CN115642473A

CN115642473A - Laser array and forming method thereof, light source module and laser radar

Info

Publication number: CN115642473A
Application number: CN202110811956.XA
Authority: CN
Inventors: 费嘉瑞; 陈杰; 向少卿
Original assignee: Hesai Technology Co Ltd
Current assignee: Hesai Technology Co Ltd
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2023-01-24

Abstract

A laser array and a forming method thereof, a light source module and a laser radar are provided, wherein the laser array comprises a plurality of lasers arranged on a semi-insulating substrate, and each laser comprises at least one light-emitting unit; the light emitting unit includes: the laser comprises a first contact layer, a light-emitting laminated layer and a second contact layer which are sequentially arranged on a substrate, wherein the first contact layer between at least two lasers is isolated; each laser comprises a first electrode and a second electrode, wherein the first electrodes of at least two lasers are connected, the second electrodes of at least two lasers are connected, and the first electrodes and the second electrodes of any two lasers are not connected at the same time. The embodiment of the invention is beneficial to reducing the number of routing bonding pads of the laser array and reducing the packaging cost.

Description

Laser array and forming method thereof, light source module and laser radar

Technical Field

The embodiment of the invention relates to the field of laser detection, in particular to a laser array, a forming method thereof, a light source module and a laser radar.

Background

Laser radar (LIDAR) has assumed important tasks in autonomous driving, such as road edge detection, obstacle identification, and real-time location and mapping (SLAM). The laser radar can accurately measure the position (distance and angle), the motion state (speed, vibration and attitude) and the shape of a target, and detect, identify, distinguish and track the target. Because of the advantages of high measuring speed, high precision, long distance measurement and the like, the laser radar is widely applied to unmanned vehicles.

In particular, a LIDAR system includes a laser emitting system and a light receiving system. The laser emission system comprises a light emission unit which generates emission light pulses, the emission light pulses are incident on a target object to be reflected and generate echo beams, and finally the echo beams are received by a light receiving system. The receiving system accurately measures the travel time of an incident light pulse from emission to reflection. Since the light pulse propagates at the speed of light, which is known, the propagation time can be converted into a measure of the distance.

The transmitting unit of the multi-line laser radar comprises a plurality of lasers which respectively transmit light pulses, and a plurality of corresponding probes respectively receive corresponding echo light beams, calculate propagation time and target object distance and obtain a plurality of data points. At present, the encapsulation of a plurality of lasers at the transmitting end of a laser radar mainly has two forms: firstly, a plurality of independent lasers are respectively mounted on a Printed Circuit Board (PCB), which is limited by the requirement of mounting precision, and space is reserved for mounting deviation between adjacent lasers, so that the line spacing of the laser radar light source is too large; the other type is that a plurality of lasers are integrated on the same chip, and then the chip is pasted on the PCB, so that the distance between the light source lines can be reduced, but with the increase of the number of laser radar lines, bonding pads which are in one-to-one correspondence with the lasers need to be arranged on one chip, and each bonding pad is connected with a driving piece on the PCB in a routing mode respectively, so that the problem that the packaging cost and the complexity are high exists in the existing laser radar.

Disclosure of Invention

The embodiment of the invention provides a laser array, a forming method thereof, a light source module and a laser radar, and aims to reduce the number of routing bonding pads of the laser array and reduce the packaging cost.

In order to solve the above problem, an embodiment of the present invention provides a laser array including a plurality of lasers disposed on a semi-insulating substrate, each laser including at least one light emitting cell; the light emitting unit includes: a first contact layer, a light emitting laminate and a second contact layer provided on a substrate in this order; wherein the first contact layer between the at least two lasers is isolated; each laser comprises a first electrode and a second electrode, wherein the first electrodes of at least two lasers are connected, the second electrodes of at least two lasers are connected, and the first electrodes and the second electrodes of any two lasers are not connected at the same time.

Correspondingly, the embodiment of the invention also provides a light source module, which comprises a laser array and a driving plate; the laser array is provided by the embodiment of the invention; the drive plate includes: a first decoder and a second decoder; the first driving circuit is connected with the first decoder and used for providing a first driving signal to the first electrode based on an output signal of the first decoder; the second driving circuit is connected with the second decoder and used for providing a second driving signal to the second electrode based on the output signal of the second decoder; one or more lasers operate based on a first drive signal and a second drive signal.

Correspondingly, an embodiment of the present invention further provides a laser radar, including: the device comprises a transmitting module and a receiving module; the transmitting module comprises the light source module provided by the embodiment of the invention and is used for emitting a detection light beam; the receiving module comprises one or more photoelectric detectors and is used for receiving the echo light beam reflected by the target object and converting the echo light beam into an electric signal.

Correspondingly, an embodiment of the present invention further provides a method for forming a laser array, including: providing a substrate, wherein the substrate is a semi-insulating substrate; forming a first contact layer on the substrate; forming a light-emitting laminated layer on the first contact layer, wherein the light-emitting laminated layer comprises a first reflector, an active region and a second reflector which are sequentially formed from bottom to top; etching the light-emitting laminated layer to form a plurality of lasers; and etching the first contact layer between at least two lasers to form a groove for exposing the substrate, so that the first contact layers of the two lasers are isolated.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

in the laser array provided by the embodiment of the invention, the first contact layers between at least two lasers are isolated, the first electrodes of at least two lasers are connected, the second electrodes of at least two lasers are connected, the first electrodes and the second electrodes of any two lasers are not simultaneously connected, and compared with the fact that each light-emitting area is provided with a corresponding routing area, the number of routing areas is reduced, and the area occupied by the routing areas is correspondingly reduced; in addition, the anode and the cathode of the laser are respectively connected with a driving circuit, and the channel laser emits light when the two stages of driving circuits are both conducted, so that the number of the driving circuits can be reduced; in summary, the embodiment of the invention is beneficial to reducing the number of routing bonding pads of the laser array and reducing the packaging cost.

