JP3615453B2 - Crystal growth apparatus and method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a crystal growth apparatus and method, for example, a crystal growth apparatus and method suitable for crystal growth for a multiwavelength surface emitting laser array.
[0002]
[Prior art]
The prior art will be described by taking a crystal for a multi-wavelength surface emitting laser array as an example.
[0003]
Since it is a structure that emits light from the surface emitting laser substrate surface, it is easy to form a two-dimensional array, and since it has a low emission angle, it has good characteristics such as good connectivity with fibers.
[0004]
Today, there is a demand for wavelength multiplexing systems that transmit at a plurality of wavelengths due to an increase in capacity of optical communication. Since surface emitting lasers can be easily arrayed at high density, if an array element in which a plurality of elements having different oscillation wavelengths are locally integrated is realized, it is considered promising as a light source for a wavelength multiplexing system.
[0005]
Conventional multi-wavelength surface emitting laser arrays are: (1) manufactured by using the difference in growth rate within the wafer surface, which is a feature of the crystal growth apparatus, and (2) a pattern prepared in advance on the wafer. There are reports on the difference in the growth rate and the difference in the growth rate, and (3) the difference in the growth rate and growth film desorption rate due to the temperature difference of the substrate.
[0006]
It is impossible to fabricate locally using the wafer distribution in (1), and (2) and (3) require a processing process on the wafer before growth, so yield and reliability There is a problem with sex.
[0007]
In a normal molecular beam epitaxial growth method (MBE), a shielding plate is used to control the growth rate. However, this technology is not designed for the film thickness distribution in the micro area, and even if a shielding plate is placed near the wafer, the diffusion on the surface of the molecule is small, so the film thickness distribution is controlled in the micro area. For this purpose, it is necessary to move the shielding plate finely, which is technically difficult, and the amount of molecular beam is changed by changing the evaporation amount of the raw material, which takes time.
[0008]
[Problems to be solved by the invention]
The present invention can locally distribute the film thickness within the wafer surface in a short time during the growth without requiring a processing process. For example, a multi-wavelength surface emitting laser with good position and film thickness controllability. It is an object of the present invention to provide a crystal growth apparatus and method capable of manufacturing an array.
[0009]
[Means for Solving the Problems]
The present invention relates to a compound semiconductor crystal growth apparatus according to a metal organic vapor phase epitaxy method or a gas source MBE method using an organic metal, and has a slit-like opening, and the opening grows a crystal during crystal growth. The compound semiconductor crystal growth apparatus is characterized in that a shielding plate that is movable in the crystal growth plane of the plate is disposed between the crystal growth raw material supply unit and the substrate.
[0010]
Here, the shielding plate is arranged two openings of the two shielding plates are opened in the same direction, the two shielding plates in the opposite direction in the crystal growth surface of the substrate It is preferable to be movable.
[0011]
Further, it is preferable that a plurality of the openings are provided in one direction.
The present invention relates to a compound semiconductor crystal growth apparatus according to an organic metal vapor phase growth method or a gas source MBE method using an organic metal.
A crystal growth method characterized in that a film thickness of a crystal to be grown is locally changed in the crystal growth plane by moving a shielding plate having an opening in the crystal growth plane of the substrate.
[0012]
Here, it is preferable that the opening width is continuously changed by moving two shielding plates having openings in opposite directions.
[0013]
Further, it is preferable to adjust the film thickness by changing the speed of moving the shielding plate.
[0014]
Furthermore, it is preferable to adjust the film thickness by changing the supply amount of the raw material depending on the location of the opening when moving the shielding plate having the opening.
[0015]
The distance between the shielding plate and the growth surface is preferably 1 cm or less.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
A first embodiment of the present invention will be described. FIG. 1 shows the configuration of a surface emitting laser. An n- AlGaInAs having a low refractive index λ / 4 (λ = 1550 nm) and an optical length λ having a high refractive index, with an AlGaInAs intermediate layer 10 nm in the middle sandwiched on an n-type InP (100) substrate 1. / 4 n-AlGaInAs 50.5 pair n-type DBR2 is grown, and then an AlGaInAs spacer layer 3 including an active layer having an optical length λ is grown, and then a 1 nm-thick modulation layer is formed in the wafer. Changed and grew.
[0017]
FIG. 2 shows a process when the modulation layer 4 is grown. The wafer 21 is mounted downward on the susceptor 22, and when the modulation layer 4 is grown, the shielding plate 24 having the opening 23 is separated from the wafer 21 by 50 μm and the crystal material supply unit 25 and the wafer 21 (substrate on which crystals are grown). And placed between. While the opening 23 having a width of 10 μm moved 2 mm for 20 seconds, the total flow rate of the raw material containing Ga, Al, and In was repeatedly and linearly changed from 10 sccm to 100 sccm, and continuously from 100 sccm to 10 sccm while moving 2 mm.
