JPH0328077B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a surface-emitting laser device that emits oscillation output light by a pn stripe structure formed on a semiconductor substrate at right angles to the semiconductor substrate, and a method for manufacturing the same, and in particular, This is a highly efficient surface-emitting laser element that can be easily manufactured and is capable of reducing the oscillation current threshold by confinement, controlling the transverse mode, and achieving a single longitudinal mode.

(Prior art) This kind of conventional surface-emitting type radiation device is, for example,
They are constructed as shown in FIGS. 3a to 3d, respectively, and in each case, the orientation of the horizontal and vertical spread of the drive current or output light with respect to the wafer surface,
That is, there is a drawback in that it is difficult to control and unify the transverse mode and the longitudinal mode, and sufficient performance cannot be obtained.

For example, in the conventional element having the configuration shown in FIG. 3a, the current 19
Since the lateral spread of 0 is restricted, a significant spread of current occurs in the active region 180, which limits the ability to increase the efficiency of laser light by reducing the current threshold. The transverse mode control of the output light cannot be sufficiently controlled only by suppressing the light intensity, and therefore it is necessary to separately provide a current confinement structure and an optical waveguide structure.

As an example, a conventional element having a lateral junction structure as shown in FIG. 3b has been considered. That is,
For example, the same n-type InP cladding layer 30,
A GaInAsP active layer 40 and an InP layer 50 are laminated, and a Zn diffusion region 200 is provided in the lateral half of the laminated structure to form a P type, and a mirror layer 1 is formed on the same upper surface.
10, a P-side electrode layer 120 and an n-side electrode layer 14.
A surface-emitting laser device has been considered in which the lateral current 190 can be controlled by providing The controllability of the transverse mode was insufficient. In addition, as shown in FIG. 3c, the Pn junction stacked structure centered on the active layer 40 is etched to the middle of the cladding layer 30 to form a circular or rectangular mesa shape, and then the surrounding area is filled with pnpn multilayer InP stripes. In conventional devices with a structure surrounded by layers, a current confinement structure and an output optical waveguide structure exist in the active region.
Since the constriction structure and the waveguide structure do not act on the cladding region, even with such multilayer embedding, the transverse mode controllability was insufficient.
In addition, as shown in FIG. 3d, an insulating material film 100 is provided on the inner wall surface of the recess surrounding the active region of the circular or rectangular mesa structure similar to that described above, and the mesa-shaped active region is covered with the insulating film 100. In the conventional device with the enclosed structure, current confinement and output optical waveguide structure are achieved, but the cross-sectional area of the mesa needs to be reduced in order to lower the current threshold and improve efficiency. , it is necessary to use a metal material layer with a small area as both the mirror 110 and the electrode 120 on the P side.
Various problems such as difficulty in increasing the reflectance of the side mirror 110, a decrease in the mechanical strength of the mesa structure, and a deterioration in heat dissipation properties occurred, making it impossible to obtain sufficient performance.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned conventional drawbacks, and skillfully combine the advantages of various conventional current confinement structures to reduce the current threshold, control the transverse mode, and unify the transverse mode. It is an object of the present invention to provide a surface-emitting laser element that is easily manufactured and has good heat dissipation properties and high reflectance, and a method for manufacturing the same.

(Structure of the Invention) In other words, the surface-emitting laser device of the present invention cleverly combines current confinement by the conventional stripe structure and current confinement by the mesa structure to confine both current and light, thereby reducing the current threshold. In addition, it is possible to control the transverse mode and unify the longitudinal mode. a lower electrode layer, an etching stop layer made of a semiconductor material of the same conductivity type as the semiconductor substrate and deposited on the semiconductor substrate with an opening having the same shape as the opening, and an etching stop layer formed on the etching stop layer. a cladding layer made of a semiconductor material of the same conductivity type as the semiconductor substrate deposited to cover the opening; a lower mirror layer deposited on the lower surface of the cladding layer filling the opening; and a part of the cladding layer. and an active layer including a semiconductor material having a conductivity type opposite to that of the semiconductor substrate is located as a central layer facing the opening and the opening.
A rectangular mesa structure consisting of a pn stripe, and a recess along one direction of the rectangle formed by the mesa structure are provided sandwiching the rectangular mesa structure, and the semiconductor substrate is of a conductivity type opposite to that of the semiconductor substrate that covers at least the rectangular mesa structure. a p-n plane buried current confinement structure deposited on the cladding layer with a semiconductor material layer as the top layer;
A cap layer made of a highly concentrated semiconductor material of a conductivity type opposite to that of the semiconductor substrate is deposited on the pn plane buried current confinement structure, and an upper mirror layer is deposited on the cap layer facing the square mesa structure. and,
It is characterized by comprising an upper electrode layer surrounding the upper mirror layer and deposited on the cap layer.

