Light-receiving device

Abstract

To provide a light receiving device which can eliminate "trade-off between operation speed and sensitivity" and can be easily manufactured, and to provide a method of manufacturing the same.SOLUTION: The light-receiving device includes a p-n junction structure in which a p-type semiconductor layer (12A, 13) and an n-type semiconductor layer (12B, 14) sandwich a light-absorbing layer (11) and a p-n junction structure in which light from the outside is transmitted to the p-n junction structure on one side of the p-n junction structure. A half mirror layer (17) that reflects light from the light absorption layer side to the light absorption layer side, and a high reflection layer (15) that is provided on the other side of the pn junction structure and reflects the light from the light absorption layer side to the light absorption layer side, A thickness W1 between the high-reflection layer and the light-absorbing layer, a thickness W2 between the half mirror layer and the light-absorbing layer, and a thickness Wabs of the light-absorbing layer are set to any one of combinations in which quantum efficiencies in the light-absorbing layer have maximum values at wavelengths of the light.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a light-receiving device in which semiconductor layers are stacked. [Background technology]

[0002] Semiconductor photodetectors are widely used in various fields that handle optical signals, and are essential devices for applications such as optical communications, optical measurement, optical spectroscopy, optical imaging, etc. Furthermore, if a semiconductor photodetector has the property of being able to achieve a high electrical saturation output, it can ensure a sufficient S / N ratio in direct OE conversion from optical signals to electrical signals (typically THz waves) even when an electrical amplifier does not exist or cannot be used.

[0003] Here, the conversion efficiency of the optical receiving device is an important indicator of the overall system performance. This is because as the frequency of the electrical signal handled after OE conversion increases, there is a constraint imposed by the "trade-off between operating speed and sensitivity" of the optical receiving device, i.e., increasing the operating speed decreases the sensitivity. If the optical signal input is constant, a decrease in optical receiving sensitivity will decrease the electrical signal output.

[0004] For example, as of 2024, photodiodes (PDs) and avalanche photodiodes (APDs) will be used as light-receiving devices in long wavelength bands (O-band, C-band, L-band, etc.) in digital optical communication systems based on 50-100 Gbaud. However, the trade-off between operating speed and sensitivity, which was not an issue in previous systems, is now becoming an issue. Specifically, to reduce the delay time of carrier travel within PD and APD elements, the optical absorption layer must be made thinner, which means that a design that ensures operating speed while suppressing sensitivity is required.

[0005] Furthermore, in the field of "THz wireless communication," which transmits signals by modulating a THz wave carrier using a laser light source, the trade-off between operating speed and sensitivity is more severely restricted than in the case of optical modulation of so-called base-band signals, because the frequency of the THz wave carrier is high.

[0006] Efforts to increase the electrical output of high-speed PDs and APDs have been underway since the 1980s in the fields of measurement technology and optical microwave technology, which require ultrafast optical-to-electrical conversion. Typical technologies include distributed traveling-wave PDs (see, for example, Non-Patent Document 1) and waveguide PDs (see, for example, Non-Patent Document 2). However, practical application of optical receiving devices using these technologies remains difficult. One reason for this is that, even though the carrier response speed of these optical receiving devices has been improved, they have issues such as large junction capacitance and difficulty in matching the speed of light and electrical signals, so their structures are not necessarily advantageous for higher speeds (100 GHz or higher to the THz range). "Improving sensitivity" to increase the output level for limited optical input remains a continuing challenge.

[0007] Here, an ultrafast PD will be described using FIGS. 1 to 3. FIG. 1 is a cross-sectional view illustrating a typical bottom-illuminated, 300 GHz-band planar PD. The PD has a wide bandgap layer (32A) and a wide bandgap semiconductor anode layer (33) on the anode side, and a wide bandgap layer (32B) and a wide bandgap semiconductor cathode layer (34) on the cathode side, sandwiching an optical absorption layer (31) with a thickness of the order of 0.1 to 0.15 μm. The PD is disposed on a semi-insulating InP substrate (38) so that the semiconductor cathode layer (34) is in contact with the semi-insulating InP substrate (38). An anode electrode (35) and a cathode electrode (36) are formed in ohmic contact with the wide bandgap semiconductor anode layer (33) and the wide bandgap semiconductor cathode layer (34), respectively.

