JP3147133B2 - Horizontal light receiving element and method of forming the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a horizontal light receiving element having high sensitivity and high response speed and a method of forming the same.

[0002]

2. Description of the Related Art In the fields of optical communication technology and optical measurement technology, a light receiving element having a high-speed response characteristic is required. The light receiving elements are roughly classified into vertical light receiving elements and horizontal light receiving elements.

[0003] The vertical light receiving element has a structure in which an electric carrier excited by an optical signal incident perpendicularly to the light receiving surface, for example, travels in a direction perpendicular to the semiconductor substrate. In order to output the carrier as an electric signal, an electrode is formed on the front surface side of the semiconductor substrate, and an electrode is formed inside or on the back surface of the semiconductor substrate. Therefore, it is difficult to flatten the semiconductor substrate. And the problem that an insulating substrate cannot be used.

On the other hand, a horizontal light receiving element has a structure in which an electric carrier excited by, for example, an optical signal incident perpendicularly to a light receiving surface travels in a direction parallel to a semiconductor substrate. Furthermore, in order to output the carrier as an electric signal, a pair of electrodes may be formed on the surface of the semiconductor substrate, so that the manufacturing process is simplified and an integrated circuit including other elements is easily formed. There are advantages.

As the horizontal light receiving element, a photoconductive light receiving element having a vertical sectional structure shown in FIG. 8, a PIN photodiode type light receiving element having a vertical sectional structure shown in FIG.
An MSM type light receiving element having a vertical cross-sectional structure shown in FIG.

The photoconductive light-receiving element shown in FIG. 8 has a light-receiving layer of Ga _0.47 In _0.53 As grown on an InP substrate and a pair of n-type ohmic electrodes formed on the light-receiving layer. It has sensitivity to light having a wavelength of 0.7 μm or less. In addition, a GaAs substrate is used instead of the InP substrate, and there is a photoconductive type light receiving element in which a GaAs crystal light receiving layer is formed on the GaAs substrate and a pair of n-type ohmic electrodes are formed. , About 0.9μm
It has sensitivity to light of the following wavelengths.

In the PIN photodiode type light receiving element shown in FIG. 9, an n-type ion implantation region and a p-type ion implantation region are formed on the surface layer of a GaInAs light-receiving layer crystal-grown on an InP substrate. An n-type ohmic electrode is formed on the region, and a p-type ohmic electrode is formed on the p-type ion-implanted region. Incidentally, GaAs is used instead of the InP substrate.
A GaAs crystal light-receiving layer is formed on the GaAs substrate, a pair of n-type ohmic electrodes and a p-type ohmic electrode are formed as shown in the figure, and further, an n-type ohmic electrode and a p-type ohmic electrode are applied. Some are formed respectively.

In the MSM type light receiving device shown in FIG. 10, an Al _0.48 Ga _0.52 As Schottky barrier enhancement layer is formed on the upper surface of a Ga _0.47 In _0.53 As light absorption layer crystal-grown on an InP substrate. A pair of Schottky electrodes are formed on the upper surface of the layer. That is, Ga _0.47 In
_Since it is difficult to form a Schottky junction directly on the _0.53 As light receiving layer, an Al _0.48 Ga _0.52 As Schottky barrier enhancement layer is formed. In addition, instead of the InP substrate, Ga
When an As substrate is applied and a GaAs crystal light-receiving layer is formed on the GaAs substrate, a Schottky electrode is often directly deposited on the light-receiving layer.

[0009]

By the way, the response speed of the lateral light receiving element is governed by the transit time until the carrier excited by the optical signal reaches the electrode, and the traveling speed of the carrier depends on the electric field strength in the light receiving layer. In general, the higher the electric field intensity, the higher the traveling speed. More specifically, based on the electric field intensity distribution of FIG. 11 corresponding to FIG. 8, for example, the voltages (−5 V and +5
The intensity of the electric field generated in the light receiving layer due to V) is strong near the surface layer of the light receiving layer and becomes weaker as it goes deeper. Therefore, the response speed of the light receiving element is governed by the traveling speed of the carrier traveling deep.

Therefore, as a means for improving the response speed of the light receiving element, it is conceivable to detect only carriers traveling in a strong electric field by reducing the thickness of the light receiving layer. If the thickness is reduced, the light-receiving layer cannot sufficiently absorb the incident optical signal, which causes a problem that the sensitivity is reduced.

The present invention has been made in view of such conventional problems, and has as its object to provide a horizontal light receiving element having high sensitivity and excellent response speed, and a method of forming the same.

