JPH04163983A - Semiconductor optical element - Google Patents

Abstract

PURPOSE:To increase the degree of freedoms of a design of an optical element having a light emission and a light reception by forming first and second regions to be formed to become an active layer or a light absorption layer in the same waveguide, and providing means for independently controlling the first and second regions. CONSTITUTION:Since electric connections are conducted in a passage of a p-type electrode 22, a p-type clad layer 18, an active layer 18, a first n-type clad layer 19 and an n-type electrode 24 in a light emitting unit, if a forward bias is applied between the electrodes 22 and 24, a current flows in this passage, carrier is injected to an active layer 14, a population inversion takes place, and an inductive emission occurs. On the other hand, in a light receptor, electric connections are conducted in a passage of the electrode 22, the layer 18, a light absorption layer 16, a second n-type clad layer 21, and an n-type electrode 23. Accordingly, if a reverse bias is applied between the electrodes 22 and 23, a light is detected in the layer 16.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor optical device, and more specifically, it is expected to serve as a semiconductor light emitting and light receiving device as well as a component of a system with new functions. Related to semiconductor optical devices.

[Prior Art] Several semiconductor optical devices that have both a semiconductor light-emitting device and a light-receiving device have been proposed in the past, and are applied to various systems as multifunctional devices.

The most common conventional example is shown in FIG. In this conventional example,
By providing a parallel groove 78 with a vertical end surface beyond the active layer 75 in a part of the resonator of the semiconductor laser element, and further providing independent electrodes 79a and 79b in each part (80 is a common electrode). , a light emitting section 76 formed on one side;
It is separated into a light receiving part 77 which is formed on the other side and receives light emitted from the light emitting part 76 and inputted to the active layer 75 again. In this conventional example, the same active layer 75 is used to partially share the functions of light emission and light reception.
The optical signal from the light receiving section 77 is returned to the light emitting section 76 and APC is performed.
It has been proposed to perform (automatic light emission amount control).

[Problems to be Solved by the Invention] In such an element that has both light emission and light reception, the method of optical and electrical separation between the two (the light emitting part and the light receiving part) is important, and the functions used thereby are important. is also determined. Therefore,
A configuration in which there is a degree of freedom in optical and electrical separation increases the degree of freedom in design, and new functions can be expected.

However, in the conventional example described above, optical separation and electrical separation are performed at the same time, and the functions are also limited. For example, the light receiving section 77 can detect only the light emitted from the light emitting section 76, and cannot detect the light inside the light emitting section 76.

In order to detect the light inside the light emitting part, there is no optical separation between the light emitting part and the light receiving part, but it is necessary to electrically separate the light emitting part and the light receiving part.
However, in the conventional example described above, there is not enough freedom in separation to adopt such a configuration.

Furthermore, in the conventional example described above, since the same active layer 75 is used for light emission and light reception, it is difficult to optimize both characteristics at the same time. Even if the characteristics of the light emitting section (such as the emission spectrum) are optimized, the light reception efficiency (sensitivity) cannot necessarily be said to be optimized at the emission wavelength.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a semiconductor optical device having a structure that has a high degree of freedom in design and can flexibly respond to requests.

[Means for Solving the Problems] In the semiconductor optical device according to the present invention for achieving the above object, the 11th Jj region and the second region preferably configured as one of the active layer and the light absorption layer are, for example, , are formed in the same waveguide so as to share the waveguide mode with each other, and further provided with a means (by flow injection, electric field application, optical excitation, etc.) for independently controlling the first and second fiR@. There is.

More specifically, one of the first region and the second region is formed as an active layer and the other is formed as a light absorption layer, or the control means is formed from an electrode and a light absorption layer for forming population inversion in the active layer. The active layer can be detected by using an optical signal detected by a light receiving section consisting of an electric control means comprising an electrode for detecting the electric field of the active layer, or a light absorption layer and an electric control means for controlling the light absorption layer. and an electrical control means for controlling the active layer, the light emitting section is configured to be controlled, and it has a means for outputting an optical signal from the outside to the same optical waveguide, and this optical signal is Light is amplified by propagating through a waveguide,
The light emitting section may be controlled by the optical signal detected by the light receiving section so that the amplification factor between input and output is always constant.

