Light-emitting device

Abstract

To provide a light emitting device capable of further improving performance.SOLUTION: A light emitting device has a first reflector placed on a semiconductor substrate, a first active layer placed on the first reflector, a first tunnel junction layer placed on the first active layer, a second active layer placed on the first tunnel junction layer, and a second reflector placed on the second active layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device. [Background technology]

[0002] Patent Document 1 discloses a VCSEL (Vertical Cavity Surface Emitting Laser) including a saturable absorbing layer. The VCSEL of Patent Document 1 can generate optical pulses with short optical pulse widths and high peak values.

[0003] Patent Document 2 discloses a VCSEL having a plurality of active regions and tunnel junctions arranged between the active regions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-176886 [Patent Document 2] U.S. Patent Application Publication No. 2022 / 0190559 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for further improvements in the performance of light-emitting devices such as those described in Patent Documents 1 and 2. [Means for solving the problem]

[0006] Therefore, an object of the present disclosure is to provide a light-emitting device that can further improve performance.

[0007] According to one disclosure of the present specification, there is provided a semiconductor device including a first reflecting mirror disposed on a semiconductor substrate, a first active layer disposed on the first reflecting mirror, a first tunnel junction layer disposed on the first active layer, a second active layer disposed on the first tunnel junction layer, and a second reflecting mirror disposed on the second active layer, wherein the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, a second barrier layer disposed on the plurality of first quantum well layers, and a third barrier layer disposed between the plurality of first quantum well layers. the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, a fifth barrier layer disposed on the plurality of second quantum well layers, and a sixth barrier layer disposed between the plurality of second quantum well layers, wherein when the number of the plurality of second quantum well layers is N, the thickness of each of the plurality of second quantum well layers is w (nm), the number of active layers is M, and the number of quantum well layers required to obtain an optical intensity with a predetermined peak-to-peak ratio is Q, the thickness Ta (nm) of the second active layer satisfies the following formula (1): Ta≧{w×N×M+(QN×M)×w / 0.2} / M (1) The distance between the second active layer and the first tunnel junction layer is 40 nm or more, and any one of the plurality of first quantum well layers and the plurality of second quantum well layers is thinner than any one of the first barrier layer to the sixth barrier layer.

[0008] Furthermore, according to yet another disclosure of the present specification, there is provided a light emitting device including: a first reflecting mirror disposed on a semiconductor substrate; a first active layer disposed on the first reflecting mirror; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; and a second reflecting mirror disposed on the second active layer, wherein the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, and a fifth barrier layer disposed on the plurality of second quantum well layers, and the fourth barrier layer is thinner than the fifth barrier layer.

[0009] Furthermore, according to yet another disclosure of the present specification, there is provided a light emitting device including: a first reflecting mirror disposed on a semiconductor substrate; a first active layer disposed on the first reflecting mirror; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; and a second reflecting mirror disposed on the second active layer, wherein the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, and a second barrier layer disposed on the plurality of first quantum well layers, and the first barrier layer is thinner than the second barrier layer. [Effects of the Invention]

[0010] According to the present disclosure, a light emitting device capable of further improving performance is provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing a light emitting device according to a first embodiment. [Figure 2] 1 is an enlarged cross-sectional view showing a light emitting device according to a first embodiment. [Figure 3] 4 is a graph showing an example of a light output waveform of the light emitting device according to the first embodiment. [Figure 4] FIG. 2 is an energy band gap diagram near the active layer in the light emitting device according to the first embodiment. [Figure 5] FIG. 6 is an enlarged cross-sectional view showing a light emitting device according to a second embodiment. [Figure 6] FIG. 10 is an energy band gap diagram near the active layer in the light emitting device according to the second embodiment. [Figure 7] FIG. 10 is an enlarged cross-sectional view showing a light emitting device according to a third embodiment. [Figure 8] FIG. 10 is an energy band gap diagram near the active layer in the light emitting device according to the third embodiment. [Figure 9] FIG. 10 is an enlarged cross-sectional view showing a light emitting device according to a fourth embodiment. [Figure 10] FIG. 10 is an enlarged cross-sectional view showing a light emitting device according to a fifth embodiment. [Figure 11]FIG. 10 is an enlarged cross-sectional view showing a light emitting device according to a sixth embodiment. [Figure 12] FIG. 13 is an enlarged cross-sectional view showing a light emitting device according to a seventh embodiment. [Figure 13] FIG. 13 is a block diagram showing a schematic configuration of a distance measuring device according to an eighth embodiment. [Figure 14] FIG. 13 is a block diagram showing an example of the configuration of a moving body according to the ninth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Identical or corresponding elements throughout the drawings are designated by common reference numerals, and their description may be omitted or simplified. In the following description, a VCSEL capable of generating an optical pulse with a short optical pulse width and a high peak value may be referred to as a high peak value VCSEL.

[0013] [First embodiment] FIG. 1 is a schematic cross-sectional view showing a light-emitting device 1 according to this embodiment. The light-emitting device 1 of this embodiment is a vertical-cavity surface-emitting laser (VCSEL) having a distributed Bragg reflector (DBR). The light-emitting device 1 includes a semiconductor substrate 11, a lower DBR layer 12, a spacer portion 13, a resonator portion 20, an upper DBR layer 32, electrodes 40 and 41, and a protective film 42. The lower DBR layer 12 (first reflector) is disposed on the semiconductor substrate 11. The spacer portion 13 is disposed on the lower DBR layer 12. The resonator portion 20 is disposed on the spacer portion 13. The upper DBR layer 32 (second reflector) is disposed on the resonator portion 20. The layers (spacer portion 13 and resonator portion 20) located between the lower DBR layer 12 and the upper DBR layer 32 form a resonator spacer portion. A saturable absorbing layer 131 is disposed in the spacer portion 13.

[0014] Fig. 2 is an enlarged cross-sectional view showing the light emitting device 1 according to this embodiment. Fig. 2 is an enlarged view of a region R shown in Fig. 1. The configuration of the light emitting device 1 will be described in more detail with mutual reference to Fig. 1 and Fig. 2.

[0015] Resonator section 20 has an n-type layer 21 arranged on spacer section 13, and an active layer 22 (first active layer) arranged on n-type layer 21. Resonator section 20 also has an active layer 25 (second active layer) arranged on active layer 22 via a spacer section, and a p-type layer 26 arranged on active layer 25.

[0016] The active layer 22 includes a barrier layer 222 (first barrier layer), three quantum well layers 221 (first quantum well layers), two barrier layers 224 (third barrier layers) disposed between the quantum well layers 221, and a barrier layer 223 (second barrier layer). The three quantum well layers 221 and the two barrier layers 224 form a multiple quantum well structure.

[0017] The active layer 25 includes a barrier layer 252 (fourth barrier layer), three quantum well layers 251 (second quantum well layers), two barrier layers 254 (sixth barrier layers) and a barrier layer 253 (fifth barrier layer) disposed between the quantum well layers 251. The three quantum well layers 251 and the two barrier layers 254 form a multiple quantum well structure.

[0018] The quantum well layers 221 and 251 may be undoped InGaAs layers, and the barrier layers 222, 223, 224, 252, 253, and 254 may be undoped GaAs layers.

[0019] The spacer portion between active layer 22 and active layer 25 includes a p-type layer 27 disposed on active layer 22, an oxide constriction layer 23 (first oxide constriction layer) disposed on p-type layer 27, and a p-type layer 28 disposed on oxide constriction layer 23. The spacer portion between active layer 22 and active layer 25 also includes a tunnel junction layer 24 (first tunnel junction layer) disposed on p-type layer 28, and an n-type layer 29 disposed on tunnel junction layer 24. An oxide constriction layer 31 (second oxide constriction layer) is disposed in upper DBR layer 32.

[0020] The active layer 22, the active layer 25, the p-type layer 26, the upper DBR layer 32, and the spacer between the active layer 22 and the active layer 25 are processed into a mesa shape. An electrode 40 electrically connected to the n-type layer 21 is disposed on the n-type layer 21 exposed by this mesa processing. An electrode 41 electrically connected to the upper DBR layer 32 is disposed on the upper DBR layer 32. A protective film 42 is disposed on the top surface of the n-type layer 21 and the side and top surfaces of the mesa, excluding at least part of the surfaces of the electrodes 40 and 41.

[0021] The semiconductor substrate 11 may be made of, for example, a GaAs substrate. The lower DBR layer 12 may be made of, for example, an Al 0.1 GaAs layer and Al 0.9 The structure can be constructed by stacking 35 pairs of layers, each layer consisting of a GaAs layer. Here, λc is the center wavelength of the high reflection band of the lower DBR layer 12, which is 940 nm in this embodiment. In this embodiment, the semiconductor substrate 11 and the lower DBR layer 12 are n-type.

[0022] The spacer portion 13 has a structure not found in typical VCSELs. The saturable absorbing layer 131 may be formed of a multiple quantum well structure including three quantum well layers, each of which has an 8-nm-thick InGaAs quantum well layer sandwiched between 10-nm-thick AlGaAs barrier layers. The portions of the spacer portion 13 other than the multiple quantum well layers may be formed of doped or undoped GaAs, AlGaAs, or the like.

