JPS61131582A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To form a high-luminous output and short-wavelength semiconductor laser without increasing the series resistance by making an impurity diffuse in the clad layer in such a way that the carrier density in the vicinity of the active layer becomes smaller. CONSTITUTION:The temperature of the substrate is made to rise for about 20hr up to reach 70 deg.C, then Al and Ga are respectively irradiated at 1,100 deg.C and 950 deg.C for forming the N type clad layer. At this time, Sn is diffused first as an impurity at 850 deg.C at the same time as the time the Al and Ga are irradiated. In such the state, the irradiation of Al and Ga is performed and when the prescribed time, when is required by the time the N type clad layer is formed and reaches the vicinity of the active layer, elapses to the clad layer to be formed, the first diffusion temperature of Sn is lowered to 750 deg.C. In this state, the impurity Sn is diffused throughout the prescribed time to be required by the time the N type clad layer is formed. When the N type clad layer is formed, the GaAs active layer is formed. Then, the P type clad layer is formed. In this case, Be is diffused as an impurity at temperatures of 800 deg.C or thereabouts. Furthermore, the gap layer is formed. In this case, the temperature for the formation of the gap layer is set at 850 deg.C, though the impurity Be keeps being diffused.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor laser.

[Prior art]

Semiconductor radars using semiconductors as materials have the advantages of being ultra-small, commercially viable, easy to change, and inexpensive, so they are used in many fields such as optical communications and optical information processing. .

FIG. 3 shows a schematic diagram of a double heterostructure semiconductor laser. The semiconductor laser has an N-type (or P-type) cladding layer 12 . An active layer 16 and a P-type (or N-type) cladding layer 13 are sequentially formed, and electrodes 14 and 15 are provided so that current flows in the forward direction between the electrodes 14 and 15. When applied, both kraft layers 12.13
Stimulated emission of light occurs in the active layer 16 sandwiched between
While the light is reflected between the mirror surfaces 17 and 18 due to the cleavage, only the light that satisfies the conditions of resonance is emitted.

Various methods for manufacturing semiconductor lasers (epitaxial growth methods) have been put into practical use, such as liquid phase growth and vapor phase growth. The MBE method, which epitaxially grows crystals by irradiation, is attracting attention because it is suitable for growing four multilayer films.

[Problem that the invention seeks to solve]

To explain the case of fabricating a semiconductor laser by epitaxially growing a crystal on an N-type GaAs substrate using the Meε method (normally, semiconductor lasers are treated as N-type based on consideration of integration with photodetectors, etc.). Sn is used as an N-type dopant (donor), and when forming an N-type clad layer on a substrate, Sn is added to the clad layer.
n is thermally diffused. This means that the Sn cell temperature is 700
~900 degrees, and at this temperature the carrier density is 5
This is because the required carry)' density is reduced by iη.

Next, FIG. 4 shows the results obtained by the present inventor regarding the cell temperature of toner Sn and the light emission output of 9 light emission wavelengths.

Figure 4 shows that when forming a cladding layer and an active layer on an N-type GaAs substrate to fabricate a semiconductor laser, the diffusion temperature of the impurity Sn was set to 750°C and
Table 1 shows the emission output and emission wavelength of the manufactured semiconductor laser at 800°C and 850°C.
In this case, the diffusion of the impurity (using Be) during the formation of the P-shaped rad layer, which is the other cladding layer, always causes the carrier density to be lXl018C1
As is clear from the diagram 0, which is set to 1-3, as the diffusion temperature of the impurity Sn increases, the emission output of the semiconductor laser decreases and the output wavelength shifts to the longer wavelength side. Examining the carrier density at each diffusion temperature of the impurity Sn, we find that at a diffusion temperature of 750°C, it is 1XIQ17cn-3, at 800°C, it is 3"1017cll-', and at 850°C, it is 6XIO17
ell=, and the carrier density increases as the diffusion temperature increases. In other words, as the carrier density increases, the emission output of the semiconductor laser decreases, and the output wavelength shifts to the higher wavelength side. Therefore, if the carrier density in the N-type cladding layer is set to LXIO17am-' or less, high output and short wavelength light can be obtained, but when the carrier density decreases, the series resistance as a semiconductor laser increases.

Usually, it is desirable that the series resistance is 15Ω or less.

[Means for solving problems]

FIG. 5 shows the light emission output and series resistance in the N-type layer and layer. The horizontal axis in FIG. 5 indicates the distance from the active layer in the N-shaped rad layer, and the distance from the active layer is 0. Within IIIm, the light emission output drops significantly, but the series resistance hardly changes during this period. In other words, in the vicinity of the active layer in the N-shaped rad layer, it is thought that carriers enter the active layer, causing negative effects such as a decrease in light emission output.
Regarding the series resistance, there is almost no effect of carrier movement in the vicinity of the active layer.

