Light emitting device

Abstract

[Problem] To provide a light emitting device that is, while being provided with a photodiode provided in a vertical cavity, capable of inhibiting degradation of laser characteristics of a VCSEL. [Solution] A light emitting device according to the present disclosure is provided with a first reflecting portion, a second reflecting portion, a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type that are provided between the first reflecting portion and the second reflecting portion, an active layer that is provided between the first semiconductor layer and the second semiconductor layer and generates light having a first wavelength through application of electric power to the first and second semiconductor layers, and an avalanche photodiode layer provided in the first reflecting portion.

Description

Light-emitting device 【0001】 This disclosure relates to a light-emitting device. 【0002】 Vertical cavity surface-emitting lasers (VCSELs) are sometimes configured as ViPs (VCSELs with integrated photodiodes) by integrating a photodiode to measure the intensity of the laser light. The photocurrent measured by the photodiode is used as a feedback signal. 【0003】 Japanese Patent Publication No. 2011-520280, Japanese Patent Publication No. 2013-502067, Japanese Patent Publication No. 2001-308368, Japanese Patent Publication No. 2009-283854 【0004】 However, there was a problem in that the photodiode placed inside the vertical resonator affected the laser characteristics. 【0005】 Therefore, this disclosure provides a light-emitting device that can suppress the degradation of the laser characteristics of a VCSEL while providing a photodiode within a vertical resonator. 【0006】 A light-emitting device according to one aspect of the present disclosure comprises a first reflector, a second reflector, a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type provided between the first reflector and the second reflector, an active layer provided between the first semiconductor layer and the second semiconductor layer that generates light of a first wavelength by applying power to the first and second semiconductor layers, and an avalanche photodiode layer provided within the first reflector. 【0007】 The first reflective section includes a first reflective layer of a first conductivity type and a second reflective layer of a second conductivity type, and the avalanche photodiode layer is provided between the first reflective layer and the second reflective layer. 【0008】 The avalanche photodiode layer includes a photoelectric conversion layer that converts light of a first wavelength into electricity to generate an electric charge, and a multiplication layer that multiplies the charge by an avalanche. 【0009】 The photoelectric conversion layer and the multiplier layer are stacked in this order in the first direction from the first reflective layer to the second reflective layer. 【0010】 The avalanche photodiode layer is provided between the photoelectric conversion layer and the multiplier layer and further includes a transition layer that transfers the charge generated in the photoelectric conversion layer to the multiplier layer. 【0011】 The photoelectric conversion layer, transition layer, and multiplier layer are stacked in this order in the first direction from the first reflective layer to the second reflective layer. 【0012】 The multiplier layer includes a first multiplier semiconductor layer of the first conductivity type and a second multiplier semiconductor layer of the second conductivity type. 【0013】 The first multiplier semiconductor layer and the second multiplier semiconductor layer are stacked in this order in the first direction from the first reflective layer to the second reflective layer. 【0014】 The multiplier layer multiplies the current from the photoelectric conversion layer by avalanche multiplication. 【0015】 The light-emitting device further comprises a first electrode electrically connected to a first semiconductor layer, a second electrode electrically connected to a second semiconductor layer, and a third electrode electrically connected to a first reflective layer. 【0016】 A voltage that is a reverse bias to the avalanche photodiode layer is applied between the first electrode and the third electrode. 【0017】 The first reflective section is made of a semiconductor material, and the second reflective section is made of a dielectric material. 【0018】 The light-emitting device further comprises a third semiconductor layer provided on the second semiconductor layer between the second reflecting portion and the second semiconductor layer, having a higher impurity concentration of the second conductivity type than the second semiconductor layer, and a fourth semiconductor layer of the first conductivity type provided on the third semiconductor layer, forming a tunnel junction with the third semiconductor layer. 【0019】 The second reflective section includes an uneven layer having an uneven shape on the light-emitting surface from which light from the active layer is emitted. 【0020】 The light-emitting device further comprises a fifth semiconductor layer provided on a fourth semiconductor layer, the fifth semiconductor layer including a conductive region sandwiched between a first reflector and a second reflector, and an impurity implant region provided around the conductive region. 【0021】 The light-emitting device further comprises a transparent conductive film provided on the conductive region and the impurity implant region. 【0022】 The third and fourth semiconductor layers are provided between the second semiconductor layer and the second reflective portion, and an air gap is provided around the third and fourth semiconductor layers. 【0023】 The active layer contains quantum dots. 【0024】 Multiple stacked structures, each composed of first to fourth semiconductor layers and an active layer, are provided between the first and second reflective sections. 【0025】 The first reflective portion is provided on an InP substrate and is a laminated film of multiple AlGaInAs layers and multiple InP layers, while the second reflective portion is a laminated film of multiple silicon oxide films and multiple titanium oxide films. 【0026】A cross-sectional view showing an example of the configuration of a light-emitting device according to the first embodiment. A cross-sectional view showing the configuration of the avalanche photodiode layer, the first reflective layer, and the second reflective layer. A graph showing the characteristics of a VCSEL with embedded photodiodes. A graph showing the characteristics of a VCSEL with embedded photodiodes. A graph showing the position of the avalanche photodiode layer with respect to the standing wave of the laser light generated by the VCSEL. A cross-sectional view showing an example of a method for manufacturing a light-emitting device according to the first embodiment. A cross-sectional view showing a method for manufacturing a light-emitting device, following Figure 6. A cross-sectional view showing a method for manufacturing a light-emitting device, following Figure 7. A cross-sectional view showing a method for manufacturing a light-emitting device, following Figure 8. A cross-sectional view showing a method for manufacturing a light-emitting device, following Figure 9. A cross-sectional view showing a method for manufacturing a light-emitting device, following Figure 10. A cross-sectional view showing an example of the configuration of a light-emitting device according to the second embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the third embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the fourth embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the fifth embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the sixth embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the seventh embodiment. A cross-sectional view showing an example of the configuration of a light-emitting device according to the eighth embodiment. A cross-sectional view showing an example of the configuration of the light-emitting device according to the ninth embodiment. A cross-sectional view showing an example of the configuration of the light-emitting device according to the tenth embodiment. A cross-sectional view showing an example of the configuration of the light-emitting device according to the eleventh embodiment. A cross-sectional view showing an example of the configuration of the light-emitting device according to the twelfth embodiment. A cross-sectional view showing an example of the configuration of the light-emitting device according to the thirteenth embodiment. A block diagram showing an example of the schematic configuration of the vehicle control system. An explanatory diagram showing an example of the installation positions of the external information detection unit and the imaging unit. 【0027】 The following describes specific embodiments of this technology with reference to the drawings. The drawings are schematic or conceptual, and the proportions of each part may not necessarily be the same as those of actual objects. In the specification and drawings, elements similar to those described above are denoted by the same reference numerals with respect to previously shown drawings, and detailed explanations are omitted as appropriate. 【0028】(First Embodiment) Figure 1 is a cross-sectional view showing an example of the configuration of a light-emitting device 1 according to the first embodiment. The light-emitting device 1 comprises a substrate 10, a first reflector 20, an avalanche photodiode layer 120, a first semiconductor layer 30, an active layer 40, a second semiconductor layer 50, a third semiconductor layer 60, a fourth semiconductor layer 70, a fifth semiconductor layer 80, a semiconductor layer 85, a second reflector 90, a first electrode 100, a second electrode 110, and a third electrode 115. The light-emitting device 1 is, for example, a semiconductor light-emitting device such as a VCSEL. The light-emitting device 1 emits light by injecting electrons and holes from the first and second semiconductor layers 30 and 50 into the active layer 40 by applying power between the first electrode 100 and the second electrode 110, and by recombining the electrons and holes in the active layer 40. Light is reflected and resonates between the first reflector 20 and the second reflector 90, and is emitted as laser light from the second reflector 90 side. At this time, the avalanche photodiode layer 120 is reverse-biased between the first electrode 100 and the third electrode 115, and the photoelectrically converted charge is avalanche multiplied to generate a photocurrent. 