JP2005340644A - Light emitting diode and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To widen the band of a light emitting diode while suppressing its manufacturing process from becoming complex. <P>SOLUTION: A stripe waveguide 2 and stripe waveguides 12, 22, and 32 branching from the stripe waveguide 2 are provided on a substrate 1. An active layer for light emitting action is formed on each of the stripe waveguides 2, 12, 22, and 32. The length of the active layer provided to the stripe waveguides 12, 22, and 32 is set to be different from each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light-emitting diode and a method for manufacturing the light-emitting diode, and is particularly suitable for application to a broadband superluminescent diode.

Semiconductor lasers and light emitting diodes are well known as conventional light emitting devices using semiconductors.
Since the semiconductor laser generates light using an amplification effect by stimulated emission, it has excellent high output characteristics and spatial coherence characteristics, and can obtain good coupling efficiency in coupling with an optical fiber. On the other hand, since the semiconductor laser has high coherence, interference noise is generated, and the measurement accuracy may be deteriorated in a field such as optical measurement.
Further, since the light emitting diode has low coherence, no interference noise is generated, but the coupling loss with the optical fiber is large, and the application as a light source for optical measurement has been limited.

Superluminescent diodes, on the other hand, use amplifying effects due to stimulated emission, so they can generate high-power light while having a wide spectral band like light-emitting diodes, and can be coupled to optical fibers. Can be obtained as a light source for optical measurement.
This super luminescent diode is put into practical use as a light source such as a white light source, an optical fiber gyro, and a high resolution OTDR (Optical Time Delay Reflectometer). In addition, application to fields such as biological light observation has been studied, and in order to increase the resolution, there is an increasing demand for a broadband superluminescent diode.

Non-Patent Document 1 discloses a method of forming a multilayer strained quantum well structure by stacking semiconductor layers having different band gaps during semiconductor crystal growth in order to increase the bandwidth of a superluminescent diode. .
Further, Non-Patent Document 2 discloses a method for increasing the bandwidth of a superluminescent diode by arranging semiconductor layers having different band gaps in the light propagation direction.
Fumio Koyama “Tapered Superluminescent Diode”, Applied Physics Vol. 68, No. 2 (1999) Osamu Mikami, Hiroshi Yasaka, and Yoshi Noguchi “Broader spectral width InGaAsP stacked active layered superdiodes”

  However, in the conventional superluminescent diode manufacturing method, a multilayer structure of quantum wells with different thicknesses is formed or the band gap is changed in the light propagation direction in order to increase the bandwidth of the superluminescent diode. It is necessary to let them. For this reason, in the conventional manufacturing method of a super luminescent diode, there existed a problem that a manufacturing process became complicated and the manufacturing yield deteriorated.

In addition, the spectrum shape of conventional superluminescent diodes is also determined by the structure of the active layer and waveguide, and the spectrum shape cannot be adjusted, so multi-peaks may occur, and an ideal Gaussian spectrum is obtained. It was difficult. For this reason, a side rope appears next to the peak of the autocorrelation function, causing a ghost or the like to occur in the observed image, which makes it difficult to apply to fields such as biological light observation. .
Accordingly, an object of the present invention is to provide a light-emitting diode and a method for manufacturing the light-emitting diode capable of widening the bandwidth while suppressing the complexity of the manufacturing process.

In order to solve the above-described problem, the light emitting diode according to claim 1 is characterized in that an optical waveguide branched in the middle is provided so that the lengths of the light emitting regions are different from each other.
Accordingly, it is possible to change the peak wavelength of the spectrum by changing the length of the light emitting region of the optical waveguide, and it is possible to multiplex light having different peak wavelengths. Therefore, by changing the shape at the time of patterning the optical waveguide, it becomes possible to achieve a broad band of the light emitting diode, and in order to achieve a broad band of the light emitting diode, a multilayer strain quantum well structure is provided in the optical waveguide, It is not necessary to form semiconductor layers having different band gaps along the light propagation direction. As a result, it is possible to increase the bandwidth of the light-emitting diode while suppressing the complexity of the manufacturing process, and to improve the manufacturing yield.

