CN112490846A

CN112490846A - Semiconductor laser transmitter

Info

Publication number: CN112490846A
Application number: CN202011361135.2A
Authority: CN
Inventors: 雷述宇
Original assignee: Ningbo Abax Sensing Electronic Technology Co Ltd
Current assignee: Ningbo Abax Sensing Electronic Technology Co Ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-03-12

Abstract

The present invention provides a semiconductor laser transmitter, which is characterized by comprising: a first DBR layer, a second DBR layer, a quantum well active region disposed between the first DBR layer and the second DBR layer, The second DBR layer is also connected to a substrate layer, the substrate layer has a first thickness, and a side of the substrate away from the quantum well active region includes a first electrode and a first electrode that excite the quantum well active region. Two electrodes; by arranging the first electrode and the second electrode of the driving active area on the same side of the substrate, the lead inductance is reduced, so that the transmitter can adapt to the scene requiring higher electrical signal transfer rate, and there is no need to change the top The way to emit light.

Description

Semiconductor laser transmitter

Technical Field

The present invention relates to the field of semiconductor laser emitters, and in particular to a VCSEL-type laser structure.

Background

Semiconductor type lasers, which are very advantageous for the whole system because of their excellent controllability and easy realization of array type integrated design, are increasingly utilized to facilitate adjustment of laser parameters by controlling characteristics such as voltage during each probing process, and are also called semiconductor Laser Diodes (LDs), which are lasers developed in the 20 th century and the 60 th era. There are dozens of working substances of semiconductor laser, such as gallium arsenide (GaAs), cadmium sulfide (CdS), etc., and the excitation modes mainly include an electric injection type, an optical pump type, and a high-energy electron beam excitation type. The advantages of semiconductor lasers mainly include the following aspects: 1) small volume and light weight. 2) The stimuli can be injected: it can be driven with only a few volts injected into a current in the milliamp range. No other excitation devices and components than the power supply device are required. The electric power is directly converted into optical power, and the energy efficiency is high. 3) The wavelength range is wide: by appropriate selection of materials and alloy ratios, lasers of any wavelength can be realized over a wide range of wavelengths, both infrared and visible. 4) Can directly modulate: the oscillation intensity, frequency and phase can be modulated in the range of dc to ghz by superimposing the signal on the drive current. 5) The coherence is high: output light with high spatial coherence can be obtained with a single transverse mode laser. In Distributed Feedback (DFB) and Distributed Bragg Reflector (DBR) lasers, stable single longitudinal mode lasing, high temporal coherence, and the like are advantageous.

At present, a semiconductor laser which is more applied is a Surface Emitting semiconductor laser, and has many advantages compared with a traditional edge Emitting reported laser, and a Vertical-Cavity Surface Emitting laser (VCSEL) in the Surface Emitting semiconductor laser has the advantages of high side mode rejection ratio, low threshold, small volume, easy integration, high output power and the like due to low threshold, circular light beam, easy coupling and easy two-dimensional integration, and becomes a hotspot of research in the photoelectron field. Such as structured light sources for 3D imaging, laser detection and ranging (LADAR), time of flight (TOF)3D imaging, aviation defense and fusion studies, etc. Vertical Cavity Surface Emitting Lasers (VCSELs) are commonly used in many semiconductor laser applications due to low power applications as well as high frequency advantages and manufacturing advantages over other types of semiconductor laser devices, where it is desirable to ensure that the VCSEL laser source has a reliable laser output during TOF ranging, however, currently employed packaging schemes are employed where the VCSEL device is front-mounted on a packaged substrate by solder or epoxy. Then, a VCSEL device can be connected to an external circuit by using wire bonding, so that parasitic inductance exists between leads of the VCSEL device, for example, 1nH parasitic inductance exists between 1mm leads, therefore, the semiconductor laser with the existing structure also needs leads, the number of leads needed by the structure is large, and a series of problems caused by the effects of parasitic inductance and the like exist, for example, when high-speed electric signal transmission requirements need to be transmitted, the problem is very important for the VCSEL type semiconductor laser to be increasingly used in high-precision TOF scheme measurement, and at the moment, the VCSEL needs to respond accurately at a high speed.

