JP3046161B2 - Semiconductor device including undoped layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having an undoped layer and a current blocking layer, wherein the current blocking layer is formed by metal organic chemical vapor deposition.

[0002]

2. Description of the Related Art Conventionally, various element structures have been formed by using structures obtained by laminating semiconductor materials by crystal growth. For example, in the case of a semiconductor laser and a light emitting diode, in order to improve the conversion efficiency from current to light,
An element structure having a current blocking layer is formed. As a conventional method of forming a current blocking layer, for example, there is a method disclosed in the literature: “Oki R & D, No. 138, Vol. 55, No. 2, pp. 15-20”. According to the disclosed method, the current blocking layer of the light emitting diode is formed by using a liquid crystal growth method (hereinafter sometimes abbreviated as “LPE”). It has a junction, ie, a PN junction and an NP junction. When the device driving current is injected into the current blocking layer,
Since a reverse bias is applied to the NP junction, the drive current is blocked.

Further, when an active region (light emitting layer) is provided in a minute region surrounded by a current blocking layer, a drive current is limited only to the active region, so that high current-light conversion efficiency can be achieved.

Hereinafter, the LP described in the above-mentioned document will be described with reference to the drawings.
A method for forming a light emitting diode having a current blocking layer using E will be described. (A) and (B) of FIG.
FIG. 2 is a cross-sectional view showing a main stage of a light emitting diode forming process.

[0005] First, a current blocking layer 26 is formed on a P-InP substrate 10 (doped Zn concentration 5 × 10 ¹⁸ cm ^-3 ).
This current blocking layer is composed of a P-InP buffer layer (doped Zn).
7 × 10 ¹⁷ cm ⁻³ ) 12, N-InP block layer (doped Sn concentration 4 × 10 ¹⁷ cm ⁻³ ) 14 and PI
nP layer block (doped Zn concentration: 4 × 10 ¹⁷ cm ⁻³ ) 1
6, and these layers are sequentially grown using LPE (FIG. 2A).

Next, a V-groove 18 is selectively formed on the laminated body on which the current blocking layer 26 has been grown, using a hydrochloric acid-based etchant. Then, a P-InP cladding layer (doped Zn 6 × 10 ¹⁷ cm ⁻³ ) 20, a P-InGaAsP active layer 22, an N-InP cladding layer (Sn-doped) 24,
The main structure of the light emitting diode having the current blocking layer is formed by sequentially growing the N-InGaAsP cap layer 28 (FIG. 2B). The P-InGaAs active layer 22 has the crescent shape shown in the figure due to the plane orientation dependence. In the drawings, illustration of upper and lower electrodes is omitted.

When crystal growth is performed using LPE, there are problems in the reproducibility of the thickness and composition of the thin film layer and the in-plane uniformity of the thickness and composition of the growth layer.

However, when MO-CVD (metal organic chemical vapor deposition) is used for crystal growth, the growth of a thin film can be controlled with a thickness on the order of molecules, and the thickness, composition, and carrier of the grown layer can be controlled. Excellent in uniformity such as concentration.

Therefore, when the crystal is grown by using the MO-CVD method, the device characteristics can be made more uniform, and the device characteristics can be made more uniform with a higher yield than when LPE is used.

[0010]

However, for example, zinc (Zn) is used as a dopant for a P-type III-V compound semiconductor. However, when a growth layer is grown by MO-CVD on a layer having a high carrier concentration, unactivated Zn diffuses into this layer or another layer already formed. For example, when an N-type layer is grown by MO-CVD on a P-type III-V compound semiconductor substrate doped with Zn, an N-type layer in which Zn in the substrate is growing during the growth of this layer. Will spread to. As a result, in the diffusion region of Zn in the N-type layer, it is inverted from N-type to P-type.

Therefore, an object of the present invention is to provide a method of growing a second conductive type layer on a first conductive type III-V compound semiconductor substrate doped with a first conductive type impurity by MO-CVD. It is an object of the present invention to provide a semiconductor device which is formed while preventing diffusion of a first conductivity type impurity into a conductivity type layer, and has an improved current blocking performance.

[0012]

A semiconductor device according to the present invention includes an undoped layer on the upper surface side of the first conductivity type substrate, a current blocking layer on the upper surface side of the undoped layer, and the current blocking layer is A first layer of the first conductivity type layer, a second conductivity type layer formed on the upper surface side of the first layer of the first conductivity type layer,
A second conductive type layer is provided on the upper surface side of the second conductive type layer, and the current blocking layer is formed by metal organic chemical vapor deposition.

[0013]

According to the structure of the present invention described above, it is not necessary to introduce a dopant gas when growing an undoped layer, so that the undoped layer is an N-type layer having a low carrier concentration. When Zn diffuses from the P-type layer into the undoped layer, the undoped layer changes from N-type to P-type. Therefore, since the undoped layer captures Zn diffused from the P-type layer by the undoped layer and acts as a kind of buffer region, it is possible to prevent Zn from diffusing into the N-type layer.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of a method for forming a thin film laminate using an organic vapor deposition method according to the present invention will be described below. It should be noted that the figures referred to below merely schematically show the size, shape and arrangement of each component so that the present invention can be understood. Therefore, it is clear that the present invention is not limited to the illustrated example.