[0012]

In order to achieve the object of the present invention, a horizontal light receiving element is constructed based on the following principle.

That is, as described with reference to FIG. 11, most of the carriers generated in the light-receiving layer travel along the deep part (the part close to the substrate) of the light-receiving layer. Therefore, if the traveling speed of the carrier traveling deep in the light receiving layer is increased, the response speed of the light receiving element can be improved even if the thickness of the light receiving layer is increased.

The following table shows GaAs and Ga _0.47 In _0.53 A
s, and electron mobility and hole mobility of each material of InAs.

[0015]

[Table 1]

When these characteristics are evaluated, Ga _(1-x) In
electron mobility in _x As increases as x increases. Therefore, the present invention improves the traveling speed of electrons traveling along the deep part of the light receiving layer by forming a layer of Ga _(1-x) In _x As with a large x at the interface between the light receiving layer and the substrate. (Increase), and thus the response speed and sensitivity of the light receiving element are improved.

Further, Ga _(1-x) In _x A is formed on a GaAs substrate.
When s (where x> 0.1) is grown or Ga _(1-x) In _x As (where x> 0.6) is grown on an InP substrate, the crystal is grown on the substrate. Since the crystal lattice constant is large, compressive strain is generated in the crystal. This compressive strain changes the structure of the energy band of the crystal, and changes the running characteristics of the carrier. In particular, in a crystal having compressive strain, the hole mobility is significantly improved, and
When Ga _0.32 In _0.68 As (corresponding to 1% strain) is grown on the nP substrate, Ga
It is known that the hole mobility can be improved about three times as compared with the case where _0.47 In _0.53 As (unstrained) is grown (“ELECTRON AND HOLE MOBILITY IN MODULATI”).
ON DOPEDGaInAs-AlInAs STRAINED LAYER SUPERLATTECE
”K. Hirose, T. Mizutani, Journal of Crystal Growth
vol.81 page130 (1987)). Therefore, the present invention improves the traveling speed of holes by forming a crystal layer having compressive strain with respect to the substrate at the interface between the light receiving layer and the substrate, and thus improves the response speed of the light receiving element. And improved sensitivity.

As an embodiment of the present invention, a Ga _(1-x) In _x As (where x> 0.6) crystal layer is formed on an InP substrate, and Ga _0.47 In _0.53 is further formed on the crystal layer.
In the lateral light receiving element having the As light receiving layer, the carrier generated by the optical signal is Ga _(1-x) In _x A
Since the s (where x> 0.6) crystal layer travels at high speed, a light receiving element with improved response speed is realized.

In another embodiment, Ga _(1-x) In _x As (where x> 0.times.0 ₎ is formed on a GaAs substrate.
1) A crystal layer is formed, and GaAs is further formed on the crystal layer.
In the lateral light receiving element in which the s light receiving layer is formed, the carrier generated by the optical signal is Ga _(1-x) In _x A
Since the s (where x> 0.1) crystal layer travels at a high speed, a light receiving element with improved response speed is realized.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. First, the structure will be described with reference to FIG. 1. On a Fe-doped semi-insulating InP substrate 1, a Ga _0.32 In _0.68 As crystal layer 2 and a Ga 3
The light receiving layer 3 of _0.47 In _0.53 As is formed in order.
Here, gallium (Ga) material for the crystal layer 2 and the light receiving layer 3 is triethylgallium, indium (In) material is trimethylindium, and arsenic (As) material is arsine. Then, in the manufacturing process, the crystal layer 2 and the light receiving layer 3 having different compositions are grown by adjusting the flow ratio of triethylgallium and trimethylindium. The thickness of the crystal layer 2 was 100 nm, and the thickness of the light receiving layer 3 was 1.5 μm.

Further, a pair of ohmic electrodes 4a and 4b are formed on the surface of the light receiving layer 3 on which the crystal is grown. still,
For the ohmic electrodes 4a and 4b, an alloy of germanium and gold is applied, the distance between the electrodes is 4 μm, and the thickness is 100 n.
m is formed in a comb shape.

According to the lateral light receiving element having such a structure, for example, as shown in FIG.
When -5V and + 5V voltages are applied to 4b, an electric field intensity distribution is generated in the light receiving element as shown in the figure. The carriers generated inside by the incidence of the optical signal hν and reaching the deep portion of the light-receiving layer 3 travel at high speed in the region W of the strained layer having high electron mobility and hole mobility, so that the response speed is improved. A light receiving element is realized.

