CN109830575B - Super-radiation light emitting diode epitaxial wafer, preparation method of epitaxial wafer and chip - Google Patents
Super-radiation light emitting diode epitaxial wafer, preparation method of epitaxial wafer and chip Download PDFInfo
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Abstract
The invention relates to the technical field of semiconductors, in particular to a super-radiation light-emitting diode epitaxial wafer, a preparation method of the epitaxial wafer and a chip, wherein the preparation method of the super-radiation light-emitting diode epitaxial wafer comprises the following steps: sequentially epitaxially growing a multilayer heterostructure on the surface of the substrate; and when the luminous layer grows, adjusting the growth temperature field to change along the gradient of the preset crystal orientation direction of the substrate, so that the thickness and the components of the luminous layer change along the gradient of the preset crystal orientation direction of the substrate. The gradient distribution of the light-emitting wavelength of the epitaxial wafer can be realized by adjusting the gradient change of the growth temperature field of the quantum well layer along the preset crystal orientation direction of the substrate, so that the obtained chip is superposed by multiple central wavelengths along the light-emitting direction, has wavelength continuity and can obtain a wide and flat spectrum; meanwhile, the process is simple and easy to implement and easy to repeat, only one-time epitaxial growth molding is needed, and the yield and reliability of the product are greatly improved.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of semiconductors, in particular to a super-radiation light-emitting diode epitaxial wafer, a preparation method of the epitaxial wafer and a chip.
[ background of the invention ]
The semiconductor super-radiation light-emitting diode is a one-way gain amplifying device for spontaneous light radiation, and the optical performance of the semiconductor super-radiation light-emitting diode is between that of a semiconductor laser and that of a semiconductor light-emitting diode. It has a wider light emission spectrum and a shorter coherence length relative to a semiconductor laser; compared with a semiconductor light emitting diode, the light emitting diode has the advantages of higher output power, higher optical fiber coupling efficiency, high response speed, small divergence angle and the like, and is widely applied to the fields of optical fiber gyroscopes, optical fiber sensing, optical coherence tomography and the like.
Of semiconductor superluminescent light-emitting diodes in fibre-optic gyro applicationsThe light coherence length can reduce Rayleigh scattering intensity in the fiber-optic gyroscope system, and the light coherence length L of the semiconductor super-radiation light-emitting diodeC＝λ2And/Δ λ, wherein Δ λ is the spectral width and λ is the center wavelength. It is therefore generally required that superluminescent light emitting diodes have a broad spectral width. The method for increasing the spectral bandwidth of the super-radiation light-emitting diode mainly changes the components or the thickness of the material in the growth direction; or a component or thickness that changes the direction of light extraction; and a combination of both approaches.
The current technologies for implementing the above schemes are various: for the super-radiation light-emitting diode with a multi-quantum well layer structure, the main technology is to change the material components or the thicknesses of different quantum well layers, so that the central wavelengths of light emitted by the quantum well layers are different, and finally the super-radiation light-emitting diode with high power and wide spectrum is realized through the spectral superposition of the different central wavelengths. However, since the emission wavelengths of the quantum well layers are not continuous, it is difficult to obtain a wide flat spectrum in this technical solution. The technologies for realizing the broad spectrum by changing the light emitting direction component and the thickness mainly include a multi-electrode method, SAG, a multi-quantum well hybrid technology and the like. The multi-electrode method is characterized in that a light emitting area is divided into a plurality of parts along a light emitting direction, different parts are injected with different currents, so that the corresponding light emitting center wavelengths are different, and a wide spectrum is obtained; in addition, when the LED is used, different electrodes are not consistent with light attenuation of the active region part, so that the LED is difficult to control. The SAG method is to deposit a medium film on the surface of a substrate and to photoetch a deposition area and a non-deposition area. The gas phase concentration on the surface of the substrate is influenced so as to change the components and the thickness of epitaxy in the light emitting direction, and the SAG method relates to a secondary epitaxy technology, has complex process, low product yield and poor reliability and is not easy to implement. The quantum well intermixing technology realizes the change of components in the light emitting direction by the mutual diffusion of well barriers, and has the defects of poor repeatability of the same process, difficult control and low product yield.
In view of the above, it is an urgent problem in the art to overcome the above-mentioned drawbacks of the prior art.
