JPH0521837A - Semiconductor functional element - Google Patents

Abstract

PURPOSE:To solve a problem of forming a step upon electrical and optical separations between elements to become a problem in a process of an optical functional element. CONSTITUTION:A structure in which a photoreceptor 70 is provided on a semiconductor substrate 58, a light emitting unit 62 is further disposed thereon, and an input light, an output light are input and output through a window 73 provided at the unit 62 side, is provided. Element isolation grooves 64 are formed in the same depth as the thickness of the unit 62 of a semiconductor optical functional element between individual elements 60 on the substrate 58, and a light shielding region 68 for shielding a light emitted in parallel with the substrate 58 from the light emitting unit of the functional element is formed on the side of the groove 64. A high resistance region 72 having an electrically high resistance, is formed in depth deeper than the thickness of the unit 70 of the functional element toward the inside of the substrate 58 from the surface in the bottom of the groove 64.

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-based optical memory device integrated with a heterojunction phototransistor and a light emitting diode as shown in FIG. 7 (Technical digest 20C3-2, Integrated Optics a
nd Optical-fiber Communication (IOOC) 1989, Kobe, Ja
pan). This optical memory device has a structure in which light is incident from the substrate 100 side and output light 102 is emitted above the substrate 100. Therefore, the thickness of the substrate 100 is thicker than the device size, and the input light 101 from the back surface of the substrate is There are many problems to be solved, such as crosstalk of input light between adjacent elements that occurs when reaching each element on the substrate surface, difficulty in supporting the substrate 100, and heat dissipation problem in large-scale integration. Although FIG. 7 shows a cross-sectional view of the integrated optical functional device, hatching is not drawn in the cross-section for easy understanding of each layer.

[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. 10 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 by which 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 41. As shown in FIG. It changes depending on the intensity of the incident light, and the state of the element is determined only on the load line 85 by the load resistor 42 connected in series to the optical function element. Therefore, three characteristics are realized by changing the load resistor 42 and the bias voltage 43. Is done.

For example, when the load resistance 42 is large, the current flowing through the element is limited to a small value, so that the input light is reduced to 0.
The current increases monotonically and the output light also monotonically increases (optical differential gain characteristic). 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. 9, 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 90.
Shows the characteristic curves when there is no input light.

However, since the optical functional element vertically integrated on the substrate cannot be constructed to have a thickness smaller than that required for the light emitting portion and the light receiving portion to generate and absorb light, the overall thickness of the element increases. As a method for laminating the elements, a method is generally used in which each layer of the optical functional element is first laminated on a flat substrate in parallel with the substrate, and then each element is separated by mesa formation. For this reason, if an element is to be electrically separated by forming a mesa, it is necessary to perform etching so that the substrate reaches the thickness of the element, and the step between the etched portion and the non-etched portion becomes large. Process problems such as electrode breakage are likely to occur.

FIG. 11 is a cross-sectional view schematically showing the disconnection of electrodes. A light receiving portion 93 and a light emitting portion 9 are formed on a semiconductor substrate 92.
The electrode 91 is extended from the upper surface of the light emitting portion 94 to the surface of the substrate 92 at the end portion of the semiconductor functional element in which 4 is stacked, and the electrode 91 is disconnected. As described above, as the thickness of the light receiving portion 93 and the light emitting portion 94, which are laminated, increases, a problem such as electrode breakage occurs during electrode formation. Although it is possible to fill the step using SiO ₂ or the like, complete flattening is difficult.

Further, since the optical functional element is sensitive to the light input to the element, if the elements are formed adjacent to each other in an array as shown in FIG. 12, the leaked light from the adjacent elements 96 and 97 is generated. Since 98 causes an erroneous operation in which the elements are turned on, optical separation in the direction parallel to the substrate between the elements is also necessary. For optical isolation, it is often practiced to stack a layer that blocks light (eg, electrodes) along the grooves between mesas after the formation of mesas as described above. When the breakage occurs, a problem of poor optical separation easily occurs. Therefore, the process of the optical functional device must ensure that the adjacent devices are electrically and optically separated from each other, and the step formed during the process is made as small as possible. An object of the present invention is to solve the problem of forming a step due to electrical and optical isolation between elements, which is a problem in the process of an optical functional element.

