JPH03274030A - Optical functional element - Google Patents

Abstract

PURPOSE:To provide the optical functional element which can make input light and output light into the same direction by setting the forbidden band width of a semiconductor material constituting a light emitting part larger than the main peak energy of input light and simultaneously using the light emitting part thereof as an input window. CONSTITUTION:A phototransistor structure of an npn heterojunction is used as a light receiving part and an light emitting diode structure of a p-n homojunction is used as the light emitting part. The input light A is made incident from the window 50 in the upper part of the light emitting part II and arrives at the light receiving part I. The wavelength corresponding to the forbidden band width of the light emitting part II is about 670 nm and, therefore, if the light of this wavelength is used as the input light, this light arrives at the light receiving part I without receiving absorption in the light emitting part II. The output light B is outputted upward through the window 50 from the light emitting part II. A part of this output light arrives at the light receiving part I and the nonlinear input/output characteristics are obtd. by the optical feedback effect thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor optical functional device useful as an optical arithmetic device or the like in an optical information processing device.

[Prior art]

As an integrated optical functional device, I(
There is an InGaA sP optical memory device that integrates a PT (heterogeneous junction phototransistor) and an LED (light emitting diode) (Technical Digest, 20
C3-2, Integrated Optics a
ndOptical-fiber Con+munic
ation (100C) 1939゜Kobe, J
apan).

This element has an input light wavelength of 1.3 μm and an output light wavelength of 1.3 μm.
It is a lower input, upper output type device in which light enters from the substrate side and output light is emitted above the substrate, and is an optical memory device that utilizes optical switch operation.

Furthermore, an example in which a similar structure is applied to an AaGaAs system has also been reported (IEICE Technical Research Report, Electronic Devices, ED88-111).

In the aforementioned optical functional device (optical memory device), the input light and output light have the same wavelength, so in order to separate the input light and output light, the input light enters from the back side of the substrate, and the output light enters from the back side of the substrate. It was necessary to emit light to the front side of the Therefore, the thickness of the board is thick compared to the element size, and crosstalk of input light between adjacent elements occurs when input light from the back of the board reaches each element on the front of the board, and it is difficult to support the board. There are many problems that need to be solved, such as heat dissipation in large-scale integration. Another problem is that since the operating conditions are based on optical switch operation, the -carbon bias must be set to 0 in order to turn off the output of the element, that is, to erase written information. To improve this problem, it is important to control the amount of optical feedback.

The above-mentioned device using the AQGaAs system has a Junin Sumo wrestler output, but an AQGaAs substrate must be used to extract the output light, and this AQGaAs substrate has low thermal conductivity, so it has poor heat dissipation and is difficult to integrate on a large scale. Heat dissipation in the process becomes a problem. Furthermore, as with InGaAsP-based devices, there is also the problem of difficulty in supporting the device. G
Even when using an aAs substrate, it is necessary to etch the back surface of the substrate, and process controllability also becomes an issue.

〔the purpose〕

The purpose of the present invention is to solve the above-mentioned problems of conventional optical memory devices, reduce crosstalk between adjacent devices of input light, and provide a main input/output device with easy board support and excellent heat dissipation. The object of the present invention is to provide an optical functional device.

Another object of the present invention is that it is possible to control the amount of optical feedback without affecting the intensity of input light, and it is possible to control not only a simple optical switch operation but also an optical memory that can be written and erased by light. The aim is to realize the device as well.

Furthermore, another object of the present invention is to provide an optical functional element that can direct input light and output light in the same direction.

[structure]

The present invention provides a semiconductor optical functional element of a type in which a light receiving section is provided on a semiconductor substrate, a light emitting section is further provided above the light receiving section, and input light and output light enter and exit through a window section provided on the light emitting section side. The forbidden band width of the semiconductor material constituting the light-receiving section is greater than the main peak energy of the input light, and the forbidden band width of the semiconductor material constituting the light-receiving section is equal to or smaller than the main peak energy of the input light. The present invention relates to a semiconductor optical functional device characterized by having a nonlinear response between input light and output light due to an optical feedback effect in which a part of the output light generated from the light returns to the light receiving section and is absorbed by the light receiving section.

The structural features of the semiconductor optical functional device of the present invention are as follows.

The forbidden band of the semiconductor material that makes up the light emitting part is larger than the main peak energy of the input light, and by simultaneously using the light emitting part as an input window, it is possible to direct the input light and output light in the same direction. .

Therefore, the input light can reach the light receiving section without being absorbed by the light emitting section. By adopting such a structure, it is possible to output a sumo wrestler at the same time. Furthermore, since the forbidden band width of one light emitting section is increased, the wavelength difference between the emission wavelength and the input light can be made large, the input and output light can be easily separated, and the output light can also be made into visible light. Here, the number of input lights is not limited to one, but may be plural. Naturally, the emitted light has a shorter wavelength than the input light, and visible light output can also be obtained for infrared input light. Furthermore, due to the feedback effect of light between the light emitting section and the light receiving section, a nonlinear response can be obtained between input and output light.

