JPH0521782A - Semiconductor light function element - Google Patents

Abstract

PURPOSE:To provide a semiconductor light function element with a means for reducing a radiation angle for solving problems such as loss of a signal light due to a wide radiation angle and deterioration in S/N due to increase in a background light. CONSTITUTION:A light function element 101 is provided on a semiconductor substrate 100 and a slit 106 is constituted by a screening object 107 within its window portion. This slit 106 has a spacing with a width of W and has a section shape with a period P and a thickness H. In this case, an irradiation direction of light is limited by theta in tantheta=W/H (theta; vertical direction is 0 degrees).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical functional element in which a semiconductor light emitting portion and a light receiving portion are monolithically integrated. INDUSTRIAL APPLICABILITY The present invention is suitable for an optical operation element which is a basic element for two-dimensional optical information processing.

[0002]

2. Description of the Related Art Conventionally, as an integrated optical functional device, there is an InGaAsP optical memory device in which a heterojunction phototransistor and a light emitting diode are integrated as shown in FIG. 19 (Technical digest 20C3-2, Integrated Optics).
and Optical-fiber Communication (IOOC) 1989, Kobe,
Japan). This optical memory device has a structure in which light is incident from the substrate 1 side and output light 3 is emitted above the substrate 1,
The thickness of the substrate 1 is thicker than the element size, and crosstalk of the input light between adjacent elements occurs when the input light 2 from the back surface of the substrate reaches each element on the front surface of the substrate, and it is difficult to support the substrate 1. , The problem of heat dissipation in large-scale integration,
There are many problems to be solved. FIG. 19 shows a cross-sectional view of the integrated optical functional device, but in order to make each layer easy to understand,
The cross section is not shaded.

[0003]

Although not publicly known, there is an optical integrated semiconductor optical functional device proposed in Japanese Patent Application No. 2-73908, as shown in FIG. This semiconductor functional device comprises an n-Al _0.4 Ga _0.6 As emitter layer 23 and p-GaAs on an n-GaAs substrate 22.
Base layer 24, n-GaAs collector layer 25, n-Al
_0.4 Ga _0.6 Asn-type cladding layer 26, p-Al _0.4 Ga
_This is a structure in which a _0.6 Asp type clad layer 27 and a p-GaAs cap layer 28 are sequentially stacked. An n-side ohmic electrode 21 is formed on the back side of the substrate, and a p-side ohmic electrode 29 is formed on the cap layer 28. The p-GaAs cap layer 28 is partially removed to form a window 46 for input / output light.

In this element, the light emitting diode 41 functions as the light emitting portion 41, and the heterojunction phototransistor 4
0 functions as the light receiving unit 40. Then, there is positive optical feedback from the light emitting section 41 to the light receiving section 40 inside the element, which causes the optical differential gain 81 (specific to the optical functional element as shown in FIG. 22 between the input light intensity and the output light intensity. (Shown by a chain line), optical bistable 82 (shown by a solid line), optical switch 83
It may have a non-linear or hysteresis characteristic (shown by a broken line). The principle that the above three characteristics of the optical functional element are realized is exactly the same as that of the photothyristor except that light is emitted from the light emitting section. As shown in FIG. And the state of the element is determined only on the load line 85 by the load resistance 42 connected in series to the optical function element. Therefore, by changing the load resistance 42 and the bias voltage 43 shown in FIG.
Two characteristics are realized.

For example, when the load resistance 42 is large, the current flowing through the element is limited to a small value. Therefore, when the input light is increased from 0, the current monotonically increases and the output light monotonically increases (light). Differential gain characteristics). When the load resistance 42 is small, when the input light is increased from 0, a point where the current-voltage characteristic crosses the load line 85 according to the intensity of the input light appears. When the input light at this time is exceeded, the optical functional element suddenly shifts to the ON state and the output light sharply increases. Once in the ON state, the element emits light with the current flowing inside, and the light causes positive feedback that causes a further current to flow to maintain the ON state. Switch characteristics). If the resistance value is in the middle of the two, it suddenly shifts to the ON state while the input light increases, but the current for maintaining the ON state is insufficient in the process of decreasing the input light, so The optical input suddenly shifts to the off state again with a smaller optical input value (optical bistable characteristic). In addition,
In FIG. 21, reference numeral 88 is a characteristic curve when the input light is infinite, reference numeral 89 is a characteristic curve when the input light is present, and reference numeral 9 is shown.
0 indicates a characteristic curve when there is no input light.

