JPS5855904A - Manufacture of optical waveguide - Google Patents

Abstract

PURPOSE:To reduce the light losses of wavelengths near a forbidden band with respect to a semiconductor laser of double heterostructure of GaAs compds. by implanting atoms smaller than component atoms by ions into the part for forming an optical wavequide from the surface of the crystal and annealing the same. CONSTITUTION:An n<+>-GaAs buffer layer 12, an n<+>-GaAlAs lower clad layer 13, an n<->-GaAs active layer and an optical waveguide part 14, a P-GaAlAs upper clad layer 15, and a p-GaAs upper clad layer 16 are laminated by a liquid phase epitaxial method on an n<+>-GaAs substrate 11, whereby a semiconductor laser of double heterostructure is obtained. When electricity is conducted to an electrode 17, light is released from a cleavage surface 18. Atoms B smaller than atoms GaAs for forming the part 14 are accelerated and are implanted from the layer 16 into an ion implanting part 19. Then the B doped in the part 19 is annealed by a laser light to remove excessive defects. Thus the optical wavequide which decreases a coefft. 22 of adsorption corresponding to laser oscillating light 24 shown by the arrow mark is obtained and the light losses are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an m-■ group compound semiconductor optical waveguide having a novel configuration.

Recently, the performance and reliability of semiconductor lasers have improved, and on the other hand, as their applications in optical communications and optical information processing have become commonplace, semiconductor lasers have become integrated with attached optical switches rather than as standalone devices. The actual problem is whether to use it as a pulse generator or to adopt a complex structure such as a feedback structure or a smoke distribution feedback structure.

However, for this purpose, as shown in FIG. However, in optical circuits commonly used in the past, a cladding portion (6) is formed on the substrate crystal (5) by a method such as liquid phase epitaxial method.
) and optical waveguide # (7
) and further create an upper cladding part C8)° on top of it, and an electrode (9) is formed on a part of it.
), a current is injected to cause laser oscillation, the oscillation light (2) is caused to reciprocate over the entire optical waveguide (7) or a corresponding part of the optical waveguide (7), and oscillation is caused. Modulation and the like were performed by the use electrode On.

However, the biggest problem with a semiconductor laser having such a structure is that the loss due to light absorption in the optical waveguide is extremely large.
As a result, the oscillation light generated in the laser oscillation section is almost always lost, resulting in a disadvantage that either the oscillation threshold becomes extremely high or the length of the optical waveguide section that can be used as an optical circuit becomes extremely short. . Moreover, such an optical waveguide structure is essential for the lattice-matched double heterostructure required for a laser oscillator, and for this reason, an optical circuit or laser oscillator having a structure as shown in FIG. Its performance was significantly inferior to that of normal semiconductor lasers that utilize labor-opening planes, and it was not possible to develop it as a practical device.

It is an object of the present invention to eliminate such drawbacks in conventional optical waveguides using double heterojunctions, and to provide a method for manufacturing optical waveguides that is easy to manufacture and can significantly reduce optical loss.

The present invention is based on the layered double heterostructure force of a ■-■ group compound semiconductor: In a gala optical waveguide, atoms with an atomic weight lighter than the average atomic weight of the constituent atoms are accelerated almost uniformly in the optical waveguide and cladding portion at high speed. This can be achieved by implanting the wafer and annealing it by a known method.

In order to further clarify the features and main advantages of the present invention, an example will be described below.

As shown in Figure 2, n+ -GaAs substrate crystal aυ
An n+-GaAs buffer layer 02+ an n+-GaAIAs lower cladding layer 1 is formed on top by liquid phase epitaxial method.
31゜n-GaAs active layer and optical waveguide section (1
41, p-GaAJAs upper cladding a (15) s
A pG a As upper covering layer αe is successively formed, and an electrode aη and an arm opening OQ on only one side are formed in a portion where a semiconductor laser is to be formed.

After that, the part K other than the semiconductor laser which becomes the guiding waveguide is
B atoms are implanted by the ion implantation method so that the optical waveguide section and a considerable part of the cladding section are uniformly doped with #1 as shown in the figure 0. Then, annealing is performed using a known furnace, laser beam, or electron beam. When excessive defects are removed by the method, the absorption edge in the first absorption curve 11#f)K moves slightly to the shorter wavelength side and becomes curve 1s123, as shown in Figure #I3, and the damage caused by the implanted atoms is removed. Therefore, the additional absorption (2) increases, but the absorption coefficient corresponding to the wavelength of the laser oscillation light (indicated by the arrow) (24) significantly decreases to about 10 to 10zclL-4,
It is possible to obtain a practical optical waveguide.

In the above-mentioned embodiment, even if Aj or P' is injected instead of B, the same result in terms of tl can be obtained. Special K
When B or AI and P are implanted in the same atomic ratio,
As shown in FIG. 3, the absorption due to pressure injuries tends to decrease.

The number of P atoms to be implanted across B and AI varies depending on the situation, but the absorption edge of the optical waveguide is t1! '20~3
It is sufficient to move QmeV, and in an example of an experiment, 5
* Approximately 10” atoms/cam.

It can be realized not only in the GaAa-GaA/As ternary double heterostructure, but also in the InP-InGaAsP quaternary double heterostructure, for example, by implanting atoms that are lighter than the average composition. .

A low-loss optical waveguide coupled to a semiconductor laser having such a structure can be used, for example, in a planar semiconductor laser using a distributed constant reflector, or as a mode locker by inserting an optical waveguide section and an optical switch. It has a wide range of applications, including realizing an integrated repeating optical pulse train generator.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a conventional optical circuit, where 1 is the oscillation part of the semiconductor laser, 2 is the oscillation light, 3 is the optical waveguide, 4 is the Fi switch part, 5 is the substrate crystal, 6 is the cladding part, and 7 is the active part. layer and optical waveguide section, 8J- is the upper cladding section, 9 is the electrode,
10 is a modulation electrode. Figure 2 is a schematic cross-sectional view of an embodiment of the present invention.
+-GaAs substrate crystal, 12 is n+-GaAa buffer layer, 13 is n+-GmA/As lower cladding layer, 14 is n--GaAs active layer and optical waveguide layer, 15 is f)
16 is a GaAs upper cladding layer, 17 is an electrode, 18 is an opening surface, and 19 is a B atom implantation part.

Claims (1)

[Claims] In a semiconductor optical waveguide that is made of GaAn or a ■-■ group compound conductor with properties similar to it, and has a structure in which it is laminated on a substrate crystal and has nine optical waveguides and a cladding part, the optical waveguide is An optical waveguide can be formed by implanting ions made by accelerating atoms of the group II or group II, which have an atomic mass smaller than the average atomic mass of the atoms forming the wave part, and performing 7-nealing using a known method. A method for manufacturing an optical waveguide that increases the forbidden band width of the optical waveguide, thereby significantly reducing optical loss at wavelengths near the forbidden band width of the optical waveguide.