According to a second aspect of the present invention, the light-emitting diode further includes electrodes for individually injecting currents into the branched optical waveguides.
As a result, the amount of current during operation can be adjusted for each of the optical waveguides having different lengths of the light emitting regions, and the spectrum shape can be adjusted while achieving a broad band of the light emitting diodes. For this reason, even when the light emitting diode is broadened, an ideal Gaussian spectrum shape can be obtained, and a single peak autocorrelation function can be obtained while preventing the occurrence of side ropes. As a result, it is possible to prevent ghosts and the like from occurring in the observation image, and application to fields such as biological light observation can be easily performed.

The light emitting diode according to claim 3 is characterized in that branch points are provided at a plurality of locations of the optical waveguide.
Accordingly, the number of branches of the optical waveguide can be easily increased, and the number of optical waveguides branched so that the lengths of the light emitting regions are different from each other can be easily increased. For this reason, it is possible to increase the bandwidth of the light emitting diode while suppressing the complexity of the manufacturing process.

According to the light emitting diode of claim 4, the end of the branched optical waveguide is separated from the end face.
As a result, it is possible to suppress the end face reflection at the end of the optical waveguide, to suppress the resonant action of the light guided through the optical waveguide, and to prevent laser oscillation in a high output operation. Therefore, it is possible to reduce the coherence while enabling operation in a wide spectral band, and to improve the resolution while suppressing the generation of interference noise, and widely used as a light source for optical measurement. be able to.

According to the light-emitting diode of claim 5, the optical waveguide is configured such that the first optical waveguide provided with an active layer and the active layer have different lengths, and the first optical waveguide And a second optical waveguide branched from the waveguide.
As a result, light having different peak wavelengths can be generated by the first and second optical waveguides, and the light respectively generated by these optical waveguides can be multiplexed, which complicates the manufacturing process. It is possible to increase the bandwidth of the light-emitting diode while suppressing the increase in the frequency.

According to the light emitting diode of claim 6, the first electrode for injecting current into the first optical waveguide and the first electrode are electrically separated from each other, and the current is supplied to the second optical waveguide. And a second electrode for injecting.
This makes it possible to separately adjust the amount of current injected into the first and second optical waveguides. For this reason, it is possible to obtain an ideal Gaussian spectrum shape while widening the band of the light emitting diode, and it is possible to easily apply to a field such as biological light observation.

The light-emitting diode according to claim 7 is characterized in that the first active layer and the second active layer have a stripe structure.
As a result, the peak wavelength of the spectrum can be changed by changing the stripe length, and light having different peak wavelengths can be combined, and the manufacturing process is suppressed, and the light emitting diode is suppressed. It is possible to increase the bandwidth.

The light emitting diode according to claim 8, wherein the lower clad layer formed on the semiconductor substrate and the plurality of stripe structures formed on the lower clad layer and branched in the middle so as to have different lengths. And an embedded layer embedded on both sides of the active layer, and an upper clad layer formed on the active layer and the embedded layer.
As a result, it is possible to branch the active layer in the middle so that the lengths to the ends are different from each other while suppressing waveguide loss, and it is possible to increase the bandwidth of the light emitting diode while suppressing the complexity of the manufacturing process. It becomes possible to plan.

  According to the light emitting diode of claim 9, the step of forming a lower clad layer on the semiconductor substrate by epitaxial growth, the step of forming an active layer on the lower clad layer by epitaxial growth, and the active layer Forming an oxide film on the substrate, patterning the oxide film to have a plurality of stripe shapes branched in the middle so that the lengths are different from each other, and etching the active layer using the oxide film as a mask By patterning the active layer to have a plurality of stripe shapes branched in the middle so that the lengths are different from each other, and performing epitaxial growth using the oxide film as a mask, both sides of the active layer are formed. Selectively forming an embedded buried layer, and an upper cladding on the active layer and the buried layer Characterized in that it comprises a step of forming a.

