JPH06318760A - Surface light emission laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a surface light emission laser provided with an active layer having an area smaller than that of a reflecting mirror and a method of manufacturing the laser. CONSTITUTION:An upper reflecting mirror 16 is formed by dry etching and after a protective film is formed on the mirror 16, an active layer 20 and barrier layers 21 and 22 are subjected to dry etching. The layer 20 is side-etched by wet etching, whereby the layer 20 having an area smaller than that of the mirror 16 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and its manufacturing method, and more particularly to a surface emitting laser and its manufacturing method.

[0002]

2. Description of the Related Art Vertical cavity surface emitting lasers (Vertical-Ca
vity Surface-Emitting Laser (hereinafter referred to as surface emitting laser) operates with a low threshold current, has a wide emission area of laser light, and has a very narrow beam emission angle. Is being researched. The surface emitting laser is
It has a laser resonator formed in a direction perpendicular to the substrate and a laser reflecting mirror composed of a semiconductor crystal surface, and since laser light is emitted from the crystal surface, it is not necessary to cleave the semiconductor substrate. Such a structural feature improves the yield and makes it possible to perform an operation test of the surface emitting laser on a wafer-by-wafer basis before separating into individual devices. A two-dimensional laser array can be formed more easily.
Such a feature of the surface emitting laser has attracted a great deal of attention as a solution to some of the problems of the conventional edge emitting lasers.

FIGS. 8 (a) to 8 (d) are conventional surface-emitting devices.
The manufacturing method of the optical laser 300 is shown. Such a face
The method of manufacturing the light emitting laser 300 is, for example, IEEE Photonic.
Technology Letters, Vol. 3 (1991), pp. 9-11.
ing. First, as shown in FIG. 8A, n-Ga
A bottom reflector 312 and a spacer layer 30 on the As substrate 301.
4, active layer 305, spacer layer 306, and upper reflector
313 is epitaxially grown in order. Bottom reflector 3
12 is n-Al alternately deposited by several tens of layers _0.08Ga
_0.92As layer 302 and n-Al_0.6Ga_0.4As layer 303
The upper reflecting mirrors 313 are alternately deposited by several tens of layers.
P-Al_0.08Ga_0.92As layer 307 and p-Al_0.6
Ga_0.4It is composed of an As layer 308. In addition, the spacer layer 30
4, the active layer 305, and the spacer layer 306 are respectively
n-Al_0.35Ga_0.65As, p-GaAs, and p-A
l_0.35Ga_0.65It consists of As.

Next, as shown in FIGS. 8B and 8C, the upper reflecting mirror 313 and the spacer layer 306 are etched with a mixed solution of potassium dichromate, hydrogen bromide and acetic acid. , The active layer 305 is Clorox
Side etching is performed with a mixed liquid of water and water so that the area of the active layer 305 is smaller than the area of the spacer layer 306. Finally, as shown in FIG. 8D, the spacer layer 3
04, a polyimide film 309 is formed so that the surface of the upper reflecting mirror 313 is exposed, and an electrode 310 made of AuGe is formed.
And 311 to the substrate 301 and the upper reflecting mirror 313, respectively.
It is formed so as to be electrically connected to.

Conference on lasers and electro
-Optics 1991 in technical digest pp. 330-333 proposes an atomic layer bonding technique for bonding different substrates as a semiconductor laser manufacturing method. This technique will be described with reference to FIGS. 9A to 9C. As shown in FIG. 9A, n-InGaA is formed on the InP substrate 401.
s layer 402, n-InP layer 403, u-InGaAsP
The layer (λg = 1.3 μm) 404, the u-InGaAsP layer (λg = 1.5 μm) 405, and the p-InP layer 406.
Are sequentially epitaxially grown by metal organic chemical vapor deposition (MOCVD).

Next, as shown in FIG. 9B, p-G
While keeping the surface of the aAs substrate 407 and the p-InP layer 406 in close contact with each other, heating was performed in a hydrogen atmosphere at 670 ° C. for 30 minutes, and G
The outermost atoms of the aAs substrate 407 and the InP layer 406 are rearranged and bonded. As a result, the GaAs substrate 407 is bonded to the InP layer 406. Finally Figure 9
As shown in (c), InP401 is removed with hydrochloric acid to manufacture a laser device.

