JP2007329191A - Process for fabricating semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for fabricating a semiconductor laser in which the interface of a GaAs semiconductor region and an InGaAs semiconductor region can be made more steep. <P>SOLUTION: A GaAs region 37 is grown on a first group III-V compound semiconductor 35 at a substrate temperature in the range of 530-600°C. After growing a GaAs region 37a, temperature is altered to a range of 450-490°C without supplying a film deposition material. After altering that temperature, a GaAs thin film 37b is grown. Thereafter, a well layer 39 composed of a second group III-V compound semiconductor containing indium is grown on the GaAs thin film 37b using molecular beam epitaxy. The GaAs thin film 37b is thicker than the GaAs region 37a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor laser.

Non-Patent Document 1 describes an InGaAs / GaAs quantum well structure formed on a GaAs substrate. The full width at half maximum of the photoluminescence spectrum from a 6.4 nm thick In _0.42 Ga _0.58 As / GaAs single quantum well structure is 9.78 meV and 18.4 meV at 77 K and room temperature, respectively. The peak wavelength of this quantum well structure is 1.223 micrometers. From a quantum well structure grown at 400 degrees Celsius, a sharp spectrum can be obtained even if the indium composition is 0.4 or more. For this reason, the growth temperature is lowered from 550 degrees Celsius to 400 degrees Celsius during GaAs growth, and InGaAs is grown at 400 degrees Celsius without interrupting the growth. The change in temperature takes 3 minutes. The growth temperature of GaAs is different from the growth temperature of InGaAs semiconductors.
J. Appl. Phys. 78 (3) 1 August 1995, pp.1685-1688

  In order to obtain a practical InGaAs / GaAs quantum well structure, it is necessary to grow the InGaAs / GaAs quantum well structure at a temperature of 500 degrees Celsius or less. In the method described in Non-Patent Document 1, InGaAs is grown at 400 degrees Celsius after the growth temperature is lowered to 400 degrees Celsius during GaAs growth. In order to avoid interrupting the growth, a temperature change is performed during film formation. On the other hand, in order to improve the flatness of the GaAs semiconductor, it is preferable to form the GaAs semiconductor at about 580 degrees Celsius. When the method described in Non-Patent Document 1 is used, the film thickness of the GaAs semiconductor increases.

  The present invention has been made in view of such circumstances, and a method for manufacturing a semiconductor laser capable of improving the flatness of the interface between a GaAs semiconductor region and a III-V compound semiconductor containing In. The purpose is to provide.

  The invention according to one aspect of the present invention is a method for manufacturing a semiconductor laser. This method includes (a) a step of growing a GaAs region on a first III-V compound semiconductor at a substrate temperature in the range of 530 degrees Celsius to 600 degrees Celsius, and (b) an As layer after growing the GaAs region. Supplying a raw material and changing the temperature to a temperature in the range of 400 ° C. to 490 ° C., (c) growing the GaAs thin film after changing the temperature, and (d) using a molecular beam epitaxy method, And a step of growing a well layer made of a second III-V compound semiconductor containing indium on the GaAs thin film, wherein the thickness of the GaAs thin film is larger than the thickness of the GaAs region.

  In order to suppress the three-dimensional growth in the growth of the second III-V compound semiconductor containing indium, it is required to grow this semiconductor at a temperature of 500 degrees Celsius or less. On the other hand, the growth of the GaAs semiconductor is preferably performed at a temperature higher than the above temperature. This is because the flatness of the semiconductor film for the well layer is improved and the half width of the photoluminescence spectrum of the quantum well structure is narrowed. In addition, when the second III-V compound semiconductor is subsequently grown after the GaAs semiconductor is grown at a low temperature that matches the growth temperature of the second III-V compound semiconductor containing indium, excess arsenic is present in the GaAs semiconductor. Forming a non-luminescent center. For this reason, the intensity | strength of a photo-luminescence spectrum falls. Furthermore, when the second III-V compound semiconductor containing indium is grown on the GaAs semiconductor after the growth is interrupted and the temperature is changed, the intensity of the photoluminescence spectrum is lowered. However, in the method according to the present invention, after the GaAs region is grown at a high temperature, the temperature is changed to a temperature of 400 ° C. or more and 490 ° C. or less without forming a film, and a GaAs thin film is further grown. According to this, it is possible to avoid a decrease in the intensity of the photoluminescence spectrum.