Further, according to the optical functional element, the input / output direction of light can be configured to be perpendicular to the integrated surface.
It is easy to form a two-dimensional array, and two-dimensional optical information can be handled in parallel. As a method of utilizing this parallelism, the configuration shown in FIG. 23 is often used. That is, this is a method in which the optical function elements 51 provided in an array on the semiconductor substrate 50 are opposed to each other through the optical system 52 such as a lens. In this configuration, when the output light that carries the signal passes through the optical system 52, the loss of the light 53 that spreads beyond the condensing range of the optical system 52 and the background reflected or scattered by the reflecting object 54 outside the substrate. Since the S / N is lowered due to the increase of the light 55, a small emission angle of the light emitting element is important.

As an example of the emission angle of the light emitting element (light emitting section), consider the case of a surface emitting LED which is often used as the light emitting section of an optical functional element because it is relatively easy to manufacture. The surface-emitting type LED has weak directivity of light in the direction perpendicular to the output surface, and the emission emission angle half-width at half maximum is 60 under perfect diffusion conditions.
It ’s big. It is not easy to reduce the half width due to the structure of the surface emitting LED.

A method of reducing the radiation angle by providing a condenser lens on the light emitting element can be considered, but when the element size becomes small, it is not possible to make a small condenser lens above the output window of the element. It gets harder. The purpose of the present invention is to
It is an object of the present invention to provide a semiconductor optical functional device equipped with means for reducing the emission angle in order to solve the problem of S / N reduction due to an increase in background light due to a wide emission angle.

[0009]

According to another aspect of the present invention, there is provided a semiconductor optical functional device including a light receiving portion on a semiconductor substrate, a light emitting portion on the light receiving portion, and a window provided on the light emitting portion side. A semiconductor optical functional device having a structure in which input light and output light are input and output from the optical part. The forbidden band width of the semiconductor material that constitutes the light emitting part of the optical functional device is larger than the main peak energy of the input light, and the light receiving part of the optical functional device The forbidden band width of the semiconductor material that constitutes is equal to or smaller than the main peak energy of the input light,
A part of the output light generated from the light emitting portion is returned to the light receiving portion, is absorbed by the light receiving portion, and has a light feedback effect, and by this effect, a non-linear response is formed between the input light and the output light. ..

According to the present invention, in order to realize the above-mentioned problem of narrowing the emission radiation angle, the window portion of the light emitting portion of the optical functional element has a thickness for transmitting a part of light and a part of it. A method of narrowing the emission angle of output light by providing a plurality of slits is used. FIG. 1 shows an example of a cross section of an optical functional element provided with slits. In FIG. 1, the optical functional element 101
Is provided on the semiconductor substrate 100, and the slit 106 is formed in the window portion by the shield 107. The slit 106 has a gap of width W as shown in the figure,
It has a cross-sectional shape with a period P and a thickness H. In this case, as shown in an enlarged view of the slit 106 in FIG. 2, the output direction of light is limited by θ that satisfies tan θ = W / H (θ is 0 degrees in the vertical direction).

The period P determines the light extraction efficiency η, which is a ratio of the output light extracted to the outside. The light extraction efficiency is determined by the slit 106 with respect to the light emitting area.
Since it is the ratio of the area of the transmission part of, η = W / P. The ratio R of the light finally emitted to the outside of the light emitting portion is dependent on the cos θ of the light intensity and the emission angle under the condition of perfect diffusion in which the light emission from the light emitting portion spreads isotropically. Therefore, the following equation is obtained.