[0007]

In the surface emitting laser, the bottom reflector and the top reflector serve as a current path for injecting a current into the active layer. Therefore, it is preferable that the bottom reflector and the top reflector have a large area so as to have a low resistance. On the other hand, it is preferable that the active layer has a small area in order to efficiently confine the current to promote the recombination of carriers and improve the light emission efficiency.

However, in the above conventional technique, the upper reflecting mirror is etched into a tapered shape, and the upper surface of the upper reflecting mirror becomes small. For this reason, there arises a problem that the resistance of the upper reflecting mirror cannot be reduced so much. Further, since the upper surface becomes small, it is necessary to form the upper surface having an appropriate area, and there is also a problem that the surface emitting laser cannot be minutely formed.

The present invention has been made to solve the above problems, and an object thereof is to provide an upper reflecting mirror having vertical side walls and an active layer having an area smaller than that of the upper reflecting mirror. Another object of the present invention is to provide a surface emitting laser and a manufacturing method thereof.

[0010]

According to a method of manufacturing a surface emitting laser according to the present invention, a first semiconductor stack serving as a bottom reflector, an active layer and an active layer formed on the first semiconductor stack are formed. An upper reflecting mirror is provided on a semiconductor substrate having a second semiconductor laminated layer including an upper barrier layer and a lower barrier layer sandwiched therebetween and a third semiconductor laminated layer serving as an upper reflecting mirror formed on the second semiconductor laminated layer. Forming a defining mask pattern, and removing the third semiconductor stack by dry etching using the mask pattern as a mask until the surface of the upper barrier layer is exposed to form the upper reflecting mirror. A step of forming an etching protection film on at least a side surface of the upper reflecting mirror; and a part of the active layer and an upper burr by dry etching using the mask pattern and the etching protection film as a mask. A step of removing a part of the layer and a part of the lower barrier layer, and a part of the active layer, a part of the upper barrier layer and a part of the lower barrier layer are further removed by wet etching, Forming an active layer having a small area, whereby the above object is achieved.

The method may further include the step of forming the semiconductor substrate by an epitaxial growth method.

The etching protection film may be made of silicon oxide. Another surface-emitting laser manufacturing method of the present invention includes a second semiconductor device including at least an active layer formed on a first semiconductor substrate via a first semiconductor stack serving as a bottom reflector.
Removing a part of the semiconductor stack by etching to form the active layer in a predetermined shape, and the surface of the third semiconductor stack to be the upper reflecting mirror formed on the second semiconductor substrate and the third semiconductor stack. The step of bringing the second semiconductor stack into contact with the surface of the second semiconductor stack and heating the second semiconductor stack by heating in a reducing atmosphere, and thereby joining the third semiconductor stack and the second semiconductor stack by direct joining. To be achieved.

The method comprises the steps of forming a third semiconductor stack,
The method may further include the step of removing a part of the third semiconductor stack by etching to form an upper reflecting mirror having a larger area than the etched second semiconductor stack.

Further, according to the method of manufacturing a semiconductor laser of the present invention, a mask pattern defining an upper reflecting mirror is formed on a substrate having an active layer and a bottom clad layer and an upper clad layer sandwiching the active layer. And a step of forming the upper reflecting mirror by removing the upper semiconductor laminated layer by dry etching using the mask pattern as a mask,
Forming an etching protection film on at least a side surface of the upper reflecting mirror; removing a part of the active layer by dry etching using the mask pattern and the etching protection film as a mask; and forming a part of the active layer. Is further removed by wet etching to form an active layer having an area smaller than that of the upper reflecting mirror, whereby the above object is achieved.

Another method of manufacturing a semiconductor laser according to the present invention is
A step of removing a part of the active layer formed on the first semiconductor substrate via the first clad layer by etching; a surface of the second clad layer formed on the second semiconductor substrate; A step of bringing the surface of the active layer on the first semiconductor substrate into contact with the surface of the active layer, heating the active layer in a reducing atmosphere, and directly joining the active layer and the second clad layer together; The purpose is achieved.

Further, the surface emitting laser of the present invention has a bottom reflecting mirror, a semiconductor layer having at least an active layer formed on the bottom reflecting mirror, and a vertical side surface formed on the semiconductor layer. The above object is achieved by having an upper reflecting mirror and making the area of the active layer smaller than the area of the upper reflecting mirror.

[0017]

[Function] An upper reflecting mirror is formed by dry etching,
After forming the protective film on the upper reflecting mirror, the active layer and the barrier layer are dry-etched. By side-etching the active layer by wet etching, an active layer having an area smaller than that of the upper reflecting mirror is formed.