[0008] The light is incident on the InP substrate 38. Since there is little light absorption in one-way light propagation, the anode electrode 35 is used as a metal reflective film to utilize the light reflected from the anode side.

[0009] FIG. 2 is a diagram illustrating the light receiving sensitivity of the PD in FIG. 1. The thickness W of the light absorbing layer (31) abs The change in light sensitivity (A / W) relative to the distance W1 from the light absorption layer (31) to the anode electrode (35) (the combined film thickness of the wide band gap layer (32A) and the wide band gap semiconductor anode layer (33)) is calculated for thicknesses of 0.155 μm, 0.135 μm, and 0.10 μm. Here, the anode electrode (35) is assumed to be made of Ti.

[0010] The reason why the photosensitivity is wavy is because it follows the optical standing wave (optical power) inside the element, and it does not mean that resonance absorption is occurring. abs Since the distance is short, W abs The position of moves with the change in W1, and this kind of wave change in sensitivity occurs. abs If W1=0.19 μm, which is near the peak of the waveform at 0.135 μm, the light receiving sensitivity is calculated to be approximately 0.22 A / W.

[0011] However, W abs Because there is a risk of controlling the position of W1, which determines the position of the photodiode, W1 is often set to about 0.04 to 0.06 μm, and the light receiving sensitivity is actually about 0.15 A / W. [supplement] The above means the following: The wide bandgap layer (32A) and wide bandgap semiconductor anode layer (33) that make up the thickness W1 are formed by epitaxial growth, but when attempting to form a thick film, it becomes difficult to control the film thickness. If the film is thick, such as W1 = 0.19 μm, the film thickness will deviate from the design value, making it difficult to match the peak of the light receiving sensitivity. For this reason, the film thickness W1 is often made thin, which is easy to control. [End of supplement]

[0012] Figure 3 shows the W absThis is a mapping of the photosensitivity with two parameters, W and W1. abs The change in light receiving sensitivity with respect to W1 is periodic. abs As the value of W increases, the light receiving sensitivity tends to increase. abs This is the region near the peak of the waveform where W1=0.135 μm and W2=0.19 μm.

[0013] On the other hand, structures that increase light sensitivity by incorporating a resonant cavity function into the PD structure have also been reported (see, for example, Non-Patent Documents 3, 4, and 5). However, most of these structures operate at a low response speed, use a quarter-wave multilayer film (e.g., a DBR: Distributed Bragg Reflector) incorporated into the semiconductor during growth as a highly reflective film, or have a small resonant absorption effect. In principle, these structures can increase light sensitivity. However, because DBRs are thick films, there are issues with controllability during epitaxial growth and heat dissipation methods for the device, making them difficult to realize.

[0014] Looking back at the history of PDs in the frequency range above 100 GHz, although there have been various attempts, the reality is that products have adopted PDs with normal light incidence from the backside, or PDs with an overhanging shape that effectively have backside incidence due to refraction from the side of the PD chip. The latter PD structure requires a larger junction area, so PDs with normal light incidence from the backside are advantageous in terms of speed.

[0015] Ultimately, what is required is to increase the speed and sensitivity of PD elements, while also raising the output saturation point, thereby achieving a higher electrical output level while improving the trade-off between speed and sensitivity. [Prior art documents] [Non-patent literature]

[0016] [Non-Patent Document 1] G. Rangel-Sharp et al., “Traveling-Wave Photodetectors: A Review,” The Radio Science Bulletin No 311 (December, 2004). [Non-patent document 2] Efthymios Rouvalis et al., “Traveling-wave Uni-Traveling Carrier Photodiodes for continuous wave THz generation,” Optics Express Vol. 18, Issue 11, pp. 11105-11110 (2010). [Non-patent document 3] Ravi Kuchibhotla et al., “Low-Voltage High-Gain Resonant-Cavity Avalanche Photodiode,” IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 3, NO. 4, APRIL 1991. [Non-patent document 4] Albert Chin and TY Chang, “Enhancement of Quantum Efficiency in Thin Photodiodes Through Absorptive Resonance,” JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL 9, NO. 3, MARCH 1991. [Non-Patent Document 5] P. Latzel et al., “Generation of mW level in the 300-GHz band using resonant-cavity-enhanced unitraveling carrier photodiodes,” IEEE Trans. Terahertz Sci. and Technol., vol. 7, no. 6, pp. 800-807, 2017. Summary of the Invention [Problem to be solved by the invention]

[0017] A planar PD with perpendicular light incidence on the optical absorption layer of the photodetector device is the most advantageous in terms of reducing junction capacitance. However, due to the "trade-off between operating speed and sensitivity" mentioned above, PDs designed with a thin optical absorption layer (for example, for applications with operating frequencies of 100 GHz or higher, a thickness of about 5000 Å from the optical wavelength inside the crystal) have the problem that the photodetector sensitivity is not necessarily sufficient, and a larger optical input power is required to obtain a certain output.