  A method of manufacturing a semiconductor laser according to one aspect of the present invention includes: (e) a third III having a band gap wavelength smaller than the band gap wavelength of the second III-V compound semiconductor by using a molecular beam epitaxy method. A step of growing a barrier layer made of a -V compound semiconductor on the GaAs thin film can be provided. According to this method, not only a semiconductor laser having a single quantum well structure but also a semiconductor laser having a multiple quantum well structure is produced.

  In the method for manufacturing a semiconductor laser according to one aspect of the present invention, the thickness of the GaAs thin film is preferably 5 nm or more. If the thickness is less than 5 nm, the effect of changing the temperature to a temperature in the range of 400 to 490 degrees Celsius appears without forming a film. The thickness of the GaAs thin film is preferably 20 nm or less. When the thickness exceeds 20 nm, the flatness of the GaAs surface decreases.

  In the method for manufacturing a semiconductor laser according to one aspect of the present invention, the second III-V compound semiconductor is preferably InGaAs or GaInNAs.

  According to the method of the present invention, the half width of the photoluminescence spectrum is improved particularly in the InGaAs film and the GaInNAs film.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a method of manufacturing a semiconductor laser capable of improving the flatness of the interface between a GaAs semiconductor region and an InGaAs semiconductor region is provided.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, an embodiment relating to a method of manufacturing a semiconductor laser of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
1A, FIG. 1B, FIG. 1C, FIG. 2A, FIG. 2B, and FIG. 2C show a method for manufacturing a semiconductor laser according to this embodiment. It is drawing which shows the main processes.

  As shown in FIG. 1A, a substrate for crystal growth is prepared. This substrate is made of a III-V compound semiconductor, and can be, for example, a GaAs substrate 11. The GaAs substrate 11 is disposed in the crystal growth apparatus 13. The crystal growth apparatus 13 is a molecular beam epitaxy apparatus. Prior to crystal growth, thermal cleaning of the main surface 11a of the GaAs substrate 11 is performed. The temperature of the thermal cleaning is, for example, 580 degrees Celsius. The natural oxide film on the surface 11a of the GaAs substrate 11 is removed by thermal cleaning.

  As shown in FIG. 1B, a film forming material F 1 is supplied, and a GaAs region 15 is grown on the GaAs substrate 11 using a crystal growth apparatus 13. The GaAs region 15 is a film that covers the entire main surface 11 a of the GaAs substrate 11. The thickness of this GaAs film is, for example, 0.19 micrometers. The growth temperature T1 of the GaAs region 15 is preferably 530 degrees Celsius or higher. The growth temperature T1 is preferably 600 degrees or less.

  As shown in FIG. 1C, after the GaAs region 15 is grown, the substrate temperature in the crystal growth apparatus 13 is lowered from the growth temperature T1 to the temperature T2 without supplying a film forming material other than the arsenic material. The temperature T2 is a temperature suitable for the growth of the well layer. In the crystal growth apparatus 13, the substrate temperature is changed to a temperature of, for example, 490 degrees Celsius or less. Further, the substrate temperature is changed to a temperature of, for example, 400 degrees or more. The temperature T2 is preferably in the above temperature range. This temperature change is performed without breaking the vacuum in the reactor of the crystal growth apparatus 13.

  As shown in FIG. 2A, after the temperature change, the film forming raw material F2 is supplied to grow the GaAs thin film 17 at the temperature T2. The thickness of the GaAs thin film 17 is smaller than the thickness of the GaAs region 15. In the method for manufacturing a semiconductor laser, the thickness of the GaAs thin film 17 is preferably 5 nm or more. If the thickness is less than 5 nm, the effect of changing the temperature to a temperature in the range of 400 to 490 degrees Celsius appears without forming a film. The thickness of the GaAs thin film 17 is preferably 20 nm or less. When the thickness exceeds 20 nm, the flatness of the GaAs surface decreases. Preferably, the thickness of the GaAs thin film 17 is about 10 nm. As the growth interruption time, it takes time to start the temperature change and stabilize the temperature. The time to stability depends on the structure of the device and is preferably as short as possible.