[ summary of the invention ]
The technical problems to be solved by the invention are as follows:
super-radiation light-emitting diodes generally require a wide spectrum, and in the conventional scheme, some methods have complex processes, poor reliability, difficulty in implementation and low product yield, while some methods have difficulty in obtaining a wide flat spectrum due to discontinuous light-emitting wavelength.
The invention achieves the above purpose by the following technical scheme:
in a first aspect, the invention provides a preparation method of a super-radiation light-emitting diode epitaxial wafer, wherein a multilayer heterostructure is sequentially epitaxially grown on the surface of a substrate 1; when the light-emitting layer 4 grows, the growth temperature field is adjusted to change along the preset crystal orientation direction of the substrate 1 in a gradient manner, so that the thickness and the components of the light-emitting layer 4 change along the preset crystal orientation direction of the substrate 1 in a gradient manner.
Preferably, the sequentially epitaxially growing the multilayer heterostructure on the surface of the substrate 1 specifically comprises: a buffer layer 2, a lower waveguide layer 3, a light-emitting layer 4, an upper waveguide layer 5, a spacer layer 6 and an ohmic contact layer 7 are sequentially stacked on the surface of a substrate 1.
Preferably, the growth temperature fields of the buffer layer 2, the lower waveguide layer 3, the upper waveguide layer 5, the spacer layer 6 and the ohmic contact layer 7 are uniform temperature fields or non-uniform temperature fields.
Preferably, the gradient change of the growth temperature field of the light-emitting layer 4 is realized by controlling the temperature of different temperature zones in the epitaxial growth zone, specifically:
dividing the epitaxial growth area into at least two temperature areas in advance according to the direction from the center to the outer edge of the epitaxial growth area, wherein the heating power of each temperature area is independently adjusted;
placing the substrate 1 on the epitaxial growth area, and enabling the preset crystal orientation direction of the substrate 1 to be consistent with the arrangement distribution direction of the at least two temperature areas;
when the light-emitting layer 4 grows, the heating power of each temperature area is respectively adjusted, so that the temperature is changed in a gradient manner along the direction from the center to the outer edge of the epitaxial growth area, and further the thickness and the components of the light-emitting layer 4 are changed in a gradient manner along the direction from the center to the outer edge of the epitaxial growth area.
Preferably, the gradient change of the growth temperature field along the preset crystal orientation direction of the substrate 1 is specifically: the growth temperature is sequentially increased in an increasing manner along the preset crystal orientation direction of the substrate 1, or sequentially decreased in a decreasing manner, or sequentially increased in an increasing manner and then decreased in an decreasing manner, or sequentially decreased in an decreasing manner and then increased in an increasing manner.
Preferably, the substrate 1 and the multilayer heterostructure are InGaAsP/InP material system, AlGaInAs/InP material system or AlGaAs/GaAs material system, and the light emitting layer 4 is InGaAsP, AlGaInAs or AlGaAs.
In a second aspect, the invention further provides a super-radiation light-emitting diode epitaxial wafer, which is manufactured by the preparation method of the super-radiation light-emitting diode epitaxial wafer in the first aspect, and comprises a substrate 1, and a buffer layer 2, a lower waveguide layer 3, a light-emitting layer 4, an upper waveguide layer 5, a spacer layer 6 and an ohmic contact layer 7 which are sequentially stacked and grown on the surface of the substrate 1; the growth temperature field of the light-emitting layer 4 is changed along the preset crystal orientation direction of the substrate 1 in a gradient manner, so that the thickness and the components of the light-emitting layer 4 are changed along the preset crystal orientation direction of the substrate 1 in a gradient manner.
Preferably, the substrate 1 is semiconductor InP, the buffer layer 2 is n-type InP, the lower waveguide layer 3 is n-type InGaAsP, the light emitting layer 4 is InGaAsP, the upper waveguide layer 5 is P-type InGaAsP, and the spacer layer 6 is a P-type spacer layer.
In a third aspect, the invention further provides a superluminescent light emitting diode chip, which is prepared by the epitaxial wafer of the second aspect through the processes of photoetching, etching, dielectric film growth and electrode manufacturing; the epitaxial wafer is obtained by the preparation method of the epitaxial wafer of the super-radiation light-emitting diode in the first aspect.
Preferably, the light emitting layer 4 is aligned with a thickness gradient change direction of the light emitting layer 4 in a direction of a current injection stripe region.
