CN214673448U - Optical communication O-waveband silicon-based high-speed semiconductor laser chip - Google Patents

Abstract

The utility model provides an optical communication O wave band silicon-based high-speed semiconductor laser chip, which adopts different buffer layers to form a growth surface of InP material with low dislocation density; N-InAlGaAs is adopted to replace a conventional N-InAlAs electron barrier layer on the energy band structure, so that the potential barrier of electrons entering a quantum well from an N type is reduced, and the threshold value is reduced; a superlattice structure quantum barrier is adopted to replace a single barrier layer structure so as to improve the transport of heavy holes in a quantum well; and the material structure is adjusted, so that the O-band high-direct-modulation-rate semiconductor laser chip with good reliability for silicon substrate optical communication is realized.

Description

Optical communication O-waveband silicon-based high-speed semiconductor laser chip

Technical Field

The utility model relates to a laser chip technical field especially relates to a silica-based high-speed semiconductor laser chip of optical communication O wave band.

Background

The high-speed optical chip is a key light-emitting chip of a large-capacity data center, a 5G network and a large-capacity access network. Compared with the conventional InP substrate, the silicon substrate has the advantages of good electric and thermal conductivity, low cost, good hardness, compatibility with the conventional semiconductor process and the like, and the preparation of the InP laser chip on the silicon substrate is the key of the next development and integration of optical communication; in general, an InP material system cannot be directly grown on a silicon substrate due to mismatch of lattice constants and the like.

In addition, the strain quantum well adopts compressive strain to convert the highest hole band into a similar light hole band, so that the Auger coincidence and the inter-valence band absorption rate are greatly reduced, and the effective mass and the state density of holes can be effectively reduced by the compressive strain, so that the gain and the relaxation frequency of the laser are improved; in 1990, researchers have found that the laser threshold can be further lowered with tensile strained quantum wells compared to compressive strain, resulting in higher optical power and relaxation frequency (Tanban-EK T et al. Performance enhancement of InGaAs/InP quaternary well lasers by bone tension and relaxation frequency.21 st internal. semiconductor. laser Conf.1990; D-3). In order to further reduce the threshold current and the working current of the laser chip, a tensile strain quantum well can be adopted, however, in order to improve the interaction density of photons and electrons of the laser and the modulation frequency of the high-speed laser chip, a larger number of layers of quantum wells are generally adopted; because the effective mass of electrons is small, the P-type electron blocking layer is generally adopted to limit the electrons on a conduction band, but the effective mass of holes is large, the problem of uneven distribution is easily caused in a multilayer quantum well, and generally, the transport of carriers on the energy band mainly has two types: one is by thermal transition across the barrier and the other is the tunneling effect of the carriers, and quantum barriers generally do not allow a large proportion of tunneling for heavy holes.

In addition, because the density of photons and electrons at the position of the dissociated cavity surface is relatively concentrated, the semiconductor laser is easy to generate heat to form cavity surface catastrophic failure, and is a common factor for failure in the application process of the laser.

SUMMERY OF THE UTILITY MODEL

In order to overcome the defects existing in the prior art, the utility model provides a silica-based high-speed semiconductor laser chip of optical communication O wave band. Transition materials with similar lattice parameters are adopted on a silicon substrate, and the grown interface is baked and cleaned to improve the growth interface of an InP material system and reduce dislocation. In addition, the thin layers of the multi-layer superlattice are used as quantum barriers, so that tunneling of holes among different wells is facilitated, and uniformity and differential gain of hole injection are improved. The PNP current blocking layer can block current from flowing to the end face by growing the PNP current blocking layer in the area near the light-emitting and backlight end face; on the other hand, the PNP combined waveguide can adjust the near field of light spots by adjusting the thickness, reduce the end face photon density of the laser and improve the reliability of a chip. Under the P-face electrode metal, the Fe-doped insulating InP layer is adopted to effectively improve the capacitance parameter of the chip and improve the bandwidth, and the conventional processes such as BCB and the like can be omitted.

The InP material low-dislocation-density growth surface is formed by adopting different buffer layers; N-InAlGaAs is adopted to replace a conventional N-InAlAs electron barrier layer on the energy band structure, so that the potential barrier of electrons entering a quantum well from an N type is reduced, and the threshold value is reduced; a superlattice structure quantum barrier is adopted to replace a single barrier layer structure so as to improve the transport of heavy holes in a quantum well; and the material structure is adjusted, so that the O-band high-direct-modulation-rate semiconductor laser chip with good reliability for silicon substrate optical communication is realized.