[0012]

[Equation 1]

To actually determine the size of the slit,
After giving a desired radiation angle, R is determined to be large. That is, the ratio of W and H is determined from the desired radiation angle. In order to increase R, P may be decreased.

There are several methods for forming the light shield 107 of the slit 106. (1) The absorber 110 (see FIG. 3) (2) A combination of a plurality of reflecting layers 111 and absorbing layers 110 (See FIG. 4) (3) A combination of a plurality of absorption layers 110 and transmission layers 112 (see FIG. 5) is a candidate.

As can be seen from the above conditions, the maximum value of the radiation angle is not the absolute value of the size of the slit 106, but W and P.
And H, the size of the slit 106 can be reduced to near the emission wavelength. Shade 10
If the material of No. 7 is selected appropriately, it can be incorporated in the process of integrating the optical functional device. Further, if the light emission direction of the element is perpendicular to the surface, it can be applied to both surface emitting diodes and surface emitting semiconductor lasers regardless of whether the light emission is coherent light or incoherent light.

Although FIG. 1 shows only the one-dimensional direction in which the slits 106 are formed, the slits 106 are two-dimensionally formed.
And the width, period, and thickness of the slit 106 may be changed depending on the direction. In that case, the full width at half maximum of light emission is asymmetric in the vertical and horizontal directions. The shape of the slit 106 may be square, rectangular, circular, or elliptical. 6 and 7 are partial plan views of the two-dimensional slit 106 formed by the light transmitting portion 114 and the light shielding portion 116 (shown by diagonal lines). FIG. 6 is composed of grid-shaped slits 106 that are asymmetrical in the vertical and horizontal directions.
Has an elliptical slit 106 formed on a plane.

[0017]

According to the invention described in claim 1, the slit provided in the window portion located on the light emitting portion of the semiconductor optical function element transmits the light transmitted from the gap having the width W in the half direction of the emission radiation angle in the periodic direction of the slit. The width θ is narrowed to tan θ = W / H. Therefore, the emission emission angle in the vertical direction of the semiconductor optical function element can be narrowed.

[0018]

EXAMPLES Examples of the present invention will be described below. FIG. 8 is a sectional view of the first embodiment of the semiconductor optical functional device according to the present invention. The semiconductor optical functional device according to the present embodiment has an n-Al _0.4 Ga _0.6 As emitter layer 12 on an n-GaAs substrate 122.
3, p-GaAs base layer 124, n-GaAs collector layer 125, n-Al _0.4 Ga _0.6 Asn-type cladding layer 1
26, undoped Al _0.2 Ga _0.8 As active layer 131, p-A
l _0.4 Ga _0.6 Asp type cladding layer 127, p-GaAs
The cap layer 128 is laminated in order.

N-Al _0.4 Ga _0.6 As emitter layer 12
3, the p-GaAs base layer 124 and the n-GaAs collector layer 125 constitute a light receiving portion 141, and the light receiving portion 141 is formed.
In order to improve the efficiency of electron injection from the emitter to the base, is composed of a heterojunction photophoresistor using an emitter with a large forbidden band. n-Al _0.4 Ga
_0.6 Asn-type cladding layer 126, undoped Al _0.2 G
The a _0.8 As active layer 131 and the p-Al _0.4 Ga _0.6 Asp clad layer 127 constitute the light emitting portion 140, and the light emitting portion 140 has a double heterojunction structure in order to improve the light emitting efficiency.

The p-GaAs cap layer 128 is etched to form a window portion 142 reaching the p-Al _0.4 Ga _0.6 Asp type cladding layer 127 on the upper part of the device so that incident light and outgoing light can enter and exit. It is configured.
Here, when the window 142 is formed, p-GaA
By etching the s cap layer 128 in a comb shape, the slits 106 as described above are formed.
An n-type ohmic common electrode 121 is formed on the back surface of the n-GaAs substrate 122, and a predetermined voltage is applied between the n-type ohmic common electrode 121 and the p-type ohmic upper electrode 129. Further, between the semiconductor optical functional element, the light receiving portion 141 is crossed, and n-Ga
Separation grooves 143 reaching the As substrate 122 are formed on the left and right.

