Light emitting device and light measuring device

Abstract

To provide a light-emitting device capable of preventing erroneous lighting of a signal line caused by propagation of leakage current from a light-emitting element part to the signal line.SOLUTION: A light-emitting chip 10 comprises: a semiconductor substrate; a light-emitting element part formed on the semiconductor substrate, and consisting of a plurality of light-emitting elements that emit light; a signal line formed on the semiconductor substrate, and transmitting a signal to the light-emitting elements; and an insulating layer formed between the signal line and the semiconductor substrate in a region where the signal line can emit light.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a light emitting device and a light measurement device. [Background technology]

[0002] Patent Document 1 discloses a light-emitting component including a substrate on which a second semiconductor laminate is grown via a tunnel junction layer or a III-V compound layer having metallic conductivity on a first semiconductor laminate, a plurality of light-emitting elements formed by the first semiconductor laminate, and a drive unit formed by the second semiconductor laminate including a thyristor, which drives the plurality of light-emitting elements to a state where they can be switched on in sequence.

[0003] Patent document 2 discloses a light emitting device that includes a light emitting section in which a plurality of light emitting element groups, each having a plurality of light emitting elements, are arranged, and the light emitting section is configured such that, for each of the plurality of light emitting element groups, the plurality of light emitting elements included in each light emitting element group are sequentially set to an emitting or non-emitting state in parallel along the arrangement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-006502 [Patent Document 2] Japanese Patent Application Publication No. 2020-120018 Summary of the Invention [Problem to be solved by the invention]

[0005] In a monolithic light-emitting substrate in which a light-emitting element and a signal line for transmitting a signal to the light-emitting element are configured on the same substrate, if leakage current from the light-emitting element section is transmitted to the signal line, the signal line will erroneously light up.

[0006] An object of the present invention is to provide a light emitting device and a light measuring device that prevent erroneous lighting of a signal line due to leakage current from a light emitting element portion being transmitted to the signal line. [Means for solving the problem]

[0007] A light emitting device according to a first aspect of the present invention comprises a semiconductor substrate, a light emitting element portion formed in a partial region of the semiconductor substrate and consisting of a plurality of light emitting elements that emit light, a signal line formed on the semiconductor substrate and that transmits a signal to the light emitting element, and an insulating layer formed between the signal line and the semiconductor substrate in an area where the signal line can emit light.

[0008] A light-emitting device according to a second aspect of the present invention is a light-emitting device according to the first aspect, further comprising a resistor formed in the light-emitting area of ​​the signal line to limit the current to the light-emitting element, and the insulating layer is formed in the area of ​​the resistor.

[0009] A light emitting device according to a third aspect of the present invention is the light emitting device according to the second aspect, wherein the insulating layer is further formed in a predetermined region around the region of the resistor.

[0010] A light emitting device according to a fourth aspect of the present invention is the light emitting device according to the first aspect, further comprising a terminal formed on the semiconductor substrate to which a signal to be transmitted to the light emitting element is input.

[0011] A light emitting device according to a fifth aspect of the present invention is the light emitting device according to the fourth aspect, wherein a signal for causing the light emitting element to emit light is transmitted from the terminal to the signal line.

[0012] A light emitting device according to a sixth aspect of the present invention is the light emitting device according to the first aspect, wherein the light emitting element section is made up of a plurality of areas, and the light emitting elements are connected to the signal line for each of the plurality of areas.

[0013] A light emitting device according to a seventh aspect of the present invention is the light emitting device according to the sixth aspect, wherein the signal lines are wired between the areas.

[0014] An optical measurement device according to an eighth aspect of the present invention comprises a light emitting device according to any one of the first to seventh aspects, a light receiving unit that receives light emitted from the light emitting device and reflected by an object, and a measurement unit that measures the distance to the object based on the travel distance of the light emitted from the light emitting device and received by the light receiving unit. [Effects of the Invention]

[0015] According to the first aspect of the present invention, even if leakage current occurs from the light emitting element component, it is possible to prevent erroneous lighting of the signal line due to the leakage current from the light emitting element component being transmitted to the signal line.