[0018]
After growing by moving the opening 23 over the entire wafer 21, the wafer 21 was rotated by 90 °, and this time, the operation of flowing 20 sccm of raw material and the operation of stopping were repeated while moving 1 mm in 20 seconds. After growing by moving the opening 23 over the entire wafer 21, the shielding plate 24 was moved away from the vicinity of the surface of the wafer 21 to return to the normal growth state.
[0019]
Subsequently, 40 pairs of p-AlGaInAs having a low refractive index optical length λ / 4 and p-AlGaInAs having a high refractive index optical length λ / 4 are sandwiched on the entire wafer 21 by sandwiching an AlGaInAs intermediate layer 10 nm having a gradient composition in the middle. A type DBR4 was grown.
[0020]
FIG. 3 shows a reflection spectrum of the surface emitting laser. As shown here, it can be seen that by changing the thickness 1 of the modulation layer, the portion of the reflectivity drop corresponding to the oscillation wavelength, that is, the resonance wavelength changes.
[0021]
FIG. 4 shows the thickness 1 of the modulation layer 4 and the oscillation wavelength. By changing the film thickness 1 within the array, it is possible to produce a multi-wavelength surface emitting laser array having oscillation wavelengths at equal intervals.
[0022]
Next, a ring electrode made of AuZnNi is produced on the surface of the wafer 21, a mesa is produced with a diameter of 10 μmφ, the surface is protected with SiNx, a wiring electrode made of Cr / Au on the upper side, and an electrode made of AuGeNi on the lower side Formed.
[0023]
FIG. 5 shows a schematic diagram of a manufactured multi-wavelength surface emitting laser array of 2 × 5 elements with an interval of 250 μm and the oscillation wavelength of the manufactured element. It can be seen that 1542 nm to 1560 nm are arranged with good control at intervals of 2 nm.
[0024]
FIG. 6 shows the optical output with respect to the injection current of the fabricated array element. It was found that all 10 elements had the same good threshold current and light output.
[0025]
Embodiment 2
A second embodiment of the present invention will be described. It is the structure of the surface emitting laser similar to FIG.
[0026]
Low-refractive-index optical length λ / 4 (λ = 1550 nm) p-AlGaInAs and high-refractive-index optical length on a p-type InP (311) B substrate 1 with an AlGaInAs intermediate layer 10 nm having a gradient composition in between. After growing 50.5 pairs of p-type DBR 2 of λ / 4 p-AlGaInAs, an AlGaInAs spacer layer 3 including an active layer of optical length λ is grown, and then a modulation layer 4 having a thickness of 1 nm is formed in the wafer. Grow with varying thickness.
[0027]
FIG. 7 shows a process when the modulation layer 4 is grown. The wafer 21 is mounted downward on the susceptor 22, and a shielding device in which two shielding plates 24 a and 24 b having repeated opening portions with a width of 2 mm are overlapped at a spacing of 2 mm when the modulation layer 4 is grown is placed 50 μm away from the wafer 21. did.
[0028]
The actual width of the opening, which is changed by moving the two shielding plates 24a and 24b in opposite directions, was changed from 0 mm to 2 mm in 20 seconds while the raw material was supplied at 100 sccm.
[0029]
Thereafter, the wafer 21 was rotated by 90 °, and the opening formed by the two shielding plates 24a and 24b was changed from 0 mm to 2 mm in 20 seconds while flowing the raw material at 10 sccm.
[0030]
After the shielding plates 24a and 24b are separated from the vicinity of the wafer surface and returned to the normal growth state, the n− of the low refractive index optical length λ / 4 with the intermediate layer of the AlGaInAs intermediate layer 10 nm having the gradient composition sandwiched between the entire wafer. A 40-pair n-type DBR4 of AlGaInAs and n-AlGaInAs having a high refractive index and an optical length of λ / 4 was grown.
[0031]
Next, a ring electrode made of AuGeNi is produced on the wafer surface, a mesa is produced with a diameter of 10 μmφ, the surface is protected with SiNx, and a wiring electrode made of Cr / Au is formed on the upper side and an electrode made of AuZuNi is formed on the lower side did.