Compared with the prior art, the invention has the beneficial effects that:
the gradient distribution of the light-emitting wavelength of the epitaxial wafer can be realized by adjusting the gradient change of the growth temperature field of the quantum well layer along the preset crystal orientation direction of the substrate, so that the obtained chip is superposed by multiple central wavelengths along the light-emitting direction, has wavelength continuity, effectively increases the spectral bandwidth, and is easy to obtain a wide and flat spectrum; meanwhile, the process is simple and easy to implement and easy to repeat, only one-time epitaxial growth molding is needed, the limitation of a light-emitting layer structure is avoided, and the yield and the reliability of the product are greatly improved.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic structural diagram of a superluminescent diode epitaxial wafer according to an embodiment of the present invention;
fig. 2 is a schematic view of temperature zones for epitaxial wafer growth according to an embodiment of the present invention;
fig. 3 is a schematic diagram of temperature adjustment during growth of a light-emitting layer of an epitaxial wafer according to an embodiment of the present invention (temperature gradient decreases from region a to region C);
fig. 4 is a schematic diagram of temperature adjustment during growth of a light-emitting layer of an epitaxial wafer according to an embodiment of the present invention (temperature gradient increases from region a to region C);
fig. 5 is a schematic diagram illustrating temperature adjustment during growth of a light-emitting layer of an epitaxial wafer according to an embodiment of the present invention (the temperature decreases and then increases from region a to region C);
fig. 6 is a schematic diagram illustrating temperature adjustment during growth of a light-emitting layer of an epitaxial wafer according to an embodiment of the present invention (the temperature increases and then decreases from region a to region C);
fig. 7 is a schematic structural diagram of a superluminescent light emitting diode chip according to an embodiment of the present invention;
fig. 8 is a schematic diagram of an emission spectrum emitted from a superluminescent light emitting diode chip according to an embodiment of the present invention.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "up", "down", "top", "bottom", "left", "right", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention but do not require that the present invention must be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. The invention will be described in detail below with reference to the figures and examples.
Example 1:
the embodiment of the invention provides a preparation method of a super-radiation light-emitting diode epitaxial wafer, as shown in fig. 1, a multilayer heterostructure is epitaxially grown on the surface of a substrate 1 in sequence, and the method specifically comprises the following steps: a buffer layer 2, a lower waveguide layer 3, a light-emitting layer 4, an upper waveguide layer 5, a spacer layer 6 and an ohmic contact layer 7 are sequentially stacked on the surface of a substrate 1. The growth temperature field of the light-emitting layer 4 is different from a uniform temperature field of a general epitaxial layer growth, but is a non-uniform temperature field, that is, when the light-emitting layer 4 grows, the growth temperature is changed in a gradient manner along a preset crystal orientation direction of the substrate 1 by adjusting the growth temperature field, so that the thickness and components of the light-emitting layer 4 are changed in a gradient manner along the preset crystal orientation direction of the substrate 1, and the light-emitting center wavelength is changed in a gradient manner along the direction. The epitaxial wafer can be used for preparing a super-radiation light-emitting diode chip, and the obtained chip is superposed by multiple central wavelengths along the light-emitting direction, so that the aim of increasing the spectral bandwidth of the light-emitting diode can be fulfilled.
In the preparation method of the epitaxial wafer provided by the embodiment of the invention, the gradient distribution of the light-emitting wavelength of the epitaxial wafer can be realized by adjusting the gradient change of the growth temperature field of the quantum well layer along the preset crystal orientation direction of the substrate, and the chip obtained on the basis of the epitaxial wafer is superposed by multiple central wavelengths along the light-emitting direction and has wavelength continuity, so that a wide and flat spectrum can be obtained; meanwhile, the process is simple and easy to implement and easy to repeat, and only one-time epitaxial growth molding is needed, so that the yield and reliability of the product are greatly improved.
The growth temperature fields of the buffer layer 2, the lower waveguide layer 3, the upper waveguide layer 5, the spacer layer 6 and the ohmic contact layer 7 can be uniform temperature fields, that is, the temperature of each epitaxial layer structure is consistent during growth, so that a structure layer with uniform thickness is obtained; the temperature field may be non-uniform, and the structural layer with non-uniform thickness is obtained, and the formation of the wide bandwidth is not affected, so the method is not limited. In addition, other insertion layers can be arranged among the buffer layer 2, the lower waveguide layer 3, the upper waveguide layer 5, the spacer layer 6 and the ohmic contact layer 7 according to actual production requirements, and the present invention is not limited to the above epitaxial structure layers.