[0016] According to the second aspect of the present invention, the insulating layer prevents leakage current from being transmitted to the resistor, thereby preventing erroneous lighting of the resistor due to leakage current from the light emitting element portion being transmitted to the resistor.

[0017] According to the third aspect of the present invention, erroneous lighting of the resistor due to leakage current from the light emitting element portion being transmitted to the resistor can be more reliably prevented than when only the resistor region is protected by an insulating layer.

[0018] According to the fourth aspect of the present invention, a signal can be transmitted from the terminal to the light-emitting element portion.

[0019] According to the fifth aspect of the present invention, a signal for causing a light emitting element to emit light can be transmitted.

[0020] According to the sixth aspect of the present invention, it is possible to make the light emitting elements emit light in area units.

[0021] According to the seventh aspect of the present invention, the wiring area can be reduced.

[0022] According to the optical measurement device of the eighth aspect of the present invention, even if leakage current occurs from the light-emitting element section, the distance to an object can be measured using a light-emitting device that prevents leakage current from the light-emitting element section from flowing toward the substrate through the signal line. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is an explanatory diagram showing a plan view of a light-emitting chip according to an embodiment of the disclosed technology; [Figure 2] FIG. 2 is an enlarged cross-sectional view of a light-emitting element. [Figure 3] FIG. 2 is an enlarged view of a resistor. [Figure 4] FIG. 4 is a cross-sectional view showing a cross-sectional structure taken along the line XX′ of FIG. [Figure 5] 9 is a diagram showing an overview of a smartphone 900 in which a light-emitting chip according to an embodiment is used. FIG. [Figure 6] FIG. 1 is a diagram illustrating an example of a functional configuration of a smartphone. [Figure 7] FIG. 10 is a diagram showing a modified example of the light emitting device. [Figure 8] FIG. 10 is a diagram showing a modified example of the light emitting device. DETAILED DESCRIPTION OF THE INVENTION

[0024] An example of an embodiment of the present disclosure will be described below with reference to the drawings. The same reference numerals are used throughout the drawings to designate identical or equivalent components and parts. The dimensional proportions of the drawings are exaggerated for illustrative purposes and may differ from the actual proportions.

[0025] In the following, an example in which a VCSEL (Vertical Cavity Surface Emitting Laser) is applied as a light-emitting element according to an embodiment of the present invention will be described, but the present invention is not limited to this, and an LED (Light Emitting Diode) or the like may also be applied.

[0026] Fig. 1 is an explanatory diagram showing a plan view of a light-emitting chip according to an embodiment of the present invention. The light-emitting chip 10 shown in Fig. 1 includes an anode electrode 11, a gate electrode 12, and a light-emitting element section 30. The light-emitting element section 30 has a plurality of light-emitting elements 40.

[0027] The anode electrode 11 is an anode-side electrode formed on a part of the wiring extending from the anode electrode formed on the light-emitting element section 30. The anode electrode 11 applies a predetermined voltage VLD to the light-emitting element section 30. In the present embodiment, an example in which the anode electrodes 11 are provided on both ends of the light-emitting chip 10 will be described, but the present invention is not limited to this, and an appropriate number of anode electrodes 11 may be provided taking into consideration the mounting of the light-emitting chip 10, etc.

[0028] The gate electrode 12 is an example of a terminal to which a signal to be transmitted to the light-emitting element of the present invention is input, and is an electrode that supplies a signal to the light-emitting element section 30 via a signal line 41 to cause the light-emitting element section 30 to emit light. In this embodiment, as described below, the light-emitting element section 30 consists of 12 areas 35 as shown in FIG. 1. Therefore, the light-emitting chip 10 shown in FIG. 1 has 12 gate electrodes 12 to allow the light-emitting elements 40 in each area to emit light independently. The light-emitting element 40 emits light by a current supplied to the anode electrode 11, so the anode electrode 11 is supplied with the power necessary for light emission. In contrast, the gate electrode 12 only needs to be supplied with a signal to cause light emission, so the voltage supplied to the gate electrode 12 is lower than the voltage supplied to the anode electrode 11. Specifically, the voltage supplied to the gate electrode 12 may be approximately 5 V to 10 V. The arrangement pattern of the gate electrodes 12 is not limited to the example shown in FIG. 1. The number of areas 35 is also not limited to 12.