Therefore, it is an urgent need to develop a VCSEL-type semiconductor transmitter that can eliminate the parasitic inductance generated by the lead wires in the prior art and further ensure the high electrical signal transmission requirement of the TOF-type ranging system.

Disclosure of Invention

The present invention is directed to provide a semiconductor laser transmitter, which solves some problems caused by parasitic inductance due to a lead-out wire in the related art due to high-speed electrical signal transmission requirements corresponding to the accuracy of a TOF type detection system, and the like, and even seriously causes the application of a VCSEL type semiconductor laser in the TOF field to be greatly limited.

In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:

the embodiment of the invention provides a semiconductor laser transmitter, which is characterized by comprising: the quantum well active region between the first DBR layer and the second DBR layer is disposed to first DBR layer, the second DBR layer still connects the substrate layer, the substrate layer has first thickness, one side that the substrate kept away from the quantum well active region contains the first electrode and the second electrode of arousing the quantum well active region.

Optionally, the first DBR layer is doped P-type, the second DBR layer is doped N-type, the first electrode is connected to the first DBR layer, and the second electrode is connected to the second DBR layer.

Optionally, the first electrode includes a conductive connection portion penetrating through the substrate, and is connected to the first DBR layer through the conductive connection portion.

Optionally, the conductive connection portion includes a conductive connection portion located at a substrate through portion formed by a TSV process.

Optionally, the semiconductor active region and the penetrating portion are disposed on the semiconductor substrate in an inserting manner.

Optionally, the through part is arranged in a separate area outside the semiconductor active area on the semiconductor substrate.

Optionally, an insulating medium portion is further included between the penetrating portion and the conductive connecting portion.

Optionally, the through part is formed by two times of etching in two directions.

Optionally, the penetrating part has an inclined part within a first inclination angle range.

Optionally, the first inclination angle is in the range of 75 ° to 90 °.

The invention has the beneficial effects that: the invention provides a semiconductor laser transmitter, which is characterized by comprising: the first DBR layer, the second DBR layer, dispose in first DBR layer with the quantum well active area between the second DBR layer, the second DBR layer still connects the substrate layer, the substrate layer has first thickness, one side that the substrate kept away from the quantum well active area contains the excitation the first electrode and the second electrode of quantum well active area, through so design on the one hand will drive active area and trigger photoelectric conversion's first electrode and second electrode and set up in the same one side of substrate, realized the reduction of lead wire quantity in the follow-up encapsulation, can satisfy the high-speed signal transmission demand through TSV fenestrate adaptation design, guaranteed to use the reliability of this type of VCSEL system.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic diagram of a package structure of a VCSEL laser source and a driving and detecting array provided in the prior art;

fig. 2 is a front view of a VCSEL laser source according to an embodiment of the present invention;

FIG. 3 is a front view of another VCSEL laser source according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a VCSEL laser source according to another embodiment of the present invention;

fig. 5 is a schematic diagram of an active transmitting unit and a perforation insertion arrangement according to an embodiment of the present invention;

fig. 6 is a schematic diagram of another arrangement of an active emission region and a perforation independently provided by an embodiment of the present invention;

fig. 7 is a schematic view of a package of a light emitting module and a substrate according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.

FIG. 1 is a schematic diagram of a prior art package structure of a VCSEL laser source and a driving and detecting array; after the VCSEL chip is attached to the submount, the positive and negative electrodes are led out by wire bonding, and the package of the whole module is completed by matching with a laser Driver and a Sensor chip, wherein the VCSEL laser source 101 is located at a position above the Driver 103, one electrode of the VCSEL laser source 101 is connected with a plane of a connecting plate between the Driver 103 and the VCSEL laser source, because of the characteristics of the laser, the other electrode needs to be led out and connected by using a lead wire 102 and connected with the other electrode output by the Driver 103, in addition, the connection of the Driver 103 also needs a lead wire 104, and similarly, a Sensor (usually, an array type photosensitive part) 107 also needs a lead wire 106 to be connected with a package substrate 105, and in the existing package connection structure, the following disadvantages exist: a) lead inductance of 1mm 1nH is inevitable when the VCSEL leads come out. b) The driving chip Driver signal is sent to the VCSEL through the flexible board, the passing path is long, and the design for eliminating the inductance must be made on the flexible board. c) The placement of the VCSEL on the Driver upper surface of the Driver chip presents a great challenge to the heat dissipation design of the VCSEL, resulting in the VCSEL not being able to operate for a long time because heat cannot be dissipated.

