JP3148154B2 - Method of manufacturing surface emitting laser and surface emitting laser manufactured by the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a surface emitting laser having high luminous efficiency and high reliability, and a surface emitting laser manufactured by the method.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a surface emitting laser according to the related art.
FIG. 4 is a sectional structural view of the vertical cavity surface emitting laser of FIG.
FIG. 3 is a process flow diagram of a surface emitting laser. These are examples
For example, Electronics Letters by chocket
Vol. 30, pages 2043-2044, 1994 (K.D. Choquett
e etal., Electronics Letters Vol. 30, 2043-2044 (1
994).). Structure according to the manufacturing method below
Will be described. On the n-type GaAs substrate 1, the wavelength in the medium is
λ, a GaAs layer having a thickness of １ ／ λ (high refractive index
Layer) and 1 / 4λ thick Al_0.9 Ga_0.1 As layer (low bending
N-type semiconductor multilayer reflective film in which 38 layers are alternately laminated.
Form 2 N-type Al_0.3 Ga _0.7 As Kula
Head layer 3, i-In_0.2 Ga_0.8 As layer was used as well layer
Active layer 4, p-type Al_0.3 Ga_0.7 Form As clad layer 5
Long, then Al_0.9 Ga_0.1 1 / 4λ starting from the As layer
Thickness of Al_0.9 Ga_0.1 As layer (low refractive index layer) and 1 /
GaAs layer (high refractive index layer) with a thickness of 4λ is laminated for 25 periods
The p-type semiconductor multilayer reflective film 6 is sequentially grown. that time,
Later, the current confinement of the device and the confinement of light are performed by oxidation of Al.
In order to perform the operation, the lowest low refraction of the p-type semiconductor multilayer reflective film 6 is required.
Al as the rate layer_0.9 Ga_0.1 Reduced Ga composition in As layer
Al_0.98Ga_0.02The As oxide layer 8 is formed. That's all
Thus, the surface emitting laser substrate 7 is manufactured. These components
Length is for metal organic chemical vapor deposition (MOVPE)
Perform by law.

In order to obtain laser oscillation in such a vertical cavity surface emitting laser, the current is confined near the active layer, and in order to obtain a single fundamental transverse mode oscillation, the active region has a depth near the active layer. It is necessary to increase the resistance of the peripheral portion of the substrate, but as a method thereof, ion implantation for implanting protons and oxidation of Al are generally used. Regarding the ion implantation, the current can be narrowed because the ion implantation region has a sufficiently high resistance. However, since the change in the refractive index due to the implantation is small, the confinement of light is small. Therefore, light spreads in a direction parallel to the layer, and the loss is large. Therefore, current constriction due to oxidation of Al is performed by the following method.

First, a mask 9 of 105 μm square made of SiN is formed on a surface emitting laser substrate 7, and a mesa 10 is formed by performing wet etching until reaching a n-type semiconductor multilayer film. Thereafter, the element is heated to 425 ° C. in a nitrogen atmosphere, and steam is introduced using an inert gas such as nitrogen as a carrier gas. Since the oxidation rate by Al ratio for AlGaAs largely changed, compared to the Al _0.9 Ga _0.1 As layer constituting the semiconductor multilayer reflection film Al _0.98 Ga _0.02 A
The oxidation rate of the layer 8 is as large as about 15 times, and Al _0.98 Ga
Only the _0.02 As layer 8 is selectively oxidized from the side of the mesa and A
l ₂ O ₃ 11 The light emitting region is oxidized for about 6 hours to about 10 μmφ, and the unoxidized central portion becomes the light emitting region 12. Thereafter, the SiN mask 9 is peeled off, an n-type electrode 21 of AuGeNi is formed on the etched bottom surface, and a p-type electrode of TiAu is formed on the mesa.
A mold electrode 22 is formed. Then, the back surface of the substrate is 100 μm
The mirror is polished to a thickness of about the same, and further mirror-polished, and an anti-reflection coating 23 is applied as necessary to complete the element.