[0018] Therefore, in order to solve the above problems, an object of the present invention is to provide a light-receiving device and a method for manufacturing the same that can alleviate the "trade-off between operating speed and sensitivity," i.e., that minimizes deterioration in sensitivity even when the operating speed is increased, and that is easy to manufacture. [Means for solving the problem]

[0019] In order to achieve the above object, the light-receiving device of the present invention has a pn junction structure including a light absorption layer sandwiched between a highly reflective layer and a half mirror layer that allows light to enter, thereby adding a resonant cavity function.

[0020] Specifically, the light receiving device according to the present invention comprises: a pn junction structure in which a light absorption layer is sandwiched between a p-type semiconductor layer and an n-type semiconductor layer; a half mirror layer on one side of the pn junction structure that transmits external light to the pn junction structure and reflects light from the light absorption layer side toward the light absorption layer side; a highly reflective layer on the other side of the pn junction structure, the highly reflective layer reflecting the light from the light absorption layer side back to the light absorption layer side; Equipped with The thickness W1 between the high-reflectivity layer and the light-absorbing layer, the thickness W2 between the half mirror layer and the light-absorbing layer, and the thickness W abs are set to any of the combinations in which the quantum efficiency of the light absorption layer has a maximum value at the wavelength of the light. It is characterized by:

[0021] Further, a method for manufacturing a light-receiving device according to the present invention is a method for manufacturing a light-receiving device having a pn junction structure in which a p-type semiconductor layer and an n-type semiconductor layer sandwich a light absorption layer, the method comprising the steps of: forming a half mirror layer on one side of the pn junction structure, the half mirror layer transmitting external light to the pn junction structure and reflecting light from the light absorption layer side to the light absorption layer side; forming a highly reflective layer on the other side of the pn junction structure, the highly reflective layer reflecting the light from the light absorption layer side toward the light absorption layer side; and The thickness W1 between the high-reflectivity layer and the light-absorbing layer, the thickness W2 between the half mirror layer and the light-absorbing layer, and the thickness W abs and setting the value of the light absorption layer to one of the combinations that gives a maximum quantum efficiency at the wavelength of the light. It is characterized by:

[0022] This photodetector device has an optically highly reflective layer on one side of the semiconductor layer (pn junction structure) that forms the PD, and an optical half-mirror layer adjacent to it on the other side. Here, in this photodetector device, the optical half-mirror layer is not incorporated into the semiconductor layer as in the past, but is stably placed between the semiconductor layer and the host substrate (reference numeral 17 in Figure 4). Alternatively, this photodetector device may have a properly designed half-mirror layer or a protective film that is sufficiently thinner than the wavelength formed between the air layer and the semiconductor layer (reference numeral 27 in Figure 7).

[0023] Even if the light absorption layer is thinned to increase speed, the light receiving sensitivity can be increased by absorbing the light in the resonant cavity using the high-reflection layer and half-mirror layer.In addition, since the resonant cavity function is not configured using a DBR as in conventional devices, manufacturing is easier and the heat dissipation of the device can be improved.

[0024] Therefore, the present invention can alleviate the "trade-off between operating speed and sensitivity," i.e., it can provide a light-receiving device and a method for manufacturing the same that can increase the operating speed while minimizing deterioration in sensitivity and is easy to manufacture.

[0025] Here, it is preferable that the highly reflective layer also functions as an electrode.

[0026] The device may be a back-illuminated type in which the half mirror layer is formed on the host substrate side, and the highly reflective layer also functions as an electrode, or may be a front-illuminated type in which the highly reflective layer is formed on the host substrate side, and the highly reflective layer also functions as an electrode.

[0027] For example, the highly reflective layer is a metal layer, and the half mirror layer is a dielectric layer.