【0029】 The substrate 10 may be a semiconductor substrate such as an n-type InP substrate. 【0030】 The first reflector 20 is a so-called DBR (Distributed Bragg Reflector) and is constructed by alternately stacking multiple materials with different refractive indices. For example, the first reflector 20 has a stacked structure of multiple epitaxially grown semiconductor materials (for example, a stacked structure of AlGaInAs and InP). The first reflector 20 includes an n-type first reflective layer 20a and a p-type second reflective layer 20b. 【0031】 The avalanche photodiode layer 120 is provided within the first reflector 20. The avalanche photodiode layer 120 is provided between the n-type first reflector layer 20a and the p-type second reflector layer 20b. The configuration of the avalanche photodiode layer 120 will be described in detail with reference to Figure 2. 【0032】The first semiconductor layer 30 is located between the first reflector 20 and the second reflector 90 and is a cladding layer provided on the first reflector 20. The first semiconductor layer 30 is made of, for example, n-type InP. 【0033】 The active layer 40 is provided between the first semiconductor layer 30 and the second semiconductor layer 50. The active layer 40 emits light when power is applied to the first and second semiconductor layers 30 and 50, causing electrons from the first semiconductor layer 30 and holes from the second semiconductor layer 50 to recombine inside the active layer 40. The active layer 40 generates light of a first wavelength. The active layer 40 is made of a multiple quantum well layer (MQW) such as AlGaInAs / AlGaInAs or GaInAsP / GaInAsP. The wavelength of the AlGaInAs / AlGaInAs multiple quantum well layer can be arbitrarily controlled by the material composition and film thickness. It is preferable to introduce mutually opposing strains into the multiple quantum well layer and the barrier layer. In this case, for example, the magnitude of the strain can be around 1%, and the number of quantum wells can be 4 to 8. 【0034】 The second semiconductor layer 50 is located between the first reflector 20 and the second reflector 90 and is a cladding layer provided on the active layer 40. The second semiconductor layer 50 is made of p-type InP, which has the opposite conductivity to the first semiconductor layer 30. Therefore, by applying a negative voltage to the first electrode 100 and a positive voltage to the second electrode 110, electrons are supplied from the first semiconductor layer 30 to the active layer 40, and holes are supplied from the second semiconductor layer 50 to the active layer 40. 【0035】 The third semiconductor layer 60 is provided on the second semiconductor layer 50. The third semiconductor layer 60 is located between the second reflector 90 and the second semiconductor layer 50. The third semiconductor layer 60 is made of a p-type semiconductor, for example, p-type AlInAs. The p-type impurity concentration of the third semiconductor layer 60 is higher than that of the second semiconductor layer 50. 【0036】The fourth semiconductor layer 70 is provided on the third semiconductor layer 60. The fourth semiconductor layer 70 is also located between the second reflector 90 and the second semiconductor layer 50. The fourth semiconductor layer 70 is made of an n-type semiconductor, for example, n-type InP. The n-type impurity concentration of the fourth semiconductor layer 70 is higher than that of the fifth semiconductor layer 80. 【0037】 The third and fourth semiconductor layers 60 and 70 constitute a buried tunnel junction (BTJ) with a high impurity concentration. Hereinafter, the third and fourth semiconductor layers 60 and 70 will also be referred to as BTJs 60 and 70. The current between electrodes 100 and 110 flows concentrated in the BTJs 60 and 70, causing them to narrow. As a result, the BTJs 60 and 70 can promote light emission in the active layer 40 directly beneath them. Furthermore, at the contact surface between the sides of the BTJs 60 and 70 and the fifth semiconductor layer 80, the difference in refractive index between these materials causes the light to narrow in the BTJs 60 and 70 as well. 【0038】 When viewed from the stacking direction (Z direction), the BTJs 60 and 70 overlap with the second reflector 90. The stacking direction (Z direction) is also the direction in which current flows through the BTJs 60 and 70, and the direction in which light resonates between the first reflector 20 and the second reflector 90. 【0039】 The fifth semiconductor layer 80 is provided on the second semiconductor layer 50 and the BTJs 60 and 70. The fifth semiconductor layer 80 covers the BTJs 60 and 70. The fifth semiconductor layer 80 is made of an n-type semiconductor, for example, n-type InP. The n-type impurity concentration of the fifth semiconductor layer 80 is lower than that of the fourth semiconductor layer 70. Therefore, no current flows at the junction between the fifth semiconductor layer 80 and the second semiconductor layer 50. 【0040】 The semiconductor layer 85 is provided on the fifth semiconductor layer 80. The semiconductor layer 85 is made of an n-type semiconductor, for example, InGaAs. The semiconductor layer 85 is provided so that the second electrode 110 can connect to the fifth semiconductor layer 80 with low resistance. The semiconductor layer 85 is removed between the BTJs 60 and 70 through which the laser light passes and the second reflector 90 in order to suppress the absorption loss of the laser light. 【0041】The second reflector 90 is located above (in the Z direction) the BTJs 60 and 70. The second reflector 90 is a DBR and is constructed by alternately stacking multiple materials with different refractive indices. For example, the second reflector 90 has a stacked structure of multiple dielectric materials (for example, SiO ２ and TiO ２ It has a laminated structure. That is, the first reflector 20 is a semiconductor DBR made of a semiconductor material, and the second reflector 90 is a dielectric DBR made of a dielectric material. In this embodiment, the laser light generated in the resonator between the first reflector 20 and the second reflector 90 is emitted from the second reflector 90. 【0042】 The first electrode 100 is provided on the first semiconductor layer 30 and is electrically connected to the first semiconductor layer 30. The first electrode 100 is made of a conductive metal such as Ti, Pt, Au, a multilayer film of AuGe and Ni and Au, or a multilayer film of PdGe, Ni and Au. The first electrode 100 is provided around the active layer 40. The first electrode 100 is electrically insulated from components other than the first semiconductor layer 30. The first electrode 100 functions as a common cathode for the laser diode and avalanche photodiode layer 120, which include the active layer 40. 【0043】 The second electrode 110 is provided on a semiconductor layer 85 above the fifth semiconductor layer 80 and is electrically connected to the fifth semiconductor layer 80. Furthermore, the second electrode 110 is electrically connected to the second semiconductor layer 50 via BTJs 60 and 70. The second electrode 110 is also made of a conductive metal, such as Ti, Pt, Au, a multilayer film of AuGe and Ni and Au, or a multilayer film of PdGe, Ni and Au. The second electrode 110 may be made of the same material as the first electrode 100. The second electrode 110 is provided around the second reflector 90. The second electrode 110 may be in contact with the second reflector 90. The second electrode 110 functions as the anode of the laser diode including the active layer 40. 【0044】The first and second electrodes 100 and 110 do not overlap with the second reflector 90 and the BTJs 60 and 70 when viewed from the Z direction. Therefore, the first and second electrodes 100 and 110 do not obstruct the laser light emitted from the second reflector 90. 【0045】 The third electrode 115 is provided on the back side of the substrate 10. The third electrode 115 is electrically connected to the first reflective layer 20a via the substrate 10. The third electrode 115 is also made of a conductive metal, such as Ti, Pt, Au, a multilayer film of AuGe and Ni and Au, or a multilayer film of PdGe, Ni and Au. The third electrode 115 may be made of the same material as the first and second electrodes 100 and 110. The third electrode 115 functions as the anode of the avalanche photodiode layer 120. 【0046】 Figure 2 is a cross-sectional view showing the configuration of the avalanche photodiode layer 120, the first reflective layer 20a, and the second reflective layer 20b. 【0047】 The avalanche photodiode layer 120 is provided between the first reflective layer 20a and the second reflective layer 20b. The avalanche photodiode layer 120 is constructed by stacking a photoelectric conversion layer 121, a transition layer 122, and a multiplier layer 123. 【0048】 The photoelectric conversion layer 121 is provided between the first reflective layer 20a and the transition layer 122. It generates electric charge by photoelectric conversion of light of the first wavelength generated in the active layer 40. The photoelectric conversion layer 121 is composed of, for example, intrinsic InGaAs without introduced impurities. The photoelectric conversion layer 121 may also be composed of, for example, InGaAsP or AlGaInAs having a composition that can absorb the wavelength λ of laser light. The photoelectric conversion layer 121 may be, for example, a lattice-mismatched material. 【0049】The transition layer 122 is provided between the photoelectric conversion layer 121 and the multiplier layer 123. The transition layer 122 transfers the charge (e.g., holes) generated in the photoelectric conversion layer 121 to the multiplier layer 123. The transition layer 122 is composed of, for example, intrinsic InGaAsP without introduced impurities. The transition layer 122 may be a single layer structure. However, it is preferable to have a layered structure (e.g., a three-layer structure) in which the composition of the transition layer 122 is changed in steps to create a stepped band gap. This lowers the band barrier and makes it easier for charge to move. 