(Example) The present invention will be described in detail below with reference to the drawings.

Therefore, for the convenience of explanation to facilitate understanding of the features of the present invention, an example of the manufacturing process of the surface-emitting laser device of the present invention will first be shown in detail in FIGS. 1a to 1h. Describe.

That is, in manufacturing the laser device of the present invention, first, as shown in FIG.
On the InP substrate 10, liquid phase epitaxial (LPE)
growth method, metal organic chemical deposition (MOCVD) growth method,
By crystal growth methods such as molecular beam epitaxial (MBE) growth, n-type
Following the etching stop layer 20 made of GaInAsP material, a cladding layer 3 made of n-type InP material
An active layer 40 and a P-type InP layer 50 made of a 0.0, p-type GaInAsP material are sequentially grown, and a pn junction layer having a short resonator is laminated. Next, the deposited layer is etched to the middle of the n-type InP cladding layer 30 by chemical etching, as shown in FIG. 1b, to form a plurality of rectangular mesas scattered in a suitable matrix on the substrate 10. do. Then,
Between the plurality of rectangular mesa groups scattered in a matrix, p-type InP layers 60 and n-type InP layers 70 are alternately stacked and buried in a plane, as shown in FIGS. In addition, Figure 1c shows the state of pnp embedding, the rare figure shows the state of pnpn multilayer embedding, and the same figure shows the state of p embedding.
The more complex the laminated structure is, the easier it becomes to control the current confinement in the mesa due to such embedding. Next, a p-type InP layer 60, which is the top layer of the planar embedding applied to the square mesa group, is coated with a p-type InP layer 60 to reduce ohmic resistance due to contact with the electrode layer.
A cap layer 80 of GaInAsP material is grown. Next, as shown in Fig. 1d, chemical etching is applied along one direction of the matrix between the mesa groups arranged in a matrix, leaving buried stripes of several micrometers at the front and back of each square mesa, and recesses are formed. A section 90 is formed. Such a recessed part 9
0 depth is the n-type InP cladding layer 3 as shown in the cross-sectional view of FIG. 1d along line A-A'.
0, so as not to reach the n-type GaInAsP etching stop layer 20. A part B of the recessed notch 90 shown in FIG. 1d is shown in an enlarged manner in the same figure. Note that the illustrated structure is an example in which PNP embedding is performed. Next, as shown in FIG. 1e, for example, the inner wall surface of each recessed notch 90 is
An insulating film 100 made of a material such as SiO ₂ or Si ₃ N ₄ is deposited to prevent chemical reactions from occurring on the semiconductor material appearing on the etched surface of the recess, especially on the exposed surface of the semiconductor material in the mesa. The recessed portions 90 may be flattened or filled with a synthetic resin material such as polyimide.

In the laminated structure formed as described above, the components necessary for functioning as a surface-emitting laser element are added to the rectangular mesa portion in which the active region that individually functions as a laser element exists, as follows. Form the adhesion.

That is, as shown in Figure 1f, the embedded pn
A high-reflectance mirror 110 made of a dielectric multilayer film, an Au thin film, etc. is deposited on the cap layer 80 in the rectangular mesa area surrounded by the stripe and the recessed part, and the buried pn stripe area is coated on the cap layer 80. On the cap layer 80 of
A p-side electrode layer 120 made of Zn, Au/Cr, Ti/Pt/AU, etc. is deposited. On the other hand, as shown in FIG. 1g, a circular or square hole 130 is formed in the back side of the above-described laminated structure on the substrate side, corresponding to the part of the square mesa where the active region is present. That is, by applying a selective etching method to the relevant portion, first, the substrate 10 is etched using an etching solution that corrodes only the n-type InP material constituting the substrate 10 and does not corrode the n-type GaInAsP material constituting the etching stop layer 20. After drilling a hole 130 with a desired shape and size, the etching solution is changed to etch away the etching stop layer 20 at the bottom of the hole, exposing the cladding layer 30. Then,
On the back side of the part other than the hole 130 on the board 10
N-side type layer 14 made of AU/Sn, AU/Ge, etc.
At the same time, on the n-type InP cladding layer 30 exposed at the bottom of the hole 130, a highly reflective layer made of a dielectric multilayer film, a thin Au film, etc. is deposited, similar to the mirror 110 provided on the surface side of the laminated structure. rate mirror 15
Deposit 0.

