JP2000232252A - Semiconductor optical integrated device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical integrated device where a laser device and a photodetector which are monolithically formed on a common semiconductor substrate can be driven by a single power supply. SOLUTION: This device 39 is equipped with a laser device 40 and a photodetector 41 which are monolithically formed on a common InP substrate 21, where the laser device 40 and the photodetector 41 are electrically isolated from each other by an isolation groove 42. The photodetector 41 is possessed of a laminated structure composed of an N-AlInAs layer 22 of thickness 100 nm, an N-InP clad layer 23, an MQW active layer 24, a P-InP clad layer 25, a P-AlInAs layer 26 of thickness 50 nm, a P-type InP clad layer 27, and a P-GaInAs contact layer 28. Al contained in the P-AlInAs layer is oxidized into an Al oxide layer 29 which is formed on each side of a ridge stripe of P-AlInAs layer to serve as a current constriction structure, and the N-AlInAs layer 22 is turned into an Al oxide layer 30 where Al contained in all the layer 22 is all oxidized. The photodetector is electrically isolated from a semiconductor substrate by the Al oxide layer 30 and electrically separated by an isolation groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical integrated device in which a laser device and a light receiving device are monolithically formed on a semiconductor substrate, and more particularly, to a laser device and a light receiving device which can be driven by a single power supply. The present invention relates to a semiconductor optical integrated device provided with an element.

[0002]

2. Description of the Related Art A semiconductor optical integrated device is a device in which optical elements having mutually different functions are monolithically formed on one substrate. For example, a semiconductor laser device and a light receiving element are integrated on one substrate. There is.

Here, a configuration of a conventional semiconductor optical integrated device in which a semiconductor laser element and a light receiving element are monolithically formed on a common semiconductor substrate will be described with reference to FIG. FIG. 7A is a sectional view showing a configuration of a conventional semiconductor optical integrated device, and FIG. 7B is a circuit diagram of the conventional semiconductor optical integrated device. In the conventional semiconductor optical integrated device 20, as shown in FIG. 7A, the laser element 10 and the light receiving element 11 have a common n-type.
It is formed on the InP substrate 1 and is electrically separated from each other by a separation groove 8, and can be independently driven.

A laser element 10 and a light receiving element 11 are respectively provided on an InP substrate 1 with an n-InP cladding layer 2 and a G
The semiconductor device has a laminated structure of a semiconductor layer including an aInAsP active layer 3, a p-InP clad layer 4, and ap ⁺ -GaInAs contact layer 5, and a p-side electrode 6 is provided on each laminated structure.
A common n-side electrode 7 is provided on the back surface of the substrate 1. Note that the active layer 3 functions as a light absorbing layer in the light receiving element 11.
The separation groove 8 separates the p-side electrode 6, the contact layer 5, the cladding layer 4, the active layer 3, and the cladding layer 2, and cuts into the upper layer of the InP substrate 1.

Next, a method for manufacturing a semiconductor optical integrated device will be described with reference to FIG. FIG. 8 is a view III- of FIG.
It is sectional drawing of the cross section parallel to the isolation | separation groove of III. First, FIG.
As shown in (1), an n-InP cladding layer 2, a GaInAsP active layer 3, and a p-InP cladding layer 4 are sequentially stacked on an n-InP substrate 1 by MOCVD. Next, using the SiO ₂ film as a mask, a stripe-shaped mesa having a width of about 1.5 μm is formed by dry etching such as RIBE. Then, using the above-mentioned SiO ₂ film as a mask, p-InP 12 and n-
A current blocking layer made of InP13 is selectively grown only on the mesa side surface.

Next, after removing the SiO ₂ film with buffered hydrofluoric acid, a p-InP cladding layer 4A and ap ⁺ -GaInAs contact layer 5 are laminated on the entire surface by MOCVD. Next, the separation groove 8 is formed by, for example, RIBE. After polishing the back surface of the InP substrate to a thickness of about 100 μm, the p-side electrode 6 and the n-side electrode 7 are formed.