[0023] The resonator section 20 includes an nip junction including an n-type layer 21, an active layer 22, a p-type layer 27, an oxide constriction layer 23, and a p-type layer 28, a tunnel junction layer 24, and an nip junction including an n-type layer 29, an active layer 25, and a p-type layer 26. The tunnel junction layer 24 includes, in order from the semiconductor substrate 11 side, a highly doped p-type layer and a highly doped n-type layer. As described above, the light emitting device of this embodiment is a multi-junction VCSEL in which multiple nip junctions are connected by the tunnel junction layer 24. The tunnel junction layer 24 may be composed of three or more semiconductor regions. The oxide constriction layer 23 is Al 0.98 Ga 0.02It can be formed by oxidizing a part of the As layer.

[0024] The upper DBR layer 32 is, for example, an Al 0.1 Ga 0.9 As layer and Al 0.9 Ga 0.1 The upper DBR layer 32 is formed by stacking 20 pairs of layers, each layer consisting of an As layer. An oxidized constriction layer 31 is disposed within the upper DBR layer 32. The oxidized constriction layer 31 is, for example, an Al 30 nm thick film. 0.98 Ga 0.02 In this embodiment, the upper DBR layer 32 is a p-type layer.

[0025] The oxidized narrowing layers 23 and 31 are formed by, for example, adding Al 0.98 Ga 0.02 The light-emitting device 1 has a non-oxidized portion in the center of the mesa and an oxidized portion near the sidewall of the mesa, both of which are formed by oxidizing the As layer from the side of the mesa with water vapor. The diameter of the non-oxidized portion in plan view can be approximately 10 μm. As a result, current injected into the light-emitting device 1 flows only through the non-oxidized portion, and only the portion of the light-emitting device 1 that overlaps with the center of the mesa in plan view lases. However, the oxidized constriction layer 23 is not essential and may not be provided.

[0026] The light emitting device 1 may be configured so that the laser light generated therein is emitted from the upper DBR layer 32 side, or so that the laser light generated therein is emitted from the semiconductor substrate 11 side. When the laser light is emitted from the upper DBR layer 32 side, the reflectance of the upper DBR layer 32 is designed to be lower than that of the lower DBR layer 12.

[0027] The light-emitting device 1 of this embodiment is based on the configuration of a typical VCSEL and further includes the following three additional elements. The first of these three elements is to substantially increase the volume of the active layer. For example, a typical VCSEL is composed of three quantum wells, but the volume of the active layer in the light-emitting device 1 of this embodiment is larger than this. The second is to introduce a saturable absorbing layer 131. The third is to increase the effective cavity length of the VCSEL compared to that of a typical VCSEL. The effective cavity length is the cavity length experienced by light within the cavity. More specifically, it is the average distance traveled by light that passes through the active layer in the resonant direction, is reflected by the two reflecting mirrors that make up the cavity, and then passes through the active layer again. If this effective cavity length is comparable to that of a typical VCSEL, the peak pulse width may be too short. The effective cavity length is preferably designed to obtain the required pulse width. For example, the effective cavity length of the light-emitting device 1 of this embodiment can be set longer than that of a typical VCSEL. By adding at least one, and preferably three, of these elements, it is possible to realize a VCSEL capable of generating optical pulses with high peak values ​​and short pulse widths.

[0028] The light-emitting device 1 has two electrodes for injecting current into the active layer. Specifically, the light-emitting device 1 of this embodiment has electrodes 40 and 41, which inject current into the active layer. A modified light-emitting device configuration is also possible in which the light absorption characteristics are controlled by injecting current into the saturable absorbing layer or applying a reverse bias voltage. Such a configuration is referred to as a comparative example. The comparative light-emitting device is, for example, a VCSEL using a saturable absorbing layer, and has a pin structure in which both the active layer and the saturable absorbing layer are sandwiched between a p-type layer and an n-type layer. Furthermore, the comparative example has two electrodes for electrically controlling the p-type and n-type layers sandwiching the active layer, and two electrodes for electrically controlling the p-type and n-type layers of the saturable absorbing layer. A single electrode may serve as any two of the four electrodes. Therefore, the number of electrodes may be three, four, or more.

[0029] In contrast to the comparative example, the light-emitting device 1 of this embodiment does not perform electrical control of the saturable absorbing layer, such as current injection or reverse bias voltage application. That is, the number of electrodes of the light-emitting device 1 is smaller than the number of electrodes of the light-emitting device of the comparative example. This configuration allows for miniaturization of the light-emitting device 1. This configuration also allows for a reduction in the number or size of control circuits that control each electrode. Furthermore, since the greater the number of electrodes, the greater the distribution of electrical characteristics for each electrode, reducing the number of electrodes makes it possible to reduce the variation in electrical characteristics.

[0030] The design concept of the light-emitting device of the comparative example differs from the design concept of the light-emitting device 1 of the present embodiment. In the light-emitting device of the comparative example, a voltage is applied to the active layer in the forward direction of pI, thereby injecting carriers for light emission into the active layer. A voltage is also applied to the saturable absorbing layer in the forward or reverse direction of pI. The oscillation timing of the light-emitting device is controlled by the conditions or time change of the voltage applied to the saturable absorbing layer. In this configuration, the oscillation timing is controlled by controlling the voltage or current applied to the saturable absorbing layer to change the characteristics of the saturable absorbing layer, such as the absorption coefficient. Therefore, it is preferable that the absorption coefficient of the saturable absorbing layer in a non-laser oscillation state be designed to be sufficiently large so as not to cause oscillation. On the other hand, it is preferable that the absorption coefficient of the saturable absorbing layer in an oscillation state be designed to be sufficiently small. In the configuration of the comparative example, it is not preferable to have a gain and an absorption coefficient of the saturable absorbing layer close to the oscillation condition that transitions from a non-laser oscillation state to an oscillating state after a certain period of time has elapsed; therefore, a design with a margin is desirable. Therefore, in the configuration of the comparative example, the light emitting device is designed to achieve a large absorption coefficient for a gain that is sufficient to achieve a non-oscillation state and a small absorption coefficient that is sufficient to achieve an oscillation state, and control of the absorption coefficient is achieved by electrical control.

[0031] FIG. 2 also shows the positions of the antinodes and nodes of the standing wave of light propagating within the light-emitting device 1, indicated by dashed lines. As shown in FIG. 2, the quantum well layers 221 and 251 are designed with materials and thicknesses such that they are positioned at the antinodes of the standing wave. The tunnel junction layer 24 is designed with materials and thicknesses such that it is positioned at the node of the standing wave. The tunnel junction layer 24 is composed of highly doped p-type and n-type layers, and it is desirable to position it near the node of the standing wave to avoid light absorption. The oxide constriction layers 23 and 31 are designed with materials and thicknesses such that they are positioned at the node of the standing wave. This reduces the optical effect of the edges of the oxidized portions of the oxide constriction layers 23 and 31. If the optical effect of the edges of the oxidized portions does not affect the laser characteristics, the oxide constriction layer 23 does not necessarily have to be positioned near the node, and may be positioned away from the node.

[0032] Fig. 3 is a graph showing an example of a calculated optical output waveform of the light emitting device 1 according to the embodiment. The horizontal axis of Fig. 3 represents time in arbitrary units, and the vertical axis of Fig. 3 represents the amount of light (solid line) in arbitrary units and the carrier density (dashed line) in arbitrary units.

[0033] The light emitting device 1 according to this embodiment emits light having a profile that has a maximum peak value and converges to a stable value, which is a predetermined light intensity, after the maximum peak value. That is, in the light emitting device 1 according to this embodiment, oscillation begins approximately several tens to several hundreds of picoseconds after the start of current injection. This delay in the start of oscillation is due to the large effective volume of the active layers 22 and 25 and the fact that oscillation is inhibited by light absorption in the saturable absorbing layer 131 for a certain period of time after the start of current injection. When light is absorbed in the saturable absorbing layer 131, the absorbed light is accumulated as carriers in the saturable absorbing layer 131. As light is absorbed, the number of carriers increases, and when the carrier density in the saturable absorbing layer 131 reaches the transparent carrier density, the saturable absorbing layer 131 no longer absorbs light. As a result, the effect of inhibiting laser oscillation disappears, and the semiconductor light emitting element begins laser oscillation.

[0034] The purpose of inhibiting laser oscillation for a certain period of time by the saturable absorbing layer 131 is to accumulate carriers exceeding a threshold carrier density in the active layers 22 and 25. Here, the threshold carrier density is the carrier density that generates the gain required for laser oscillation.

[0035] FIG. 4 is an energy bandgap diagram near the active layer 25 in the light-emitting device 1 according to this embodiment. The vertical axis of FIG. 4 indicates the energy gap Eg, and the horizontal axis of FIG. 4 indicates the depth direction of the light-emitting device 1. Note that the scale of the horizontal axis in FIG. 4 has been appropriately changed for emphasis, and the width of each layer shown in FIG. 4 does not reflect the actual thickness of each semiconductor layer. Furthermore, the thickness values ​​of the semiconductor layers shown in FIG. 4 indicate a design example of the light-emitting device 1.