[0029] The light-emitting element section 30 includes a plurality of light-emitting elements 40. In this embodiment, the light-emitting element section 30 corresponds to a region surrounding all of the light-emitting elements 40 formed on the light-emitting chip 10. In this embodiment, when the vertical direction of FIG. 1 is considered as a row, the light-emitting elements 40 in each row are arranged at a predetermined interval. On the other hand, when viewed horizontally in FIG. 1, the light-emitting elements 40 are arranged at a predetermined interval every other row. Adjacent rows are vertically offset by half the size of the light-emitting elements 40, and the light-emitting elements 40 are arranged in a so-called staggered pattern. However, the arrangement of the light-emitting elements 40 is not limited to a staggered pattern. For example, the light-emitting elements 40 in each row may be arranged at a predetermined interval, with the positions of the light-emitting elements 40 not vertically offset between adjacent rows, in a so-called array pattern. The number of light-emitting elements 40 may be an appropriate number taking into account the output power required of the light-emitting chip 10, etc. In this embodiment, the light-emitting element section 30 is composed of 12 areas 35 as shown in FIG. 1.

[0030] 1, the signal line 41 may be wired between the areas 35 in the light-emitting element section 30. In other words, in a plan view of the light-emitting element section 30, the portion of the signal line 41 extending from the gate electrode 12 does not overlap with the area 35 except for the portion connected to the light-emitting element 40 in the area 35, and is wired within the space separating the areas 35. The width of the signal line 41 in the short direction may be formed narrower than the width of each area 35 of the light-emitting element section 30 in a plan view. The light-emitting chip 10 according to this embodiment has a so-called monolithic structure in which the light-emitting element 40 and the signal line 41 are formed on the same substrate.

[0031] FIG. 2 is a cross-sectional view showing the cross-sectional structure of the light-emitting element 40. As shown in FIG.

[0032] Light-emitting element 40 comprises an n-type substrate 70 using GaAs, a lower DBR (Distributed Bragg Reflector) layer 71 formed on n-type substrate 70, a resonator 72 formed on lower DBR layer 71, an upper DBR layer 73 formed on resonator 72, a tunnel coupling layer 75 formed on upper DBR layer 73, a cathode layer 76 formed on tunnel coupling layer 75, a p-gate layer 77 formed on cathode layer 76, an n-gate layer 78 formed on p-gate layer 77, and an anode layer 79 formed on n-gate layer 78. A cathode electrode 90 (rear electrode) is formed on the rear surface of n-type substrate 70. Furthermore, a gate electrode 12 is formed on anode layer 79.

[0033] The lower DBR layer 71 is a multilayer reflector having a predetermined thickness, for example, 0.25λ / n, where λ is the oscillation wavelength of the light emitting element 40 and n is the refractive index of the medium (semiconductor layer), and is formed by alternately stacking two semiconductor layers with different refractive indices. In this embodiment, the lower DBR layer 71 is n-type.

[0034] The upper DBR layer 73 is a multilayer reflector having a predetermined thickness, for example, 0.25λ / n, and configured by alternately stacking two semiconductor layers with different refractive indices. In this embodiment, the upper DBR layer 73 is n-type.

[0035] The resonator 72 resonates and amplifies the light emitted from the light emitting element 40. The light resonated and amplified by the resonator 72 is emitted from the opening 83 of the light emitting element 40.

[0036] The cathode layer 76 functions as a cathode, the p-gate layer 77 and the n-gate layer 78 function as gates, and the anode layer 79 functions as an anode.