Positive feedback of light, which is a feature of the optical function element, occurs when light passes from the light emitting section 140 to the light receiving section 141 inside the element. The input light passes through the slit 106, and the light emitting unit 14
0 is further transmitted, enters the light receiving unit 141, and is absorbed. The output light passes through the slit 106 from the light emitting unit 140 and is output upward. The carriers injected from the upper and lower electrodes 121 and 129 are undoped Al _0.2 Ga of the light emitting section 140.
_{The 0.8} As active layer 131 is radiatively recombined to generate output light. The light from the light emitting section 140 has energy of GaAs.
Since it is larger than the forbidden band width, the absorption is absorbed by the p-GaAs cap layer 128 forming the upper slit 106. The light output from the gap of the slit 106 is p-G
When the thickness of the aAs cap layer 128 is H and the width of the gap is W, tan θ = W / H is emitted only in a direction at an angle of θ (θ is 0 degrees in the vertical direction) or less, and a desired output light is emitted. A narrower emission angle of light is realized.

Next, the manufacturing process of the first embodiment will be described with reference to FIGS. First, as shown in FIG.
On the GaAs substrate 122, n-Al _0.4 Ga _0.6 As emitter layer 123, p-GaAs base layer 124, n-Ga.
As collector layer 125, n-Al _0.4 Ga _0.6 Asn type cladding layer 126, undoped Al _0.2 Ga _0.8 As active layer 13
1, p-Al _0.4 Ga _0.6 Asp type clad layer 127, p
-The GaAs cap layer 128 is grown in order. The metal organic vapor phase epitaxy method was used as the growth method. The thickness of each layer is n
-Al _0.4 Ga _0.6 As emitter layer 123 is 0.2 μm,
The p-GaAs base layer 124 has a thickness of 0.1 μm and n-GaA.
s collector layer 125 is 0.5 μm, n-Al _0.4 Ga _0.6
Asn-type clad layer 126 is 0.5 μm, undoped Al
_0.2 Ga _0.8 As active layer 131 is 0.1 μm, p-Al
_0.4 Ga _0.6 Asp type clad layer 127, 0.5 μm,
The p-GaAs cap layer 128 has a thickness of 5 μm.

Next, as shown in FIG. 10, by using a photolithography technique and an etching technique,
The slit 106 is formed in the p-GaAs cap layer 128. At this time, the etching is p-Al _0.4 Ga _0.6 Asp.
The p-Al _0.4 Ga _0.6 Asp type clad layer 127 should be stopped just above the type clad layer 127.
Etching does not change the electrical characteristics of the device. When the reactive vapor phase etching method is used as the etching method,
The wall surface of the slit is vertical and can be formed smoothly.

Next, as shown in FIG. 11, etching is performed with a solution of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1 for element isolation to form an isolation groove 143. Finally, as shown in FIG. 12, the p-type ohmic electrode 129 (A
uZn / Au) on the back surface of the n-GaAs 122 substrate.
The ohmic electrode 121 (AuGe / Ni / Au) is formed. In this embodiment, the slit 106 has a gap of 3 μm.
m, the period of the slit 106 is 6 μm, and the radiation angle θ = 3
With the result of 0 degree and R = 25%, the full width half maximum half width 6
The radiation angle could be narrowed to half of 0 degree.

Further, a second embodiment of the present invention will be described. FIG. 13 is a sectional view of a second embodiment of the semiconductor optical functional device according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. The semiconductor optical functional device of this embodiment has an n-
On the GaAs substrate 122, n-Al _0.4 Ga _0.6 As emitter layer 123, p-GaAs base layer 124, n-Ga.
As collector layer 125, n-Al _0.6 Ga _0.4 As block layer 130, n-Al _0.4 Ga _0.6 Asn-type cladding layer 1
26, undoped Al _0.2 Ga _0.8 As active layer 131, p-A
l _0.4 Ga _0.6 Asp type cladding layer 127, p-Al _0.2
The Ga _0.8 Asp clad layer 132 and the p-GaAs cap layer 128 are laminated in this order.