The active layer is etched into a predetermined shape by using the first substrate having the upper reflecting mirror and the second substrate having the bottom reflecting mirror and the active layer formed thereon, and thereafter, the active layer is subjected to the upper reflecting. Bonding is performed by direct bonding by closely contacting with a mirror and heating in a reducing atmosphere. As a result, an active layer having an area smaller than that of the upper reflecting mirror is formed.

[0019]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1A shows a cross section of a surface emitting laser 11 according to the present invention. The surface emitting laser 11 is the substrate 1
2 and a bottom reflecting mirror 14 and an active region 1 formed on the bottom reflecting mirror 14.
5 and an upper reflecting mirror 16 formed on the active region 15. The substrate 12 and the buffer layer 13 are made of n-type GaAs and p-type GaAs, respectively. The active region 15 is sandwiched between the bottom reflection mirror 14 and the top reflection mirror 16 and functions as a vertical resonator.

As shown in FIG. 1B, the active region 1
5 is an active layer 20, barrier layers 21 and 22, and a space.
Layers 22, 23, 24, 25, and 26
It The active layer 20 is sandwiched between barrier layers 21 and 22.
In addition, the barrier layers 21 and 22 are spacer layers 23 and 2
5 and the spacer layers 24 and 26.
The active layer 20 and the barrier layers 21 and 22 are
Dope In_0.2Ga_0.8As and undoped GaAs
Consists of. The spacer layers 23 and 24 are undoped.
Al_0.5Ga_0.5Spacer layers 25 and 26 made of As
Are p-type Al _0.5Ga_0.5As and n-type Al_0.5G
a_0.5It consists of As. The barrier layers 21 and 22 charge
The child and the hole are confined in the active layer 20. Single portrait mode
To adjust the length of the vertical cavity to oscillate at
Are provided with spacer layers 22 to 26.

Further, as shown in FIG. 1C, the bottom reflecting mirror 14 includes a p-type AlAs layer 27 and a p-type GaAs layer 2.
8 is a distributed reflector (DBR) alternately deposited,
The p-type AlAs layer 27 and the p-type GaAs layer 28 are 24.5 pairs. Similarly, as shown in FIG. 1D, the upper reflector 16 is a distributed reflector (DB) in which n-type AlAs layers 29 and n-type GaAs layers 30 are alternately deposited.
R), the n-type AlAs layer 29 and the n-type GaAs layer 3
It consists of 24 pairs with 0 as a pair. The p-type AlAs layer 27 and the p-type GaAs layer 2 are arranged so that the bottom reflecting mirror 14 and the upper reflecting mirror 16 reflect the light of the wavelength emitted from the active layer 20.
8, the thicknesses of the n-type AlAs layer 29 and the n-type GaAs layer 30 are selected.

A cap layer 17 made of n-type GaAs is formed on the upper reflecting mirror 16, and a cathode electrode 18 is formed.
Are electrically connected to the cap layer 17. The anode electrode 19 is formed on the p-GaAs layer 28 of the bottom reflecting mirror 14.
Are formed. The cathode 18 has a window 31
The laser light is emitted from the window 31.

A method of manufacturing the surface emitting laser 11 will be described below. First, as shown in FIG. 2A, the p-type GaAs buffer layer 13, the p-type AlAs layer 27 and the p-type GaAs layer 28 for the bottom reflecting mirror 14, the active layer 20 for the active region 15, and the barrier. Layers 21 and 22, spacer layer 23-
26, the n-type AlAs layer 29 and the n-type GaAs layer 30 for the upper reflecting mirror 16, and the n-type cap layer 17 as n.
Epitaxially grow on the type GaAs substrate 12. Various epitaxial growth methods well known to those skilled in the art can be used to form these semiconductor layers, but in order to accurately control the thickness of each semiconductor layer, metal organic chemical vapor deposition (MOCVD) or It is preferable to use a molecular beam epitaxial growth method (MBE) or the like. Each semiconductor layer has the composition and thickness shown in the table below.

[0025]

[Table 1]

The active layer 20 has a bandgap wavelength λg =
Since it has a wavelength of 0.98 μm, the bottom reflecting mirror 14 and the top reflecting mirror 16 are configured so as to reflect light having a wavelength of 0.98 μm. Such a reflector is a distributed reflector (DB
R) is well known to those skilled in the art, and it is possible to design a reflecting mirror that reflects an arbitrary wavelength by setting the refractive index and the thickness of the semiconductor layer forming the reflecting mirror to predetermined values. In this embodiment, two pairs of a GaAs layer and an AlAs layer are used.
By stacking 4 pairs, about 99% of light can be reflected.

