JPH0766993B2 - Semiconductor optical amplifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor optical amplifier device, for example, a semiconductor laser device in which a semiconductor laser device that emits a laser beam from a resonator (optical waveguide) end of an end face is provided with an optical amplifying action. Alternatively, it relates to a semiconductor optical amplifier element such as an integrated optical device (OEIC element) having such a semiconductor laser element portion.

[Background technology]

As a light source for optical communication or a light source for information processing of digital audio discs, video discs, laser beam printers, etc., for example, "Electronic Materials" 1983
Semiconductor lasers have been developed as described in P39-48, October issue of 1983, issued October 1, 1983. These semiconductor lasers (semiconductor laser elements: laser chips)
In most of these, as shown in the above-mentioned document, electrodes are provided on a pair of front and back surfaces sandwiching an optical waveguide, and a predetermined voltage is applied between the pair of electrodes (anode electrode, cathode electrode). Then, the laser light is emitted from the end surface (mirror surface) of the optical waveguide.

By the way, according to the failure analysis conducted by the present inventor, it was found that among defective products in which laser oscillation does not occur, when the applied voltage is increased to the threshold current value or more, the laser oscillation suddenly occurs. That is, as shown in FIG. 2, in the electrodes 3 and 4 of the optical waveguide (resonator end face) 2 of the laser chip 1, when there is a missing electrode due to a pinhole or the like in the portion corresponding to the optical waveguide, In the optical waveguide portion corresponding to the electrode missing portion 5, as shown in FIG. 3, the current 6 does not sufficiently flow, so that the excitation is not sufficient in the optical waveguide 2 portion corresponding to the electrode missing portion 5, As shown in the graph of FIG. 4 in which the vertical axis represents the light output (Po) and the horizontal axis represents the injection current (I), the laser light does not oscillate at the predetermined threshold value a. Therefore, in an actual work site, such a laser chip is treated as a defective product.

However, even in the laser chip 1 having such an electrode missing portion 5, a current (b) relatively larger than the threshold current value is obtained.
It was found that the laser beam with a large output suddenly emitted when the current was passed.

Therefore, the present invention has been realized by providing an independent electrode at the electrode missing portion 5 and using this electrode as a trigger electrode, it is possible to obtain a semiconductor optical amplification device capable of laser oscillation with a small signal current. .

[Object of the Invention]

An object of the present invention is to provide a semiconductor optical amplifier device capable of controlling oscillation of high-power laser light with a small signal current.

The above and other objects and novel characteristics of the present invention are
It will be apparent from the description of the present specification and the accompanying drawings.

[Outline of Invention]

The outline of a typical one of the inventions disclosed in the present application will be briefly described as follows.

That is, the present invention provides an optical waveguide which is provided below a clad layer in a semiconductor substrate and has end faces on a pair of side surfaces of the semiconductor substrate facing each other, and an optical waveguide provided on the upper main surface of the semiconductor substrate with the waveguide interposed therebetween. A semiconductor laser amplifying device having a semiconductor laser structure having an anode electrode provided on the semiconductor substrate lower main surface, and an anode electrode provided on the semiconductor substrate upper main surface on the optical waveguide. ,
A trigger electrode for applying a signal current provided corresponding to the central portion of the optical waveguide, and sandwiching the trigger electrode, and provided away from the trigger electrode,
A main body on a semiconductor substrate which is composed of a U-shaped drive electrode for applying a current that does not cause laser emission, and which is located between the trigger electrode and the drive electrode and is located on the optical waveguide. A pair of slits located at the end position in the clad layer extending from the surface to the vicinity of the optical waveguide are provided, an insulating film is embedded in the slits, and a signal current is applied to the trigger electrode to cause the optical waveguide to move. It is designed to pass a current through the entire length of the optical waveguide so that laser light is emitted from the end face of the optical waveguide.When a small signal electrode is applied to the trigger electrode, high-power laser light is oscillated, so the optical amplification effect Produced and high performance can provide semiconductor optical amplifier device.