Next, a second embodiment will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 1 are indicated by the same reference numerals. First, to explain the structure, this is PI
This is an N-photodiode type light receiving element, in which a Ga _0.32 In _0.68 As crystal layer 2 and a Ga _0.47 In are formed on a semi-insulating InP substrate 1 doped with Fe by using a metal organic chemical vapor deposition method.
The light receiving layer 3 of _0.53 As is formed in order. here,
The raw materials and manufacturing method of the crystal layer 2 and the light receiving layer 3 are the same as those in the first embodiment.

Further, an n-type implanted region 5a is formed by implanting Si ions into a predetermined portion of the surface layer of the light-receiving layer 3 on which the crystal has been grown, and a p-type implanted region 5b is formed by doping Be. Have been. Further, the n-type ohmic electrodes 6a, p
A p-type ohmic electrode 6b is formed on each of the mold injection regions 5b. Note that an alloy of germanium and gold or the like is applied to the n-type ohmic electrode 6a, and the p-type ohmic electrode 6b
Is applied with an alloy of zinc and gold.

Even in the PIN photodiode type light receiving element having such a structure, the carriers generated inside the element and reaching the deep part of the light receiving layer 3 have the electron mobility and the hole as shown in FIG. Since the vehicle travels at a high speed on the strained layer having high mobility, a light receiving element with improved response speed is realized.

Next, a third embodiment will be described with reference to FIG. In FIG. 3, portions corresponding to the components in FIG. 1 are indicated by the same reference numerals. First, the structure will be described.
This is an M-type light receiving element, which is semi-insulating In doped with Fe.
A buffer layer 7 of InP is formed on the P substrate 1, and a layer 8 of Ga _0.61 In _0.39 As is further formed on the buffer layer 7,
Further, on the layer 8, Ga was grown using metal organic chemical vapor deposition.
A crystal layer 2 of _0.32 In _0.68 As and a light receiving layer 3 of Ga _0.47 In _0.53 As are sequentially formed. Here, the raw materials and manufacturing method of the crystal layer 2 and the light receiving layer 3 are the same as those in the first embodiment.

Further, Al _0.48 In _0.52
An As layer 9 is formed, and a pair of Schottky electrodes 10 a and 10 b are formed on the surface of the layer 9. In addition, Al
The layer 9 of _0.48 In _0.52 As has a thickness of about 0.1 μm, and trimethyl aluminum is applied as a raw material of Al.
The Schottky electrodes 10a and 10b are made of an alloy of germanium and gold, and are formed in a comb shape with a mutual electrode spacing of 4 μm and a thickness of 100 nm.

Even in the MSM type light receiving element having such a structure, carriers generated inside the element and reaching the deep part of the light receiving layer 3 have electron mobility and hole mobility as shown in FIG. Since the light-emitting element travels at a high speed on a strained layer having a high response speed, a light-receiving element with improved response speed is realized. Further, the InP buffer layer 7
By interposing the Ga _0.61 In _0.39 As layer 8 between the light-receiving layer 2 and the light-receiving layer 2, the strain is canceled and the crystallinity is effectively maintained.

Although the buffer layer 7 of InP is formed in FIG. 3, the buffer layer 7 is not limited to this, and a buffer layer having an arbitrary structure may be used. In FIG.
A layer 9 of Al _0.48 In _0.52 As is directly formed on the light receiving layer 3 of _0.47 In _0.53 As, and a quaternary layer of AlGaInAs or a superlattice made of these materials is provided between the layer 9 and the light receiving layer 3. May be formed. When such a structure is inserted, the response speed can be further improved.

Next, a fourth embodiment will be described with reference to FIG. First, the structure will be described. This is an element using a GaAs substrate. A GaAs substrate 11 is formed on a Ga _0.84 In _0.15 As crystal layer 12 by metalorganic vapor phase epitaxy.
The light-receiving layer 13 of aAs is formed in order. here,
The gallium (Ga) source of the crystal layer 12 and the light receiving layer 13 is triethylgallium, the indium (In) source is trimethylindium, and the arsenic (As) source is arsine. Then, in the manufacturing process, the crystal layer 12 and the light receiving layer 13 having different compositions are grown by adjusting the flow ratio of triethylgallium and trimethylindium.

Further, on the surface of the light receiving layer 13 on which the crystal has grown,
A pair of n-type ohmic electrodes 14a and 14b are formed. The n-type ohmic electrodes 14a and 14b are made of an alloy of germanium and gold.

According to the lateral light receiving element having such a structure, carriers generated inside the element and reaching the deep portion of the light receiving layer 13 have the same electron mobility and hole mobility as shown in FIG. Since the vehicle travels at a high speed on a high strain layer, a light receiving element with improved response speed is realized.

