JPH0548135A - Semiconductor photodetector and its manufacture - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process and improve the efficiency of a semiconductor photodetector. CONSTITUTION:A semiconductor layer 3 of the first conductivity type is provided on part of a semiconductor substrate 1 by epitaxial growth by using a suitable mask 2 and a semiconductor superlattice light absorbing layer 5 having a super lattice which is perpendicular to the surface of the substrate 1 is formed by using the side of the layer 3 as the growth seed of the layer 5. Therefore, the surface vertical direction having the largest area can be utilized as the incident direction of light. In addition, incident light can be effectively converted into optical signals and, at the same time, a large number of devices can be formed in the same substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor photodetector using a semiconductor material and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, Applied Physics Letter.
50 (16), p.1092 Conventional GaAs / AlGa
It is sectional drawing which shows the infrared detection device which used As superlattice. In this figure, 1 is a semiconductor substrate, 5 is a semiconductor superlattice light absorption layer, 6 is an electrode formation layer formed on this semiconductor superlattice light absorption layer 5, 7 is an electrode, and 9 is formed on the semiconductor substrate 1. The formed electrode forming layers 10 are light incident surfaces obtained by polishing the semiconductor substrate 1 at an angle of 45 degrees.

Next, a manufacturing method will be described. On the semiconductor substrate 1, for example, a semi-insulating GaAs substrate, a second carrier type semiconductor layer (electrode forming layer) 9 having a high carrier concentration is formed by a semiconductor crystal growth method such as a metal organic chemical vapor deposition method or a molecular beam epitaxy method, For example, an n-type GaAs layer is grown to about 1 μm. Thereafter, the semiconductor superlattice light absorption layer 5, for example, 40ÅGaAs / 300ÅAl, is grown by the same growth means.
50 cycles of _0.31 Ga _0.69 As are formed. Further, a second conductivity type semiconductor layer (electrode formation layer) 6 similar to the semiconductor layer 9 is provided on the semiconductor superlattice light absorption layer 5, and thereafter, the end portion of the semiconductor substrate 1 is placed on the element formation surface by 45 °. The light incident surface 10 is formed by polishing at an angle of degrees. Finally, an electrode 7, for example Au / Ge / N, is formed on the surface of the second conductivity type semiconductor layers 6 and 9.
A metal such as i is vapor-deposited to complete the device.

A light incident surface 10 which is a polished surface of the substrate of this device.
Therefore, for example, when an infrared ray having a wavelength of about 8 μm is incident, the incident light passes through the semiconductor substrate 1 and the semiconductor superlattice light absorption layer 5
Reach Here, the incident light excites electrons in the GaAs well subband to the conduction band, and these electrons travel as hot electrons and are detected as an optical signal.

[0005]

Since the conventional semiconductor photodetector is constructed as described above, the semiconductor substrate 1 itself must be polished in the manufacturing process, and the light is incident obliquely. There was a need. For this reason,
Since only the light component perpendicular to the superlattice plane is absorbed, the quantum efficiency is only 0.5 at maximum. Moreover, since only a single element can be formed on the semiconductor substrate 1, there is a problem that integration is difficult.

The present invention has been made in order to solve the above-mentioned problems. It is not necessary to polish the substrate, it is not necessary to allow light to be incident obliquely, the quantum efficiency is improved, and the same substrate is used. Another object of the present invention is to obtain a semiconductor photodetector capable of simultaneously forming a large number of elements and a manufacturing method thereof.

[0007]

According to another aspect of the present invention, there is provided a semiconductor photodetecting device in which a light absorption layer surface is a semiconductor between a semiconductor layer of a first conductivity type and a semiconductor layer of a second conductivity type formed on a semiconductor substrate. The semiconductor superlattice light absorption layer formed perpendicular to the substrate surface is provided.

In the method for manufacturing a semiconductor photodetector according to the present invention, the sidewall of the semiconductor layer is used as a seed to epitaxially grow the sidewall, and the semiconductor superlattice light absorption layer is formed perpendicularly to the semiconductor substrate.

