JP3147328B2 - Surface emitting semiconductor laser manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a surface emitting laser having a current confinement structure using a direct bonding method.

[0002]

2. Description of the Related Art In recent years, two-dimensional high-density integration of long-wavelength surface emitting lasers is possible, so that their development as key devices as light emitting light sources for optical signal processing and optical information processing has been greatly desired.

Heretofore, this type of device has been disclosed, for example, in Appl.
s. lett. 66 1995 pp.1030
After bonding the R portion and the light emitting layer, the current confining structure for efficiently injecting the current into the active layer in the minute region is In.
It was formed by etching in a post type up to the upper part of the P clad layer.

[0004]

However, in the above-mentioned device, when a post type having a small diameter is etched by etching, a non-light-emitting process is increased due to the influence of surface recombination of the active layer and the like, leading to laser oscillation. There is a problem that the threshold current increases.

Further, when a current constriction structure is manufactured by ion implantation after direct bonding, the active layer may be damaged,
Since ions are implanted into a deep region (for example, 4 μm), the ions to be implanted are limited to light atomic weight elements due to the limitation of the acceleration voltage, and there is a problem in reliability at the time of high-temperature operation.

Further, when fabricating an ultrafine structure, the resistance of the semiconductor multilayer film is significantly increased, and there has been a problem of deterioration of device characteristics.

In addition, when integrated with an electronic circuit, the type of ion atoms to be implanted is limited, so that the etching depth becomes about 10 μm, and various problems occur in the process method in the step structure. However, there has been a problem that it is difficult to manufacture an optimum structure.

[0008]

The main feature of the present invention is to form a current confining structure in a reflecting mirror or a cladding layer in advance and then fabricate a surface emitting semiconductor laser by direct bonding. The above-mentioned problem is solved by various means.

<First Embodiment of the Invention> A first method for manufacturing a surface emitting semiconductor laser according to the present invention is directed to a method of manufacturing a semiconductor device having Ga having a first conductivity type.
An Al _x1 Ga _1-x1 As film and an Al _x2 Ga _1-x2 As film (0 ≦ x1, x2 ≦ 1) having the first conductivity type and a film thickness of / 4 of the optical wavelength are formed on an As substrate. A step of alternately stacking to form a first light reflecting mirror, and a stacked structure including a cladding layer having a first conductivity type, an active layer, and a cladding layer having a second conductivity type on an InP substrate; Forming a cladding layer having the first conductivity type facing the InP substrate;
On a GaAs substrate having the second conductivity type, Al _x13 Ga _1-x3 A having the second conductivity type and a film thickness of / 4 of the optical wavelength is used.
forming a second light reflecting mirror by alternately laminating an s film and an Al _x4 Ga _1-x4 As film (0 ≦ x3, x4 ≦ 1); and forming the first and second light reflecting mirrors. A step of implanting an ionic species for increasing the resistance of AlGaAs while leaving a closed region; a step of bonding the first reflecting mirror and the laminated structure on the InP substrate by heating; and a step of bonding. Removing the InP substrate from the laminated structure that has passed through, and bringing the laminated structure from which the InP substrate has been removed into close contact with the second light reflecting mirror, and heating and bonding. I do.

<Embodiment of Second Invention> A second method for manufacturing a surface emitting semiconductor laser according to the present invention is directed to a method of manufacturing a semiconductor device having Ga having the first conductivity type.
An Al _x1 Ga _1-x1 As film and an Al _x2 Ga _1-x2 As film having a first conductivity type and a thickness of / 4 of the optical wavelength are formed on an As substrate.
.Ltoreq.x1, x2.ltoreq.1) to form a first light reflecting mirror, a first cladding layer not doped with impurities, an active layer, and a second cladding layer doped with no impurities on the InP substrate. Forming a stacked structure comprising: a first cladding layer facing the InP substrate; and
An Al _x13 Ga _1-x3 As film having a second conductivity type and a thickness of 1 of the optical wavelength on a GaAs substrate having a conductivity type of
forming a second light reflecting mirror by alternately laminating 1 _x4 Ga _1-x4 As films (0 ≦ x3, x4 ≦ 1); and forming a closed region in the second cladding layer to a second conductivity type. A step of adhering the second reflecting mirror and the laminated structure by bringing the laminated structure into close contact with each other and heating; removing the InP substrate from the laminated structure having undergone the bonding step; A step of setting a closed region, which is located in the first clad layer of the laminated structure having undergone the removing step and facing the region of the second clad layer having the second conductivity type, to the first conductivity type, And a step of heating and bonding the laminated structure in which the closed region located in the first clad layer has the first conductivity type and the first light reflecting mirror.