[0036] As shown in FIG. 4, the active layer 25 has three 8-nm-thick quantum well layers 251 arranged therein. A 6-nm-thick barrier layer 254 is arranged between each of the three quantum well layers 251. An 86-nm-thick barrier layer 252 is arranged below the three quantum well layers 251, and an 86-nm-thick barrier layer 253 is arranged above the three quantum well layers 251. The total thickness Ta of the active layer 25 is 208 nm. Although omitted in FIG. 4, the active layer 22 may also have a similar design. In this embodiment, the thickness of the barrier layer 252 and the thickness of the barrier layer 253 are the same.

[0037] 4, an n-type layer 29 is disposed between the barrier layer 252 and the tunnel junction layer 24 as a spacer layer. The thickness Ts of the n-type layer 29 is 219 nm. The n-type layer 29 may be composed of multiple layers. These multiple layers may include, for example, an oxide constriction layer, a carrier blocking layer, a strain relaxation layer, and the like.

[0038] The design of the thickness Ta of the active layer 25, the design of the thickness Ts of the n-type layer 29, and the relationship between the thicknesses of the quantum well layers and barrier layers in the multiple quantum well will be described in more detail. First, the design of the thickness Ta of the active layer 25 will be described. According to the inventors' investigations, in a light emitting device 1 with an effective cavity length of 2 μm, if a peak value ratio of 5 or more is required, the effective number of quantum well layers required is 7.5. Furthermore, the minimum carrier density required to generate stimulated amplification necessary for laser oscillation is 2×10 18 cm -3 In this case, the ratio of the density of carriers accumulated in the barrier layers to the density of carriers accumulated in the quantum well layers is approximately 0.2. In this embodiment, the number of quantum well layers per active layer is three, and since two active layers 22 and 25 are stacked, the total number of quantum well layers is six (3 × 2). The thickness of each quantum well layer is 8 nm. The thickness Ta of the active layer 25 is the sum of the total thickness of the quantum well layers and the total thickness of the barrier layers. Therefore, the minimum thickness of the active layer 25 to ensure a thickness of the active layer equivalent to 7.5 quantum well layers, including the quantum well layers and barrier layers, is {8 × 3 × 2 + (7.5 − 3 × 2) × 8 / 0.2} / 2 = 54 nm. Therefore, under the above assumptions, the thickness Ta of the active layer 25 is preferably 54 nm or greater. Here, the peak-to-peak ratio is the ratio between the peak value of the optical pulse waveform and the steady-state value after stabilization. For example, a peak value ratio of 5 means that the peak light quantity is five times the steady-state light quantity.

[0039] The above discussion will be generalized. Let N be the number of quantum well layers per active layer, w (nm) be the thickness of each quantum well layer, M be the number of active layers in the light-emitting device 1, and Q be the number of quantum well layers required to obtain a light intensity with a predetermined peak-to-peak ratio. In this case, it is desirable that the thickness Ta of the active layer 25 satisfy the following formula (1): Ta≧{w×N×M+(QN×M)×w / 0.2} / M (1)

[0040] As described above, by setting the thickness Ta of the active layer 25 so as to satisfy the formula (1), a light emitting device 1 that can obtain a sufficient peak value ratio is provided. For the same reason, it is also desirable to set the thickness Ta of the active layer 22 so as to satisfy the formula (1).

[0041] Furthermore, depending on the application of the light-emitting device 1, a larger peak-to-peak ratio may be required. For example, when a peak-to-peak ratio of 10 or more is required, 11 effective quantum well layers are required. In this case, the minimum thickness of the active layer 25 to ensure a thickness of the active layer equivalent to 11 quantum well layers, including the quantum well layers and barrier layers, is {8 × 3 × 2 + (11 − 3 × 2) × 8 / 0.2} / 2 = 124 nm when the number of active layers is two. Therefore, when a peak-to-peak ratio of 10 or more is required, the thickness Ta of the active layer 25 is desirably 124 nm or more. An example of such an application is a light-emitting device for distance measurement when the object to be measured is located far away.

[0042] Thus, the peak to peak ratio can be improved as the thickness Ta of the active layer 25 increases. However, considering the diffusion length of carriers, the thickness Ta is preferably 1 μm or less. Therefore, the thickness Ta is preferably in the range of 54 nm or more and 1 μm or less, and more preferably in the range of 124 nm or more and 1 μm or less.

[0043] Next, the relationship between the thicknesses of the quantum well layers and the barrier layers will be described in more detail. As described above, in a high-peak VCSEL such as the one described in this embodiment, carriers accumulate not only in the quantum well layers but also in the barrier layers. Therefore, a design concept is adopted in which the number of quantum well layers is limited to the minimum required for oscillation, and carriers are accumulated in the barrier layers to compensate for the lack of quantum well layers. The amount of radiative recombination is proportional to the square of the carrier density. Therefore, by accumulating carriers widely across the quantum well layers and barrier layers, as in this embodiment, energy loss due to spontaneous emission is reduced. To achieve the above design, it is desirable to ensure a certain thickness of the barrier layers in this embodiment. This configuration is more advantageous than the active layer configuration of a typical VCSEL or a configuration that increases carrier accumulation by increasing the number of quantum well layers. To achieve wide and thin carrier accumulation using the barrier layers as well, it is preferable to increase the thickness of the non-doped region. The energy difference (band gap difference) between the emission level of the quantum well layer and the band gap of the barrier layer is preferably in the range of 105 meV to 230 meV, as described below, when it is important to avoid the influence of light absorption by the band edge. If a 4% reduction in light extraction efficiency due to band-edge light absorption is acceptable, the band gap difference is preferably in the range of 60 meV to 230 meV. Here, 60 meV to 230 meV means 60 meV or more and 230 meV or less. In contrast, the design guidelines for the active layer of a conventional VCSEL, not the high-peak VCSEL described above, are presented below to explain the differences between the conventional VCSEL and a high-peak VCSEL. In a conventional VCSEL, the band gap difference between the quantum well layer and the barrier layer is large enough to prevent carrier accumulation in the barrier layer. This is done to avoid carrier accumulation in the barrier layer, increase response speed, and lower the oscillation threshold. Furthermore, the thickness of the non-doped portion, including the barrier layer, is made as thin as possible. This is done to increase response speed and reduce electrical resistance. Furthermore, the non-doped portion is kept to a minimum, and the cavity length is adjusted to a predetermined thickness, such as 1 λc, by using a doped layer other than the non-doped portion of the cavity to match the standing wave intensity distribution. Therefore, the diffusion of dopants from the tunnel junction layer does not pose a problem because it is contained within the doped portion.

[0044] Furthermore, even if dopants are mixed into the barrier layers for some reason, degradation of the characteristics of ordinary semiconductor lasers (including VCSELs) is unlikely to occur. Conversely, there are cases where dopants are intentionally doped into parts of the barrier layers to improve the characteristics of semiconductor lasers. For example, a configuration can be made in which the modulation speed of a semiconductor laser is improved by doping part of the barrier layer between quantum wells with a p-type dopant.

[0045] In a typical VCSEL configuration, it is preferable that the thickness of the non-doped section, which is composed of the quantum well layer and barrier layer of the cavity section, be as thin as possible. Furthermore, since the positions of each layer, such as the active layer and tunnel junction layer, and the positions of the refractive index interfaces between layers are aligned with the intensity distribution of the standing wave, the doped layers are thickened, and dopant diffusion from the tunnel junction layer is not a problem. Furthermore, even if dopants are mixed into the barrier layers, the characteristics of the semiconductor laser may be improved.

[0046] On the other hand, high-peak VCSELs require thick barrier layers, which are closer to the tunnel junction layer than regular VCSELs. The inventors discovered that if dopants are introduced into the barrier layer of a high-peak VCSEL, the barrier layer's ability to store carriers is reduced, resulting in a problem of reduced high-peak pulse energy. This will be discussed in more detail later.

[0047] Consider the case where a peak-to-peak ratio of 5 or greater is required for a high-peak VCSEL, i.e., where the quantum well layer thickness is 8 nm, there are three quantum well layers per active layer, and the thickness Ta of the active layer 25 is 54 nm. In this case, the total thickness of the quantum well layers is 8 × 3 = 24 nm, and the total thickness of the barrier layers is 54 − 24 = 30 nm. Therefore, the ratio of the total thickness of the barrier layers to the total thickness of the quantum well layers is approximately 1.25. This is an example where the barrier layer thickness is at the lower limit, so it is desirable for the ratio of the total thickness of the barrier layers to the total thickness of the quantum well layers to be 1.25 or greater.

