JPS62141507A - Optical integrated circuit and its production - Google Patents

Abstract

PURPOSE:To eliminate the need for intricate optical alignment between semiconductors and dielectric materials by providing a dielectric crystal layer including optical waveguides and semiconductor epitaxial crystal layer including at least either of a light emitting region and light receiving region on a semiconductor substrate. CONSTITUTION:This optical integrated circuit consists of a thin LiNb2O3 film 9 and a semiconductor epitaxial layer consisting of InP/InGaAsP on the InP substrate 8. A Ti-diffused optical waveguide 11 is formed on the thin LiNb2O3 film 9 and a directional coupler having a control electrode 12 is formed particularly in an optical switch part 7. The semiconductor epitaxial layer forms a DFB type laser having a grating 13 in a light emitting part 6 and a P-N junction type photodiode in a light receiving part. The laser light oscillated in the light emitting part 6 is made incident on the Ti-diffused optical waveguide 11 at both ends and arrives at the light receiving part 5 on one side to make monitoring of the light output. Said light arrives at the optical switch part on the other end and after the optical path is changed over, the light is emitted from exit ends 14, 14'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical integrated circuit that integrates a waveguide type optical device using a dielectric and a light emitting/light receiving device using a semiconductor, and a method for manufacturing the same.

Conventional technology L 1Nb2O. The dielectric material represented by % can form an optical waveguide with very low loss of 1 dB/cm or less by a method such as Ti diffusion.

This material also has a large electro-optic effect, making it ideal for optical modulators and
Optical switches and other devices have already achieved practical properties. In addition, this material can utilize nonlinear optical effects to produce second harmonics (
! 3HG) can also be expected as an element.

On the other hand, semiconductor materials represented by group ■-V compound semiconductors, including their mixed crystals, have light emitting and light receiving functions.

It is the most preferred material for optical/electrical conversion elements.

Therefore, a hybrid optical integrated circuit using these two materials can be expected to have a wide range of applications, such as a semiconductor laser with an optical switch and a short-wave optical laser using SHG.

Normally, methods for optically coupling a photoelectric conversion element such as a semiconductor laser and an optical waveguide element include via a 7-eyeper or via a lens system, but this is due to the preservation of the optical wavefront and the optical stability. Lacks sex. From the standpoint of mode shape and optical stability at the end facets, it is most preferable to optically couple the semiconductor laser and the dielectric optical waveguide in direct proximity.

As an example, FIG. 4 shows a hybrid optical integrated circuit in which a semiconductor laser and a guiding waveguide are integrated.

Here, 1 is an SL submount, on which a semiconductor layer 2 and a dielectric waveguide element 3 are mounted and fixed. S
i. The mount 1 is formed with a step so that the optical axes of the active layer 2' of the semiconductor laser 2 and the optical waveguide 3' of the dielectric optical waveguide element 30 are aligned. Such a configuration allows direct coupling between the semiconductor laser and the leading waveguide.

However, with this method, it is very difficult to form a step on the submount with enough precision to align the optical axis of a pixel element with a thickness of several hundred microns, and the error when fixing it is inevitably large.

As a means to overcome such difficulties in alignment, attempts have been made to form the entire region including the optical waveguide using a compound semiconductor. Although this method is most desirable from the standpoint of integration, a compound semiconductor guided waveguide has a larger waveguide loss than a dielectric guided waveguide such as LiNbO3, and the material-specific electro-optic effect necessary for optical switch functions is also small.

The best way to create an optical integrated circuit that does not impair the characteristics of individual elements and does not require complicated optical alignment is to form an electric shield layer and a semiconductor layer on the same substrate. However, LiNb2 is placed on a semiconductor substrate such as InP.
It is almost impossible to form an O3 epitaxial layer or an InP epitaxial layer on a L i Nb2 OJ plate by normal means due to the difference in crystal structure and lattice constant between the two.

Problems to be Solved by the Invention As stated above, it is extremely difficult with conventional techniques to obtain an optical integrated circuit that takes advantage of the advantages of dielectric and semiconductor materials and does not require a 7-line complex optical system. I got it.

Means for Solving the Problems In order to overcome the above-mentioned problems, the present invention mounts or fixes a dielectric crystal on a portion of a semiconductor substrate, epitaxially grows a semiconductor on the other portion, and provides optical guidance on the dielectric portion. A light receiving/emitting part and, if necessary, an electric confectionery are formed in the wave path and semiconductor part, and the light emitting part/light receiving part and the optical waveguide are formed on the same optical axis in an optical integrated circuit.

Operation By using the above-mentioned means, the dielectric optical waveguide device and the semiconductor photoelectric conversion device can be improved without impairing their characteristics when used alone.
This makes it possible to easily provide an optical integrated circuit that does not require difficult alignment.