  As shown in FIG. 2B, after the growth of the GaAs thin film 15, the film-forming raw material F3 is supplied to grow the second III-V compound semiconductor layer 19 containing indium. The film formation temperature of the second III-V compound semiconductor layer 19 is, for example, the temperature T2. The second III-V compound semiconductor layer 19 is, for example, InGaAs or GaInNAs. The second III-V compound semiconductor layer 19 functions as, for example, a well layer. The thickness of the second III-V compound semiconductor layer 19 is, for example, about 7 nm. A quantum well structure of a semiconductor laser using an InGaAs well layer is provided so as to realize an emission wavelength in a range of 1100 nm to 1150 nm, for example.

  As shown in FIG. 2C, after the growth of the second III-V compound semiconductor layer 19, the film forming raw material F4 is supplied to grow the GaAs film 21. The GaAs film 21 functions as a cap layer, for example. The thickness of the GaAs film 21 is, for example, 0.1 micrometers. The GaAs film 21 can be grown without changing the growth temperature of the second III-V compound semiconductor layer 19, and at a temperature higher than the growth temperature of the second III-V compound semiconductor layer 19. It can also grow. It is preferable to move from the growth of the second III-V compound semiconductor layer 19 to the growth of the GaAs film 21 without interrupting the growth.

  In order to suppress the three-dimensional growth in the growth of the second III-V compound semiconductor 19 containing indium, it is necessary to grow the semiconductor 19 at a temperature of 500 degrees Celsius or less. On the other hand, in order to improve the flatness of the semiconductor film 19 for the well layer and to narrow the half width of the photoluminescence spectrum of the quantum well structure, the growth of the GaAs semiconductor may be performed at a temperature higher than the above temperature. preferable. Further, after the GaAs semiconductor is grown at a low temperature that matches the growth temperature of the second III-V compound semiconductor (III-V compound semiconductor containing indium), the second III-V compound semiconductor is subsequently grown. Excess arsenic is incorporated into the GaAs semiconductor. Since these form non-luminescent centers, the intensity of the photoluminescence spectrum decreases. Furthermore, when the second III-V compound semiconductor containing indium is grown on the GaAs semiconductor after the growth is interrupted and the temperature is changed, the intensity of the photoluminescence spectrum is reduced. However, according to the method according to the present embodiment, after the GaAs region is grown at a high temperature, the temperature is changed to a temperature not lower than 450 degrees Celsius and not higher than 490 degrees without forming a film, and further the GaAs thin film 17 is grown. To do. According to this, it is possible to avoid a decrease in the intensity of the photoluminescence spectrum.

Example 1
Subsequently, some examples will be described. In any experimental example, thermal cleaning (580 degrees Celsius, 20 minutes) is performed prior to growth. The film forming speed is 1 μm / h. The photoluminescence wavelength is 1100 nm at room temperature. The flux strength of arsenic is 3.5 × 10 ⁻⁵ Torr.

Example 1:
GaAs growth 1: film thickness 0.1 μm, growth temperature, 470 degrees Celsius In _0.3 Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees GaAs growth 2: film thickness 0.1 μm, growth temperature 470 Degree Example 2:
GaAs growth 1: film thickness 0.1 μm, growth temperature, 530 ° C. growth interruption: temperature change from 530 ° C. to 470 ° C., 5 minutes In _0.3 Ga _0.7 As growth: film thickness 7 nm, growth temperature, Celsius 470 degree GaAs growth 2: film thickness 0.1 μm, growth temperature, 470 degrees Example 3:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 530 degrees Celsius Growth interruption: temperature change from 530 degrees to 470 degrees, GaAs growth 2: film thickness 0.01 μm, growth temperature, 470 degrees Celsius In _{0. 3} Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees GaAs growth 3: film thickness 0.02 μm, growth temperature, 470 degrees to 580 degrees GaAs growth 4: film thickness 0.08 μm, growth temperature, 580 centigrade Degree Example 4:
GaAs growth 2: film thickness 0.09 μm, growth temperature, 580 degrees Celsius Growth interruption: temperature change from 580 degrees to 470 degrees, GaAs growth 2: film thickness 0.01 μm, growth temperature, 470 degrees Celsius In _{0. 3} Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 ° GaAs growth 3: film thickness 0.02 μm, growth temperature 470 ° to 580 ° changing GaAs growth 4: film thickness 0.08 μm, growth temperature, 580 degrees Celsius Example 5:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 600 ° C. growth interruption: temperature change from 600 ° C. to 470 ° C., 5 minutes GaAs growth 2: film thickness 0.01 μm, growth temperature, 470 ° C. In _{0. 3} Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees GaAs growth 3: film thickness 0.02 μm, changing to growth temperature 470 degrees to 600 degrees GaAs growth 4: film thickness 0.08 μm, growth temperature, 600 degrees Celsius Example 6:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 580 degrees Celsius Growth interruption 1: temperature change from 580 degrees to 470 degrees, GaAs growth 2: film thickness 0.01 μm, growth temperature, 470 degrees Celsius In _{0 .3} Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees GaAs growth 3: film thickness 0.02 μm, growth temperature, 470 degrees growth interruption 2: temperature (Celsius) temperature change from 470 degrees to 580 degrees, GaAs growth for 5 minutes 4: film thickness 0.08 μm, growth temperature, 580 degrees Celsius Example 7:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 580 degrees Celsius growth interruption 1: temperature change from 580 degrees to 470 degrees, GaAs growth 2: film thickness 0.01 μm, growth temperature, 470 degrees Celsius In _{0 .3} Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees GaAs growth 3: film thickness 0.1 μm, growth temperature, 470 degrees Example 8:
GaAs growth 1: film thickness 0.1 μm, growth temperature, 470 degrees Celsius In _0.3 Ga _0.7 As growth: film thickness 7 nm, growth temperature, 470 degrees growth interruption: temperature change from 470 degrees to 530 degrees, 5 GaAs growth for 2 minutes: film thickness 0.1μm, growth temperature, 530 degrees Celsius