[0005]

In the above-described surface emitting laser, the refractive index is greatly reduced from 3.5 to about 1.7 due to oxidation of the AlGaAs layer, so that light is almost completely confined. . However, since the thickness of the AlGaAs layer increases due to oxidation, the thickness of one layer is partially different, and the structure becomes very weak, and long-term reliability cannot be obtained. The oxidation of Al is generally performed in steam, but it is very difficult to obtain reproducibility and uniformity in this process. Further, in order to selectively oxidize only the AlGaAs layer near the active layer, G in the composition of the AlGaAs layer, which is a low refractive index layer constituting the semiconductor multilayer reflective film, which is another part that is not oxidized, is used.
Although the a-ratio is increased, the reflectance per one cycle decreases. Therefore, in order to obtain a sufficient reflectance, the number of cycles must be increased, and the man-hour required for crystal growth increases. In addition, since the light absorption increases, a high reflectance cannot be obtained. As a result, there is a problem that the optical characteristics are deteriorated such as an increase in the oscillation threshold current.

An object of the present invention is to provide a novel method of manufacturing a surface emitting laser which has solved the above-mentioned problems and a surface emitting laser manufactured by the method.

[0007]

The above object is achieved by the following means.

That is, according to the present invention, after a first conductive type semiconductor multilayer reflective film, a first conductive type clad layer, an active layer, a second conductive type clad layer and an adhesive layer are grown on a first conductive type substrate, Etching the adhesive layer while leaving the region of the element, growing the second conductive type semiconductor layer reflective film and the adhesive layer on another semi-insulating substrate, and contacting the adhesive layers of both substrates with each other in a hydrogen atmosphere. Heating the two substrates together while applying pressure therein, removing the semi-insulating substrate by etching the semi-insulating substrate side until reaching the second conductive type semiconductor multilayer film, and removing the exposed second conductive type. Forming a mask sufficiently larger than the element part on the upper surface of the type semiconductor multilayer reflective film, performing ion implantation or etching using the mask to ensure insulation to the adjacent element, and using the back surface or etching etc. 1st conductivity type The present invention proposes a method for manufacturing a surface emitting laser, characterized by using a step of exposing a conductive multilayer film to form an electrode thereon and forming an electrode on a second conductive type semiconductor multilayer reflective film. And a surface emitting laser manufactured by the above method.

According to the surface emitting laser of the present invention, in order to form a space in the vicinity of the active layer, it is electrically completely confined, and the refractive index difference is between GaAs (3.4) and air (1.
0), the light is almost completely confined optically. Moreover, since no distortion occurs in a mere space, it is structurally strong and has excellent long-term reliability. Further, since the range of the current constriction is determined by the size of the mesa, reproducibility and controllability are good. Further, unlike the selective oxidation of the AlGaAs layer, the Ga ratio of the AlGaAs layer, which is a low refractive index layer in the semiconductor multilayer film, can be reduced, so that a sufficient reflectance can be obtained with a small number of periods, and the number of steps required for the growth is reduced. And a structure having good optical characteristics can be manufactured. As a result, a surface emitting laser with high reliability and good optical characteristics can be realized. As the first conductivity type substrate and the semi-insulating substrate, GaAs or InP can be used.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

[0011]

FIG. 1 is a structural view of the present device, and FIG. 2 is a process flow diagram of the present device. The structure will be described below according to the manufacturing method.

First, when the wavelength in the medium is λ, the GaAs layer having a thickness of ４λ is placed on the n-type GaAs substrate 1.
The n-type semiconductor multilayer reflective film 2 is formed by alternately stacking 20 AlAs layers each having a thickness of / 4λ. N-type Al _0.3
A Ga _0.7 As clad layer 3, an active layer 4 with an i-Al _0.2 Ga _0.8 As layer as a barrier, an i-In _0.2 Ga _0.8 As layer as a well layer, and a p-type Al _0.3 Ga _0.7 As clad layer 5 are grown.
Further, GaAs having a thickness of 5 / 4λ is used as the first adhesive layer 31.
Grow the s layer. At this time, in order to satisfy the optical reflection condition, the thickness of the first adhesive layer 31 is set to an odd multiple of ４λ.
These are grown, for example, by metal organic chemical vapor deposition (MOVP).
E) or the like. Next, a mask 32 having a donut-shaped opening having an inner diameter of 6 μmφ and an outer diameter of 50 μmφ is formed on the first adhesive layer 31 by a photolithography method or the like.
Using the mask, the first adhesive layer 31 is formed into p-type Al _0.3 Ga
_The mesa 33 is formed by performing wet etching to a depth that does not reach the _0.7 As clad layer 5.

