KR100860187B1 - Semiconductor optical device having a double heterostructure to reduce leakage current and method of manufacturing the same - Google Patents

Abstract

According to the present invention, a substrate, a lower photoresist layer and an upper photoresist layer provided on the substrate, a multi-quantum well interposed between the lower photoresist layer and the upper photoresist layer, and formed on the upper photoresist layer A double heterostructure (DH) comprising an InP cladding layer having a thickness of 200 to 250 nm and having a mesa form; A first current blocking layer and a second current blocking layer sequentially stacked on the periphery of the double hetero structure and pn-bonded to each other; And an upper clad layer formed on the mesa of the double hetero structure and the second current blocking layer.

Leakage current, DH, BH, mesa, current blocking layer, pn junction

Description

Semiconductor optical device with double heterostructure to reduce leakage current and manufacturing method thereof

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a block diagram showing a double heterostructure of a general semiconductor optical device.

FIG. 2 is a partially enlarged view showing a buried heterostructure having the double heterostructure of FIG. 1. FIG.

3 and 4 are photographs showing a heterostructure in which an abnormal crystal film is provided according to the prior art.

5 is a photograph showing a FS-embedded heterostructure provided according to the prior art.

6 is a block diagram illustrating a buried heterostructure of a semiconductor optical device provided according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a structure of reducing the thickness of the InP clad layer in FIG. 6.

8 is a photograph showing a structure of a semiconductor optical device having an InP clad layer thickness of 200 nm of a buried hetero structure.

9 is a photograph showing a structure of a semiconductor optical device having an InP clad layer thickness of 150 nm of a buried hetero structure.

<Description of main reference numerals in the drawings>

100 ... InP substrate 101 ... active layer

102,102 '... InP cladding layer 103 ... First current blocking layer

104 second secondary barrier layer 105 upper cladding layer

The present invention relates to a semiconductor optical device and a method of manufacturing the same, and more particularly, to a semiconductor optical device having a double heterostructure (DH) that can reduce the leakage of current through the current blocking layer around the active layer. And to a method for producing the same.

In general, a semiconductor diode (hereinafter, referred to as a 'semiconductor optical device'), such as a light emitting diode (LED) or a laser diode (LD), is disposed on the n-InP substrate 10, as shown in FIG. 1, and the InP buffer layer 11. , The active layer 13 of the multi-quantum well structure, the p-InP clad layer 15, the etching InGaAs layer 16, and the InP protective layer 17, which are positioned between the light confinement layers 12 and 14, are sequentially formed. Stacked double heterostructures.

Here, the active layer 13 has a multi-quantum well structure in which quantum wells 13a and barrier layers 13b are alternately provided.

After the epitaxial growth, the double heterostructure wafer is subjected to a regrowth process after a mesa etching process to achieve a planar BH structure having excellent threshold current efficiency. Accordingly, the p-InP current blocking layer and the n-InP current blocking layer are sequentially stacked around the active layer 13 to block leakage of the injection current. In particular, the p-InP current blocking layer is formed on the upper surface of the mesa of the double heterostructure. It is formed to be connected to the grown p-InP cladding layer 15.

As shown in FIG. 2, the semiconductor optical device primarily grows a p-InP cladding layer 15 on the light confinement layer 14, and thereafter, a Si ₃ N ₄ (or SiO ₂ ) mask layer and an InGaAs for etching. The layer 16 is grown to perform mesa etching on the multi-quantum well 13, and the second p-InP current blocking layer 18 and the n-InP current blocking layer 19 around the multi-quantum well 13. In order to remove the Si ₃ N ₄ (or SiO ₂ ) mask layer and the InGaAs layer 16 for etching, and then the p-InP upper clad layer 20 is sequentially replaced with the p-InP layer 15. And buried heterostructure (BH) by growing on the n-InP current blocking layer 19.

In the semiconductor optical device, the leakage current generated by the shape or thickness of the buried heterostructure has a decisive influence on the threshold current and lifetime of the semiconductor optical device. In order to solve this problem, researches on a method of changing the buried heterostructure, such as designing a deeper mesa structure, have been actively conducted.

In the case of the mesa structure, if the etching depth is not sufficient in the MOCVD regrowth process performed after the etching process, an abnormal crystal film structure may be formed as shown in FIGS. 3 and 4.

