JPS60207390A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To stabilize an output, and to improve reproducibility by forming a semiconductor laser having buried type double hetero-structure and a photodetector on the same substrate and detecting laser beams from the semiconductor laser by the photodetector. CONSTITUTION:A P type CaAlAs layer 22 and three layers or more of two kinds of compound semiconductor thin-films having different forbidden band width are laminated on a substrate 21, and quantum well type structure is used as an active layer 24. An N type GaAlAs layer 23 having forbidden band width larger than that of semiconductors is shaped as an upper clad layer, thus forming double hetero-junction structure. An N type GaAs layer 25 as an uppermost layer is etched by utilizing a mask 26 for diffusing an impurity, and the P type impurity is diffused. The two semiconductors constituting a quantum well type are alloyed in an impurity diffusion region in the active layer 24, forbidden band width is made larger than a light-emitting region in the lower section of the N type GaAs layer 25 and an optical waveguide, and a refractive index is reduced. The performance of a laser is improved, and the yield of products is enhanced largely.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a semiconductor laser in which a semiconductor laser having an active region of a quantum well type layer, an optical waveguide, and a photodetector are configured on the same substrate, and the semiconductor laser and the photodetector are optically connected. The present invention relates to a device and a method for manufacturing the same.

Conventionally, a single mode oscillation semiconductor laser device has a buried heterostructure in which an active region is surrounded by a semiconductor device having a large forbidden band width. This buried heterostructure laser device is manufactured using two liquid phase growth methods and mesa etching. That is, a double heterostructure crystal is created in the first liquid phase growth, and this crystal is chemically etched into a mesa stripe shape, and then in the second liquid phase growth, the mesa stripes have a forbidden band width. embedded by a large semiconductor.

As described above, the conventional buried type heterostructure laser device has a complicated manufacturing process, and it is difficult to control the stripe width, resulting in poor product yield.

In view of the above, the applicant has proposed that the upper and lower parts of the active layer of the quantum well structure are made of semiconductors having a composition larger than the average composition of the two types of semiconductors that make up the quantum well structure, and that the left and right parts of the active layer are We have proposed a semiconductor laser device consisting of a semiconductor with an average composition in a quantum well structure by diffusing zinc into the well structure.

This semiconductor laser device uses a quantum well structure as an active layer by simply performing an impurity diffusion process on a multilayer semiconductor crystal growth layer formed by an epitaxial growth method.
390(2) No. 79).

However, since the output of a semiconductor laser device changes sensitively depending on the temperature, it is necessary to constantly detect the output and feed back the output to stabilize the output. Until now, the semiconductor laser device manufactured as described above was placed on a metal mount together with a separately manufactured photodetector to detect the output of the laser beam oscillated by the laser device, but the alignment of both devices was required complicated work.

The purpose of the invention is to provide the above-mentioned embedded type double heterostructure semiconductor laser and a photodetector on the same substrate, detect the laser light of the semiconductor laser with the photodetector, and stabilize the output. It is an object of the present invention to provide a semiconductor device and a method for manufacturing the semiconductor device easily and with good reproducibility.

Hereinafter, the present invention will be explained based on the attached drawings. FIG. 1 shows a third embodiment of the semiconductor device of the present invention, / is a p-type semiconductor substrate, and on top of this semiconductor substrate An active layer having a nine-quantum well structure, which will be described later, is present as a cladding layer. Compound semiconductors constituting this quantum well structure include GaAs, GaAlAs, and G
Examples include binary, quinary, and quaternary semiconductors having different forbidden band widths, such as cLAgP, GaInAs, and InGaAsP. Above the active layer, there is an n-type semiconductor layer 3 as an upper cladding layer, which has a wider forbidden band width than the semiconductor constituting the active layer.

At the center of the upper surface of the upper cladding layer 3, a striped n-type semiconductor 5α having a narrower forbidden band width than the cladding layer is provided in the direction of the laser resonator. Furthermore, an n-type semiconductor layer is similarly provided at the end of the upper cladding layer 3 at a position where a photodetector is to be formed (FIG. 2).

Lower cladding layer 2t under this striped semiconductor 3α
The impurity diffusion region (in which a p-type impurity such as zinc is diffused) is formed, except for the straight line section α reached at , and the curved section 7b which branches off midway through the straight line section α6- and extends toward the n-type semiconductor. Shaded area in Figure 2)
The impurity diffusion region 6 of the active layer l is formed by alloying two types of semiconductors constituting a quantum well structure.The impurity non-diffusion region of the active layer D becomes an optical waveguide. ? , constitutes a light 1 detector.

: A striped n-type semiconductor on the upper cladding layer 3; an insulating film except for the area where the body 3α is provided and the area where the n-type semiconductor sb serving as a photodetector is provided. Cover with

In addition, in order to prevent leakage current that does not pass through the light emitting region Zα from occurring, the n-type semiconductor Sα and the impurity diffusion region of the upper cladding layer 3 are electrically connected via the impurity non-diffusion region of the upper cladding layer 3. state. There is an outer electrode /θ on the top surface of the n-type semiconductor jα, and a p-side electrode // on the bottom surface of the semiconductor substrate /.
There is an electrode for a photodetector on the upper surface of the type semiconductor 3b,
A semiconductor device as shown in FIG. 1 is constructed.

