line positioned at the support member and having one end and the other end for receiving signal light;
A second optical transmission line having one end and the other end positioned on the support member and providing monitored signal light;
It is located on the said supporting member between the said other end of the said 1st optical transmission path, and the said other end of the said 2nd optical transmission path, It was described in any one of Claims 1-7 An optical monitor component comprising a semiconductor light receiving element.

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