〔Example〕

FIG. 1 is a perspective view showing the outline of a semiconductor optical amplification device according to an embodiment of the present invention, and FIG. 5 is a state in which no signal is input to the trigger electrode of the semiconductor optical amplification device shown in FIG. 6 is a schematic cross-sectional view showing a current flow state in FIG. 6, FIG. 6 is a schematic cross-sectional view showing a current flow state in a laser emission state of the semiconductor optical amplifier, and FIGS.
FIG. 12 is a view showing a wafer which is a work in each manufacturing step in manufacturing the semiconductor optical amplifier device according to one embodiment of the present invention, and FIG. 7 is used for manufacturing the semiconductor optical amplifier device of the present invention. FIG. 8 is a cross-sectional view of the wafer subjected to the mesa etching, FIG. 8 is a cross-sectional view of the wafer subjected to the buried growth treatment, and FIG. 10 is the mid-depth of the cladding layer on the optical waveguide. A cross-sectional view showing the etched state, FIG. 11 is a cross-sectional view of a wafer subjected to zinc diffusion treatment,
FIG. 12 is a sectional view of the wafer with electrodes formed,
The figure is a perspective view showing a semiconductor optical amplifier.

The semiconductor optical amplifier element (also referred to as a chip) in this embodiment has a structure as shown in FIG.
Further, this chip is manufactured through the manufacturing steps shown in FIGS.

In this embodiment, an example in which the present invention is applied to a semiconductor laser device (laser chip) having a buried hetero structure (BH) used for optical communication will be described.

For a description of the structure of the chip as shown in FIG.
This will be explained by explaining the manufacturing state shown in FIGS. 7 to 12.

In manufacturing a laser chip, first, a compound semiconductor thin plate (wafer) 7 as shown in FIG. 7 is prepared. This wafer 7 is an n-type InP substrate 8 and (100) of this substrate 8.
A multilayer growth layer 13 composed of an n-type InP buffer layer 9, an InGaAsP active layer 10, a p-type InP clad layer 11, and a p-type InGaAsP cap layer 12 sequentially formed on the crystal plane by a liquid phase epitaxial method, The buffer layer 9, the active layer 10, and the cladding layer 11 form a double heterojunction structure. The substrate 8 has a thickness of about 200 μm, and the active layer 10
Has a thickness of 0.15 μm, and each of the other layers has a thickness of about 1 to 2 μm.

Next, as shown in FIG. 8, an insulating film (SiO ₂ ) is formed on the main surface (upper surface) of the wafer 7 by a CVD (chemical vapor deposition) method, and this insulating film is partially formed by photolithography. 5 to 6 width parallel to <110> cleavage direction
A large number of stripe-shaped masks 14 of μm are formed. After that, the semiconductor layer exposed from the mask 14 of the wafer 7 is etched with an etching solution such as bromethanol.
The etching is performed so as to reach the middle of the buffer layer 9 or the surface layer portion of the substrate 8. In this embodiment, the etching reaches the middle of the buffer layer 9. As a result of anisotropic etching, the upper portion of the active layer 10 covered with the mask 14 becomes an inverted mesa portion whose cross section is an inverted triangle and the crystal <
It remains in the form of stripes along the 110> direction, and a downward mesa portion from the active layer 10 forms a parabola. The mask interval is about 400 μm.

Next, the mask 14 partially extending on the main surface of the wafer 7 is removed. Then, as shown in FIG. 9, the p-type InP blocking layer 15, n is formed in the recessed portion by etching.
The buried layer 16 of InP type and the cap layer 17 of InGaAsP type are sequentially buried by the epitaxy method.

Next, as shown in FIG. 10, an insulating film 18 made of SiO ₂ or the like is partially formed on the main surface of the wafer 7 by photolithography. The insulating film 18 serves as an etching mask for etching the active layer 10, that is, the upper portion of the cladding layer 11 which is the upper layer of the optical waveguide in a slit shape. Therefore, using the insulating film 18 as a mask, the upper portions of the cap layer 12 and the clad layer 11 are etched to form the slit 19. This is to prevent current from flowing across the portion of the cladding layer 11 directly below the slit 19. That is, this semiconductor optical amplification element (chip) 20 has a trigger electrode 21 to be described later on the cap layer 12 sandwiched by a pair of slits 19 as shown in FIGS. 5, 6 and 13. A drive electrode 22 to be described later is provided on the outside of the slit 19, but with a structure taken so that the current injected by the drive electrode 22 flows into the optical waveguide portion directly below the chip 20. Therefore, the controllability of laser light emission is improved.