Figure 1h shows the laminated structure in which a large number of laser elements and a matrix are arranged as described above.
As shown in FIG. 2, a plurality of surface-emitting laser devices of the present invention are completed at once by cutting into individual chips centered on the square mesa portion. Note that Fig. 1h shows the P side of the laser element chip, and the same figure shows the n side.
Both are schematic perspective views shown facing upward, and the surface-emitting laser device of the present invention having a transverse mode control/current confinement structure is obtained by forming the above manufacturing process.

An example of the configuration of the surface-emitting laser device of the present invention formed by the manufacturing process as described above is shown in FIGS. 2a and 2a.
It is shown in Figure 2b. Note that FIG. 2a is a cross-sectional view of the chip shown in FIG. 1h along line A-A',
FIG. 2b is a cross-sectional view of the same chip taken along line B--B'. As is clear from the figure, in the surface emitting laser device of the present invention, the part of the rectangular mesa containing the active region is in the direction of line A-A'.
Due to the pn stripe buried layer, the line B-
In the direction B', both current and light are confined by the insulating material applied to the recess formed by chemical etching, and therefore the oscillation current and the oscillation output light are transmitted to the substrate surface. Both lateral mode control, which controls the attitude of the spread in the horizontal direction along the substrate, and longitudinal mode control, which controls the attitude of the spread in the direction perpendicular to the substrate surface, and unification, are set to the current threshold reduction limit as in the past. This can be achieved satisfactorily without causing problems such as difficulty in increasing the reflectance of the mirror layer, deterioration of heat dissipation properties, and reduction in strength of the mesa structure.

The operation of the surface-emitting laser device of the present invention is described in a second manner.
To explain the configuration example shown in FIG. 2A and FIG. The current flowing through is confined in the active region within the rectangular mesa surrounded by the pn stripe buried layer and the passivation film 100 on the inner wall surface of the recess 90.
A so-called population inversion, in which the distribution of atoms with respect to energy levels is inverted, is formed in the active layer 40, and excited laser light is generated. The generated laser light is also confined within a waveguide surrounded by the concave cutout 90, and is confined by a Fabry-Perot resonator consisting of mirrors 110 and 150 with high reflectivity located at the upper and lower ends of the waveguide, respectively. resonance 160
This causes laser oscillation. At this time, the threshold value of the current flowing inside the rectangular mesa is sufficiently reduced based on the current confinement effect by the pn stripe buried layers 60 and 70 and the passivation film 100 of the recessed part 90. Further, the output laser beam 170 exhibits a single longitudinal mode due to the short resonators stacked around the active layer 40, and the refractive index exhibited by the material of the passivation film 100 of the concave cutout 90 and the active region formed by the rectangular mesa. A transverse single mode is also possible due to the difference in the width of the active region and the width of the active region.

In addition, in the laser device of the present invention having the configuration shown in FIG. 2, a rectangular mesa is formed by etching the recessed portion 90 and the portions of its inner wall surface other than the passivation film 100 in the laminated structure as described above with reference to FIG. In addition to the manufacturing process that provides a current confinement structure by embedding pn stripes after formation, it is also possible to provide a built-in current confinement structure in a stacked semiconductor by appropriately selectively sequentially depositing the required deposited layers. It also has some structural advantages.

In addition, in the above explanation, we have described examples of the manufacturing process and element structure starting from an n-type InP substrate, but starting from a p-type InP substrate, the setting of p-type and n-type of each layer in the above explanation is also explained. Of course, by reversing each case, it is possible to form a laser device of the present invention having a completely similar device structure through a completely similar manufacturing process. In addition, the material of each layer is not limited to the above-mentioned example, for example,
The laser device of the present invention can be similarly formed using other suitable materials, such as using GaAs instead of InP.

(Effects) As is clear from the above description, according to the present invention, the pn stripe buried layer and the etched groove provided with passivation can effectively prevent the current flowing through the active region formed into a short cavity in a surface-emitting semiconductor laser device. It is possible to easily reduce the current threshold by narrowing the current, and also to enable sufficient transverse mode control to unify the transverse mode as well as the longitudinal mode. A surface-emitting laser device with improved performance can be easily manufactured. Therefore, according to the surface-emitting semiconductor laser device of the present invention, which can extract optical output perpendicularly to the wafer with a sufficiently narrow divergence angle, it is possible to convert it into a two-dimensional laser or integrate it with other semiconductor functional devices. can also be easily realized.