The utility model discloses specifically adopt following technical scheme:

an optical communication O wave band silicon-based high-speed semiconductor laser chip is characterized in that: on a Si substrate, adopting different buffer layers to form a low dislocation density growth surface; the material structure adopts N-InAlGaAs to replace the N-InAlAs electron barrier layer and adopts a superlattice quantum barrier structure.

Further, the buffer layer includes: an N-GaP buffer layer, an N-GaAs buffer layer, and an N-InP buffer layer.

And, a optical communication O wave band silicon-based high-speed semiconductor laser chip, characterized by: the epitaxial layer comprises the following components which are sequentially formed on a Si substrate: the device comprises an N-GaP buffer layer, an N-GaAs buffer layer, an N-InP buffer layer, an N-InAlGaAs transition layer, an InAlGaAs lower waveguide layer, an InAlGaAs lower respectively limiting layer, an InGaAlAs strain multi-quantum well and barrier, an InAlGaAs upper respectively limiting layer, a P-InAlAs electron blocking layer, a P-InP spacing layer, a P-InGaAsP grating layer, a P-InP grating cover layer, a P-InGaAsP corrosion stop layer, a P-InP space layer, a P-InGaAsP transition layer, a P-InGaAs electric contact layer and an insulating InP layer doped with Fe.

Furthermore, the front and back light-emitting end faces of the chip are dissociated in a regrowth area, and the regrowth area is filled with a P-InP layer, an N-InGaAsP layer and a P-InP layer which are formed by regrowth.

Further, a ridge waveguide formed by etching on the epitaxial layer is also included.

Further, the ridge waveguide is etched to a P-InGaAsP etch stop layer.

Further, in the InGaAlAs strained multi-quantum well and barrier, the barrier layer is composed of a superlattice structure of 3 layers of 2nm InGaAlAs barriers and 2 layers of 2nm InGaAlAs wells.

The utility model discloses and preferred scheme at the substrate of silicon, grow the GaP buffer layer earlier at first through MOCVD and grow GaAs and InP buffer layer in proper order after that, realize that the material surface of low defect does benefit to the epitaxial growth of follow-up laser structure.

On the epitaxial structure, N-AlGaInAs is adopted to replace the conventional N-InAlAs to reduce the height of a potential barrier, thereby being beneficial to improving the transport reduction threshold of electrons; and then, the working threshold and the bandwidth of the chip are improved by adopting a tensile strained multi-quantum well, and the quantum barrier adopts a thin superlattice structure, so that the heavy hole is favorably transported among different quantum wells, and the distribution uniformity of the heavy hole is improved.

The PNP structure layer is grown in the area close to the light-emitting end face and the backlight end face, the reverse PN junction characteristic of PNP plays a role in limiting electrons, carrier flow is prevented from generating heat to the end face and photon action, and COMD (cavity surface catastrophic failure) occurs. The InP/InGaAsP/InP has the function of combining waveguides for an optical field and is coupled with light of an active region, the near-field distribution of laser is adjusted, near-field light spots are improved, the end face photon density is reduced, the interaction between end face electrons and photons is improved, the divergence angle is reduced, and the end face catastrophe failure of a chip is improved.

In addition, the Fe-doped insulating InP layer grown on the epitaxial structure can play a role in electrical isolation to reduce capacitance and improve bandwidth, so that conventional processes such as BCB/PI glue and the like are not needed, the capacitance parameter of the chip is improved, and the working bandwidth is improved; the utility model discloses can realize the high-speed semiconductor laser chip of optical communication O wave band based on silicon substrate.

Drawings

The invention will be described in further detail with reference to the following drawings and detailed description:

fig. 1 is a schematic view of an epitaxial structure of a high-speed laser chip according to an embodiment of the present invention;

in the figure: 1 is an N-Si substrate, 2 is an N-GaP buffer layer, 3 is an N-GaAs buffer layer, 4 is an N-InP buffer layer, 5 is an N-InGaAlAs transition layer, 6 is an InGaAlAs lower waveguide layer, 7 is an InGaAlAs lower respectively limiting layer, 8 is an InGaAlAs strain multiple quantum well and barrier, 9 is an InGaAlAs upper respectively limiting layer, 10 is a P-InAlAs layer, 11 is a P-InP spacer layer, 12 is a P-InGaAsP grating layer, 13 is a P-InP grating cover layer, 14 is a P-InGaAsP corrosion stop layer, 15 is a P-InP space layer, 16 is a P-InGaAsP transition layer, 17 is a P-InGaAsP electric contact layer, 18 is an Fe-doped insulating InP layer, the left and right end faces in the figure are the dissociation of a laser, and 19, 20 and 21 are respectively a P-InP layer, an N-InP layer and a P-InP layer which are regrown in a selected region.