When the peak intensity and the half-value width of the photoluminescence of the sample produced by each of these experimental examples are obtained, the sample name is shown.
Example 1: 1 44
Example 2: Noise level Example 3: 1.1 35
Example 4: 1.6 23
Example 5: 0.8 25
Example 6: 1.35 21
Example 7: 1 30.4
Example 8: 0.5 69
It is. According to these experimental results, the half-value width is superior in Example 3, Example 4, Example 5, Example 6, and Example 7 as compared with Example 1. Further, when compared with the results of Example 1, the peak intensity is excellent in Examples 3, 4 and 6.

  In addition, when InGaAs was grown immediately without growing GaAs after the temperature was lowered after the growth of GaAs, the photoluminescence emission intensity was reduced to the noise level. This indicates that the growth interruption at the interface increases non-radiative recombination centers due to excessive arsenic and impurity pileup.

  Further, after growing GaAs at 580 degrees Celsius, if the growth temperature is lowered during the growth of GaAs without interrupting the growth (for example, the temperature is decreased to 470 degrees Celsius at a rate of 1 degree / second), the photoluminescence intensity becomes that of Example 1. Decreased to about 60 percent. If the temperature is changed without interrupting growth during GaAs growth, it takes about 3 minutes from the start of the temperature change to the temperature stabilization. At a growth rate of 1 μm / h, the temperature transition region has a thickness of 0.05 μm or more, so the effect of high-temperature growth is lost.

  After growing InGaAs, the growth temperature of the GaAs cap film may be the same as the growth temperature of InGaAs, or the temperature may be raised. For the same reason as the GaAs / InGaAs interface, it is better to avoid growing the GaAs and forming the InGaAs / GaAs interface after stopping the growth with the surface of the InGaAs exposed.

That is, after growing the GaAs region, changing to a temperature in the range of 400 to 490 degrees Celsius without supplying film forming materials other than As, growing the GaAs thin film after changing the temperature, A well layer (for example, InGaAs) is preferably grown on the GaAs thin film. FIG. 3 is a drawing showing the half width of the photoluminescence spectrum. FIG. 4 is a drawing showing the peak intensity of the photoluminescence spectrum.
GaAs growth temperature (Celsius) FWHM PL intensity (arbitrary unit)
Temp1: 470 60 1
Temp2: 530 35 1.3
Temp3: 580 18 1.6
Temp4: 600 25 0.8
It is.