The method provided by the invention is suitable for various different light-emitting layer structures of the super-radiation light-emitting diode, is not limited by the light-emitting layer structures, and has universality. For example, the substrate 1 and the multilayer heterostructure may be an InGaAsP/InP material system, an AlGaInAs/InP material system, or an AlGaAs/GaAs material system, and the light emitting layer 4 may be InGaAsP, AlGaInAs, or AlGaAs. In the embodiment of the present invention, an InGaAsP/InP material system is taken as an example, the substrate 1 is a semiconductor InP substrate, the buffer layer 2 is an n-type InP buffer layer, the lower waveguide layer 3 is an n-type InGaAsP waveguide layer, the light-emitting layer 4 is an InGaAsP light-emitting layer, the upper waveguide layer 5 is a P-type InGaAsP waveguide layer, and the spacer layer 6 is a P-type spacer layer.
Taking the light emitting layer 4 as InGaAsP as an example, there is competition for incorporation of elements during the growth process: ga and In of group iii compete, As and P of group v compete, and the composition content of In and As therein has a greater influence on the wavelength and thickness, so that the description is made here In and As. When the temperature changes, the In component and the As component which are incorporated into the material of the luminescent layer change along with the temperature change, so that the forbidden band width of the material of the luminescent layer and the growth rate of the material are changed, and the luminescent wavelength is changed. The method comprises the following specific steps: when the light emitting layer 4 is grown, the lower the temperature is, the more In components and As components are incorporated, and the faster the growth rate is; the larger the contents of the In component and the As component, the narrower the forbidden bandwidth of the material of the light emitting layer, the longer the corresponding light emitting wavelength, and the increased thickness of the light emitting layer. The higher the temperature is, the less the In component and As component are incorporated, the slower the growth rate becomes; for a semiconductor super-radiation light-emitting diode, the smaller the contents of the In component and the As component of the light-emitting layer, the wider the forbidden bandwidth of the material of the light-emitting layer, the shorter the corresponding light-emitting wavelength, and the thinner the light-emitting layer.
In the embodiment of the present invention, the gradient change of the growth temperature field of the light emitting layer 4 can be realized by controlling the temperatures of different temperature regions in the epitaxial growth region, which is specifically as follows:
first, the epitaxial growth region is divided into at least two temperature regions in advance in a direction from the center to the outer edge of the epitaxial growth region, and the heating power of each temperature region is independently adjusted. In the embodiment of the present invention, the fabrication of the epitaxial wafer is completed on an MOCVD machine by using a Metal-organic Chemical Vapor Deposition (MOCVD) technique, as in the conventional fabrication method. Specifically, referring to fig. 2, a circular tray 8 is disposed on the MOCVD equipment, where the tray 8 is an epitaxial growth zone, and in this embodiment, A, B, C temperature zones are set as an example, and a zone a, a zone B, and a zone C are respectively disposed along the center to the outer edge of the tray 8.
Then, the substrate 1 is placed on the epitaxial growth region, and the preset crystal orientation direction of the substrate 1 is consistent with the arrangement distribution direction of the at least two temperature regions. As shown in fig. 2, a plurality of substrates 1 can be placed on the tray 8, and a plurality of epitaxial wafers can be simultaneously fabricated; wherein a represents the crystal orientation direction of the substrate 1, and the arrangement directions of the three temperature regions A, B and C are consistent along the center of the tray 8 to the outer edge of the tray 8.
And finally, when the light-emitting layer 4 grows, the heating power of each temperature area is respectively adjusted, so that the temperature is changed in a gradient manner along the direction from the center of the epitaxial growth area to the outer edge, and further the thickness and the components of the light-emitting layer 4 are changed in a gradient manner along the direction from the center of the epitaxial growth area to the outer edge. The advantages of accurate temperature control and high temperature repeatability of an MOCVD machine are utilized to respectively adjust the heating power of the area A, the area B and the area C, so that the temperature changes in a gradient manner from the center of the tray 8 to the outer edge of the tray 8, and a line B with an arrow in figure 2 shows the gradient change direction of the temperature and is consistent with the crystal direction a. The order of the third step and the second step can be interchanged, and is not limited to only placing the substrate first and then adjusting the temperature, or placing the substrate after adjusting the temperature.