【0050】 The multiplier layer 123 is provided between the transition layer 122 and the second reflective layer 20b. The multiplier layer 123 avalanche multiplies the charge generated in the photoelectric conversion layer 121 and transitioned across the transition layer 122. The avalanche multiplied current is measured externally as a photocurrent. The multiplier layer 123 is composed of a laminated film of an n-type multiplier semiconductor layer 123n and a p-type multiplier semiconductor layer 123p. The n-type multiplier semiconductor layer 123n and the p-type multiplier semiconductor layer 123p constitute a pn junction. A reference voltage (e.g., ground voltage) is applied to the first electrode 100 as a common cathode. A positive voltage is applied to the third electrode 115 as an anode. As a result, a reverse bias is applied to the pn junction of the n-type multiplier semiconductor layer 123n and the p-type multiplier semiconductor layer 123p. A depletion layer forms at the pn junction where a reverse bias is applied. When electric charge enters this depletion layer, avalanche multiplication occurs and a photocurrent flows. As a result, even when the current from the photoelectric conversion layer 121 is small, the multiplication layer 123 can increase the current to a large amount through avalanche multiplication. The n-type multiplication semiconductor layer 123n is composed of, for example, n-type InP. The p-type multiplication semiconductor layer 123p is composed of, for example, p-type AlInAs or p-type InP. The multiplication layer 123 made of InP-based material can, for example, multiply the current by about 10 times. 【0051】The photoelectric conversion layer 121, the transition layer 122, and the multiplication layer 123 are laminated in this order in the Z direction from the first reflection layer 20a to the second reflection layer 20b. As a result, the charges (holes) generated in the photoelectric conversion layer 121 can drift from the third electrode 115 (anode) side to the first electrode 100 (cathode) side and enter the multiplication layer 123. 【0052】 Further, the n-type multiplication semiconductor layer 123n and the p-type multiplication semiconductor layer 123p of the multiplication layer 123 are laminated in this order in the Z direction. As a result, the pn junction of the n-type multiplication semiconductor layer 123n and the p-type multiplication semiconductor layer 123p can be reverse-biased between the first electrode 100 (cathode) and the third electrode 115 (anode). As a result, the avalanche photodiode layer 120 can avalanche-multiply the charges photoelectrically converted in the photoelectric conversion layer 121 into a relatively large current. 【0053】 (Regarding ΔI ＰＤ / ΔI ＶＣＳＥＬ ) FIGS. 3 and 4 are graphs showing the characteristics of a VCSEL in which a photodiode is embedded. A VCSEL in which a photodiode is embedded is also called a ViP (VCSEL with integrated Photodiode). Incidentally, in order to explain ΔI ＰＤ / ΔI ＶＣＳＥＬ , here, it is assumed that a photodiode layer PD is provided between the first reflection layer 20a and the second reflection layer 20b instead of the avalanche photodiode layer 120. 【0054】 The vertical axis represents the optical output of the laser light (hereinafter also simply referred to as the light intensity) for the VCSEL, and the photocurrent for the photodiode layer PD. The horizontal axis represents the current I ＶＣＳＥＬ supplied to the VCSEL. I ｔｈ represents the threshold current of the VCSEL. The VCSEL current width ΔI ＶＣＳＥＬ represents the change amount of the current I ＶＣＳＥＬ . The photocurrent change amount ΔI ＰＤ represents the change amount of the photocurrent I ＶＣＳＥＬ generated in the photodiode layer PD with respect to a predetermined VCSEL current width ΔI ＰＤ . 【0055】 For example, Figure 3 shows the characteristics when the photodiode layer PD is relatively close to the active layer 40 (when the number of layers of the second reflective layer 20b is small). In Figure 3, a predetermined VCSEL current width ΔI ＶＣＳＥＬ In contrast, the photocurrent change ΔI ＰＤ This changes relatively significantly. This is because the photodiode layer PD is relatively close to the active layer 40, so the light intensity of VCSEL received by the photodiode layer PD becomes relatively strong. Therefore, ΔI ＰＤ / ΔI ＶＣＳＥＬ It will grow to a relatively large size. 【0056】 Figure 4 shows the characteristics when the photodiode layer PD is relatively far from the active layer 40 (when the number of second reflective layers 20b is large). In Figure 4, the predetermined VCSEL current width ΔI ＶＣＳＥＬ In contrast, the photocurrent change ΔI ＰＤ The change is relatively small. This is because the photodiode layer PD is relatively far from the active layer 40, so the light intensity of VCSEL received by the photodiode layer PD is relatively weak. Therefore, ΔI ＰＤ / ΔI ＶＣＳＥＬ It becomes relatively small. 【0057】 To accurately measure the light intensity of VCSEL, ΔI ＰＤ / ΔI ＶＣＳＥＬ A larger value is preferable. Therefore, ΔI ＰＤ / ΔI ＶＣＳＥＬ Considering the characteristics, it is preferable that the photodiode layer PD be close to the VCSEL. 【0058】 (I ｔｈ (Regarding) VCSEL threshold current I ｔｈ In Figure 3, it is relatively high, but in Figure 4, it is relatively low. Threshold current I ｔｈ When it exceeds this value, the light intensity from VCSEL is such that, regardless of the distance between the photodiode layer PD and the active layer 40, the current I ＶＣＳＥＬ It rises with a slope that is almost equal to the value of . Therefore, the threshold current I ｔｈ When it is low, VCSEL is a certain current I ＶＣＳＥＬ In this case, the light intensity increases, and conversely, the threshold current I ｔｈWhen the value is high, VCSEL is a certain current I ＶＣＳＥＬ The light intensity weakens at this point. Therefore, the threshold current I ｔｈ A lower value is preferable. That is, the threshold current I ｔｈ Considering this, it can be said that it is preferable for the photodiode layer PD to be relatively far from the active layer 40 (i.e., for there to be more layers of the second reflective layer 20b). 【0059】 (Regarding the position and thickness of the avalanche photodiode layer 120) The characteristics of a comparative example in which a photodiode layer PD is placed between the first reflective layer 20a and the second reflective layer 20b instead of the avalanche photodiode layer 120 will be described. The photodiode layer PD is assumed to be made of InGaAs. 【0060】 By changing the film thickness of the photodiode layer PD, each ΔI ＰＤ / ΔI ＶＣＳＥＬ We investigated its characteristics. 【0061】 ΔI ＰＤ / ΔI ＶＣＳＥＬ From this perspective, the thicker the photodiode layer PD, the more layers of the second reflective layer 20b can be stacked, and even if the photodiode layer PD is separated from the active layer 40, ΔI ＰＤ / ΔI ＶＣＳＥＬ It was possible to maintain ΔI above a predetermined threshold. That is, the thicker the photodiode layer PD, the more ΔI can be maintained even when the photodiode layer PD is separated from the active layer 40. ＰＤ / ΔI ＶＣＳＥＬ It was found that it was possible to raise the threshold above a certain level. 【0062】 Next, the characteristics of the light-emitting device according to this embodiment, in which the avalanche photodiode layer 120 is placed between the first reflective layer 20a and the second reflective layer 20b, will be described. 【0063】 The film thickness of the avalanche photodiode layer 120 is changed, and each ΔI ＰＤ / ΔI ＶＣＳＥＬ We investigated its characteristics. 【0064】 ΔI ＰＤ / ΔI ＶＣＳＥＬFrom this perspective, the thicker the avalanche photodiode layer 120, the more layers of the second reflective layer 20b can be stacked, and even if the avalanche photodiode layer 120 is separated from the active layer 40, ΔI ＰＤ / ΔI ＶＣＳＥＬ We were able to maintain it above a predetermined threshold. 【0065】 Furthermore, when comparing the above comparative example with this embodiment, the avalanche photodiode layer 120 has a greater ΔI than the photodiode layer PD, even if the number of stacked second reflective layers 20b is large. ＰＤ / ΔI ＶＣＳＥＬ It is possible to maintain a high ΔI. That is, even if the avalanche photodiode layer 120 is far away from the active layer 40 relative to the photodiode layer PD, ΔI ＰＤ / ΔI ＶＣＳＥＬ It was found that ΔI can be maintained at a high level. This is because the avalanche photodiode layer 120 avalanche multiplies the charge generated in the photoelectric conversion layer 121 in the multiplication layer 123. By using the avalanche photodiode layer 120, ΔI ＰＤ / ΔI ＶＣＳＥＬ While maintaining a high value, the avalanche photodiode layer 120 can be moved far away from the active layer 40. Therefore, as explained with reference to Figures 3 and 4, by using the avalanche photodiode layer 120, ΔI ＰＤ / ΔI ＶＣＳＥＬ While maintaining a high level, the threshold current I of VCSEL ｔｈ This can be made lower. As a result, this embodiment allows ΔI ＰＤ / ΔI ＶＣＳＥＬ While maintaining a high level, the supply current I of VCSEL ＶＣＳＥＬ This can reduce the noise. Thus, the avalanche photodiode layer 120 is advantageous over the photodiode layer PD. 【0066】 Furthermore, even if the film thickness of the avalanche photodiode layer 120 is relatively thin, it exhibits sufficiently high characteristics (ΔI) at positions far from the active layer 40. ＰＤ / ΔI ＶＣＳＥＬ ) can be obtained. 【0067】Next, we will explain the relationship between the threshold current Ith of the VCSEL and the number of layers of the second reflective layer 20b. 【0068】 The threshold current Ith was investigated by varying the film thickness of the avalanche photodiode layer 120. 【0069】 The threshold current Ith of the VCSEL decreases as the number of stacked second reflective layers 20b increases, that is, as the avalanche photodiode layer 120 is farther from the active layer 40. Furthermore, when the number of stacked second reflective layers 20b is fixed, that is, when the position of the avalanche photodiode layer 120 relative to the active layer 40 is fixed, the threshold current Ith of the VCSEL decreases as the thickness of the avalanche photodiode layer 120 decreases. Therefore, from the viewpoint of the threshold current Ith of the VCSEL, it is preferable for the avalanche photodiode layer 120 to be farther from the active layer 40 and to have a thin film thickness. 【0070】 As mentioned above, reducing the thickness of the photodiode layer PD is possible. ＰＤ / ΔI ＶＣＳＥＬ From that perspective, it is undesirable. 【0071】 However, since the light-emitting device according to this embodiment uses an avalanche photodiode layer 120, even if the thickness of the avalanche photodiode layer 120 is made somewhat thin, sufficiently high characteristics (ΔI) can be achieved. ＰＤ / ΔI ＶＣＳＥＬ ) can be obtained. Furthermore, even if the number of stacked second reflective layers 20b is increased and the avalanche photodiode layer 120 is moved far away from the active layer 40, the light-emitting device according to this embodiment can still obtain sufficiently high characteristics (ΔI ＰＤ / ΔI ＶＣＳＥＬ ) can be obtained. 【0072】 Therefore, the light-emitting device according to this embodiment suppresses the current consumption of the VCSEL with a low threshold current Ith, while maintaining the high characteristics (ΔI) of the avalanche photodiode layer 120. ＰＤ / ΔI ＶＣＳＥＬ ) can be obtained. 