<A third aspect of the invention> A third method for manufacturing a surface emitting semiconductor laser according to the present invention is the method for manufacturing a surface emitting semiconductor laser described above, wherein the first or second reflecting mirror and the reflecting mirror are formed. Forming a layer structure including an active layer of an electronic device between the GaAs substrates to be formed, bonding the first reflecting mirror and the laminated structure including the active layer, and the second step. After the step of bonding the laminated structure including the reflecting mirror and the active layer, the step of removing the GaAs substrate on which the layer structure is formed, and the step of removing the GaAs substrate, And forming an element.

<Operation> In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems as follows. That is, since there is no ion implantation region or ion passage region in the active layer, the current confinement structure can be formed without damaging the active layer. Further, since the depth of the ion implantation is extremely small, the acceleration voltage can be reduced, and stable heavy atom ions can be implanted even at the time of high-temperature operation. Further, when fabricating an ultrafine structure, it is easy to fabricate a semiconductor multilayer film which is a reflector having a high electric resistance so as to have a wide range of current paths, and it is possible to suppress the influence of heat generation. When an electronic circuit is integrated, not only an insulating layer can be formed by ion implantation, but also various p-type and n-type ion species can be implanted, and a wide range of manufacturing steps can be performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a surface emitting semiconductor laser according to the present invention will be described below.

(First Embodiment) FIGS. 1 and 2 show the steps of a method of manufacturing a long-wavelength surface emitting laser according to an embodiment of the present invention. As shown in the drawings, the method for manufacturing a long-wavelength surface emitting laser according to the present embodiment is manufactured by the following steps. Step of Producing First Mirror on First Substrate First GaAs substrate 10 having the first conductivity type
Al _x1 Ga having a conductivity type of and a film thickness of 1/4 of the optical wavelength
_1-x1 As film and Al _x2 Ga _1-x2 As film (0 ≦ x1, x2 ≦
1) and alternately stacking to form an epitaxial growth as the first light reflecting mirror 11 (see FIG. 1A). Step of manufacturing a stacked structure on the third substrate. Cladding layer 1 having mold
4, an active layer 15, and a cladding layer 16 having a second conductivity type
Forming a cladding layer 14 having the first conductivity type so as to face the InP substrate 17 (see FIG. 1B). Fabrication of a second reflecting mirror on the second substrate A GaAs substrate 19 having the second conductivity type is provided with Al _x13 Ga having a second conductivity type and a film thickness of 1 of the optical wavelength.
_1-x3 As film and Al _x4 Ga _1-x4 As film (0 ≦ x3, x4 ≦
1) alternately stacking to form epitaxial growth as the second light reflecting mirror 18 (see FIG. 1 (c)). Step of implanting ion species.
a step of ion-implanting 12 oxygen as an ion species for increasing the resistance of lGaAs while leaving a closed region; and a step of bringing a laminated structure of a third substrate into close contact with the first reflector side of the first substrate. Step of bonding the reflecting mirror 11 and the laminated structure on the InP substrate 17 by heating them together (FIG. 2)
(Refer to (a)) Step of removing the third substrate after adhesion Step of removing the InP substrate 17 from the laminated structure after the adhering step The second structure is added to the laminated structure adhered to the first reflector side of the first substrate. A step of heating and bonding the laminated structure from which the InP substrate 17 has been removed and the second light reflecting mirror 18 (see FIG. 2B)

Hereinafter, a detailed manufacturing process of this embodiment will be described.