FIG. 2 shows the elements of a basic embodiment. The device of this example has n-AL, 4Ga6.
@As layer 21. p-GaAsJl! 122, n-G
aAs layer 23, n-AQ, 1Ga0. , As layer 24.
p-AQl+, 4aa, 1As layer 25. p-GaAs
It has a #II structure in which layers 26 are laminated. 50 is a window for inputting light, 28 is an n-type ohmic electrode,
27 is a p-type ohmic electrode. ■ is the light receiving part (21,
22, 23 layers).

2 is a light emitting section (layers 24 and 25), and in this embodiment, an npn heterojunction phototransistor structure is used as a light receiving section, and a pn homojunction light emitting diode structure is used as a light emitting section. Input light A enters through the window 50 at the top of the light emitting section (2) and reaches the light receiving section I. At this time, the wavelength corresponding to the forbidden cloth in the light emitting part (■) in Fig. 2 is approximately 670r++w, so if light with a wavelength greater than this wavelength (for example, light with a wavelength of 780 nm) is used as input light, this light will be absorbed by the light emitting part (2). It reaches the light receiving part I without being received. Since the wavelength corresponding to the forbidden cloth of GaAs that constitutes the light-receiving part I is approximately 890 nn+, absorption in the light-emitting part ■ is small, and the center wavelength range of the input light absorbed by the light-receiving part can be set to approximately 680 to 890 nm. becomes. Output light B is outputted upward from the light emitting section (2) through the window 50. In the structure shown in Figure 2, the wavelength is approximately 670 nm.
A part of this output light reaches the light receiving section I, and its optical feedback effect brings about nonlinear input/output characteristics.

FIG. 3 shows a manufacturing process diagram of the element of the basic embodiment shown in FIG. 2. The manufacturing process will be explained below with reference to the drawings.

First, n-AQ was deposited on an n-GaAs substrate 20. ,4Ga,
, GAs layer (emitter layer) 21. p-GaAs layer (base layer) 22. n-GaAs layer (collector layer) 23, n-
A Qy, 4 Gao-g As layer 24,
A p-AQo, *Gao, GA8 layer 25 and a p-GaAs layer (cap layer) 26 are grown.

As the growth method, various methods can be used, such as LPE method (liquid phase epitaxy), MBE method (molecular beam epitaxy), and MOVPE method (metal organic vapor phase epitaxy). The thickness of each growth layer is n-Aff. 1Ga110. Ass layer 1 has a thickness of approximately 0.5 to 3.0 μm, and p-GaAs layer 22 has a thickness of approximately 0.0 μm.
5 to 0.5 μm, and the n-GaAs layer 23 has a thickness of approximately 0.5 to 5 μm.
0pm, n-AQolGao, Ass layer 4 is approximately 1.0
~3.0 μm, p-AQ, , Ga00. AsJ125 has a thickness of approximately 0.1 to 3.0 μm, and p-GaAs layer 26 has a thickness of approximately 0.1 μm.
~2.0 μm is good. Of course, the thickness may be outside the above range as long as it meets the intent of the present invention.
Figure 3(a)].

Also, A Qx Gal-x used for growth
Although the AQ mixed crystal ratio X of the As semiconductor can be arbitrarily selected within the range of 0.1<X<1.0, it is preferable that the AQ mixed crystal ratio of the emitter layer is 0.2 or more in order to increase the gain. Similarly, the AQ mixed crystal ratio of the 24th and 25th layers forming the light emitting part is also
0.5 due to the need to utilize the direct transition of GaAs semiconductors.
The following are desirable.

Next, by using photolithography and etching techniques, windows 5 are formed in the p-GaAs cap layer 26.
form 0. At this time, etching is p-AQolGa
o, it is desirable to stop at the top of the GAs layer s layer. As an etchant, for example, H2O2: NH40H
=20: If etching is performed at 40℃ using 1, 1
Approximately 2 μm of the Ga As layer is etched in 0 to 20 seconds. This etchant is AQo,,Ga,,
, since the As layer is not etched, the bottom surface of the window 50 is p-A.
jll, 4Ga, GAs layer will be located on top of the s layer [Fig. 3(b)].

Here, when the thickness of the cap layer 26 is thin (0.1 μm
Even if this etching is not performed on the front and rear surfaces, there is no problem in the operation of the device because the absorption of input light is small.

Finally, a p-type ohmic electrode 27 (for example, AuZn/Au, Cr/A
n-type ohmic electrode 28 (for example, AuGe/Ni/Au, etc.) is formed on the n-GaAs substrate 20 [
Figure 3(c)).