【0073】Figure 5 is a graph showing the position of the avalanche photodiode layer 120 relative to the standing wave of the laser light generated by VCSEL. The vertical axis of this graph represents the amplitude of the standing wave of the laser light. The horizontal axis represents the distance from the active layer 40. 【0074】 Figure 5 shows the cases where the avalanche photodiode layer 120 is located at the "antinode" of the standing wave of the laser light, at a position shifted by 0.1λ from the "antinode," and at a position shifted by 0.2λ from the "antinode." 【0075】 Next, the relationship between the threshold current Ith of the VCSEL and the number of layers of the second reflective layer 20b will be explained. Note that the film thickness of the avalanche photodiode layer 120 is assumed to be fixed. 【0076】 As shown in Figure 5, the threshold current Ith was investigated when the avalanche photodiode layer 120 was positioned at the "antinode" of the standing wave of the laser light, at a position shifted by 0.1λ from the "antinode" (Δ0.1λ), and at a position shifted by 0.2λ from the "antinode" (Δ0.2λ). 【0077】 The threshold current Ith is relatively high when the avalanche photodiode layer 120 is located at the "antinode" of the standing wave of the laser light. Furthermore, it was found that the threshold current Ith gradually decreases at positions Δ0.1λ and Δ0.2λ where the avalanche photodiode layer 120 is shifted towards the "node" side from the "antinode" side of the standing wave of the laser light. Therefore, from the viewpoint of the threshold current Ith of VCSEL, it is preferable for the avalanche photodiode layer 120 to be located at a position shifted towards the "node" side from the "antinode" side of the standing wave of the laser light. 【0078】 Next, ΔI ＰＤ / ΔI ＶＣＳＥＬ The relationship between this and the number of layers of the second reflective layer 20b will be explained. Note that the film thickness of the avalanche photodiode layer 120 is assumed to be fixed. 【0079】The characteristics (ΔI) of the avalanche photodiode layer 120 when its position is set to the position of the "antinode" of the standing wave of the laser light, a position shifted by 0.1λ from the "antinode" (Δ0.1λ), and a position shifted by 0.2λ from the "antinode" (Δ0.2λ). ＰＤ / ΔI ＶＣＳＥＬ I investigated ). 【0080】 ΔI ＰＤ / ΔI ＶＣＳＥＬ The position of the avalanche photodiode layer 120 is relatively high at the "antinode" position of the standing wave of the laser light. ΔI ＰＤ / ΔI ＶＣＳＥＬ It was found that the position of the avalanche photodiode layer 120 gradually decreases at positions Δ0.1λ and Δ0.2λ, which are shifted from the position of the "antinode" to the "node" side of the standing wave of the laser light. Therefore, ΔI ＰＤ / ΔI ＶＣＳＥＬ From this perspective, it is preferable that the position of the avalanche photodiode layer 120 be close to the position of the "antinode" of the standing wave of the laser light. 【0081】 In this embodiment, by using the avalanche photodiode layer 120, sufficiently high characteristics (ΔI ＰＤ / ΔI ＶＣＳＥＬ Since this is obtained, the position of the avalanche photodiode layer 120 can be shifted from the position of the "antinode" to the "node" side of the standing wave of the laser light without any problems. This makes it possible to further reduce the threshold current Ith of the VCSEL, which leads to a reduction in current consumption. 【0082】 In summary, the light-emitting device according to this embodiment achieves high performance (ΔI) even when the avalanche photodiode layer 120 is incorporated into the VCSEL, thereby reducing the thickness of the avalanche photodiode layer 120, moving the avalanche photodiode layer 120 away from the active layer 40, and shifting it from the "antinode" of the standing wave of the laser light. ＰＤ / ΔI ＶＣＳＥＬ This allows us to maintain the position of the avalanche photodiode layer 120. 【0083】Furthermore, by reducing the thickness of the avalanche photodiode layer 120, moving the avalanche photodiode layer 120 away from the active layer 40, and shifting it away from the "antinodes" of the standing waves of the laser light, the threshold current Ith of the VCSEL can be reduced, thereby reducing the current consumption. 【0084】 Furthermore, the light-emitting device according to this embodiment can be controlled by the thickness of the avalanche photodiode layer 120, or by the position of the avalanche photodiode layer 120 relative to the standing wave of the active layer 40 or the laser light, which determines ΔI ＰＤ / ΔI ＶＣＳＥＬ It can be controlled. 【0085】 Next, a method for manufacturing the light-emitting device 1 according to the first embodiment will be described. 【0086】 Figures 6 to 11 are cross-sectional views showing an example of a method for manufacturing the light-emitting device 1 according to the first embodiment. 【0087】 On the n-type InP substrate 11, which serves as the first substrate as shown in Figure 6, multiple n-type AlGaInAs films and multiple n-type InP films are alternately epitaxially grown to form the first reflective layer 20a. 【0088】 Next, the material for the avalanche photodiode layer 120 is deposited on the first reflective layer 20a. For example, the material for the photoelectric conversion layer 121 (e.g., undoped InGaAs), the material for the transition layer 122 (e.g., undoped InGaAsP), the material for the n-type multiplier semiconductor layer 123n (e.g., n-type InP), and the material for the p-type multiplier semiconductor layer 123p (e.g., p-type AlInAs or p-type InP) are epitaxially grown on the first reflective layer 20a in this order. The transition layer 122 may be a single-layer structure. However, it is preferable to have a layered structure (e.g., a three-layer structure) in which the composition of the transition layer 122 is changed in steps to create a stepped band gap. This lowers the band barrier and makes it easier for charge to move. 【0089】 Next, multiple p-type AlGaInAs films and multiple p-type InP films are alternately epitaxially grown on the avalanche photodiode layer 120 to form a second reflective layer 20b. 【0090】Next, the materials of the first semiconductor layer 30, the active layer 40, the second semiconductor layer 50, and the BTJs 60 and 70 are epitaxially grown in this order. The material of the first semiconductor layer 30 is, for example, n-type InP. The material of the active layer 40 is, for example, AlGaInAs or InGaAsP. The material of the second semiconductor layer 50 is, for example, p-type InP. The material of the third semiconductor layer 60 is, for example, p-type AlInAs having a high p-type impurity concentration. The material of the fourth semiconductor layer 70 is, for example, n-type InP having a high n-type impurity concentration. ＋ type AlInAs. The material of the fourth semiconductor layer 70 is, for example, n ＋ type InP. 【0091】 Next, the materials of the BTJs 60 and 70 are processed using lithography technology and etching technology. At this time, the material of the fourth semiconductor layer 70 is processed by wet etching using a chlorine-based mixed solution such as HCl, H ３ PO ４ , CH ３ COOH, H ２ O, etc. The material of the third semiconductor layer 60 is processed by wet etching using a chlorine-based mixed solution such as H ３ PO ４ , H ２ O ２ , H ２ O, etc. As a result, as shown in FIG. 7, the BTJs 60 and 70 are formed within the resonator formation region. 【0092】 Next, as shown in FIG. 8, the material of the fifth semiconductor layer 80 is deposited on the second semiconductor layer 50 and the BTJs 60 and 70 so as to cover the BTJs 60 and 70. The material of the fifth semiconductor layer 80 is formed, for example, by epitaxially growing n-type InP. The material of the semiconductor layer 85 is deposited on the fifth semiconductor layer 80. The material of the semiconductor layer 85 is formed, for example, by epitaxially growing n-type InGaAs. 【0093】Next, a hard mask (e.g., a silicon oxide film) is formed on the resonator pattern using lithography and etching techniques. Furthermore, the materials for the semiconductor layer 85, the fifth semiconductor layer 80, the second semiconductor layer 50, and the active layer 40 are processed using methods such as RIE (Reactive Ion Etching) with the hard mask (not shown) as a mask. This results in the structure shown in Figure 9. 【0094】 Next, a mask material (not shown) is deposited, and this mask material is patterned to the layout of the first and second electrodes 100 and 110 using lithography and etching techniques. The mask material covers the areas other than the formation areas of the first and second electrodes 100 and 110. 【0095】 Next, using a mask material as a mask, the materials for the first and second electrodes 100 and 110 are deposited on the first semiconductor layer 30 and the semiconductor layer 85. The materials for the first and second electrodes 100 and 110 are conductive metals such as AuGe, Ti, Pt, Ni, or Au. 【0096】 Next, by removing the mask material, the first electrode 100 is formed on the first semiconductor layer 30 and the second electrode 110 is formed on the semiconductor layer 85, as shown in Figure 10. 【0097】 Next, as shown in Figure 10, the material for the third electrode 115 is deposited on the back surface of the substrate 10. The material for the third electrode 115 is, for example, a conductive metal such as AuGe, Ti, Pt, Ni, or Au. 【0098】 Next, the semiconductor layer 85 material is processed using lithography and etching techniques. As a result, as shown in Figure 11, the semiconductor layer 85 is left beneath the second electrode 110, and the semiconductor layer 85 material in the formation region of the second reflector 90 is removed. 【0099】 Next, as shown in Figure 1, a second reflector 90 is formed on the fifth semiconductor layer 80. The second reflector 90 is made of, for example, SiO ２ and TiO ２ This is a laminated film. This completes the light-emitting device 1 shown in Figure 1. 【0100】(Second Embodiment) Figure 12 is a cross-sectional view showing an example of the configuration of the light-emitting device 1 according to the second embodiment. In the second embodiment, the second reflector 90 has an uneven layer having an uneven shape on its outermost surface. The uneven shape of the second reflector 90 has an uneven shape on the light-emitting surface from which the laser light from the active layer 40 is emitted. For example, when the area of ​​the BTJ 60, 70 and the second reflector 90 as viewed from the Z direction is relatively large (for example, when the diameter is 6 μm or more), the polarization characteristics of the laser light can be controlled by providing an uneven layer on the second reflector 90. This makes it possible to increase the output power of the laser light. The material of the uneven layer is, for example, TiO ２ That's fine. The pitch of the uneven surface can be, for example, about 700 nm. The ratio of the length of the concave part to the length of the convex part of the uneven surface (Duty) can be about 0.5. The height of the convex part of the uneven surface (the step difference of the uneven surface) can be about 200 nm. 