Next, as shown in FIG. 11, an insulating film 23 made of SiO ₂ or the like is formed on the entire main surface of the wafer 7 by photolithography, and is partially removed. The insulating film 23 fills the slit 19. The insulating film embedded in the slip 19 can prevent contamination (for example, entry of foreign matter) in the slit 19. The insulating film 23 is not provided on the surface of the stripe-shaped mesa portion. Therefore, the insulating film 23 is used as a mask to remove zinc (Zn) from the wafer 7.
A zinc diffusion region 24 (dotted region) is formed by being implanted into the main surface of the clad layer 11 and reaching the middle depth of the clad layer 11.
This zinc diffusion region 24 becomes an ohmic layer of the contact electrode.

Next, the back surface of the wafer 7 is etched so that the entire thickness of the wafer 7 is about 100 μm. Thereafter, as shown in FIG. 12, an anode electrode 25 is provided on the main surface of the wafer 7 and a cathode electrode 26 is provided on the back surface thereof. The anode electrode 25 is Cr / Au, the cathode electrode 26 is AuGeNi / Pd / Au,
Both are formed by vapor deposition and alloy processing. As shown in FIG. 13, the anode electrode 25 is composed of a trigger electrode 21 and a driving electrode 22 and is electrically independent of each other. That is, the current injection portion 27 of the trigger electrode 21 extends to the central portion of the optical waveguide just above the optical waveguide, and the current injection portion 28 of the drive electrode 22 has a U-shape as shown so as to sandwich the trigger electrode 21. And extends above both ends of the optical waveguide. The trigger electrode 21 and the drive electrode 22 have a large bonding area for connecting wires on both sides of the chip 20 so as to sandwich the optical waveguide.
It has 29,30.

Next, such a wafer 7 is vertically and horizontally divided, and as shown in FIG. 13, chips 20 having a length and width of several hundred μm and a height of about 100 μm are manufactured.

When such a semiconductor optical amplifier device is used, a desired voltage between the drive electrode 22 and the cathode electrode 26 of the anode electrode 25 (for example, larger than the threshold current value a shown in the graph of FIG. A small current) is always applied, and the signal current is guided to the trigger electrode 21 of the anode electrode 25. As a result, when no signal is input to the trigger electrode 21, as shown in FIG.
Since a current flows between the (electrode 4) and the driving electrode 22 of the anode electrode 25, and no current flows in the central portion of the optical waveguide,
Laser oscillation does not occur. However, when a signal current flows through the trigger electrode 21 of the anode electrode 25, the current flows through the optical waveguide along its entire length as shown in FIG. 6, and the laser light 31 is emitted from the mirror surfaces at both ends of the optical waveguide. This laser light 31 is applied to the trigger electrode 21 and the drive electrode 22.
Since a current flows in the current value, the current value becomes the current value b in the graph of FIG. 4, and the output is high. Therefore, this semiconductor optical amplifier device can emit high-power laser light with a small signal current.

〔effect〕

(1) In the semiconductor optical amplifier device of the present invention, the current injection part 28 of the drive electrode 22 is arranged on both ends of the optical waveguide, and the current injection part 28 is provided.
The current injection part 27 of the trigger electrode 21 is provided above the optical waveguide between
When used, a current is passed to the cathode electrode 26 and the drive electrode 22, which is a part of the anode electrode 25, to the extent that laser emission does not occur, and a signal current is passed to the trigger electrode 21. As a result, high output laser light can be emitted even with a small signal current, and a high optical amplification effect can be obtained.

(2) According to the present invention, a pair of slits positioned in the cladding layer extending from the main surface of the semiconductor substrate located on the optical waveguide between the trigger electrode and the driving electrode to the vicinity of the optical waveguide. Is provided and an insulating film is embedded in the slit, and a signal current is applied to the trigger electrode so that the current flows through the entire length of the optical waveguide, so a high efficiency optical amplification effect can be obtained with a small signal current. And there is no problem of pollution.

