JP2008288293A - Semiconductor photodetector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor photodetector of large quantum efficiency and less dark current, even concretely in the case of thin film thickness of an InGaAsN optical absorption layer. <P>SOLUTION: The semiconductor photodetector uses the InGaAsN layer formed on an InP substrate 1 as the optical absorption layer 5 and projecting a signal light from the reverse side to the InP substrate 1. In the semiconductor photodetector, a semiconductor multilayer-film reflecting mirror 2 for reflecting the signal light is fitted between the InP substrate 1 and the InGaAsN optical absorption layer 5. In the semiconductor photodetector, a reflecting mirror (such as one reflecting a light on an interface between a p-InGaAs layer 7 and air) further reflecting the light reflected by a semiconductor multilayer film reflecting mirror 2 is fitted further on the reverse side of the InP substrate 1 to the InGaAsN optical absorption layer 5, and the signal light is resonated between the two reflecting mirrors. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor light receiving element.

  Absorption lines of many molecules exist in the near-infrared to mid-infrared wavelength range longer than a wavelength of 1.7 μm (μm). A molecule absorbs light of a specific wavelength depending on the type of the molecule. By using spectroscopic measurement for the absorption line of the molecule, the concentration of a specific gas in a mixed gas or the concentration of a specific molecule in a substance is measured. It becomes possible to do.

  In a light receiving element using a semiconductor, the light absorption layer needs a band gap wavelength longer than the wavelength of signal light. However, considering the dark current and the light receiving sensitivity of the semiconductor light receiving element, a material having a band gap wavelength extremely longer than the wavelength of the light to be measured is not suitable for the light absorbing layer. This is because, in a light receiving element using a semiconductor, as the band gap wavelength of the light absorption layer becomes longer, the dark current increases remarkably, and the light when the incident light wavelength is shortened. The absorption coefficient in the absorption layer increases rapidly in the vicinity of the band gap wavelength of the light absorption layer, but then settles down, so even if the band gap wavelength of the light absorption layer is extremely long, the advantage for absorption is reduced. is there. For the above reason, a light receiving element using a photoconductive effect of PbS having a band gap wavelength of 3.4 μm has been mainly used for detecting light in the vicinity of a wavelength of 1.7 to 3.2 μm.

  However, in general, a light receiving element using the photoconductive effect has a slower response time than a light receiving element using the photovoltaic effect. Therefore, in recent years, instead of the photoconductive detector using PbS, a light receiving element called an extended InGaAs light receiving element using the photovoltaic effect has been developed and put into practical use. FIG. 3 is a diagram schematically showing a layer structure of the extended type InGaAs light receiving element. FIG. 3 shows a layer structure of an extended InGaAs light receiving element including an InAsP buffer layer 22, an InGaAs light absorption layer 23, and an InAsP window layer 24, the composition of which is changed stepwise on the InP substrate 21. InGaAs has an In composition ratio of 0.53 and a band gap wavelength of 1.67 μm under the condition that the lattice constant coincides with InP, and it is difficult to detect light having a wavelength of 1.7 μm or more. Since the band gap wavelength of InGaAs increases as the In composition ratio increases, the In composition ratio of the InGaAs absorption layer must be increased to 0.53 or more in order to measure light having a wavelength of 1.7 μm or more. There is. In the extended type InGaAs light receiving element of FIG. 3, a device for increasing the In composition ratio of the InGaAs light absorption layer 23 is devised.

  Specifically, an InAsP buffer layer 22 with the As composition ratio increased stepwise is formed on the InP substrate 21 by epitaxial growth, and the lattice constant of the last layer of the InAsP buffer layer 22 is changed to that of the InGaAs light absorption layer 23. Try to match. By using the InAsP buffer layer 22 in which the As composition is increased stepwise, the In composition ratio of the InGaAs light absorption layer 23 can be 0.53 or more, and the band gap wavelength is 1.67 μm or more. Even so, it is possible to suppress dislocations generated in the lower InAsP buffer layer 22 from propagating to the InGaAs light absorption layer 23. As the extended type InGaAs light receiving element, a light receiving element has been developed that can receive light with an In composition ratio of the InGaAs light absorption layer 23 exceeding 0.8 and a wavelength near 2.6 μm.