First, as shown in FIG. 1A, a first reflecting mirror 11 is formed on a GaAs substrate 10 as a first substrate.
GaAs layer doped with n × 3 × 10 ¹⁸ cm ⁻³ and AlAs
The layers are alternately epitaxially grown at a thickness of 1/4 of the optical wavelength. Also, as shown in FIG.
As the second reflecting mirror 18, the GaAs substrate 1 as the second substrate
On top of this, a p-type doped GaAs layer and an AlAs layer are alternately grown 30 pairs at a film thickness of 1/4 of the optical wavelength.

Next, after a pattern having a diameter of 10 μm is formed with a resist on the growth film 11 on the first substrate, an acceleration voltage 8
Oxygen ion implantation 1 at 0 keV and a dose of 2 × 10 ¹⁴ cm ^-3
Do 2 After removing the resist, annealing is performed at 450 ° C. in a hydrogen atmosphere.

Next, as shown in FIG. 1B, an InP lattice-matched to InP is formed on an InP substrate 17 as a third substrate.
GaAs etching stop layer 13 and 5 × 10 ¹⁷ cm ⁻³
p-type doped InP first cladding layer 14, non-doped InGaAsP (1.3 μm composition), InGaAs
Of the MQW active layer 15 composed of 5.5 pairs alternately and 5 × 1
The InP second cladding layer 16 n-doped at 0 ¹⁷ cm ^-3 is epitaxially grown so that the total film thickness excluding the etching stop layer 13 becomes the thickness of the optical wavelength λ.

After removing the surface oxide film of the epitaxially grown film of each of the first substrate 10 and the third substrate 17 with HF, the substrate is annealed at 600 ° C. in a hydrogen atmosphere to directly adhere (see FIG. 2A). .

Next, HCl and H ₃ PO ₄ are deposited on the InP substrate 17.
And remove the InGaAs etching stop layer 13 with sulfuric acid, hydrogen peroxide solution and water.

Next, after removing the surface oxide film of the epitaxial growth film of the second substrate 19 with HF, the p-type InP
The first clad layer 14 is annealed at 600 ° C. in a hydrogen atmosphere to be directly bonded.

Thereafter, GaAs 19 as the second substrate is removed with a mixed solution of aqueous ammonia and aqueous peroxide solution, and HF is removed.
The AlAs layer which is a part of the reflector is etched with the aqueous solution.

Thereafter, RI is used for electrical isolation between elements.
Etching is performed by BE.

Finally, an AuZnNi p-type electrode is patterned 21 on the upper surface, and an AR coat 22 is deposited on the substrate side to reduce return light, and then patterned to form an A
uGeNi22 is deposited (see FIG. 2B).

When the current-light output characteristics of the long-wavelength surface emitting laser having the above-described structure were measured,
Laser oscillation with an oscillation wavelength of 1.55 μm at a threshold current of 4 mA was confirmed. In addition, since the current confinement was not present in the high-resistance DBR layer, the element resistance was reduced to 20Ω near the threshold current.

In this embodiment, a semiconductor multilayer film is used as a reflecting mirror, but one of them may be a dielectric multilayer film. In addition, although ion implantation of oxygen was used as the current confinement layer, it goes without saying that a similar effect can be obtained by using other elements.

(Second Embodiment) FIG. 3 shows a process procedure of a manufacturing method of an embodiment of a long-wavelength surface emitting laser according to the present invention. In the surface emitting laser according to the second embodiment, the process is basically the same as that of the first embodiment described above.

First, as shown in FIG. 3, an n-type GaAs layer and an AlAs layer are alternately formed on a GaAs substrate 30, which is a first substrate, with a film thickness of 1/4 of the optical wavelength.
Zero-pair epitaxial growth 30 is performed (FIG. 3A).

Separately, a pair of p-type GaAs layers and AlAs layers are alternately grown on a GaAs substrate as the second substrate as a second reflecting mirror with a thickness of / 4 of the optical wavelength alternately.

