JPH07106621A - Semiconductor light receiving element - Google Patents

Abstract

PURPOSE:To obtain a semiconductor light receiving element exhibiting excellent absorption characteristics for a specific laser light, while realizing monolithic structure with an electronic device easily, by laminating an InGaAs quantum well layer having compressive strain and a GaAsP or InGaP barrier layer having tensile strain alternately to form a light absorption layer. CONSTITUTION:A buffer layer 2, a strained quantum well light absorption layer 3, and a window layer 4 are laminated on an n-GaAs substrate 1. The strained quantum well light absorption layer comprises an alternate laminate of 100 layers of In0.28Ga0.72As well layer 3a and GaAs0.44P0.5 barrier layer 3b. The In0.28Ga0.72As well layer 3a is epitaxially grown on the GaAs substrate as a crystal having grating constant higher than that of GaAs. The well layer 3a is applied with compressive strain of 0.2% thus setting the center of absorption band of light receiving element at 1mum or thereabout. On the other hand, the GaAs0.44P0.5 barrier layer 3b is grown epitaxially on the GaAs substrate as a crystal having grating constant lower than that of GaAs and applied with tensile strain of 0.2%.

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 a laser for optical communication having a wavelength near 1 μm.

[0002]

2. Description of the Related Art In short-distance optical communication such as in-plant LAN and indoor communication, there is little trouble in use even if the transmission efficiency is lowered, and therefore, characteristics such as threshold value and power consumption are excellent.
In many cases, a short wavelength band laser in the vicinity of μm is used.

As the light receiving element in this frequency band, generally, a cheap Si type light receiving element is often used, but the central wavelength of the Si light absorption band is around 0.7 μm, and the laser light in the vicinity of 1 μm is used. The light receiving sensitivity to is not always sufficient. Further, since it is difficult to fabricate the Si-based light receiving element on the GaAs substrate, there is a drawback that it is not possible to fabricate the OEIC by making it monolithic with the electronic device formed on the GaAs substrate.

On the other hand, in the InGaAs / GaAsP-based or InGaAs / InGaP-based quantum well photodetector, the center wavelength of the optical absorption band is about 1 μm by applying a compressive strain of about 0.2% to InGaAs which is a well layer. In addition to the above, it is possible to make it monolithic with an electronic device formed on a GaAs substrate, and its application to a receiving element of a wavelength band laser near 1 μm is under study.

[0005]

However, in order to make the light absorption intensity of the quantum well light receiving element sufficient, it is necessary that the thickness of the light absorption layer is at least about 1 μm. When the added crystals of InGaAs or the like are laminated, crystal defects and crystal destruction occur due to the accumulation of stress, so that it is not possible to obtain a film thickness that can achieve a sufficient light absorption intensity.

For example, when an InGaAs well layer having a thickness of 6 nm having a compressive strain of 0.2% and a GaAsP barrier layer having a thickness of 6 nm having no strain are alternately grown on a GaAs substrate, a well layer is formed. When 3 to 5 barrier layers are laminated, TE
Large crystal defects that can be confirmed by M occur, and further crystal growth is impossible. Therefore, in the conventional studies, the upper limit of the film thickness of the strained quantum well light absorption layer is 100 nm, and a sufficient light absorption intensity cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is excellent in the light receiving sensitivity for a laser beam in the vicinity of 1 .mu.m formed on a GaAs substrate and has a sufficiently high absorption intensity. In the device, the light absorption layer is an InGaAs quantum well layer having a compressive strain, a GaAsP barrier layer having a tensile strain, or an InG having a tensile strain.
A semiconductor light receiving element characterized by being formed by a repeating structure with an aP barrier layer.

In the present invention, the compressive strain is applied to the well layer so that the center of the absorption band of the light receiving element is in the vicinity of 1 μm. For example, if an In _0.20 Ga _0.80 As well layer having a film thickness of 6 nm is used, The center is 0.95 μm, and the film thickness is 6
If the In _0.28 Ga _0.72 As well layer of nm is used, the absorption band center can be set to 0.98 μm.