Another embodiment of the invention is shown in FIG. In this embodiment, the n-GaAs layer 23 and n-A1201Gao,
An absorption layer 29 for light emitted from the light emitting part is formed between the 5AsAs layers. By adding this absorption layer, it becomes possible to control the efficiency of light feedback from the light emitting section to the light receiving section, and it becomes possible to control the input/output characteristics.

The absorption layer must be transparent to input light and absorbent to output light; for example, in the element of the basic embodiment shown in FIG. If the AQ mixed crystal ratio of the Qy Gal-v A s layer is Y, the composition of the absorption layer is A Qz G 8l-1
When As, the range of Z is found to be Y<Z<0.4. That is, the forbidden width of the absorption layer must be larger than the main peak energy of the input light and smaller than the main peak energy of the output light.

FIG. 5 shows an embodiment in which a structure different from that shown in FIG. 4 is used to control the optical feedback rate. In this example, n-GaAs
Layer 23 and n-An, 1. A distributed Bragg reflective layer consisting of two types of semiconductor stacks having different refractive indexes is provided between the Ga, Ass layer 4 and the Ass layer 4.
tor, DBR) 29'. As the semiconductor material constituting this reflective layer 29', for example, in the element of the basic embodiment shown in FIG. 2, AQ-2G, Ga, -E, As, AQ-2G at-1xA s, etc. can be used. (However, 0<Xi<X2≦1.0). What is important here is that the forbidden width of the material constituting the reflective layer must be larger than the main peak energy of the input light.

6 and 7 are other embodiments of the basic embodiment. In the embodiment of FIG. 6, p-AQo, *Gao
, GAs layer 25 and p-GaAs layer 26 have a large p-AQo, Ga, 4As layer (cladding layer) 3.
0 is added to make the light emitting part a single heterojunction structure, and in the embodiment shown in FIG. 7, n-AQo, *G
ao0, large in of the forbidden cloth instead of Ass layer 4 n −
A Q@, @Ga6,4 A s layer (cladding layer) 31 is grown to form a double heterojunction structure. All of these structures are intended to improve the confinement of carriers in the light emitting part and improve the light emission efficiency. At this time, in order to fully utilize the effect of the heterobarrier, it is desirable that the difference in the forbidden width be 0.2 eV or more.

This corresponds to a difference in AQ mixed crystal ratio of about 0.2 or more.

Note that the thickness of the P and n-type cladding layers is preferably about 0.5 μm or more and 5.0 μm or less.

FIG. 8 shows p-G in the element of the basic embodiment of FIG.
In this example, an insulating layer 32 (for example, silicon dioxide, silicon nitride, etc.) is added on the aAs cap layer, and the p-type ohmic electrode is in contact with the p-GaAs cap layer only in the peripheral area of the light receiving window 200. By efficiently concentrating the injected current at the bottom of the input window, the operating current was reduced by more than 30%.

FIG. 9 shows an effect similar to that in FIG. 8 in the current confinement region 3.
This was achieved by forming 3. This current confinement region 33 can be created, for example, by forming an n region by diffusing n-type impurity atoms (such as Si) or by forming a high resistance region by implanting protons. In addition, in FIG. 9, the tip of this narrowing region 33 is p −A Qo , 4 G
ao, s A S It is stopped in N25, but n
- There is no problem even if it reaches the GaAs layer 23.

What is important is that this narrowed region 33 is formed below the electrode 27 except around the window 50.

FIG. 10 shows the element of the basic embodiment shown in FIG.
This is an example grown on a QaAs substrate 40.

Therefore, the phototransistor is of the pnp type. The structure of this example is as follows: p-GaAs base Fi40
-A Q,,4G a,,,A s layer (emitter layer)
41°n-GaAs layer 23 (base N) 42, p-Ga
As layer (collector layer) 43. p-AQ,1,Gao,G
As layer 44, n-A Qo, 4 Gao, 6
A 5N45, n-GaAs layer (cap layer) 46 is grown thereon. 47 is an n-type ohmic electrode, and 48 is a p-type ohmic electrode.

Note that the structure for controlling the amount of optical feedback shown in the embodiments of FIGS. 4 and 5 can of course be applied to the embodiments shown in FIGS. 6 and below.

Further, the embodiments shown in FIGS. 4 to 9 can also be fabricated on a P-type substrate like the device shown in FIG. 1O. At this time, to form the constriction region in FIG. 9, n-type impurity atoms (
The same objective can be achieved if the formation of a p region by diffusion of Zn, etc.) is used instead of the diffusion of n-type impurity atoms used in the device of FIG. Of course, formation of the high resistance region by proton implantation can also be used.