[0048] Next, consider the case where a peak-to-peak ratio of 10 or more is required, i.e., the quantum well layer thickness is 8 nm, the number of quantum well layers per active layer is 3, and the thickness Ta of the active layer 25 is 124 nm. In this case, the total thickness of the quantum well layers is 8 × 3 = 24 nm, and the total thickness of the barrier layers is 124 − 24 = 100 nm. Therefore, the ratio of the total thickness of the barrier layers to the total thickness of the quantum well layers is 4.17. Because this is an example where the barrier layer thickness is at the lower limit, it is more desirable for the ratio of the total thickness of the barrier layers to the total thickness of the quantum well layers to be 4.17 or greater.

[0049] Furthermore, since the multiple quantum well layers are designed to be located near the antinodes of the standing wave, the barrier layers between the multiple quantum well layers are often designed to be relatively thin. Therefore, in order to ensure the total thickness of the barrier layers as described above, the barrier layers above and below the multiple quantum well layers are often designed to be relatively thick. Therefore, it is desirable that at least one of the multiple barrier layers in the active layer is designed to be relatively thick, and that the barrier layers between the quantum well layers are designed to be relatively thin. That is, in the example of FIG. 2, it is desirable that at least one of the multiple quantum well layers 221 and 251 is thinner than at least one of the barrier layers 222, 223, 224, 252, 253, and 254. This allows for a design in which the quantum well layers are located near the antinodes of the standing wave.

[0050] Next, the design of the thickness Ts of the n-type layer 29 will be described. As described above, in the light emitting device 1 of this embodiment, the barrier layer needs to be thick to some extent in order to ensure the peak value ratio. Meanwhile, in this embodiment, the tunnel junction layer 24 is disposed in the light emitting device 1.

[0051] However, if an attempt is made to simply replace the active layer with a thick barrier layer, which is necessary for a high peak power VCSEL, at the position where the active layer is located in the design concept of a normal VCSEL, the distance between the tunnel junction layer and the barrier layer will be closer than in the case of a normal VCSEL. Therefore, the inventors have found that in the configuration of this embodiment, the manufacturing process of tunnel junction layer 24 can affect the characteristics of light emitting device 1 due to the following factors.

[0052] The tunnel junction layer 24 is formed by a 10 19 cm -3 The VCSEL may include highly doped p-type and n-type layers with a doping ratio of 1000 to 1000. Unlike conventional VCSELs, which do not accumulate carriers in the barrier layer, high-peak VCSELs also accumulate carriers in the barrier layer. Therefore, when dopants from the tunnel junction layer 24 are introduced into the barrier layer, the carrier concentration in the barrier layer increases due to the presence of carriers generated by the doping in addition to carriers injected by current injection. This increases the probability of radiative recombination of electrons and holes, and the rate at which accumulated carriers disappear through radiative recombination. Furthermore, dopants can generate nonradiative recombination centers, which increase the nonradiative recombination of electrons and holes through these centers and cause carrier disappearance through nonradiative recombination. As a result, the carrier accumulation function is reduced, which can lead to a decrease in luminous efficiency. The decrease in luminous efficiency due to the introduction of dopants into the barrier layer does not occur in conventional VCSELs, which do not accumulate carriers in the barrier layer, but occurs in high-peak VCSELs.

[0053] The dopant of the tunnel junction layer 24 may be mixed into the barrier layer due to the influence of gas remaining in the film formation apparatus during epitaxial growth of the barrier layer and the influence of dopant diffusion from the tunnel junction layer 24 due to heat during the manufacturing process. Note that the gas remaining in the film formation apparatus during epitaxial growth of the barrier layer affects the barrier layer farther from the substrate than the tunnel junction layer 24 (i.e., the barrier layer formed after the tunnel junction layer 24).

[0054] The influence of dopant contamination due to the above factors depends on the distance between the active layer 25 and the tunnel junction layer 24, i.e., the thickness Ts of the n-type layer 29. According to the inventors' study of the range of dopant contamination from the tunnel junction layer, the thickness Ts is preferably 40 nm or more, which reduces the influence of dopant contamination. Furthermore, the thickness Ts is more preferably 70 nm or more, which further reduces the influence of dopant contamination.

[0055] Next, we will explain the preferred range of the band gap difference between the barrier layer and the quantum well layer. In this disclosure, carriers are accumulated not only in the quantum well layer but also in the barrier layer, thereby increasing the amount of accumulated carriers. The band gap difference between the barrier layer and the quantum well layer required to accumulate carriers in the barrier is 230 meV or less. Assume that the difference between the band gap of the ground state of the quantum well and the band gap of the barrier layer is small, and the light-emitting device is used within the normal temperature range in which semiconductor lasers are used, rather than near absolute zero. In this case, some of the carriers present in the quantum well layer may exist at the same energy position as the conduction band and valence band of the barrier layer in the energy direction distribution. The preferred range for such a distribution is 230 meV or less. Therefore, from the perspective of having carriers present in the barrier layer, a band gap of 230 meV or less is effective.

[0056] On the other hand, from the perspective of avoiding light absorption by the semiconductor constituting the barrier layer, it is preferable that the band gap difference be equal to or greater than a specific value. In this embodiment, the material of the barrier layer is GaAs, and the light extraction efficiency is calculated using the wavelength dependence of the absorption coefficient of GaAs as follows. When the band gap difference between the barrier layer and the quantum well layer is 105 meV, the light extraction efficiency decreases by 2% compared to when there is no band gap absorption. Similarly, when the band gap differences between the barrier layer and the quantum well layer are 60 meV, 48 meV, and 44 meV, the light extraction efficiency decreases by 3%, 4%, and 5%, respectively, compared to when there is no band gap absorption. Focusing on these differences, the difference between a 2% decrease and a 3% decrease is relatively large at 45 meV. However, the difference between a 3% decrease and a 4% decrease is 12 meV, and the difference between a 4% decrease and a 5% decrease is 4 meV, so it rapidly decreases.

[0057] In compound semiconductors with ternary or higher elements, the target controllability of element composition during crystal growth is about 1%, and this level of controllability is easily achievable. A 1% change in composition results in a bandgap change of 12 meV for AlGaAs-based materials and 14 meV for InGaAs-based materials. Therefore, a 1% change in composition results in a similar energy difference when the light extraction efficiency changes from 3% to 4%. Therefore, considering a 1% change in composition during crystal growth, it is preferable that the bandgap difference be 60 meV or more, which corresponds to a design value where the light extraction efficiency decreases by 3%.

[0058] From the above, a suitable range of the band gap difference is considered from the viewpoints of both allowing carriers to exist in the barrier layer and avoiding light absorption in the barrier layer. To keep the decrease in light extraction efficiency to 2% or less while prioritizing avoiding the influence of light absorption by the band edge, the band gap difference is preferably in the range of 105 meV to 230 meV. Furthermore, if a decrease in light extraction efficiency of about 4% due to light absorption by the band edge is acceptable, taking into account controllability during crystal growth, the band gap difference is preferably in the range of 60 meV to 230 meV.

[0059] Even if a compound semiconductor material different from the above is used, the wavelength dependency of the absorption coefficient for wavelengths equal to or less than the band gap does not change significantly as long as the material is a direct transition semiconductor material, and therefore the above-mentioned numerical values ​​can be applied.

[0060] An example of a method for manufacturing the light emitting device 1 will now be described. First, the semiconductor layers constituting the lower DBR layer 12, the spacer portion 13, the resonator portion 20, and the upper DBR layer 32 are grown on the semiconductor substrate 11 by metal organic chemical vapor deposition or molecular beam epitaxy.

[0061] Next, photolithography and etching techniques are used to pattern the active layer 22, the active layer 25, the p-type layer 26, the upper DBR layer 32, and the spacer portion between the active layer 22 and the active layer 25. This forms a columnar mesa with a diameter of, for example, about 30 μm.

[0062] Next, thermal oxidation is performed in a water vapor atmosphere at about 450° C. to remove Al in the upper DBR layer 32 and between the active layer 22 and the active layer 25. 0.98 Ga 0.02 The As oxidized constriction layers 31 and 23 are oxidized from the sidewalls of the mesa. At this time, by controlling the oxidation time, the Al 0.98 Ga 0.02 In the As layer, a non-oxidized portion is formed in the center of the mesa, and an oxidized portion is formed near the sidewall of the mesa. 0.98 Ga 0.02 The diameter of the non-oxidized portion of the As layer is controlled to be about 10 μm.

[0063] Next, using photolithography and vacuum deposition, an electrode 41 that will serve as a p-side electrode is formed on the upper surface of the mesa, and then an electrode 40 that will serve as an n-side electrode is formed on the upper surface of the n-type layer 21 that is exposed by etching. The electrode 41 has a circular ring pattern, and the central opening serves as a circular window for light extraction.

[0064] Next, photolithography and plasma CVD are used to form a protective film 42 so as to cover the top and side surfaces of the mesa on which the electrodes 40 and 41 are provided, and the top surface of the n-type layer 21. Note that the above process procedure may be such that the entire mesa is covered with the protective film before the electrodes are formed, and then the protective film is partially removed from the top surface of the mesa, and the electrode is formed in that portion.