Drawings

FIG. 1 is a top view of a laser of the disclosed technology;

FIG. 2 is a schematic cross-sectional view of the laser of FIG. 1;

FIG. 3 is a schematic cross-sectional view of a laser according to the prior art;

FIG. 4 is a top view of the laser of FIG. 3;

FIG. 5 is a schematic cross-sectional view of a laser according to an embodiment of the present invention;

FIG. 6 is a top view of one embodiment of a laser of the present invention;

FIG. 7 is a schematic cross-sectional view of another embodiment of a laser of the present invention;

FIG. 8 is a top view of an illustrative first electrode of another embodiment of a laser of the present invention;

FIG. 9 is a top view of an illustrative second electrode of another embodiment of a laser of the present invention;

FIG. 10 is a schematic structural diagram of an embodiment of a driving board in the light source module according to the present invention;

fig. 11 to 17 are schematic structural diagrams corresponding to steps in an embodiment of a method for forming a laser device according to the present invention.

Detailed Description

As known in the background art, the laser radar has the problems of high packaging cost and complexity. The cause of the problem is analyzed below.

Referring collectively to fig. 1 and 2, a top view and a cross-sectional view, respectively, of an emission unit of a laser array are shown.

As shown in fig. 1 and fig. 2, in the multi-line lidar, a separate laser chip is used for each line of the transmitting end, wherein 10 is a light source area, and 11 is a routing area. To reduce the line spacing, the light source may be directly attached to the PCB using a laser die having a cross-sectional structure as shown in fig. 2. As an example, each laser chip includes a plurality of laser light emitting points of a common cathode 12 substrate, and anode contact metals are connected to each other through an interconnection metal layer 13. The size of the bare laser is limited by the step of chip mounting, when two adjacent laser chips are mounted on a PCB, the bare laser is limited by the precision of the chip mounting, a certain size needs to be reserved between the chips, and the mutual interference of the chips caused by the deviation of the chip mounting is avoided, so that the line spacing of the radar light source is larger, and the improvement by a large margin is difficult.

In addition, the cathode of each laser chip is attached to a cathode bonding pad of the PCB, the anode of each laser chip is connected to an anode bonding pad of the PCB, a plurality of lasers of the multi-line laser radar need to be sequentially pasted and electrically connected in a routing mode, and the packaging cost and complexity are greatly increased along with the increase of the number of radar lines.

Referring to fig. 3 and 4 in combination, one method for reducing the package cost and complexity is to integrate the multi-line laser on the same chip, and fabricate the laser light emitting region 20 of the multi-line light source and the common cathode 22 of the multi-line laser on one die, where the laser anode contact metals of one line are also connected through the anode interconnection metal layer 23, the anode interconnection metal layers 23 of different lines are isolated from each other, and the interval between two adjacent lasers can be reduced. The multi-line laser bare chip is a whole chip, the anode drive is adopted to gate the laser of a certain line to emit light, and only one-time surface mounting is needed, so that the packaging cost and the complexity are reduced.

However, when the chip is applied to a high-line-count laser radar, each line of laser needs one routing area 21, for example, a 32-line laser is integrated on one laser chip, and 32 routing areas 21 need to be left at the edge of the light-emitting area 20, which occupies a large chip area; and the number of wire bonding increases with the increase of the number of radar lines, which is also not favorable for reducing the packaging cost. In addition, each line laser requires a driving circuit, which also creates a serious challenge for PCB layout.

In order to solve the technical problem, embodiments of the present invention provide a laser array, where first contact layers between at least two lasers are separated, first electrodes of the at least two lasers are connected, second electrodes of the at least two lasers are connected, and the first electrodes and the second electrodes of any two lasers are not connected at the same time, and compared with each light-emitting region having a corresponding wire bonding region, the number of wire bonding regions is reduced, and the area occupied by the wire bonding region is correspondingly reduced; in addition, the anode and the cathode of the laser are respectively connected with a driving circuit, and the channel laser emits light when the two stages of driving circuits are both conducted, so that the number of the driving circuits can be reduced; in summary, the embodiment of the invention is beneficial to reducing the number of routing bonding pads of the laser array and reducing the packaging cost.

In order to make the aforementioned objects, features and advantages of the embodiments of the present invention comprehensible, specific embodiments accompanied with figures are described in detail below.

Referring to fig. 5 and 6, schematic structural diagrams of an embodiment of the laser array of the present invention are shown. Wherein fig. 5 shows a schematic cross-sectional structure and fig. 6 shows a corresponding top view.

In this embodiment, the laser array includes:

a plurality of lasers 300 disposed on the semi-insulating substrate 100, each laser 300 including at least one light emitting cell 200. Fig. 5 and 6 illustrate an example in which each laser includes one light emitting unit.