  The problem with the extended type InGaAs light receiving element as shown in FIG. 3 is that even if the dislocation propagating to the InGaAs light absorbing layer 23 can be reduced to some extent by devising the layer structure and manufacturing method of the InAsP buffer layer 22, It is extremely difficult to completely eliminate the influence of defects due to mismatching, and it is almost impossible to make the defect density comparable to that of a crystal lattice-matched to InP. The increase in defects in the light absorption layer 23 decreases the quantum efficiency in the semiconductor light receiving element and increases the dark current. In order to improve the performance of the semiconductor light receiving element, it is extremely important to suppress the generation of crystal defects.

  For this reason, InGaAsN is expected which can make the band gap wavelength longer than 1.7 μm while lattice matching with InP. In general, III-V compound semiconductors generally have a bandgap wavelength that decreases as the lattice constant decreases. InGaAsN, on the other hand, the bandgap decreases with increasing nitrogen (N) composition ratio, but the bandgap decreases. It has the feature that the wavelength increases.

  FIG. 4 shows an absorption spectrum of InGaAsN lattice-matched to InP and having an N composition ratio of 3.5%. In FIG. 4, the horizontal axis represents the wavelength of incident light, and the vertical axis represents the absorption coefficient. As apparent from FIG. 4, the band gap wavelength of InGaAsN exceeds 2.2 μm, and the band gap wavelength can be increased by further increasing the N composition ratio. Even in InGaAsNSb in which N is added to InGaAsSb, an increase in the band gap wavelength accompanying the introduction of nitrogen into the crystal has been confirmed as in InGaAsN (for example, see Non-Patent Document 1 below), and even if InGaAsNSb is used. It is possible to form an absorption layer of a light receiving element that is lattice-matched to InP and has a band gap wavelength exceeding 1.7 μm.

V. Gambin et al., “GaInNAsSb for 1.3-1.6-μm-long wavelength lasers grown by molecular beam epitaxy, IEEE Journal of Selected Topics in Quantum Electronics Vol.8, No.4,2002, pp.795-800 M. Herrera et al., “Compositon modulation in GaInNAs quantum wells: Comparison of experiment and theory”, Journal of Applied Physics, Vol. 97, 2005, p. 73705 T. Okada et al., “The role of strain and composition on the morphology of InGaAsP layers grown on <001> InP substrates”, Journal of Crystal Growth, Vol.179,1997, pp.339-348 K, Kishino et al., “Resonant cavity-enhanced (RCE) correspondings”, IEEE Journal of Quantum Electronics, Vol.27, No.8, 1991, pp.2025-2034 Q. Han et al., “1.55μm GaInNAs resonant-cavity-enhenced characterized grown on GaAs”, Applied physics Letters, Vol.87, 2005, p.11105 S. Jouba et al., “2μm resonat cavity enhanced InP / InGaAs single quantum well photo-detector”, Electronics Letters, Vol.35, No.15, 1999, pp.1272-1274 D. Vignaud et al., “Free-carrier absorption and growth temperature of highly Be-doped InGaAs in molecular beam epitaxy”, Journal of Crystal Growth, Vol.291, 2006, pp.107-111

  By the way, a general structure of a light receiving element using a semiconductor as an absorption layer is a so-called PIN type layer structure in which an undoped absorption layer is sandwiched between a p-type doped layer and an n-type doped layer. FIG. 5 is a diagram schematically showing a layer structure of a PIN type light receiving element using InGaAsN as an absorption layer.

FIG. 5 shows a basic layer structure of a light receiving element including an n-InP buffer layer 26, an InGaAsN light absorption layer 27, and a p-InGaAs contact layer 28 on an InP substrate 25. As an index of light-to-electricity conversion efficiency in a light-receiving element, it is common to use quantum efficiency as a guide, and in spectroscopic measurement near wavelengths from 1.7 to 3.2 μm, the light intensity of the light source is low, which is high Quantum efficiency is desirable. A common means for increasing the quantum efficiency is to increase the film thickness of the light absorption layer. The absorption coefficient of the light absorption layer with respect to the signal light is generally about 1000 to 10,000 inverse centimeters (cm ⁻¹ ). If the absorption coefficient is 5000 cm ⁻¹ , a film thickness of about 0.2 μm is required even if the quantum efficiency is only 5%.