  When the GaAs growth temperature is 500 degrees Celsius or higher, the half width of the PL spectrum is improved. Further, the surface of the GaAs film grown at 600 degrees Celsius was slightly cloudy. Accordingly, the GaAs growth temperature is preferably more than 500 degrees Celsius and 600 degrees or less. When the growth is interrupted at a low temperature, the full width at half maximum is wider than when the growth is not interrupted. However, if the growth temperature of GaAs is increased, the adverse effect of the growth interruption can be eliminated. It is preferable to grow GaAs at a substrate temperature in the range of 530 to 600 degrees Celsius. Referring to FIG. 4, as the growth temperature of GaAs is increased, the PL intensity tends to be improved although a decrease is observed at 600 degrees Celsius. Therefore, a temperature of 550 ° C. or higher is more preferable as the GaAs growth temperature, and a temperature of 580 ° C. or lower is preferable as the GaAs growth temperature.

When an InGaAsS quantum well (QW) was grown by changing the growth temperature and V / III ratio of InGaAs as follows, the PL intensity and the half width were as follows. Except for the InGaAs layer growth conditions, it is the same as Example 4, and the GaAs growth temperature is 580 degrees Celsius.
From Temp1 to Temp4, the As flux strength is 1 × 10 ⁻⁵ Torr,
Temp5 is 1 × 10 ⁻⁴ Torr and Temp6 is 1 × 10 ⁻⁵ Torr.
InGaAs growth temperature (Celsius) FWHM PL intensity (arbitrary unit)
Temp1: 440 25 7
Temp2: 430 23 1.7
Temp3: 420 22 0.8
Temp 4: 400 20 0.1
Temp5: 490 29 5
Temp6: 490 50 5.5
When the growth temperature is 420 ° C. or lower, the PL intensity required for practical use cannot be obtained. Further, in order to suppress three-dimensional growth, a higher As pressure is required as the temperature increases, but the flux strength necessary to obtain a half width of 30 meV or less at a growth temperature of 490 ° C. is 1 × 10 ⁻⁴ Torr. A flux strength higher than this is practically difficult in MBE growth, and the upper limit of the growth temperature is preferably 490 ° C. Therefore, in the case of InGaAs, the growth temperature is more preferably 420 ° C. to 490 ° C.

(Second Embodiment)
5A, FIG. 5B, FIG. 5C, FIG. 6A, FIG. 6B, and FIG. 6C show a method of manufacturing a semiconductor laser according to this embodiment. It is drawing which shows the main processes.

  Prepare a substrate for crystal growth. This substrate is made of a III-V compound semiconductor, and can be, for example, a GaAs substrate 31. The GaAs substrate 31 is disposed, for example, in the crystal growth apparatus 13.

As shown in FIG. 5A, a GaAs buffer layer is formed on the GaAs substrate 31. Silicon is added to the GaAs buffer layer 33, and the carrier concentration is 5 × 10 ¹⁷ cm ⁻³ . The thickness of the GaAs buffer layer 33 is, for example, 200 nm. Next, an n-type cladding layer 35 is formed on the GaAs buffer layer 33. The n-type cladding layer 35 is, for example, GaInP. Silicon is added to the n-type cladding layer 35, and the carrier concentration is 5 × 10 ¹⁷ cm ⁻³ . The n-type cladding layer 35 has a thickness of, for example, 1400 nm.

  As shown in FIG. 5B, a light guide layer 37 is formed on the n-type cladding layer 35. The light guide layer 37 is, for example, undoped GaAs. The thickness of the light guide layer 37 is, for example, 140 nm. Next, as shown in FIG. 5C, a well layer 39 is formed on the light guide layer 37. The well layer 39 is made of, for example, GaInNAs. The thickness of the well layer 39 is, for example, 10 nm. A growth flow is applied to the growth from the light guide layer 37 to the well layer 39 as in the first embodiment. That is, after growing the GaAs region 37a, the temperature is changed to a temperature in the range of 400 ° C. or more and 490 ° C. or less without supplying a film forming material, and after changing the temperature, the GaAs thin film 37b is changed from 530 ° C. to 600 ° C. The well layer (GaInNAs in this embodiment) is grown on the GaAs thin film 37b. In this case, the light guide layer 37 is composed of a GaAs region 37a and a GaAs thin film 37b. The step of forming the light guide layer 37 includes the step of growing the GaAs region 37a, and the temperature is lowered after this step to grow the GaAs thin film 37b. Including the step of. In a specific example, the growth temperature of the GaAs region 37a for the light guide layer is, for example, 580 degrees Celsius. The growth is interrupted for about 5 minutes, and the temperature is lowered from 580 degrees Celsius to 440 degrees Celsius. At 440 degrees Celsius, a 10 nm thick GaAs thin film 37 b and a 10 nm thick GaInNAs well layer are grown on the thin film 37 b. The nitrogen raw material is produced using a radical gun.