As shown in FIG. 2B, after forming the silicon oxide film 40 on the n-type cap layer 17, a resist pattern 41 is formed on the silicon oxide film 40. The resist pattern 41 defines the area of the upper reflecting mirror 16. Since the upper reflecting mirror 16 has high resistance caused by band discontinuity between the AlAs layer and the GaAs layer, it is preferable to increase the area to reduce the resistance. Therefore, it is preferable that the resist pattern 41 is as large as possible,
As will be described later, in order to integrate the surface emitting laser 11 in two dimensions, it is preferable to make it small. Therefore, a circular shape having a diameter of about 10 to 15 μm is preferable.

The silicon oxide film 40 and the semiconductor layer are dry-etched using the resist pattern 41 as a mask. Before etching, the reaction chamber was evacuated to a vacuum degree of 1 × 10 ⁻⁴ Torr or less, and then chlorine gas at a flow rate of 1 sccm and 20 sc
Dry etching is performed at a pressure of 30 mTorr or less using an argon gas having a flow rate of cm. 9x before etching
It is more preferable to perform the etching with a vacuum degree of 10 ⁻⁷ Torr or less and while maintaining a pressure of about 5 mTorr. Under this condition, the semiconductor layer can be etched perpendicularly to the substrate 12. The etching is time-controlled so that the surface of the barrier layer 22 is exposed.

After removing the resist pattern 41, the substrate 12
After a silicon oxide film (not shown) is deposited so as to cover the entire surface of the barrier layer 22, the silicon oxide film is dry-etched until the surface of the barrier layer 22 is exposed. As shown in FIG. 2C, this forms sidewalls 43 on the side surfaces of the upper reflecting mirror 16 and the spacer layers 24 and 26. After that, as shown in FIG. 2D again, the silicon oxide film 40 and the sidewalls 43 are exposed by the dry etching method described above so that the surface of the spacer layer 23 is exposed.
Using the as a mask, the barrier layers 21 and 22 and the active layer 20 are removed. In this step, the silicon oxide film 40 may also be slightly etched. However, since the etching rate of the silicon oxide film 40 is slower than the etching rates of the barrier layers 21 and 22 and the active layer 20, the surface of the spacer layer 23 is exposed before the silicon oxide film 40 is completely etched.

Next, as shown in FIG. 2E, a mixture of citric acid, hydrogen peroxide and water (weight ratio 1: 1 :).
The substrate 12 is immersed in the mixed solution while keeping 1) at 20 ° C. This mixed solution etches GaAs, but Al _0.5 G
a _0.5 As hardly etches. Therefore,
As shown in FIG. 2E, the barrier layers 21 and 22 made of GaAs and having exposed side surfaces are selectively etched. N-type GaAs layer 30 constituting the upper reflecting mirror 16
This is because the side surface is covered with the sidewall and the spacer layer 23 whose surface is exposed is made of Al _0.5 Ga _0.5 As. The active layer 20 is made of In _0.5 Ga _0.5 As and is slower than the etching rates of the barrier layers 21 and 22. However, since the active layer 20 is thin and sandwiched between the barrier layers 21 and 22 which are well etched, it is eluted together with the barrier layers 21 and 22.

The etching time is determined so that the active layer 20 has a predetermined area. The area of the active layer 20 can be set to an arbitrary value irrespective of the area of the upper reflecting mirror 16, but in order to reduce the threshold current and increase the current density of the active layer 20, the area should be as small as possible. preferable. The diameter of the emission wavelength is preferable when it is not necessary to consider the restrictions on the manufacturing process and the problem of heat radiation.
Usually, the diameter is preferably about 3 to 5 times the wavelength. According to the present embodiment, since the emission wavelength is 0.98 μm, the cross section of the active layer 20 is preferably circular with a diameter of about 3 to 5 μm.

Finally, as shown in FIG. 2F, after removing the silicon oxide film 40 and the sidewalls 43, the cathode electrode 18 is formed on the cap layer 17. After removing part of the cap layers 23 and 25 and the p-AlAs layer 27 with hydrofluoric acid, the anode electrode 19 is formed of p-GaAs.
Formed on layer 28. This is because the semiconductor layer made of GaAs easily forms a good ohmic contact with the metal electrode.
After forming the electrodes, as shown in FIG.
A protective film 45 made of polyimide or the like may be formed thereon so as to cover the side surface of the active region 15 and the side surface of the upper reflecting mirror 16.