Although the heating powers of the zones A, B and C are independently adjusted, the three temperature zones are mutually influenced in temperature, for example, the heating power of the zone A is adjusted to have the largest influence on the temperature of the zone A, but the temperatures of the zone B and the zone C are influenced at the same time, and the influence degree is that the zone A is larger than the zone B and is larger than the zone C. When the temperature division is performed in advance, a plurality of times of test adjustment and verification are required, so that after the division is completed, the temperature can be changed in a gradient manner along the direction from the center of the tray 8 to the outer edge of the tray 8 by adjusting the heating power of each area.
The gradient change of the growth temperature along the preset crystal orientation direction of the substrate 1 may specifically be: the growth temperature is sequentially increased in an increasing manner along the preset crystal orientation direction of the substrate 1, or sequentially decreased in a decreasing manner, or sequentially increased in an increasing manner and then decreased in an decreasing manner, or sequentially decreased in an decreasing manner and then increased in an increasing manner; the temperature difference can be adjusted according to actual needs without limitation. The following description is provided for various gradient changes:
referring to fig. 3, it is assumed that the temperature distribution gradually decreases in the direction from the center of the tray 8 to the edge of the tray 8, that is, in the direction from the a region to the B region to the C region (direction B in fig. 2) when the light emitting layer is grown. In the epitaxial wafer grown under this condition, the contents of the In component and the As component In the luminescent layer gradually increase along the direction from the center of the tray 8 to the edge of the tray 8, and the thickness of the luminescent layer also gradually increases along the direction from the center of the tray 8 to the edge of the tray 8, so that the distribution of the luminescence wavelength can be obtained to gradually lengthen along the direction from the center of the tray 8 to the edge of the tray 8.
Referring to fig. 4, it is assumed that the temperature distribution gradually increases in the direction from the center of the tray 8 to the edge of the tray 8, that is, in the direction from the a region to the B region to the C region (direction B in fig. 2) when the light emitting layer is grown. In the epitaxial wafer grown under this condition, the contents of the In component and the As component In the luminescent layer gradually decrease along the direction from the center of the tray 8 to the edge of the tray 8, and the thickness of the luminescent layer also gradually decreases along the direction from the center of the tray 8 to the edge of the tray 8, so that the distribution of the luminescence wavelength can be obtained to be gradually shortened along the direction from the center of the tray 8 to the edge of the tray 8.
Referring to fig. 5, it is assumed that, when growing a light emitting layer, the temperature distribution first decreases and then increases in the direction from the center of the tray 8 to the edge of the tray 8, that is, in the direction from the a region to the B region to the C region (direction B in fig. 2). In the epitaxial wafer grown under the condition, the contents of In components and As components In the luminescent layer increase and then decrease along the direction from the center of the tray 8 to the edge of the tray 8, and the thickness of the luminescent layer also increases and then decreases along the direction from the center of the tray 8 to the edge of the tray 8, so that the distribution of the luminescent wavelength can be gradually lengthened and then gradually shortened along the direction from the center of the tray 8 to the edge of the tray 8.
Referring to fig. 6, it is assumed that, when growing a light emitting layer, the temperature distribution first increases and then decreases in the direction from the center of the tray 8 to the edge of the tray 8, that is, in the direction from the a region to the B region to the C region (direction B in fig. 2). In the epitaxial wafer grown under the condition, the contents of In components and As components In the luminescent layer are firstly reduced and then increased along the direction from the center of the tray 8 to the edge of the tray 8, and the thickness of the luminescent layer is also firstly reduced and then increased along the direction from the center of the tray 8 to the edge of the tray 8, so that the distribution of the luminescent wavelength can be obtained along the direction from the center of the tray 8 to the edge of the tray 8, and the luminescent wavelength is firstly gradually shortened and then gradually lengthened.
When the temperature is increased first and then decreased gradually, or decreased first and then increased gradually, that is, under the temperature distribution condition corresponding to fig. 5 or fig. 6, not only the superluminescent light emitting diode with a wide and flat light emitting spectrum can be obtained, but also the wavelength of the monolithic epitaxial wafer can be more concentrated, and the yield of the prepared superluminescent light emitting diode chip can be higher, which is beneficial to improving the yield.
Example 2:
on the basis of the embodiment 1, the embodiment of the invention also provides a super-radiation light-emitting diode epitaxial wafer, which is obtained by adopting the preparation method of the super-radiation light-emitting diode epitaxial wafer in the embodiment 1.
