JP2023042124A - Light-emitting device and light-measuring apparatus - Google Patents

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

The present invention relates to a light emitting device and a light measuring device.

Patent Document 1 discloses a substrate in which a second semiconductor laminate is grown on a first semiconductor laminate via a tunnel junction layer or a group III-V compound layer having metallic conductivity; A plurality of light emitting elements composed of one semiconductor laminate, and a thyristor composed of the second semiconductor laminate, which sequentially drives the plurality of light emitting elements so that they can be turned on. and a driving portion.

Patent Document 2 includes a light-emitting portion in which a plurality of light-emitting element groups each having a plurality of light-emitting elements are arranged, and the light-emitting portion includes the light-emitting element for each of the plurality of light-emitting element groups along the arrangement. A light-emitting device is disclosed in which a plurality of light-emitting elements included in a group are arranged in parallel and sequentially set to a light-emitting or non-light-emitting state.

JP 2018-006502 A Japanese Patent Application Laid-Open No. 2020-120018

In a so-called monolithic light-emitting substrate in which a light-emitting element and a signal line for transmitting a signal to the light-emitting element are formed on the same substrate, if a leakage current from the light-emitting element portion is transmitted to the signal line, the signal line erroneously lights up.

SUMMARY OF THE INVENTION 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.

A light-emitting device according to a first aspect of the present invention comprises a semiconductor substrate, a light-emitting element section formed in a partial region of the semiconductor substrate and configured of a plurality of light-emitting elements that emit light, and a light-emitting element section formed on the semiconductor substrate. a signal line for transmitting a signal to the light emitting element; and an insulating layer formed between the signal line and the semiconductor substrate in a region where the signal line can emit light.

A light-emitting device according to a second aspect of the present invention is the light-emitting device according to the first aspect, further comprising a resistor formed in the region of the signal line capable of emitting light and limiting current to the light-emitting element, The insulating layer is formed in the area of the resistor.

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 area around the area of the resistor.

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 and receiving a signal to be transmitted to the light-emitting element.

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.

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 portion is composed of a plurality of areas, and the light-emitting element is connected to the signal line for each of the plurality of areas. .

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 line is wired between the areas.

A light measuring 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 the light emitting device. a measuring unit that measures the distance to the object based on the flight distance of the light emitted from the device and received by the light receiving unit.

According to the first aspect of the present invention, even when a leakage current is generated from the light emitting element portion, it is possible to prevent erroneous lighting of the signal line due to transmission of the leakage current from the light emitting element portion to the signal line. .

According to the second aspect of the present invention, by preventing leakage current from being transmitted to the resistor with the insulating layer, it is possible to prevent erroneous lighting of the resistor due to leakage current from the light emitting element section being transmitted to the resistor. .

According to the third aspect of the present invention, it is possible to more reliably prevent erroneous lighting of the resistor due to leakage current from the light emitting element section being transmitted to the resistor, compared to the case where only the resistor region is protected by the insulating layer. can.

According to the fourth aspect of the present invention, signals can be transmitted from the terminal to the light emitting element section.

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

According to the sixth aspect of the present invention, it is possible to cause the light emitting element to emit light in area units.

According to the seventh aspect of the present invention, the wiring area can be suppressed.

According to the light measuring device according to the eighth aspect of the present invention, even when leakage current occurs from the light emitting element, the leakage current from the light emitting element is prevented from flowing in the direction of the substrate through the signal line. A light emitting device can be used to measure the distance to an object.

1 is an explanatory diagram showing a light-emitting chip according to an embodiment of technology disclosed in a plan view; FIG. It is a figure which expands and shows the cross section of a light emitting element. It is a figure which expands and shows a resistor. 4 is a cross-sectional view showing a cross-sectional structure taken along the line X-X' of FIG. 3; FIG. 1 is a diagram showing an outline of a smart phone 900 using a light-emitting chip according to an embodiment; FIG. It is a figure which shows the functional structural example of a smart phone. It is a figure which shows the modification of a light-emitting device. It is a figure which shows the modification of a light-emitting device.

An example of an embodiment of the present disclosure will be described below with reference to the drawings. In each drawing, the same or equivalent components and portions are given the same reference numerals. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

In the following, a form 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 as an example. may be

FIG. 1 is an explanatory diagram showing a light-emitting chip according to an embodiment of the present invention in plan view. 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 .