  However, InGaAsN is difficult to obtain a film having a uniform composition as a feature of the material, and it is known that the composition ratio of In and N fluctuates in a direction transverse to the growth direction (for example, the above non- (See Patent Document 2). In the case where there is such a compositional modulation, the compositional modulation increases as the film thickness increases, so that it is difficult to obtain a crystal having a large film thickness (see, for example, Non-Patent Document 3 above). For this reason, when InGaAsN having a lattice match with InP and having a band gap wavelength of 1.7 μm or more is used as a light absorption layer in a semiconductor light receiving element, the film thickness of the light absorption layer cannot be increased, so that high quantum efficiency cannot be obtained. There is a problem. Further, when the thickness of the light absorption layer is increased, crystal defects are generated due to compositional modulation, which may cause an increase in dark current and a decrease in quantum efficiency.

  The present invention has been made paying attention to the unsolved problems of the prior art regarding the semiconductor light-receiving element using InGaAsN as a light absorption layer, and specifically, when the thickness of the InGaAsN light absorption layer is thin. Even so, an object of the present invention is to provide a semiconductor light-receiving element that can obtain a large quantum efficiency and also has a low dark current.

  The semiconductor light-receiving element of the first invention that achieves the above object has a semiconductor layer containing nitrogen as a light absorption layer on a semiconductor substrate, and signal light is incident on the light absorption layer from a direction opposite to the semiconductor substrate. In the semiconductor light receiving element that extracts an electric signal from the signal light, a semiconductor multilayer film that reflects the signal light is provided between the semiconductor substrate and the light absorption layer.

  The semiconductor light-receiving element of the second invention is the semiconductor light-receiving element of the first invention, wherein the semiconductor substrate is InP, and the light absorption layer has an InGaAsN layer having a wavelength corresponding to a band gap of 1.7 μm or more. Or an InGaAs NSb layer.

  According to a third aspect of the present invention, there is provided the semiconductor light receiving element according to the first or second aspect, wherein the semiconductor substrate is InP, and the semiconductor multilayer film is a semiconductor material capable of lattice matching with InP. In addition, one or more of In, Ga, and Al and one or more of As and P are included as constituent elements, and the wavelength corresponding to the band gap of the semiconductor multilayer film is 0.83 micrometer to 1. It is characterized by a 67 micrometer.

  According to a fourth aspect of the present invention, there is provided the semiconductor light-receiving element according to any one of the first to third aspects, wherein the semiconductor multilayer film is reflected on the opposite side of the semiconductor substrate with respect to the light absorption layer. A reflection mirror for further reflecting the reflected light is formed, and a resonator structure is formed between the semiconductor multilayer film and the reflection mirror with respect to the signal light.

  According to a fifth aspect of the present invention, there is provided the semiconductor light-receiving element according to the fourth aspect, wherein the reflector uses a semiconductor-gas interface, a dielectric multilayer film, or a semiconductor multilayer film. is there.

  As described above, in the semiconductor light receiving element according to the present invention, the semiconductor layer containing nitrogen such as InGaAsN formed on a semiconductor substrate such as an InP substrate is used as a light absorption layer, and signal light is opposite to the semiconductor substrate (InP substrate). In the semiconductor light-receiving element that is made incident from above, a semiconductor multilayer film (reflecting mirror) for reflecting signal light is disposed between the semiconductor substrate (InP substrate) and the light absorption layer such as InGaAsN, and the light absorption layer such as InGaAsN is further provided. On the other hand, on the opposite side of the semiconductor substrate (InP substrate), a reflecting mirror that further reflects the light reflected by the semiconductor multilayer film is installed, and the signal light is resonated between the two reflecting mirrors. By using a semiconductor light receiving element having such a resonator structure, signal light that has not been absorbed by the light absorption layer in one pass can be absorbed while resonating between reflecting mirrors. Can be dramatically increased. As a result, the conventional problem that high quantum efficiency cannot be obtained when the thickness of the InGaAsN light absorption layer is small is solved. In addition, since an increase in the thickness of the InGaAsN light absorption layer can be suppressed, generation of defects in the InGaAsN light absorption layer can be suppressed, and as a result, an increase in dark current can be avoided.