Fig. 2 is a schematic diagram of the structure of quantum well and barrier energy band of conduction band in the embodiment of the present invention;

in the figure, the barrier layer is composed of 3 layers of 2nm InGaAlAs barriers and 2 layers of 2nm InGaAlAs trap superlattice structures, and the function of improving the transportation of heavy holes between quantum traps is achieved.

Detailed Description

In order to make the features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail as follows:

as shown in fig. 1, the specific structure of the epitaxial layer of the optical communication O-band silicon-based high-speed semiconductor laser chip and the manufacturing process of the chip provided in this embodiment are as follows:

1. firstly, placing a 2-inch N-Si substrate 1 into an MOCVD growth cavity, introducing nitrogen at high temperature for baking for 15min, wherein the baking effect of introducing carrier gas at high temperature mainly has two aspects, namely removing surface dirt particles on one hand, improving the growth surface quality of the material by utilizing the high-temperature quality transport effect on the other hand, improving the surface flatness, and then growing a 300nm N-GaP buffer layer 2; introducing phosphane at high temperature, baking for 15min, and growing a 300nm N-GaAs buffer layer 3 with a growth lattice constant similar to GaP; then, arsine is introduced into the mixture to be baked for 15min at high temperature, and the 500nm N-InP buffer layer 4 grows to finish the growth of the buffer layer.

2. Then growing a 15nm N-AlGaInAs transition layer 5, growing an undoped 30nm AlGaInAs lower waveguide layer 6, wherein the lower waveguide layer has low potential barrier and is beneficial to improving the transport of electrons; growing a limiting layer 7 under 20nm of undoped AlGaInAs respectively; then forming an InGaAlAs strain multiple quantum well and a barrier 8, wherein the InGaAlAs strain multiple quantum well and the barrier 8 comprise 7 layers of grown 8nm-AlGaInAs tensile strain quantum wells, the tensile strain is at least 1.3%, 8 layers of grown 10nm-AlGaInAs compressive strain quantum barriers, the compressive strain is at least 0.4%, each quantum barrier consists of 3 layers of 2nm-AlGaInAs barriers and 2 layers of 2nm-AlGaInAs well superlattice structures, as shown in figure 2, each quantum barrier is compressive strain, and the barrier layers adopt a multi-layer superlattice structure to improve hole transportation; compared with a compressive strain quantum well, the tensile strain has lower threshold value and higher gain and bandwidth characteristics, and meanwhile, the quantum barrier adopts a thin superlattice structure, so that heavy holes are more favorably transmitted among the quantum wells through a tunneling effect, and the uniformity of direct distribution of the heavy holes in different quantum wells is improved, thereby improving the differential gain and bandwidth saturation characteristics; growing a 15nm AlGaInAs upper limiting layer 9 and a 25nm P-InAlAs electronic barrier layer 10; and growing a 50nm P-InP layer 11, growing a 40nm P-InGaAsP grating layer 12 and preparing a uniform grating.

3. Followed by PECVD deposition of SiO₂And a dielectric layer is 200nm, areas which are 20 micrometers close to the front light-emitting end face and the rear light-emitting end face of the chip are removed through photoetching corrosion, and diluted bromine is adopted: carrying out isotropic etching on the hydrobromic acid solution until the etching depth reaches the N-InP buffer layer; and then growing 100nm P-InP 19, 50nm N-InGaAsP 20 and 100nm P-InP 21 in sequence, wherein the PNP combination layer plays a role of a reverse PN junction when current passes through so as to limit most of the current to be injected into the end face of the chip, cavity surface catastrophic failure (COMD) caused by large photon and electron density of the end face of the chip is improved, in addition, the PNP layer can be used as a waveguide layer optically, and the distribution of light spot near fields on the end face can be optimized by adjusting the thickness of the N-InGaAsP layer so as to improve the photon density of the end face and reduce the heat generation of the end face of the chip.