[0065] Next, in order to obtain good electrical properties, heat treatment is carried out in a nitrogen atmosphere to alloy the interface between the electrode material and the semiconductor material, thereby completing the light emitting device 1 of this embodiment.

[0066] As described above, this embodiment provides a light-emitting device 1 with improved performance, even in a configuration in which a tunnel junction layer 24 is disposed between multiple active layers 22 and 25. In the first embodiment, a saturable absorbing layer is used to suppress laser oscillation for a certain period of time, and carriers are accumulated inside the semiconductor laser, after which a short pulse is generated and the accumulated carriers are released. This embodiment, in a configuration in which laser oscillation is suppressed for a certain period of time and carriers are accumulated inside the semiconductor laser, includes a carrier accumulation layer and a quantum well layer suitable for carrier accumulation. Therefore, the same effect can be achieved in semiconductor lasers that have a configuration in which laser oscillation other than the saturable absorbing layer is suppressed for a certain period of time. In the above description, the mesa is formed up to the n-type layer 21, but this is not limited thereto. For example, it may be formed down to the oxide constriction layer. It is preferable that the mesa be formed above the saturable absorbing layer 131. This is because forming a mesa in the saturable absorbing layer 131 increases non-radiative recombination in the saturable absorbing layer 131.

[0067] [Second embodiment] In this embodiment, a modification of the first embodiment will be described in which the thicknesses of the barrier layers 252 and 253 are changed. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0068] 5 is an enlarged cross-sectional view showing the light emitting device 1 according to this embodiment. This embodiment differs from the first embodiment in that the barrier layer 252 is thinner than the barrier layer 253 in the active layer 25. In accordance with this change, the thicknesses of the n-type layer 29 and the p-type layer 26 are changed so that the position of the quantum well layer 251 is shifted lower than the position of the quantum well layer 251 in the first embodiment.

[0069] FIG. 6 is an energy bandgap diagram near the active layer 25 in the light-emitting device 1 according to this embodiment. Three 8-nm-thick quantum well layers 251 are arranged in the active layer 25. A 6-nm-thick barrier layer 254 is arranged between each of the three quantum well layers 251. A 68-nm-thick barrier layer 252 is arranged below the three quantum well layers 251. A 104-nm-thick barrier layer 253 is arranged above the three quantum well layers 251. Therefore, the total thickness Ta of the active layer 25 is 208 nm, which is the same as the total thickness of the active layer 25 of the first embodiment. Although omitted in FIG. 4, the active layer 22 may have a similar design to that of the first embodiment.

[0070] In this embodiment, the barrier layer 252 is thinner than the barrier layer 253. As such, the thicknesses of the upper and lower barrier layers of the multiple quantum well do not need to be the same. Compared to the first embodiment, the distance from the upper DBR layer 32 to the active layer 25 is longer in this embodiment. Therefore, for example, in a configuration in which part of the upper DBR layer 32 is etched and an electrode is disposed on the resonator portion 20, if diffusion of the electrode material adversely affects the active layer, the effect of further reducing the effects of diffusion can be achieved by positioning the active layer away from the electrode.

[0071] Therefore, also in this embodiment, a light emitting device 1 is provided that can improve performance.

[0072] [Third embodiment] In this embodiment, a modified example in which the thickness of the active layer is changed from that of the second embodiment will be described. In this embodiment, the description of elements common to the first and second embodiments may be omitted or simplified.

[0073] 7 is an enlarged cross-sectional view showing the light emitting device 1 according to this embodiment. The difference between this embodiment and the second embodiment is that the overall thickness of the active layers 22 and 25 is reduced. Accordingly, the thickness of the p-type layer 26 is reduced so as to shorten the length of the resonator portion 20 by half the wavelength.

[0074] FIG. 8 is an energy bandgap diagram near the active layer 25 in the light-emitting device 1 according to this embodiment. Three 8-nm-thick quantum well layers 251 are arranged in the active layer 25. A 6-nm-thick barrier layer 254 is arranged between each of the three quantum well layers 251. A 68-nm-thick barrier layer 252 is arranged below the three quantum well layers 251. An 86-nm-thick barrier layer 252 is arranged above the three quantum well layers 251. Therefore, the total thickness Ta of the active layer 25 is 190 nm, which is thinner than the total thickness of the active layer 25 of the second embodiment. Although omitted in FIG. 8, the total thickness Ta of the active layer 22 is also 190 nm.

[0075] In this embodiment, the thickness of the active layers 22 and 25 is thinner than that in the second embodiment, but the thickness of Ta is 124 nm or more, and a high peak value ratio of 10 or more can be obtained. In this way, the thickness of the active layers 22 and 25 can be changed as appropriate.

[0076] Therefore, in this embodiment, as in the first and second embodiments, a light emitting device 1 that can improve performance is provided.

[0077] In this embodiment, the distance between the active layer 25 and the oxide constriction layer 31 is shorter than in the second embodiment, which can reduce the lateral spread of carriers and improve the light emission efficiency.

[0078] Furthermore, in this embodiment, the active layers 22, 25, and the p-type layer 26 are thinned, thereby reducing the length of the resonator portion 20 per junction by half a wavelength compared to the first embodiment. This allows for shallower etching depth for mesa formation, simplifying the manufacturing process and improving yield. By shortening the resonator length, the mesa etching depth can be reduced as described above. Furthermore, shortening the resonator length offers benefits such as reduced costs due to reduced material usage, reduced risk of longitudinal mode hopping due to increased longitudinal mode spacing, and improved light extraction efficiency due to reduced light absorption by the semiconductor. These benefits become more pronounced as the number of junctions increases. By shortening the resonator length, the present embodiment also achieves the above-mentioned effects.

[0079] If the effective cavity length is short due to a short cavity length and the necessary high peak pulse width cannot be obtained, the effective cavity length may be adjusted, for example, by providing a spacer layer or the like on the substrate side of the oxide constriction layer closer to the substrate. Even in this case, the oxide constriction layer 23 is located on the upper side (opposite the substrate) compared to the first embodiment, which has the advantage that the etching depth can be made shallower.

[0080] Next, the preferred range of the band gap difference between the barrier layer and the quantum well layer will be described. The band gap difference between the barrier layer and the quantum well layer required to store carriers in the barrier is 230 meV or less, the same as in the first embodiment. The reason why the maximum value of the preferred range of the band gap difference is the same as in the first embodiment is that the principle for storing carriers in the barrier layer is as described above, and this value does not depend on the film thickness of the barrier layer, etc.

[0081] The following calculation results were obtained for the effect of light absorption by the semiconductor constituting the barrier layer on the light extraction efficiency, calculated in the same manner as in the first embodiment. When the band gap difference between the barrier layer and the quantum well layer is 95 meV, the light extraction efficiency decreases by 2% compared to when there is no band gap absorption. Similarly, when the band gap differences between the barrier layer and the quantum well layer are 55 meV, 46 meV, and 42 meV, the light extraction efficiency decreases by 3%, 4%, and 5%, respectively, compared to when there is no band gap absorption. Focusing on these differences, the difference between a 2% decrease and a 3% decrease is relatively large, at 40 meV. However, the difference between a 3% decrease and a 4% decrease is 9 meV, and the difference between a 4% decrease and a 5% decrease is 4 meV, which rapidly decreases.

[0082] In compound semiconductors with ternary or higher elements, the target controllability of element composition during crystal growth is about 1%, and this level of controllability is easily achievable. A 1% change in composition results in a bandgap change of 12 meV for AlGaAs-based materials and 14 meV for InGaAs-based materials. Therefore, a 1% change in composition results in a similar energy difference when the light extraction efficiency changes from 3% to 4%. Therefore, considering a 1% change in composition during crystal growth, it is preferable that the bandgap difference be 55 meV or more, which corresponds to the design value of a 3% decrease in light extraction efficiency.

[0083] From the above, a suitable range of the band gap difference is considered from the viewpoints of both allowing carriers to exist in the barrier layer and avoiding light absorption in the barrier layer. To keep the decrease in light extraction efficiency to 2% or less while prioritizing avoiding the influence of light absorption by the band edge, the band gap difference is preferably in the range of 95 meV to 230 meV. Furthermore, if a decrease in light extraction efficiency of about 4% due to light absorption by the band edge is acceptable, taking into account controllability during crystal growth, the band gap difference is preferably in the range of 55 meV to 230 meV.

[0084] The preferred range of the band gap difference between the barrier layer and the quantum well layer, which is common to both the first and third embodiments, is as follows: To minimize the decrease in light extraction efficiency to 2% or less while emphasizing the avoidance of the influence of light absorption by the band edge, the band gap difference is preferably in the range of 105 meV to 230 meV (105 meV or more and 230 meV or less). Furthermore, if a decrease in light extraction efficiency of about 4% due to light absorption by the band edge is acceptable, the band gap difference is preferably in the range of 60 meV to 230 meV (60 meV or more and 230 meV or less), taking into account controllability during crystal growth.