In this regard, Mitsubishi Japan, shown in FIG. 5, has released a 1.3 μm DFB LD product having an FS-BH structure having a relatively deep mesa etching depth and a very high DH top layer. As described above, when the mesa etching depth is deeply formed, a change in the film characteristics due to the change of the under cut ratio of the mesa etching mask having a predetermined length should be considered.

On the other hand, BH manufacturing method for forming mesa in the vertical form by performing the mesa etching process by dry etching rather than wet etching has also been published, this method is reported to be difficult to commercialize due to leakage current problem.

The present invention has been made in view of the above, and an object of the present invention is to provide a semiconductor optical device having an optimized thickness of an InP clad layer having a double hetero structure and a method of manufacturing the same, so as to reduce leakage current.

In order to achieve the above object, a semiconductor optical device according to the present invention includes a substrate, a lower photonic confinement layer and an upper photoconductive layer provided on the substrate, and a multi-quantum interposed between the lower photoconductive layer and the upper photoconductive layer. A double heterostructure (DH) including a well and an InP cladding layer having a thickness of 200 to 250 nm formed on the upper photoresist layer, and having a mesa shape; A first current blocking layer and a second current blocking layer sequentially stacked on the periphery of the double hetero structure and pn-bonded to each other; And an upper clad layer formed on the mesa of the double hetero structure and the second current blocking layer.

Preferably, the substrate may be formed of n-InP, the first current blocking layer is p-InP, the second current blocking layer is n-InP, and the upper clad layer is formed of p-InP.

According to another aspect of the invention, the step of sequentially growing a buffer layer, a lower photoresist layer, an active layer, an upper photoresist layer and an InP clad layer on the substrate to form a double heterostructure (DH); Etching the double heterostructure in a mesa pattern; Sequentially growing a first current blocking layer and a second current blocking layer around the mesa to be pn-bonded to each other; Forming a cladding layer on the mesa of the double heterostructure and the second current blocking layer; And forming an ohmic contact layer on the cladding layer, wherein in the forming a double heterostructure, the InP cladding layer is formed so that a portion of the first current blocking layer may cover the InP cladding layer having a double heterostructure. There is provided a method for manufacturing a semiconductor optical device, characterized by growing to a thickness of 200 ~ 250nm.

Preferably, the substrate is grown by n-InP, the first current blocking layer by p-InP, the second current blocking layer by n-InP, and the upper cladding layer by p-InP.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly introduce the concept of terms in order to best explain their invention. It should be interpreted as meanings and concepts in accordance with the technical spirit of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

6 shows a buried heterostructure of a semiconductor optical device provided in accordance with the present invention.

Referring to FIG. 6, a semiconductor optical device according to the present invention includes a double heterostructure (DH) etched to form a mesa, and a first current blocking layer 103 and a second current sequentially stacked around the double heterostructure. The blocking layer 104, the upper cladding layer 105 and the ohmic contact layer 106 formed on the double hetero structure mesa and the second current blocking layer 104.

The double heterostructure has a thickness formed on the active layer 101 and the active layer 101, the active layer 101 having a structure grown on the substrate 100 and interposed between the lower photoresist layer and the upper photoresist layer with a multi-quantum well. An InP cladding layer 102 of 200-250 nm is included.

Around the mesa of the double heterostructure, the first current blocking layer 103 and the second current blocking layer 104 are sequentially stacked while forming a pn junction to block leakage of the injection current. Here, when the InP substrate 100 is made of an n-type semiconductor, the first current blocking layer 103 is grown by p-InP, and the second current blocking layer 104 is grown by n-InP. In contrast, when the InP substrate 100 is made of a p-type semiconductor, the first current blocking layer 103 is grown by n-InP, and the second current blocking layer 104 is grown by p-InP. .

In the double heterostructure, changing the thickness of the InP cladding layer 102 causes the vertical position and layer shape of the active layer 101, the first current blocking layer 103, the second current blocking layer 104, and the like to be changed. . Accordingly, the InP cladding layer 102 shown in FIG. 6 has a larger thickness than the InP cladding layer 102 'shown in FIG. However, excessive increase in thickness of the InP cladding layer 102 may deteriorate electrical characteristics such as resistance or carrier confinement characteristics. In this regard, the InP cladding layer 102 may be 200-250. It is grown to have a thickness of nm.