The laser of the embodiment is an area array laser. More specifically, a Vertical-Cavity Surface-Emitting Laser (VCSEL) is exemplified here.

The plurality of lasers are arranged in a matrix array or a staggered array.

It should be noted that, the light emitting units 200 are filled with the isolation material 130 to realize the spacing between the light emitting units 200. Specifically, the isolation material 130 is an insulating material.

In this embodiment, the light emitting unit 200 includes: a first contact layer 110, a light emitting stack, and a second contact layer 120 are sequentially disposed on the substrate 100.

The substrate 100 is used to provide a process platform.

The substrate 100 is a semi-insulating (s.i.) substrate 100 such that the substrate 100 is not electrically conductive, thereby isolating the first electrodes of adjacent lasers.

In this embodiment, the material of the substrate 100 is gallium arsenide. In other embodiments, the material of the substrate may also be gallium nitride, silicon, or other III/V compounds.

In other embodiments, the substrate 100 may also serve as a base for the formation of micro-lenses, and thus the material of the substrate 100 may also be a material suitable for process requirements or easy integration.

In this embodiment, the first contact layer 110 is a cathode contact layer of the laser 300, and is used for connecting to a negative electrode of a driving circuit. Specifically, the first contact layer 110 is an N + + contact layer (i.e., a high-concentration N-type doped layer).

Wherein the first contact layer 110 between at least two lasers 300 is isolated.

The light-emitting laminated layer comprises a first reflector 101, an active region 103 and a second reflector 102 which are sequentially arranged along a preset direction. In this embodiment, the preset direction is shown as a Y1 direction in the figure.

Wherein the active region 103 is used for radiating photons, said first mirror 101 and second mirror 102 constitute a resonant cavity for forming coherent oscillation of the radiated photons, providing a sufficiently strong injection current so that the photons can form a lasing against various losses of the device itself, after which the laser light exits the mirror as an exit mirror. In general, VCSEL emission light is located in the near infrared band.

In this embodiment, the laser 300 is a vertical cavity surface emitting laser, and the first mirror 101 and the second mirror 102 are Distributed Bragg Reflectors (DBRs).

The distributed Bragg reflector is a multilayer structure and is formed by alternately arranging two optical films with different refractive indexes. Fresnel reflection occurs at each interface of the two optical films. At the operating wavelength, the optical path difference of the reflected light at two adjacent interfaces is half wavelength, and in addition, the reflection at the interfaces also causes the optical path difference of half wavelength. Thus, all reflected light at the interface for light at the operating wavelength is coherently enhanced.

It should be noted that the reflectivities of the two DBRs are different, wherein the reflectivity of the DBR on one side is close to 100% and can be used as a total reflection mirror of the resonant cavity, and the reflectivity of the DBR on the other side is relatively low and can be used as an exit mirror of the resonant cavity.

In this embodiment, the light emitting direction (i.e. the direction of the black arrow in the figure) of the laser 300 is the same as the predetermined direction, that is, the light emitting direction of the laser 300 is from bottom to top as shown in the figure, so the first reflector 101 is a total reflector, and an N-type DBR is used.

The DBR is formed by alternately forming two optical films with different refractive indexes, such as Al _x Ga _1-x As/Al _1-y Ga _y As, where x and y may be different. And the optical path length of each optical film is lambda/4, wherein lambda is the working wavelength of the laser.

The active region 103, through the multiple quantum well structure, establishes a basis for realizing an inversion distribution of internal carriers to radiate photons.

For example, the active region 103 includes indium gallium arsenide (GaInAs)/gallium arsenide (GaAs) quantum wells.

And a second mirror 102 for cooperating with the first mirror 101 to form a resonant cavity. In order to make the laser light exit from the bottom to the top, the second reflector 102 is an exit mirror. In particular, said second mirror 102 is also a distributed Bragg mirror, formed by two optical films of different refractive index alternately, such as Al _x Ga _1-x As/Al _1-y Ga _y As, where x and y may be different. And the optical length of each optical film is lambda/4, wherein lambda is the working wavelength of the laser.

In other embodiments, the first reflector 101 and the second reflector 102 may be made of other dielectric materials.

It should also be noted that the first mirror 101 and the second mirror 102 are doped to reduce their electrical resistance. Specifically, the doping types of the first mirror 101 and the second mirror 102 are different. In this embodiment, the first mirror 101 is an N-doped DBR, and the second mirror 102 is a P-doped DBR.

In this embodiment, the second contact layer 120 is an anode contact layer of the laser and is used for connecting to the anode of the driving circuit. Specifically, the second contact layer 120 is an anode contact metal.

Each laser 300 comprises a first electrode 201 and a second electrode 202, wherein the first electrodes 201 of at least two lasers 300 are connected, the second electrodes 202 of at least two lasers 300 are connected, and the first electrodes 201 and the second electrodes 202 of any two lasers 300 are not connected at the same time.

The first electrode 201 is electrically connected to the first contact layer 110, and the second electrode 202 is electrically connected to the second contact layer 120. Specifically, the first electrode 201 is used for electrically connecting a first driving circuit and the first contact layer 110, and transmitting a driving signal of an external circuit to the first contact layer 110; the second electrode 202 is used to realize electrical connection between a second driving circuit and the second contact layer 120, and transmit a driving signal of an external circuit to the second contact layer 120.

