JPH08313745A - Semiconductor optical integrated circuit and its production - Google Patents

Abstract

PURPOSE: To make it possible shut off the stray light to a photodetector by forming a groove deeper than a semiconductor light absorption layer around the photodetector and covering the flanks of this groove exclusive of the photodetecting part of the photodetector with opaque thin films. CONSTITUTION: The groove 51 which limits the current implantation region of a distribution feedback type semiconductor laser 2 part and the groove 52 which shuts off the stray light to the semiconductor photodetector 3 are formed by etching in a head for a one-chip interference measurement formed by integrating a distribution feedback type semiconductor laser 2, a semiconductor photodetector 3 and an optical waveguide 4 on a GaAs semiconductor substrate 1 by using an integration process applying the disordering of, for example, a quantum well structure. The groove 52 is formed deeper than an undoped GaAs quantum well layer (a light absorption layer to the semiconductor photodetector 3) and the flanks thereof exclusive of the photodetecting part of the photodetector 3 are coated with upper electrodes as opaque thin films. As a result, the semiconductor photodetector 3 is electrically insulated and the stray light from distribution feedback type semiconductor laser to the semiconductor photodetector is shut off.

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 circuit.

[0002]

2. Description of the Related Art Conventionally, in an optical measuring device for detecting weak light, it is an important issue to remove stray light which is light other than signal light incident on a light receiving element, and an optical shield plate or a light absorber is used. Stray light incident on the light receiving element is excluded.

[0003]

This problem is also an important issue in a semiconductor optical integrated circuit in which various optical elements are integrated on a semiconductor substrate, and particularly a semiconductor in which a light emitting element and a light receiving element are formed on the same substrate. This is a big problem in optical integrated circuits.

In view of the above points, an object of the present invention is to block stray light to the light receiving element by forming a deep groove around the light receiving element or the light emitting element and covering the side surface with an opaque thin film. It is to realize a semiconductor optical integrated circuit that can be performed. Another object of the present invention is to provide a method for manufacturing a semiconductor optical integrated circuit capable of blocking stray light to the light receiving element by forming a deep groove around the light receiving element or the light emitting element and covering the side surface with an opaque thin film. To provide.

[0005]

In order to achieve such an object, according to the first invention of the present application, in a semiconductor optical integrated circuit in which a light emitting element and a light receiving element are formed on the same substrate, the periphery of the light receiving element is provided. Is characterized in that a groove deeper than the semiconductor light absorption layer is formed, and the side surface of the groove is formed so as to be covered with an opaque thin film except the light receiving portion of the light receiving element. In a second invention of the present application, in a semiconductor optical integrated circuit in which a light emitting element and a light receiving element are formed on the same substrate, a groove deeper than a semiconductor active layer is formed around the light emitting element, and a side surface of the groove is an optical element. It is characterized in that it is formed so as to be covered with an opaque thin film except the output portion.

In the method invention of the present application, at least a cladding layer and at least a cladding layer are formed on a GaAs substrate by a semiconductor crystal growth method.
A step of growing a GRIN layer, a quantum well layer, a GRIN layer, and a guide layer; a step of forming a diffraction grating for a semiconductor laser and a rib type optical waveguide in the guide layer; The mask layer is masked, and impurities are ion-implanted into the other portions, and a clad layer and a cap layer are grown on the guide layer on which the diffraction grating and the rib type optical waveguide are formed by a semiconductor crystal growth method. A step of etching the groove structure to electrically insulate the electrodes of the semiconductor light receiving element and to block stray light to the semiconductor light receiving element, and then to the semiconductor laser and the semiconductor light receiving so as to cover the side surface of the groove structure. The method is characterized by including a step of forming an upper electrode and a lower electrode in the device.

[0007]

Function: A groove is formed around the light receiving element or the light emitting element, and the side surface thereof is covered with an opaque thin film. This blocks stray light to the light receiving element.

[0008]

The present invention will be described in detail below with reference to the drawings.
Here, a distributed feedback semiconductor laser (DFB-LD: Distributed Feedback-L) is formed on a GaAs semiconductor substrate by using an integration process which applies disordering of a quantum well structure.
aser diode), a semiconductor light receiving element, and a one-chip interferometric measuring head in which an optical waveguide is integrated.

FIG. 1 is a block diagram showing an example of the one-chip interference measuring head. In the figure, 1 is a GaAs semiconductor substrate, 2 is a distributed feedback semiconductor laser, 3 is a semiconductor light receiving element, 4 is an optical waveguide, 5 and 6 are lenses, and 7 is a prism.