FIGS. 1A to 1C are process diagrams for explaining an embodiment of the present invention. Each figure is a diagram schematically showing a state of a structure obtained in a main process step in a cross section.
In the drawing, hatching indicating a cross section is partially omitted.

In this embodiment, an undoped layer (not doped with impurities) 32 is formed on a P-type substrate 30 as a first conductivity type layer which is a group III-V compound semiconductor doped with zinc (Zn). The P-N-P current blocking layer 36 including the N-type layer 34 as the second conductivity type layer is formed on the undoped layer 32 by MO growth.
-An example of growing using a CVD method will be described.

First, a P-InP substrate (doped Zn concentration: 5 × 10 ¹⁸ cm ⁻³ ) 30 shown in FIG. 1A is set in a growth chamber, and an undoped layer 32 is formed on the substrate 30 under the following conditions. Is grown to a thickness of 0.2 μm (FIG. 1B).

The growth conditions in this embodiment are as follows. Group III materials are trimethylindium (TM
I) is used after bubbling with hydrogen. Also, phosphine (PH ₃ ) is used as the group V material. Decompress the growth chamber,
The substrate 30 is heated to an appropriate temperature in the range of 550 to 650C. Subsequently, the above-described gas is introduced into a growth chamber under reduced pressure, and an InP layer is grown on the substrate. Also, 50 molar ratio of TMI and PH ₃ to be introduced into the growth chamber (VIII ratio)
A preferred value in the range of 200 is preferred. When growing an undoped layer, no dopant gas is introduced.

Next, on the undoped layer 32, a 0.7 μm-thick P-InP layer (doped Zn concentration: 5 × 10 ¹⁷ cm ⁻³ ) 38, which is the first layer of the first conductivity type layer, 0.5 μm-thick N—InP layer (doped tin concentration: 7 × 1)
0 ¹⁷ cm ⁻³ ) 34 and a 1.5 μm-thick P-InP layer (doped Zn concentration 2 × 10 ¹⁷ ) which is the second layer of the first conductivity type layer
cm ⁻³ ) 40 are sequentially grown under the growth conditions described below to form the current blocking layer 36 (FIG. 1C).

The conditions for forming the current blocking layer 36, the first layer 38 of the first conductivity type, the second layer 34, and the second layer 40 of the first conductivity type are such that an undoped layer is grown. Dimethyl zinc (DMZn) as a P-type dopant gas and silane (SH ₄ ) as an N-type dopant gas under the same InP growth conditions as those used in the above. The carrier concentration in the growth layer is controlled by controlling the flow rate of the dopant gas. The flow rate and pressure of the dopant gas are controlled using a mass flora controller and a pressure controller, respectively.

The diffusion of Zn from the first layer 38 of the first conductivity type layer and the second layer 40 of the first conductivity type layer into the N-type layer in the current blocking layer 36 Since the concentration of Zn is low, there is no practical problem.

If the same V-groove as in the conventional example is formed in the laminate on which the above-described current blocking layer is formed, and the cladding layer and the light emitting layer, and if necessary, the cap layer are formed, the same as in the conventional example is obtained. Light emitting diodes can be obtained.

In the embodiment described above, in the present invention,
Although an example in which a specific material is used and formed under specific conditions has been described, other materials may be used. Further, the thickness of the undoped layer is not limited to 0.2 μm.

[0024]

According to the structure of the semiconductor device of the present invention,
An undoped layer is provided on the first conductivity type substrate. The undoped layer has two types of junctions, ie, a PN junction and an NP junction, and has a current blocking layer formed by metal organic chemical vapor deposition. Therefore, the N-type layer serving as the second conductivity type layer does not contain impurities diffused from the substrate, that is, zinc. For this reason, the semiconductor device of the present invention
Since it is formed without losing the conductivity type layer and by growing the carrier concentration with good reproducibility, it has high current blocking ability and stable semiconductor element characteristics.

[Brief description of the drawings]

FIGS. 1A to 1C are process diagrams for explaining an embodiment of a crystal growth method using an organometallic crystal growth method of the present invention.

FIGS. 2A and 2B are process diagrams for explaining a conventional method of manufacturing a light emitting diode having a current blocking layer.

[Explanation of symbols]

 10: P-InP layer 12: P-InP buffer layer 14: N-InP block layer 16: P-InP block layer 18: V groove 20: P-InP cladding layer 22: P-InGaAsP layer 24: N-InP cladding Layer 26: Current blocking layer 28: N-InGaAsP cap layer 30: P-InP substrate 32: Undoped layer 34: N-type layer (N-InP layer) 36: Current blocking layer 38: P-InP layer 40: P-InP layer

Claims (1)

(57) [Claims] An undoped layer is provided on an upper surface side of a first conductivity type substrate, and a current blocking layer is provided on an upper surface side of the undoped layer. The current blocking layer includes a first layer of a first conductivity type layer, A second conductivity type layer formed on the upper surface side of the first layer; and a second layer of the first conductivity type layer formed on the upper surface side of the second conductivity type layer. A semiconductor device comprising an undoped layer formed by a metalorganic vapor phase crystal growth method.