[0085] [Fourth embodiment] In this embodiment, a modification of the first embodiment will be described in which the thicknesses of the barrier layers 222 and 223 are changed. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0086] 9 is an enlarged cross-sectional view showing a light emitting device 1 according to this embodiment. This embodiment differs from the first embodiment in that the barrier layer 222 is thinner than the barrier layer 223 in the active layer 22. In addition, the thicknesses of the n-type layer 21 and the p-type layer 27 are changed in accordance with this change. However, the total thickness Ta of the active layer 22 is the same as the total thickness of the active layer 22 in the first embodiment. In addition, the active layer 25 may have the same design as in the first embodiment.

[0087] In this embodiment, the barrier layer 222 is thinner than the barrier layer 223. In this way, the thicknesses of the barrier layers above and below the multiple quantum well do not need to be the same, and the same effects as in the first embodiment can be obtained.

[0088] Therefore, in this embodiment, as in the first embodiment, a light emitting device 1 that can improve performance is provided.

[0089] In this embodiment, the distance between the active layer 25 and the oxidized constriction layer 31 and the distance between the active layer 22 and the oxidized constriction layer 23 can be set to closer values ​​than in the first embodiment. Therefore, the degree of carrier diffusion between the multiple active layers 22 and 25 can be made uniform, and the performance of the light emitting device 1 can be improved.

[0090] [Fifth embodiment] In this embodiment, a modification of the first embodiment will be described in which the thicknesses of the barrier layers 222 and 223 are changed as in the second embodiment, and further the thicknesses of the barrier layers 252 and 253 are changed as in the fourth embodiment. That is, this embodiment combines the features of the second embodiment and the features of the fourth embodiment. In this embodiment, the description of elements common to the first, second, or fourth embodiment may be omitted or simplified.

[0091] 10 is an enlarged cross-sectional view showing a light emitting device 1 according to this embodiment. This embodiment differs from the first embodiment in that, in active layer 25, barrier layer 252 is thinner than barrier layer 253, and further, in active layer 22, barrier layer 222 is thinner than barrier layer 223. In addition, in accordance with these changes, the thicknesses of n-type layer 29, p-type layer 26, n-type layer 21, and p-type layer 27 are also changed. However, the total thickness Ta of active layers 22 and 25 is the same as the total thickness of active layers 22 and 25 in the first embodiment.

[0092] In this embodiment, barrier layer 252 is thinner than barrier layer 253, and barrier layer 222 is thinner than barrier layer 223. In this way, the thicknesses of the barrier layers above and below the multiple quantum well do not need to be the same. Furthermore, if differences in the shape of the active layer at each junction cause gain or other characteristic differences between the active layers, the shapes of the active layers at each junction may be made the same. This has the effect of reducing the characteristic differences compared to when the shapes of the active layers are different for each junction.

[0093] Therefore, also in this embodiment, a light emitting device 1 is provided that can improve performance.

[0094] [Sixth embodiment] In this embodiment, a modification in which the conductivity type of each semiconductor region is changed from that of the second embodiment will be described. In this embodiment, the description of elements common to the first and second embodiments may be omitted or simplified.

[0095] FIG. 11 is an enlarged cross-sectional view showing a light-emitting device 1 according to this embodiment. In this embodiment, the conductivity types of the semiconductor regions other than the non-doped portions are reversed compared to the second embodiment. That is, the n-type layer 21, the p-type layer 27, the p-type layer 28, the n-type layer 29, and the p-type layer 26 of the second embodiment are replaced with the p-type layer 21a, the n-type layer 27a, the n-type layer 28a, the p-type layer 29a, and the n-type layer 26a, respectively. Furthermore, the n-type lower DBR layer 12 and the p-type upper DBR layer 32 of the second embodiment are replaced with the p-type lower DBR layer 12a and the n-type upper DBR layer 32a, respectively. Furthermore, in this embodiment, the tunnel junction layer 24a (first tunnel junction layer) includes, in order from the semiconductor substrate 11 side, a highly doped n-type layer (first n-type layer) and a highly doped p-type layer (first p-type layer). In this embodiment, the conductivity type of the semiconductor substrate 11 is p-type.

[0096] In this embodiment, as in the first embodiment, a light emitting device 1 that can improve performance is provided.

[0097] In this embodiment, the p-type layer 29a is disposed on the side of the barrier layer 252, which is thinner than the barrier layer 253. Generally, the mobility of holes is smaller than the mobility of electrons, so that the injection of carriers into the quantum well is more efficient when the p-type layer 29a is disposed on the side of the thin barrier layer 252. Therefore, in this embodiment, the injection of carriers can be made more efficient than in the second embodiment.

[0098] [Seventh embodiment] In this embodiment, a modification in which a tunnel junction layer is further added to the sixth embodiment will be described. In this embodiment, the description of elements common to the first, second, or sixth embodiment may be omitted or simplified.

[0099] FIG. 12 is an enlarged cross-sectional view showing the light emitting device 1 according to this embodiment. In the light emitting device 1 of this embodiment, an n-type layer 51 is disposed on the spacer portion 13, a tunnel junction layer 52 (second tunnel junction layer) is disposed on the n-type layer 51, and a p-type layer 21a is disposed on the tunnel junction layer 52. The tunnel junction layer 52 includes, in order from the semiconductor substrate 11 side, a highly doped n-type layer (second n-type layer) and a highly doped p-type layer (second p-type layer). The configuration above the p-type layer 21a is the same as that of the sixth embodiment. In this embodiment, the semiconductor substrate 11 and the lower DBR layer 12 have n-type conductivity. The tunnel junction layer 52 serves to invert the conductivity types of the layers above and below the tunnel junction layer 52. The tunnel junction layer 52 is disposed between the lower DBR layer 12 and the active layer 22, allowing the use of an n-type semiconductor substrate 11. In this embodiment, the portion of the spacer portion 13 other than the multiple quantum wells may be made of an undoped GaAs layer or the like.

[0100] In this embodiment, too, a light emitting device 1 capable of improving performance is provided, similar to the first embodiment. Also in this embodiment, the efficiency of carrier injection can be improved, similar to the sixth embodiment.

[0101] Furthermore, in this embodiment, an n-type semiconductor substrate 11, which is generally of higher quality than a p-type semiconductor substrate, can be used, and therefore the performance of the light emitting device 1 can be improved compared to the sixth embodiment.

[0102] Although the tunnel junction layer 52 may be disposed below the spacer portion 13 (on the substrate side), it is preferable that it be disposed above the spacer portion 13 (on the opposite side to the substrate) as shown in Fig. 12. This is because an n-type semiconductor absorbs less light and can improve quality.

[0103] [Eighth embodiment] A distance measuring device according to the eighth embodiment will be described with reference to Fig. 13. Fig. 13 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment.

[0104] The distance measuring device 700 according to this embodiment is a distance measuring device (LiDAR device) in which a surface-emitting laser array in which the light emitting devices 1 according to any one of the first to seventh embodiments are arranged in an array is used as a light source unit. The distance measuring device 700 can be configured with a control unit 710, a surface-emitting laser array driver 712, a surface-emitting laser array 714, an emission-side optical system 718, a reception-side optical system 720, an image sensor 722, and a distance data processing unit 724.

[0105] The surface-emitting laser array 714 is a packaged semiconductor device in which the light-emitting devices 1 according to any one of the first to seventh embodiments are arranged in an array. The surface-emitting laser array driver 712 is a driver that receives a drive signal from the control unit 710, generates a drive current for oscillating the surface-emitting laser array 714, and outputs the drive current to the surface-emitting laser array 714. Note that the surface-emitting laser array 714 and the surface-emitting laser array driver 712 do not necessarily need to be separate components, and the surface-emitting laser array 714 may have the function of the surface-emitting laser array driver 712.

[0106] The light-emitting side optical system 718 is an optical system that emits laser light generated by the surface-emitting laser array 714 toward the range to be measured. The light-receiving side optical system 720 is an optical system that guides laser light reflected by the measurement object 1000 to an image sensor 722. Note that although the light-emitting side optical system 718 and the light-receiving side optical system 720 are represented by a single convex lens-shaped member in Fig. 13, they are not composed of only a single convex lens-shaped member, but are composed of a lens group combining multiple lenses.

[0107] The image sensor 722 is a photoelectric conversion device in which a plurality of pixels, each including a photoelectric conversion unit, are arranged in a two-dimensional array, and is a light-receiving device that outputs an electrical signal in response to incident light. The image sensor 722 may be an imaging device such as a CMOS image sensor or a SPAD image sensor. The distance data processing unit 724 functions as a distance information acquisition unit that generates and outputs information regarding the distance to the measurement target object 1000 present in the distance measurement range based on the signal from the image sensor 722. Note that the distance data processing unit 724 only needs to be electrically connected to the image sensor 722, and may be disposed in the same package as the image sensor 722 or in a package separate from the image sensor 722.

[0108] The control unit 710 is configured by an information processing device including a microcomputer and logic circuits, and functions as a central processing device that controls the operation of each unit and performs various calculation processes in the distance measuring device 700.