【0101】 (Third Embodiment) Figure 13 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the third embodiment. In the third embodiment, the fifth semiconductor layer 80 comprises a conductive region 130 provided between the first reflector 20 and the second reflector 90, and an impurity implant region 131 provided around the conductive region 130. The conductive region 130 is composed of, for example, n-type InP. The impurity implant region 131 is formed by implanting impurities such as H, He, O, and B into the fifth semiconductor layer 80 around the conductive region 130. The impurity implant region 131 is in a non-conductive or high-resistance state due to the introduction of crystal defects by the implantation of impurities. 【0102】 According to the third embodiment, the active layer 40, the second semiconductor layer 50, and the TJs 60 and 70 are not processed by etching, but the current is constricted by the impurity implant region 131. The current between electrodes 100 and 110 flows concentrated in the conductive region 130 and is constricted. As a result, the TJs 60 and 70 can promote luminescence in the active layer 40 directly beneath them. 【0103】Although not shown in the figures, a lens mirror may be formed on the back side of the substrate 10. This allows the light-emitting device 1 to have a light-constricting function. Alternatively, the conductive region 130 may be selectively etched to create a recess in the conductive region 130, thereby creating a step between the conductive region 130 and the impurity implant region 131. This enables light-constriction in the conductive region 130. 【0104】 Other configurations of the third embodiment may be the same as those of the first or second embodiment. Therefore, the third embodiment can obtain the same effects as the first or second embodiment. 【0105】 (Fourth Embodiment) Figure 14 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the fourth embodiment. In the fourth embodiment, a transparent electrode layer 140 is provided on the fifth semiconductor layer 80 and the semiconductor layer 85. The transparent electrode layer 140 is provided between the fifth semiconductor layer 80 or the semiconductor layer 85 and the second reflector 90 or the second electrode 110. The transparent electrode layer 140 is made of a transparent conductive material such as ITIO or ITO. The transparent electrode layer 140 may also be provided in the step between the conductive region 130 and the impurity implant region 131. As a result, the transparent electrode layer 140 can narrow the light. 【0106】 The other configurations of the fourth embodiment may be the same as those of the third embodiment. Therefore, the fourth embodiment can obtain the same effects as the third embodiment. 【0107】 (Fifth Embodiment) Figure 15 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the fifth embodiment. The fifth embodiment includes TJs 60 and 70 provided between the second semiconductor layer 50 and the second reflector 90, and an air gap 63 provided around the TJs 60 and 70. The air gap 63 is formed by etching the material of the TJs 60 and 70 from the lateral direction (perpendicular to the Z direction). 【0108】According to the fifth embodiment, the current is narrowed by the air gap 63. As a result, the current between electrodes 100 and 110 flows to and is narrowed in TJs 60 and 70. This allows TJs 60 and 70 to further efficiently promote light emission in the active layer 40 directly beneath them. 【0109】 Furthermore, a difference in refractive index occurs in the lateral direction (a direction intersecting the Z-direction) on the sides of TJ60 and TJ70. Therefore, optical constriction of the laser beam becomes possible. 【0110】 Other configurations of the fifth embodiment may be the same as those of the first or second embodiment. Therefore, the fifth embodiment can obtain the same effects as the first or second embodiment. The fifth embodiment may include a transparent electrode layer 140. In this case, the fifth embodiment can also obtain the effects of the fourth embodiment. 【0111】 (Sixth Embodiment) Figure 16 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the sixth embodiment. In the sixth embodiment, the active layer 40 comprises quantum dots 41 provided on the first semiconductor layer 30 and an embedded layer 42 provided on the quantum dots 41. The quantum dots 41 are, for example, InAs epitaxially grown on the first semiconductor layer 30. The embedded layer 42 is, for example, AlGaInAs. The active layer 40 can emit light even when composed of quantum dots 41 in this way. By using quantum dots 41 in the active layer 40, the temperature characteristics of the VCSEL can be improved. 【0112】 Other configurations of the sixth embodiment may be the same as those of any of the first to fifth embodiments. Therefore, the sixth embodiment can obtain the same effects as any of the first to fifth embodiments. 【0113】(Seventh Embodiment) Figure 17 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the seventh embodiment. In the seventh embodiment, multiple stacked structures including an active layer and BTJs are stacked. For example, in the seventh embodiment, a first stacked structure ST1 including an active layer 40, a second semiconductor layer 50, BTJs 60 and 70, and a fifth semiconductor layer 80 is provided on a first semiconductor layer 30. Furthermore, a second stacked structure ST2 including an active layer 45, a second semiconductor layer 55, TJs 65 and 75, and a fifth semiconductor layer 81 is provided on the first stacked structure ST1. That is, the seventh embodiment is a multi-junction type VCSEL. The materials of the active layer 45, the second semiconductor layer 55, and TJs 65 and 75 may be the same as the materials of the active layer 40, the second semiconductor layer 50, and BTJs 60 and 70, respectively. The configuration of the fifth semiconductor layer 81 may be the same as the fifth semiconductor layer 80 in Figure 14. However, due to current narrowing, the BTJs 60 and 70, which are close to the first electrode 100 on the cathode side, are provided only below the second reflector 90. 【0114】 The substrate 10, the first and second reflectors 20 and 90, and the electrodes 100 and 110 are common to the first and second laminated structures ST1 and ST2. The first and second laminated structures ST1 and ST2 are provided between the first reflector 20 and the second reflector 90. 【0115】 Thus, this technology is also applicable to multi-junction type VCSELs. By using a multi-junction type, the laser beam can be made to high output. However, the method of current constriction is not limited to this. Therefore, the seventh embodiment can also be combined with any of the configurations of the first to sixth embodiments. As a result, the seventh embodiment can obtain the same effects as any of the first to sixth embodiments. 【0116】 (Eighth Embodiment) Figure 18 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the eighth embodiment. In the eighth embodiment, GaAs-based materials are used for the substrate 10 and the first reflective layer 20a. For example, an n-type GaAs substrate is used for the substrate 10. The first reflective layer 20a is a GaAs-based DBR in which a plurality of GaAs layers and a plurality of AlGaAs layers or AlAs layers are alternately stacked on the substrate 10. 【0117】GaAs-based materials have superior thermal conductivity compared to InP-based materials. Therefore, using GaAs-based materials for the substrate 10 and the first reflective layer 20a improves heat dissipation. 【0118】 Other configurations of the eighth embodiment may be the same as those of any of the first to seventh embodiments. This allows the eighth embodiment to achieve the same effects as any of the first to seventh embodiments. 【0119】 (Ninth Embodiment) Figure 19 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the ninth embodiment. In the ninth embodiment, a plurality of BTJs 60, 70 and a plurality of second reflectors 90 each share one substrate 10, a first reflective layer 20a, a second reflective layer 20b, an avalanche photodiode layer 120, an active layer 40, a second semiconductor layer 50, a fifth semiconductor layer 80, a first electrode 100, and a third electrode 115. The plurality of BTJs 60, 70 are provided correspondingly between each of the plurality of second reflectors 90 and one second semiconductor layer 50. The number of BTJs 60, 70 and second reflectors 90 that share the substrate 10 etc. is not particularly limited. That is, a plurality of VCSELs are provided on one substrate 10. 【0120】 The multiple BTJs 60, 70 and the multiple second reflectors 90 may have different configurations from each other. They may also have different polarization characteristics. Since the multiple second electrodes 110 are provided in accordance with the multiple BTJs 60, 70 or the multiple second reflectors 90, each VCSEL of the multiple BTJs 60, 70 or the multiple second reflectors 90 can be driven independently. Each VCSEL may have different polarization characteristics. 【0121】 Multiple BTJs 60, 70 and multiple second reflectors 90 may be arranged in an array in a planar layout in a plane perpendicular to the Z direction. Multiple BTJs 60, 70 and multiple second reflectors 90 correspond to each other and are arranged to overlap in a planar view from the Z direction. 【0122】Other configurations of the ninth embodiment may be the same as those of the first embodiment. This allows the ninth embodiment to achieve the same effects as the first embodiment. Furthermore, the ninth embodiment can be combined with any of the configurations of the second to eighth embodiments. Therefore, the ninth embodiment can achieve the same effects as any of the second to eighth embodiments. 【0123】 (Tenth Embodiment) Figure 20 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the tenth embodiment. In the tenth embodiment, the ViP portion of the light-emitting device 1 is provided on the wiring board 200. 【0124】 The light-emitting device 1 of the tenth embodiment further comprises a wiring board 200, wiring 210, 220, and bumps 230. The wiring board 200 is made of an insulating material such as AlN. The wiring 210, 220 are patterned on the surface of the wiring board 200 in a predetermined layout. The wiring 210, 220 are made of conductive materials such as copper, aluminum, tungsten, and AuSn. The bumps 230 are provided on the wiring 210 and are electrically connected to the wiring 210. The bumps 230 are made of conductive materials such as AuSn solder, Ag, and In. 