In this way, according to the present invention, two regions preferably formed as a light emitting part or a light receiving part are created in the same waveguide,
Since these are configured to be controlled separately, a semiconductor optical device that can be used as a light emitting/receiving device with a high degree of freedom can be realized.

[Example] Fig. 1 is a perspective view of a first embodiment of the present invention, and Fig. 2 shows an example of a system using the first embodiment. ) A 5I-GaAs buffer FJ12 with a thickness ILLm is placed on the GaAs substrate 11,
5I-Alo, i Gaa, y As with a thickness of 1.5 um
Cladding layer, thickness 0. 1&im non-doped A 1
o, osG ao, *sA S active layer 14, 0.3 μm thick S I-A 1 a,z G ao,s
As cladding layer 15, non-doped A with a thickness of 0.1 μm
1 o, osG a o, *sA S absorption layer 16.
1 μm thick S I A 1o, x Gao, y A
S cladding layers 17 were sequentially laminated using the molecular beam epitaxial method.

Next, etching was performed beyond the active layer 14 and up to the cladding layer 13, leaving the stripe region. After that, mask the stripe and one side of the stripe, and mask only one side of the stripe (right side in Figure 1).
The ao, t As cladding layer 18 was embedded using a liquid phase epitaxial method.

Furthermore, the mask was removed and the other side of the stripe left earlier (left side in Figure 1) was used as the 1st n-Alo, sG ao,
y As cladding layer 19. Alo, i Gao,
yAs high resistance layer 20, second n A lo, s G
The ao, y As cladding layer 21 was similarly filled using liquid phase epitaxial method. At this time, S I -A 1
o, w Ga.

. The thickness of each layer was controlled so that the high resistance layer 20 was located approximately in the middle of the As cladding layer 15.

Furthermore, a portion up to the high-resistance layer 20 was removed along the stripe by etching at a distance of several μm from the stripe.

Furthermore, a p-electrode 22 is placed on top of the p-cladding layer 18, and an n-electrode 22 is placed on top of the p-clad layer 18.
The poles 23 and 24 were formed on the first and second n-cladding layers 19 and 21 after pretreatment to establish ohmic contact.This embodiment has a light emitting part and a light receiving part in the same waveguide. The feature is that it has an electrode structure that can electrically control the light emitting part and the light receiving part.

The operation of the first embodiment will be explained.

In the light emitting part, p-electrode 22→p-cladding layer 18
→Active layer 14→First n-cladding layer 19-In-electrode 2
Since electrical connection is made through the path passing through the picture electrodes 22 and 24, if a forward bias is applied between the picture electrodes 22 and 24, a current will flow through this path, carriers will be injected into the active layer 14, a population inversion will be formed, and induction will occur. A release occurs.

On the other hand, in the light receiving section, electrical connection is made through the path of p-electrode 22 -> p- cladding layer 18 - light absorption layer 16 -> second n-cladding layer 21 -> n-electrode 23 . Therefore, if a reverse bias is applied to the picture electrodes 22 and 23, light will be detected by the light absorption layer 16.

At this time, since the active layer 14 and the light absorption layer 16 are optically coupled and form one waveguide, the optical power inside the light emitting section can be detected. That is, in this embodiment, what is detected is the optical power inside the element, and not the light emitted outside the light emitting section as in the conventional example. Therefore, when using the device of this example as a semiconductor laser, it is necessary to keep in mind that what is detected is the optical power inside the device.

In the configuration of the above embodiment, if a forward bias is applied between both the electrodes 22 and 23 and between the electrodes 22 and 24, the light emitting section and the light receiving section both become light emitting sections and can function as a normal semiconductor laser. be.

It is also possible to use only one set of electrodes 22.23 or 22.24 and have each function performed individually. If forward bias is applied only to the light emitting part, it becomes a semiconductor laser, and if reverse bias is applied only to the light receiving part, it functions as a pin-PD.