  The semiconductor light-receiving element having the resonator structure as described above has been mainly studied as a structure of a light-receiving element on a GaAs substrate so far (for example, see Non-Patent Document 4 and Non-Patent Document 5 above). In order to increase the quantum effect in the light receiving element having this resonator structure, there is no problem as long as the reflectance of the reflecting mirror on the incident side with respect to the detection light is 30% or more. The reflectance of the semiconductor multilayer film reflector to be disposed is desirably 70% or more (see Non-Patent Document 4 above). The semiconductor multilayer film can increase its reflectivity with respect to a desired wavelength as the refractive index difference between the two materials constituting the semiconductor multilayer film increases.

  However, in semiconductor materials that can be lattice-matched to InP (materials that use In, Ga, Al, As, and P as constituent elements are generally used), a wavelength of 1.3 μm used for optical fiber communication or It is difficult to give a large refractive index difference between materials for light of 1.55 μm, and as a result, it is difficult to produce a semiconductor multilayer film with high reflectivity. This is one factor that makes it difficult to manufacture a semiconductor light-receiving element having a resonator structure on an InP substrate. On the other hand, even with a material lattice-matched to InP, in the case of light having a wavelength sufficiently longer than the band gap wavelength, absorption by the semiconductor multilayer film is not a problem, and as a result, a semiconductor multilayer film having high reflectivity is obtained Becomes easier. In a semiconductor light-receiving device that combines a light absorption layer of an InGaAs single quantum well layer with a band gap wavelength of about 2 μm and a semiconductor multilayer reflector composed of InGaAs and InP lattice-matched to InP, the quantum efficiency is improved. An increased example has been reported (see Non-Patent Document 6 above). The band gap wavelength of InGaAsN can be 1.7 μm or longer, which is longer than the band gap wavelength (0.83 μm to 1.67 μm) of a material made of In, Ga, Al, As, and P lattice-matched to InP. By using InGaAsN for the light absorption layer, there is no problem of absorption in the semiconductor multilayer film reflector, and it becomes possible to produce a semiconductor multilayer film combining two semiconductor materials that can obtain a high reflectance difference.

  Incidentally, since the band gap wavelength of InGaAsN can be increased as the N composition ratio increases, the band gap wavelength of InGaAsN is not limited to the longer wavelength side. However, when considering the entire semiconductor light receiving element, absorption in the valence band occurs in other layers such as a contact layer for light having a wavelength of 4 μm or more (for example, see Non-Patent Document 7 above), Incident light quantity decreases. In a semiconductor light receiving element using a resonator structure, since absorption of all layers in the resonator becomes a problem, the practical upper limit of the wavelength is about 4 μm.

[Action]
In a light-receiving device (semiconductor light-receiving element) using InP as a substrate and InGaAsN as a light absorption layer, a reflecting mirror having a resonator structure is provided above and below the InGaAsN light absorption layer, so that signal light having a desired wavelength can be obtained. Quantum efficiency can be increased. For this reason, even if InGaAsN, which is difficult to increase the film thickness, is used for the light absorption layer, high quantum efficiency can be obtained even if the film thickness of the light absorption layer is small, and the dark current can also be reduced. .

  As described above, when the present invention is used, the quantum efficiency with respect to signal light having a wavelength of 1.7 μm or more can be increased in the semiconductor light receiving element on the InP substrate even if the thickness of the absorption layer is small. Thereby, in the near-infrared to mid-infrared wavelength region, it is possible to produce a semiconductor light-receiving element with high sensitivity and small dark current, and there is an effect that it can be applied to high-sensitivity spectroscopic measurement.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a sectional view showing a layer structure of a wafer of a semiconductor light receiving element according to a first embodiment of the present invention.

  First, the configuration of the semiconductor light receiving element according to the present embodiment will be described. As shown in FIG. 1, the semiconductor light receiving element according to the present embodiment includes an n-InP substrate 1, a semiconductor multilayer reflector 2 formed on the n-InP substrate 1, and a semiconductor multilayer reflector 2. An n-type doped InGaAsP layer 3 having a band gap wavelength of 1.3 μm formed thereon, an InGaAsP layer 4 having a band gap wavelength of 1.3 μm formed on the n-type doped InGaAsP layer 3, and an InGaAsP layer 4 The InGaAsN layer 5 serving as a light absorption layer formed on the InGaAsP layer 6, the InGaAsP layer 6 formed on the InGaAsN layer 5, and the p-type doped InGaAs layer 7 formed on the InGaAsP layer 6. In this semiconductor light-receiving element, as indicated by an arrow in FIG. 1, signal light is incident on the InGaAsN light absorption layer 5 from the opposite direction to the n-InP substrate 1, and an electric signal is extracted from the signal light.