The anode electrode 11 is an anode-side electrode formed on a part of the wiring extending from the anode electrode formed in 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 embodiment in which the anode electrodes 11 are provided at both ends of the light-emitting chip 10 will be described as an example.

The gate electrode 12 is an example of a terminal for inputting a signal to be transmitted to the light emitting element of the present invention, and is an electrode for supplying the light emitting element section 30 with a signal for causing the light emitting element section 30 to emit light through the signal line 41 . In this embodiment, as will be described later, the light emitting element section 30 consists of 12 areas 35 as shown in FIG. Therefore, the light-emitting chip 10 shown in FIG. 1 includes 12 gate electrodes 12 for independently causing the light-emitting elements 40 in each area to emit light. The current supplied to the anode electrode 11 causes the light emitting element 40 to emit light, so that the anode electrode 11 is supplied with power necessary for light emission. On the other hand, the voltage supplied to the gate electrode 12 is lower than the voltage supplied to the anode electrode 11 because it is sufficient to supply the gate electrode 12 with a signal to emit light. Specifically, the voltage supplied to the gate electrode 12 may be about 5V to 10V. The arrangement pattern of the gate electrodes 12 is not limited to the example shown in FIG. Also, the number of areas 35 is not limited to twelve.

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 the light emitting elements 40 formed on the light emitting chip 10 . In this embodiment, when the vertical direction in FIG. 1 is defined as a row, the light emitting elements 40 arranged in each row are arranged at predetermined intervals. On the other hand, when viewed in the left-right direction of FIG. 1, the light-emitting elements 40 are arranged at predetermined intervals while skipping one row. Adjacent rows are vertically shifted by half the size of the light emitting elements 40, and the light emitting elements 40 are arranged in a so-called zigzag pattern. However, the arrangement of the sending elements 40 is not limited to the zigzag pattern. For example, the light emitting elements 40 arranged in each row are arranged at predetermined intervals, and the positions of the light emitting elements 40 are shifted in the vertical direction between adjacent rows. They may be arranged in a so-called array. Also, the number of light-emitting elements 40 may be an appropriate number in consideration of the output power required for the light-emitting chip 10 and the like. In addition, in this embodiment, the light emitting element section 30 consists of 12 areas 35 as shown in FIG.

Further, in the present embodiment, the signal line 41 can be wired between the areas 35 in the light emitting element section 30 as shown in FIG. In other words, when the light-emitting element section 30 is viewed in plan, the signal line 41 does not overlap the area 35 except for the portion where the signal line 41 extends from the gate electrode 12 and is connected to the light-emitting element 40 in the area 35 . 35 are wired within the interval for partitioning them. The width of the signal line 41 in the lateral direction can be formed narrower than the width of each area 35 of the light emitting element section 30 in 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.

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

The light emitting element 40 includes an n-type substrate 70 using GaAs, a lower DBR (Distributed Bragg Reflector) layer 71 formed on the n-type substrate 70, a resonator 72 formed on the lower DBR layer 71, An upper DBR layer 73 formed on the resonator 72, a tunnel coupling layer 75 formed on the upper DBR layer 73, a cathode layer 76 formed on the tunnel coupling layer 75, and a p-gate formed on the cathode layer 76. It consists of a layer 77 , an n-gate layer 78 formed on the p-gate layer 77 and an anode layer 79 formed on the n-gate layer 78 . A cathode electrode 90 (back electrode) is formed on the back surface of the n-type substrate 70 . Furthermore, a gate electrode 12 is formed on the anode layer 79 .

The lower DBR layer 71 has 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). is a multilayer film reflector configured by alternately and repeatedly laminating two semiconductor layers different from each other. In this embodiment, the lower DBR layer 71 is n-type.

The upper DBR layer 73 is a multilayer reflector made by alternately and repeatedly laminating two semiconductor layers each having a predetermined thickness, eg, 0.25λ/n, and having different refractive indices. In this embodiment, the upper DBR layer 73 is n-type.

The resonator 72 resonates and amplifies the light emitted by 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 .

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

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. FIG. Also, an anode electrode 92 is formed on the anode layer 79 adjacent to the opening 83 .

An oxidized region 74 is formed in the upper DBR layer 73 in the region of the light emitting device 40 . The oxidized region 74 is an example of the insulating layer of the present invention, particularly an example of an oxide film, and has a function of blocking current. That is, by forming the oxidized region 74 in the region of the light emitting element 40, the current flowing from the anode electrode 82 toward the cathode electrode 90 can be reduced. By restricting the current flowing from the anode electrode 82 to the cathode electrode 90, the light-emitting chip 10 consumes less power than when the oxidized region 74 is not formed.