The difference of the second embodiment from the first embodiment is that the cladding layer structure of the light emitting section 140 is used as it is as the slit 106. Active layer 13
The light emission from 1 has a p-bandwidth equal to that of the active layer 131.
It is absorbed by the Al _0.2 Ga _0.8 Asp type cladding layer 132. However, the p-Al _0.2 Ga _0.8 Asp type cladding layer 13
Since the forbidden band width of No. 2 is larger than the forbidden band width of the p-GaAs base layer 124, the forbidden band width of the p-GaAs base layer 124 is calculated from the p-Al _0.2 Ga _0.8 Asp type cladding layer 13.
The light corresponding to the energy in the range of the forbidden band of 2 is not absorbed by the portion forming the slit 106, reaches the light receiving portion 141, and the light input to the element from outside the optical functional element is Even if the slit 106 exists, it can enter the light receiving unit 141 without being obstructed.

Next, the manufacturing process of the second embodiment will be described with reference to FIGS.
It will be described with reference to FIG. First, as shown in FIG.
On -GaAs substrate _{122, n-Al 0.4 Ga 0.6} As emitter layer 123, p-GaAs base layer 124, n-G
aAs collector layer 125, n-Al _0.4 Ga _0.6 Asn-type cladding layer 126, undoped Al _0.2 Ga _0.8 As active layer 1
31, p-Al _0.4 Ga _0.6 Asp type cladding layer 127,
p-Al _0.2 Ga _0.8 Asp-type cladding layer 132, p-G
The aAs cap layer 128 is sequentially grown. The metal organic vapor phase epitaxy method was used as the growth method. The thickness of each layer is
The n-Al _0.4 Ga _0.6 As emitter layer 123 is 0.2 in this order.
μm, p-GaAs base layer 124 is 0.1 μm, n−
GaAs collector layer 125 is 0.5 μm, n-Al _0.4 G
a _0.6 Asn-type clad layer 126 is 0.5 μm, undoped A
l _0.2 Ga _0.8 As active layer 131 is 0.1 μm, p-Al
_0.4 Ga _0.6 Asp type clad layer 127 is 0.5 μm, p
-Al _0.2 Ga _0.8 Asp type clad layer 132 has a thickness of 5 μm,
The p-GaAs cap layer 128 has a thickness of 0.5 μm.

Next, as shown in FIG. 15, by using a photolithography technique and an etching technique,
The cap layer 128 is selectively removed only at the light input window portion 142. NH ₂ OH: H ₂ O ₂ as etching solution
= 1: 20 was used. Further, as shown in FIG.
The slit 106 is formed in the -Al _0.2 Ga _0.8 Asp type cladding layer 132. At this time, etching is p-Al _0.4
It is necessary to stop almost directly above the Ga _0.6 Asp type clad layer 127, but even if the p-Al _0.4 Ga _0.6 Asp type clad layer 127 is slightly etched, the electrical characteristics of the device do not change. When the reactive gas phase etching method is used as the etching method, the wall surface of the slit 106 can be formed to be vertical and smooth.

Then, as shown in FIG. 17, etching is performed with a solution of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1 for element isolation to form isolation trenches 143. Finally, as shown in FIG. 18, the window 142 of the p-GaAs cap layer 128 is formed.
P-type ohmic electrode 129 (AuZn / A
u), an n-type ohmic electrode 121 (AuGe / Ni / Au) is formed on the back surface of the n-GaAs substrate 122.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the first and second embodiments, the semiconductor layer was formed by using the metal organic chemical vapor deposition method, but it is grown by other means capable of forming a thin film such as liquid phase growth method and molecular beam growth method. Even in such a case, the structure of the present invention can be applied.