[Brief explanation of the drawing]

Figure 1a, Figure 1b, Figure 1c~, Figure 1d
Figures 1e to 1g and 1h are sectional views and perspective views sequentially showing examples of the manufacturing process of the surface-emitting laser device of the present invention, and Figures 2a and 2b are surface-emitting laser devices of the present invention. FIGS. 3a to 3d are cross-sectional views showing examples of the structure of a conventional surface-emitting laser device, respectively, in cross-sections in directions perpendicular to each other. FIGS. 10... n-type InP substrate, 20... n-type InP etching stop layer, 30... n-type InP cladding layer, 4
0...p-type GaInAsP active layer, 50...p-type InP
layer, 60... p-type InP buried layer, 70... n-type InP
Buried layer, 80... p-type GaInAsP cap layer, 9
0... Etching groove (concave cutout), 100... Passivation film, 110... P-side mirror layer, 12
0...p-side electrode layer, 130...hole, 140...n
Side electrode layer, 150... n-side mirror layer, 160...
Optical resonance path, 170... optical output, 180... active region, 190... current, 200... Zn diffusion region.

Claims (1)

[Claims] 1. A semiconductor substrate having a circular or rectangular opening, a lower electrode layer deposited on the lower surface of the semiconductor substrate excluding the opening, and an opening having the same shape as the opening. an etching stop layer made of a semiconductor material of the same conductivity type as the semiconductor substrate and deposited on the semiconductor substrate; and a semiconductor of the same conductivity type as the semiconductor substrate deposited on the etching stop layer to cover the opening. a lower mirror layer deposited on the lower surface of the cladding layer to fill the opening, and a semiconductor material that includes a part of the cladding layer and has a conductivity type opposite to that of the semiconductor substrate. A rectangular mesa structure with the active layer as a central layer and consisting of the aperture and a pn stripe located opposite to the aperture, and a recess along one direction of the rectangle formed by the mesa structure with the rectangular mesa structure sandwiched therebetween. a pn plane buried current confinement structure deposited on the cladding layer with a semiconductor material layer of a conductivity type opposite to that of the semiconductor substrate as the uppermost layer covering at least the square mesa structure; a cap layer made of a highly concentrated semiconductor material of a conductivity type opposite to that of the deposited semiconductor substrate; an upper mirror layer deposited on the cap layer facing the square mesa structure; and a cap layer surrounding the upper mirror layer. A surface emitting laser device comprising: an upper electrode layer deposited on the cap layer. 2. A surface-emitting laser device according to claim 1, wherein the inner wall surface of the recessed portion is covered with an insulating material film. 3. A surface-emitting laser device according to claim 1, wherein the recessed portion is filled with a synthetic resin material. 4. On a semiconductor substrate, an etching stop layer made of a semiconductor material of the same conductivity type as the semiconductor substrate and a cladding layer made of a semiconductor material of the same conductivity type as the semiconductor substrate are provided as the bottom layer, and the etching stop layer is of a conductivity type opposite to that of the semiconductor substrate. A growth process in which a pn stripe structure is sequentially grown and deposited with an active layer having a semiconductor material as a central layer, and the pn stripe structure is removed by chemical etching into the cladding layer and arranged in a matrix. multiple pn
A mesa formation process for forming a striped rectangular mesa structure, and at least a pn buried layer made of a semiconductor material layer of a conductivity type opposite to that of the semiconductor substrate, which covers the plurality of rectangular mesa structures, between the plurality of rectangular mesa structures. a planar embedding process in which the planar embedding layer is buried flatly; an ohmic resistance reduction process in which a cap layer made of a highly concentrated semiconductor material of a conductivity type opposite to that of the semiconductor substrate is grown and deposited on the planar embedding layer; and removing the cap layer into the cladding layer by chemical etching to form recesses along one direction of the matrix between the plurality of rectangular mesa structures; A current confinement process in which an insulating material film is applied to each inner wall surface or a synthetic resin material is filled in each of the recesses, and a plurality of insulating material films are applied on the cap layer facing each of the plurality of rectangular mesa structures. an upper resonant structure formation process of depositing a plurality of upper mirror layers and depositing an upper electrode layer on the cap layer surrounding each of the plurality of upper mirror layers, and selecting the semiconductor substrate and the etching stop layer. A plurality of holes and openings are formed in a circular or rectangular shape each facing the plurality of rectangular mesa structures by sequentially removing them from the bottom surface by etching, and a plurality of holes and openings are formed in the bottom surface of the cladding layer exposed in each of the openings. a lower resonant structure forming step of depositing a lower mirror layer of the plurality of rectangular mesas and a lower electrode layer on the lower surface of the semiconductor substrate excluding the openings; 1. A method for manufacturing a surface-emitting laser device, comprising a step of forming chips in which the chips are cut into pieces centering on each structure.