In this embodiment, the oxidized region 74 is formed by exposing at least the region where the oxidized region 74 is to be formed by etching and oxidizing a portion of the upper DBR layer 73 .

A resistor 50 for limiting the current flowing from the gate electrode 12 to the light emitting element section 30 is formed in the middle of the signal line 41 for transmitting the signal from the gate electrode 12 to the light emitting element section 30 . The place where the resistor 50 is formed may be between the gate electrode 12 and the light emitting element section 30 . FIG. 3 is an enlarged view of the resistor 50. As shown in FIG. 4 is a cross-sectional view showing the cross-sectional structure taken along the line X-X' of FIG.

The light-emitting chip 10 includes an n-type substrate 70 using GaAs, a lower DBR (Distributed Bragg Reflector) layer 71 formed on the n-type substrate 70, a resonator 72 formed on the lower DBR layer 71, An upper DBR layer 73 formed on the resonator 72, a tunnel coupling layer 75 formed on the upper DBR layer 73, a cathode layer 76 formed on the tunnel coupling layer 75, and a p-gate formed on the cathode layer 76. Layer 77 , n-gate layer 78 formed over p-gate layer 77 , and anode layer 79 formed over n-gate layer 78 . A cathode electrode 90 (back electrode) is formed on the back surface of the n-type substrate 70 .

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 electrodes 82 function as signal lines. The anode layer 79 serves as a resistor that limits current flowing from the gate electrode 12 to the light emitting element section 30 .

If the leakage current from the light emitting element 40 flows through the lower DBR layer 71 in a state where the oxidized region 74 is not formed in the region of the resistor 50, the region of the resistor 50 is erroneously lit. This is because the resistor 50 has a thyristor structure. The area of resistor 50 includes at least the area where anode layer 79 is formed. That is, 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 of the region of the resistor 50 perpendicular to the X-X' line.

An oxidized region 74 is formed in the upper DBR layer 73 in the region where the resistor 50 is formed so that the cathode layer 76, the p-gate layer 77, the n-gate layer 78, and the anode layer in the region where the resistor 50 is formed. 79 can prevent leakage current from flowing through the lower DBR layer 71 from the light emitting element 40 .

Here, when leakage current from the light emitting element 40 flows through the region where the resistor 50 is formed, if there is no oxidized region 74, the upper DBR layer 73 and the lower DBR layer 71 in the region where the resistor 50 is formed There is a possibility that it will emit light with. Since light emission consumes current, more leakage current flows to the resistor 50 side. Moreover, even if the upper DBR layer 73 and the lower DBR layer 71 do not emit light, the current may escape to the lower layer side of the n-type substrate 70 . Even if the current escapes to the lower layer side of the n-type substrate 70 , a larger amount of leakage current will flow into the region of the resistor 50 . In this embodiment, the oxidized region 74 is not formed in the region where the resistor 50 is formed. Even if a leakage current flows, the amount of current will be less than in the case of escaping to another place, and the current that can be used for light emission will be increased. In other words, this embodiment improves the luminous efficiency compared to the case where the oxidized region 74 is not formed in the region where the resistor 50 is formed.

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 becomes It does not always overlap with the oxidized region 74 formed in the upper DBR layer 73 at times. The oxidized region 74 does not have to overlap the entire area where the resistor 50 is formed. That is, the oxidized region 74 may be formed in part of the region where the resistor 50 is formed. Since the oxidized region 74 is formed so as to partially overlap the region where the resistor 50 is formed, even if a leakage current from the light emitting device 40 flows, the region where the resistor 50 is formed does not cover the light emitting device 40 . It becomes difficult for leakage current to flow from

The oxidized region 74 may be formed in the region where the p-gate layer 77 is formed in addition to the region of the n-gate layer 78 shown in FIG. Since the oxidized region 74 is also formed 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 .

Next, a specific example of a device using the light-emitting chip according to the above embodiment will be described.

FIG. 5 is a diagram showing an outline of a smart phone 900 using a light-emitting chip according to an embodiment of the invention. A smartphone 900 includes a display 910 that displays information and a distance measurement unit 920 that measures the distance to an object. Smartphone 900 is an example of the light measurement device of the present invention.