[0010]

FIG. 1 is a sectional view showing the basic structure of the present invention. A semiconductor optical function element having a structure in which a light receiving section 70 is provided on a semiconductor substrate 58, a light emitting section 62 is further provided thereon, and input light and output light are input and output through a window section 73 provided above the light emitting section 62, The forbidden band width of the semiconductor material forming the light emitting portion 62 of the optical functional element is larger than the main peak energy of the input light, and the forbidden band width of the semiconductor material forming the light emitting portion 70 of the optical functional element is the main peak energy of the input light. A part of the output light generated from the light emitting portion 62 is equal to or smaller than that and is returned to the light receiving portion 70, and is absorbed by the light receiving portion 70 to have an optical feedback effect. This effect has a non-linear response between the input light and the output light.

In addition, one-dimensional or two-dimensional on the semiconductor substrate 58.
Individual elements 6 of semiconductor optical functional elements arranged in a three-dimensional array
0, an element isolation groove 64 is formed at the same depth as the thickness of the light emitting portion 62 of the semiconductor optical functional element, and the light emitting portion 66 of the semiconductor optical functional element is formed on the side surface of the element isolation groove 64.
A light-blocking region 68 for blocking light emitted from the substrate 58 in a direction parallel to the substrate 58 is formed, and a depth equal to or larger than the thickness of the light-receiving portion 70 is formed in the bottom of the element isolation trench 64 from its surface toward the inside of the semiconductor substrate 58. The feature is that a high resistance region 72 having a high resistance is formed.

Regarding the electrical isolation of the individual optical function elements, a mesa portion formed more than the thickness of the light emitting portion 62 and a high resistance formed more than the thickness of the light receiving portion 70 at the bottom between the formed mesas. The feature is that it is performed in the area 72. Also, regarding the optical separation of the individual optical function elements, the light emitting unit 6
A light-shielding region 68 for shielding light is formed on the side surface of the mesa portion formed to have a thickness of 2 or more, so that light emitted from the light emitting portion 62 of the semiconductor optical function element in the direction parallel to the substrate 58 is adjacent to the optical function. The feature is that the light receiving portion 70 of the element is not absorbed.

[0013]

In the present invention, the depth of the element isolation groove 64 becomes the thickness of the light emitting portion 62 while satisfying the conditions of electrical isolation and optical isolation between elements, and the light emitting portion 62 and the light receiving portion 70 are simply combined. The step is smaller than the case where the separation groove is formed to a depth that matches the thickness, and problems such as disconnection of electrodes and insulating films formed along the upper and side surfaces of the optical functional element are alleviated.

[0014]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a sectional view showing an embodiment of the present invention. The semiconductor functional element according to this embodiment has an n-A substrate on an n-GaAs substrate 119.
l _0.4 Ga _0.6 As emitter layer 118, p-GaAs base layer 117, n-GaAs collector layer 116, n-Al
_0.4 Ga _0.6 Asn-type cladding layer 115, undoped Al _0.2
Ga _0.8 As active layer 114, p-Al _0.4 Ga _0.6 Asp
The mold clad layer 113 and the p-GaAs cap layer 112 are laminated in this order. n-Al _0.4 Ga _0.6
Asn-type cladding layer 115, undoped Al _0.2 Ga _0.8 As
The active layer 114 and the p-Al _0.4 Ga _0.6 Asp clad layer 113 constitute a light emitting diode (light emitting portion), and the light emitting diode 130 has a double heterojunction structure in order to improve the light emission efficiency.

Further, the n-Al _0.4 Ga _0.6 As emitter layer 118, the p-GaAs base layer 117, and the n-GaAs collector layer 116 constitute a light-receiving portion, and the light-receiving portion 132 has an electron injection efficiency from the emitter to the base. To raise
It is composed of a heterojunction photophoresistor using an emitter with a large forbidden band. At the top of the device, p-
The GaAs cap layer 112 is etched to form p-Al.
_An incident window 128 reaching the _0.4 Ga _0.6 Asp type clad layer 113 is formed so that incident light and outgoing light can enter and exit. An n-type ohmic common electrode 120 is formed on the back surface of the n-GaAs substrate 119, and a predetermined voltage is applied between the n-type ohmic common electrode 120 and the p-type ohmic upper electrode 110.