Next, a fifth embodiment will be described with reference to FIG. In FIG. 5, portions corresponding to the components in FIG. 4 are denoted by the same reference numerals. First, to explain the structure, this is PI
N photodiode type light receiving element, GaAs substrate 1
First, using a metal organic chemical vapor deposition method, Ga _0.84 In _0.15
An As crystal layer 12 and a GaAs light receiving layer 13 are sequentially formed. Here, the raw materials and manufacturing method of the crystal layer 12 and the light receiving layer 13 are the same as those of the fourth embodiment.

Further, an n-type implanted region 15a is formed by implanting Si ions into a predetermined portion of the surface layer of the light-receiving layer 13 where the crystal has been grown, and a p-type implanted region 15b is formed by doping Be. Have been. Further, the n-type ohmic electrode 16a is provided on the n-type implanted region 15a, and the p-type ohmic electrode 1 is provided on the p-type implanted region 15b.
6b are respectively formed. The n-type ohmic electrode 1
An alloy of germanium and gold is applied to 6a, and an alloy of zinc and gold is applied to the p-type ohmic electrode 16b.

Even in the PIN photodiode type light receiving element having such a structure, carriers generated inside the element and reaching the deep part of the light receiving layer 13 are similar to those shown in FIG.
Since the high-speed traveling through the strained layer having high electron mobility and high hole mobility, a light receiving element with improved response speed is realized.

Next, a sixth embodiment will be described with reference to FIG. In FIG. 6, portions corresponding to the components in FIG. 4 are denoted by the same reference numerals. First, the structure will be described.
This is an M-type light receiving element, and an Al _0.3 Ga
A buffer layer 17 of _0.7 As is formed, and a Ga _0.85 In layer is formed on the buffer layer 17 by metal organic chemical vapor deposition.
A crystal layer 12 of _0.15 As and a light receiving layer 13 of GaAs are sequentially formed.

Further, an AlGaAs layer 18 is formed on the upper surface of the light receiving layer 13, and a pair of Schottky electrodes 19a and 19b are formed on the surface of the layer 18.

Even in the MSM type light receiving element having such a structure, the carriers generated inside the element and reaching the deep part of the light receiving layer 13 have the electron mobility and the hole mobility as shown in FIG. Since the light-emitting element travels at a high speed on a strained layer having a high response speed, a light-receiving element with improved response speed is realized.

Further, since the buffer layer 17 of Al _0.3 Ga _0.7 As is formed between the GaAs substrate 11 and the crystal layer 12, the carrier generated by the optical signal is transferred to a crystal having a high electron mobility and a high hole mobility. As a result of being able to be effectively confined in the layer 12, it contributes to the improvement of the response speed. That is, the difference in band gap between the crystal layer 12 of Ga _0.85 In _0.15 As and the light-receiving layer 13 of GaAs is small, and the effect that the carriers generated by the optical signal leak below the crystal layer 12 is caused by the buffer layer 17. This is because it can be suppressed by a large band gap.

[0040]

As described above, according to the present invention, I
In a lateral light receiving element using an nP substrate, Ga _(1-x) In _x A having a large electron mobility is provided between the light receiving layer and the substrate.
Since a crystal layer of s (where x> 0.6) is formed and the electron mobility and the hole mobility are improved by the compressive strain of this crystal layer, the carrier traveling along the deep part of the light receiving layer is improved. Even if the traveling speed is improved (increased) and the light receiving layer is relatively thick, the response speed can be improved and high sensitivity can be realized.

In the case of a lateral light receiving element using a GaAs substrate, Ga _(1-x) In _x As (where x> 0.1) having a high electron mobility is provided between the light receiving layer and the substrate. And the electron mobility and the hole mobility are improved by the compressive strain caused by the crystal layer, so that the traveling speed of the carrier traveling along the deep part of the light receiving layer is improved (increased).
In other words, even if the light receiving layer is relatively thick, the response speed can be improved and high sensitivity can be realized.

As described above, according to the present invention, it is possible to realize a horizontal light-receiving element having high sensitivity and high-speed response and having a simple structure. It exhibits excellent effects such as being applicable to the measurement field and the like.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a structure of an embodiment of a photoconductive lateral light receiving element using an InP substrate.

FIG. 2 is a partial cross-sectional view showing the structure of one embodiment of a PIN photodiode type lateral light receiving element using an InP substrate.

FIG. 3 is a partial cross-sectional view showing a structure of an embodiment of an MSM type lateral light receiving element using an InP substrate.