In order to reduce the lead structure, there are various solutions in the prior art, wherein a typical one is to arrange a first electrode and a second electrode on the edge of a substrate close to an active area, then coat an adhesive layer on the other end of the active area, adhere the second substrate layer through the adhesive layer, and then remove the original substrate layer through reverse removal, so that the strength of the device can be ensured, and two different electrodes are also designed on the same side, the light emitting direction is not changed, and the device still adopts a light ejecting mode, but such design has the second substrate layer added in the light emitting direction and the adhesive layer added at the same time, so that although the connection is simplified, actually more process steps are introduced in the manufacturing process, and the substrate removing process is not complicated, but the cost is greatly increased for precision machining, and since the emitted light needs to pass through the adhesive layer and the second substrate, the light loss will be produced, this scheme is in fact equivalent to the light loss of back light-emitting mode, light loss will far exceed back light-emitting scheme even under the improper prerequisite of tie coat control, in order to improve light loss back light, there is the improvement scheme to propose offering the hole of corresponding quantity in the position of the substrate direction cooperation light-emitting of light-emitting, in order to guarantee the unaffected scheme of emergent light, but these schemes themselves still have higher complexity on technology, manufacturing cost also does not have essential reduction, consequently guarantee that the production process is extravagant little and keep current top light-emitting scheme in order to improve this phenomenon, need design a novel structure.

Fig. 2 is a front view of a VCSEL laser source according to an embodiment of the present invention; the present invention is optimized for the structure of VCSEL laser source, wherein 202a and 202b are the first electrode and the second electrode of the laser source, wherein the electrode material can be (Au), germanium (Ge), silver (Ag), palladium (Pd), platinum (Pt), nickel (Ni), titanium (Ti), vanadium (V), tungsten (W), chromium (Cr), aluminum (Al), copper (Cu), zinc (Zn), tin (Sn) and indium (In), and the like, but is not limited to metal material, and can also be a transparent electrode formed by metal oxide, and the first electrode is connected to the first DBR layer (i.e. P-type Bragg reflector Reflection of 209 In the figure), and has a laminated structure In which low refractive index layer and high refractive index layer are alternately stacked. The low refractive index layer being, for example, lightP-type Al with chemical film thickness of lambda/4 (or (2k +1) × lambda/4)_X1Ga_(1-X1)As (0 < X1 < 1). λ represents the oscillation wavelength of the semiconductor laser 1. The high refractive index layer is P-type Al with optical thickness of lambda/4 (or (2k +1) × lambda/4)_X2Ga_(1-X2)As (0. ltoreq. X2 < X1), which is only exemplified here, and is not a specific limitation As to the material of implementation, it is sufficient that the Bragg structure is arranged so that the medium and low refractive indexes and the high refractive index are alternately stacked. The second electrode 202b is connected to the second DBR layer, i.e., 211 in the drawing, which has a stacked structure in which low refractive index layers and high refractive index layers are alternately stacked. The low refractive index layer is N-type Al with an optical film thickness of lambda/4 (or (2k +1) × lambda/4)_X3Ga_(1-X3)As (0 < X3 < 1). The high refractive index layer is N-type Al with optical thickness of lambda/4 (or (2k +1) × lambda/4)_X4Ga_(1-X4)As (0. ltoreq. X4 < X3), which is also exemplified herein, and not particularly limited to implementation materials for which a Bragg structure satisfying an alternate stacking of medium and low refractive indexes and a high refractive index is provided, the active region 210 has a quantum well structure in which undoped Al having a thickness of 8nm is alternately stacked_0.11As_0.89Quantum well layer of GaAs quantum well layer and undoped Al having thickness of 5nm_0.3Ga_0.7A barrier layer of an As layer. For example, the active region 210 is designed to have a 780nm wavelength light emission (practically not limited to this wavelength, infrared light in the wavelength range of 800nm-1000nm is more commonly used in TOF systems) in accordance with an optical thickness of the active region 210 being an integer multiple of the wavelength of 1/2 laser light to satisfy the resonance condition. From undoped Al_0.6Ga_0.4The isolation layer formed of the As layer As a layer for forming the active region 210 includes a quantum well structure at the center thereof, although specific material and thickness relationships are not limited thereto and are merely exemplary illustrations herein. The whole isolation layer has the same film thickness as lambda/n_rIs as large as an integer multiple of where λ is the oscillation wavelength and n is_rIs a refractive index of a medium, and a voltage is applied through the first electrode 202a and the second electrode 202b to realize light emission of the diode, it should be noted that the structure in which the light emitting portion in the VCSEL type semiconductor laser transmitter includes the first and second DBR layers and the active region is generally in the longitudinal directionThe dimensions of the locations are relatively small, for example the total thickness may be around 10 μm, but the reliability of the emitter at such dimensions will be subject to severe examination, and therefore a substrate is generally provided on the opposite side of the light-emitting direction, which has a first thickness, which is mainly to ensure the reliability of the whole device, so that the first thickness of the substrate is designed according to the theory of strength, for example a semiconductor substrate layer of not less than 100 μm, the invention forms a Through-hole with a specific aspect ratio, for example in the case of an aspect ratio of 5:1 to 40:1 or even higher, by forming a Through-hole structure on the substrate, optimally by using a TSV process (Through Silicon Via), i.e. a Through Silicon Via process, so as to form a Through-hole with a specific aspect ratio, for example in the case of an aspect ratio of 5:1 to 40:1 or even higher, and thereafter providing a dielectric layer, for example an insulating material, on the sidewalls of the Through, in order to ensure the connection reliability and even lead out the heat generated by the device through the conductive connecting part in the through hole, the conductive connecting part in the through hole can be set to be completely filled metal, for example, the filling material which is completely the same as the material of the first electrode, and is connected with the first electrode, and the first electrode and the second electrode can be both arranged on one side of the substrate far away from the light-emitting direction of the emitting part through the through hole, so that the more optimized packaging connection can be realized, the connection of leads is omitted, and the high-speed transmission of electric signals is realized to the maximum extent.