[0028] The above inventions can be combined as much as possible. [Effects of the Invention]

[0029] By using the "resonant cavity absorption" technology of the photodiode (PD) of this application, it is possible to increase the light receiving sensitivity of PDs, which was previously limited by the "trade-off between operating speed and sensitivity" constraint of conventional technology. In other words, it is possible to increase the electrical output under constant optical input conditions. Since the electrical output is equal to the square of (current sensitivity A / W), the greater the change in sensitivity, the greater the effect of increasing output.

[0030] The present invention can provide a light-receiving device and a method for manufacturing the same that can alleviate the "trade-off between operating speed and sensitivity," that is, can increase the operating speed without deteriorating the sensitivity as much as possible and is easy to manufacture. [Brief explanation of the drawings]

[0031] [Figure 1] 1A and 1B are diagrams illustrating the structure of a related light-receiving device. [Figure 2] FIG. 10 is a diagram illustrating the light-receiving sensitivity characteristics of a related light-receiving device. [Figure 3] FIG. 10 is a diagram illustrating the light-receiving sensitivity characteristics of a related light-receiving device. [Figure 4] 1A and 1B are diagrams illustrating the structure of a light-receiving device according to the present invention. [Figure 5] 10A and 10B are diagrams illustrating the light-receiving sensitivity characteristics of the light-receiving device according to the present invention. [Figure 6] 10A and 10B are diagrams illustrating the light-receiving sensitivity characteristics of the light-receiving device according to the present invention. [Figure 7] 1A and 1B are diagrams illustrating the structure of a light-receiving device according to the present invention. [Figure 8] 10A and 10B are diagrams illustrating the light-receiving sensitivity characteristics of the light-receiving device according to the present invention. [Figure 9] 10A and 10B are diagrams illustrating the light-receiving sensitivity characteristics of the light-receiving device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The following description of the preferred embodiments of the present invention will be given with reference to the accompanying drawings. The preferred embodiments described below are examples of the present invention, and the present invention is not limited to the preferred embodiments. In this specification and the drawings, components having the same reference numerals are intended to represent the same components.

[0033] (Embodiment 1) FIG. 4 is a cross-sectional view illustrating the light-receiving device of this embodiment. a pn junction structure in which a light absorbing layer (11) is sandwiched between p-type semiconductor layers (12A, 13) and n-type semiconductor layers (12B, 14); a half mirror layer (17) on one side of the pn junction structure that transmits external light to the pn junction structure and reflects light from the light absorption layer side to the light absorption layer side; a highly reflective layer (15) on the other side of the pn junction structure, which reflects the light from the light absorption layer side back to the light absorption layer side; Equipped with The thickness W1 between the high-reflectivity layer and the light-absorbing layer, the thickness W2 between the half mirror layer and the light-absorbing layer, and the thickness W abs are set to any of the combinations in which the quantum efficiency of the light absorption layer has a maximum value at the wavelength of the light. It is characterized by:

[0034] The light-receiving device is a back-illuminated type in which the half mirror layer (17) faces the host substrate (18), and the highly reflective layer (15) also functions as an electrode. The host substrate (18) is made of, for example, SiC. FIG. 5 is a diagram illustrating the light-receiving sensitivity of the present light-receiving device.

[0035] The photodetector device has a basic structure of a so-called p-up type, with the p-side (anode side) facing up. abs The upper layer of the pn junction is a wide bandgap layer (12A) and a wide bandgap semiconductor anode layer (13), and the lower layer is a wide bandgap layer (12B) and a wide bandgap semiconductor cathode layer (14). The pn junction structure up to this point is not significantly different from the structure of a conventional high-speed PD.

[0036] This photodetector device connects an anode electrode (15) made of a refractory metal, such as Mo, which can also function as an optically highly reflective layer, to the wide bandgap semiconductor anode layer (13). The reflectivity of refractory Mo is slightly better than that of the conventionally used Ti. The reason for using a refractory metal is to suppress reaction between the metal and the semiconductor electrode layer and ensure stable and reliable operation. Although the reflection loss is somewhat larger than that of an electrode mainly made of Au, it is on the order of about 5%, which is not a major problem for ultra-high speed applications.

[0037] A half-mirror dielectric layer (17), such as a Si3N4 film, is placed between the bottom of the wide-bandgap semiconductor cathode layer (14) and the host substrate (18). Compared to semiconductor DBR (Distributed Bragg Reflector) layers, which are conventionally used as reflective layers, the combination with the Si3N4 film results in a lower reflectivity, but the half-mirror effect is still evident. For example, when combined with SiC / Si3N4 film / InGaAsP (Eg = 0.90 eV), the reflectivity is calculated to be as low as R = 15%, so a strong resonant absorption effect cannot be expected.

[0038] However, in ultra-high-speed PDs with a thin optical absorption layer, the maximum optical responsivity is improved to 0.42 A / W, as shown in Figure 5, compared to 0.22 A / W (Figure 2) when the absorption layer thickness Wabs is 0.135 μm in a conventional PD structure (the thickness W2 is constant at 0.66 μm, which is the condition that gives the extreme value of optical responsivity).

[0039] The important point is that the same W abs , W2 combination, even if W1 changes, the operating speed does not change, so in order to improve the operating speed, abs The advantage of this is that it is possible to increase the light receiving sensitivity even when the substrate is thin, thereby mitigating the "trade-off between operating speed and sensitivity."

[0040] The thickness of the wide bandgap layer (12A) plus the wide bandgap semiconductor anode layer (13) = W1, and the thickness of the light absorption layer (11) = W abs This changes the positional relationship of the light absorbing layer (11) with the anode electrode (15), which also functions as an optically highly reflective layer. The interface of the optically highly reflective layer becomes a "node" of the optical electric field amplitude of the incident light, generating a standing wave, and the light receiving sensitivity is determined by the position and thickness of the light absorbing layer (11) relative to the standing wave. On the other hand, the thickness W2 of the wide bandgap layer (12B) plus the wide bandgap semiconductor cathode layer (14) adjusts the length of the optical cavity of the PD. abs This parameter determines the light receiving sensitivity by changing the state of the standing wave while being related to the

[0041] Figure 5 shows the sensitivity change with respect to W1 when W2 is fixed, with three W abs Value (W abs = 0.10, 0.135, 0.155 μm). abs This is a mapping of the photosensitivity with two parameters, W1 and W abs It has a clear periodic structure, and the width of the light sensitivity contour line is narrower than in the case of Figure 3. Area A in Figure 6 is the W absThis is the region near the peak of the waveform where W1=0.135 μm and W2=0.19 μm.

[0042] From Figures 5 and 6, the quantum efficiency QE, which is the light receiving sensitivity, is abs , W2 has periodic peaks (extremal values), i.e.,

number

[0043] (Embodiment 2) FIG. 7 is a cross-sectional view illustrating the light-receiving device of this embodiment. The pn junction structure is the same as the pn junction structure described in embodiment 1 (FIG. 4). This light-receiving device has a pn junction structure in which a light absorbing layer (21) is sandwiched between p-type semiconductor layers (22B, 24) and n-type semiconductor layers (22A, 23); a half mirror layer (27) on one side of the pn junction structure that transmits external light to the pn junction structure and reflects light from the light absorption layer side to the light absorption layer side; a highly reflective layer (26) on the other side of the pn junction structure that reflects the light from the light absorption layer side back to the light absorption layer side; Equipped with The thickness W1 between the high-reflectivity layer and the light-absorbing layer, the thickness W2 between the half mirror layer and the light-absorbing layer, and the thickness W abs are set to any of the combinations in which the quantum efficiency of the light absorption layer has a maximum value at the wavelength of the light. It is characterized by:

[0044] The light-receiving device is a front-illuminated type in which the highly reflective layer 26 faces the host substrate 28, and the highly reflective layer 26 also functions as an electrode. The host substrate 28 is made of, for example, SiC. FIG. 8 is a diagram illustrating the light-receiving sensitivity of the light-receiving device.

[0045] The light-receiving device is a so-called n-up type, with the cathode side facing up.abs The upper layer of the pn junction is a wide bandgap layer (22A) and a wide bandgap semiconductor cathode layer (23), and the lower layer is a wide bandgap layer (22B) and a wide bandgap semiconductor anode layer (24). This pn junction structure is not significantly different from the conventional high-speed PD structure.

[0046] This photodetector device features an anode electrode layer (26) made of a refractory metal, such as Mo, which can also function as a highly optically reflective layer, inserted between a host substrate (28) such as SiC and a wide bandgap semiconductor anode layer (24). This photodetector device is completely different from the structure of the photodetector device shown in Figure 4, in which the semiconductor electrode layer (wide bandgap semiconductor cathode layer (14)) is pulled out to the side and then contacts the cathode electrode (16). Since the anode electrode layer (26) contacts the wide bandgap semiconductor anode layer (24) in a vertical direction, the series resistance can be reduced.