Furthermore, as in the conventional example shown in FIG.
It is also possible to provide grooves up to 4 and use one side as a light emitting section and the other side as a light receiving section. Thus, APC
It is possible to do things such as control. Furthermore, in the device of this example, the light absorption layer 16 can be designed in accordance with the light emission characteristics of the light emitting part. In other words, the layer structure (composition, doping amount) of the light absorption part 16 can be independently changed to improve the light reception efficiency. You can improve characteristics such as improvement.

Now, this embodiment has a new function of being able to drive the light emitting part and the light receiving part simultaneously and independently, and detecting the optical power inside the light emitting part.An example of a system using this is shown in Figure 2. I will explain. In FIG. 2, 25 is an AR co-coating applied to both end faces in order to use the first embodiment as an optical amplification element 30, 26 is an optical fiber, and 27 is an AGC circuit.

This system is an optical relay system, in which a signal transmitted through an optical fiber 26 is amplified while being guided inside the semiconductor optical device, and is output to the other optical fiber 26.

In this case, it is desired that the degree of amplification is always constant. In this system, the light inside the amplifier 30 is received by the light receiving section, and the light is returned to the light emitting section to perform auto gain control such as controlling the amount of current thereto. The signal light can be detected by providing the light receiving section with a demodulation circuit that matches the frequency of the signal light (this is provided in the AGC circuit 27).
This can be done separately from the C-level spontaneous emission light of the optical amplifier 30.

AG by detecting the level of spontaneous emission light when there is no signal light
It is also possible to do C.

1 Furthermore, the electrode 23 of the light receiving section is divided in the resonance direction, the signal level received on the input side and the signal level received on the output side are compared, and feedback is applied to the light emitting section so as to keep the ratio constant. AGC can also be performed.

Conventional optical amplifiers also require AGC, and generally a beam splitter, fiber type demultiplexer, or the like is used to separate a part of the output signal light. Compared to this,
This system does not require separation (the equipment is greatly simplified).

In the first embodiment shown in FIG. 1, the active layer 14 and the light absorption layer 16 have the same composition and the same film thickness. Therefore, as can be seen from the above, the structure remains the same and the electrodes 22.2
If the bias conditions between 3 and 22.24 are completely reversed,
The active layer 14 is used as a light receiving part and the light absorbing layer 16 is used as a light emitting part.

However, the light receiving section causes a loss to the light emitting section and deteriorates the characteristics of one light emitting section, so it is not necessarily necessary to make the light emitting section and the light receiving section the same. Rather, it is better to optimize one light-emitting section according to the light-emitting characteristics and one light-receiving section according to the light-receiving characteristics, and the feature of this embodiment is that each can be designed independently. Its design should be tailored to the expected functionality.

Design examples of the optical amplifying element 30 in the system shown in FIG. 2 are shown in FIGS. 3(a) to 3(d).

FIG. 3(a) shows the band structure of the conduction band of the configuration explained in the first embodiment of FIG.

In the system shown in FIG. 2, it is better not to deteriorate the amplification characteristics, so we place emphasis on the characteristics of the light emitting part, and arrange the active layer 14 in the center of the waveguide mode, as shown in FIG. 3(b). However, if the light absorption layer 16 is formed in the part that becomes the tail of the waveguide mode, the third
It is expected that the amplification factor will be improved compared to Figure (a).

In addition, as shown in FIG. 3(c), the active layer 14 and the light absorption layer 16
has a quantum well structure, and GRIN is installed on both sides of the waveguide structure.
It is also possible to provide a (graded 1ndex) structure. When using quantum wells, the composition, barrier width, etc. can be changed to arbitrarily design light emission and light reception characteristics suitable for the intended use.

