JPH0350885A - Buried semiconductor optical element - Google Patents

Abstract

PURPOSE:To prevent a waveguide loss to be caused when an active layer is melted back from a transverse direction by a method wherein an antimeltback layer whose band gap is smaller that that of a core layer and is larger than that of a semiconductor buried layer is formed between the core layer and the semiconductor buried layer. CONSTITUTION:Au undoped InGaAsP active layer 2 with a wavelength composition of 1.54mum, an undoped InGaAsP antimeltback layer 3 with a wavelength composition of 1.3mum and a p-InP clad layer 4 are crystal-grown on the surface of an n-InP substrate 1 by an LPE growth method; after that, two grooves 12, 13 and a mesa stripe 14 1.0mum wide which is sandwiched between them are formed in the orientation [110]. Then, a p-InGaAsP AMB layer 5 with a wavelength composition of 1.3mum, a p-InP current-blocking layer 6 and an n-InP current-blocking layer 7 are crystal-grown on a semiconductor multilayer crystal excluding the upper part of the mesa stripe 14, and a p-InP buried layer 8 and a p<+> InGaAsP contact layer 9 with a wavelength composition of 1.2mum are crystal-grown on the whole surface by the LPE growth method. By using a buried semiconductor optical element manufactured in this manner, a waveguide loss can be reduced by about 10% as compared with conventional optical elements.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a buried semiconductor optical device without waveguide loss caused by lateral meltback of a core layer (active layer).

(Prior Art) In recent years, embedded semiconductor optical devices such as embedded semiconductor lasers, semiconductor optical amplifiers, and semiconductor optical waveguides have become increasingly important. An example of the structure of this type of embedded optical device is, for example, in 1985, Proceedings of the Institute of Electronics and Communication Engineers General National Conference on Optical and Quantum Electronics A, 85
It is described on page 7. Its structure is a double channel planar embedded structure (Double) as shown in Figure 2.
e Channel Planar Burie
d Heterostructure, hereinafter referred to as DC-P
In a four-wire horizontal structure with a BH structure (abbreviated as BH structure), n-I
On an nP substrate 1, a non-doped InGaAsP active layer 2 and an anti-meltback (AM
B) A layer 3, a p-InP cladding layer 4 are provided to form a mesa stripe 14, and furthermore, a p-1np current blocking layer 6, an n-InP current blocking layer 7, a p-InP buried layer 8, a p-InP In the figure showing the formation of the -1nGaAsP contact layer 9, 10 and 11 are electrodes, and 12 and 13 are electrodes.

As described above, since the conventional structure has a pnpn current blocking mechanism inside, the degree of current concentration in the striped active region is good, and as a result, a semiconductor laser using this structure has an oscillation wavelength of 1.3 μm. , oscillation threshold 15-20mA, optical output 50mW or more, maximum operating temperature 1
It has excellent properties such as a temperature of 20°C or higher. Further, in a semiconductor optical amplifier using this structure, a signal gain of 25 dB or more is obtained because the efficiency of current injection into the active layer is high.

(Problem to be Solved by the Invention) However, when manufacturing the above-mentioned conventional buried semiconductor optical device using a liquid phase epitaxial (LPE) growth method, the active layer (hereinafter, a light emitting device is taken as an example),
For the purpose of explanation, meltback from above the active layer is prevented by growing an anti-meltback layer before growing the cladding layer on the core layer (the core layer will be referred to as the active layer). As shown in FIG. 2, the core layer was melted back in the lateral direction during buried growth, which increased waveguide loss and also tended to deteriorate waveguide fabrication accuracy.

In this respect, conventional embedded semiconductor optical devices have problems to be solved. In particular, when using I n+-x Gag Asy P+-y, which is almost lattice-matched to InP, as the active layer, Applied Physics Letters (App
1. Phys, Lett,).

32 (4), 234 (1978), when the wavelength composition of the active layer is made longer than 1°4 μm, the active layer becomes more susceptible to meltback due to In melt, and the active layer becomes thicker. In this case, the meltback from the lateral direction becomes noticeable.

Furthermore, when considering a semiconductor optical amplifier as an embedded semiconductor optical device, it is necessary to take measures such as making the cross-sectional shape of the active layer close to a square in order to suppress the dependence of the amplification gain on the input light opening as much as possible. From the viewpoint of manufacturing technology, it is necessary to increase the active layer thickness to about 0.2 to 0.4 μm. Therefore, the active layer is more susceptible to meltback from the lateral direction.

An object of the present invention is to provide a buried semiconductor optical device that is free from waveguide loss caused by lateral meltback of the active layer.

(Means for Solving the Problems) In order to solve the above-mentioned problems, an embedded semiconductor optical device of the present invention is composed of at least one semiconductor layer having the functions of light waveguide, light emission, amplification, or a combination thereof. two semiconductor cladding layers that sandwich the core layer in the vertical direction and have a larger band gap energy than the core layer; and two semiconductor cladding layers that sandwich the core layer in the horizontal direction and have a larger band gap energy than the core layer. In a buried type semiconductor optical device having a striped structure including two semiconductor buried layers, an anti-semiconductor optical device having a band gap smaller than the core layer and larger than the semiconductor buried layer is provided between the core layer and the semiconductor buried layer. A meltback layer is provided.