[0037] In the region of the light emitting element 40, the p-gate layer 77, the n-gate layer 78, and the anode layer 79 are removed by etching to form an opening 93. Adjacent to the opening 83, an anode electrode 92 is formed on the anode layer 79.

[0038] In the region of the light-emitting element 40, an oxidized region 74 is formed in the upper DBR layer 73. The oxidized region 74 is an example of an insulating layer, particularly an example of an oxide film, of the present invention, and has a function of blocking current. That is, by forming the oxidized region 74 in the region of the light-emitting element 40, it is possible to restrict the current flowing from the anode electrode 82 to the cathode electrode 90. By restricting the current flowing from the anode electrode 82 to the cathode electrode 90, the light-emitting chip 10 consumes less power than if the oxidized region 74 were not formed.

[0039] In this embodiment, at least the region where the oxidized region 74 is to be formed is exposed by etching, and a portion of the upper DBR layer 73 is oxidized to form the oxidized region 74 .

[0040] A resistor 50 is formed in the middle of the signal line 41 that transmits a signal from the gate electrode 12 to the light emitting element section 30, limiting the current that flows from the gate electrode 12 to the light emitting element section 30. The resistor 50 may be formed anywhere between the gate electrode 12 and the light emitting element section 30. FIG. 3 is an enlarged view of the resistor 50. FIG. 4 is a cross-sectional view showing the cross-sectional structure taken along line X-X' in FIG. 3.

[0041] Light-emitting chip 10 includes an n-type substrate 70 made of GaAs, a lower DBR (Distributed Bragg Reflector) layer 71 formed on n-type substrate 70, a resonator 72 formed on lower DBR layer 71, an upper DBR layer 73 formed on resonator 72, a tunnel coupling layer 75 formed on upper DBR layer 73, a cathode layer 76 formed on tunnel coupling layer 75, a p-gate layer 77 formed on cathode layer 76, an n-gate layer 78 formed on p-gate layer 77, and an anode layer 79 formed on n-gate layer 78. In addition, a cathode electrode 90 (rear electrode) is formed on the rear surface of n-type substrate 70.

[0042] An electrode 82 is formed on the anode layer 79, and a connection wiring 81 is connected to the electrode 82. An insulating film 80 is formed between the connection wiring 81 and the n-gate layer 78. In the resistor 50, the anode layer 79, the connection wiring 81, and the electrode 82 function as a signal line. The anode layer 79 functions as a resistor that limits the current flowing from the gate electrode 12 to the light-emitting element section 30.

[0043] If the oxidized region 74 is not formed in the resistor 50 region and leakage current from the light-emitting element 40 flows through the lower DBR layer 71, the resistor 50 region will erroneously light up. This is because the resistor 50 has a thyristor structure. The resistor 50 region includes at least the region where the anode layer 79 is formed. In other words, the light-emitting region of the present invention includes at least the region where the anode layer 79 is formed. Therefore, in the light-emitting chip 10 according to this embodiment, an oxidized region 74 is formed in the upper DBR layer 73 in the region where the resistor 50 is formed. The oxidized region 74 is formed, for example, by oxidizing the upper DBR layer 73 from the side surface of the resistor 50 region perpendicular to the X-X' line.

[0044] By forming an oxidized region 74 in the upper DBR layer 73 in the region where the resistor 50 is formed, leakage current from the light-emitting element 40 through the lower DBR layer 71 can be prevented from flowing to the cathode layer 76, p-gate layer 77, n-gate layer 78, and anode layer 79 in the region where the resistor 50 is formed.