Compared with the light-emitting regions respectively provided with corresponding routing regions, the first contact layer 110 between the at least two lasers 300 is isolated, the first electrodes 201 of the at least two lasers 300 are connected, two or more lasers 300 connected with the first electrodes 201 share a cathode drive, the first electrodes 201 of the lasers 300 are all connected to the same cathode pad 203, and further connected to the same cathode drive circuit through the cathode pad 203; the second electrodes 202 of at least two lasers 300 are connected, two or more lasers 300 connected with the second electrodes 202 share anode drive, the second electrodes 202 of the lasers 300 are all connected to the same anode bonding pad 204 and further connected to the same anode drive circuit through the anode bonding pad 204, the first electrodes 201 and the second electrodes 202 of any two lasers 300 are not connected at the same time, and therefore the cathode drive circuit and the anode drive circuit can be matched to gate any one laser 300.

It is understood by those skilled in the art that the common cathode and common anode manner of the laser shown in fig. 6 is only an illustration, and the interconnection or isolation between the first electrode 201 and the second electrode 202 between the multiple lasers can be set by those skilled in the art, and all of them are within the scope of the present invention. For example, the anode pad is denoted at 203, the cathode pad is denoted at 204 in fig. 6, the first electrodes 201 of every two lasers are connected to the same cathode pad 204, and the second electrodes of the four lasers, which are isolated from each other by the first electrodes 201, are connected to the same anode pad 203, so that the technical effect of using the cathode driving circuit and the anode driving circuit to cooperate to gate any one laser 300 can be obtained.

In summary, the number of the wire bonding regions is reduced, the area occupied by the wire bonding regions is correspondingly reduced, and the packaging cost of the laser is reduced.

Specifically, the first electrode 201 is disposed around the first mirror 101 of the light emitting unit 200, and the first contact layers 110 between the lasers 300, to which the first electrodes 201 are not connected, are isolated from each other.

The first electrode 201 is located on a side of the first contact layer 110 facing the active region 103, and connects the first contact layers 110 of at least two lasers 300.

The isolation material 130-2 between the lasers 300, which are not connected to the first electrode 201, is in contact with the substrate 100, so that the first contact layer 110 of the corresponding laser 300 and the first electrode 201 are electrically isolated from each other.

The second electrode 202 is located on a side of the second contact layer 120 facing away from the active region 103, and connects the second contact layers 120 of at least two lasers 300.

In this embodiment, each laser 300 includes a plurality of light emitting cells 200, and the second contact layers 120 of the plurality of light emitting cells 200 are connected through the second electrode 202.

Specifically, the first contact layers 110 of the plurality of light emitting cells 200 of each laser 300 are connected, the second contact layers 120 are connected by the second electrodes 202, the plurality of light emitting cells 200 are arranged in a matrix or honeycomb shape to constitute light emitting regions of the lasers 300, and the plurality of light emitting cells 200 can emit light in response to the same driving signal, so that the plurality of light emitting cells 200 can be regarded as one laser 300 as a whole.

The second electrode 202 is disposed on the surface of the isolation material 130, and connects the second contact layers 120 of at least two lasers 300.

In this embodiment, the light emitting direction (i.e. the black arrow direction in the figure) of the laser 300 is the same as the preset direction, and light emitting holes (not labeled) are formed in the second contact layer 120 and the second electrode 202, so that light can be emitted normally.

The first electrode 201 and the second electrode 202 may be made of a non-light-transmissive material. Specifically, the first electrode 201 and the second electrode 202 are interconnection metal layers. The interconnection metal layer may be a metal material such as copper or aluminum.

In this embodiment, the laser array is divided into: the laser comprises M1 groups of lasers, wherein each group comprises N1 lasers, and first electrodes 201 of the N1 lasers are connected, wherein the product of M1 and N1 is the total number of the lasers; and/or, the laser array is divided into: and M2 groups of lasers, wherein each group comprises N2 lasers, and second electrodes 202 of the N2 lasers are connected, wherein the product of M2 and N2 is the total number of the lasers, and N2 is not less than M1.

In a preferred embodiment, M1= N2 and M2= N1 are provided, so that the total number of bonding areas available for the first electrode 201 and the second electrode 202 is minimized, and the sum of the corresponding required anode driving circuit and cathode driving circuit is minimized, thereby further reducing the packaging cost.

Fig. 7 to 9 are schematic structural diagrams of another embodiment of the laser array of the present invention. Fig. 7 is a schematic cross-sectional structure diagram of another embodiment of a laser array, and fig. 8 and 9 are top views corresponding to fig. 7. The laser array according to the embodiment of the present invention is the same as the laser array according to the previous embodiment, and the description thereof is omitted. The laser array of the embodiment of the present invention is different from the previous embodiments in that: the light emitting direction (as indicated by the black arrow in fig. 7) of the laser 300a is opposite to the preset direction Y1.

That is, the laser 300a is a backside illumination (BSI) laser, thereby improving the application flexibility of the embodiment of the present invention. Correspondingly, the embodiment of the invention can also reduce the number of the driving circuits of the back-side light-emitting laser, thereby being beneficial to reducing the number of routing bonding pads of the laser array, reducing the area occupied by routing areas and reducing the packaging cost.

Specifically, the laser 300a is a back-side emitting laser, and the substrate 100a may further have a micro lens structure (not shown) on a surface facing away from the active region 103 for converging light formed by the light emitting stack.