Furthermore, as shown in FIG. 3(d), a layer 31 with a superlattice structure is provided between the active layer 14 and the light absorption layer 16 to realize a structurally high resistance layer and ensure semi-insulation between the two. It is also possible to consider a design in which

FIG. 4 shows a second embodiment. This embodiment is composed of four electrodes. Components that are the same as in FIG. 1 are given the same numbers. In this embodiment, in order to obtain a four-pole structure, the substrate portion is removed and electrodes are provided under it. In this way, the electrical connection is completely separated vertically between the light emitting part (lower part) and the light receiving part (upper part) with the high resistance j120 and the SI-cladding layer 15 as boundaries. The type layer 41 - the active layer 14 → the n-type layer 43 → the n-type electrode 47 are connected, and the light receiving part is connected to the p-type electrode 46 → p-type layer 42 → light absorption layer] 6-〇-type layer 44 → n-type electrode 48 Optically, the
This embodiment is the same as the first embodiment, and has the same operation and effect.

FIG. 5 shows a third embodiment. In the same figure, n-GaA
On the s substrate 51, an n-GaAs buffer layer 52 with a thickness of Igm, an n-Alo with a thickness of 1.5 gm, x Gaa, t
AS cladding layer 53, 0.1 μm thick non-doped Al a, osG ao, ssAs active layer 54, 1.5 μm thick p-A 1 o, z Gao, t As
A cladding layer 55 is laminated. Next, a stripe is produced by etching, and a high resistance N56 is produced on the bottom surface portion other than the stripe. Furthermore, non-doped Ala with a thickness of 0.1 μm, osG ao,
The eaAS light absorption layer 57 is further laminated with an n''A1゜GaO,?A s cladding layer 58 so as to embed the stripe.Furthermore, an n-type electrode 6 is formed on the top of the stripe.
0, an n-type electrode 61 is formed at the bottom of the substrate 51, and an n-type electrode 62 is formed at the top of the n-cladding layer 58 on both sides of the stripe.

The electrical connections in this embodiment are as follows.

First, the light emitting part is composed of p-type electrode 6O-p-cladding layer 55-active layer 54-n-cladding layer 53-In-buffer layer 5
2→n-substrate 51-n [connected like pole 61; Next, the light-receiving section consists of the n-type electrode 60→p-clad layer 55.
→ light absorption layer 57 → n-cladding layer 58 - nt electrode 62 In this embodiment, unlike the previous first and second embodiments, the waveguide mode is almost determined by the configuration of the light emitting part. ing. Therefore, in this example, the characteristics of the light emitting part (
The expected effect is an improvement in the emission spectrum (emission spectrum, etc.). That is, in this embodiment, the light receiving section is located in a part of the field distribution of the waveguide mode, which mainly includes the light emitting section. FIG. 6 shows a fourth embodiment. The configuration of this embodiment will be explained.

A p-GaAs buffer layer 64 with a thickness of lum and a p-GaAs buffer layer 64 with a thickness of 1.5 um are formed on a p-GaAs substrate 63.
ao,y A S cladding layer 65, thickness 0. 1um of non-doped A 10. (IsG ao, esA
S active layer 66, n −A 1 o with a thickness of 0.15 μm,
i G ao, a As cladding layer 67 is laminated. Next, the p-
Etching is performed up to the cladding layer 65. After that, S I -A 1 o, z Gao, i As except for the stripe
It is filled with a cladding layer 68. Further, an n-Alo, aGao, s As cap layer 69 with a thickness of O, lum, an n-A lo, *Gao, s As cladding layer 70 with a thickness of 0.1 um, and a non-doped Al with a thickness of 0.1 um. o
, oaG ao@sAs light absorption layer 71, thickness 1.5
pAlo of um.

In the first step of forming the sGas, tAs cladding layer 72, the n-cap layer 69 is removed except for the stripe portion, and an nt electrode 73 is formed on top of the n-cap layer 69. Furthermore, a p-electrode 74 is provided above the stripe, and a p-electrode 75 is provided below the substrate 63.
form.

The electrical connections in this embodiment are as follows.

The light emitting part is composed of piii pole 75-p substrate 63-jp-buffer layer 64→p-cladding layer 65→active layer 66-6n-
The cladding layer 67-n-cap layer 69 is connected to the n-electrode 73. On the other hand, the light-receiving part has the pif pole 74-p-cladding layer 72→light absorption layer 7l-1n-cladding layer 70→
It is connected to the n-cap layer 69→n@tM73.

