JPH05259577A - Semiconductor multilayer structure - Google Patents

Abstract

PURPOSE:To keep carrier concentration constant with excellent controllability, on a P-InP layer or a P-InP substrate of high concentration. CONSTITUTION:A semiconductor multilayer structure is constituted as follows; an InGaAsP layer 2 as a stopper layer for Zn is introduced in the interface between a Zn high concentration layer and a Zn low concentration layer or in a P-InP buffer layer 3. Thereby diffusion of Zn can be restrained by the InGaAsP layer 2, and the carrier concentration can be kept constant with excellent controllability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device.

[0002]

2. Description of the Related Art Conventionally, high concentration (1E18 or more) p-I
A semiconductor multilayer film grown on an nP substrate and a high concentration p-
In the semiconductor multilayer film including the InP growth layer, the change in carrier concentration due to Zn diffusion has been a problem.

An example of a device grown on a high-concentration (1E18 or more) p-InP substrate is the IEEE Journal of Quantum Electronics Vol.
6 No. 9), pp1460 (1990), there is an example in which the film thickness of the p-InP buffer layer is increased to 3 μm. Regarding the diffusion of Zn, Japanese Journal of Applied Physics No. 2
Volume 8 Issue 10 (JAPANESE JOURNAL OF APPLIED PHYSICS
vol.28, No.10), pp1700 (1989) and the like.

[0004]

The diffusion constant of Zn in the InP layer is as large as 10 ^-13 to 10 ^-12 cm ² / s. Therefore, the substrate during the multi-layer growth, the buried growth, and other processes Zn is diffused from the (p substrate) to the epi layer and from the high concentration layer to the low concentration. For example, 600 ℃, 4 × 10 ¹⁸ cm
^-3 , 1 hour diffuses about 1 μm. This diffusion is p-
When manufacturing a laser structure on an InP substrate, the substrate is 4 ×
The p-InP buffer layer has a high concentration of 10 ¹⁸ cm ^-3 , whereas the p-InP buffer layer has a low concentration of 1 to 8 × 10 ¹⁷ cm ^-3 . Particularly, in a semiconductor laser, when the carrier concentration exceeds 1E18, the threshold value may increase from several times to infinity. On the contrary, there is a method of lowering the carrier concentration of the p-InP buffer layer in consideration of this diffusion, but in this case, there is a problem that the resistance is newly increased.

An object of the present invention is to suppress such diffusion of Zn and accurately control the carrier concentration during multilayer growth, buried growth, and other processes.

[0006]

The suppression of Zn diffusion shown in the above problem can be achieved by putting a quaternary layer (InGaAsP) in the InP buffer layer or at the boundary between the high concentration layer and the low concentration layer.

That is, according to the present invention, the quaternary layer (InGaAs
By introducing P) as a stopper layer, diffusion of Zn can be suppressed and the carrier concentration can be kept constant with good controllability.

[0008]

Since Zn in InP has a large diffusion coefficient as described above, it easily diffuses as the carrier concentration increases and the temperature rises. On the other hand, since the diffusion coefficient of Zn in the InGaAsP mixed crystal is small (about 1/2 or less), the diffusion of Zn is suppressed and it becomes a stopper layer.

[0009]

EXAMPLE 1 FIG. 1 is a sectional view of a semiconductor multilayer according to Example 1, showing an example in which a quaternary layer is used as a boundary between a p-InP substrate and a p-InP buffer layer. Fabrication was carried out by p-InP substrate 1 (4E18) on the p-InP substrate 1 by metalorganic vapor phase epitaxy.
After the InGaAsP stopper layer 2 (wavelength 1.10 μm, hole concentration 3E17) was grown to a thickness of 0.1 μm, p
-InP buffer layer 3 (hole concentration 3E17, film thickness 1.0 μm), undoped InGaAsP active layer 4 (wavelength 1.
3 μm, film thickness 0.2 μm), n-InP clad layer 5
(Electron concentration is 2E18, film thickness is 1.0 μm), n-InG
aAsP cap layer 6 (wavelength 1.18 μm, film thickness 0.1.
3 μm) was sequentially grown.

FIG. 2 shows Zn from the active layer to the substrate at this time.
Shows the change in concentration in the depth direction. For comparison, a case without a conventional p-InGaAsP stopper layer is also shown. In the case of the conventional p-InP buffer layer only, Zn diffuses from the substrate to the buffer layer, and the carrier concentration of the p-InGaAsP stopper layer and further the InGaAs active layer changes. When (layer) was used, the carrier concentration could be kept constant. Thereby, for example, in a semiconductor laser,
It was possible to prevent an increase in threshold value (several times to ∞) accompanying an increase in carrier concentration (1E18 or more).

<Embodiment 2> FIG. 3 is a multilayer structure diagram of a second embodiment according to the present invention. In this embodiment, I shown in FIG.
A plurality of nGaAsP stopper layers are put in an InP buffer layer, which is more effective for a p-InP buffer layer having a low carrier concentration (about 1E18 to below) or a high concentration p-InP substrate (6E18 or more). Target.

<Third Embodiment> FIG. 4 is a cross-sectional view of a third embodiment of the present invention. The present embodiment is an example in which diffusion of Zn in the p-InP cladding layer is taken into consideration when grown on an n substrate. Fabrication is performed on the n-InP substrate 7 (1 to 2E18) by n
-InP buffer layer 8 (electron concentration is 2E18) 1.0 μm
After the growth of m film thickness, InGaAs / InP multiple quantum well (MQW) active layer 9, p-InGaAsP stopper layer 10 (wavelength 1.10 μm, film thickness 0.05 μm), p-
An InP clad layer 11 (hole concentration: 8E17, film thickness: 3.0 μm) and a p-InGaAsP cap layer 12 (wavelength: 1.18 μm, film thickness: 0.3 μm) were sequentially grown.
In this case, it is particularly effective when the temperature is 700 ° C. or higher in the process after the multilayer.

[0013]

FIG. 2 is a Zn concentration change showing the effect of the InGaAsP stopper layer.
If there is no P stopper layer, Zn from the substrate to the buffer layer
Diffuse into the p-InP buffer layer and further InGaA
While the carrier concentration of the s active layer was changed, the carrier concentration could be kept constant when the present invention (InGaAsP stopper layer) was used. Thus, for example, in a semiconductor laser, the carrier concentration increases (1E
It was possible to prevent the increase of the threshold value (several times to ∞) accompanying 18 or more), and it was possible to fabricate a low threshold laser with good reproducibility.

[Brief description of drawings]

FIG. 1 is a sectional view of a multilayer structure according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a concentration change of Zn in a depth direction.

FIG. 3 is a sectional view of a multilayer structure according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a multilayer structure according to a third embodiment of the present invention.

[Explanation of symbols]

1 ... p-InP substrate, 2 ... p-InGaAsP stopper layer, 3 ... p-InP buffer layer, 4 ... InGaAsP active layer, 5 ... n-InP clad layer, 6 ... n-InGaA
sP cap layer.

Claims (2)

[Claims] 1. A p-InP substrate or a high concentration of p-
In a semiconductor multilayer structure including an InP layer, the p-In
A semiconductor multilayer structure having an impurity diffusion suppressing layer in a P layer or at an interface between a high concentration and a low concentration layer. 2. The semiconductor multi-layer structure according to claim 1, wherein the impurity diffusion suppression layer is an InGaAsP layer.