FIG. 8 is a photograph showing the structure of a semiconductor optical device having a thickness of 200 nm of an InP clad layer 102 having a buried hetero structure. Referring to the drawings, a part of the first current blocking layer 103 covers the InP cladding layer 102 sufficiently to correspond to the 200 nm thick InP cladding layer 102, so that the current blocking function can be performed without a problem. It can be seen.

On the other hand, in the semiconductor optical device shown in FIG. 9, the thickness of the InP cladding layer 102 ′ is 150 nm, and a part of the first current blocking layer 103 does not cover the vicinity of the active layer 101 so that the current blocking characteristic is poor. The result is bad.

The upper clad layer 105 is grown to be pn-bonded on the mesa top surface of the double heterostructure and the second current blocking layer 104, and an ohmic contact layer 106 is formed thereon. Here, when the second current blocking layer 104 is grown by n-InP, the upper cladding layer 105 in contact with it is grown by p-InP.

According to the buried heterostructure as described above, the current injected into the upper cladding layer 105 via the ohmic contact layer 106 is the thickness of the double heterostructured InP cladding layer 102 and the first current blocking corresponding thereto. The leakage amount is reduced by the current blocking action due to the arrangement structure of the layer 103 or the like.

Hereinafter, a process of performing a semiconductor optical device manufacturing method according to an exemplary embodiment of the present invention will be described.

First, a first growth process of forming a semiconductor thin film having a double heterostructure having the active layer 103 is performed. The double heterostructure has a structure in which an InP buffer layer, an InGaAsP lower light confinement layer, a multi-quantum well, an InGaAsP upper light confinement layer, and an InP clad layer are sequentially stacked on the InP substrate.

In the double heterostructure, the InP cladding layer is grown to a thickness of 200 to 250 nm so that a part of the first current blocking layer may cover the InP cladding layer of the double heterostructure after completion of the secondary growth process.

After the double heterostructure is formed, a mask layer is deposited on the InP clad layer, a mesa pattern is formed on the double heterostructure by a photolithography process, and a wet etching process is then performed. In this case, Si ₃ N ₄ or SiO ₂ may be used as the mask layer.

After the mesa is formed in the double heterostructure, a secondary growth process of sequentially stacking the first current blocking layer and the second current blocking layer around the mesa to be pn-bonded to each other is performed.

Subsequently, when a third growth process of sequentially stacking an InP upper clad layer and an ohmic contact layer is formed on the upper surface of the mesa and the second current blocking layer, a semiconductor optical device having the above-described structure is manufactured.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

According to the present invention, the thickness of the InP cladding layer of the double heterostructure is 200 to 250 nm, so that the first current blocking layer can sufficiently cover the InP cladding layer, thereby improving the current blocking performance and reducing the leakage current.

Claims (4)

A substrate, a lower photonic confinement layer and an upper photoconductive layer provided on the substrate, multiple quantum wells interposed between the lower photoconductive layer and the upper photoconstraining layer, and a thickness of 200 to 250 nm formed on the upper photoconstraining layer. A double heterostructure (DH) comprising an InP cladding layer and formed in mesa form; A first current blocking layer and a second current blocking layer sequentially stacked on the periphery of the double hetero structure and pn-bonded to each other; And And an upper clad layer formed on the mesa of the double hetero structure and the second current blocking layer. The method of claim 1, And the substrate is n-InP, the first current blocking layer is p-InP, the second current blocking layer is n-InP, and the upper clad layer is grown by p-InP. Sequentially growing a buffer layer, a lower photoresist layer, an active layer, an upper photoresist layer, and an InP clad layer on the substrate to form a double heterostructure (DH); Etching the double heterostructure in a mesa pattern; Sequentially growing a first current blocking layer and a second current blocking layer around the mesa to be pn-bonded to each other; Forming an upper clad layer on the mesa of the double heterostructure and the second current blocking layer; And And forming an ohmic contact layer on the upper clad layer. In the step of forming the double heterostructure, the semiconductor optical device fabrication, characterized in that to grow the InP clad layer to a thickness of 200 ~ 250nm so that a portion of the first current blocking layer can cover the InP clad layer of the double hetero structure Way. The method of claim 3, Wherein the substrate is grown by n-InP, the first current blocking layer is p-InP, the second current blocking layer is n-InP, and the upper clad layer is grown by p-InP. .

Images