Further, as shown in FIG. 4, a plurality of surface emitting lasers 11 may be arranged two-dimensionally to form a laser array 46. When the surface emitting lasers 11 are arranged two-dimensionally, the arrangement interval is defined by the size of the upper reflecting mirror 16 of the surface emitting lasers 11. Therefore, in order to arrange the surface emitting lasers 11 at a high density, the upper reflection is required. The mirror 16 preferably has a small area.

As described above, the surface emitting laser 1 of the present invention.
1 comprises an upper reflector having vertical side faces and an active layer having an area smaller than that of the upper reflector, so that the current flowing through the upper reflector is confined in the active layer having a smaller area. Therefore, in the active layer, a high current density can be achieved and the threshold current can be lowered. Since the upper reflecting mirror is formed by dry etching, it can be processed into a desired sectional shape with high accuracy. On the other hand, since the active layer is formed by wet etching, non-radiative coupling centers that damage the active layer are not generated. Therefore, high external quantum efficiency is achieved. Since the area of the upper reflecting mirror and the area of the active layer do not impose any restriction on each other, they can be formed to have respective predetermined areas depending on the application. Particularly when the upper reflecting mirror has a high resistance, the current flowing through the upper reflecting mirror can be increased by increasing the area.

According to such a method, a surface emitting laser in which the side surface of the active layer 20 is not in contact with the semiconductor layer can be obtained. Since the side surface of the active layer is in contact with air having a much lower refractive index than the semiconductor layer, a high light confining effect can be expected.

The method of manufacturing the surface emitting laser 11 described above can also be applied to an edge emitting laser. 5 (a) to 5
A method of manufacturing the edge emitting laser 51 will be described with reference to (f). As shown in FIG. 5A, a clad layer 53 made of n-AlGaAs, an active layer 54 made of u-GaAs, and p-Al are formed on a semiconductor substrate 52 made of n-GaAs.
A cladding layer 55 made of GaAs and a cap layer 56 made of p-GaAs are epitaxially grown in order.

As shown in FIG. 5B, after a silicon oxide film 57 is formed on the cap layer 56, a resist pattern 58 is formed on the silicon oxide film 57, and the resist pattern 58 is used as a mask to form the silicon oxide film. Etch 57. Then, the dry etching is performed until the active layer 54 is exposed.

After removing the resist pattern 58, the substrate 52
After depositing a silicon oxide film (not shown) on the entire surface of the silicon oxide film, the silicon oxide film is etched until the surface of the active layer 54 is exposed, and as shown in FIG.
Are formed on the side surfaces of the cap layer 56 and the cladding layer 55.

As shown in FIG. 5D, the active layer 54 is again etched by the above-mentioned dry etching until the surface of the cladding layer 53 is exposed. Then, a mixed solution of citric acid, hydrogen peroxide solution and water (weight ratio 1:
Wet etching is performed using 1: 1) until the active layer 54 has a predetermined area. Finally, the silicon oxide film 57 and the sidewall 59 are removed, and the electrodes 60 and 61 are formed on the cap layer 56 and the substrate 52.

According to such a method, a laser in which the side surface of the active layer 54 does not contact the semiconductor layer can be obtained. Since the side surface of the active layer is in contact with air having a much lower refractive index than the semiconductor layer, a high light confining effect can be expected.

Example 2 The surface emitting laser 111 according to the present invention will be described below. FIG. 6E shows a cross section of the surface emitting laser 111 according to the present invention. Surface emitting laser 1
11 is formed on the p-type substrate 112 via the buffer layer 113, and includes a bottom reflecting mirror 114 and a bottom reflecting mirror 11.
4 and an upper reflecting mirror 116 formed on the active region 115. Board 1
Both 12 and the buffer layer 113 are made of p-type GaAs. The active region 115 is sandwiched between the bottom reflection mirror 114 and the top reflection mirror 116, and functions as a vertical resonator.

