JPH05152599A - Light receiving semiconductor element - Google Patents

Abstract

PURPOSE:To prevent unstable condition of laser emission by reducing reflecting retrogressive light from the receiving side in optical communication. CONSTITUTION:A region of p<+>-InP 5 is formed as a light-receiving region on an epitaxial wafer which consists of a substrate 1 of n<+>-InP, a buffering layer 2 of n-InP, a light absorbing layer 3 of n<->-InPGaAs, and a window layer 4 on n-InP. Then, an inclined light-receiving region 5 is formed by etching the surface of the light-receiving region obliquely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element used for optical communication.

[0002]

2. Description of the Related Art A compound semiconductor photodetector has been put to practical use as a high-sensitivity, long-wavelength photodetector for optical communication. Above all, a wavelength of 1.3 μm or 1.55 using InGaAs is used.
A semiconductor light receiving element for μm is widely used for large capacity long distance optical communication.

FIG. 5 shows a conventional example of a pin photodiode using this InGaAs. On the n ⁺ -InP substrate 1, the carrier concentration is 1E15 to 2E16 cm ^-3 , and the layer thickness is 1 to 1.
3 μm n-InP buffer layer 2, carrier concentration 1E14-
1E16 cm ^-3 , n ⁻ -InGaAs having a layer thickness of 1 to 5 μm
Light absorption layer 3, carrier concentration 1E15 to 3E16 cm ^-3 ,
On an epitaxial wafer in which an n-InP window layer 4 having a layer thickness of 0.5 to 2 μm was sequentially grown by a vapor phase growth method, p ⁺ -I having a carrier concentration of 1E17 to 1E20 cm ^-3 was used as a light receiving portion.
After selectively forming the nP region 5 by the sealing diffusion of Zn, an antireflection film / insulating film 8 serving as an antireflection film is formed on the surface of the n-InP window layer 4.
As a result, an oxide film or a nitride film is grown. After that, the insulating film 8 is selectively perforated to form the p-side electrode 6, and further the n-side electrode 7 is formed on the back surface of the substrate.

The pin photodiode using InGaAs thus produced is mainly used as a receiver in optical fiber communication. A semiconductor laser (hereinafter referred to as LD) is used on the transmitting side in an optical communication system. The signal light emitted from the LD is condensed by the lens and guided to the optical fiber. On the light receiving side, the light propagating in the optical fiber is condensed by the lens on the light receiving portion and photoelectrically converted inside the light receiving element (in the light absorption layer).

Here, there is a phenomenon that the light emitted from the LD is partially reflected by the end of the optical fiber, the surface of the lens, and the surface of the light receiving element, and returns to the LD side through the optical fiber again. When this reflected return light returns to the inside of the LD, the light emitting state of the LD becomes unstable, so this reflected return light must be suppressed as much as possible. Therefore, as a measure against reflected return light on the light receiving element side, the fiber end is obliquely cut in the range of 5 ° to 15 °, or an antireflection film is provided on the surface of the lens or the light receiving element.

[0006]

In the above-mentioned conventional light receiving element, when mounted on the stem, the light receiving element sometimes tilts and is fixed, and the direction of the tilt is not constant. Therefore, the optical fiber coupled to the light receiving element is not fixed. It may not match the diagonal cutting direction of. That is, when the inclined surface of the light receiving element and the cut surface of the optical fiber have a “C” shape when viewed from the side, the reflected light on the surface of the light receiving element is returned to the inside of the optical fiber. In the conventional light receiving element described above, the inclination of the light receiving element with respect to the stem is not uniquely determined, so that the above inconvenience cannot be avoided.

[0007]

The semiconductor light receiving element of the present invention is characterized in that the light incident surface of the light receiving region is inclined in the range of 5 ° to 15 °.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the manufacturing process of the first embodiment of the present invention. An n ⁺ -InP substrate 1 having a carrier concentration of 1E15 cm ⁻³ and a layer thickness of 2 μm was formed by vapor phase epitaxy.
-InP buffer layer 2, carrier concentration 1E15 cm ^-3 , n ^-- InGaAs light absorption layer 3 having a layer thickness of 1.4 µm-After growing an InGaAs light absorption layer 3, carrier concentration 1E16 cm ^-3 , layer thickness of 1 µm n-
The InP window layer 4 is grown [(a) of FIG. 1].