In such a semiconductor optical integrated device formed monolithically on one substrate, the active layer of the laser element and the light absorbing layer of the light receiving element can be formed in the same process step with the same composition. As described above, the alignment at the time of mounting the semiconductor optical integrated device is not required, and the number of components can be reduced, so that the cost of the entire semiconductor optical integrated device module can be reduced.

[0008]

However, since it is necessary to drive the laser device by applying a forward bias to the laser device and to apply a reverse bias to the light receiving device, the laser device and the light receiving device are thus provided on a common semiconductor substrate. When the element is formed, FIG.
As shown in (b), two separate power supplies are required.
Therefore, for example, when a semiconductor optical integrated device is mounted as a package, the electric circuit becomes more complicated, the cost of the entire package increases, and the package becomes larger.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor optical integrated device having a configuration in which a laser element and a light receiving element formed monolithically on a common semiconductor substrate can be driven by a single power supply, and a method of manufacturing the same. It is to provide.

[0010]

In order to achieve the above object, a semiconductor optical integrated device according to the present invention is formed monolithically on a common semiconductor substrate and is electrically isolated from each other by element isolation regions. A semiconductor optical integrated device having a laser element and a light receiving element, wherein an electrode of one of the laser element and the light receiving element is formed on a back surface of the semiconductor substrate, and the other element is electrically connected to the semiconductor substrate. It is characterized by being electrically separated by a separation band.

In the present invention, there is no restriction on the configuration of the electrical separation zone, and it can be formed of an oxide insulating film, for example, an Al oxide layer. By forming the electrical isolation band with the Al oxide layer and the current confinement structure with the Al oxide layer, both the electrical isolation band and the current confinement structure can be formed by one oxidation process. The present invention can be applied without any restrictions on the composition, film thickness, and the like of the compound semiconductor multilayer structure forming the laser element and the light receiving element.

Further, according to the present invention, there is provided a method of manufacturing a semiconductor optical integrated device, comprising: a semiconductor device having a laser element and a light receiving element formed monolithically on a common semiconductor substrate and electrically separated from each other by an element isolation region. A method for manufacturing an optical integrated device, comprising: forming a first oxidized layer made of a compound semiconductor containing Al on a semiconductor substrate in both a laser element forming region and a light receiving element forming region; Forming a double heterostructure including at least a second oxidized layer made of a compound semiconductor containing Al;
In the laser element formation region, a step of forming a first ridge stripe exposing the second oxidized layer, and in the light receiving element formation region, in addition to the formation of the first ridge stripe,
Further, a step of forming a second ridge stripe wider than the first ridge stripe and exposing the first layer to be oxidized, and performing a heat treatment in a water vapor atmosphere to form a second ridge stripe in the laser element formation region Oxidizing the side of the ridge stripe of the layer to be oxidized, and all the layers of the first layer to be oxidized and the side of the ridge stripe of the second layer to be oxidized in the light receiving element formation region.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment of Semiconductor Optical Integrated Device This embodiment is an example of an embodiment of a semiconductor optical integrated device according to the present invention. FIG. 1A shows a laser device and a semiconductor optical integrated device of this embodiment. FIG. 1B is a cross-sectional view illustrating a layer structure of the light receiving element, FIG. 1B is a circuit diagram of the laser element and the light receiving element, FIG. 2A is a cross-sectional view of the laser element of FIG. 2B is a sectional view of the light receiving element of FIG. 1 taken along the line II-II. The semiconductor optical integrated device 39 of the present embodiment is
As shown in FIG. 1, a laser device 40 and a light receiving device 41 are formed monolithically on a common InP substrate 21 and are electrically separated by a separation groove 42.