  As shown in FIG. 6A, after the well layer 39 is grown, the barrier layer 41 is grown using the molecular beam epitaxy method. The barrier layer 41 is made of a III-V compound semiconductor having a band gap wavelength smaller than that of the III-V compound semiconductor for the well layer, and is, for example, an undoped GaAs semiconductor. The thickness of the barrier layer 41 is, for example, 10 nm. By repeating the well layer growth and the barrier layer growth a desired number of times, not only a single quantum well structure semiconductor laser but also a multiple quantum well structure semiconductor laser can be produced. In this embodiment, as shown in FIG. 6B, a well layer 43 is grown on the barrier layer 41. The well layer 43 is made of, for example, GaInNAs. The thickness of the well layer 43 is, for example, 10 nm.

After the well layer 43 is grown, the light guide layer 45 is grown as shown in FIG. Thereafter, a p-type cladding layer 47 and a contact layer 49 are sequentially formed. The light guide layer 45 is, for example, undoped GaAs and has a thickness of 140 nm, for example. The p-type cladding layer 47 is, for example, GaInP. Zinc is added to the p-type cladding layer 47, and the carrier concentration is 7 × 10 ¹⁷ cm ⁻³ . The thickness of the p-type cladding layer 47 is 1400 nm, for example. The contact layer 49 is patterned. The p-type contact layer 49 is, for example, GaAs. Zinc is added to the p-type contact layer 49, and the carrier concentration is 2 × 10 ¹⁸ cm ⁻³ . The thickness of the p-type contact layer 49 is, for example, 200 nm. An anode electrode 53 is formed on the insulating film 51 such as silicon oxide, and a cathode electrode 55 is formed on the back surface of the substrate 31. With these steps, the main steps of the method for fabricating a semiconductor laser have been described.

(Example 2)
Experimental samples were prepared using several growth conditions. All As pressures are 3 × 10 ⁻⁵ Torr.
Example 9:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 580 degrees Celsius growth interruption 1: temperature change from 580 degrees to 465 degrees, GaAs growth 2: film thickness 0.01 μm, growth temperature, 465 degrees In _{0. 3} Ga _0.7 N _0.05 As _0.95 growth: film thickness 7 nm, growth temperature, 465 ° GaAs growth 3: film thickness 0.02 μm, growth temperature 465 ° -600 ° C. Temperature change GaAs growth 4: film thickness 0 0.08 μm, growth temperature, 600 degrees Example 10:
GaAs growth 1: film thickness 0.1 μm, growth temperature, 465 degrees Celsius In _0.3 Ga _0.7 N _0.05 As _0.95 growth: film thickness 7 nm, growth temperature 465 degrees GaAs growth 2: film thickness 0. 02 μm, growth temperature 465 degrees Growth interruption: temperature change from 465 degrees to 530 degrees, GaAs growth for 2 minutes and 50 seconds 3: film thickness 0.1 μm, growth temperature 600 degrees

Annealing was performed at RTA 750 ° C. for 30 seconds. The N composition was 0.5% and the wavelength was 1150 nm. The peak intensity and the half-value width of the photoluminescence of the sample produced by each of these experimental examples are obtained.
Sample name Peak intensity (arbitrary unit) Half width (unit: meV)
Example 9: 0.24 40
Example 10: 0.250
It is. According to these experimental results, compared to Example 10, the full width at half maximum and the peak intensity are superior in Example 9.

  Separately from these examples, sample A was grown at 480 degrees Celsius for all of the GaAs regions that form the base of the well layer, and a portion of the GaAs regions that serve as the foundation of the well layers was grown at 580 degrees, and then the growth was interrupted. Sample B on which a GaAs thin film was grown at a lowered temperature of 470 degrees Celsius was prepared. These samples A and B are annealed. Annealing was performed using the RTA method under conditions of 750 degrees Celsius and 15 seconds. The half width of sample A is 60 meV, and the half width of sample B is 45 meV. Therefore, the order of the steps of high temperature growth of GaAs, temperature drop during growth interruption, low temperature growth of GaAs, and well layer growth is preferable for forming the quantum well structure.