[0032]
FIG. 8 is a top view of the manufactured multi-wavelength surface emitting laser array of 5 × 5 elements with an interval of 250 μm, and shows the oscillation wavelength of the manufactured elements at the same time. It can be seen that 1535 nm to 1559 nm are arranged with good control at 1 nm intervals. It was found that all 25 elements had good threshold current and light output as in Example 1.
[0033]
Embodiment Example 3
In the above embodiment example, the metal organic vapor phase epitaxy is performed. However, the same method can be applied to a gas source MBE using an organic metal having a large diffusion on the surface.
[0034]
FIG. 9 is a front view showing the gas source MBE, where (a) shows a state during normal growth, and (b) shows a state where a shielding plate is introduced.
[0035]
The ejection cells 81 a and 81 b are crystal raw material supply units, and movable shielding plates 24 a and 24 b are arranged between the ejection ports of the ejection cells 81 a and 81 b and the wafer 21.
[0036]
Also in this apparatus, as in Embodiment 2, it is possible to locally distribute the film thickness within the wafer surface in a short time during the growth.
[0037]
In addition to the above-described embodiments, the present invention can be modified in various ways as follows.
[0038]
For example, the material system is not limited to AlGaInAs but can be applied to AlGaAs, GaInAsP, GaAlInAsSb, and AlGaInN systems. Furthermore, the film thickness modulation technique at the time of crystal growth by this method is not limited to the surface emitting laser, but can be applied to other optical and electronic devices. In addition, by changing the moving direction using a plurality of shielding plates, a two-dimensional film thickness distribution can be formed each time without rotating and changing the direction of the wafer. Further, by simultaneously rotating the shielding plate and the wafer, the influence of the film thickness distribution in the direction in which the raw material flows can be reduced. Furthermore, the growth without the influence of shielding becomes possible by increasing the distance between the wafer shielding plates.
[0039]
【The invention's effect】
According to the present invention, it is possible to locally distribute the film thickness within the wafer surface in a short time during the growth without requiring a processing process.
Therefore, for example, a multiwavelength surface emitting laser array can be fabricated with good controllability of position and film thickness. In addition, for example, it is possible to realize a multi-wavelength surface emitting laser array having good characteristics such as element characteristics and element lifetime, in which the elements in the array correspond to the oscillation wavelength with good control.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional view showing a configuration of a surface emitting laser.
FIG. 2 is a diagram for explaining the growth of a modulation layer.
FIG. 3 is a graph showing a reflection spectrum of a surface emitting laser structure.
FIG. 4 is a graph showing the relationship between the thickness of a modulation layer and the oscillation wavelength.
FIG. 5 is a perspective view of a 2 × 5 multiwavelength surface emitting laser array.
FIG. 6 is a graph showing injection current versus light output.
FIG. 7 is a diagram for explaining the growth of a modulation layer.
FIG. 8 is a plan view of a 5 × 5 multiwavelength surface emitting laser array.
FIG. 9 is a conceptual front view of an MBE device.
[Explanation of symbols]
1 group plate <br/> 2 DBR layer,
3 Spacer layer,
4 modulation layer,
5 DBR layer,
21 wafers,
22 Susceptor,
23 opening,
24 shielding plate,
24a, 24b shielding plate,
25 Crystal raw material supply section,
81a, 81b Raw material supply unit.

Claims (7)

In a compound semiconductor crystal growth apparatus according to an organic metal vapor phase growth method or a gas source MBE method using an organic metal,
It has a slit-shaped opening, a shield plate which is movable in a crystal growth surface of the board growing crystals the opening during the crystal growth, between the crystal-growing raw material supply unit and the substrate A compound semiconductor crystal growth apparatus characterized by being arranged. The shielding plate is arranged two openings of the two shielding plates are opened in the same direction, the two shielding plates are movable in opposite directions in the crystal growth surface of the substrate The crystal growth apparatus according to claim 1. The crystal growth apparatus according to claim 1, wherein a plurality of the openings are provided in one direction. In a compound semiconductor crystal growth apparatus according to an organic metal vapor phase growth method or a gas source MBE method using an organic metal,
A compound semiconductor crystal growth method characterized in that a film thickness of a crystal to be grown is locally changed in the crystal growth plane by moving a shielding plate having an opening in the crystal growth plane of the substrate. 5. The crystal growth method according to claim 4, wherein the opening width is continuously changed by moving two shielding plates having openings in opposite directions. 6. The crystal growth method according to claim 4, wherein the film thickness is adjusted by changing a moving speed of the shielding plate. The crystal growth method according to any one of claims 4 to 6, wherein when the shielding plate having the opening is moved, the film thickness is adjusted by changing the supply amount of the raw material depending on the position of the opening.

Images