Fig. 3 is a front view of another VCSEL laser source structure according to an embodiment of the present invention, which is different from the above-mentioned solution in that the perforation solution is a perforation formed by two times of forming in two opposite directions, a non-through hole with a depth of 40-70 μm can be formed from one side of the substrate away from the emitting end, and then a hole with a remaining proportion is formed from the opposite side, so as to implement a through design, and the connected metal is not fully filled, in an actual use process, an insulating medium layer is included between a hole wall in the through hole and the conductive connection portion, and a resistance reduction portion is further included, the metal material of the portion is significantly greater than that of other portions (that is, the conductive filling portion includes a special-shaped cross-section portion), in order to ensure reliability of the device, other medium materials are filled in a remaining space of the through hole, and may also be the same material as the insulating medium, of course, other dielectric materials can be used as the filling material, and the two-step molding scheme overcomes some possible defects of the through hole with a large aspect ratio formed in one step, which is more beneficial for the implementation of the present invention, the implementation manner of the conductive connection portion in fig. 3 can be different from that in fig. 2, the conductive connection portion in fig. 2 can be formed by heat melting and in a deposition manner, and the metal in fig. 3 can be formed by deposition, which is of course not described in detail here with the same components as before, and the use of similar parts is also similar.

Fig. 4 is a front view of a VCSEL laser source according to another embodiment of the present invention, which is different from the above-mentioned manner in that the two-step formed through-hole has a sidewall that is not vertical and has a certain included angle with the horizontal direction, and in order to ensure the efficiency of forming and processing and optimally ensure the uniformity of the formed conductive connection portion, the sidewall is optimally set to have an angle range of 75 ° to 90 °, and both sides of the sidewall are provided with inclined portions within the included angle range, although the inclined portions having the included angle range may also be provided at the one-step formed through-hole, and will not be described herein again.