  As a result, the active layer is etched using the oxide film formed on the active layer as a mask, thereby forming on the semiconductor substrate an optical waveguide branched in the middle so that the lengths of the active layers are different from each other. And the peak wavelengths of the spectrum of the light generated in each optical waveguide can be made different from each other. For this reason, it is possible to increase the bandwidth of the light-emitting diode without providing a multilayer strained quantum well structure in the optical waveguide or forming a semiconductor layer having a different band gap along the light propagation direction. Can be improved.

The light emitting diode according to claim 10, wherein a conductive film is formed on the upper clad layer, and the conductive film is patterned to form electrodes that are electrically isolated from each other for each stripe. And a step of performing.
As a result, the amount of current during operation can be adjusted for each of the optical waveguides having different lengths of the light emitting regions, and the spectrum shape can be adjusted while achieving a broad band of the light emitting diodes.

  As described above, according to the present invention, by changing the length of the light emitting region of the optical waveguide, it becomes possible to change the peak wavelength of the spectrum of the light generated in the optical waveguide, thereby complicating the manufacturing process. Thus, it is possible to increase the bandwidth of the light emitting diode.

Hereinafter, a light emitting diode and a method for manufacturing the light emitting diode according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing a schematic configuration of a light emitting diode according to a first embodiment of the present invention.
In FIG. 1, a stripe waveguide 2 and stripe waveguides 12, 22, and 32 branched from the stripe waveguide 2 are provided on a substrate 1. Here, each stripe waveguide 2, 12, 22, and 32 is provided with an active layer that emits light. An electrode 13 for injecting current into the active layer provided in the stripe waveguides 2 and 12 is disposed on the stripe waveguides 2 and 12, and provided on the stripe waveguide 22 on the stripe waveguide 22. An electrode 23 for injecting current into the active layer is disposed, and an electrode 33 for injecting current into the active layer provided in the stripe waveguide 32 is disposed on the stripe waveguide 23. Antireflection films 41 and 42 are respectively formed on both end faces of the substrate 1 on which the stripe waveguides 2, 12, 22, and 32 are provided.

In addition, it is preferable that the electrodes 13, 23, and 33 for injecting current into the stripe waveguides 12, 22, and 32 are electrically separated from each other. Further, the end of the stripe waveguide 2 is disposed on the light emission end face provided with the antireflection film 41, and the ends of the stripe waveguides 12, 22, 32 are separated from the end face provided with the antireflection film. It is preferable.
Here, the lengths of the light emitting regions provided in the stripe waveguides 12, 22, and 32 can be set to be different from each other. For example, the length from the tip of the stripe waveguide 2 to the end of the stripe waveguide 12 is set. Is L1, the length from the tip of the stripe waveguide 2 to the end of the stripe waveguide 22 is L2, and the length from the tip of the stripe waveguide 2 to the end of the stripe waveguide 32 is L3 (L1 ≠ L2 ≠ L3). can do. The widths of the stripe waveguides 2, 12, 22, and 32 can be set so that the single mode is maintained.
Then, by setting the lengths of the light emitting regions provided in the stripe waveguides 12, 22, and 32 to be different from each other, the peak wavelengths of the light generated in the stripe waveguides 12, 22, and 32 are made different from each other. be able to.

  FIG. 2 is a diagram showing spectral characteristics of stripe waveguides having different light emitting region lengths. In the example of FIG. 2, the length L1 from the tip of the stripe waveguide 2 to the end of the stripe waveguide 12 is 1.5 mm, and the length L2 from the tip of the stripe waveguide 2 to the end of the stripe waveguide 22 is L2 = The length from the front end of the stripe waveguide 2 to the end of the stripe waveguide 32 was 1.2 mm, and L3 = 0.9 mm. Further, the structures other than the length of the stripe waveguides 12, 22, and 32 are the same, and in the light emitting region of each of the stripe waveguides 12, 22, and 32, an active layer having five quantum wells is formed and each stripe waveguide is formed. The widths of the waveguides 12, 22, and 32 are also the same.