Accordingly, in the light emitting stack, the first reflecting mirror 101a is an exit mirror, and light exits from one side of the first reflecting mirror 101 a; the second mirror 102a is a total reflection mirror.

Accordingly, as shown in the figure, in the present embodiment, the second contact layer 120a and the second electrode 202a do not need to reserve a light hole.

In this embodiment, in order to reduce light absorption by the substrate 100a, the substrate 100a may be thinned during the fabrication of the laser array.

For a detailed description of the laser array according to the embodiment of the present invention, please refer to the corresponding description in the foregoing embodiments, which is not repeated herein.

In order to solve the technical problem, an embodiment of the present invention further provides a light source module, which includes a laser and a driving board.

Wherein, the laser is the laser of the embodiment of the present invention, and the technical details refer to the related description of the foregoing embodiment.

Referring collectively to fig. 10, there is shown a block circuit diagram of one embodiment of the driver board of the present invention.

The driving board may be an Integrated Circuit (IC) chip or a Printed Circuit Board (PCB).

The driving board includes: a first decoder 301 and a second decoder 302; a first driving circuit 310 connected to the first decoder 301, for providing a first driving signal to the first electrode 201 based on an output signal of the first decoder 301; a second driving circuit 320 connected to the second decoder 302, for providing a second driving signal to the second electrode 202 based on the output signal of the second decoder 302; the one or more lasers operate based on the first drive signal and the second drive signal.

In this embodiment, the first decoder 301 may be a MUX (multiplexer) for selecting to output signals to one or more first driving circuits 310; the second decoder 302 may also be a MUX for selecting output signals to one or more second driving circuits 320.

One or more lasers operate based on the first driving signal and the second driving signal, and when the first driving circuit 310 and the second driving circuit 320 of the same laser are simultaneously gated, the lasers emit light, so that bipolar addressing is realized, and the number of driving circuits can be reduced.

The driving circuit comprises a driving switch for controlling the on-off of a driving signal, and when the driving switch is switched on, the driving signal is injected into the laser to control the laser to emit light; when the drive switch is turned off, the laser stops emitting light. In an IC chip, the driving switch may be a MOS switch, such as a PMOS or NMOS. In the PCB board, the driving switch may be a GaN switch.

In this embodiment, the laser array is divided into: the laser device comprises M1 groups of lasers, wherein each group comprises N1 lasers, first electrodes of the N1 lasers are connected, and the product of M1 and N1 is the total number of the lasers; the number of the first driving circuits is M1, and the M1 first driving circuits are respectively connected with the first electrodes of the M1 groups of lasers; therefore, only M1 first driving circuits, N1 and second driving circuits are needed in the embodiment, and the number of the driving circuits is favorably reduced.

In a specific implementation, the number of required drive circuits can be minimized by setting the grouping of the laser arrays such that the values of M1, N1 minimize the sum of M1 and N1.

In other embodiments, the laser array is divided into: m2 groups of lasers, wherein each group comprises N2 lasers, and second electrodes of the N2 lasers are connected, wherein the product of M2 and N2 is the total number of the lasers, and N2 is not less than M1; the number of the second driving circuits is M2, and the M2 second driving circuits are respectively connected with the second electrodes of the M2 groups of lasers; therefore, only M2 second driving circuits and N2 first driving circuits are needed in the embodiment, and the quantity of the driving circuits is favorably reduced.

In a specific implementation, the number of required drive circuits can be minimized by arranging the grouping of the laser arrays such that the values of M2, N2 minimize the sum of M2 and N2.

Correspondingly, the invention also provides a laser radar which comprises a transmitting module and a receiving module.

The transmitting module comprises the light source module provided by the embodiment of the invention and is suitable for emitting a detection light beam; the receiving module comprises one or more photoelectric detectors and is suitable for receiving the echo light beams reflected by the target object and converting the echo light beams into electric signals.

The embodiment of the invention reduces the number of routing bonding pads of the laser array, reduces the packaging cost, correspondingly reduces the line light source spacing of the laser radar, obtains high linear density and is beneficial to reducing the cost of the laser radar.

The plurality of lasers are arranged in a matrix array or a staggered array.

Correspondingly, the invention also provides a forming method of the laser. Fig. 11 to 17 are schematic structural diagrams corresponding to steps in an embodiment of a method for forming a laser according to the present invention.

The following describes the method for forming the laser in this embodiment in detail with reference to the accompanying drawings.

Referring to fig. 11, a substrate 100 is provided, the substrate 100 being a semi-insulating substrate.

The substrate 100 is used to provide a process platform.

The substrate 100 is a semi-insulating (s.i.) substrate 100.

With continued reference to fig. 11, a first contact layer 101 is formed on the substrate 100.

In this embodiment, the first contact layer 110 is a cathode contact layer of a laser, and is used for connecting to a negative electrode of a driving circuit. Specifically, the first contact layer 110 is an N + + contact layer (i.e., a high concentration N-type doped layer).

With continued reference to fig. 11, a light emitting stack including a first mirror 101, an active region 103, and a second mirror 102 formed in this order from bottom to top is formed on the first contact layer 101.

In this embodiment, the preset direction is shown as a Y1 direction in the figure.

Wherein the active region 103 is used for radiating photons, said first mirror 101 and second mirror 102 constitute a resonant cavity for forming coherent oscillation of the radiated photons, providing a sufficiently strong injection current so that the photons can form a lasing against various losses of the device itself, after which the laser light exits the mirror as an exit mirror. In general, VCSEL emission light is in the near infrared band.