As shown in fig. 1, the epitaxial wafer includes a substrate 1, and a buffer layer 2, a lower waveguide layer 3, a light emitting layer 4, an upper waveguide layer 5, a spacer layer 6, and an ohmic contact layer 7, which are sequentially stacked and grown on a surface of the substrate 1. The growth temperature field of the light-emitting layer 4 is a non-uniform temperature field, that is, the growth temperature changes along the preset crystal orientation direction of the substrate 1 in a gradient manner, and the thickness and the components of the obtained light-emitting layer 4 change along the preset crystal orientation direction of the substrate 1 in a gradient manner, so that the light-emitting center wavelength changes along the direction in a gradient manner. The epitaxial wafer can be used for preparing a super-radiation light-emitting diode chip, and the obtained chip is superposed by multiple central wavelengths along the light-emitting direction, so that the aim of increasing the spectral bandwidth of the light-emitting diode can be fulfilled. The specific preparation method of the epitaxial wafer can refer to example 1, and details are not repeated here.
The epitaxial wafer provided by the invention is suitable for various material systems, such as InGaAsP/InP material systems, AlGaInAs/InP material systems or AlGaAs/GaAs material systems. Taking an InGaAsP/InP material system as an example, the substrate 1 is a semiconductor InP substrate, the buffer layer 2 is an n-type InP buffer layer, the lower waveguide layer 3 is an n-type InGaAsP waveguide layer, the light-emitting layer 4 is an InGaAsP light-emitting layer, the upper waveguide layer 5 is a P-type InGaAsP waveguide layer, and the spacer layer 6 is a P-type spacer layer. If the waveguide layer is an AlGaInAs/InP material system, the difference between the AlGaInAs/InP material system and the InGaAsP/InP material system is that the lower waveguide layer 3 is an n-type AlGaInAs waveguide layer, the light-emitting layer 4 is an AlGaInAs light-emitting layer, and the upper waveguide layer 5 is a P-type AlGaInAs waveguide layer; if the light emitting layer is an AlGaAs/GaAs material system, the difference from the InGaAsP/InP material system is that the substrate 1 is a semiconductor GaAs substrate, the buffer layer 2 is an n-type GaAs buffer layer, the lower waveguide layer 3 is an n-type AlGaAs waveguide layer, the light emitting layer 4 is an AlGaAs light emitting layer, and the upper waveguide layer 5 is a P-type AlGaAs waveguide layer.
Specifically, the gradient change of the growth temperature along the predetermined crystal orientation direction of the substrate 1 may be sequentially increasing, sequentially decreasing, sequentially increasing and then decreasing, or sequentially decreasing and then increasing, so that the obtained thickness distribution of the light emitting layer is also different. Taking the light emitting layer 4 As InGaAsP As an example, referring to fig. 1, when the growth temperature gradient increases from left to right In the figure, the incorporation of In component and As component In the light emitting layer 4 gradually decreases, and the light emitting layer thickness gradient decreases. Similarly, when the temperature gradient decreases from left to right, the thickness gradient of the light-emitting layer 4 increases, as shown in fig. 3; when the growth temperature is first decreased in a gradient and then increased in a gradient from left to right, the thickness of the light-emitting layer 4 is first increased in a gradient and then decreased in a gradient, as shown in fig. 5; when the growth temperature is increased in a gradient manner and then decreased in a gradient manner from left to right, the thickness of the light-emitting layer 4 is decreased in a gradient manner and then increased in a gradient manner, as shown in fig. 6.
In the embodiment of the invention, the growth temperature fields of the buffer layer 2, the lower waveguide layer 3, the upper waveguide layer 5, the spacer layer 6 and the ohmic contact layer 7 can be uniform temperature fields, so as to obtain a structural layer with uniform thickness; or non-uniform temperature field, and obtaining a structural layer with non-uniform thickness, without limitation. In addition, other insertion layers can be arranged among the buffer layer 2, the lower waveguide layer 3, the upper waveguide layer 5, the spacer layer 6 and the ohmic contact layer 7 according to actual production requirements, and the present invention is not limited to the above epitaxial structure layers.