The present invention has been made based on this knowledge, and an object of the present invention is to provide a method for manufacturing a semiconductor laser that can reduce series resistance and achieve high light output.

The present invention uses the MBE method, which uses molecular beams to epitaxially grow crystals on a substrate, to produce a semiconductor laser having a structure in which an active layer is sandwiched between cladding layers. It is characterized by being diffused into the cladding layer.

〔Example〕

FIG. 1 is a schematic diagram of the apparatus used to carry out the method of the invention. In the figure, reference numeral 20 denotes a molecular beam epitaxy apparatus, the inside of which is kept in a high vacuum state by an ultra-high vacuum evacuation apparatus (not shown), and a substrate holding plate 21 is provided approximately in the middle of the molecular beam epitaxy apparatus ff120. , the substrate holding plate 2
1 holds the substrate 11.

A shutter 22 is arranged below the substrate 11 held on the substrate holding plate 21, and further below that, a plurality of evaporation source cells 23, 23, . . . covered with a liquid nitrogen cooling system are arranged. There is. Each evaporation source cell 23 injects a molecular beam having thermal energy such as Ga or ^s+sn. A shutter 24 is arranged between each evaporation source cell 23 and the shutter 22 to block molecular beams emitted from each evaporation source cell 23, respectively.

In addition, an ion sputter gun 25, an electron a 26, an Auger electron analysis system 27, a quadrupole mass spectrometer 28, and the like are arranged.

30 is a control device, into which the detection results of the quadrupole mass spectrometer 28 are input, and the output of the control word 230 is sent to a cell temperature control system that controls the temperature of the shutters 22, 24 and each evaporation source cell 23. It is given to 31.

Normally, when the amount of sample in the cell 23 changes, the evaporation area changes, and the amount of molecular beam emission changes accordingly. Therefore, in order to control the emission amount, the ion current is monitored by the quadrupole mass spectrometer 28 and this information is input to the control device 30, and the control value Va, 30 is determined based on the temperature of each cell 23. A predetermined signal is output to the cell temperature control system 31.

In addition, the control device 30 is configured to control each shutter based on a predetermined time chart to form a predetermined cladding layer and active layer, and to control the temperature of each cell in the impurity to change its diffusion temperature. It becomes.

Now, an N-type GaAs substrate is irradiated with Ga, 8N, and As to form a cladding layer and an active layer, and N as a dopant.
FIG. 2 shows a time chart for manufacturing a semiconductor laser by diffusing irradiation of Sn to the cladding layer and irradiation of [le to the P-shaped cladding layer. In this case, first, the substrate temperature was raised to 700°C for about 20 hours, and then An was heated to 1100°C and Ga was heated to 95°C to form an N-type cladding layer.
The irradiation is carried out at 0°C, and at the same time as the irradiation of 8j1 and Ga, Sn is first diffused as an impurity at 850"c. In this state, the irradiation is carried out for a predetermined period of time (approximately 25 hours), and the N-type cladding layer is For a predetermined time until the thickness reaches a predetermined thickness, that is, for an N-type cladding layer to be formed,
After a predetermined time has elapsed for the N-type cladding layer to reach the vicinity of the active layer, the diffusion temperature of the Sn impurity is lowered to 750° C., and in this state Sn is diffused for a predetermined time until the N-type cladding layer is formed. .

When the N-type cladding layer is formed, the shutter for Al and the shutter for Sn are closed to stop irradiation of Al and Sn in order to form a GaAs active layer.

This state is continued for a predetermined time (5 hours) to form an active layer of a predetermined thickness.

When the active layer is formed, the shutter related to ^l is opened to form a P-shaped rad layer, but in this case, the shutter related to Be is newly opened and Be is used as an impurity at a temperature of about 800°C. Spread. Irradiation is carried out for a predetermined period of time (approximately 20 hours) in this state, and when a P-shaped rad layer of a predetermined thickness is formed, the shutter related to Ajl is then closed and a cap layer is formed. do. In this case, the impurity Be continues to be diffused at a temperature of 850°C.

Formation of the cap layer takes about 20 hours.

As is continuously irradiated from the start of the work (the start of raising the temperature of the substrate) until the end of the work.

Through such a process, a semiconductor laser with high light output, short wavelength, and low series resistance is manufactured.