[0009]

In the semiconductor superlattice light absorption layer of the present invention, the superlattice surface is perpendicular to the substrate surface, and all light components incident from the front surface or the back surface of the substrate interact with the semiconductor superlattice light absorption layer.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the semiconductor photodetector of the present invention. In FIG. 1, reference numeral 1 denotes a semiconductor substrate, which is made of GaAs, for example. Reference numeral 2 denotes an insulating film formed on the semiconductor substrate 1, which is, for example, a SiN film. A stripe-shaped first conductivity type semiconductor layer 3 epitaxially grown on the semiconductor substrate 1 is, for example, a p-type GaAs layer.
An insulating film 4 for protecting the element is, for example, a SiN film. 5
Is a semiconductor superlattice light absorption layer that absorbs incident light.
It is formed with 0ÅGaAs / 300ÅAl _0.31 Ga _{0.69 As} 50 cycles. 6 is a semiconductor layer of the second conductivity type, for example, n
Type GaAs layer. Reference numeral 7 denotes a second conductivity type electrode, which is formed of a compound metal such as Au / Ge / Ni. Reference numeral 8 is a first conductivity type electrode formed on the entire back surface of the semiconductor substrate 1 by vapor deposition or the like, and is formed of, for example, Au / Zn. The electromagnetic field vector of light incident through the insulating film 4 on the element surface is all perpendicular to the superlattice plane. Therefore, all the incident light can interact with the semiconductor superlattice light absorption layer 5. Therefore, it is possible to essentially improve the efficiency as compared with the conventional example in which only half of the electromagnetic field vector can interact.

Next, the principle of light detection will be described. The basic structure of the device in the present invention is a so-called PIN photodiode. Light receiving portion, that is, semiconductor superlattice light absorption layer 5, for example, 40ÅGaAs / 30
0ÅAl _0.31 Ga _{0.69 As} GaA in 50 cycles
An s well and an AlGaAs barrier are formed. Each well has a unique subband and extended continuous excited states. When light, for example, infrared rays with a wavelength of about 8 μm is incident on this, the electrons in the sub-band are excited, jump to this continuous excited state, that is, the conduction band, and travel as hot electrons to detect optical signals. To be done.

What is essential in the present invention is that the semiconductor superlattice light absorption layer 5 relating to light absorption is not formed such that the superlattice surface and the substrate surface are parallel to each other as in the conventional example, but is vertical. Is to be formed. For this purpose, the side wall of the epitaxial layer once grown on the substrate is used as a seed for epitaxial growth, and a superlattice plane perpendicular to the substrate is grown from here.

FIG. 2 is a sectional view showing another embodiment of the semiconductor photodetector of the present invention. In this embodiment, the electrode 7 is made of the same electrode material and another electrode 8 is formed on the upper surface. Is.

Hereinafter, a method of manufacturing the semiconductor photodetector of FIG. 1 will be described according to the manufacturing flow shown in FIGS. First, as shown in FIG. 3A, the insulating film 2 is deposited on the semiconductor substrate 1 by, for example, the plasma CVD method. Then, the amorphous silicon layer 1 is formed by, for example, a thermal CVD method.
1 is deposited. Next, as shown in FIG. 3B, the amorphous silicon layer 11 is formed using an appropriate patterning mask.
Holes are formed by dry etching using, for example, CHF ₃ / SF ₆ plasma. Next, for example, the insulating film 2 in the hole portion is removed by buffer hydrofluoric acid to expose the surface of the substrate and form the groove 12 for forming the semiconductor layer of the first conductivity type. Next, as shown in FIG. 3C, a suitable semiconductor epitaxy method, for example, metal organic chemical vapor deposition (MO) is used in the groove 12.
The first conductivity type semiconductor layer 3 is epitaxially grown by using the CVD method. Then, as shown in FIG.
An insulating film 4 for protecting the element is deposited by, for example, a thermal CVD method so as to cover the entire surfaces of the epitaxially grown semiconductor layer 3 of the first conductivity type and the amorphous silicon layer 11. After that, as shown in FIG. 3E, a part of the insulating film 4 for protecting the element on the amorphous silicon layer 11 is removed by etching with, for example, hydrofluoric acid by using an appropriate patterning mask, and the amorphous silicon layer 11 is removed. A hole 13 for removing the is formed.