EXAMPLES Below, examples of the present invention will be described in which an InP-based material is used as the semiconductor material and l-1Nboat- is used as the dielectric material.

FIG. 1 shows an optical integrated circuit according to a first embodiment of the present invention. This is a light emitting device with a light output monitor mechanism and a light switch. Figure 1A shows its plan view, and Figure 1B shows the
-M' shows a cross-sectional structural diagram. Here, 6 is the light receiving part,
6 is a light emitting section, and 7 is a light switch section. This integrated circuit dI
LiNb2O7 film 9 on nP substrate 8,! : InP
/ Consists of an InGaAsP-based semiconductor epitaxial layer 10. A Ti diffused optical waveguide 11 is formed on the LiNb2O,- film 9, and in particular, a directional coupler having a control electrode 12 is formed in the optical switch section 7. Further, the semiconductor epitaxial layer forms a DFB type laser equipped with a grating 13 in the light emitting part 6, and a Pa junction type 7-odd diode in the light receiving part. The laser beam oscillated by the light emitting section 6 passes through the Ti diffused optical waveguides 11 at both ends.
On one side, the light is entrusted to the light receiving section 5 to monitor the optical output, and on the other side, it reaches the optical switch section, and after the optical path is switched, it is emitted from the output ends 14, 14'.

The feature of this device is that it has a dielectric crystal layer and a semiconductor epitaxial layer on a semiconductor substrate, an optical waveguide including an optical switch is formed in the dielectric part, a light receiving/emitting element is formed in the semiconductor part, and both of them use the same light. It is to exist on the axis.

Optical integrated circuits with this structure can take full advantage of the features of dielectrics and semiconductors, do not require a complex optical system, are optically stable, and have low coupling loss between the semiconductor laser and optical waveguide. , propagation loss in the optical waveguide and loss in the optical switch can be minimized.

FIG. 2 shows the manufacturing process of the optical integrated circuit of this example.

First, on the 'nP substrate 8, a LINbO3 crystal 9 having a thickness (~10 μm) that can be linked with the S/N is mounted or fixed. As a method of fixing Li, high power laser light is
There is a method in which the Nbo3/InP interface is irradiated to directly fuse the two, or a metal layer or the like is used as an intermediate layer and is similarly fused as a binder between the two (FIG. 2A). Next, L zNbO3
Crystal 9f, thickness suitable for processing in the following process (several 1
The film is made thinner by polishing to a thickness of 0 μm or less (Figure 2B).

This step is not necessarily essential. Next, T1 diffusion is performed at necessary locations on the LiNbo3 crystal 9 to form an optical waveguide 11 (FIG. 2C).

Next, the LiNbO in the area of the light receiving part 52 and the light emitting part 6 is removed by dry etching to expose the surface of the InP substrate 8 (FIG. 2D). If more is needed, LiNbO3
The exposed In formed during fixing and etching
The defect layer on the P surface can be removed by wet etching using aqua regia, Bx methanol, or the like.

Below, InP is applied to the exposed part of the InP substrate surface on the InP substrate 8 partially masked with LiNbO3e.
Epitaxial growth of the P/InGaAsP system is performed multiple times if necessary to form a light receiving part and a light emitting part (second
Figure F). There are two epitaxial growth methods: vapor phase growth and liquid phase growth. In vapor phase growth methods such as MOCVD+MBE, a single crystal grows even on LiNbO3, but in liquid phase growth, it grows only on the exposed part of the InP surface. No crystal growth. For this reason, it is best to perform epitaxial growth using a liquid phase growth method since the growth rate is even faster. Optical waveguide 9
In order to match the optical axes of the semiconductor laser in the light emitting section 6 and the photodiode in the light receiving section 5 more precisely, the second step is to increase the film thickness (LiNbO59 and InPl 0') as shown in Figure E.
grow epitaxially. After further polishing and flattening the surface of the 1nP epitaxial layer 15 on the LiNbO39 surface to the same height, the InP epitaxial layer 9 is etched to a depth of about 1 to 2 μm so that the film thickness can be controlled in subsequent epitaxial growth. do.

Next, a grating 13 is formed on the InP surface of the light emitting section 6, and then a growth layer 10 is formed by InGaAsP/InP multilayer epitaxial growth to form a DFB type laser. Furthermore, an InGaAs layer is epitaxially grown on the light receiving part 5, and Zn, which is a P-type impurity, is partially diffused into the diffusion region 16.
to form a photodiode (FIG. 2F).

In such a process, the light emitting part 6. Light receiving section 5. and the optical waveguide 11 can be easily formed on the same optical axis. L is formed on the InP substrate 8 in the process before epitaxial growth.
Even when the iNbO3 crystal 9 is simply mounted without being fixed, the presence of the semiconductor epitaxial layer 10 in the subsequent epitaxial growth makes it possible to mechanically fix the 9LiF crystal 039, and no axis misalignment will occur thereafter.