[0047] The half mirror layer (27) is a thin dielectric protective film. Alternatively, the half mirror layer (27) may be a protective layer formed between the air and the semiconductor layer that is sufficiently thinner than the wavelength of light. Even though it is a thin film, its reflectance R is 31%, which is significantly higher than the reflectance R of the Si3N4 film of embodiment 1, which is 15%. A ring-shaped cathode electrode (25) is disposed around the half mirror layer (27) so as to be in contact with the pn junction structure.

[0048] Figure 8 shows the sensitivity change with respect to W1 when W2 is fixed, with three W abs Value (W abs For example, the thickness of the light absorption layer is W abs When W1 is adjusted to 0.2 μm, the peak photosensitivity increases to 0.53 A / W. This is a 2.4-fold improvement over the 0.22 A / W (Fig. 2) achieved with a conventional PD structure where the absorption layer thickness is Wabs = 0.135 μm, and corresponds to an approximately 6-fold improvement in electrical output for the same optical input intensity.

[0049] As explained in the first embodiment, the important point is that the same W abs , W2 combination, even if W1 changes, the operating speed does not change, so in order to improve the operating speed, abs The advantage of this embodiment is that it is possible to increase the light-receiving sensitivity even when the thickness of the light-absorbing layer 21 is thin, thereby eliminating the trade-off between operating speed and sensitivity. As with the first embodiment, the change in light-receiving sensitivity is determined by the relative position of the light-absorbing layer 21 with respect to the standing wave of the optical cavity that constitutes the PD.

[0050] Figure 9 shows the W abs This is a mapping of the photosensitivity with two parameters, W1 and W abs It has a clear periodic structure with respect to W1, and the width of the contour line of the light receiving sensitivity is narrower than in the case of Figure 3, and the dependence of the light receiving sensitivity on W1 is steeper. Area A in Figure 9 is the W abs This is the region near the peak of the waveform where W1=0.135 μm and W2=0.19 μm.

[0051] From Figures 8 and 9, the quantum efficiency QE, which is the light receiving sensitivity, is abs , W2 has periodic peaks (extremal values), i.e.,

number

[0052] Achieving high photosensitivity also means that the thickness of the semiconductor layer can be more tightly controlled. The photosensitivity of the photodetector device of this embodiment can be monitored after the device is almost completed, and the photosensitivity can be brought close to its maximum value at the desired wavelength by thinning the wide bandgap semiconductor cathode layer (23) by etching or adjusting the thickness of the dielectric protection film (half mirror layer (27)).

[0053] (Other embodiments) In the light-receiving devices of Embodiments 1 and 2, the semiconductor layer on the cathode side is described as being n-type and the semiconductor layer on the anode side is described as being p-type, but the present invention is not limited to this configuration. That is, the light-receiving device according to the present invention may have a configuration in which the semiconductor layer on the cathode side is replaced with p-type and the semiconductor layer on the anode side is replaced with n-type.

[0054] (Addendum) This disclosure relates to the reception of ultrafast optical signals, the generation of terahertz waves using optical signals, and photoelectric signal conversion, and more specifically, to the structure of semiconductor photodetector devices used therein, and in particular provides technology for more efficiently achieving high-speed, high-frequency operation. In other words, the objective of this invention is to improve the photosensitivity of PDs in order to increase their output power, and more directly, to easily realize resonant cavity absorption, which has been difficult to fabricate due to its complicated structure.

[0055] The means for solving the above problems according to the present invention are as follows.

[0056] [Configuration 1] A pn junction diode including, as components, a semiconductor laminated structure including a light absorbing layer, two wide band gap layers stacked above and below the light absorbing layer, and a wide band gap semiconductor anode layer and a wide band gap semiconductor cathode layer arranged adjacent to the outer sides thereof, and an anode electrode and a cathode electrode for electrically connecting the wide band gap anode layer and the wide band gap cathode layer, respectively; The pn junction diode has an optically highly reflective layer disposed on one side and an optical half mirror layer disposed on the other side adjacent to the upper and lower outer sides of the wide band gap semiconductor anode layer and the wide band gap semiconductor cathode layer, and the pn junction diode is an optically arranged pn junction diode in which an optical incident signal is introduced from the half mirror layer side, and The total thickness of the wide bandgap layer placed between the optically highly reflective layer and the light absorbing layer is W1, and the thickness of the light absorbing layer is W absWhen the total thickness of the wide band gap layer between the light absorption layer and the half mirror layer is W2, the quantum efficiency QE of the light absorption at the wavelength of the predetermined incident light signal has a maximum value, that is,