The active region 115 includes an active layer 120, barrier layers 121 and 122, spacer layers 122 and 123, and
Includes 124, 125, and 126. Active layer 1
20 is sandwiched between barrier layers 121 and 122, and the barrier layers 121 and 122 are spacer layers 123 and 12.
5 and the spacer layers 124 and 126. The active layer 120 and the barrier layers 121 and 122 are made of undoped In _0.2 Ga _0.8 As and undoped GaAs, respectively. In addition, the spacer layers 123 and 124
Is made of undoped Al _0.5 Ga _0.5 As, and the spacer layers 125 and 126 are p-type Al _0.5 Ga _0.5 As, respectively.
And n-type Al _0.5 Ga _0.5 As. Barrier layer 121
And 122 trap electrons and holes in the active layer 120. Spacer layers 122-126 are provided to adjust the length of the vertical cavity to oscillate in a single longitudinal mode.

The bottom reflector 114 is composed of the p-type AlAs layer 12
Is a distributed reflector (DBR) in which 7 and p-type GaAs layers 128 are alternately deposited, and p-type AlAs layers 127 and p
It is composed of 24.5 pairs of the type GaAs layers 128.
Similarly, the upper reflecting mirror 116 is a distributed reflector (DBR) in which the n-type AlAs layers 129 and the n-type GaAs layers 130 are alternately deposited, and the n-type AlAs layers 129 and the n-type G are provided.
It is composed of 24 pairs of aAs layers 130. The p-type AlAs layer 12 is formed so that the bottom reflector 114 and the top reflector 116 reflect light having a wavelength emitted from the active layer 120.
7, p-type GaAs layer 128, n-type AlAs layer 129, n
The thickness of the type GaAs layer 130 is selected.

A buffer layer 117 made of n-type GaAs and an n-type substrate 201 are formed on the upper reflecting mirror 116, and a cathode electrode 118 is electrically connected to the n-type substrate 201. An anode electrode 119 is formed on the p-type substrate 112.

A method of manufacturing the surface emitting laser 111 will be described below. First, as shown in FIG. 6A, an n-type substrate 201
An n-type buffer layer 117, an n-type AlAs layer 129 and an n-type GaAs layer 130 for the upper reflecting mirror 116 are epitaxially grown on the n-type buffer layer 117. Further, as shown in FIG. 6C, the p-type GaAs buffer layer 113 and the bottom reflecting mirror 11 are provided.
4 for p-type AlAs layer 127 and p-type GaAs layer 1
28, the active layer 120 for the active region 115, the barrier layers 121 and 122, and the spacer layers 123 to 126.
Epitaxial growth is performed on the mold substrate 112. Various epitaxial growth methods well known to those skilled in the art can be used to form these semiconductor layers, but in order to accurately control the thickness of each semiconductor layer, metal organic chemical vapor deposition (MOCVD) or MOCVD is used. , Molecular beam epitaxial growth method (MB
It is preferable to use E) or the like. Since each semiconductor layer is substantially the same as the semiconductor layer shown in the first embodiment, the description thereof will be omitted.

As shown in FIG. 6B, the n-type substrate 2
Resist pattern 14 on the n-type AlAs layer 129 of No. 01.
1 is formed, and n is formed using the resist pattern 141 as a mask.
Dry etching is performed until the surface of the mold buffer layer 117 is exposed. The etching method is the same as the method shown in the first embodiment. Further, as shown in FIG. 6D, a resist pattern 142 is formed on the spacer layer 126 of the p-type substrate 112, and the resist pattern 142 is also used as a mask to dry-etch the surface of the barrier layer 121 until it is exposed. I do. The active layer 120 is formed by dry etching.
The damaged portion generated on the side surface of the may be removed by about several nm by wet etching. The resist patterns 141 and 142 define the areas of the upper reflecting mirror 116 and the active layer 120, respectively. For the reason described in Example 1, the resist pattern 141 has a diameter of 10 to 15
The resist pattern 142 has a diameter of 3 to 3
It is preferably formed in a circular shape having a size of about 5 μm.

Next, after removing the resist patterns 141 and 142 respectively, the n-type substrate 201 and the p-type substrate 112 are dipped in a hydrofluoric acid aqueous solution or a mixed solution of sulfuric acid, hydrogen peroxide solution and water for about 30 seconds, Surface treatment of the n-type AlAs layer 129 and the spacer layer 126 is performed. As shown in FIG. 6E, the n-type AlAs layer 129 is aligned so that the center of the pattern of the n-type AlAs layer 129 of the n-type substrate 201 coincides with the center of the pattern of the spacer layer 126 of the p-type substrate 112.
And the surface of the spacer layer 126 are brought into close contact with each other, and MO
Leave it in the reaction chamber of the CVD device. While adhering hydrogen gas to the reaction chamber, the n-type substrate 201 and the p-type substrate 112 which are in close contact with each other are attached.
Is heated at about 600 ° C. for several hours. As a result, n-type A
Bonding occurs between atoms on the surfaces of the 1As layer 129 and the spacer layer 126, and the contact surfaces are bonded by direct bonding.
Finally, the cathode electrode 118 and the anode electrode 119 are formed on the n-type substrate 201 and the p-type substrate 112, respectively.