Optically, although the stripe is temporarily interrupted at the n-cap layer 69, the effect of the upper and lower stripes makes it possible to
It can be treated as one waveguide (there is almost no difference from the first embodiment).

1. Therefore, this device also provides the same effects as the first embodiment.

In the first to fourth embodiments described above, the constituent material is GaAS-based, but it is not limited to GaAS-based, and other materials such as InP-based
It may also be made of other conductive materials such as V-based or II-Vl-based.

Further, although the active layer and the light absorption layer are described using quantum wells, each of them may have a multi-quantum well structure, a quantum wire, or the like.

The manufacturing method uses well-known film forming equipment with excellent controllability and reproducibility.
Any etching device may be used.

Further, the waveguide on which the active layer and the light absorption layer are formed may be configured as a single mode rectangular waveguide, a multimode waveguide, or the like depending on the application.

[Effects of the Invention] As explained above, according to the present invention, the first region and the second region, which are preferably configured as an active layer or a light absorption layer, are fabricated in the same waveguide, and the first and second regions are formed in the same waveguide. Since means are provided to independently and separately control the two regions, for example, light emission,
As an optical element that also receives light, the degree of freedom in design increases.

Thereby, the light emitting part and the light receiving part can be designed uniquely, and the characteristics can be improved. In addition to the conventional configuration, it is also possible to configure a system with new functions.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of a semiconductor device according to the present invention, FIG. 2 is a diagram showing an optical relay system configured using the first embodiment, and FIG. 3 is a diagram showing (a) to (d). 4 is a diagram showing the second embodiment, FIG. 5 is a diagram showing the third embodiment, FIG. 6 is a diagram showing the fourth embodiment, FIG. 7 is a diagram showing a conventional example. 11.51.63... Board, engineering 2.52.64.
...Buffer layer, 13.15.18.19.21
．． 53.55.58...Clad layer, 14.54
．． 66... Active layer, 16.57.71...
Light absorption layer% 20.56...High resistance layer, 22.23
．． 24.45.46, 47.48, 60. 62.73
, 74, 75...electrode, 25...AR cocoing, 26...optical fiber, 27...
AGC circuit, 30... Optical amplifier, 31...
Superlattice layer (SL layer), 41.42...p-type layer, 4
3.44...n-type layer, 69...n-cap layer

Claims (1)

[Claims] 1. A first region and a second region preferably configured as one of the active layer and the light absorption layer are formed in the same waveguide, and the first and second regions are independently formed. A semiconductor optical device characterized in that it is provided with means for controlling. 2. The semiconductor optical device according to claim 1, wherein one of the first region and the second region is an active layer, and the other is a light absorption layer. 3. The semiconductor optical device according to claim 2, wherein the control means is an electrical control means comprising an electrode for forming population inversion in the active layer and an electrode for detecting an electric field from the light absorption layer. 4. A light emitting section comprising the active layer and an electrical control means for controlling the active layer using a light signal detected by a light receiving section comprising the light absorption layer and an electric control means for controlling the light absorption layer. 4. The semiconductor optical device according to claim 3, wherein the semiconductor optical device is configured to provide control. 5. It has a means for inputting and outputting an optical signal from the outside to the waveguide, and this optical signal is optically amplified by propagating in the waveguide, and the amplification factor between input and output is always constant. 5. The semiconductor optical device according to claim 4, wherein said light emitting section is controlled by an optical signal detected by a light receiving section. 6. The semiconductor optical device according to claim 1, wherein the first and second regions are opposed to each other with a semi-insulating layer interposed therebetween. 7. The semiconductor optical device according to claim 1, wherein the first and second regions share a waveguide mode with each other. 8. The semiconductor optical device according to claim 1, wherein the other region of the first and second regions exists in a part of the optical electric field distribution of the waveguide mode mainly in one of the two regions. 9. The semiconductor optical device according to claim 7, wherein the first and second regions have a quantum well structure. 10. The first and second regions are opposed to each other via a layer having p-type or n-type polarity, and further, the outer layer of both regions is composed of a layer having a polarity opposite to that of the first and second regions. Item 1. Semiconductor optical device according to item 1.