A light emitting diode 130 is provided between the individual devices.
An element isolation trench 134 reaching the surface position of the n-GaAs collector layer 116 is formed at the same depth as the thickness of the. The element separating groove 134 is formed so as to surround the element when a plurality of individual elements are arranged on the substrate.

Further, on the p-GaAs cap layer 112 and on the side surface of the light emitting diode 130 (element isolation groove 134).
SiO ₂ insulating layer 111 is formed on a side surface of the p-type ohmic upper electrode 110, and a p-type ohmic upper electrode 110 formed on the SiO ₂ insulating layer 111 forms a light-blocking region that blocks light. Also,
A high resistance region 121 having a high electrical resistance is formed in the bottom of the element isolation groove 134 from the surface thereof toward the inside of the n-GaAs substrate 119 to a depth equal to or larger than the thickness of the light receiving portion 132.

Next, an example of the manufacturing method of this embodiment will be described. First, as shown in FIG. 3, an n-GaAs substrate 119 is formed.
N-Al _0.4 Ga _0.6 As emitter layer 118 (thickness 0.2 μm, carrier concentration 1 × 10 ¹⁷ cm to ³ ), p-G
aAs base layer 117 (thickness 0.1 μm, carrier concentration 1 × 10 ¹⁸ cm to ³ ), n-GaAs collector layer 116
(Thickness 1 μm, carrier concentration 1 × 10 ¹⁵ cm to ³ ), n−
Al _0.4 Ga _0.6 Asn-type cladding layer 115 (thickness 1 μm
m, carrier concentration 1 × 10 ¹⁸ cm ³ ), undoped Al _0.2
Ga _0.8 As active layer 114 (thickness 0.1 μm, carrier concentration 1 × 10 ¹⁵ cm ³ ), p-Al _0.4 Ga _0.6 Asp type cladding layer 113 (thickness 1 μm, carrier concentration 1 × 10 5
¹⁸ cm ~ ³ ), p-GaAs cap layer 112 (thickness: 0.
2 μm and a carrier concentration of 2 × 10 ¹⁸ cm ³ ) were sequentially stacked by using the metal organic chemical vapor deposition method.

Subsequently, as shown in FIG. 4, NH ₄ OH: H ₂ O ₂ = 4: 1, 20 ° C., 40 seconds (depth: 2.5 μm) using an etching mask produced by photolithography technique. Under the conditions, etching for separating the light emitting portion was performed. By this etching, the element isolation groove 134 is formed.

On this, as shown in FIG. 5, a SiO ₂ insulating film 111, which also serves as an ion implantation mask and element insulation and passivation, is formed by plasma CVD to 300
nm deposition. By using an etching mask by photolithography, only the bottom of the isolation trench 134 is SiO ₂
The insulating film 111 was etched and used as a mask for ion implantation. The ion implantation conditions are that protons are used as the ion species and the implantation energy level is 140 k.
The eV and dose amount were set to 10 ¹⁴ cm to ² . The high resistance region 121 is formed by this ion implantation. The ion implantation conditions were set so that the proton distribution peak was located at the depth of the base layer (1 μm from the bottom of the groove), and the carrier concentration of the base layer was 1 × 10 ¹⁸ cm ~ ^3. To compensate for the high resistance region 12
The dose amount that can form 1 was selected.

Next, as shown in FIG. 6, photolithography
Using Raffy again SiO₂Pattern on insulating film 111
To form an electrode 1 on the p-GaAs cap layer 112.
A window for contacting with 10 is formed. For etching
HF: NH_FourF = 1: 5, 20 ° C., 60 seconds are used
It was Then, using an etching mask, NH_FourOH: H₂
O₂= 1: 20, 20 ° C, p-under the condition of 5 seconds
By selectively etching the GaAs cap layer 112,
The light input / output window 128 is formed. Next, the p-side electrode Cr / A
uZn / Au (300 nm) is a p-GaAs cap layer
112 and SiO ₂Evaporate on the insulating film 111 and lift
On the p-type ohmic by forming the electrode pattern by the
The partial electrode 110 is formed.