  Here, the InGaAsN light absorption layer 5 has a nitrogen composition ratio of 0.035, an In composition ratio of 0.63, a band gap wavelength of 2.2 μm, and a film thickness of 115 nm. In addition, the semiconductor multilayer reflector 2 has an n-type doped InGaAs layer (film thickness of 148 nm) and an n-type doped InP layer (film thickness of 163 nm) as one pair, and 13 pairs are laminated to obtain a wavelength of 2.05 μm. The reflectance with respect to light was set to about 90%. Reflection at the interface between the p-type doped InGaAs layer 7 and the air (reflectance 30%) was used for the reflecting mirror on the signal light incident side.

  For comparison, a wafer without the semiconductor multilayer film reflecting mirror 2 in the layer structure of FIG.

Next, a method for manufacturing a semiconductor light receiving element according to this embodiment will be described. For the growth of the epitaxial wafer, the group III raw materials are triethylgallium (TEGa) and trimethylindium (TMIn), the group V raw materials are arsine (AsH ₃ ), phosphine (PH ₃ ), nitrogen (N ₂ ), and the dopant raw material is tin ( An organometallic molecular beam epitaxy method of Sn) and beryllium (Be) was used. At the time of manufacturing the InGaAsN layer 5, nitrogen gas was decomposed into atomic nitrogen inside the high frequency plasma source and then supplied to the substrate. The substrate temperature during growth is 470 ° C. for the InGaAsN layer 5 and 500 ° C. for the other layers. The raw material supply amount in each layer was adjusted so that the lattice constant difference with respect to InP would be less than 0.1% in each semiconductor layer constituting the semiconductor light receiving element of FIG. After forming a circular mesa with a diameter of 400 μm, a nitrogen silicon film 8 was deposited. After removing the nitrogen silicon film 8 at the center of the mesa portion, a ring-shaped p-type electrode 9 having an outer diameter of 370 μm and an inner diameter of 250 μm was formed. Finally, the InP substrate 1 was polished to form an n-type electrode 10.

  The semiconductor light-receiving device thus fabricated had a photocurrent peak wavelength of 2.053 μm and a quantum efficiency of 26% at the peak wavelength. On the other hand, in the semiconductor light-receiving element without the semiconductor multilayer reflector 2 manufactured for comparison, the quantum efficiency was about 3% at the peak wavelength of the photocurrent of 2.057 μm. The quantum efficiency increased by a factor of 5 or more due to the presence of the semiconductor multilayer reflector 2 as described above. From this, it was found that the quantum efficiency is remarkably increased by the layer between the two reflecting mirrors including the InGaAsN layer 5 operating as a resonator as described above. On the other hand, it was confirmed that the quantum efficiency increased by 3 times or more when the wavelength of the signal light was in the range of 2.01 μm to 2.08 μm, and the quantum efficiency was increased in the wavelength range close to 10 nm. It was.

  The dark current was 720 ± 50 nA at a bias voltage of −1 V regardless of the presence or absence of the semiconductor multilayer reflector 2. On the other hand, in the semiconductor light receiving element having the InGaAsN light absorption layer 5 (film thickness: 1 μm) manufactured under the same growth conditions and having no semiconductor multilayer reflector 2, the quantum efficiency of 18% was obtained, but the bias voltage − The dark current at 1V was 10 μA. The reason why the dark current is about one-tenth in the semiconductor light receiving element having the semiconductor multilayer mirror 2 is that the film thickness of the InGaAsN light absorption layer 5 is small and the occurrence of crystal defects can be suppressed.