In FIG. 2, it can be seen that the peak wavelength of the light becomes longer as the length of the stripe waveguides 12, 22, 32 becomes longer.
Then, currents are injected into the stripe waveguides 12, 22, and 32 through the electrodes 13, 23, and 33, respectively, whereby light having different peak wavelengths is generated in the stripe waveguides 12, 22, and 32. The light having different peak wavelengths generated by the stripe waveguides 12, 22, and 32 is combined in the stripe waveguide 2, and the combined light is emitted to the outside from the light emission end face of the stripe waveguide 2. Is done.

  As a result, it is possible to change the peak wavelength of the spectrum by changing the length of the light emitting regions of the stripe waveguides 12, 22, and 32, and combine the light having different peak wavelengths in the stripe waveguide 2. Can be waved. For this reason, it is possible to increase the bandwidth of the light emitting diode by changing the shape of the stripe waveguides 2, 12, 22, and 32 when forming the pattern. There is no need to provide a quantum well structure in the optical waveguide or to form semiconductor layers having different band gaps along the light propagation direction. As a result, it is possible to increase the bandwidth of the light-emitting diode while suppressing complication of the manufacturing process, and to improve the manufacturing yield.

  Further, by electrically separating the electrodes 13, 23, and 33 for injecting current into the stripe waveguides 12, 22, and 32, respectively, the amount of current during operation is adjusted for each of the stripe waveguides 12, 22, and 32. Thus, the spectrum shape can be adjusted while widening the bandwidth of the light emitting diode. Therefore, even when the light emitting diode has a wide band, an ideal Gaussian spectrum shape can be obtained, and a single-peak autocorrelation function can be obtained while preventing the occurrence of side ropes. As a result, it is possible to prevent a ghost or the like from occurring in the observation image, and the light emitting diode can be easily applied to fields such as biological light observation.

  Further, by separating the ends of the stripe waveguides 12, 22, and 32 from the end face provided with the antireflection film 42, it is possible to suppress the end face reflection at the ends of the stripe waveguides 12, 22, and 32, thereby reducing the stripes. It is possible to suppress the resonance action of the light guided through the waveguides 12, 22, and 32 and to prevent laser oscillation in high output operation. For this reason, it is possible to reduce the coherence while enabling the operation in a wide spectrum band, and to suppress the generation of interference noise of the light-emitting diode, so that it can be widely used as a light source for optical measurement.

Further, by forming the antireflection films 41 and 42 on the both end faces of the substrate 1 provided with the stripe waveguides 12, 22, and 32, respectively, the reflectivity at both end faces of the substrate 1 can be reduced, and ripples can be reduced. Occurrence can be suppressed.
In addition, a window structure or an oblique stripe structure may be used, which makes it possible to reduce the end face reflectivity and improve the manufacturing yield. In addition to the method of using a window structure on the rear end face of each branched stripe waveguide 12, 22, 32, an antireflection film may be formed on the rear end face of each stripe waveguide 12, 22, 32. Good.

FIG. 3 is a diagram showing a spectral characteristic of light emitted from the stripe waveguide 2 of FIG. In the example of FIG. 3, the current value injected into the stripe waveguides 2 and 12 through the electrode 13 is 10 mA, the current value injected into the stripe waveguide 22 through the electrode 23 is 100 mA, and through the electrode 33. The current value injected into the stripe waveguide 32 was 160 mA.
In FIG. 3, a high output of 20 mW or more was obtained as an output of the light emitting diode, and a low ripple characteristic having a maximum pp ripple of 0.5 dB or less was shown. In addition, the half width of the conventional super luminescent diode is about 60 nm, whereas the half width of the light emitting diode having the configuration shown in FIG. 1 is about 90 nm, indicating a broadband characteristic.
In the embodiment of FIG. 1, the method of providing the stripe waveguides 12, 22, 33 having different lengths branched from the stripe waveguide 2 in order to increase the bandwidth of the light emitting diode has been described. You may make it provide the bending waveguide from which the length branched on the way differs.