In the epitaxial wafer provided by the embodiment of the invention, the thickness and the components of the light-emitting layer are changed along the gradient of the preset crystal orientation direction of the substrate, so that the gradient distribution of the light-emitting wavelength can be realized, the chips obtained on the basis of the epitaxial wafer are superposed for multiple central wavelengths along the light-emitting direction, the spectral bandwidth can be effectively increased, the wavelength continuity is realized, and a wide and flat spectrum can be obtained.
Example 3:
on the basis of the foregoing embodiment 1 and embodiment 2, an embodiment of the present invention further provides a superluminescent light emitting diode chip, which is prepared by performing photolithography, etching, dielectric film growth, and electrode manufacturing processes on an epitaxial wafer (i.e., the epitaxial wafer in embodiment 2) prepared by the method described in embodiment 1. The method specifically comprises the following steps: after the epitaxial wafer is prepared by the method in the embodiment 1, a ridge waveguide structure is etched on the surface of the epitaxial wafer by a ridge waveguide etching process, and an electrode window is etched in an alignment manner; then, manufacturing an upper electrode by adopting methods such as evaporation or sputtering and the like; then thinning the substrate and manufacturing a lower metal electrode. Meanwhile, in order to further reduce the reflection of the end faces, antireflection films may be generally plated on the two light-emitting end faces, and the finally obtained superluminescent light-emitting diode chip is shown in fig. 7. For the preparation and characteristics of the epitaxial wafer, reference may be made to embodiments 1 and 2, which are not described herein again.
With continued reference to fig. 7, in the superluminescent light emitting diode prepared from the epitaxial wafer, the light emitting layer 4 is consistent with the thickness gradient change direction of the light emitting layer 4 along the direction of the current injection stripe region; wherein, the arrow c represents the current injection direction, the arrow d represents the thickness gradient change direction of the light-emitting layer 4, i.e. the wavelength gradient change direction, the arrow e represents the current injection strip region direction, and the arrow f represents the light-emitting direction of the superluminescent light-emitting diode die. The light emitting layer 4 is consistent with the thickness gradient change direction of the light emitting layer 4 along the direction of the current injection stripe region, specifically: the light emitting layer 4 is completely the same as the thickness gradient change direction along the current injection stripe region direction, or the light emitting layer 4 forms a small angle with the thickness gradient change direction along the current injection stripe region direction.
When the light-emitting layer 4 is consistent with the thickness gradient change direction of the light-emitting layer 4 along the direction of the current injection strip region, the superluminescent light-emitting diode chip is superposed by multiple central wavelengths along the light-emitting direction, so that the purpose of increasing the spectral bandwidth of the light-emitting diode can be achieved. As shown in fig. 8, a curve m represents the light-emitting spectrum of the conventional superluminescent led chip, and a curve n represents the light-emitting spectrum of the superluminescent led chip according to the embodiment of the present invention. Compared with the existing super-radiation light-emitting diode chip, the super-radiation light-emitting diode chip provided by the embodiment of the invention has the advantages that the bandwidth is increased, and because the single chip has wavelength continuity along the light-emitting direction, a wide and flat spectrum can be easily obtained under different currents, and the advantages are more remarkable when the super-radiation light-emitting diode chip is used in a high-power super-radiation light-emitting diode.
By combining the embodiments 1 to 3, the epitaxial wafer and the chip of the superluminescent diode provided by the invention have the following advantages: the gradient distribution of the light-emitting wavelength of the epitaxial wafer can be realized by adjusting the gradient change of the growth temperature field of the quantum well layer along the preset crystal orientation direction of the substrate, so that the aim of increasing the spectral bandwidth of the light-emitting diode chip is fulfilled; the process is simple and easy to implement and easy to repeat, and only one-time epitaxial growth molding is needed, so that the yield and the reliability of the product are greatly improved; the wavelength continuity of a single tube core along the light-emitting direction can be realized, a wide and flat spectrum can be easily obtained under different currents, and the advantages are more obvious when the super-radiation light-emitting diode is used in a high-power super-radiation light-emitting diode; the material can be applied to various material systems, is not limited by a luminescent layer structure, and has universality.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. A preparation method of a super-radiation light-emitting diode epitaxial wafer is characterized in that a multilayer heterostructure is sequentially epitaxially grown on the surface of a substrate (1); when the light-emitting layer (4) grows, adjusting a growth temperature field to change along the preset crystal orientation direction gradient of the substrate (1) so as to change the thickness and the components of the light-emitting layer (4) along the preset crystal orientation direction gradient of the substrate (1);
the contents of In components and As components In the luminescent layer (4) are firstly reduced and then increased along the direction from the center of the tray (8) to the edge of the tray (8), the thickness of the luminescent layer is also firstly reduced and then increased along the direction from the center of the tray (8) to the edge of the tray (8), and the obtained distribution of the luminescent wavelength is firstly gradually shortened and then gradually lengthened along the direction from the center of the tray (8) to the edge of the tray (8).