【0125】 The ViP portion of the light-emitting device 1 is connected to the wiring board 200 with the surface side having the first and second electrodes 100 and 110. The first electrode 100 is connected to the bump 230. The second electrode 110 is connected to the wiring 220. The second electrode 110 covers the second reflector 90. 【0126】 Since the surface side of the ViP portion is connected to the wiring board 200, the light-emitting device 1 becomes a back-illuminated VCSEL. Therefore, a portion of the third electrode 115 is removed at the laser beam emission position. In a plan view from the Z direction, the third electrode 115 is removed in the portion that overlaps with the BTJs 60, 70 and the second reflector 90. 【0127】 Furthermore, the substrate 10 may be made of n-type InP with a low impurity concentration, or it may be a semi-insulating substrate. 【0128】Other configurations of the tenth embodiment may be the same as those of the first embodiment. This allows the tenth embodiment to achieve the same effects as the first embodiment. Furthermore, the tenth embodiment can be combined with any of the configurations of the second to ninth embodiments. Therefore, the tenth embodiment can achieve the same effects as any of the second to ninth embodiments. 【0129】 (Eleventh Embodiment) Figure 21 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the eleventh embodiment. In the eleventh embodiment, an uneven shape is provided on the surface of the second reflector 90 facing the wiring board 200. The other configurations of the eleventh embodiment may be the same as those of the tenth embodiment. As a result, the eleventh embodiment can obtain the same effects as the tenth embodiment. 【0130】 (Twelfth Embodiment) Figure 22 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the twelfth embodiment. In the twelfth embodiment, the ViP portion of the light-emitting device 1 is provided on a semiconductor substrate 300. 【0131】 The light-emitting device 1 of the twelfth embodiment further comprises a semiconductor substrate 300, wiring 310, 320, bumps 330, and a semiconductor element 340. The semiconductor substrate 300 is made of, for example, a silicon substrate. The wiring 310, 320 are patterned on the surface of the semiconductor substrate 300 in a predetermined layout. The wiring 310, 320 are made of, for example, a conductive material such as copper, aluminum, or tungsten. The bumps 330 are provided on the wiring 310 and are electrically connected to the wiring 310. The bumps 330 are made of, for example, a conductive material such as AuSn solder. The semiconductor element 340 is provided on the semiconductor substrate 300 and is electrically connected to the wiring 310, 320. The semiconductor element 340 may be made of, for example, a transistor that constitutes a CMOS (Complementary Metal Oxide Semiconductor) circuit. Alternatively, the semiconductor element 340 may be, for example, a transistor that constitutes a drive circuit that supplies power to the light-emitting device 1. Thus, the light-emitting device 1 may have a modular structure in which the ViP and peripheral circuits are integrated. 【0132】The ViP portion of the light-emitting device 1 is connected to the semiconductor substrate 300 with the surface side containing the first and second electrodes 100 and 110 facing the semiconductor substrate 300. The first electrode 100 is connected to the bump 330. The second electrode 110 is connected to the wiring 320. The second electrode 110 covers the second reflector 90. 【0133】 Since the ViP portion is connected to the semiconductor substrate 300 on its surface side, the light-emitting device 1 becomes a back-illuminated VCSEL. Therefore, a portion of the third electrode 115 is removed at the laser beam emission position. In a plan view from the Z direction, the third electrode 115 is removed in the portion that overlaps with the BTJs 60, 70 and the second reflector 90. 【0134】 Furthermore, the substrate 10 may be made of n-type InP with a low impurity concentration, or it may be a semi-insulating substrate. 【0135】 Other configurations of the 12th embodiment may be the same as those of the first embodiment. This allows the 12th embodiment to achieve the same effects as the first embodiment. Furthermore, the 12th embodiment can be combined with any configuration of the second to 9th embodiments. Therefore, the 12th embodiment can achieve the same effects as any of the second to 9th embodiments. 【0136】 (Third Embodiment) Figure 23 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the thirteenth embodiment. In the thirteenth embodiment, an uneven shape is provided on the surface of the second reflecting mirror 90 facing the semiconductor substrate 300. The other configurations of the thirteenth embodiment may be the same as those of the twelfth embodiment. As a result, the thirteenth embodiment can obtain the same effects as the twelfth embodiment. 【0137】 (Examples of application to mobile devices) The technology disclosed herein (the technology) can be applied to various products. For example, the technology disclosed herein may be implemented as a device mounted on any type of mobile device such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, and robots. 【0138】Figure 24 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technology described herein may be applied. 【0139】 The vehicle control system 12000 comprises a plurality of electronic control units connected via a communication network 12001. In the example shown in Figure 24, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an external information detection unit 12030, an internal information detection unit 12040, and an integrated control unit 12050. The functional configuration of the integrated control unit 12050 is shown in the figure, which includes a microcomputer 12051, an audio / image output unit 12052, and an in-vehicle network interface 12053. 【0140】 The drivetrain control unit 12010 controls the operation of devices related to the vehicle's drivetrain according to various programs. For example, the drivetrain control unit 12010 functions as a control device for a drivetrain generating device that generates driving force for the vehicle, such as an internal combustion engine or a drive motor; a drivetrain transmission mechanism that transmits driving force to the wheels; a steering mechanism that adjusts the steering angle of the vehicle; and a braking device that generates braking force for the vehicle. 【0141】 The body system control unit 12020 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window system, or various lamps such as headlights, reverse lights, brake lights, turn signals, or fog lights. In this case, the body system control unit 12020 may receive radio waves transmitted from a portable device that replaces a key or signals from various switches. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock system, power window system, lamps, etc. 【0142】The external information detection unit 12030 detects information from outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the external information detection unit 12030. The external information detection unit 12030 causes the imaging unit 12031 to capture images of the outside of the vehicle and receives the captured images. Based on the received images, the external information detection unit 12030 may perform object detection processing such as detecting people, cars, obstacles, signs, or characters on the road surface, or distance detection processing. 【0143】 The imaging unit 12031 is a light sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light. 【0144】 The in-vehicle information detection unit 12040 detects information inside the vehicle. The in-vehicle information detection unit 12040 is connected to, for example, a driver status detection unit 12041 that detects the driver's state. The driver status detection unit 12041 includes, for example, a camera that captures images of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's level of fatigue or concentration, or determine whether the driver is drowsy, based on the detection information input from the driver status detection unit 12041. 【0145】 The microcomputer 12051 can calculate control target values ​​for the drive force generator, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the external information detection unit 12030 or the internal information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing ADAS (Advanced Driver Assistance System) functions, including collision avoidance or impact mitigation, following driving based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning. 【0146】Furthermore, the microcomputer 12051 can perform cooperative control for purposes such as autonomous driving, where the vehicle drives autonomously without driver intervention, by controlling the drive force generating device, steering mechanism, or braking device, etc., based on information about the vehicle's surroundings acquired by the external information detection unit 12030 or the internal information detection unit 12040. 【0147】 Furthermore, the microcomputer 12051 can output control commands to the body system control unit 12020 based on external information acquired by the external information detection unit 12030. For example, the microcomputer 12051 can control the headlights according to the position of a preceding or oncoming vehicle detected by the external information detection unit 12030, and perform coordinated control aimed at reducing glare, such as switching from high beams to low beams. 【0148】 The audio-image output unit 12052 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying information to the vehicle's occupants or to those outside the vehicle. In the example shown in Figure 24, the output devices are exemplified as an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an onboard display and a head-up display. 【0149】 Figure 25 shows an example of the installation position of the imaging unit 12031. 【0150】 In Figure 25, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105. 【0151】The imaging units 12101, 12102, 12103, 12104, and 12105 are installed, for example, on the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle 12100. The imaging unit 12101 installed on the front nose and the imaging unit 12105 installed on the upper part of the windshield inside the vehicle mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 installed on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 installed on the upper part of the windshield inside the vehicle is mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes. 