[0109] Next, the operation of the distance measuring device according to this embodiment will be described with reference to Fig. 13. First, the control unit 710 outputs a drive signal to the surface-emitting laser array driver 712. The surface-emitting laser array driver 712 receives the drive signal from the control unit 710 and injects a current of a predetermined value into the surface-emitting laser array 714. This causes the surface-emitting laser array 714 to oscillate, and laser light is output from the surface-emitting laser array 714.

[0110] The laser light generated by the surface-emitting laser array 714 is emitted toward the distance measurement range by the light-emitting side optical system 718. Of the laser light irradiated onto the measurement object 1000 in the distance measurement range, the laser light reflected by the measurement object 1000 and incident on the light-receiving side optical system 720 is guided to the image sensor 722 by the light-receiving side optical system 720.

[0111] Each pixel of the image sensor 722 generates an electric signal pulse in accordance with the timing of incidence of the laser light. The electric signal pulse generated by the image sensor 722 is input to the distance data processing unit 724.

[0112] The distance data processing unit 724 generates information about the distance to the measurement object 1000 along the light propagation direction based on the reception timing of the electrical signal pulse output from the image sensor 722. For example, the information about the distance to the measurement object 1000 is generated based on the time difference between the timing at which light is emitted from the surface-emitting laser array 714 and the timing at which the image sensor 722 receives the light. By calculating the distance information based on the electrical signal pulse output from each pixel of the image sensor 722, three-dimensional information about the measurement object 1000 can be acquired.

[0113] The ranging device 700 of this embodiment can be applied to, for example, a control device in the automotive field that controls a vehicle to avoid collision with another vehicle, or a control device that controls automatic driving by following another vehicle. The ranging device 700 of this embodiment can also be applied to other moving objects (moving devices) such as ships, aircraft, and industrial robots, as well as moving object detection systems. The ranging device 700 of this embodiment can be widely applied to devices that use information about objects recognized three-dimensionally, including distance information. These moving objects can be configured to include the ranging device of this embodiment and control means that controls the moving object based on information about the distance acquired by the ranging device.

[0114] Furthermore, the three-dimensional information including depth that can be acquired by the distance measuring device 700 of this embodiment can also be used in an image capturing device, an image processing device, a display device, etc. For example, by using the three-dimensional information acquired by the distance measuring device 700 of this embodiment, it is possible to display a virtual object on an image of the real world without creating a sense of incongruity. Furthermore, by storing the three-dimensional information together with the image information, it is also possible to correct the blurring of the captured image after shooting.

[0115] [Ninth embodiment] A moving body according to the ninth embodiment will be described with reference to Figures 14(a) and 14(b), which are block diagrams showing examples of the configuration of a moving body according to this embodiment.

[0116] 14(a) shows an example of the configuration of a device mounted on a vehicle as an in-vehicle camera. The device 80 has a distance measurement unit 803 that measures the distance to an object to be measured, and a collision determination unit 804 that determines whether or not there is a possibility of a collision based on the distance measured by the distance measurement unit 803. The distance measurement unit 803 may be configured, for example, by the distance measuring device 700 described in the eighth embodiment. Here, the distance measurement unit 803 is an example of a distance information acquisition means that acquires distance information to the object to be measured. In other words, the distance information is information related to the distance to the object to be measured, etc.

[0117] The device 80 is connected to a vehicle information acquisition device 810 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The device 800 is also connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 804. The device 80 is also connected to an alarm device 830 that issues an alarm to the driver based on the determination result of the collision determination unit 804. For example, if the collision determination unit 804 determines that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel. These devices of the device 80 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0118] In this embodiment, the device 80 measures the distance around the vehicle, for example, the front or rear. Fig. 14(b) shows the device when measuring the distance in front of the vehicle (distance measurement range 850). A vehicle information acquisition device 810, which serves as a distance measurement control means, sends an instruction to the device 80 or the distance measurement unit 803 to perform a distance measurement operation. This configuration can further improve the accuracy of distance measurement.

[0119] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from a lane, etc. Furthermore, the present invention is not limited to vehicles such as automobiles, but can be applied to moving objects (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to a wide range of devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, without being limited to moving objects.

[0120] [Modified embodiment] The present disclosure is not limited to the above-described embodiments and various modifications are possible. For example, an example in which part of the configuration of one embodiment is added to another embodiment, or an example in which part of the configuration of one embodiment is replaced with part of the configuration of another embodiment, is also an embodiment of the present disclosure.

[0121] In the first to seventh embodiments described above, a two-junction configuration including two active layers is illustrated, but the number of junctions is not limited to this. For example, a configuration similar to the above-described embodiments can be applied even when the number of junctions is three or more. For example, in a three-junction configuration, a structure in which two groups including layers from the tunnel junction layer 24 to the n-type layer 21 are stacked can be applied.

[0122] Furthermore, in the above-described first to seventh embodiments, GaAs, AlGaAs, and InGaAs are exemplified as semiconductor materials on which crystal growth is possible when a GaAs substrate is used as the semiconductor substrate 11, but the semiconductor substrate 11 is not limited to a GaAs substrate. For example, an InP substrate can also be used as the semiconductor substrate 11. Examples of semiconductor materials on which crystal growth is possible when an InP substrate is used as the semiconductor substrate 11 include InP, InGaAs, InGaP, and InGaAsP.

[0123] Furthermore, the DBR layer in the light-emitting devices according to the first to seventh embodiments does not necessarily have to be made of a semiconductor material, and may be made of a material other than a semiconductor material. In this case, too, by configuring the light-emitting device to have the same functions as the first to seventh embodiments, the same effects as those of this embodiment can be achieved.

[0124] Furthermore, the oxide constriction layer 23 is not necessarily required in the light-emitting devices according to the first to seventh embodiments, and the oxide constriction layer 23 may not be provided. In such a case, for example, in FIG. 2, a configuration in which the layers below the active layer 22 are shifted upward by a distance of ½ λc in the plane of the drawing can be applied. This shortens the cavity length by ½ λc, thereby reducing the amount of material used during manufacturing and lowering costs. Furthermore, the longitudinal mode spacing is widened, thereby reducing the risk of longitudinal mode hopping. Light absorption by the semiconductor is reduced, improving light extraction efficiency. These advantages become more pronounced as the number of junctions increases. If a short cavity length results in a short effective cavity length, making it impossible to obtain a required high peak pulse width, the effective cavity length may be adjusted, for example, by providing a spacer layer closer to the substrate.

[0125] Furthermore, the electrode 40 in the light-emitting device according to the first embodiment does not necessarily have to be formed on the upper surface of the n-type layer 21, and may be formed, for example, on the lower surface of the semiconductor substrate 11. In this case as well, the same effects as those of the first embodiment can be achieved as long as the saturable absorbing layer has a pin configuration in which it is sandwiched between a p-type layer and an n-type layer and is not electrically controlled from the outside.

[0126] The disclosure of this specification includes the complement of the concepts described in this specification. In other words, if this specification states, for example, that "A is B" (A=B), then this specification is deemed to disclose or suggest that "A is not B" even if the statement that "A is not B" (A≠B) is omitted. This is because when "A is B," it is assumed that the case where "A is not B" is taken into consideration.