[0045] Here, if leakage current from the light-emitting element 40 flows into the region where the resistor 50 is formed, the absence of the oxidized region 74 could result in light emission from the upper DBR layer 73 and the lower DBR layer 71 in the region where the resistor 50 is formed. Light emission consumes current, causing even more leakage current to flow toward the resistor 50. Even if light is not emitted from the upper DBR layer 73 and the lower DBR layer 71, the current may escape to the lower layer of the n-type substrate 70. Even if the current escapes to the lower layer of the n-type substrate 70, the amount of leakage current that escapes will increase to the region where the resistor 50 is formed. In this embodiment, even if leakage current flows, the amount of current is smaller than when the oxidized region 74 is not formed in the region where the resistor 50 is formed, and light is emitted in the region where the resistor 50 is formed or when the current escapes to other locations starting from the region where the resistor 50 is formed. In other words, this embodiment improves light-emitting efficiency compared to when the oxidized region 74 is not formed in the region where the resistor 50 is formed.

[0046] Depending on the oxidation process or the size of the region where the light-emitting element 40 is formed or the region where the gate electrode 12 is formed, the entire region where the resistor 50 is formed does not necessarily overlap with the oxidized region 74 formed in the upper DBR layer 73 when the light-emitting chip 10 is viewed in plan. The oxidized region 74 does not have to overlap the entire region where the resistor 50 is formed. In other words, the oxidized region 74 may be formed in part of the region where the resistor 50 is formed. By forming the oxidized region 74 so as to overlap part of the region where the resistor 50 is formed, even if leakage current flows from the light-emitting element 40, the leakage current from the light-emitting element 40 is less likely to flow in the region where the resistor 50 is formed.

[0047] 3, the oxidized region 74 may be formed in the region where the p-gate layer 77 is formed. By forming the oxidized region 74 also in the region where the p-gate layer 77 is formed, it is possible to more reliably prevent leakage current from the light-emitting element 40 from flowing into the region of the resistor 50.

[0048] Next, a specific example of an apparatus in which the light-emitting chip according to the above embodiment is used will be described.

[0049] 5 is a diagram showing an overview of a smartphone 900 using a light-emitting chip according to an embodiment of the present invention. The smartphone 900 includes a display 910 that displays information and a distance measuring unit 920 that measures the distance to an object. The smartphone 900 is an example of the light measurement device of the present invention.

[0050] The distance measuring unit 920 measures the distance between the smartphone 900 and an object to be measured by a Time of Flight (ToF) method. The distance measuring unit 920 includes a light emitting unit 921 and a light receiving unit 922. The light emitting unit 921 emits light toward the object to be measured. The light emitting unit 921 is provided with, for example, the light emitting chip 10 according to the first embodiment or the light emitting chip 100 according to the second embodiment. The light receiving unit 922 receives light emitted by the light emitting unit 921 and reflected by the object to be measured. The light receiving unit 922 is provided with, for example, a CMOS image sensor.

[0051] 6 is a diagram showing an example of the functional configuration of the smartphone 900. The control unit 930 includes, for example, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), etc., and controls the operation of the smartphone 900. The control unit 930 operates as a measurement unit 931 by reading and executing a control program stored in the ROM.

[0052] The measurement unit 931 controls the light-emitting unit 921 to emit light for a short period of time. That is, the light-emitting unit 921 emits light in pulses under the control of the measurement unit 931. The measurement unit 931 then measures the distance to the object by a time-of-flight method based on the travel distance of the light irradiated from the light-emitting unit 921 and received by the light-receiving unit 922. More specifically, the measurement unit 931 calculates the optical path length from when light is emitted from the light-emitting unit 921, reflected from the object to be measured, and to when it reaches the light-receiving unit 922, based on the time difference between when the light-emitting unit 921 emits light and when the light-receiving unit 922 receives the reflected light from the object to be measured. The positions of the light-emitting unit 921 and the light-receiving unit 922 and the distance between the light-emitting unit 921 and the light-receiving unit 922 are predetermined. Therefore, the measurement unit 931 can measure the distance from the light-emitting unit 921 and the light-receiving unit 922 to the object to be measured.

[0053] The smartphone 900 can obtain the distance to the object being measured by measuring the time it takes for light emitted by the light emitting unit 921 to be reflected by the object being measured and received by the light receiving unit 922.