4. Removing SiO on the surface of the wafer after the PNP layer is grown₂And a dielectric layer, namely putting the wafer into an MOCVD cavity, heating, growing a 100nm P-InP grating cover layer 13, a 25nm P-InGaAsP corrosion stop layer 14, a 2.0 micron P-InP space layer 15, a 50nm P-InGaAsP transition layer 16, a 250nm P-InGaAs electric contact layer 17 and a 300nm Fe-doped insulating InP layer 18 at high temperature, and finishing the epitaxial growth of the material.

PECVD growth of 150nm SiO₂The dielectric layer is etched by photoetching to form a laser ridge waveguide, and the other areas on the wafer except the two sides of the ridge waveguide are etched completely; removing the surface dielectric layer, growing 4000nm SiO₂Opening a hole on the surface of the ridge waveguide in a conventional passivation layer, removing the Fe-doped insulating InP layer on the surface of the ridge waveguide, evaporating Ti/Pt/Au P-type electrode metal by using an electron beam, and enabling the P-type metal and the surface of the semiconductor material to pass through SiO₂The passivation layer and the Fe-doped insulating InP layer form electrical isolation to form a lower chip capacitor, processes such as BCB/PI glue and the like are not needed, and the characteristics of low capacitance and high bandwidth of the chip can be realized; then thinning the back mask of the chip to 200 microns, evaporatingThe N-side metal has no great influence on the series resistance due to the thicker thinning thickness because of the low material resistance characteristic of the silicon material; dissociating to form bars, using Al₂O₃And electron beam evaporation is carried out on the/Si film system to form a high-reflection and high-transmission film of the chip resonant cavity, so that the chip preparation is completed.

The method adopts silicon as a substrate, heat sink is not needed in the actual packaging process, and the high-speed laser chip can be widely used in the fields of silicon optical integration, hybrid integration, silicon optical data centers and the like.

The present invention is not limited to the best mode, and any person can obtain other optical communication O-band silicon-based high-speed semiconductor laser chips in various forms according to the teaching of the present invention.

Claims (7)

1. An optical communication O wave band silicon-based high-speed semiconductor laser chip is characterized in that: on a Si substrate, adopting different buffer layers to form a low dislocation density growth surface; N-InAlGaAs is adopted to replace the N-InAlAs electron barrier layer on the material structure, and a superlattice structure quantum barrier structure is adopted.

2. The optical communication O-band silicon-based high-speed semiconductor laser chip of claim 1, wherein: the buffer layer includes: an N-GaP buffer layer, an N-GaAs buffer layer, and an N-InP buffer layer.

3. An optical communication O wave band silicon-based high-speed semiconductor laser chip is characterized in that: the epitaxial layer comprises the following components which are sequentially formed on a Si substrate: the device comprises an N-GaP buffer layer, an N-GaAs buffer layer, an N-InP buffer layer, an N-InAlGaAs transition layer, an InAlGaAs lower waveguide layer, an InAlGaAs lower respectively limiting layer, an InGaAlAs strain multi-quantum well and barrier, an InAlGaAs upper respectively limiting layer, a P-InAlAs electron blocking layer, a P-InP spacing layer, a P-InGaAsP grating layer, a P-InP grating cover layer, a P-InGaAsP corrosion stop layer, a P-InP space layer, a P-InGaAsP transition layer, a P-InGaAs electric contact layer and an insulating InP layer doped with Fe.

4. The optical communication O-band silicon-based high-speed semiconductor laser chip of claim 3, wherein: the front and back light-emitting end faces of the chip are dissociated in a regrowth area, and the regrowth area is filled with a P-InP layer, an N-InGaAsP layer and a P-InP layer which are formed by regrowth.

5. The optical communication O-band silicon-based high-speed semiconductor laser chip of claim 4, wherein: and a ridge waveguide formed by etching on the epitaxial layer.

6. The optical communication O-band silicon-based high-speed semiconductor laser chip of claim 5, wherein: the ridge waveguide is etched to the P-InGaAsP etch stop layer.

7. The optical communication O-band silicon-based high-speed semiconductor laser chip of claim 3, wherein: in the InGaAlAs strain multi-quantum well and barrier, the barrier layer is composed of 3 layers of 2nm InGaAlAs barriers and 2 layers of 2nm InGaAlAs well superlattice structures.

Images