【0152】 Figure 25 shows an example of the imaging range of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 located on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 located on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 located on the rear bumper or back door. For example, by superimposing the image data captured by imaging units 12101 to 12104, an overhead view image of the vehicle 12100 can be obtained. 【0153】 At least one of the imaging units 12101 to 12104 may have a function for acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera consisting of multiple image sensors, or an image sensor having pixels for phase difference detection. 【0154】For example, the microcomputer 12051, based on distance information obtained from the imaging units 12101 to 12104, can determine the distance to each object within the imaging range 12111 to 12114 and the temporal change of this distance (relative speed to the vehicle 12100). In particular, it can extract the closest object on the vehicle 12100's path that is traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or more) as the preceding vehicle. Furthermore, the microcomputer 12051 can set a predetermined distance to be maintained before the preceding vehicle and perform automatic braking control (including follow-and-stop control) and automatic acceleration control (including follow-and-start control), etc. In this way, cooperative control aimed at autonomous driving, where the vehicle drives autonomously without driver intervention, can be performed. 【0155】 For example, the microcomputer 12051 can use distance information obtained from imaging units 12101 to 12104 to classify and extract three-dimensional object data related to three-dimensional objects, such as motorcycles, passenger cars, large vehicles, pedestrians, utility poles, and other three-dimensional objects, and use this data for automatic obstacle avoidance. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the degree of risk of collision with each obstacle. If the collision risk is above a set value and there is a possibility of collision, the microcomputer 12051 can provide driving assistance to avoid collisions by outputting a warning to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or evasive steering via the drive system control unit 12010. 【0156】At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer 12051 can recognize pedestrians by determining whether or not pedestrians are present in the images captured by the imaging units 12101 to 12104. Such pedestrian recognition is performed, for example, by a procedure to extract feature points from the images captured by the imaging units 12101 to 12104 as infrared cameras, and a procedure to perform pattern matching on a series of feature points that indicate the contour of an object to determine whether or not it is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the imaging units 12101 to 12104 and recognizes a pedestrian, the audio-image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio-image output unit 12052 may also control the display unit 12062 to display an icon indicating a pedestrian at a desired position. 【0157】 The above describes an example of a vehicle control system to which the technology described herein may be applied. The technology described herein may be applied to, for example, the imaging unit 12031, among the configurations described above. 【0158】 Furthermore, this technology can be configured as follows: 【0159】 (1) A light-emitting device comprising: a first reflecting portion; a second reflecting portion; a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type provided between the first reflecting portion and the second reflecting portion; an active layer provided between the first semiconductor layer and the second semiconductor layer, which generates light of a first wavelength by applying power to the first and second semiconductor layers; and an avalanche photodiode layer provided within the first reflecting portion. 【0160】 (2) The light-emitting device according to (1), wherein the first reflective portion includes a first reflective layer of a first conductivity type and a second reflective layer of a second conductivity type, and the avalanche photodiode layer is provided between the first reflective layer and the second reflective layer. 【0161】(3) The light-emitting device according to (2), wherein the avalanche photodiode layer includes a photoelectric conversion layer that converts light of the first wavelength into electricity to generate an electric charge, and a multiplier layer that multiplies the electric charge by an avalanche. 【0162】 (4) The light-emitting device according to (3), wherein the photoelectric conversion layer and the multiplication layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer. 【0163】 (5) The light-emitting device according to (3), wherein the avalanche photodiode layer further includes a transition layer provided between the photoelectric conversion layer and the multiplier layer, which transfers the charge generated in the photoelectric conversion layer to the multiplier layer. 【0164】 (6) The light-emitting device according to (5), wherein the photoelectric conversion layer, the transition layer, and the multiplier layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer. 【0165】 (7) The light-emitting apparatus according to any one of (3) to (6), wherein the multiplier layer includes a first multiplier semiconductor layer of a first conductivity type and a second multiplier semiconductor layer of a second conductivity type. 【0166】 (8) The light-emitting apparatus according to (7), wherein the first multiplier semiconductor layer and the second multiplier semiconductor layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer. 【0167】 (9) The light-emitting device according to any one of (3) to (8), wherein the multiplier layer multiplies the current from the photoelectric conversion layer by avalanche multiplication. 【0168】 (10) The light-emitting device according to any one of (2) to (9), further comprising: a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; and a third electrode electrically connected to the first reflective layer. 【0169】 (11) The light-emitting device according to (10), wherein a voltage that is a reverse bias to the avalanche photodiode layer is applied between the first electrode and the third electrode. 【0170】(12) The light-emitting device according to any one of (1) to (11), wherein the first reflecting portion is made of a semiconductor material and the second reflecting portion is made of a dielectric material. 【0171】 (13) The light-emitting device according to any one of (1) to (12), further comprising: a third semiconductor layer provided on the second semiconductor layer between the second reflecting portion and the second semiconductor layer, having a higher concentration of impurities of the second conductivity type than the second semiconductor layer; and a fourth semiconductor layer of the first conductivity type provided on the third semiconductor layer, forming a tunnel junction with the third semiconductor layer. 【0172】 (14) The light-emitting device according to any one of (1) to (13), wherein the second reflecting portion comprises an uneven layer having an uneven shape on the light-emitting surface from which light from the active layer is emitted. 【0173】 (15) The light-emitting device according to (13), further comprising a fifth semiconductor layer provided on the fourth semiconductor layer, wherein the fifth semiconductor layer includes a conductive region sandwiched between the first reflector and the second reflector and an impurity implant region provided around the conductive region. 【0174】 (16) The light-emitting device according to (15), further comprising a transparent conductive film provided on the conductive region and the impurity implant region. 【0175】 (17) The light-emitting device according to (13), wherein the third and fourth semiconductor layers are provided between the second semiconductor layer and the second reflector, and an air gap is provided around the third and fourth semiconductor layers. 【0176】 (18) The light-emitting device according to any one of (1) to (17), wherein the active layer includes quantum dots. 【0177】 (19) The light-emitting device according to (13), wherein a plurality of stacked structures composed of the first to fourth semiconductor layers and the active layer are provided between the first reflector and the second reflector. 【0178】(20) The light-emitting device according to any one of (1) to (19), wherein the first reflective portion is provided on an InP substrate, the first reflective portion is a laminated film of a plurality of AlGaInAs layers and a plurality of InP layers, and the second reflective portion is a laminated film of a plurality of silicon oxide films and a plurality of titanium oxide films. 【0179】 (21) The light-emitting device according to any one of (1) to (19), wherein the first reflector is provided on a GaAs substrate, and the first reflector is composed of a laminated film of GaAs and AlGaAs or AlAs. 【0180】 (22) The light-emitting device according to (13), wherein a plurality of second reflectors are provided with respect to one first reflector, and a plurality of third semiconductor layers and a plurality of fourth semiconductor layers are provided correspondingly between each of the plurality of second reflectors and the second semiconductor layer. 【0181】 (23) The light-emitting device according to (1), wherein light from the active layer is emitted from the first reflecting section. 【0182】 (24) The light-emitting device according to (10), further comprising a wiring board on which wiring layers electrically connected to the first and third electrodes are provided. 【0183】 (25) The light-emitting device according to (10), further comprising a semiconductor substrate on which a wiring layer electrically connected to the first and third electrodes and a semiconductor element connected to the wiring layer are provided. 【0184】 Furthermore, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure. Also, the effects described herein are merely illustrative and not limiting, and other effects may exist. 【0185】1. Light-emitting device 10. Substrate 20. First reflector 30. First semiconductor layer 40. Active layer 50. Second semiconductor layer 60. Third semiconductor layer 70. Fourth semiconductor layer 80. Fifth semiconductor layer 85. Semiconductor layer 90. Second reflector 100. First electrode 110. Second electrode 115. Third electrode 120. Avalanche photodiode layer 121. Photoelectric conversion layer 122. Transition layer 123. Multiplication layer