The laser element 40 is shown in FIGS.
As shown in FIG. 3A, a 100-nm-thick epitaxially-grown film having a thickness of 100 nm is formed on an n-InP substrate 21 having a thickness of 100 μm.
m-n-AlInAs layer 22, n-InP cladding layer 2
3, GRIN-SCH-MQW active layer 24, p-InP
Cladding layer 25, p-AlInAs layer 2 having a thickness of 50 nm
6, p-InP cladding layer 27, and p ⁺ -GaInA
It has a laminated structure composed of the s-contact layer 28.

The laser device 40 includes the upper layer of the n-InP cladding layer 23, and the laminated structure thereabove is shown in FIG.
As shown in (a), it is formed in a stripe-shaped mesa. Further, the stripe-shaped mesa includes a ridge stripe composed of a p-InP clad layer 25 and a p-AlInAs layer 26, a p-InP clad layer 27 covering the ridge stripe, and a p ⁺ -GaInAs contact layer 28. P-AlIn forming ridge stripe
On both sides of the As layer 26, an Al oxide layer 29 obtained by oxidizing Al in the AlInAs layer forms a current confinement structure.

The p-side electrode 3 is formed on the mesa via an insulating film 31 formed so as to form a window on the contact layer 28.
2 is provided, and an n-side electrode 33 is provided on the back surface of the InP substrate 21.

The light receiving element 41 is shown in FIGS.
As shown in FIG. 2B, n-AlInA having a thickness of 100 nm is formed.
Al oxide layer 3 in which Al is oxidized over all layers of s layer 22
0, a two-step mesa structure having a mesa from the upper layer of the InP substrate 21 in addition to the same mesa as the laser element 40, and an n-side electrode 35 on the n-InP clad layer 23. Except that it is formed and the p-side electrode 34 is formed only on the upper part of the mesa, it has the same laminated structure as the laser element 40. Light receiving element 4
1 is electrically separated from the semiconductor substrate 21 by the Al oxide layer 30 and is electrically separated from the laser element 40 by the separation groove 42.

As described above, since the light receiving element 41 is electrically independent of the laser element 40, the semiconductor optical integrated device 39 of the present embodiment has a circuit as shown in FIG. With this configuration, the laser element 40 and the light receiving element 41 can be operated by a single power supply.

The embodiment this embodiment of a method for manufacturing a semiconductor optical integrated device is an example embodiment of the manufacturing method according to the present invention a semiconductor optical integrated device, FIG. 3 (a) (b),
4 (a) and (b), FIGS. 5 (a) and (b), and FIG.
FIGS. 3A and 3B are cross-sectional views illustrating the layer structure of each step when fabricating the semiconductor optical integrated device according to the embodiment. 4, 5, and 6, (a) shows a laser element forming region, and (b) shows a light receiving element forming region. In the method of the present embodiment, first, as shown in FIG.
A film thickness of 100 on the InP substrate 21 by MOCVD;
nm-AlInAs layer 22, n-InP clad layer 23, GRIN-SCH-MQW active layer 24, and p-
The InP cladding layers 25 are sequentially laminated.

Next, the middle of the p-InP cladding layer 25 is removed by etching by a general photolithography and dry etching by RIBE, and a width of 2.5 p.
A μm ridge stripe is formed. After that, MOCV
As shown in FIG. 3B, a p-AlInA film having a thickness of 50 nm is formed on the entire surface of the wafer including the ridge stripe by the D method.
s layer 26, p-InP clad layer 27, and p ⁺ -Ga
The InAs contact layers 28 are sequentially stacked.

Next, the contact layer 28, the p-InP cladding layer 27, the p-AlInAs layer 26, the p-InP cladding layer 25, the MQW active layer 24, and the dry etching by general photolithography and RIBE are used.
Then, a part of the n-InP cladding layer 23 is removed by etching to form a ridge stripe having a width of 10 μm as shown in FIG.

In the region where the light receiving element is formed, as shown in FIG. 4B, the n-InP cladding layer 23 and the n-Al
The InAs layer 22 and the n-InP substrate 21 are separately removed halfway to form a ridge having a width of 20 μm.

Next, the substrate is subjected to a heat treatment at a temperature of 500 ° C. for about 4 hours in a reaction furnace into which steam is introduced using nitrogen as a carrier gas. The heat treatment utilizes the fact that the oxidation rate of the AlInAs layer depends on the layer thickness, and the oxidation rate increases as the layer thickness increases.
An Al oxide layer 29 used as a current confinement layer and an Al oxide layer 30 used for electrical isolation of the light receiving element 41 are formed together. That is, in the AlInAs layer 22 and the AlInAs layer 26, the AlInAs layer 22 has a thickness of 100 nm with respect to the thickness of the AlInAs layer 26 of 50 nm.
m, and an AlInAs layer 26 on the side surface of the ridge.
Oxidation rate is further reduced due to the reduced thickness. As a result, the oxidation of the Al oxide layer 29 for current confinement is reliably stopped at the side surface of the ridge, and the entire layer of the AlInAs layer 22 is oxidized over the entire region. As described above, by performing the heat treatment, the AlIn
The As layers 22 and 26 are oxidized to form Al oxide layers 2 respectively.
9 and 30, as shown in FIGS. 5 (a) and 5 (b),
It is formed in a laser element formation area and a light receiving element formation area.

Next, a separation groove 42 for electrically separating the laser element 40 from the light receiving element 41 is formed. At this time, at least the surface of the groove on the laser side needs to be formed substantially perpendicular to the substrate in order to form a laser cavity mirror. The vertical groove can be easily formed by dry etching using RIBE or wet etching using a hydrochloric acid-based etchant. Also, as a countermeasure against the return light, the reflection of the laser light can be prevented by forming the surface of the groove on the light receiving element side obliquely.

Subsequently, the InP substrate 21 is polished to a thickness of about 100 μm. In the laser element 40, as shown in FIG. 6A, an insulating film 31 is formed on the upper surface of the mesa so as to open a window on the contact layer 28, and then a p-side electrode 32 is formed on the insulating film 31. Further, the n-type electrode 33 is n-
It is formed on an InP substrate 21. On the other hand, in the light receiving element 41,
As shown in FIG. 6B, an insulating film 31 is formed by opening a window on a part of the n-InP cladding layer 23 and on the contact layer 28, and then the p-side electrode 3 is formed on the insulating film 31.
4 is formed. Further, the exposed n-InP cladding layer 2
An n-side electrode 35 is formed on 3.

In the integrated device manufactured as described above, the light receiving device 41 is shared by the AlP layer 30 and the common InP substrate 21.
Is electrically separated from the laser element 40 and the light receiving element 4 by a single power supply when mounted on a package.
1 can be operated. Also, needless to say, since the active layer of the laser element and the light absorption layer of the light receiving element are formed by the same process, there is no need to perform alignment during mounting. The separation groove 42, that is, the element isolation region 42
Alternatively, a DBR reflector made of air and a semiconductor can be formed.

[0027]

According to the structure of the present invention, in a semiconductor optical integrated device in which a laser element and a light receiving element which are electrically separated from each other by an element isolation region are monolithically formed on a common semiconductor substrate, And forming an electrode of one of the light-receiving elements on the back surface of the semiconductor substrate, and
By electrically separating the other element from the semiconductor substrate by an electrical separation band, a semiconductor optical integrated device that can be operated by a single power supply is realized. The method of the present invention comprises:
An optimum method for manufacturing a semiconductor optical integrated device according to the present invention is realized.

[Brief description of the drawings]

FIG. 1A is a sectional view showing a layer structure of a laser element and a light receiving element of a semiconductor optical integrated device according to an embodiment of the present invention;
(B) is a circuit diagram of a laser element and a light receiving element.

2A is a cross-sectional view taken along a line II of the laser device of FIG. 1, and FIG. 2B is a cross-sectional view taken along a line II-II of the light receiving device of FIG.
FIG.