  In the above embodiment, the semiconductor light receiving element whose quantum efficiency increases when the absorption peak wavelength is around 2.05 μm has been described. However, the absorption peak wavelength is not limited to around 2.05 μm, and lattice matching with InP is possible. 1 for the signal light having a wavelength of 1.7 μm or more longer than the band gap wavelength of the material composed of In, Ga, Al, As, and P, and the composition and film of the semiconductor multilayer mirror and other layers in FIG. By adjusting the thickness, the absorption peak wavelength of the light receiving element can be changed, and it is clear that the same effect as in the above embodiment can be obtained. The light absorption layer may be any material that is lattice-matched to InP and has a band gap wavelength longer than 1.7 μm. Similar effects can be obtained even when InGaAsNSb is used for the light absorption layer as described above. It is clear.

  In the above embodiment, the case where the semiconductor multilayer mirror is composed of InGaAs and InP is shown. However, a multilayer film composed of InGaAs and InAlAs, or a multilayer film composed of InGaAlAs and InP, etc. It is clear that the same effect can be obtained if the semiconductor material can be doped with a material capable of lattice matching with InP. Here, the material that can be lattice-matched to InP does not need to have the same lattice constant as that of InP, and includes materials having a slight difference in lattice constant, and lattice relaxation due to the difference in lattice constant occurs. It does n’t matter if you do n’t.

  In the above embodiment, n-type doped InP is used as the InP substrate. However, even when a semi-insulating substrate is used and a structure in which both the p-type electrode and the n-type electrode are taken from the surface is used. It is clear that the same effect can be obtained because the characteristics of this structure can be utilized.

  In the above-described embodiment, the case where the metalorganic molecular beam epitaxy method is used as the manufacturing method has been described. However, any growth method capable of manufacturing the InGaAsN layer may be used. The molecular beam epitaxy method, the gas source molecular beam It is clear that the same effect can be obtained by a growth method such as an epitaxy method or a metal organic vapor phase epitaxy method.

[Second Embodiment]
FIG. 2 is a cross-sectional view showing a layer structure of a wafer of a semiconductor light receiving element according to the second embodiment of the present invention.

  First, the configuration of the semiconductor light receiving element according to the present embodiment will be described. As shown in FIG. 2, the semiconductor light receiving element according to the present embodiment includes an n-InP substrate 11, a semiconductor multilayer reflector 12 formed on the n-InP substrate 11, and a semiconductor multilayer reflector 12. An n-type doped InGaAsP layer 13 having a band gap wavelength of 1.3 μm formed thereon, an InGaAsP layer 14 having a band gap wavelength of 1.3 μm formed on the n-type doped InGaAsP layer 13, and an InGaAsP layer 14 The InGaAsN layer 15 serving as a light absorption layer formed on the InGaAsP layer 16, the InGaAsP layer 16 formed on the InGaAsN layer 15, and the InP layer 17 formed on the InGaAsP layer 16. In this semiconductor light receiving element, as indicated by an arrow in FIG. 2, signal light is incident on the InGaAsN light absorption layer 5 from a direction opposite to the n-InP substrate 11 and an electric signal is extracted from the signal light.

Here, the InGaAsN light absorption layer 15 has a nitrogen composition ratio of 0.035, an In composition ratio of 0.63, a band gap wavelength of 2.2 μm, and a film thickness of 150 nm. In addition, the semiconductor multilayer mirror 12 includes an n-type doped InGaAs layer (film thickness of 145 nm) and an n-type doped InP layer (film thickness of 159 nm) as one pair, and is laminated for 10 pairs so that light with a wavelength of 2 μm is applied. The reflectivity was about 80%. For the growth of the above epitaxial wafer, the above-mentioned metalorganic molecular beam epitaxy method was used. A zinc (Zn) thermal diffusion process as shown in FIG. 1 was performed on a circular region having a diameter of 300 μm on the upper surface of the epitaxial wafer. Further, a reflecting mirror 18 made of silicon oxide (SiO ₂ ) and silicon (Si) was formed on the surface by using an electron beam evaporation method so that the reflectance with respect to light having a wavelength of 2 μm was about 75%. Thereafter, the reflecting mirror 18 was removed in a ring-shaped boundary region having an outer diameter of 300 μm and an inner diameter of 220 μm, and a p-type electrode 19 was formed in this region. Finally, the InP substrate 11 was polished to form the n-type electrode 20, thereby fabricating a planar light-receiving element.