2. The method for preparing the epitaxial wafer of the super-radiation light-emitting diode according to claim 1, wherein the sequentially epitaxially growing the multilayer heterostructure on the surface of the substrate (1) is specifically as follows: a buffer layer (2), a lower waveguide layer (3), a luminescent layer (4), an upper waveguide layer (5), a spacer layer (6) and an ohmic contact layer (7) are sequentially stacked and grown on the surface of a substrate (1).
3. The preparation method of the super-radiation light-emitting diode epitaxial wafer according to the claim 2 is characterized in that the growth temperature fields of the buffer layer (2), the lower waveguide layer (3), the upper waveguide layer (5), the spacer layer (6) and the ohmic contact layer (7) are uniform temperature fields or non-uniform temperature fields.
4. The method for preparing the epitaxial wafer of the super-radiation light-emitting diode according to claim 1, wherein the gradient change of the growth temperature field of the light-emitting layer (4) is realized by controlling the temperature of different temperature zones in the epitaxial growth zone, and specifically comprises the following steps:
dividing the epitaxial growth area into at least two temperature areas in advance according to the direction from the center to the outer edge of the epitaxial growth area, wherein the heating power of each temperature area is independently adjusted;
placing the substrate (1) on the epitaxial growth area, and enabling the preset crystal orientation direction of the substrate (1) to be consistent with the arrangement distribution direction of the at least two temperature areas;
when the light-emitting layer (4) grows, the heating power of each temperature area is respectively adjusted, so that the temperature is changed in a gradient manner along the direction from the center of the epitaxial growth area to the outer edge, and further the thickness and the components of the light-emitting layer (4) are changed in a gradient manner along the direction from the center of the epitaxial growth area to the outer edge.
5. The method for preparing the super-radiation light-emitting diode epitaxial wafer according to any one of claims 1 to 4, characterized in that the substrate (1) and the multilayer heterostructure are InGaAsP/InP material system, AlGaInAs/InP material system or AlGaAs/GaAs material system, and the light-emitting layer (4) is InGaAsP, AlGaInAs or AlGaAs correspondingly.
6. The super-radiation light-emitting diode epitaxial wafer is characterized by comprising a substrate (1), and a buffer layer (2), a lower waveguide layer (3), a light-emitting layer (4), an upper waveguide layer (5), a spacer layer (6) and an ohmic contact layer (7) which are sequentially stacked and grown on the surface of the substrate (1); the growth temperature field of the light-emitting layer (4) is changed along the preset crystal orientation direction of the substrate (1) in a gradient manner, so that the thickness and the components of the light-emitting layer (4) are changed along the preset crystal orientation direction of the substrate (1) in a gradient manner;
the contents of In components and As components In the luminescent layer (4) are firstly reduced and then increased along the direction from the center of the tray (8) to the edge of the tray (8), the thickness of the luminescent layer is also firstly reduced and then increased along the direction from the center of the tray (8) to the edge of the tray (8), and the obtained distribution of the luminescent wavelength is firstly gradually shortened and then gradually lengthened along the direction from the center of the tray (8) to the edge of the tray (8).
7. The superluminescent light emitting diode epitaxial wafer according to claim 6, wherein the substrate (1) is semiconductor InP, the buffer layer (2) is n-type InP, the lower waveguide layer (3) is n-type InGaAsP, the light emitting layer (4) is InGaAsP, the upper waveguide layer (5) is P-type InGaAsP, and the spacer layer (6) is P-type spacer layer.
8. A super-radiation light emitting diode chip is characterized in that the chip is prepared by an epitaxial wafer through photoetching, etching, dielectric film growth and electrode manufacturing processes; the epitaxial wafer is obtained by the preparation method of the super-radiation light-emitting diode epitaxial wafer in the claims 1-5.
9. The superluminescent light emitting diode chip of claim 8, wherein the light emitting layer (4) coincides with a direction of a thickness gradient of the light emitting layer (4) in a direction of a current injection stripe region.
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