FIG. 4 is a partial cross-sectional view showing a structure of one embodiment of a photoconductive lateral light receiving element using a GaAs substrate.

FIG. 5 is a partial cross-sectional view showing the structure of one embodiment of a PIN photodiode type lateral light receiving element using a GaAs substrate.

FIG. 6 is a partial cross-sectional view showing the structure of one embodiment of an MSM type lateral light receiving element using a GaAs substrate.

FIG. 7 is an explanatory view schematically showing an electric field distribution inside the device of the embodiment shown in FIGS. 1 to 6;

FIG. 8 is a partial cross-sectional view showing a structure of a conventional example of a photoconductive horizontal light receiving element.

FIG. 9 is a partial sectional view showing the structure of a conventional example of a PIN photodiode type horizontal light receiving element.

FIG. 10 is a partial cross-sectional view showing the structure of a conventional example of an MSM type horizontal light receiving element.

FIG. 11 is an explanatory view schematically showing an electric field distribution inside the element of the conventional example shown in FIGS. 8 to 10;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... InP board, 2 ... crystal layer, 3 ... light receiving layer, 4a, 4
b, 14a, 14b... n-type ohmic electrodes, 5a, 15
a: n-type implantation region, 5b, 15b: p-type implantation region, 6
a, 16a ... n-type ohmic electrode, 6b, 16b ... p-type ohmic electrode, 7 ... InP layer, 8 ... Ga _0.61 In _0.39
As layer, 9... Al _0.48 In _0.52 As layer, 10a, 10
b, 19a, 19b: Schottky electrode, 17: Al _0.3
Ga _0.7 As layer, 18... AlGaAs layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/10-31/119

Claims (13)

(57) [Claims] _1. Ga _(1-x) I formed on an InP substrate
n _x As (where, x> 0.6) lateral light receiving element and having a crystal layer composed of, a light receiving layer composed of a formed on the crystal layer Ga _0.47 In _0.53 As. 2. The lateral light receiving device according to claim 1, wherein the thickness of the crystal layer is set to be equal to or less than a critical film thickness with respect to a strain amount with respect to the InP substrate. 3. The horizontal light receiving element according to claim 1, wherein an ohmic electrode is formed at a predetermined position on the surface of the light receiving layer. 4. An n-type and a p-type on a surface layer of a predetermined portion of the light receiving layer.
A n-type impurity region, an n-type ohmic electrode in the n-type impurity region, and a p-type ohmic electrode in the p-type impurity region, thereby having a PIN photodiode type structure. The horizontal light-receiving element according to claim 1. 5. An MSM type structure in which a barrier layer made of AlInAs is formed on the light receiving layer and a pair of Schottky electrodes are further formed on the barrier layer. 2. The horizontal light receiving element according to 1. 6. Ga _(1-x) formed on a GaAs substrate
A horizontal light-receiving element comprising: a crystal layer made of In _x As (where x>0.1); and a light-receiving layer made of GaAs formed on the crystal layer. 7. The lateral light receiving device according to claim 6, wherein the thickness of the crystal layer is set to be equal to or less than a critical film thickness with respect to a strain amount with respect to the GaAs substrate. 8. The horizontal light receiving element according to claim 6, wherein an ohmic electrode is formed at a predetermined position on the surface of the light receiving layer. 9. An n-type and a p-type on a predetermined surface layer of the light-receiving layer.
A n-type impurity region, an n-type ohmic electrode in the n-type impurity region, and a p-type ohmic electrode in the p-type impurity region, thereby having a PIN photodiode type structure. The horizontal light receiving element according to claim 6. 10. An MSM structure having a barrier layer made of AlGaAs formed on the light receiving layer and a pair of Schottky electrodes formed on the barrier layer. 7. The horizontal light receiving element according to 6. 11. An AlGa film formed on a GaAs substrate.
A buffer layer composed of As, a crystal layer composed of Ga _(1-X) In _x As (where x> 0.1) further formed on the buffer layer, and a GaAs layer further formed on the crystal layer. A light receiving element comprising: a light receiving layer comprising: 12. InP is formed by metal organic chemical vapor deposition.
On the substrate, Ga _(1-x) In _x As (where x> 0.6)
A method for forming a lateral light receiving element, comprising sequentially growing a crystal layer made of Ga _0.47 In _0.53 As and a light receiving layer made of Ga _0.47 In _0.53 As. 13. A method of forming GaAs by metal organic chemical vapor deposition.
Ga _(1-x) In _x As (provided that x> 0.
A method for forming a lateral light receiving element, comprising sequentially growing a crystal layer made of 1) and a light receiving layer made of GaAs.