Finally, the back surface of the n-GaAs substrate 119 was lapped with alumina powder to a thickness of 100 μm, and the n-side electrode AuGe / Ni / Au of 100 μm was laid on the back surface of the substrate.
nm vapor deposition to form the n-type ohmic common electrode 120,
Finished the manufacturing process. The p-type ohmic upper electrode 110 also has a function of horizontally confining the light of the light emitting unit 130. The step formed on the array of elements is 2.5
Since it is μm, the device can be manufactured without any problem in forming the p-type ohmic upper electrode 110, and the conventional optical functional device characteristics shown in FIGS. 9 and 10 can be obtained.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, other than the material system used in the above-mentioned embodiment, a semiconductor material such as InP or another composition may be used. This is particularly effective when the elements are arranged in a one-dimensional or two-dimensional array and the elements are likely to electrically and optically interfere with each other. Although the semiconductor layer is formed by using the metal organic chemical vapor deposition method in the above-mentioned embodiment, the present invention is also applicable to the case where the semiconductor layer is grown by other means capable of forming a thin film such as liquid phase growth method and molecular beam growth method. The structure of can be applied. Further, it is obvious that the manufacturing method of the above-mentioned embodiment is only one example, and that it can be manufactured by using various manufacturing processes used for manufacturing a semiconductor.

[0024]

According to the first aspect of the invention, an element isolation groove having the same depth as the thickness of the light emitting portion is provided, and a light shielding region is formed on the side surface of the element isolation groove, and the element isolation groove is formed. In the bottom of the groove, from the surface to the inside of the semiconductor substrate, by providing a high resistance region of high electrical resistance to a depth equal to or greater than the thickness of the light receiving portion, without impairing the original characteristics of the functional element,
It is possible to solve process problems such as disconnection of electrodes due to electrical and optical isolation grooves of the device, which has been a problem in manufacturing the optical functional device.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing an embodiment of a semiconductor functional device of the present invention.

FIG. 3 is a cross-sectional view showing the manufacturing process of the present embodiment.

FIG. 4 is a cross-sectional view showing the manufacturing process of the present embodiment.

FIG. 5 is a cross-sectional view showing the manufacturing process of the present embodiment.

FIG. 6 is a cross-sectional view showing the manufacturing process of the present embodiment.

FIG. 7 is a cross-sectional view of a conventional semiconductor functional element.

FIG. 8 is a cross-sectional view of a semiconductor functional device which has not been known and has already been proposed.

FIG. 9 is a diagram showing voltage-current characteristics of a semiconductor functional element.

FIG. 10 is a diagram for explaining three characteristics of the semiconductor functional element.

FIG. 11 is a cross-sectional view for explaining disconnection of electrodes.

FIG. 12 is a cross-sectional view for explaining optical crosstalk between individual elements.

[Explanation of symbols]

 Reference numeral 58,119 Semiconductor substrate 70,132 Light receiving portion 62,130 Light emitting portion 73,128 Window portion 64,134 Element separating groove 68 Light shielding area 72,121 High resistance area

Claims (1)

Claim: What is claimed is: 1. A structure in which a light receiving portion is provided on a semiconductor substrate, a light emitting portion is further provided thereon, and input light and output light are input and output through a window portion provided on the light emitting portion side. And 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 the main peak energy of the input light. A part of the output light generated from the light emitting unit, which is smaller than that, is returned to the light receiving unit, and has a non-linear response between the input light intensity and the output light intensity due to the optical feedback effect absorbed by the light receiving unit. A semiconductor optical functional element characterized by comprising: a semiconductor optical functional element arranged in a one-dimensional or two-dimensional array on the substrate; Element isolation groove And a light-shielding region for shielding light emitted from the light emitting portion in a direction parallel to the substrate is formed on a side surface of the element isolation groove, and the semiconductor isolation substrate is formed on the bottom of the element isolation groove from its surface. A semiconductor optical functional device, characterized in that a high resistance region having a high resistance is formed inwardly to a depth equal to or larger than the thickness of the light receiving portion.