(3) According to the present invention, by applying the present invention to an optical module, an optical IC, or the like having a laser emitting portion, it is possible to obtain an effect that highly accurate laser emission control can be performed with a small current.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments and various modifications can be made without departing from the scope of the invention. In addition, by selecting the width of the trigger electrode, for example, it is possible to sufficiently deal with the magnitude of the signal and the change in the purpose of use, and the same effect as the above embodiment can be obtained. Further, the present invention can be applied regardless of the device structure of the semiconductor laser, and the same effects as those of the above-described embodiment can be obtained.

[Field of application]

In the above description, the case where the invention made by the present inventor is mainly applied to the technology for optical communication which is the background field of application is described, but the invention is not limited thereto, and for example, visible light by GaAIAs system. It can be applied to measurement technology and medical technology using semiconductor lasers.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of a semiconductor optical amplifier device according to an embodiment of the present invention, FIG. 2 is a schematic perspective view showing a conventional semiconductor laser device having an electrode missing, and FIG. 3 is also having an electrode missing. FIG. 4 is a graph showing a high-power laser oscillation state in a high current state of a semiconductor laser element having a missing electrode, which is a cross-sectional schematic view of a semiconductor laser element showing a current flow in a state. FIG. 6 is a schematic cross-sectional view showing a current flow state in the state in which no signal is input to the trigger electrode of the semiconductor optical amplification element shown in the figure and no laser emission is generated. FIG. 7 is a cross-sectional schematic view showing a flow state, FIG. 7 is a cross-sectional view of a wafer used for manufacturing the semiconductor optical amplifier device of the present invention, FIG. 8 is a cross-sectional view of a wafer subjected to mesa etching, and FIG. Included A cross-sectional view of the wafer subjected to the growth treatment, FIG. 10 is a cross-sectional view showing a state where the cladding layer on the optical waveguide is etched to an intermediate depth, and FIG. 11 is a cross-sectional view of the wafer subjected to the zinc diffusion treatment, FIG. 12 is a sectional view of the wafer with electrodes formed thereon, and FIG. 13 is a perspective view showing a semiconductor optical amplifier device. 1 ... Laser chip, 2 ... Optical waveguide (end face of resonator),
3,4 ... electrode, 5 ... electrode missing part, 6 ... current, 7 ...
... Compound semiconductor thin plate (wafer), 8 ... Substrate, 9 ... Buffer layer, 10 ... Active layer, 11 ... Clad layer, 12 ... Cap layer, 13 ... Multilayer growth layer, 14 ... Mask, 15 ...... Blocking layer, 16 …… Embedding layer, 17 …… Cap layer,
18 ... Insulating film, 19 ... Slit, 20 ... Semiconductor optical amplifier (chip), 21 ... Trigger electrode, 22 ... Drive electrode,
23 ... Insulating film, 24 ... Zinc diffusion region, 25 ... Anode electrode, 26 ... Cathode electrode, 27 ... Current injection part, 28 ... Current injection part, 29, 30 ... Bonding region, 31 ... Laser light

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-55-133587 (JP, A) JP-A-53-67390 (JP, A) JP-A-52-6479 (JP, A) JP-A-59- 165480 (JP, A)

Claims (1)

[Claims] 1. A semiconductor substrate provided below a cladding layer,
And an optical waveguide having end faces on a pair of opposite side surfaces of the semiconductor substrate, an anode electrode provided on the upper main surface of the semiconductor substrate and a cathode electrode provided on the lower main surface of the semiconductor substrate with the waveguide interposed therebetween. A semiconductor laser amplifying device having a semiconductor laser structure having an anode electrode provided on the main surface of the semiconductor substrate on the optical waveguide, the signal current being provided corresponding to a central portion of the optical waveguide. With a trigger electrode for applying a current, and a U-shaped drive electrode sandwiching the trigger electrode and provided apart from the trigger electrode for applying a current that does not cause laser emission. In the clad layer, which is configured and extends between the trigger electrode and the drive electrode and extends from the main surface of the semiconductor substrate located on the optical waveguide to the vicinity of the optical waveguide. A pair of slits located at the end positions are provided, an insulating film is embedded in the slits, a current is passed through the entire length of the optical waveguide by applying a signal current to the trigger electrode, and laser light is emitted from the end face of the optical waveguide. A semiconductor optical amplifier device characterized by emitting light.