In this embodiment, the laser is a vertical cavity surface emitting laser, and the first mirror 101 and the second mirror 102 are Distributed Bragg Reflectors (DBRs).

The distributed Bragg reflector is a multilayer structure and is formed by alternately arranging two optical films with different refractive indexes. Fresnel reflection occurs at each interface of the two optical films. When the wavelength is working, the optical path difference of the reflected light at two adjacent interfaces is half wavelength, and in addition, the reflection at the interfaces also causes the optical path difference of half wavelength. Thus, all reflected light at the interface for light at the operating wavelength undergoes coherence enhancement.

It should be noted that the reflectivities of the two DBRs are different, wherein the reflectivity of one DBR is close to 100% and can be used as a total reflection mirror of the resonant cavity, and the reflectivity of the other DBR is relatively low and can be used as an exit mirror of the resonant cavity.

In this embodiment, the light emitting direction (i.e., the direction of the black arrow in the figure) of the laser is the same as the predetermined direction, i.e., the light emitting direction of the laser is from bottom to top as shown in the figure, so the first reflector 101 is a total reflector and employs an N-type DBR.

The distributed Bragg reflector is formed by alternately forming two optical films with different refractive indexes, such as Al _x Ga _1-x As/Al _1-y Ga _y As, where x and y may be different. And the optical length of each optical film is lambda/4, wherein lambda is the working wavelength of the laser.

The active region 103, through a multiple quantum well structure, establishes a basis for realizing an inversion distribution of internal carriers to radiate photons.

And a second mirror 102 for cooperating with the first mirror 101 to form a resonant cavity. In order to make the exit light of the laser exit from bottom to top, the second reflector 102 is an exit mirror. In particular, the second mirror 102 is also a distributed Bragg mirror, crossed by two optical films of different refractive indexAlternatively, e.g. Al _x Ga _1-x As/Al _1-y Ga _y As, where x and y may be different. And the optical path length of each optical film is lambda/4, wherein lambda is the working wavelength of the laser.

In other embodiments, the first mirror 101 and the second mirror 102 may be made of other dielectric materials.

Note that the first mirror 101 and the second mirror 102 are doped to reduce their electrical resistance. Specifically, the doping types of the first mirror 101 and the second mirror 102 are different. In this embodiment, the first mirror 101 is an N-type doped DBR, and the second mirror 102 is a P-type doped DBR.

In this embodiment, a current confinement layer 105 is further formed between the active region 103 and the second mirror 102.

As an example, the material of the current confinement layer 105 is aluminum arsenide or aluminum gallium arsenide.

With continued reference to figure 11, a second contact layer 120 is formed on the second mirror 102.

In this embodiment, the second contact layer 120 is an anode contact layer of the laser and is used for connecting with the anode of the driving circuit. Specifically, the first contact layer 110 is an anode contact metal.

In this embodiment, the light emitting direction of the laser is the same as the preset direction, and a light emitting hole is formed in the second contact layer 120, so that light can be emitted normally.

Referring to fig. 12 and 13, which show a schematic cross-sectional structure and a corresponding top view, respectively, the light emitting stack is etched to form a plurality of lasers 300.

Wherein the first contact layer 110 between at least two lasers 300 is etched to form a trench 111 exposing the substrate 100, isolating the first contact layers 110 of the two lasers 300.

In this embodiment, the step of etching the light emitting stack to form a plurality of lasers 300 includes: etching the light emitting laminate to form a plurality of light emitting units 200; the laser 300 includes at least one light emitting cell 200.

In this embodiment, the step of forming a plurality of lasers 300 further includes: after etching the light-emitting stack, the sidewall of the current confinement layer 105 is oxidized, so that part of the material at the edge of the current confinement layer 105 is oxidized into the insulating ring 106, and the remaining current confinement layer 105 has conductivity to serve as a current passing hole 107.

By forming the insulating ring 106 and the through hole 107, the current flowing through the second electrode is concentrated in the center of the active region 103 by being limited by the oxide aperture.

In this embodiment, the insulating ring 106 is made of aluminum oxide or aluminum gallium oxide.

Referring to fig. 14 and fig. 15 in combination, respectively showing a schematic cross-sectional structure and a corresponding top view, in this embodiment, the method for forming the laser array further includes: after forming the plurality of lasers 300, a first electrode 201 is formed on a side of the first contact layer 110 facing away from the substrate 100, and the first electrodes 201 of at least two lasers 300 are connected.

The first electrode 201 is electrically connected to the first contact layer 110. Specifically, the first electrode 201 is used to realize electrical connection between a first driving circuit and the first contact layer 110, so as to transmit a driving signal of an external circuit to the first contact layer 110.

The first electrode 201 may be made of a non-light-transmissive material. Specifically, the first electrode 201 is an interconnection metal layer. The interconnection metal layer may be a metal material such as copper or aluminum.

In this embodiment, after the second contact layer 120 is formed, the light emitting stack is etched to form a plurality of lasers 300. In other embodiments, the light emitting stack may be etched to form a plurality of lasers, and then the second contact layer is formed.

Referring to fig. 16 and 17, which respectively show a schematic cross-sectional structure and a corresponding top view, the method of forming the laser array further comprises: an isolation material 130 is filled between the light emitting cells 200.