  The semiconductor light-receiving element thus fabricated had a photocurrent peak wavelength of 1.996 μm and a quantum efficiency at the peak wavelength of 42%. The quantum efficiency obtained from the calculation is 2.2% in the structure without the multilayer reflector 12, whereas it is 49.3% in the structure with the semiconductor multilayer reflector 12, which is the result of this embodiment. Thus, it was confirmed that the quantum efficiency almost as designed was obtained. Although the quantum efficiency rapidly decreases when the signal light moves away from this peak wavelength, a quantum efficiency of 10% or more was confirmed in the wavelength range of 1.993 μm to 1.997 μm. From the above, it has been found that by increasing the reflectivity of the two reflecting mirrors constituting the resonator structure, the wavelength region where the quantum efficiency is increased is reduced, but a remarkable amplification is observed. As for dark current, a good characteristic of 120 ± 16 nA was obtained at a bias voltage of −1V.

  In the above-described embodiment, the semiconductor light receiving element using the reflecting mirror 18 made of silicon oxide and silicon as the upper reflecting mirror has been described. However, other types can be used as long as the reflecting mirror can obtain a high reflectance. It is obvious that a multilayer film using a dielectric material or a multilayer film using a semiconductor may be used, and the same effects as in the above-described embodiments can be obtained.

It is sectional drawing for demonstrating the layer structure of the semiconductor light receiving element which concerns on the 1st Example of this invention typically (Example 1). It is sectional drawing for demonstrating typically the layer structure of the semiconductor light receiving element which concerns on the 2nd Example of this invention (Example 2). It is sectional drawing for demonstrating the layer structure of an extended type InGaAs light receiver typically. It is the figure which showed the absorption spectrum in InGaAsN lattice-matched with InP. It is sectional drawing for demonstrating typically the layer structure of the optical receiver using an InGaAsN light absorption layer.

Explanation of symbols

1 n-InP substrate 2 semiconductor multilayer film reflector (n-InGaAs / n-InP)
3 n-InGaAsP
4 InGaAsP
5 InGaAsN
6 InGaAsP
7 p-InGaAs
8 silicon nitride 9 p-type electrode 10 n-type electrode 11 n-InP substrate 12 semiconductor multilayer mirror (n-InGaAs / n-InP)
13 n-InGaAsP
14 InGaAsP
15 InGaAsN
16 InGaAsP
17 InP
18 Si / SiO ₂ reflector 19 p-type electrode 20 n-type electrode 21 n-InP substrate 22 InAsP buffer layer whose composition is changed stepwise 23 InGaAs
24 InAsP
25 n-InP substrate 26 n-InP
27 InGaAsN
28 p-InGaAs

Claims (5)

In a semiconductor light receiving element that has a semiconductor layer containing nitrogen as a light absorption layer on a semiconductor substrate, and that makes signal light incident on the light absorption layer from a direction opposite to the semiconductor substrate and extracts an electric signal from the signal light ,
A semiconductor light-receiving element comprising a semiconductor multilayer film that reflects the signal light between the semiconductor substrate and the light absorption layer. The semiconductor substrate is InP;
2. The semiconductor light receiving element according to claim 1, wherein the light absorption layer is either an InGaAsN layer or an InGaAsNSb layer having a wavelength corresponding to a band gap of 1.7 μm or more. The semiconductor substrate is InP;
The semiconductor multilayer film is a semiconductor material capable of lattice matching with InP, and includes at least one of In, Ga, and Al, and at least one of As and P as constituent elements,
3. The semiconductor light receiving element according to claim 1, wherein a wavelength corresponding to a band gap of the semiconductor multilayer film is 0.83 μm to 1.67 μm.   A reflecting mirror for further reflecting the light reflected by the semiconductor multilayer film is formed on the opposite side of the semiconductor substrate with respect to the light absorption layer, and between the semiconductor multilayer film and the reflecting mirror. The semiconductor light receiving element according to claim 1, wherein the semiconductor light receiving element has a resonator structure with respect to the signal light.   The said reflecting mirror installed on the opposite side to the said semiconductor substrate with respect to the said light absorption layer uses the interface of a semiconductor and gas, or a dielectric multilayer film, or a semiconductor multilayer film, It is characterized by the above-mentioned. Semiconductor light receiving element.

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