[0127] The disclosure of this specification includes the following configurations. (Configuration 1) a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, a second barrier layer disposed on the plurality of first quantum well layers, and a third barrier layer disposed between the plurality of first quantum well layers; the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, a fifth barrier layer disposed on the plurality of second quantum well layers, and a sixth barrier layer disposed between the plurality of second quantum well layers; When the number of the plurality of second quantum well layers is N, the thickness of each of the plurality of second quantum well layers is w (nm), the number of active layers is M, and the number of quantum well layers required to obtain a light intensity with a predetermined peak value ratio is Q, the thickness Ta (nm) of the second active layer satisfies the following formula (1): Ta≧{w×N×M+(QN×M)×w / 0.2} / M (1) a distance between the second active layer and the first tunnel junction layer is 40 nm or more; Any one of the plurality of first quantum well layers and the plurality of second quantum well layers is thinner than any one of the first barrier layer to the sixth barrier layer. A light-emitting device characterized by: (Configuration 2) The thickness Ta of the second active layer is 54 nm or more. 2. The light-emitting device according to claim 1. (Configuration 3) The thickness Ta of the second active layer is 124 nm or more. 3. The light-emitting device according to configuration 1 or 2. (Configuration 4) The distance between the second active layer and the first tunnel junction layer is 70 nm or more. 4. The light emitting device according to any one of configurations 1 to 3. (Configuration 5) a ratio of the total thickness of the first barrier layer to the sixth barrier layer to the total thickness of the plurality of first quantum well layers and the plurality of second quantum well layers is 1.25 or more; 5. The light emitting device according to any one of configurations 1 to 4. (Configuration 6) a ratio of the total thickness of the first barrier layer to the sixth barrier layer to the total thickness of the plurality of first quantum well layers and the plurality of second quantum well layers is 4.17 or more; 6. The light emitting device according to any one of configurations 1 to 5. (Configuration 7) The fourth barrier layer is thinner than the fifth barrier layer. 7. The light emitting device according to any one of configurations 1 to 6. (Configuration 8) The first barrier layer is thinner than the second barrier layer. 7. The light emitting device according to any one of configurations 1 to 6. (Configuration 9) the first barrier layer is thinner than the second barrier layer; The fourth barrier layer is thinner than the fifth barrier layer. 7. The light emitting device according to any one of configurations 1 to 6. (Configuration 10) a first oxide constriction layer disposed between the first active layer and the second active layer; a second oxide constriction layer disposed on the second active layer; Further having 10. The light emitting device according to any one of configurations 1 to 9. (Configuration 11) a second oxide constriction layer disposed on the second active layer; 10. The light emitting device according to any one of configurations 1 to 9. (Configuration 12) a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, and a fifth barrier layer disposed on the plurality of second quantum well layers; The fourth barrier layer is thinner than the fifth barrier layer. A light-emitting device characterized by: (Configuration 13) the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, and a second barrier layer disposed on the plurality of first quantum well layers; The first barrier layer is thinner than the second barrier layer. 13. The light-emitting device according to claim 12. (Configuration 14) the semiconductor substrate is p-type; The first tunnel junction layer includes a first n-type layer and a first p-type layer disposed on the first n-type layer. 14. The light-emitting device according to claim 12 or 13. (Configuration 15) a second tunnel junction layer disposed between the semiconductor substrate and the first active layer; the semiconductor substrate is n-type; the first tunnel junction layer includes a first n-type layer and a first p-type layer disposed on the first n-type layer; The second tunnel junction layer includes a second n-type layer and a second p-type layer disposed on the second n-type layer. 14. The light-emitting device according to claim 12 or 13. (Configuration 16) a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, and a second barrier layer disposed on the plurality of first quantum well layers; The first barrier layer is thinner than the second barrier layer. A light-emitting device characterized by: (Configuration 17) The optical fiber further includes a saturable absorbing layer between the first reflector and the second reflector. 17. The light emitting device according to any one of configurations 1 to 16. (Configuration 18) The saturable absorbing layer is disposed between the first reflector and the first active layer. 18. The light-emitting device according to claim 17. (Configuration 19) The light emitting device is configured to emit light having a profile that has a maximum peak value and converges to a stable value that is a predetermined light intensity after the maximum peak value. 19. The light emitting device according to any one of configurations 1 to 18. (Configuration 20) a band gap difference between any one of the plurality of first quantum well layers and the plurality of second quantum well layers and any one of the first barrier layer to the sixth barrier layer is 60 meV or more and 230 meV or less; 20. The light emitting device according to any one of configurations 1 to 19. (Configuration 21) a band gap difference between any one of the plurality of first quantum well layers and the plurality of second quantum well layers and any one of the first barrier layer to the sixth barrier layer is 105 meV or more and 230 meV or less; 21. The light emitting device according to any one of configurations 1 to 20. (Configuration 22) The light-emitting device according to any one of configurations 1 to 21, a light receiving device that receives light emitted from the light emitting device and reflected by the object to be measured; a distance information acquisition unit that acquires information about the distance to the object to be measured based on the time difference between the timing at which light is emitted from the light emitting device and the timing at which light is received by the light receiving device; A distance measuring device comprising: (Configuration 23) A mobile object, a distance measuring device according to aspect 22; a control means for controlling the moving object based on information about the distance acquired by the distance measuring device; A moving object characterized by having:

[0128] The present disclosure can also be realized by a process in which a program that realizes one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device read and execute the program. The present disclosure can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0129] It should be noted that the above-described embodiments are merely examples of specific embodiments for carrying out the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be carried out in various forms without departing from its technical idea or main features. [Explanation of symbols]

[0130] 1. Light-emitting device 11 Semiconductor substrate 12, 12a Lower DBR layer 22, 25 active layer 24, 52 Tunnel junction layer 32, 32a Upper DBR layer 221, 251 quantum well layer 222, 223, 224, 252, 253, 254 Barrier layer

Claims

1. a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, a second barrier layer disposed on the plurality of first quantum well layers, and a third barrier layer disposed between the plurality of first quantum well layers; the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, a fifth barrier layer disposed on the plurality of second quantum well layers, and a sixth barrier layer disposed between the plurality of second quantum well layers; When the number of the plurality of second quantum well layers is N, the thickness of each of the plurality of second quantum well layers is w (nm), the number of active layers is M, and the number of quantum well layers required to obtain a light intensity with a predetermined peak value ratio is Q, the thickness Ta (nm) of the second active layer satisfies the following formula (1): Ta≧{w×N×M+(Q-N×M)×w / 0.2} / M (1) a distance between the second active layer and the first tunnel junction layer is 40 nm or more; Any one of the plurality of first quantum well layers and the plurality of second quantum well layers is thinner than any one of the first barrier layer to the sixth barrier layer. A light-emitting device characterized by:

2. The thickness Ta of the second active layer is 54 nm or more.

2. The light emitting device according to claim 1.

3. The thickness Ta of the second active layer is 124 nm or more.

2. The light emitting device according to claim 1.

4. The distance between the second active layer and the first tunnel junction layer is 70 nm or more.

2. The light emitting device according to claim 1.

5. a ratio of the total thickness of the first barrier layer to the sixth barrier layer to the total thickness of the first quantum well layers and the second quantum well layers is 1.25 or more; 2. The light emitting device according to claim 1.

6. a ratio of the total thickness of the first barrier layer to the sixth barrier layer to the total thickness of the first quantum well layers and the second quantum well layers is 4.17 or more; 2. The light emitting device according to claim 1.

7. The fourth barrier layer is thinner than the fifth barrier layer.

2. The light emitting device according to claim 1.

8. The first barrier layer is thinner than the second barrier layer.

2. The light emitting device according to claim 1.

9. the first barrier layer is thinner than the second barrier layer; The fourth barrier layer is thinner than the fifth barrier layer.

2. The light emitting device according to claim 1.

10. a first oxide constriction layer disposed between the first active layer and the second active layer; a second oxide constriction layer disposed on the second active layer; Further having 2. The light emitting device according to claim 1.

11. a second oxide constriction layer disposed on the second active layer; 2. The light emitting device according to claim 1.

12. a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the second active layer includes a fourth barrier layer, a plurality of second quantum well layers disposed on the fourth barrier layer, and a fifth barrier layer disposed on the plurality of second quantum well layers; The fourth barrier layer is thinner than the fifth barrier layer. A light-emitting device characterized by:

13. the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, and a second barrier layer disposed on the plurality of first quantum well layers; The first barrier layer is thinner than the second barrier layer.

13. The light emitting device according to claim 12.

14. the semiconductor substrate is p-type; The first tunnel junction layer includes a first n-type layer and a first p-type layer disposed on the first n-type layer.

13. The light emitting device according to claim 12.

15. a second tunnel junction layer disposed between the semiconductor substrate and the first active layer; the semiconductor substrate is n-type; the first tunnel junction layer includes a first n-type layer and a first p-type layer disposed on the first n-type layer; The second tunnel junction layer includes a second n-type layer and a second p-type layer disposed on the second n-type layer.

13. The light emitting device according to claim 12.

16. a first reflector disposed on a semiconductor substrate; a first active layer disposed on the first reflector; a first tunnel junction layer disposed on the first active layer; a second active layer disposed on the first tunnel junction layer; a second reflector disposed on the second active layer; and and the first active layer includes a first barrier layer, a plurality of first quantum well layers disposed on the first barrier layer, and a second barrier layer disposed on the plurality of first quantum well layers; The first barrier layer is thinner than the second barrier layer. A light-emitting device characterized by:

17. The optical fiber further includes a saturable absorbing layer between the first reflector and the second reflector.

2. The light emitting device according to claim 1.

18. The saturable absorbing layer is disposed between the first reflector and the first active layer.

18. The light emitting device according to claim 17.

19. The light emitting device is configured to emit light having a profile that has a maximum peak value and converges to a stable value that is a predetermined light intensity after the maximum peak value.

2. The light emitting device according to claim 1.

20. a band gap difference between any one of the plurality of first quantum well layers and the plurality of second quantum well layers and any one of the first barrier layer to the sixth barrier layer is 60 meV or more and 230 meV or less; 2. The light emitting device according to claim 1.

21. a band gap difference between any one of the plurality of first quantum well layers and the plurality of second quantum well layers and any one of the first barrier layer to the sixth barrier layer is 105 meV or more and 230 meV or less; 2. The light emitting device according to claim 1.

22. A light emitting device according to any one of claims 1 to 21; a light receiving device that receives light emitted from the light emitting device and reflected by the object to be measured; a distance information acquisition unit that acquires information about the distance to the measurement object based on the time difference between the timing at which light is emitted from the light emitting device and the timing at which light is received by the light receiving device; A distance measuring device comprising:

23. A mobile object, a distance measuring device according to claim 22; a control means for controlling the moving object based on information about the distance acquired by the distance measuring device; A moving object characterized by having:

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