And an isolation material 130 for realizing a space between the light emitting cells 200. Specifically, the material of the isolation material 130 is an insulating material.

The isolation material 130 between the lasers 300, which are not connected to the first electrode 201, is in contact with the substrate 100, so that electrical isolation is achieved between the first contact layer 110 of the corresponding laser 300 and the first electrode 201.

With continued reference to fig. 16 and 17, the method of forming the laser array further includes: after the trench is formed, a second electrode 202 is formed on the surface of the second contact layer 120, the second electrode 202 connects the second contact layers 120 of at least two lasers 300, and the first contact layer 110 is isolated between the lasers 300 connected by the second contact layers 120.

The second electrode 202 is electrically connected to the second contact layer 120, and the second electrode 202 is used for electrically connecting a second driving circuit to the second contact layer 120 and transmitting a driving signal of the driving circuit to the second contact layer 120.

Further, in a region where the second electrode 202 is not disposed, the isolation material 130 is etched to form a trench (not shown) in contact with the first electrode 201; or the trench may be masked before filling the isolation material 130 to form a trench in contact with the first electrode 201. The trench is then filled with an electrode material to form a contact region 201-1 of the first electrode on the surface of the isolation material 130. The contact region 201-1 may be a pad for electrically connecting with a driving circuit, and the contact region 201-1 is electrically connected with the first electrode 201 and the first contact layer 110 to transmit a driving signal of the driving circuit to the first contact layer 110.

Each laser comprises a first electrode 201 and a second electrode 202, wherein the first electrodes 201 of at least two lasers 300 are connected, the second electrodes 202 of at least two lasers 300 are connected, and the first electrodes 201 and the second electrodes 202 of any two lasers 300 are not connected at the same time.

Compared with the light-emitting regions respectively provided with corresponding routing regions, the first contact layer 110 between the at least two lasers 300 is isolated, the first electrodes 201 of the at least two lasers 300 are connected, two or more lasers 300 connected with the first electrodes 201 share a cathode drive, the first electrodes 201 of the lasers 300 are all connected to the same cathode pad, and further connected to the same cathode drive circuit through the cathode pad; the second electrodes 202 of at least two lasers 300 are connected, two or more lasers 300 connected with the second electrodes 202 share anode drive, the second electrodes 202 of the lasers 300 are all connected to the same anode bonding pad, and then are connected to the same anode drive circuit through the anode bonding pad, the first electrodes 201 and the second electrodes 202 of any two lasers 300 are not connected at the same time, and therefore the cathode drive circuit and the anode drive circuit can be used for being matched to gate any one laser 300.

In this embodiment, the second electrode 202 is disposed on the surface of the isolation material 130, and connects the second contact layers 120 of at least two lasers 300.

In this embodiment, the light emitting direction of the laser 300 is the same as the preset direction, and light emitting holes are formed in the second contact layer 120 and the second electrode 202, so that light can be emitted normally.

The second electrode 202 may be made of a non-light-transmissive material. Specifically, the second electrode 202 is an interconnection metal layer. The interconnection metal layer can be a metal material such as copper, aluminum and the like.

Specifically, in this embodiment, a second electrode 202 is formed on the surface of the isolation material 130, the second electrode 202 connects the second contact layers 120 of at least two lasers 300, and the first contact layer 110 between the lasers 300 connected by the second contact layers 120 is isolated.

In this embodiment, the laser array is divided into: m1 groups of lasers 300, each group comprising N1 lasers 300, the first electrodes 201 of said N1 lasers 300 being connected, wherein the product of M1 and N1 is the total number of said lasers 300; and/or the laser array is divided into: and M2 groups of lasers 300, each group including N2 lasers 300, the second electrodes 202 of the N2 lasers 300 being connected, wherein the product of M2 and N2 is the total number of the lasers 300, and N2 is equal to or less than M1.

It should be noted that, in this embodiment, the light emitting direction of the laser 300 is the same as the preset direction.

In other embodiments, the light emitting direction of the laser may also be opposite to the preset direction Y1.

That is, the laser is a backside illumination (BSI) laser, thereby improving the application flexibility of the embodiment of the present invention. Correspondingly, the embodiment of the invention can also reduce the number of the driving circuits of the back-side light-emitting laser, thereby being beneficial to reducing the number of routing bonding pads of the laser array and the area occupied by the routing area and reducing the packaging cost.

In particular, the laser is a back-side emitting laser, and the substrate may further have a micro lens structure (micro lens) on a side facing away from the active region for converging light formed by the light emitting stack.

Correspondingly, in the light-emitting laminated layer, the first reflector is an exit mirror, and light exits from one side of the first reflector; the second reflector is a total reflector. In this embodiment, the second contact layer and the second electrode do not need to be provided with light holes.

In this embodiment, in order to reduce light absorption by the substrate, the substrate may be thinned during the fabrication of the laser array.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected by one skilled in the art without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

1. A laser array comprising a plurality of lasers disposed on a semi-insulating substrate, each laser comprising at least one light emitting cell;

the light emitting unit includes: a first contact layer, a light emitting stack and a second contact layer provided in this order on a substrate,

wherein the first contact layer between the at least two lasers is isolated;

each laser comprises a first electrode and a second electrode, wherein the first electrodes of at least two lasers are connected, the second electrodes of at least two lasers are connected, and the first electrodes and the second electrodes of any two lasers are not connected at the same time.