Next, on an InP substrate 32 as a third substrate,
InGaAs etching stop layer 36, InP first cladding layer 35, InGaAsP (1.3 μm composition),
MQW active layer 3 composed of 5.5 pairs of InGaAs alternately
4. The InP second cladding layer 33 is epitaxially grown non-doped sequentially so that the total film thickness excluding the etching stop layer becomes the thickness of the optical wavelength λ.

Next, after a pattern having a diameter of 10 μm is formed with a resist on the growth film on the third substrate, an acceleration voltage of 100 μm is formed.
Si ion implantation 37 at keV and dose 2 × 10 ¹⁶ cm ^-3
a is performed in the InP second cladding layer 33. After removing the resist, annealing is performed at 450 ° C. in a hydrogen atmosphere.

After removing the surface oxide film of each of the epitaxially grown films of the first substrate 30 and the third substrate 32 with HF,
Anneal at 600 ° C. in a hydrogen atmosphere for direct bonding.
Next, the InP substrate is etched away with HCl and H ₃ PO ₄ , and the InGaAs etching stop layer 36 is removed.
Is removed with sulfuric acid, hydrogen peroxide and water.

Next, after forming a pattern having a diameter of 10 μm with a resist, an acceleration voltage of 100 keV and a dose of 2 × 10 ¹⁶ cm are used.
^-3 with Be ion implantation 37b and InP first cladding layer 3
Perform during 5. After resist removal, 450 ° C in hydrogen atmosphere
Anneal.

Next, after removing the surface oxide film of the epitaxially grown film of the second substrate with HF, it is annealed at 600 ° C. in a hydrogen atmosphere on the first cladding layer of InP and directly adhered thereto. The GaAs as the second substrate is removed with the mixed solution, and the AlAs layer as a part of the reflecting mirror is etched with the HF aqueous solution.

Finally, as shown in FIG. 3 (b), an AuZnNi p-type electrode pattern 39b is formed on the upper surface, and an AR coat 39 is deposited on the substrate side to reduce return light, followed by patterning. And AuGeNi39a is deposited. Finally, DBR by RIBE for isolation between devices
Etch the layer.

When the current-light output characteristics of the long-wavelength surface emitting laser configured as described above were measured, laser oscillation was confirmed at a threshold current of 6 mA.

In this embodiment, a semiconductor multilayer film is used as a reflecting mirror, but one of them may be a dielectric multilayer film. In this embodiment, ions are implanted into the cladding layer. However, it goes without saying that the same effect can be obtained by ion-implanting a part of the reflector, which is a semiconductor multilayer film, into a non-doped region.

(Third Embodiment) FIG. 4 shows a process procedure of a manufacturing method of an embodiment of a long-wavelength surface emitting laser according to the present invention.

In the surface emitting laser according to the third embodiment, the process is basically the same as that of the first embodiment described above. explain. As shown in FIG. 4, by operating in the same manner as in the first embodiment, the first substrate G as the first reflecting mirror is used.
An n-type GaAs layer and an AlAs layer are alternately epitaxially grown 50 on the aAs substrate at a thickness of 1/4 of the optical wavelength alternately, and GaAs as the second substrate is used as a second reflecting mirror.
An InGaP etch stop layer, a Si-doped n ⁺ GaAs contact layer 45, an n ^- GaAs channel layer (acting as an active layer) 46 and a non-doped Ga
An As layer 47, an InGaP etch stop layer, a p-type doped GaAs layer and an AlAs layer are alternately formed by 1 of the optical wavelength.
30 pairs of epitaxial growths 51 are alternately performed sequentially with a film thickness of.

Next, after a pattern having a diameter of 10 μm is formed with a resist on the growth film on the first substrate, an acceleration voltage of 80 keV is applied.
Then, oxygen ions are implanted at a dose of 2 × 10 ¹⁴ cm ⁻³ (52 in FIG. 4A). After removing the resist, annealing is performed at 450 ° C. in a hydrogen atmosphere.

Next, on the InP substrate as the third substrate, In
An InGaAs etching stopping layer lattice-matched to P, a 5 × 10 ¹⁷ cm ⁻³ p-type doped InP first cladding layer 54, and 5.5 pairs of non-doped InGaAsP (1.3 μm composition) and InGaAs alternately. The MQW active layer 53 and the InP second cladding layer 55 n-doped with 5 × 10 ¹⁷ cm ⁻³ are sequentially epitaxially grown so that the total film thickness excluding the etching stop layer becomes the thickness of the optical wavelength λ.