Next, on another semi-insulating GaAs substrate 34, 1
A p-GaAs layer having a thickness of ４λ and a p-GaAs layer having a thickness of ４λ
A p-type semiconductor multilayer reflective film 35 in which AlAs layers are alternately stacked for 15.5 periods is grown. The surface of this substrate ends with a GaAs layer, and the GaAs layer becomes the second adhesive layer 36. Thereafter, the first adhesive layer 32 and the second adhesive layer 36 of both substrates are formed.
And pressurize the contact portion in a hydrogen atmosphere while
The substrate is bonded by increasing the temperature to about 0 ° C. Further, the semi-insulating substrate 34 is removed by etching the entire surface until the semi-insulating substrate reaches the p-type semiconductor multilayer film 35. On the exposed top surface of the p-type semiconductor multilayer reflective film 35, the inner diameter of the mask 32 is larger than the inner diameter and smaller than the outer diameter of 40 μm.
A mask 37 having a size of φ is formed, protons are implanted under the condition of 300 keV and 5 × 10 ¹⁴ cm ⁻² using the mask 37 to form a high-resistance region 38, and an insulating property to an adjacent element is formed. To secure. Further, a part of the wafer is etched until it reaches the n-type semiconductor multilayer reflective film 2 to form an n-type electrode 21 made of AuGeNi on the exposed n-type semiconductor multilayer reflective film 2. A p-type electrode 24 made of TiPtAu is formed thereon, and a heat treatment is performed at 400 ° C. for about 30 seconds in order to obtain ohmic properties. Further, the back surface is mirror-polished, and an anti-reflection coat 23 is applied to the back surface as needed.

[0014]

As described above, according to the present invention,
In order to form a space in the vicinity of the active layer, the space is completely confined electrically, and the refractive index difference is large between GaAs (3.4) and air (1.0). Completely constricted. In addition, since no distortion occurs in a mere space, the structure is strong and no distortion occurs, and high reliability is maintained. Further, since the range of the current constriction is determined by the size of the mesa, reproducibility and controllability are good. Further, unlike the selective oxidation of the AlAs layer, the AlAs / GaAs G
Since the a ratio can be kept constant, a sufficient reflectance can be obtained with a small number of periods, a man-hour required for growth is small, and a structure having good optical characteristics can be manufactured. Further, since the surfaces to be bonded are the same crystal and the lattice constant of the crystal is the same, the crystal is not distorted by the bonding and the reliability is not impaired. As a result, a surface emitting laser with a low oscillation threshold current can be realized.

[Brief description of the drawings]

FIG. 1 is a structural diagram of an element of the present invention.

FIG. 2 is a process flow chart of the device of the present invention.

FIG. 3 is a cross-sectional view of a conventional device.

FIG. 4 is a process flow chart of a conventional device.

[Explanation of symbols]

Reference Signs List 1 n-type GaAs substrate 2 n-type semiconductor multilayer reflection film 3 n-type Al _0.3 Ga _0.7 As cladding layer 4 active layer 5 p-type Al _0.3 Ga _0.7 As cladding layer 6 p-type semiconductor multilayer reflection film 7 surface emitting laser substrate 8 Al _0.98 Ga _0.02 As oxide layer 9 SiN mask 10 Mesa 11 Al ₂ O ₃ 12 Light emitting area 21 n-type electrode 22 p-type electrode 23 anti-reflection coat 24 P-type electrode 31 first adhesive layer 32 mask 33 mesa 34 semi-insulating GaAs substrate 35 p-type semiconductor multilayer reflective film 36 second adhesive layer 37 mask 38 high resistance region

Claims (2)

(57) [Claims] 1. A first conductive type semiconductor multilayer reflective film, a first conductive type clad layer, an active layer, a second conductive type clad layer, and an adhesive layer are grown on a first conductive type substrate. Etching, leaving a second conductive type semiconductor layer reflective film and an adhesive layer on another semi-insulating substrate, and contacting the adhesive layers of the two substrates with each other to apply pressure in a hydrogen atmosphere. Bonding the two substrates by heating while heating, removing the semi-insulating substrate by etching the semi-insulating substrate side to reach the second conductive type semiconductor multilayer film, and exposing the exposed second conductive type semiconductor multilayer reflection. Forming a mask sufficiently larger than the element portion on the upper surface of the film, performing ion implantation or etching using the mask to ensure insulation to adjacent elements, and forming the first conductivity type on the back surface or by etching. Exposed semiconductor multilayer And manufacturing an electrode on the second conductive type semiconductor multilayer reflective film. 2. A surface emitting laser manufactured by the method according to claim 1.