4 is a cross-sectional view showing a specific configuration example when the light emitting diode of FIG. 1 is cut along the line AA ′, and FIG. 5 is a view when the light emitting diode of FIG. 1 is cut along the line BB ′. It is sectional drawing which shows the specific structural example.
4 and 5, an n-InP clad layer 52 is stacked on an n-InP substrate 51, and the stripe waveguides 2, 12, 22, and 32 of FIG. 1 are formed on the n-InP clad layer 52. GaInAsP-based active layers 5, 15, 25, and 35 are formed so as to correspond to the arrangement positions. That is, on the n-InP substrate 51, GaInAsP-based active layers 5, 15, 25, and 35 are formed in stripes so that the GaInAsP-based active layers 15, 25, and 35 are branched from the GaInAsP-based active layer 5, respectively. Has been. The lengths of the GaInAsP-based active layers 15, 25, and 35 are set to be different from each other. The structure of the GaInAsP-based active layers 15, 25, and 35 may be a multilayer quantum well structure, a multilayer strained quantum well structure, a quantum wire, or a quantum dot in addition to the bulk.

  Then, a mesa stripe waveguide structure is formed by sequentially embedding both sides of the GaInAsP-based active layers 5, 15, 25 and 35 with the p-InP buried layer 53 and the n-InP buried layer 54, and the n-InP buried layer is formed. 54 and the GaInAsP-based active layers 5, 15, 25, and 35, a p-InP clad layer 55 is formed. Instead of embedding the GaInAsP-based active layers 5, 15, 25, 35 in the p-InP buried layer 53 and the n-InP buried layer 54, the GaInAsP-based active layers 5, 15 are made of Fe-doped InP. , 25 and 35 may be embedded.

  On the p-InP clad layer 55, electrodes 13, 23, and 33 for injecting current into the stripe waveguides 2, 12, 22, and 32 are formed. Here, the electrode 13 can be disposed on the stripe waveguides 2 and 12, the electrode 23 can be disposed on the stripe waveguide 22, and the electrode 33 can be disposed on the stripe waveguide 32. The electrodes 13, 23, and 33 can be electrically separated from each other. In the p-InP buried layer 53, the n-InP buried layer 54, and the p-InP clad layer 55, the isolation groove 6 disposed between the GaInAsP-based active layers 15, 25, and 35 is formed. Note that an insulator such as a resin may be embedded in the separation groove 6.

  Here, when manufacturing the light emitting diode of FIGS. 4 and 5, the n-InP cladding layer 52 and the GaInAsP-based active layer are sequentially epitaxially grown on the n-InP substrate 51. As the epitaxial growth, for example, a method such as MBE (Molecular Beam Epitaxy), MOCVD (Metal Organic Chemical Vapor Deposition), or ALCVD (Atomic Layer Chemical Vapor Deposition) can be used.

Then, by a method such as CVD, forming a SiO ₂ film on the GaInAsP-based active layer, by processing the SiO ₂ film using photolithography and etching, the SiO ₂ film stripe waveguide 2,12 , 22 and 32. The GaInAsP-based active layer is etched using the SiO ₂ film patterned in the shape of the stripe waveguides 2, 12, 22, and 32 as a mask, thereby corresponding to the shapes of the stripe waveguides 2, 12, 22, and 32. The GaInAsP-based active layers 5, 15, 25, and 35 are formed.