After removing the surface oxide films of the epitaxially grown films of the first substrate and the third substrate with HF, they are annealed at 600 ° C. in a hydrogen atmosphere to perform direct bonding. Next, the InP substrate is removed by etching with HCl and H ₃ PO ₄ .

Next, after removing the surface oxide film of the epitaxially grown film of the second substrate with HF, the film is annealed at 600 ° C. in a hydrogen atmosphere on the p-type InP first cladding layer to directly adhere.

Thereafter, the GaAs as the second substrate is removed with a mixed solution of aqueous ammonia and an aqueous solution of peroxide, and the I.sub.2 is removed with hydrochloric acid.
The nGaAsP etching stop layer is etched with an HF aqueous solution to etch the AlAs layer which is a part of the reflecting mirror.

Thereafter, the n ⁺ G
aAs contact layer 45 and n ^- GaAs channel layer 4
6, GaAs 47 of the non-doped layer, and the InGaP etch stop layer are etched.

In the surface emitting laser part, p of AuZnNi is used.
After patterning a mold electrode and depositing an AR coat 49 on the substrate side to reduce return light, patterning is performed and an AuGeNi layer 48 is deposited on the back surface of the first substrate.

In order to form a MESFET, the n ⁺ GaAs contact layer 45 in the gate portion is etched, and when the gate length and the gate width are 3 μm and 20 μm, respectively, Ti /
A Pt / Au layer 43 is formed.

After that, source and drain electrodes are formed on the n ⁺ contact layer, and the source electrode and the p electrode of the surface emitting laser are connected by Cr / Au 41.

MESFET constructed as described above
FIG. 4 shows an example in which a laser and a long-wavelength surface emitting laser are integrated.

When the gate voltage-light output characteristics when the drain voltage was 8 V were measured, the results were as shown in FIG.
The modulation operation of the surface emitting laser by the SFET was confirmed.

In this embodiment, the surface emitting laser and the FET are integrated, but may be combined with another electronic device such as an HBT (hetero bipolar transistor). It goes without saying that the same effect can be obtained even when the structure of the surface emitting laser is set to the second embodiment.

[0052]

As described above with reference to the embodiments, according to the long wavelength band surface emitting laser of the present invention, the current confinement structure can be formed without damaging the active layer, and the depth of ion implantation can be increased. Since the region becomes extremely shallow, the acceleration voltage can be reduced, and stable heavy ion implantation can be performed even during high-temperature operation.

When an electronic circuit is integrated, not only an insulating layer can be formed by ion implantation, but also various ion types of p-type and n-type can be implanted, so that a wide range of manufacturing steps can be performed. It can be widely applied in the field of OEIC together with the bonding technology.

[Brief description of the drawings]

FIG. 1 shows epi structures of three types of substrates constituting a surface emitting laser of the present invention.

FIG. 2 shows a part (a) of the process shown in Example 1 and (b) a structural view of a surface emitting laser according to the present invention.

FIGS. 3A and 3B show a manufacturing step (a) of the surface emitting laser according to the present invention shown in Example 2 and a sectional structural view (b) of the surface emitting laser.

FIG. 4 is an integrated sectional structural view of the FET and the surface emitting laser according to the present invention shown in Embodiment 3;

FIG. 5 is a graph showing gate voltage-light output characteristics.