number

[0057] [Configuration 2] Within the scope of configuration 1, a semiconductor light-receiving device characterized in that the side of the half mirror layer is bonded to a host substrate that is optically transparent and has mechanical strength and high thermal conductivity, and the light reflectance and transmittance are determined by the combination of the host substrate, the half mirror layer, and the semiconductor layer adjacent to the half mirror layer.

[0058] [Configuration 3] Within the scope of configuration 1, a semiconductor light-receiving device characterized in that the optically highly reflective layer side consisting of a metal layer is bonded to a host substrate having mechanical strength and high thermal conductivity, and the optical reflectance and transmittance are determined by the combination of an air layer, the half mirror layer, and the semiconductor layer adjacent to the half mirror layer.

[0059] [effect] The photodiode (PD) structure of this invention uses the technology of "resonant cavity absorption" to significantly increase the light receiving sensitivity of PD. In high-speed PD structures, as the frequency increases (for example, 300 GHz operation), sensitivity is sacrificed to ensure operating speed, but this technology is one solution for improving this. The calculated current sensitivity for a 300 GHz structure is 2.4 times higher, which is equivalent to 6 times the electrical output. Since it can significantly increase the electrical output under limited optical input conditions, it has great practical advantages. [Explanation of symbols]

[0060] 11, 21, 31: Light absorbing layer 12A, 22A, 32A: Wide band gap layers 12B, 22B, 32B: Wide band gap layers 13, 24, 33: Wide bandgap semiconductor anode layer 14, 23, 34: Wide bandgap semiconductor cathode layer 15: Anode electrode (highly reflective layer) 16: Cathode electrode 17, 27: Dielectric layer (half mirror layer) 18, 28, 38: Host board 25: Cathode electrode 26: Anode electrode (highly reflective layer)

Claims

1. a pn junction structure in which a light absorption layer is sandwiched between a p-type semiconductor layer and an n-type semiconductor layer; a half mirror layer on one side of the pn junction structure that transmits external light to the pn junction structure and reflects light from the light absorption layer side toward the light absorption layer side; a highly reflective layer on the other side of the pn junction structure, the highly reflective layer reflecting the light from the light absorption layer side back to the light absorption layer side; Equipped with The thickness W between the highly reflective layer and the light absorbing layer １ , the thickness W between the half mirror layer and the light absorbing layer ２ and the thickness W of the light absorbing layer ａｂｓ are set to any of the combinations in which the quantum efficiency of the light absorption layer has a maximum value at the wavelength of the light. A light receiving device comprising:

2. 2. The light-receiving device according to claim 1, wherein the highly reflective layer also functions as an electrode.

3. 2. The light-receiving device according to claim 1, wherein the light-receiving device is a back-illuminated type in which the half mirror layer is formed on the host substrate side, and the highly reflective layer also functions as an electrode.

4. 2. The light-receiving device according to claim 1, wherein the light-receiving device is a front-illumination type, and the highly reflective layer is formed on the host substrate side, and the highly reflective layer also functions as an electrode.

5. 2. The light-receiving device according to claim 1, wherein the highly reflective layer is a metal layer, and the half mirror layer is a dielectric layer.

6. A method for manufacturing a light-receiving device having a pn junction structure in which a p-type semiconductor layer and an n-type semiconductor layer sandwich a light-absorbing layer, comprising: forming a half mirror layer on one side of the pn junction structure, the half mirror layer transmitting external light to the pn junction structure and reflecting light from the light absorption layer side to the light absorption layer side; forming a highly reflective layer on the other side of the pn junction structure, the highly reflective layer reflecting the light from the light absorption layer side toward the light absorption layer side; and The thickness W between the highly reflective layer and the light absorbing layer １ , the thickness W between the half mirror layer and the light absorbing layer ２ and the thickness W of the light absorbing layer ａｂｓ and setting the value of the light absorption layer to one of the combinations that gives a maximum quantum efficiency at the wavelength of the light. A method for manufacturing a light-receiving device, comprising:

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