[0054] In the above embodiment, the light-emitting chip 10 that irradiates light in a vertical direction has been exemplified, but the present invention is not limited to such an example. For example, as shown in Fig. 7, the present invention can be applied to a light-emitting element 1010 that irradiates light in a direction Lf that intersects with the substrate surface and is tilted forward from the propagation direction of the waveguide of the propagating light, and to a light-emitting device 1100 in which a plurality of light-emitting elements 1010 that irradiate light in the direction Lf are provided on a substrate 1102, as shown in Fig. 8.

[0055] The light-emitting device 1010 shown in the plan view (a) and cross-sectional view (b) along line A-A' in FIG. 7 includes an optical amplifier 1050, a widened portion 1062, and an optical coupling portion 1052. The optical amplifier 1050 amplifies and outputs light (seed light) coupled to the optical coupling portion 1052. As an example, the optical amplifier 1050 is a surface-emission type optical amplifier using a GaAs-based DBR waveguide. That is, the optical amplifier 1050 includes an N-electrode 1040 formed on the back surface of the substrate 1030, a lower DBR 1032 formed on the substrate 1030, an active region 1034, an upper DBR 1036, a non-conductive region 1060, a conductive region 1058, and a P-electrode 1018.

[0056] In the above embodiment, the oxidized region 74 is formed in the upper DBR layer 73 of the resistor 50 to provide insulation, thereby enabling the oxidized confinement to be formed in the same process as the oxidized confinement in the light-emitting element 40. However, the oxidized region may be provided in a layer other than the upper DBR layer 73.

[0057] In the above embodiment, an oxide film is used as the insulating layer, but the oxide film described in the above embodiment may be replaced with other means, such as ion implantation, to provide insulation, as long as insulation can be achieved.

[0058] In the above embodiment, the oxidized region 74 is formed in the region where the resistor 50 is formed to provide insulation, but the oxidized region 74 may also be formed in the region where the signal line 41 is formed to provide insulation. [Explanation of symbols]

[0059] 10 Light-emitting chip 11 Anode electrode 12 gate electrode 30 Light emitting element section 40 Light-emitting element 50 resistor 70 n-type substrate 71 Lower DBR layer 72 Resonator 73 Upper DBR layer 74 Oxidation Region 75 Tunnel Coupling Layer 76 cathode layer 77 p-gate layer 78 n-gate layer 79 Anode layer 90 Cathode electrode 900 smartphones 910 Display 920 Ranging section 921 Light-emitting part 922 Light receiving part

Claims

1. a semiconductor substrate; a light emitting element section formed in a partial region of the semiconductor substrate and including a plurality of light emitting elements for emitting light; a signal line formed on the semiconductor substrate and transmitting a signal to the light emitting element; an insulating layer formed between the signal line and the semiconductor substrate in a region of the signal line where light can be emitted; a resistor formed in the light-emitting region of the signal line to limit the current to the light-emitting element; Equipped with In the light-emitting device, an insulating layer is formed between the signal line and the semiconductor substrate in the region of the upper DBR layer of the resistor by an oxidized region or ion implantation.

2. The light emitting device according to claim 1 , further comprising a terminal formed on the semiconductor substrate, to which a signal to be transmitted to the light emitting element is input.

3. The light emitting device according to claim 2 , wherein a signal for causing said light emitting element to emit light is transmitted from said terminal to said signal line.

4. 2. The light emitting device according to claim 1, wherein the light emitting element section is made up of a plurality of areas, and the light emitting elements are connected to the signal lines for each of the plurality of areas.

5. The light emitting device according to claim 4 , wherein the signal lines are wired between the areas.

6. The light emitting device according to any one of claims 1 to 5, a light receiving unit that receives light emitted from the light emitting device and reflected by an object; a measuring unit that measures the distance to the object based on the flight distance of light emitted from the light emitting device and received by the light receiving unit; An optical measurement device comprising:

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