In this semiconductor device, an electron current is applied to the n-side electrode 10,
When a hole current is supplied to the p-side electrode, the current is concentrated in the active layer (light emitting region) ga in the straight line portion 7α of the impurity non-diffused region. Since both sides of this light-emitting region 7α are composed of impurity diffusion regions in which the quantum well structure is alloyed, the linear portion 7α of the impurity non-diffusion region of the active layer 2 is bent from the light-emitting region. A semiconductor laser is constructed with the active layer & as a light emitting region, and the light emitting region has a quantum well structure.
A single mode laser beam in the lateral direction is oscillated at a small oscillation threshold current.

Note that if a p-type semiconductor layer with a lower refractive index than the lower cladding layer is interposed as a light guide layer between the lower cladding layer and the active layer, light confinement will be more effective and the laser beam will be The oscillation threshold current also becomes lower.

Straight line part of the impurity non-diffused region of the active layer? When a laser beam oscillates in the light emitting region Sα of The tip of the curved portion 76? , to a photodetector configured in .

The tip that becomes a photodetector? , is p as shown in FIG.
A reverse bias is applied to the p-outer junction with the -n junction to form a depletion hermitage, and in this state, the optical waveguide rb
As the light propagates further, the detected electrical signal is fed back to the far side of the semiconductor laser,
The laser output power destination can be controlled to be constant.

Next, an embodiment of the method for manufacturing a semiconductor device of the present invention will be described. First, after organic cleaning and chemical etching of the p-type Gaza substrate crystal 2/, molecular beam epitaxial growth method,
Substrate using vapor phase epitaxial growth method! A p-type GaAjAa layer having a large forbidden band width than the semiconductor constituting the active layer is formed as a lower cladding layer on the active layer. Next, three or more layers of two types of compound semiconductor thin films having different forbidden band widths are alternately laminated on the lower cladding layer λλ to a thickness of several tens to several hundreds of times, and this quantum well structure is used as an active layer 2II. Next, on top of the quantum well structure active layer, we added n-type GaAJAa, which has a large forbidden band width compared to the semiconductor that constitutes the active layer.
Layer 3 is formed as an upper cladding layer to form a so-called double heterojunction structure.

The upper cladding layer 3 has a narrow forbidden band width n! J! A GaAs layer is grown to connect to the ohmic electrode. Substrate crystal, if necessary
A p-type GaAa layer or a 911 GaAjAs layer may be provided as a buffer layer between 21 and the lower cladding layer 10-.

Once the multilayer structure is formed as described above, a film of silica, silicon nitride, etc. is deposited on the n-type Gaps layer, and as shown in Fig. Remove all but the curved portion and use it as a mask roller for impurity diffusion. Next, using this mask 26, the uppermost n-type GaAa layer 23 is etched into a mesa shape to have a similar shape to the mask, and then a p-type impurity such as zinc (Zn) is heated from the top surface. is diffused until it reaches at least the lowest layer of the semiconductor ultra-thin film of the quantum well structure that constitutes the active layer 2.

In FIG. 4, impurity diffusion regions are indicated by diagonal lines.

The depth and lateral diffusion of impurities is controlled by the impurity diffusion temperature and diffusion time. In this way, due to the diffusion of impurities, the impurity diffusion region of the active layer 21 is formed by alloying the two semiconductors forming the quantum well type, and forming a non-diffusion region, that is, a linear portion that becomes a light emitting region under the n-type GaAa layer 2S. The forbidden band width of the curved portion that becomes the optical waveguide also becomes larger, and the refractive index becomes smaller.

Next, the mask 26 is removed, and uGeNi alloys 2g and 30 are vapor-deposited on the straight portion 25α and the tip 5b of the straight GaAs layer of the 8-layer n-type GcLA layer 3, respectively) for the outer electrode and photodetector. Use as an electrode. Also, the board 2/
After polishing the back surface, a Crku alloy 29 is deposited to form a p-side electrode. Finally, both end surfaces of the multilayered structure formed are placed between the bones to form a resonator.

The semiconductor device manufactured in this way is shown in FIG.
The striped portion of the active layer 21I that does not diffuse impurities serves as a laser emission region, the curved portion serves as an optical waveguide, and the tip of the curved portion, that is, the n-type semiconductor 2SbT portion serves as a photodetector. A part of the laser light oscillated in the light emitting region of the laser is guided to a photodetector through an optical waveguide, and the output intensity of the oscillated laser light is measured.

Note that the curved portion 7 that does not diffuse impurities and becomes an optical waveguide
b is not only curved in the side direction as in the embodiment shown in FIG. 2, but also partially curved and partially straight, with a photodetector provided near the interfold surface, as shown in FIG. You can do it like this.