2. The laser array of claim 1, wherein the light emitting stack comprises a first mirror, an active region, and a second mirror arranged in sequence along a predetermined direction;

the first electrode is positioned on one side, facing the active region, of the first contact layer and connects the first contact layers of at least two lasers;

the second electrode is positioned on one side of the second contact layer, which is far away from the active region, and the second contact layers of the at least two lasers are connected.

3. The laser array of claim 1, wherein the first electrodes are disposed around the first mirrors of the light emitting cells, and the first contact layers between the lasers to which the first electrodes are not connected are isolated from each other.

4. The laser array of claim 1, wherein the light emitting cells are filled with an isolation material therebetween, the isolation material between the lasers with the first electrodes unconnected being in contact with the substrate.

5. The laser array of claim 4, wherein the second electrode is disposed on the surface of the spacer material connecting the second contact layers of at least two lasers.

6. The laser array of claim 1, wherein each laser comprises a plurality of light emitting cells, the second contact layers of the plurality of light emitting cells being connected by a second electrode.

7. The laser array of claim 2, wherein the light emitting direction of the laser is the same as the predetermined direction, and the second contact layer and the second electrode have light emitting holes formed therein.

8. The laser array of claim 2, wherein the light emitting direction of the lasers is opposite to the predetermined direction.

9. The laser array of claim 1, wherein the laser array is divided into: the laser device comprises M1 groups of lasers, wherein each group comprises N1 lasers, first electrodes of the N1 lasers are connected, and the product of M1 and N1 is the total number of the lasers; and/or the presence of a gas in the atmosphere,

and M2 groups of lasers, wherein each group comprises N2 lasers, and second electrodes of the N2 lasers are connected, wherein the product of M2 and N2 is the total number of the lasers, and N2 is not less than M1.

10. The laser array of claim 9, wherein the values of M1, N1 minimize the sum of M1 and N1.

11. The laser array of claim 9, wherein the values of M2 and N2 minimize the sum of M2 and N2.

12. The laser array of claim 2, wherein the lasers are vertical cavity surface emitting lasers and the first and second mirrors are distributed bragg reflectors.

13. The laser array of claim 8, wherein the lasers are back-emitting lasers and the substrate has a microlens structure on a side facing away from the active region.

14. A light source module comprising a laser array and a driving board, wherein the laser array is the laser array as claimed in any one of claims 1 to 13;

the drive plate includes: a first decoder and a second decoder;

the first driving circuit is connected with the first decoder and used for providing a first driving signal to the first electrode based on an output signal of the first decoder;

the second driving circuit is connected with the second decoder and used for providing a second driving signal to the second electrode based on the output signal of the second decoder;

one or more lasers operate based on a first drive signal and a second drive signal.

15. The light source module as claimed in claim 14, wherein the laser array is divided into: the laser device comprises M1 groups of lasers, wherein each group comprises N1 lasers, first electrodes of the N1 lasers are connected, and the product of M1 and N1 is the total number of the lasers;

the number of the first driving circuits is M1, and the M1 first driving circuits are respectively connected with the first electrodes of the M1 groups of lasers;

and/or the presence of a gas in the atmosphere,

the laser array is divided into: m2 groups of lasers, wherein each group comprises N2 lasers, and second electrodes of the N2 lasers are connected, wherein the product of M2 and N2 is the total number of the lasers, and N2 is not less than M1;

the number of the second driving circuits is M2, and the M2 second driving circuits are respectively connected with the second electrodes of the M2 groups of lasers.

16. A lidar, comprising: the device comprises a transmitting module and a receiving module;

the emitting module comprises the light source module set of any one of claims 14 to 15, and is used for emitting a probe light beam;

the receiving module comprises one or more photoelectric detectors and is used for receiving the echo light beams reflected by the target object and converting the echo light beams into electric signals.

17. The lidar of claim 16, wherein a plurality of the lasers are arranged in a matrix array or a staggered array.

18. A method of forming a laser array, comprising:

providing a substrate, wherein the substrate is a semi-insulating substrate;

forming a first contact layer on the substrate;

forming a light-emitting laminated layer on the first contact layer, wherein the light-emitting laminated layer comprises a first reflector, an active region and a second reflector which are sequentially formed from bottom to top;

etching the light-emitting laminated layer to form a plurality of lasers;

and etching the first contact layer between at least two lasers to form a groove for exposing the substrate, so that the first contact layers of the two lasers are isolated.

19. The method of forming a laser array of claim 18, further comprising: after forming a plurality of lasers, forming a first electrode on the surface of the first contact layer, which faces away from the substrate, wherein the first electrodes of at least two lasers are connected.

20. The method of forming a laser array of claim 18, further comprising: forming a second contact layer on the second mirror;

and after the groove is formed, forming a second electrode on the surface of the second contact layer, wherein the second electrode is used for connecting the second contact layers of at least two lasers, and the first contact layers between the lasers connected by the second contact layers are isolated.

21. The method of claim 20, wherein etching the light emitting stack to form a plurality of lasers comprises: etching the light-emitting laminated layer to form a plurality of light-emitting units; the laser comprises at least one light emitting unit;

the method for forming the laser array further comprises the following steps: filling an isolation material between the light emitting cells; and forming a second electrode on the surface of the isolation material, wherein the second electrode is used for connecting the second contact layers of at least two lasers, and the first contact layers between the lasers connected by the second contact layers are isolated.