(Function) As described above, in the present invention, since the anti-meltback layer is provided between the core layer and the semiconductor buried layer, the above-mentioned meltback can be prevented.

I EEE Journal Opquantum Electronics (
IEEE J, of Quantum Electr.
On, QE-17, 635 (1981)
When In+-eGagAsap,-, having a wavelength of 1.3 or more is used as an active layer, the anti-meltback layer has a wavelength composition of 1.3. I n l −X G a K over czm
It is necessary to use A S y P +-y. Therefore, in this material system, the wavelength composition is 1.3 to 1-4)
t m I n r-x G a z A S y P
By using ly as an anti-meltback layer, meltback of the active layer can be prevented.

(Example) Next, the present invention will be explained with reference to the drawings.

Figure 1 shows a 1.5 μm band InGa film according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an AsP DC-PBHtJ semiconductor laser.

First, the manufacturing method for obtaining this structure will be described below.

On the upper surface of the n-InP substrate 1, a non-doped InGaAsP active layer 2 with a wavelength composition of 1.54 μm, a wavelength composition of 1.3u,
m non-doped InGaAsP anti-meltback layer (
AMB layer) 3 and ρ-InP cladding layer 4 were grown to thicknesses of 0.1 μm, 0.01 μm, and 1 μm, respectively, by the LPE growth method.
After successive crystal growth in the [110] direction,
Two springs 12 and 13 with a depth of 1.5 μm and a width of 4 μm and a mesa stripe 14 with a width of 1.0 μm sandwiched between them are formed.

Next, p-InGaAs with a wavelength composition of 1.3 μm was placed on the semiconductor multilayer crystal except for the upper part of the mesa stripe 14.
A P AMB layer 5, a p I n P current blocking layer 6, an n-1nP current blocking layer 7, a p-InP buried layer 8 on the entire surface, and a p'' with a wavelength composition of 1.2 μm.
-I nGaAs P contact layer 9 has a thickness of 0.01 μm, 1 μm, 0.5 μm, and 6 μm at the flat portion, respectively.
Crystals are sequentially grown by the LPE growth method so as to have a thickness of 0.5 μm and 0.5 μm.

Furthermore, an electrode 10 made of Cr/Au is placed on the p side.
An electrode 11 made of AuGeNi is provided under the n-1nP substrate 1.
form.

According to the embedded semiconductor optical device manufactured in this way, the waveguide loss is 10% lower than that of conventional semiconductor optical devices.
The degree can be reduced. In addition, by using a method similar to that of the semiconductor optical device described above, the active layer is as thick as about 0.25 μm, and the mesa width is 0.4 μm, without causing the active layer to melt back from the lateral direction.
By fabricating an element as narrow as about μm and applying anti-reflection coating to both end faces, it is possible to fabricate a good semiconductor optical amplifier with a signal gain of 30 dB and a TE-7M gain difference of 1 dB or less.

In the above embodiments, the buried layer may be formed of a plurality of semiconductor layers of different conductivity types or a high resistance semiconductor layer, and
In+-tGaxA S y P ly-y in which the active layer and anti-meltback layer are almost lattice-matched to InP
It is also a preferable example that the wavelength composition of the anti-meltback layer is 1.3 μm or more at room temperature.

Furthermore, in the above embodiment, an example of an active semiconductor optical device (semiconductor laser or semiconductor optical amplifier) fabricated using a DC-PBH structure was explained, but it is also possible to fabricate an active semiconductor optical device (semiconductor laser or semiconductor optical amplifier) using a pond structure, such as a BHm structure. It is clear that the present invention can also be applied to passive optical waveguides. Furthermore, the semiconductor material used is not limited to InP-based materials.

Furthermore, although an example of an optical semiconductor device having a single semiconductor layer as a core layer has been described, the present invention is also effective for devices having a multilayer semiconductor layer such as a superlattice as a core layer.

(Effects of the Invention) As described above, it is possible to provide a buried semiconductor optical device without waveguide loss caused by the core layer being laterally melted back, which is useful.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a sectional view of a C-PBHW4 semiconductor laser, and FIG. 2 shows a conventional example of a DC-PHW semiconductor laser.
B) (It is a cross-sectional view of a structured semiconductor laser. 1-n-InP substrate, 2... non-doped InGaA
sP active layer, 3... anti-meltback layer, 1-p
InP cladding layer, 5-p InGaAsP anti-meltback layer, 6...p-1nP current blocking layer,
7...n-InP current blocking layer, 8=-p-InP
Buried layer, 9.=p"-InGaAsP contact layer, 10, 11.=Electrical Wi, 12°13... Clear, 14... Mesa stripe, 15... Direction in which the active layer is melted back.

Claims (1)

[Claims] A core layer composed of at least one semiconductor layer having the functions of light waveguide, light emission, amplification, or a combination thereof, and two semiconductor layers sandwiching the core layer in the vertical direction and having a larger band gap energy than the core layer. In a buried type semiconductor optical device having a stripe structure comprising a semiconductor cladding layer and two semiconductor buried layers that sandwich the core layer in the lateral direction and have a larger bandgap energy than the core layer, the core layer and the semiconductor buried 1. An embedded semiconductor optical device, further comprising an anti-meltback layer having a smaller bandgap than the core layer and a larger band gap than the semiconductor buried layer.