[Explanation of symbols]

Reference Signs List 10 first GaAs substrate 11 first light reflecting mirror 12 oxygen ion implantation region 13 InGaAs etching stop layer 14 p-type InP cladding layer 15 MQW active layer 16 n-type InP cladding layer 17 InP substrate 18 second light reflecting mirror 19 GaAs substrate 21 AuZnNi / Au electrode 22 AR coating film 23 AuGeNi / Au electrode 31 First reflector 32 InP substrate 33 n-type InP cladding layer 34 MQW active layer 35 p-type InP cladding layer 36 InGaAs etching stop layer 37a Si ion implantation region 37b Be ion implanted region 38 second reflecting mirror 39 AR coat film 39a AuGeNi / Au electrode 39b AuZnNi / Au electrode 41 AuZnNi wiring electrode 42 drain electrode 43 Ti / Pt / Au gate electrode 44 source electrode 45 n ⁺ aAs layer 46 n ^- GaAs channel layer 47 i-GaAs layer 48 AuGeNi / Au electrode 49 AR coat film 50 reflecting mirror 51 reflecting mirror portion 52 ion implantation section 53 MQW active layer 54 InP cladding layer 55 InP cladding layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-335967 (JP, A) Appl. Phys. Lett. 64 [12] (1994) p. 146-1465 Appl. Phys. Lett. 62 [7] (1993) p. 738-740 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (3)

(57) [Claims] An GaAs substrate having a first conductivity type has a first conductivity type and an A film having a thickness of 1/4 of an optical wavelength.
l _x1 Ga _1-x1 As film and Al _x2 Ga _1-x2 As film (0 ≦ x
1, x2 ≦ 1) alternately to form a first light reflecting mirror; and a cladding layer having a first conductivity type, an active layer, and a cladding layer having a second conductivity type on an InP substrate. And a cladding layer having the first conductivity type by the InP.
Forming opposite the substrate, the first two of the GaAs substrate having a conductivity type, Al _x13 Ga _1-x3 A and a quarter of the thickness of the second conductive type, and an optical wavelength
forming a second light reflecting mirror by alternately laminating an s film and an Al _x4 Ga _1-x4 As film (0 ≦ x3, x4 ≦ 1); and forming the first and second light reflecting mirrors. A step of implanting an ion species for increasing the resistance of AlGaAs while leaving a closed region; a step of adhering the first reflecting mirror and the laminated structure on the InP substrate by heating; and a step of adhering; Removing the InP substrate from the laminated structure that has passed through, and bringing the laminated structure from which the InP substrate has been removed into close contact with the second light reflecting mirror, and heating and bonding. Surface emitting semiconductor laser manufacturing method. Wherein Al _x1 G having a quarter of the thickness of the first conductivity type and the optical wavelength GaAs substrate having a first conductivity type
a _1-x1 As film and Al _x2 Ga _1-x2 As film (0 ≦ x1, x2
≦ 1) alternately to form a first light reflecting mirror, and a stack comprising a first clad layer not doped with impurities, an active layer and a second clad layer not doped with impurities on the InP substrate. The structure is the first cladding layer
Forming an Al _x13 Ga _1-x3 As film and an Al _x4 Ga ₁ film having a second conductivity type and a film thickness of の of the optical wavelength on a GaAs substrate having the second conductivity type; forming a second light reflecting mirror by alternately laminating _-x4 As films (0 ≦ x3, x4 ≦ 1); and setting a closed region in the second cladding layer to a second conductivity type. A step of adhering the second reflecting mirror and the laminated structure by bringing the laminated structure into close contact with each other and heating; a step of removing the InP substrate from the laminated structure after the step of adhering; and a step of removing the InP substrate. The second clad layer is located on the first clad layer of
Making the closed region facing the region of the first conductivity type the first conductivity type; and forming the stacked structure having the closed region located on the first cladding layer of the first conductivity type and the first light reflection. Attach the mirror,
A method for manufacturing a surface emitting semiconductor laser, comprising a step of heating and bonding. 3. The method for manufacturing a surface emitting semiconductor laser according to claim 1, wherein an active element of an electronic element is provided between the first or second reflecting mirror and the GaAs substrate on which the reflecting mirror is formed. Forming a layer structure comprising a layer; bonding the first reflecting mirror to the laminated structure comprising the active layer; and forming the laminated structure comprising the second reflecting mirror and the active layer. The method comprises the steps of: removing the GaAs substrate on which the layer structure is formed after the bonding step; and forming an electronic element on the layer structure after the step of removing the GaAs substrate. Surface emitting semiconductor laser manufacturing method.