〔effect〕

According to the present invention, since the carrier 8 degree is made small in the portion near the active layer where the series resistance hardly changes, a semiconductor laser with high light emission output and short wavelength can be manufactured without increasing the series resistance.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the equipment used to carry out the method of the present invention, Figure 2 is a time chart for explaining the operation of the equipment, Figure 3 is a schematic diagram of a semiconductor radar, and Figure 4 is the impurity diffusion temperature. FIG. 5 is a graph showing the relationship between the distance from the active layer in the kraft layer, the light emitting output, and the series resistance. 11...Substrate 12.13...Clad layer 14.
DESCRIPTION OF SYMBOLS 15... Electrode 16... Active layer 20... Molecular beam lithography device 21... Substrate holding plate 22.24...
・Shutter 23...Evaporation source cell 30...Control device patent Applicant: Sanyo Electric Co., Ltd. Agent Patent attorney: Noboru Kono No. 3 Figure length: No. 512] Moxibustion em> Figure 4 Procedure? Di stop climbing (spontaneous) 1. Description of the case 1982 Patent Application No. 254701 2, title of the invention “Ii conductor laser manufacturing method, person making the amendment Relationship to the case Patent applicant location 2-18 Keihan Hondori, Moriguchi City Name (
188) Sanyo Electric Co., Ltd. Representative Ue Ie 4, Agent Address ■543 1-14 Shitennoji, Tennoji-ku, Osaka City
No. 22 "Claims", "Details of the Invention 6, Contents of Amendment 6-1""Scope of Claims" as per the attached sheet 6-2 "Detailed Description of the Invention" in the specification of Nisshin Building No. 207 ``In a high vacuum'' on page 2, line 14 of the specification is corrected to ``in an ultra-high vacuum''. (2) On page 2, line 17 of the book M, the word “thin film” was replaced with “
"Thin film," he corrected. (3) On page 3, line 6 of the Book of Light, the phrase ``by thermal diffusion'' is corrected to ``dope.'' (4) On page 3, line 15 of the specification, "diffusion temperature" is corrected to "cell temperature." (5) In the 20th line of page 3 of Akira 5ur-, the phrase ``diffusion is'' is corrected to ``the cell temperature is''. (6) Page 4, line 2, lines 4 to 5 of Ming M,
In the 6th and 8th lines, the words "diffusion temperature" are corrected to "cell temperature." (7) On page 5, line 17 of the specification, the word "diffuse" is corrected to "dope." (8) On page 6, line 3 of the specification, the phrase "r high vacuum state" is corrected to "ultra high vacuum state." (9) ``Form an active layer and change the diffusion temperature'' on page 7, line IO to line 111 of Akira ms.
"It forms an active layer and controls the temperature of each impurity cell." On page 7, line 16 of the specification, the phrase "diffuse irradiation" is corrected to "dope." (11) On page 7, line 18 of the specification, the phrase "heated for about 20 hours" is corrected to "heated for about 20 minutes." (12) Book M, page 8, lines 1 to 2, line 9, 1
In each line 88, "diffusion" is corrected to "dope." (13) “(About 25 hours)” on page 8, line 2 of the Meiji M.
Correct the statement to "(about 25 minutes)". (14) Ming 1 [? In page 8, line 7 of F, the phrase "diffusion temperature" is corrected to "cell temperature." (15) Ming I [Book I, page 8, line 13: “(5 hours)”
Correct the statement to "(5 minutes)". (16) “(approximately 20 hours)” on page 8, line 19 of the specification
Correct the statement to "(approximately 20 minutes) °". (17) In the second and third lines of page 9 of the specification, the words "diffused" are corrected to "doped." (18) In the 4th line of page 9 of the Meiji M, the statement "about 20 hours" is corrected to "about 20 minutes." 6-3 In the ``Brief Description of Drawings'' section of the specification, page 9, line 20, ``diffusion temperature'' is corrected to ``cell temperature.'' Figure 6-4 Figure 2 is corrected as shown in the attached sheet. 7. List of attached documents (1 document stating the entire text of the scope of claims after amendment (11) 1 copy (2) Corrected drawings 1 copy Document stating the entire text of the scope of claim after amendment 2, Claims 1 When manufacturing a semiconductor laser with a structure in which an active layer is sandwiched between cladding layers using the MB2 method, which epitaxially grows crystals on a substrate using molecular beams, impurities are added to the cladding layer to reduce carrier density near the active layer. 2. The semiconductor laser manufacturing method according to claim 1, wherein the substrate is GaAs of the substrate type, and the impurity is N-type Sn. .He whisper 2 figure

Claims (1)

[Claims] 1. When manufacturing a semiconductor laser with a structure in which an active layer is sandwiched between cladding layers by the MBE method in which crystals are epitaxially grown on a substrate using molecular beams, carrier density is small in the vicinity of the active layer. 1. A semiconductor laser manufacturing method characterized by diffusing impurities into a cladding layer so as to achieve the following. 2. The substrate is N-type GaAs, and the impurity is N-type GaAs.
2. The method of manufacturing a semiconductor laser according to claim 1, wherein the semiconductor laser is Sn-shaped.