Finally, electrode 12' on the necessary part! By forming the i-formation, it is possible to fabricate an optical integrated circuit in which a semiconductor laser/optical switch and a monitoring photodiode shown in FIG. 1 are integrated.

The manufacturing method for such optical integrated circuits is InP/L.
A semiconductor and a dielectric can be easily integrated on the same substrate without using the difficult method of heterogeneous epitaxial growth between iNbO3.

Next, a second embodiment of the present invention is shown in FIG. This is a second harmonic generation (SHG) device that integrates a semiconductor laser and an L 1NbO3 optical waveguide. The characteristics of L x Nbo3 are not only that it has a large electro-optic effect, but also that it has a nonlinear optical effect and is transparent to the generated second harmonic, making it most preferable as a material for generating short wavelength laser light. InGaA
When a semiconductor laser (wavelength 1.2 to 1.4 μm) using s+P/InP material is used as the primary light, o, eμ
The second harmonic of the m band is AI! 0.4 for semiconductor laser f (wavelength 0.8 to 0.9 μm) made of GaAs/GaAs material
A second harmonic in the μm band is obtained. In the optical integrated circuit shown in FIG. 3, an InP substrate 8 is formed with a LiNbO3 crystal 9 including an optical waveguide 11, and an InG film forming an embedded semiconductor laser.
It consists of an aAsP/I nP epitaxial layer 10° and an electrode 12 for injecting current into the laser. This structure is obtained by forming the output end by cleaving after the manufacturing process of FIGS. 2A-F. By integrating the semiconductor laser and the LiNbO3 optical waveguide in this manner, high coupling efficiency can be obtained, and the second harmonic can be generated with high efficiency.

Although InP is used as the semiconductor in this example, other semiconductors such as GaAm may be used, and Li may be used as the dielectric.
Although NbO3 is used, it goes without saying that other dielectric materials such as PLZT may also be used.

Effects of the Invention As described above, the optical integrated circuit of the present invention has a structure including a dielectric crystal layer including a guiding waveguide and a semiconductor epitaxial crystal layer including at least one of a light emitting region and a light receiving region on a semiconductor substrate. A circuit is obtained by a manufacturing method in which a dielectric crystal is mounted or fixed on a part of a semiconductor substrate, and then a semiconductor T is epitaxially grown on an unexposed part of the semiconductor substrate, whereby a semiconductor and a dielectric are used alone. Accordingly, it is possible to provide an optical integrated circuit that has high coupling efficiency without impairing the optical performance, does not require complicated optical alignment between the two, and has high coupling efficiency.

[Brief explanation of drawings]

FIG. 3 is a process diagram showing the manufacturing process of the same integrated circuit; FIG. 3 is a perspective view of an optical integrated circuit according to the second embodiment of the present invention;
The figure is a cross-sectional view of a conventional optical integrated circuit. 5... Light receiving section, 6... Light emitting section, 7...
....Optical switch part, 8...InP substrate, 9
・・・・・・L i! fboa thin film, 10...
InP/InGaAsP epitaxial layer, 11
......τi diffused optical waveguide. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 (A> (B) Figure 2 (A) (C) Figure 2 CD) (E)

Claims (6)

[Claims] (1) An optical integrated circuit comprising, on a semiconductor substrate, a dielectric crystal layer including an optical waveguide and a semiconductor epitaxial crystal layer including at least one of a light emitting region and a light receiving region. (2) The optical integrated circuit according to claim 1, wherein the optical waveguide and the light emitting region or the light receiving region are on the same optical axis. (3) As a semiconductor substrate and semiconductor epitaxial layer
The optical integrated circuit according to claim 1, which uses a III-V group compound semiconductor. (4) LiNbO_3 or Li as dielectric crystal layer
The optical integrated circuit according to claim 1, which uses Ta_2O_3. (5) A step of mounting or fixing a dielectric crystal on a semiconductor substrate, a step of forming an optical waveguide on the dielectric crystal, and a step of removing the dielectric crystal in a part of the semiconductor substrate by etching. A method for manufacturing an optical integrated circuit, comprising the steps of: exposing the semiconductor substrate; and epitaxially growing a semiconductor on the exposed region of the semiconductor substrate. (6) After growing a semiconductor epitaxial layer thicker than the thickness of the dielectric crystal, the dielectric crystal surface and the semiconductor epitaxial layer surface are made to have the same height by polishing, and the semiconductor epitaxial layer is etched within 5 microns from the surface. 6. The method of manufacturing an optical integrated circuit according to claim 5, wherein the semiconductor epitaxial layer is then grown again.