Then, the p-InP buried layer 53 and the n-InP buried layer 54 are sequentially epitaxially grown on the n-InP substrate 51 using the SiO ₂ film patterned in the shape of the stripe waveguides 2, 12, 22, 32 as a mask. Thus, the p-InP buried layer 53 and the n-InP buried layer 54 are selectively formed on both sides of the GaInAsP-based active layers 5, 15, 25, 35.

  Next, a p-InP cladding layer 55 is formed on the n-InP buried layer 54 and the GaInAsP-based active layers 5, 15, 25, 35 by epitaxial growth. Note that a contact layer may be formed on the p-InP cladding layer 55. Then, the p-InP buried layer 53, the n-InP buried layer 54, and the p-InP clad layer 55 are etched using a photolithography technique and an etching technique, thereby forming a gap between the GaInAsP-based active layers 15, 25, and 35. The separation groove 6 disposed in the is formed. Then, a metal film is formed on the p-InP clad layer 55 by a method such as sputtering. Then, the electrodes 13, 23, and 33 are formed on the p-InP clad layer 55 by performing etching of the metal film using photolithography technology and etching technology.

Thus, by etching the GaInAsP-based active layer using the SiO ₂ film formed on the GaInAsP-based active layer as a mask, the lengths of the GaInAsP-based active layers 15, 25, and 35 are different from each other. A branched optical waveguide can be formed on the semiconductor substrate, and the peak wavelengths of the light spectra generated in the GaInAsP-based active layers 15, 25, and 35 can be made different from each other. Therefore, it is possible to increase the bandwidth of the light-emitting diode without providing a multilayer strained quantum well structure in the GaInAsP-based active layers 15, 25, and 35 and forming semiconductor layers having different band gaps along the light propagation direction. Therefore, the manufacturing yield can be improved.

  In the above-described embodiment, the method for forming a light emitting diode using an InP / GaInAsP-based material has been described. The semiconductor material may be used. In the above-described embodiment, the method using the mesa stripe waveguide structure as the stripe waveguides 2, 12, 22, and 32 has been described. However, in addition to the mesa stripe waveguide structure, the rib waveguide structure and the ridge waveguide are used. A structure or a strip-loaded waveguide structure may be used.

FIG. 6 is a plan view showing a schematic configuration of the light emitting diode according to the second embodiment of the present invention.
In FIG. 6, a stripe waveguide 102, stripe waveguides 112 and 122 branched from the stripe waveguide 102, and a stripe waveguide 132 branched from the stripe waveguide 122 are provided on a substrate 101. Here, each stripe waveguide 102, 112, 122, 132 is provided with an active layer that emits light. An electrode 113 for injecting current into an active layer provided in the stripe waveguides 102 and 112 is disposed on the striped waveguides 102 and 112, and provided on the stripe waveguide 122 on the stripe waveguide 122. An electrode 123 for injecting current into the active layer is disposed, and an electrode 133 for injecting current into the active layer provided in the stripe waveguide 132 is disposed on the stripe waveguide 123. Antireflection films 141 and 142 are formed on both end surfaces of the substrate 101 on which the stripe waveguides 102, 112, 122, and 132 are provided.

  Here, the lengths of the light emitting regions provided in the stripe waveguides 112, 122, and 132 can be set to be different from each other. Then, by setting the lengths of the light emitting regions provided in the stripe waveguides 112, 122, and 132 to be different from each other, the peak wavelengths of the light generated in the stripe waveguides 112, 122, and 132 are made different from each other. be able to.

  Then, by injecting current into the stripe waveguides 112, 122, 132 through the electrodes 113, 123, 133, light having different peak wavelengths is generated in the stripe waveguides 112, 122, 132, respectively. Then, light having different peak wavelengths generated by the stripe waveguides 122 and 132 is multiplexed by the stripe waveguide 122, and light having different peak wavelengths generated by the stripe waveguides 112, 122, and 132 is strip-guided. It is multiplexed by the waveguide 102. The combined light is emitted from the light emission end face of the stripe waveguide 102 to the outside.

  As a result, the number of branches of the stripe waveguides 112, 122, 132 can be easily increased, and the number of the stripe waveguides 112, 122, 132 branched so that the lengths of the light emitting regions are different from each other can be easily obtained. It can be increased. For this reason, it is possible to increase the bandwidth of the light emitting diode while suppressing the complexity of the manufacturing process.

  The light-emitting diode of the present invention can be used as a light source such as a white light source, an optical fiber gyroscope, and a high-resolution OTDR, and is applied to fields such as a multi-wavelength light source for wavelength division multiplexing optical communication networks, optical sensing, and biological light observation. be able to.

It is a top view which shows schematic structure of the light emitting diode which concerns on 1st Embodiment of this invention. It is a figure which shows the spectral characteristic of the stripe waveguide from which the length of a light emission area | region differs mutually. It is a figure which shows the spectral characteristic of the light radiate | emitted from the stripe waveguide 2 of FIG. It is sectional drawing which shows the specific structural example when the light emitting diode of FIG. 1 is cut | disconnected by the AA 'line. It is sectional drawing which shows the specific structural example when the light emitting diode of FIG. 1 is cut | disconnected by the BB 'line | wire. It is a top view which shows schematic structure of the light emitting diode which concerns on 2nd Embodiment of this invention.

Explanation of symbols

1, 101 Substrate 2, 12, 22, 32, 102, 112, 122, 132 Striped waveguide 13, 23, 33, 113, 123, 133 Electrode 41, 42, 141, 142 Antireflection film 5, 15, 25, 35 GaInAsP-based active layer 51 n-InP substrate 52 n-InP clad layer 53 p-InP buried layer 54 n-InP buried layer 55 p-InP clad layer 6 Separation groove

Claims (10)

  A light-emitting diode, characterized in that an optical waveguide branched in the middle is provided so that the lengths of the light-emitting regions are different from each other.   The light emitting diode according to claim 1, further comprising an electrode for individually injecting a current into each of the branched optical waveguides.   The light-emitting diode according to claim 1, wherein branch points are provided at a plurality of locations of the optical waveguide.   4. The light emitting diode according to claim 1, wherein a terminal end of the branched optical waveguide is separated from an end face. 5. The optical waveguide is
A first optical waveguide provided with an active layer;
5. The light-emitting diode according to claim 1, further comprising: a second optical waveguide branched from the first optical waveguide, wherein the active layers have different lengths. . A first electrode for injecting a current into the first optical waveguide;
6. The light emitting diode according to claim 5, further comprising: a second electrode that is electrically separated from the first electrode and injects a current into the second optical waveguide.   The light emitting diode according to claim 5 or 6, wherein the first active layer and the second active layer have a stripe structure. A lower cladding layer formed on a semiconductor substrate;
An active layer formed on the lower cladding layer and having a plurality of stripe structures branched in the middle so that the lengths differ from each other;
A buried layer filling both sides of the active layer;
A light emitting diode comprising: the active layer; and an upper clad layer formed on the buried layer. Forming a lower clad layer on the semiconductor substrate by epitaxial growth;
Forming an active layer on the lower cladding layer by epitaxial growth;
Forming an oxide film on the active layer;
Patterning the oxide film so as to have a plurality of stripe shapes branched in the middle so that the lengths differ from each other;
Etching the active layer using the oxide film as a mask, patterning the active layer to have a plurality of stripe shapes branched in the middle so that the lengths are different from each other;
Selectively forming buried layers disposed on both sides of the active layer by performing epitaxial growth using the oxide film as a mask;
And a step of forming an upper clad layer on the active layer and the buried layer. Forming a conductive film on the upper clad layer;
The method for manufacturing a light emitting diode according to claim 9, further comprising: forming electrodes electrically separated from each other for each stripe by patterning the conductive film.

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