Claims

1. A light-emitting device comprising: a first reflecting portion; a second reflecting portion; a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type provided between the first reflecting portion and the second reflecting portion; an active layer provided between the first semiconductor layer and the second semiconductor layer, which generates light of a first wavelength by applying power to the first and second semiconductor layers; and an avalanche photodiode layer provided within the first reflecting portion.

2. The light-emitting device according to claim 1, wherein the first reflective portion includes a first reflective layer of a first conductivity type and a second reflective layer of a second conductivity type, and the avalanche photodiode layer is provided between the first reflective layer and the second reflective layer.

3. The light-emitting device according to claim 2, wherein the avalanche photodiode layer includes a photoelectric conversion layer that converts light of the first wavelength into electricity to generate an electric charge, and a multiplier layer that multiplies the electric charge by avalanche.

4. The light-emitting device according to claim 3, wherein the photoelectric conversion layer and the multiplication layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer.

5. The light-emitting device according to claim 3, wherein the avalanche photodiode layer further includes a transition layer provided between the photoelectric conversion layer and the multiplier layer, which transfers the charge generated in the photoelectric conversion layer to the multiplier layer.

6. The light-emitting device according to claim 5, wherein the photoelectric conversion layer, the transition layer, and the multiplier layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer.

7. The light-emitting device according to claim 3, wherein the multiplier layer includes a first multiplier semiconductor layer of a first conductivity type and a second multiplier semiconductor layer of a second conductivity type.

8. The light-emitting device according to claim 7, wherein the first multiplier semiconductor layer and the second multiplier semiconductor layer are stacked in this order in a first direction from the first reflective layer toward the second reflective layer.

9. The light-emitting device according to claim 3, wherein the multiplier layer multiplies the current from the photoelectric conversion layer by avalanche multiplication.

10. The light-emitting device according to claim 2, further comprising: a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; and a third electrode electrically connected to the first reflective layer.

11. The light-emitting device according to claim 10, wherein a voltage that is a reverse bias to the avalanche photodiode layer is applied between the first electrode and the third electrode.

12. The light-emitting device according to claim 1, wherein the first reflective portion is made of a semiconductor material and the second reflective portion is made of a dielectric material.

13. The light-emitting device according to claim 1, further comprising: a third semiconductor layer provided on the second semiconductor layer between the second reflective portion and the second semiconductor layer, having a higher concentration of impurities of the second conductivity type than the second semiconductor layer; and a fourth semiconductor layer of the first conductivity type provided on the third semiconductor layer, forming a tunnel junction with the third semiconductor layer.

14. The light-emitting device according to claim 1, wherein the second reflective portion comprises an uneven layer having an uneven shape on the light-emitting surface from which light from the active layer is emitted.

15. The light-emitting device according to claim 13, further comprising a fifth semiconductor layer provided on the fourth semiconductor layer, wherein the fifth semiconductor layer includes a conductive region sandwiched between the first reflector and the second reflector, and an impurity implant region provided around the conductive region.

16. The light-emitting device according to claim 15, further comprising a transparent conductive film provided on the conductive region and the impurity implant region.

17. The light-emitting device according to claim 13, wherein the third and fourth semiconductor layers are provided between the second semiconductor layer and the second reflector, and an air gap is provided around the third and fourth semiconductor layers.

18. The light-emitting device according to claim 1, wherein the active layer includes quantum dots.

19. The light-emitting device according to claim 13, wherein a plurality of stacked structures composed of the first to fourth semiconductor layers and the active layer are provided between the first reflecting portion and the second reflecting portion.

20. The light-emitting device according to claim 1, wherein the first reflective portion is provided on an InP substrate, the first reflective portion is a laminated film of a plurality of AlGaInAs layers and a plurality of InP layers, and the second reflective portion is a laminated film of a plurality of silicon oxide films and a plurality of titanium oxide films.

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