  A quantum well structure of a semiconductor laser using a GaInNAs well layer is provided so as to realize an emission wavelength in a range of 1150 nm to 1350 nm, for example. The indium composition is, for example, 28% to 35%, and the nitrogen composition is, for example, about 0.5% to 2%.

Example 3
Experimental samples were prepared using several growth conditions. All As pressures are 1 × 10 ⁻⁵ Torr. The growth temperature is changed from Temp1 to Temp4.
Example 9:
GaAs growth 1: film thickness 0.09 μm, growth temperature, 580 ° C. growth interruption 1: temperature change from 580 ° C. to growth temperature Tg, GaAs growth 2: film thickness 0.01 μm, growth temperature, Tg
In _0.3 Ga _0.7 N _0.1 As _0.9 growth: film thickness 7 nm, growth temperature, Tg degree GaAs growth 3: film thickness 0.02 μm, temperature change from growth temperature Tg degree to 600 degree GaAs growth 4 : Film thickness 0.08 μm, growth temperature, 600 degrees.
GaInNAs growth temperature (Celsius) FWHM PL intensity (arbitrary unit)
Temp1: 410 35 0.13
Temp2: 420 35 0/36
Temp3: 428 40 0.4
Temp 4: 435 50 0.1
Annealing was performed at RTA 750 ° C. for 30 seconds. The N composition was 1% and the wavelength was 1250 nm.

Thus, under the conditions of N = 1% and As pressure 1 × 10 ⁻⁵ Torr, the growth temperature is desirably 420 ° C. to 430 ° C. GaInNAs differs in optimum growth temperature and annealing temperature depending on the N composition and As pressure, but the PL strength is significantly lowered at 400 ° C. or lower, and it is difficult to suppress three-dimensional growth at 490 ° C. or higher even if the As pressure is increased. A growth temperature range of 400 ° C. to 490 ° C. is suitable. In order to obtain a half width and PL strength necessary for practical use, 400 ° C. to 470 ° C. is more preferable.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1A, FIG. 1B, and FIG. 1C are drawings showing main steps of a method of manufacturing a semiconductor laser according to the first embodiment. 2A, 2B, and 2C are drawings showing main steps of the method of manufacturing the semiconductor laser according to the first embodiment. FIG. 3 is a drawing showing the half width of the photoluminescence spectrum. FIG. 4 is a drawing showing the peak intensity of the photoluminescence spectrum. FIG. 5A, FIG. 5B, and FIG. 5C are drawings showing main steps of the method of manufacturing the semiconductor laser according to the first embodiment. 6A, 6B, and 6C are drawings showing main steps of the method of manufacturing the semiconductor laser according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... GaAs substrate, 13 ... Crystal growth apparatus, F1, F2, F3, F4 ... Film-forming raw material, 15 ... GaAs area | region, 17 ... GaAs thin film, 19 ... 2nd III-V compound semiconductor layer, 21 ... GaAs film | membrane, 31 ... GaAs substrate, 33 ... GaAs buffer layer, 35 ... n-type cladding layer, 37 ... light guide layer, 39 ... well layer, 37a ... GaAs region, 37b ... GaAs thin film, 41 ... barrier layer, 43 ... well layer, 47 ... p-type cladding layer, 49 ... contact layer, 51 ... insulating film, 53 ... anode electrode, 55 ... cathode electrode

Claims (4)

A method for fabricating a semiconductor laser, comprising:
Growing a GaAs region on the first III-V compound semiconductor at a substrate temperature in the range of 530 to 600 degrees Celsius;
After growing the GaAs region, supplying an As raw material and changing the temperature to a range of 400 to 490 degrees Celsius;
Growing the GaAs thin film after changing the temperature;
Growing a well layer made of a second III-V compound semiconductor containing indium on the GaAs thin film using molecular beam epitaxy;
With
The thickness of the GaAs thin film is smaller than the thickness of the GaAs region.   Using a molecular beam epitaxy method to grow a barrier layer made of a third III-V compound semiconductor having a band gap wavelength smaller than that of the second III-V compound semiconductor on the GaAs thin film; The method of claim 1, further comprising: The thickness of the GaAs thin film is 5 nm or more,
The method according to claim 1, wherein the GaAs thin film has a thickness of 20 nm or less. 4. The method according to claim 1, 2 or 3, wherein the second III-V compound semiconductor is InGaAs or GaInNAs.

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