Furthermore, in the above explanation, a lower cladding layer, an active layer, an upper cladding layer, and a striped semiconductor are formed using a p-type semiconductor layer on a p-type semiconductor substrate, and ions such as silicon are implanted to form an n-type impurity diffusion region in the active layer. A semiconductor device having the same functions as those described above can be constructed even when the light emitting region and the optical waveguide are formed.

As is clear from the above description, the semiconductor device according to the present invention uses a crystal growth process of a multilayer structure using molecular beam epitaxial growth or vapor phase epitaxial growth with good film thickness controllability, and a mask formation process using Fore3-trithography. Self-alignment (self-alignment) that does not require formation or separate mask alignment technology
By using an extremely simple impurity diffusion process, it is possible to integrate an embedded laser with a quantum well structure as an active layer, an optical waveguide, and a photodetector on the same substrate, significantly improving the performance of the laser. This will greatly improve product yield.

Next, the present invention will be explained with reference to examples.

100X thick GaAs layer and 70X thick Ga6 layer
4Aj6. A total of 10 zAs layers are formed alternately, followed by an n@Qα layer with a normal thickness of 1.5μ as an upper cladding layer.
. , 1IAlo, IIAB layer and 0.5μ normal thickness n-type G
The aA6 layer was crystal grown.

After silicon nitride was deposited on the upper surface of this multilayer structure, a mask having a straight line portion having a width of approximately 4 μm and curved portions branching from the straight line portion was formed by photo-/4'-lithography. Using this mask, the uppermost n-type GaAs layer is etched into a mesa shape, and then zinc is diffused at a temperature of 600° C. until it reaches the bottom layer of the active layer. The non-diffused region of zinc in the active layer was narrower than the mask width, about 2.5 μm, due to the presence of lateral diffusion.

Next, the portion of the uppermost n-type GaAs layer where zinc was diffused was removed by side etching, and the
℃ to form an oxide film on the exposed n-type GaAjAa layer, and the silicon nitride used as a mask was removed, and then the curved part of the uppermost outer mold GaAs layer was cut at the tip. The n-type GaAs layer on the straight line and the tip was covered with an insulating film, and then AuGεN (alloy) was evaporated on the straight n-type GcLAa layer to form the n-side electrode. An A5LGeNi alloy was also deposited on the n-type GaAs layer at the tip to form an electrode for a photodetector.The bottom surface of the p-type GaAa substrate was polished and CrAu was deposited on it to form a p-side electrode, with both ends opened at the arms. Then, it was cut into a semiconductor device having a length of about 300 μm and a width of about 400 μm.

-13- The oscillation threshold current of the laser of this semiconductor device at room temperature is 5
m), The oscillation wavelength was 7800X, and a fundamental single mode laser beam was oscillated. In the photodetector, there are 5 laser outputs with an IV of 0.02 for a fluctuation of 0.1fiW.
fiV, and this value was large enough to detect the output of the semiconductor laser.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a semiconductor device according to the present invention, FIG. 2 is a partially cut away perspective view of the semiconductor device, and FIG. 3 is a cross-sectional view showing the structure of a photodetector of the semiconductor device. figure,
4 to 6 are perspective views showing the manufacturing process of the semiconductor device of the present invention, and FIG. 7 is a plan sectional view showing another arrangement of the optical waveguide and photodetector of the semiconductor device. /...Semiconductor substrate, Co...Lower cladding layer, 3...
・Upper cladding layer, da...active layer, 3α, jb...
N-type half--insulating film, 10...n-side electrode, ll...
- P-side electrode, 12... electrode for photodetector. Patent applicant Hirobe Kawada, Director of the Agency of Industrial Science and Technology

Claims (2)

[Claims] (1) A stripe-shaped light-emitting region is formed in the center of the active layer with a quantum well structure, which is sandwiched between upper and lower compound semiconductor layers with a composition larger than the average composition of the two types of compound semiconductors that make up the active layer, in the direction of the laser cavity. a semiconductor laser provided with the active layer, a photodetector having a p-n junction structure provided at an end of the active layer, one end optically connected to the light emitting region of the semiconductor laser, and the other end optically connected to the photodetector. 1. A semiconductor device comprising optical waveguides that are connected to each other. (2) The average composition of the two semiconductors constituting the active layer is larger than the upper and lower sides of the active layer of the quantum well structure, which is constructed by alternately stacking three or more layers of two compound semiconductor thin films with different compositions. a mask that is integrated with a multilayer structure sandwiched by compound semiconductor layers having the same composition, and has a straight line part and a curved part branching from the middle of the straight line part and extending outward on the upper surface of the multilayer structure. Then, using the mask, the impurity is diffused until it reaches at least the lowest layer of the active layer, and electrodes are provided on the top surface of the straight part of the impurity non-diffusion region and the top surface of the curved part, and the impurity is non-diffused. A semiconductor device characterized in that the straight part of the area is a light emitting area of a semiconductor laser, the curved part is an optical waveguide, the tip of the curved part is a photodetector, and the semiconductor laser and the photodetector are optically connected. Production method.