According to such a method, the upper reflecting mirror 11
Since 6 and the active region 115 including the active layer 120 can be processed independently of each other, they can be formed so as to have a predetermined area depending on the application. Further, when the surface emitting laser 111 is used as a two-dimensional array, it is not necessary to pattern the upper reflecting mirror 116, and FIG.
It is only necessary to bond the n-type substrate 201 having the semiconductor structure shown in FIG. 6 to the p-type substrate 112 shown in FIG. 6D by the above-described direct bonding. In this case, since the n-type substrate 201 and the p-type substrate 112 need not be aligned with each other, the manufacturing process is simplified.

The method of manufacturing the surface emitting laser 111 described above is as follows.
It can also be applied to edge emitting lasers. 7 (a) to 7
A method of manufacturing the edge emitting laser 151 will be described with reference to (f). As shown in FIG. 7A, a cladding layer 156 made of n-AlGaAs is epitaxially grown on a semiconductor substrate 155 made of n-GaAs. Further, as shown in FIG. 7B, a cladding layer 153 made of n-AlGaAs and an active layer 154 made of u-GaAs are epitaxially grown in order on a semiconductor substrate 152 made of p-GaAs.

As shown in FIG. 7C, the active layer 15
4 is patterned into a desired shape by wet etching or the like. Then, the semiconductor substrates 152 and 155 are soaked in a hydrofluoric acid aqueous solution or a mixed solution of sulfuric acid, hydrogen peroxide solution and water for about 30 seconds so that the cladding layer 156 and the active layer 1 are formed.
Surface treatment with 54 is performed. As shown in FIG. 7D, the surfaces of the active layer 154 and the cladding layer 156 are brought into close contact with each other and left as they are in the reaction chamber of the MOCVD apparatus. Semiconductor substrate 15 adhered while flowing hydrogen gas into the reaction chamber
2 and 155 are heated at about 600 ° C. for several hours. As a result, bonds are generated between the atoms on the surfaces of the clad layer 156 and the active layer 154, and the contact surfaces are bonded by direct bonding. A part of the semiconductor substrate 155 and the cladding layer 156 is removed by wet etching to form a cathode electrode 157 and an anode electrode 158 on the cladding layer 156 and the semiconductor substrate 152, respectively. According to such a method, a laser in which the side surface of the active layer 154 is not in contact with the semiconductor layer can be obtained.

In Examples 1 and 2 described above, InGa
Although the method of manufacturing the surface emitting laser provided with the active layer made of As has been described, the surface emitting laser provided with the active layer made of InGaAsP and AlGaInP can be similarly manufactured by the above method. Further, each semiconductor layer is not limited to the above composition and thickness. The protective film made of silicon oxide is formed by plasma CVD method, photo CVD method, thermal CVD method.
It can be formed by a method or the like. Besides silicon oxide, silicon nitride or photoresist can be used for the protective film.

[0052]

According to the present invention, the area of the active layer can be reduced without reducing the area of the reflecting mirror. Since the active layer is formed by wet etching, damage that would otherwise become a non-radiative center is reduced. Therefore, the current flowing through the active layer can be confined without increasing the resistance of the reflecting mirror serving as the current path, so that it is possible to realize a laser having high emission efficiency and operating at a low threshold current and a low driving voltage. it can. Further, according to the present invention, it is possible to form a laser in which the side surface of the active layer is in contact with air or the protective film having a refractive index lower than that of the semiconductor. Therefore, it is possible to realize a laser capable of confining laser light in the active layer more efficiently.

[Brief description of drawings]

1A is a schematic perspective view of a surface emitting laser according to a first embodiment of the present invention, and FIG. 1B is a sectional view of an active region thereof.
(C) and (d) are sectional views of the bottom reflector and the top reflector, respectively.

2A to 2F are cross-sectional views illustrating a method of manufacturing the surface emitting laser according to the first embodiment.

FIG. 3 is a sectional view showing the structure of a surface emitting laser having a protective film.