Fig. 5 is a schematic diagram of the VCSEL laser source light emitting portion and the penetrating portions arranged in an inserting manner according to an embodiment of the present invention, and by such arrangement, each penetrating portion can only correspond to a plurality of emitting portions, that is, the first electrode is connected to a plurality of active regions through the electrical connection portions in the penetrating holes, so that a more accurate light emitting control effect can be achieved, and in addition, the inserting design can also ensure the distance of the conductive connection portions in each penetrating portion, so that the interference effect of the conductive connection portions in the penetrating portions can be optimized, the rule of the inserting arrangement can be obtained by using optimized computer program simulation calculation, and the rest of the inserting arrangement is not described in detail.

Fig. 6 is a schematic diagram of an independent arrangement of light emitting portions and penetrating portions of a VCSEL laser source according to an embodiment of the present invention, in which more active regions can be connected to, for example, tens of active regions through a conductive connecting portion of a penetrating portion to control laser light emitted from the active regions, and all penetrating portions are disposed in separate regions, so that the arrangement can ensure that the density of emitted light can achieve coverage with higher resolution in a field of view, and simultaneously, the number of required penetrating portions is reduced as much as the number of active regions driven by the same conductive connecting portion, so that interference between the conductive connecting portions can be reduced as much as possible, and the requirement for high-speed signal transmission in a TOF system is also facilitated, thereby ensuring accuracy of distance measurement.

Fig. 7 is a schematic structural diagram illustrating a VCSEL laser source and a package substrate according to an embodiment of the present invention; through the design of the VCSEL laser source structure shown in fig. 5 or fig. 6, the planar design of the first electrode and the second electrode provides a basis for planar connection with the substrate 705, and the first electrode of the VCSEL laser source is directly connected with the second electrode and the corresponding electrode of the packaging substrate in a welding manner, so that direct planar connection is realized, and therefore, no external lead is adopted for the two electrodes, so that the parasitic inductance is reduced or eliminated, and it is very important for TOF ranging to obtain a high-precision measurement result, and on the other hand, the connection reliability is also realized through the structure.

The technical scheme of the invention realizes the following technical advantages:

1. parasitic parameters brought by the lead process can be reduced.

2. And the signal crosstalk generated by the inductance effect of a large high-speed driving current signal through a lead wire is reduced.

3. The steps of reducing the lead wires are completely free of movable parts, and reliability is improved.

4. The technical effect of using the VCSEL light source for high-speed response of high-precision TOF measurement system design is achieved.

5. The rule of the arrangement of the conductive metal connecting parts is optimized, the adaptation to different scenes is realized, and the interference phenomenon among the conductive connecting parts is also reduced.

It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A semiconductor laser transmitter, comprising: a first DBR layer, a second DBR layer, a quantum well active region disposed between the first DBR layer and the second DBR layer, The second DBR layer is also connected to a substrate layer, the substrate layer has a first thickness, and a side of the substrate away from the quantum well active region includes a first electrode and a second electrode that excite the quantum well active region electrode.

2 . The semiconductor laser transmitter according to claim 1 , wherein the first DBR layer is P-type doped, the second DBR layer is N-type doped, and the first electrode and the The first DBR layer is connected, and the second electrode is connected to the second DBR layer.

3 . The semiconductor laser transmitter according to claim 1 , wherein the first electrode comprises a conductive connection part penetrating the substrate, and is connected to the first DBR layer through the conductive connection part. 4 . connect.

4 . The semiconductor laser transmitter of claim 1 , wherein the conductive connection portion comprises a conductive connection portion located in a through-substrate portion formed by a TSV process. 5 .

5 . The semiconductor laser transmitter according to claim 4 , wherein the semiconductor active region and the through portion are interspersed and arranged on the semiconductor substrate. 6 .

6 . The semiconductor laser transmitter according to claim 4 , wherein the penetration portion is arranged in an independent region outside the semiconductor active region on the semiconductor substrate. 7 .

7 . The semiconductor laser transmitter according to claim 4 , wherein an insulating medium portion is further included between the penetration portion and the conductive connection portion. 8 .

8 . The semiconductor laser transmitter of claim 4 , wherein the penetration portion is formed by two etchings in two directions. 9 .

9 . The semiconductor laser transmitter according to claim 4 , wherein the penetration portion has an inclined portion within a first inclination angle range. 10 .

10 . The semiconductor laser transmitter according to claim 9 , wherein the first tilt angle ranges from 75° to 90°. 11 .