Although only a single element has been described so far, it is also possible to arrange the elements of the present invention in a two-dimensional array and process two-dimensional data all at once. Furthermore, the device of the present invention can of course be applied not only to GaAs-based semiconductor materials but also to other devices such as InGaAsP-based materials. It is possible to introduce a spacer layer or provide a highly doped stopper layer in the collector layer to suppress the expansion of the depletion layer.

Further, the structures of the light receiving section and the light emitting section are not particularly limited as long as they meet the intent of the present invention. For example, the light receiving section may be a photodiode or the like instead of a Peter junction phototransistor. For one light emitting part, multiple structures such as a buried structure can be used. What is important is that a light emitting part made of a material with a forbidden band higher than the main peak energy of the input light is formed above the light receiving part, and light feedback occurs between the two by coupling light.
For example, the composition of each layer forming the light emitting section is not limited to the composition used in the above embodiment.

FIG. 11 shows an example of the obtained input/output optical characteristics. (a
) is optical bistable operation, and (b) is optical switch operation. By using optical bistable operation, it is possible to realize an optical memory operation that uses an optical trigger for writing and erasing, and by using an optical switch operation, it is possible to realize an optical switch operation. In the latter case, writing can be performed by inputting a light trigger, and erasing can be performed by setting the bias voltage of the element to O. FIGS. 12(a) and 12(b) are diagrams illustrating the operation. (
a-1), (b-1) are the input/output characteristics of the element, (a
-2) and (b-2) represent the operating characteristics of the element.

Pout in (a-1) and (b-1) is output light from the functional element, Pin is input light to the functional element from the outside, and t indicates time.

In optical memory operation, by changing the input light to 1-2-1-3-1, the output light changes to A-B-A, but when the input light is changed to 2 (writing pulse), the output light changes to B. niONL
,,When the input light is set to 3 (erasing pulse), the output light is OFF.
F. In the optical switch operation, when the input light changes from 0-1-0, the output light changes from A-B. At this time, when the input light is 1, the output light is ONL, and this state is maintained until the bias of the element is set to O. In the device of the present invention, these two operations are based on the input/output optical characteristics shown in FIG.
Confirmed.

〔effect〕

The present invention not only makes it possible for input light and output light to enter and exit from the same window, but since there is no input window on the board side, the board can be closely attached to the heat sink, which greatly improves the problem of heat dissipation. In addition, crosstalk between adjacent elements caused by the conventional method of introducing input light from the substrate side is also reduced, and the difficulty of supporting the elements is also resolved, which greatly overcomes the drawbacks of conventional elements. . In addition, due to the feature of the element of the present invention that the wavelength difference between input and output light can be made up to approximately 20Or++++, even in the configuration of the Junin Sumo wrestler output, the light to the light receiving part of the output light is not affected by the input light. It is possible to control the amount of feedback, and at the same time, it is also possible to realize new functions such as wavelength conversion from infrared to visible.

It also became possible to perform logical operations using multiple input lights.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional optical memory device with lower input and upper output. FIG. 2 is a sectional view of a device showing a basic embodiment of the device of the present invention. 3(a) to 3(c) are manufacturing process diagrams of the element of the basic embodiment shown in FIG. 2. Fourth
Figures - Figure 1O. FIG. 3 is a cross-sectional view showing another embodiment of the element of the present invention. FIGS. 11(a) and 11(b) show the measurement results of optical bistable operation and optical switch operation among the input/output characteristics obtained with the device of the present invention. FIGS. 12(a) and 12(b) are operation explanatory diagrams of an optical memory operation and an optical switch operation. ■... Light receiving part ■... Light emitting part A...
・Input light B...Output light 22-p-G
aAs layer (pace layer) 23-n-GaAs layer (collector layer) 24-n-AQ, , Ga, , As layer
25'-p-AQo, 4Gao, sAS layer 26...
p-GaAs layer (cap layer) 27...ρ-type ohmic electrode 28...n-type ohmic electrode 29...absorption layer 33...narrowing region 42-n-GaAs layer (base layer) 43-p- GaAs layer (collector layer) 44-p-AQ, , Ga0. , As layer 45-n-A
Q, , 4Ga, 0, As layer 46...GaAs layer (cap layer) 47...n-type ohmic electrode

Claims (1)

[Claims] 1. In a type of semiconductor optical functional element that has a light receiving section on a semiconductor substrate and a light emitting section above it, input light and output light enter and exit through a window provided on the light emitting section side,
The forbidden band width of the semiconductor material constituting the light emitting part is larger than the main peak energy of the input light, and the forbidden band width of the semiconductor material forming the light receiving part is equal to or smaller than the main peak energy of the input light. A semiconductor optical functional device characterized in that a part of the output light generated from the light emitting part returns to the light receiving part and is absorbed by the light receiving part, resulting in a nonlinear response between input light and output light due to an optical feedback effect.