A diffusion mask is formed on the above epitaxial wafer by the CVD method, a hole of 50 μmφ is formed in the light receiving portion, and then a p ⁺ -InP region 5 having a carrier concentration of 1E17 to 1E20 cm ^-3 is formed by sealing diffusion of Zn, for example. It is selectively formed [(b) of FIG. 1]. After the p ⁺ -InP region 5 is formed, a photoresist mask 10 is formed as an etching mask so as to surround the light receiving region, and the ion beam 11 is irradiated from a 6 ° oblique direction to perform etching [(c) of FIG. 1]. An inclined light receiving region 9 which is partially inclined by 6 ° is formed on the surface of the window layer 4 [(d) of FIG. 1].

After removing the photoresist mask 10, an antireflection film / insulating film 8 is grown on the surface side by a usual method.
A window is formed in this insulating film, and then the p-side electrode 6 is formed. Next, the back surface of the n ⁺ -InP substrate 1 has a total thickness of 1
Polished to 0 to 200 μm, Sn-A on the surface
u is vapor-deposited and alloyed to form the n-side electrode 7.

FIG. 2 shows a sectional view of a pin photodiode manufactured by the above method, and FIG. 3 shows the relationship between the inclination of the light receiving portion and the cutting direction of the optical fiber in the light receiving element module in which the photodiode is mounted. As shown in FIG. 3, if both are fixed to the stem so that the cut direction of the optical fiber and the direction of the inclined light receiving region 9 are aligned, it is possible to prevent the surface reflection from the light receiving element from returning to the optical fiber again. . Even if the photodiode is tilted and mounted on the stem in this case, the tilted light-receiving surface and the cut surface of the optical fiber are “Ha” because the tilted light-receiving surface is only horizontal to the stem plane. The “-” shape is prevented, and the light reflected from the photodiode surface does not re-enter the optical fiber.

FIG. 4 is a sectional view showing a second embodiment of the present invention. This embodiment relates to a back illuminated pin photodiode. The photodiode of this embodiment is manufactured as follows. The process up to the step shown in FIG. 1B is the same as in the case of the first embodiment. After forming the epitaxial wafer in this way, the p-side electrode 6 is formed on the substrate surface.
To form.

Next, the back surface of the substrate has a total thickness of 100 to 1
After mirror polishing to 50 μm, a photoresist mask is formed so as to surround the light receiving region, and ion beam etching is performed from an oblique 6 ° direction to selectively form a tilted light receiving region 9 on the back surface. After that, the antireflection film 8 is formed on the inclined region of the back surface, and the n-side electrode 7 is formed on the other portions. Also in the present embodiment, in the light receiving element module,
By aligning the inclined surface of the light receiving element with the inclined direction of the optical fiber, reflected return light can be prevented as in the previous embodiment.

The preferred embodiment has been described above.
The present invention is not limited to these examples, and can be applied not only to pin photodiodes but also to APDs, and also to photodiodes using materials other than InAsP / InP-based materials. In addition to vapor phase epitaxy, liquid phase epitaxy, MOCVD, MBE is used as a means for forming an epitaxial wafer.
Method, ALE method, etc. can be adopted. Also, the inclination angle of the light receiving region can be arbitrarily set within the range of about 5 ° to 15 °.

In the light receiving element of the present invention, the mount surface on the support and the light incident surface may be the same surface. In that case, the semiconductor surface of the light receiving region is inclined with respect to the portion where the mounting electrode is formed.

[0016]

As described above, since the light receiving element of the present invention has the surface of the light receiving region inclined with respect to the mount surface, the present invention allows the optical fiber of the optical fiber with respect to the inclination of the light receiving region. The cut surface can be uniquely determined. As a result, reflected return light from the surface of the light receiving element to the LD can be prevented, and instability of oscillation on the LD side in optical fiber communication can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the first embodiment of the present invention.

FIG. 3 shows a first aspect of the present invention in a light-receiving element module.
FIG. 6 is a cross-sectional view showing the relationship between the embodiment of FIG.

FIG. 4 is a sectional view showing a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

1 n ⁺ -InP substrate 2 n-InP buffer layer 3 n ^-- InGaAs light absorption layer 4 n-InP window layer 5 p ⁺ -InP region 6 p-side electrode 7 n-side electrode 8 Antireflection film / insulating film 9 Gradient light reception Area 10 Photoresist mask 11 Ion beam 12 Optical fiber

Claims (1)

[Claims] 1. A semiconductor light receiving element having a mount surface mounted on a support and a light incident surface on which light is incident, wherein the light incident surface is inclined with respect to the mount surface. Semiconductor light receiving element.