Distance measurement unit 920 measures the distance between smartphone 900 and an object to be distanced using the Time of Flight (ToF) method. The distance measuring section 920 includes a light emitting section 921 and a light receiving section 922 . The light emitting unit 921 irradiates light toward the distance measurement target. The light-emitting portion 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 the 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.

FIG. 6 is a diagram illustrating a functional configuration example of the smartphone 900. As illustrated in FIG. The control unit 930 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), 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.

The measurement unit 931 controls the light emitting unit 921 to emit light from the light emitting unit 921 for a short period of time. That is, the light emitting section 921 emits light in a pulsed manner under the control of the measuring section 931 . Then, the measuring unit 931 measures the distance to the object by the time of flight method based on the flight distance of the light emitted from the light emitting unit 921 and received by the light receiving unit 922 . More specifically, the measuring unit 931 determines the amount of light emitted from the light emitting unit 921 based on the time difference between the time when the light emitting unit 921 emitted the light and the time when the light receiving unit 922 received the reflected light from the object to be distance-measured. , the optical path length of the light reflected by the object to be distance-measured and reaching the light receiving unit 922 is calculated. The positions of the light-emitting portion 921 and the light-receiving portion 922 and the distance between the light-emitting portion 921 and the light-receiving portion 922 are predetermined. Therefore, the measuring unit 931 can measure the distance from the light emitting unit 921 and the light receiving unit 922 to the object to be measured.

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

In the above embodiment, the light-emitting chip 10 that emits light in the vertical direction was exemplified, but the present invention is not limited to such an example. For example, as shown in FIG. 7, a light emitting element 1010 in which light is emitted in a direction Lf that intersects the substrate surface and is inclined forward in the propagation direction of the waveguide of propagating light, and as shown in FIG. , and a light emitting device 1100 in which a substrate 1102 is provided with a plurality of light emitting elements 1010 that emit light in the direction Lf.

The light-emitting element 1010 shown in the plan view (a) and the cross-sectional view (b) along line A-A' of FIG. The optical amplification section 1050 has a function of amplifying the light (seed light) coupled to the optical coupling section 1052 and emitting it. The optical amplifier 1050 is, for example, a surface emitting optical amplifier using a GaAs-based DBR waveguide. That is, the optical amplifier section 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. is composed of

In the above embodiment, by forming the oxidized region 74 in the upper DBR layer 73 of the resistor 50 to insulate it, the oxidized constriction can be formed in the same process as the oxidized constriction in the light emitting element 40, but the upper DBR layer 73 The oxidized regions may be provided in other layers instead.

In the above embodiments, the oxide film was used as the insulating layer, but the oxide film described in the above embodiments may be replaced by other means such as ion implantation so as to provide insulation, if insulation can be provided. good.

In the above embodiment, the oxidized region 74 is formed in the region where the resistor 50 is formed to insulate it, but the oxidized region 74 may also be formed in the region where the signal line 41 is formed for insulation.

REFERENCE SIGNS LIST 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 oxidized region 75 tunnel coupling layer 76 cathode layer 77 p-gate layer 78 n Gate layer 79 Anode layer 90 Cathode electrode 900 Smart phone 910 Display 920 Distance measuring unit 921 Light emitting unit 922 Light receiving unit

Claims (8)

a semiconductor substrate;
a light emitting element section formed in a partial region of the semiconductor substrate and composed of 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 where the signal line can emit light;
A light emitting device. 2. The light-emitting device according to claim 1, further comprising a resistor formed in said light-emitting region of said signal line to limit current to said light-emitting element, said insulating layer being formed in said resistor region. . 3. The light emitting device according to claim 2, wherein said insulating layer is further formed in a predetermined region around said resistor region. 2. The light emitting device according to claim 1, further comprising a terminal formed on said semiconductor substrate and receiving a signal to be transmitted to said light emitting element. 5. The light-emitting device according to claim 4, wherein a signal for causing said light-emitting element to emit light is transmitted from said terminal to said signal line. 2. The light-emitting device according to claim 1, wherein said light-emitting element section comprises a plurality of areas, and said light-emitting element is connected to said signal line for each of said plurality of areas. 7. The light emitting device according to claim 6, wherein said signal line is wired between said areas. a light emitting device according to any one of claims 1 to 7;
a light receiving unit that receives light emitted from the light emitting device and reflected by an object;
a measurement unit that measures the distance to the object based on the flight distance of the light emitted from the light emitting device and received by the light receiving unit;
A light measuring device comprising:

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