[0031]

According to the first aspect of the present invention, the emission emission angle in the vertical direction is narrowed without impairing the characteristics of the semiconductor optical functional device that inputs and outputs light in the vertical direction to the integrated surface. Therefore, it is possible to solve the problem of a decrease in S / N due to an increase in background light due to a wide radiation angle. Further, even if the slit film thickness is comparatively thin, the slit can be formed with sufficient accuracy, so that it is easier to manufacture by providing a minute optical system such as a condenser lens on the upper part, and it is suitable for integration. The narrowing of the radiation angle has an advantage that it does not depend on whether the light source is coherent or incoherent.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of a semiconductor optical functional device of the present invention.

FIG. 2 is an enlarged sectional view of a slit portion of the semiconductor optical functional device of the present invention.

FIG. 3 is a sectional view showing an example of a slit of the present invention.

FIG. 4 is a sectional view showing an example of a slit of the present invention.

FIG. 5 is a sectional view showing an example of a slit of the present invention.

FIG. 6 is a plan view showing an example of a slit of the present invention.

FIG. 7 is a plan view showing an example of a slit of the present invention.

FIG. 8 is a sectional view of the first embodiment of the present invention.

FIG. 9 is a diagram showing a manufacturing method according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a manufacturing method according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a manufacturing method according to the first embodiment of the present invention.

FIG. 12 is a diagram showing a manufacturing method according to the first embodiment of the present invention.

FIG. 13 is a sectional view of a second embodiment of the present invention.

FIG. 14 is a diagram showing a manufacturing method according to the second embodiment of the present invention.

FIG. 15 is a diagram showing a manufacturing method according to the second embodiment of the present invention.

FIG. 16 is a diagram showing a manufacturing method according to the second embodiment of the present invention.

FIG. 17 is a diagram showing a manufacturing method according to the second embodiment of the present invention.

FIG. 18 is a diagram showing a manufacturing method according to the second embodiment of the present invention.

FIG. 19 is a diagram showing a cross-sectional view of a conventional optical functional element.

FIG. 20 is a view showing a cross-sectional view of an already proposed optical functional device.

FIG. 21 is a diagram showing voltage-current characteristics of an optical functional element.

FIG. 22 is a diagram showing the relationship between the input light intensity and the output light intensity of the optical function element.

FIG. 23 is a configuration diagram of a conventional element that handles two-dimensional optical information in parallel.

[Explanation of symbols]

100 semiconductor substrate 101 optical functional element 106 slit 107 shield 121 n-type ohmic electrode 122 n-GaAs 123 n-Al _0.4 Ga _0.6 As emitter layer 124 p-GaAs base layer 125 n-GaAs collector layer 126 n-Al _0.4 Ga _0.6 As clad layer 127 p-Al _0.4 Ga _0.6 As clad layer 128 p-GaAs cap layer 129 p-type ohmic upper electrode 131 Al _0.2 Ga _0.8 As active layer 132 p-Al _0.2 Ga _0.8 As clad layer 140 light emitting part 141 light receiving part 142 Window 143 Separation groove

Claims (1)

Claim: What is claimed is: 1. A semiconductor substrate having a light-receiving portion, and a light-emitting portion on the light-receiving portion. Input light and output light are input and output through a window provided on the light-emitting portion side. The forbidden band width of the semiconductor material forming the light emitting portion is larger than the main peak energy of the input light, and the forbidden band width of the semiconductor material forming the light receiving portion is equal to or smaller than the main peak energy of the input light. A part of the output light generated from the light emitting portion is returned to the light receiving portion, and a semiconductor optical functional element having a non-linear response between the input light and the output light due to the optical feedback effect absorbed by the light receiving portion. The slit is formed by providing a plurality of slits having a thickness H and a period P for partially transmitting light through a gap having a width W and partially shielding light in the window portion located on the light emitting portion. Emitting light in the periodic direction of A light-emitting radiation angle half-value width θ tanθ = W
A semiconductor optical functional device characterized by narrowing the angle to / H.