FIG. 4 is a configuration perspective view showing an array in which a plurality of surface emitting lasers are two-dimensionally arranged.

5A to 5F are process cross-sectional views illustrating a method of manufacturing an edge-emitting laser using the manufacturing method shown in FIG.

6A to 6E are process cross-sectional views illustrating a surface emitting laser according to a second embodiment and a method for manufacturing the same.

7A to 7E are process cross-sectional views illustrating a method of manufacturing an edge-emitting laser using the manufacturing method shown in FIG.

8A to 8D are process cross-sectional views illustrating a method of manufacturing a surface emitting laser according to a conventional technique.

9A to 9C are process cross-sectional views illustrating a method for manufacturing an edge-emitting laser according to a conventional technique.

[Explanation of symbols]

 11 surface emitting laser 12 substrate 13 buffer layer 14 bottom reflecting mirror 15 active region 16 top reflecting mirror 17 cap layer 18 cathode electrode 19 anode electrode 31 window

Claims (8)

[Claims] 1. A method of manufacturing a surface emitting laser, comprising: sandwiching a first semiconductor layer serving as a bottom reflector and an active layer formed on the first semiconductor layer. An upper reflector is defined on a semiconductor substrate having a second semiconductor stack including an upper barrier layer and a lower barrier layer, and a third semiconductor stack serving as an upper reflector formed on the second semiconductor stack. Forming a mask pattern for forming the upper reflecting mirror, and removing the third semiconductor stack by dry etching using the mask pattern as a mask until the surface of the upper barrier layer is exposed. A step of forming an etching protection film on a side surface of the upper reflecting mirror; and a part of the active layer, an upper barrier layer and a lower part of the active layer by dry etching using the mask pattern and the etching protection film as a mask. A step of removing a part of the barrier layer, and a part of the active layer, a part of the upper barrier layer and a part of the lower barrier layer are further removed by wet etching to reduce an area smaller than that of the upper reflecting mirror. And a step of forming an active layer having the same. 2. The method for manufacturing a surface emitting laser according to claim 1, further comprising the step of forming the semiconductor substrate by an epitaxial growth method. 3. The method for manufacturing a surface emitting laser according to claim 1, wherein the etching protection film is made of silicon oxide. 4. A method of manufacturing a surface emitting laser, comprising: a second semiconductor layer including at least an active layer formed on a first semiconductor substrate via a first semiconductor stack serving as a bottom reflector. A step of removing a part of the semiconductor stack by etching to form the active layer into a predetermined shape, and a third step of forming an upper reflecting mirror formed on the second semiconductor substrate.
The step of contacting the surface of the semiconductor stack with the surface of the second semiconductor stack and heating in a reducing atmosphere to bond the third semiconductor stack and the second semiconductor stack by direct bonding. A method of manufacturing a surface emitting laser, comprising: 5. The method for manufacturing a surface emitting laser according to claim 4, wherein the method comprises etching after removing a part of the third semiconductor stack after forming the third semiconductor stack. A method of manufacturing a surface emitting laser, further comprising the step of forming an upper reflecting mirror having an area larger than that of the second semiconductor laminated layer. 6. A method of manufacturing a semiconductor laser, the method defining an upper semiconductor layer on a substrate having an active layer and a bottom cladding layer and an upper cladding layer formed so as to sandwich the active layer. A step of forming a mask pattern, a step of removing the upper semiconductor stack by dry etching using the mask pattern as a mask to form the upper semiconductor layer, and a step of forming an etching protection film on at least a side surface of the upper semiconductor layer. A step of removing a part of the active layer by dry etching using the mask pattern and the etching protection film as a mask; and an area smaller than that of the upper semiconductor layer by removing a part of the active layer by wet etching. And a step of forming an active layer having a surface emitting laser. 7. A method of manufacturing a semiconductor laser, the method comprising: removing a part of an active layer formed on a first semiconductor substrate via a first cladding layer by etching. The surface of the second cladding layer formed on the second semiconductor substrate and the surface of the active layer on the first semiconductor substrate are brought into contact with each other and heated in a reducing atmosphere, and the active layer and the second A method for manufacturing a surface emitting laser, which comprises a step of directly joining the cladding layer. 8. A surface having a bottom reflecting mirror, a semiconductor layer having at least an active layer formed on the bottom reflecting mirror, and an upper reflecting mirror having vertical side surfaces formed on the semiconductor layer. A surface emitting laser, wherein the active layer has an area smaller than that of the upper reflecting mirror.