Then, as shown in FIG.
Through, the amorphous silicon layer 11 is decomposed and removed by, for example, CHF ₃ / SF ₆ plasma etching to form a hole 14 for forming a semiconductor superlattice light absorption layer. here,
The side wall (sidewall 16) of the first conductivity type semiconductor layer 3 that has been epitaxially grown previously is exposed. After that, as shown in FIG. 4B, the semiconductor superlattice light absorption layer 5, for example, 40 Å GaAs / 300 Å Al _0.31 Ga _0.69 , is formed by using, for example, the MOCVD method, the hydride vapor phase epitaxy method (VPE) or the like with the sidewall 16 as a seed. As50 cycles are formed. In addition, the hole 14 is not completely embedded but is partially
That is, the trench 15 for forming the second conductivity type semiconductor layer is left. Next, as shown in FIG. 4C, a semiconductor crystal growth method similar to that described above is used to epitaxially grow the second conductivity type semiconductor layer 6, for example, an n-type GaAs layer doped with Si during growth. Finally, as shown in FIG. 4D, a second conductivity type electrode 7 is vapor-deposited on the second conductivity type semiconductor layer 6, and the first back surface of the semiconductor substrate 1 is covered with a first material.
The conductive type electrode 8 is formed by vapor deposition to complete the semiconductor photodetector according to the present invention.

In the above embodiment, the semiconductor substrate 1 of the first conductivity type is used, and the current flows in the front and back direction of the semiconductor substrate 1. However, a semi-insulating substrate is used and the first conductivity type is used. Alternatively, the second conductivity type electrodes 8 and 7 may be formed on the same surface of the substrate and the light to be detected may be incident from the rear surface of the substrate. This example will be described with reference to FIGS. Figure 5 (a)
As shown in, after filling the hole 14 with the second conductive type semiconductor layer 6, a part of the upper portion of the first conductive type semiconductor layer 3 of the insulating film 4 for protecting the element is removed by etching with hydrofluoric acid or the like, A hole 17 for forming a first conductivity type electrode is formed. Next, FIG.
As shown in (b), the second conductivity type electrode 7 is formed on the second conductivity type semiconductor layer 6, and the first conductivity type electrode 8 is formed on the first conductivity type semiconductor layer 3. By doing so, a semiconductor photodetector according to another embodiment of the present invention is completed.

In the above embodiment, the first conductivity type electrode metal is formed on the entire back surface of the substrate and the detection light is incident from the front surface. However, the electrode is formed only on a part of the back surface. The detection light may be incident from both the front and back sides.

[0018]

As described above, according to the first and second aspects of the present invention, the semiconductor layer of the first conductivity type is partially formed on the semiconductor substrate, and the semiconductor layer of the first conductivity type is formed. Since the semiconductor superlattice light absorption layer is formed by using the side wall of the layer as a growth seed of the semiconductor superlattice light absorption layer, the following effects are achieved.

Since it is not necessary to polish the semiconductor substrate, the manufacturing process is simplified and the device can be manufactured efficiently. Further, since light can be made to enter the substrate perpendicularly, all incident light components are absorbed perpendicularly to the superlattice surface, and therefore improvement in quantum efficiency can be expected. Moreover, since a large number of elements can be formed on the same semiconductor substrate, the area of the opening, that is, the light receiving area is increased, and the device has high sensitivity. Furthermore, since they can be integrated on the same substrate, they can be used as a two-dimensional image pickup device.

[Brief description of drawings]

FIG. 1 is a sectional view showing a semiconductor photodetector according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor photodetector device showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of a semiconductor photodetector device of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process that follows FIG.

FIG. 5 is a cross-sectional view showing a step of another manufacturing method of the present invention.

FIG. 6 is a sectional view showing a conventional semiconductor photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Insulating film 3 First conductive type semiconductor layer 4 Insulating film for element protection 5 Semiconductor superlattice light absorption layer 6 Second conductive type semiconductor layer 7 Second conductive type electrode 8 First conductive type electrode 11 Amorphous Silicon Layer 12 First Conduction Type Semiconductor Layer Forming Groove 13 Amorphous Silicon Layer Removing Hole 14 Semiconductor Superlattice Light Absorbing Layer Forming Hole 15 Second Conduction Type Semiconductor Layer Forming Groove 16 Sidewall 17 Hole for forming first conductivity type electrode

Claims (2)

[Claims] 1. A semiconductor superlattice optical absorption device, wherein a light absorption layer surface is formed perpendicular to the semiconductor substrate surface between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer formed on a semiconductor substrate. A semiconductor photo-detecting device having a layer. 2. A semiconductor layer of a first conductivity type is formed on a semiconductor substrate in a predetermined pattern, and a semiconductor superlattice light absorption layer is perpendicular to the surface of the semiconductor substrate using a sidewall of the semiconductor layer of the first conductivity type as a seed. A method for manufacturing a semiconductor photodetector, comprising the step of forming.