The output light of the distributed feedback semiconductor laser 2 is divided into two by the optical waveguide 4, one of which directly goes to the semiconductor light receiving element 3 by the curved waveguide and the other of which is emitted from the semiconductor substrate 1 and collimated by the output lens 5 to be a prism. Head to 7.
The output light reflected by the prism 7 is condensed by the input lens 6, again enters the optical waveguide 4 on the semiconductor substrate 1, and goes to the semiconductor light receiving element 3. Two lights, that is, the output light guided through the curved waveguide of the distributed feedback semiconductor laser 2 and the output light reflected and returned by the prism 7 are combined before the semiconductor light receiving element 3, and the semiconductor light receiving element 3 receives the light. An interference signal of both output lights is obtained.

Next, the manufacturing process will be described. (1) As shown in the sectional view of FIG. 2, an n-type GaAs substrate 11 is formed by a semiconductor crystal growth method, for example, a metal organic chemical vapor deposition method.
N-type GaAs buffer layer 12 (thickness 0.5 μ
m), the n-type Al _0.6 Ga _0.4 As cladding layer 13 (thickness 1.5 μm), and the undoped Al _x Ga _1-x As (x =
0.6-0.3) GRIN layer 14 (thickness 150 nm)
And the undoped GaAs quantum well layer 15 (thickness 10 n
m) and undoped Al _x Ga _1-x As (x = 0.3 to
0.6) GRIN layer 16 (thickness 150 nm) and carrier block layer 17 of undoped Al _0.6 Ga _0.4 As
A guide layer 18 (thickness 30 nm) and Al _0.15 Ga _0.85 As (thickness 20 nm) are grown at a temperature of 780 ° C.
In this case, the buffer layer 12 and the carrier block layer 17
Is not always necessary. Undoped GaAs
The quantum well layer 15 operates as an active layer in the distributed feedback semiconductor laser 2 and operates as a light absorption layer in the semiconductor light receiving element 3.

(2) A diffraction grating 21 for a distributed feedback type semiconductor laser and a rib type optical waveguide 22 are formed in the guide layer 18 by electron beam exposure and etching with sulfuric acid / hydrogen peroxide mixture. A top view after etching is shown in FIG.
And cd cross sections are shown in FIGS. 4 and 5, respectively. The etching at this time is controlled so that the guide layer 18 is completely etched and stopped in the carrier block layer 17. As a result, the difference between the etched portion and the non-etched portion is the presence or absence of the guide layer, and the difference in the refractive index due to etching is determined by the thickness of the guide layer.

(3) As shown in FIG. 6, masks (hatched portions) 31a and 31b are applied to the portion composed of the distributed feedback semiconductor laser 2 and the semiconductor light receiving element 3, and the other portions have energy of 100 keV and a dose of 1 An impurity such as Si is ion-implanted at × 10 ¹³ cm ^-2 .

(4) A p-type Al _0.6 Ga _0.4 As clad layer 41 (thickness: 1. is formed on the guide layer 18 on which the diffraction grating 21 and the rib type optical waveguide 22 are formed by the metal organic chemical vapor deposition method).
5 μm) and the p-type GaAs cap layer 42 (thickness 0.3
μm) at a temperature of 750 ° C. Since the Si impurity promotes the interdiffusion of Al and Ga, the temperature rise at this time makes the quantum well in the portion where Si ions are implanted disorder. Due to this disordering, the absorption edge of the quantum well shifts to the shorter wavelength side, and the Si ion-implanted portion becomes a low-loss waveguide. The cd cross section in FIG. 3 is shown in FIG. The GaAs quantum well layer 151 indicated by the dotted line in the figure is disordered.

(5) Groove structure 5 having a depth of 1.6 μm for limiting the current injection region of the distributed feedback semiconductor laser 2 portion 5
1 and the electrode of the semiconductor light receiving element 3 are electrically insulated, and a depth of 3 μm for blocking stray light to the semiconductor light receiving element 3
Etch the trench structure 52. Groove structure 51, 52
A top view of the above is shown in FIG.

[0016] (6) and the deposition of the SiO ₂ film 61, a distributed feedback semiconductor laser 2 and the semiconductor light-receiving element 3 portion of the SiO ₂ film 6
1 is etched, and then the distributed feedback semiconductor laser 2 and the semiconductor light receiving element 3 have an upper electrode 62 (the upper electrode of the distributed feedback semiconductor laser 2 is 62a and the upper electrode of the semiconductor light receiving element 3 is 62b) and the lower electrode. 63 is formed. 9 is a top view of the upper electrodes 62a and 62b, and FIGS. 10 and 11 are sectional views taken along line ef and line gh in FIG. As shown in FIGS. 9 and 11, the side surface of the groove structure 52 having a depth of 3 μm is entirely covered with the upper electrode 62 except for the light receiving portion of the semiconductor light receiving element 3, whereby strong light emission is achieved. It is possible to block stray light emitted from the distributed feedback semiconductor laser 2 as a source in the lateral direction and entering the light receiving portion.