FIGS. 3A and 3B are cross-sectional views each showing a layer structure in each step when manufacturing a semiconductor optical integrated device according to an embodiment.

4 (a) and FIG. 4 (b) correspond to FIG.
FIG. 5B is a cross-sectional view illustrating the layer structure in each step of manufacturing the semiconductor optical integrated device according to the embodiment example, following FIG. FIG. 4A shows a laser element forming area, and FIG. 4B shows a light receiving element forming area.

5 (a) and FIG. 5 (b) correspond to FIG.
4 is a cross-sectional view showing a layer structure in each step when manufacturing the semiconductor optical integrated device according to the embodiment. FIG.
5A shows a laser element forming region, and FIG. 5B shows a light receiving element forming region.

6 (a) and FIG. 6 (b) correspond to FIG.
4 is a cross-sectional view showing a layer structure in each step when manufacturing the semiconductor optical integrated device according to the embodiment. FIG.
6A shows a laser element forming region, and FIG. 6B shows a light receiving element forming region.

FIG. 7A is a cross-sectional view showing a layer structure of a laser element and a light receiving element of a conventional semiconductor optical integrated device, and FIG. 7B is a circuit diagram of the laser element and the light receiving element.

8 is a sectional view of a section parallel to the separation groove taken along the line III-III in FIG. 7A.

[Explanation of symbols]

Reference Signs List 1 n-InP substrate 2 n-InP cladding layer 3 GaInAsP active layer 4 p-InP cladding layer 5 p ⁺ -GaInAs contact layer 6 p-side electrode 7 n-side electrode 8 separation groove 10 laser element 11 light-receiving element 12 p-InP layer 13 n-InP layer 20 conventional semiconductor optical integrated device 21 n-InP substrate 22 n-AlInAs layer 23 n-InP cladding layer 24 GRIN-SCH-MQW active layer 25 p-InP cladding layer 26 p-AlInAs layer 27 p- InP cladding layer 28 p-GaInAs contact layer 29, 30 Al oxide layer 31 insulating film 32 p-side electrode 33 n-side electrode 34 p-side electrode 35 n-side electrode 39 semiconductor optical integrated device of embodiment 40 laser element 41 light receiving element 42 Separation groove

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeharu Yamaguchi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Akihiko Kasukawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Furukawa Electric Co., Ltd. (reference) 5F073 AA13 AA46 AA74 AB13 CA12 CB02 DA05 DA22 DA25

Claims (3)

[Claims] 1. A semiconductor optical integrated device having a laser element and a light receiving element which are monolithically formed on a common semiconductor substrate and are electrically separated from each other by an element isolation region. The electrode of one of the elements is formed on the back surface of the semiconductor substrate, and the other element is
A semiconductor optical integrated device, which is electrically separated from a semiconductor substrate by an electrical separation band. 2. An electrical separation zone is formed by an Al oxide layer,
2. The semiconductor optical integrated device according to claim 1, wherein the current confinement structure is formed of an Al oxide layer. 3. A method of manufacturing a semiconductor optical integrated device having a laser element and a light receiving element which are monolithically formed on a common semiconductor substrate and are electrically separated from each other by an element isolation region. A first oxidized layer made of an Al-containing compound semiconductor on the semiconductor substrate in both the region and the light receiving element formation region; and a second oxidized compound semiconductor formed on the first oxidized layer and made of the Al-containing compound semiconductor Forming a double heterostructure including at least a layer to be oxidized; forming a first ridge stripe exposing a second layer to be oxidized in a laser element forming region; Forming a second ridge stripe that is wider than the first ridge stripe and exposes the first oxidized layer, in addition to forming the first ridge stripe; In a laser element forming region, the ridge stripe side portion of the second oxidized layer is applied, and in the light receiving element forming region, all the first oxidized layer and the ridge of the second oxidized layer are formed. Oxidizing a side portion of the stripe.