The purpose of applying tensile strain to the barrier layer is to alleviate the accumulation of strain stress due to the increase in the number of well layer layers, and thereby to prevent crystal defects and crystal destruction. The thickness of the light absorption layer can be increased, and the light absorption intensity can be increased.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view showing a structure of a light receiving element according to the present invention, and FIG. 2 is an enlarged sectional view showing a structure of a strained quantum well light absorption layer which is a feature of the present invention. In FIG. 1, the portion excluding the strained quantum well light absorption layer 3 has the same structure as a known PIN light receiving element.

That is, 1 is an n-GaAs substrate, 2 is an n-InGaP buffer layer having a thickness of 1 μm, 4 is an n-InGaP window layer having a thickness of 0.5 μm, and 5
Is a SiNx insulating film (x is a natural number), 8 is SiNx
A p ⁺ diffusion layer having a thickness of 0.8 μm and formed by diffusing Zn using the film 5 as a mask, and 6 and 7 are p
A side electrode and an n-side electrode, and 9 is a SiNx antireflection film.

Further, in FIG. 2, 3a is In having a thickness of 6 nm.
_0.28 Ga _0.72 As well layer 3b is 6 nm thick G
This is an aAs _0.44 P _0.56 barrier layer, in which 100 well layers 3a and 3 barrier layers are alternately laminated, and the total thickness of the strained quantum well light absorption layer 3 is 1.2 μm.

Here, In _0.28 G forming the well layer 3a
a _0.72 As is a crystal having a larger lattice constant than GaAs, and by epitaxially growing it on a GaAs substrate, a compressive strain of 0.2% is applied to the well layer 3a, while forming a barrier layer 3b. GaAs _0.44 P _0.56 is a crystal having a smaller lattice constant than GaAs.
Due to the epitaxial growth on the substrate, a tensile strain of 0.2% is applied to the barrier layer 3b.

In this way, the compressive strain is applied to the well layer as follows.
This is because the absorption band center of the light receiving element is set to be near 1 μm,
In this example, the center of the absorption band was 0.98 μm. Further, when a cross-section was observed by TEM, it was confirmed that the quantum well light absorption layer 3 did not have crystal defects or crystal destruction. This is because, unlike the conventional strained quantum well photo detector in which compressive strain is applied only to the well layer, strains in opposite directions are applied to the well layer and the barrier layer, so that stress due to strain is mutually relaxed. It is a thing.

Although the GaAsP type crystal is used as the barrier layer in the above-mentioned embodiment, the same effect can be obtained by using the tensile strained InGaP type crystal. Although the PIN light receiving element has been described in the above embodiments, the present invention can be similarly applied to other types of light receiving elements such as an avalanche photodiode (APD). Further, the gist of the present invention is to mutually relax strain stress by applying strains in opposite directions to the well layer and the barrier layer, respectively. The film thickness of the well layer and the barrier layer, the degree of strain, or Numerical values such as the number of repetitions that should be appropriately changed according to the wavelength and intensity of the laser light are not limited to those described in the above embodiment.

[0016]

As is apparent from the above description, in the light receiving element according to the present invention, the light absorbing layer is made of InGaA having a compressive strain.
Since it is formed by a repeating structure of an s quantum well layer and a tensile strained GaAsP barrier layer or a tensile strained InGaP barrier layer, it has excellent absorption characteristics for laser light in the vicinity of 1 μm, and Since it is formed on a GaAs substrate, it has an advantage that it can be easily monolithic with an electronic device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a light receiving element according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a structure of a photonic quantum well light absorption layer which is a feature of the present invention.

[Explanation of symbols]

1 is an n-GaAs substrate 2 is an n-InGaP buffer layer 3 is a strained quantum well light absorption layer 3a is an InGaAs well layer 3b is a GaAsP barrier layer 4 is an n-InGaP window layer 5 is a SiNx insulating film 6 is a p-side electrode 7 n-side electrode 8 is p ⁺ diffusion layer 9 is SiNx antireflection film

Claims (1)

[Claims] 1. A light-receiving element having a light absorption layer provided on a GaAs substrate, wherein the light absorption layer has a compressive strain of InGaA.
A semiconductor light-receiving element characterized by being formed by a repeating structure of an s quantum well layer and a tensile strained GaAsP barrier layer or a tensile strained InGaP barrier layer.