As described above, the groove structure 52 having a depth of 3 μm whose side surface is covered with the upper electrode 62 has an effect of electrically insulating the semiconductor light receiving element 3 and blocking stray light to the semiconductor light receiving element 3. This makes it possible to measure a weak interference signal. Further, by using the upper electrode as the opaque thin film, the opaque thin film for blocking stray light can be formed by the same process as the formation of the upper electrode, and the manufacturing process can be simplified.

The present invention is not limited to the above embodiment. For example, in the above embodiment, a groove structure whose side surface is covered with an opaque thin film is formed around the light receiving element to block stray light. On the contrary, the groove structure is formed around the semiconductor light emitting element 3. A structure for blocking stray light may be used. Also, both may be used in combination.

[0019]

As described above, according to the present invention, in a semiconductor optical integrated circuit, a deep groove is formed around a light receiving element or a light emitting element, and the side surface thereof is covered with an opaque thin film so that the light receiving element is electrically connected. It is possible to electrically insulate and to block stray light to the light receiving element, which makes it possible to measure a weak interference signal. Also, by using the upper electrode as an opaque thin film,
An opaque thin film for blocking stray light can be formed by the same process as the formation of the upper electrode, and the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a semiconductor optical integrated circuit according to the present invention.

FIG. 2 is a sectional view of the semiconductor optical integrated circuit shown in FIG.

FIG. 3 is a top view after etching treatment in a manufacturing process of a semiconductor optical integrated circuit.

FIG. 4 is a sectional view taken along line ab in FIG.

5 is a sectional view taken along line cd in FIG.

FIG. 6 is a view showing the shape of an ion implantation mask.

FIG. 7 is a diagram showing disordering of a quantum well layer.

FIG. 8 is a top view of the groove structure.

FIG. 9 is a diagram showing an upper electrode.

10 is a sectional view taken along line ef in FIG.

11 is a sectional view taken along line gh in FIG.

[Explanation of symbols]

 1 GaAs semiconductor substrate 2 distributed feedback semiconductor laser 3 semiconductor light receiving element 4 optical waveguide 5, 6 lens 7 prism 11 GaAs substrate 12 buffer layer 13 clad layer 14 GRIN layer 15 quantum well layer 16 GRIN layer 17 block layer 18 guide layer 21 diffraction Lattice 22 Rib type optical waveguide 31a, 31b Mask 41 Cladding layer 42 Cap layer 51, 52 Groove 62, 62a, 62b Upper electrode 63 Lower electrode 151 Disordered quantum well layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // H01L 31/10 H01L 31/10 A

Claims (4)

[Claims] 1. In a semiconductor optical integrated circuit in which a light emitting element and a light receiving element are formed on the same substrate, a groove deeper than a semiconductor light absorbing layer is formed around the light receiving element, and a side surface of the groove is a light receiving element of the light receiving element. A semiconductor optical integrated circuit characterized by being formed so as to be covered with an opaque thin film except for a part. 2. In a semiconductor optical integrated circuit in which a light emitting element and a light receiving element are formed on the same substrate, a groove deeper than a semiconductor active layer is formed around the light emitting element, and a side surface of the groove except a light output portion. A semiconductor optical integrated circuit characterized by being formed so as to be covered with an opaque thin film. 3. The semiconductor optical integrated circuit according to claim 1 or 2, wherein the opaque thin film is made of the same material as an electrode used in the semiconductor optical integrated circuit. 4. A method for manufacturing a semiconductor optical integrated circuit in which a light emitting element and a light receiving element are formed on the same substrate, wherein at least a cladding layer, a GRIN layer, and a quantum layer are formed on a GaAs substrate by a semiconductor crystal growth method. Well layer and GRI
Growing an N layer and a guide layer; forming a diffraction grating for a semiconductor laser and a rib type optical waveguide in the guide layer; masking a portion including the semiconductor laser and the semiconductor light receiving element; A step of ion-implanting impurities into the portion; a step of growing a clad layer and a cap layer on the guide layer on which the diffraction grating and the rib type optical waveguide are formed by a semiconductor crystal growth method; and an electrode of the semiconductor light receiving element. Etching the groove structure to electrically insulate the semiconductor and block stray light to the semiconductor light receiving element, and then form the upper electrode and the lower electrode on the semiconductor laser and the semiconductor light receiving element so as to cover the side surface of the groove structure. A method of manufacturing a semiconductor optical integrated circuit, comprising: