GB2109155A - Semiconductor laser manufacture - Google Patents
Semiconductor laser manufacture Download PDFInfo
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- GB2109155A GB2109155A GB08132182A GB8132182A GB2109155A GB 2109155 A GB2109155 A GB 2109155A GB 08132182 A GB08132182 A GB 08132182A GB 8132182 A GB8132182 A GB 8132182A GB 2109155 A GB2109155 A GB 2109155A
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- active region
- cladding layer
- layer
- cladding
- conductivity type
- Prior art date
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 37
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 238000005253 cladding Methods 0.000 claims abstract description 57
- 239000000758 substrate Substances 0.000 claims abstract description 22
- 238000001451 molecular beam epitaxy Methods 0.000 claims abstract description 10
- 238000000034 method Methods 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 13
- 230000003287 optical effect Effects 0.000 abstract description 7
- 230000006378 damage Effects 0.000 abstract description 3
- 239000011149 active material Substances 0.000 abstract 1
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 11
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 11
- 230000005855 radiation Effects 0.000 description 10
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 9
- 229910052733 gallium Inorganic materials 0.000 description 9
- 229910052785 arsenic Inorganic materials 0.000 description 8
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 8
- 230000004907 flux Effects 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000004411 aluminium Substances 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 229910052738 indium Inorganic materials 0.000 description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 3
- 238000001465 metallisation Methods 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- MDPILPRLPQYEEN-UHFFFAOYSA-N aluminium arsenide Chemical compound [As]#[Al] MDPILPRLPQYEEN-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- JVPLOXQKFGYFMN-UHFFFAOYSA-N gold tin Chemical compound [Sn].[Au] JVPLOXQKFGYFMN-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004943 liquid phase epitaxy Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/16—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
- H10H20/01—Manufacture or treatment
- H10H20/011—Manufacture or treatment of bodies, e.g. forming semiconductor layers
- H10H20/013—Manufacture or treatment of bodies, e.g. forming semiconductor layers having light-emitting regions comprising only Group III-V materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
- H01S5/2275—Buried mesa structure ; Striped active layer mesa created by etching
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Geometry (AREA)
- Semiconductor Lasers (AREA)
Abstract
A semiconductor laser which can sustain a high optical power density emission without suffering catastrophic optical damage of the reflective facets adopts the so-called "window structure" i.e. with the active material layer (4) spaced from the reflective facets. To make the laser a first cladding layer (3) is provided on a semiconductor substrate (1) of the same conductivity type. The active region is then grown by molecular beam epitaxy as a discrete island (4) after which a second cladding layer (5) is provided on the upper surface of the semiconductor body to envelope the active region (4). The laser can be completed by providing metallized contacts (6,7). Both cladding layers may also be formed by molecular beam epitaxy. <IMAGE>
Description
SPECIFICATION
Semiconductor laser manufacture
This invention relates to a method of manufacturing a semiconductor laser comprising a semiconductor body having an active region between two cladding layers, the material of each cladding layer having a larger bandgap than the material of the active region. This method includes the steps of providing the first cladding layer of a semiconductor substrate, the first layer having the same conductivity type as said substrate, providing the second cladding layer on the first layer, and providing the active region between said first and second cladding layers, said active region having the opposite conductivity type to one or other of the cladding layers.
With recent technological advances laser devices have found many diverse applications particularly, for example, in the field of communications.
The term 'laser' is an acronym for light amplification by the simulated emission of radiation. Basically, the atoms of a laser device can be stimulated by external means to excite the electrons into higher energy states. If there are sufficient electrons in a particular high energy state the condition of socalled "population inversion" is achieved and the laser is then capable of producing an intense coherent beam of substantially monochromatic electromagnetic radiation.
There are various types of laser device employing gaseous, solid and liquid media. One such device is the semiconductor laser which is a solid-state device comprising a semiconductor body having a p-n juntion. The condition of pollution inversion can occur in a so-called 'active region' of the device when a sufficiently large electric current is made to flow across the p-n junction.
When this condition has been achieved there are two main results. Firstly, radiation is emitted from the laser as electrons spontaneously fall to lower energy states and, secondly, the active region becomes an amplifier for radiation of the same frequency as the emitted radiation. In a semiconductor laser the faces of the semiconductor body which are perpendicular to the direction of the emitted radiation can be adapted so that some of the emitted radiation is reflected back and forth through the active region. Thus, the laser comprises a cavity resonator. Above a minimum current oscillation can occur in the resonator, that is to say laser action is achieved.
Unfortunately, it has been found for conventional semiconductor laser devices that the maximum available optical power is limited by the onset of a phenomenon known as catastrophic optical mirror damage (hereinafter referred to as COMD), which is a local destruction of the reflective surfaces of the laser at high optical power density emission.
A Asolution to the COMD problem has been prop- osed by H. Yonezu et al in a paper entitled "High
Optical Power Density Emission from a 'Window
Stripe' Al GaAs Double-Heterostructure Laser" which appeared in Applied Physics Letters, Vol. 34, No. 10 on 15th May 1979. This paper discloses a novel semiconductor laser structure in which the active
region is spaced apart from the reflective surfaces in the direction of the emitted radiation. It is claimed that with this novel structure (referred to as a "window" structure) the maximum available optical
power can be at least one order of magnitude higher than that obtained in conventional structures.
To make this window laser a first n-type cladding
layer is provided on a semiconductor substrate of the same conductivity type. An intermediate n-type layer is then provided on the first cladding layer after which a second n-type cladding layer is provided on the intermediate layer. These three layers are all grown by conventional liquid phase epitaxy. Localized rectangular areas of the intermediate layer are then converted to the p-conductivity type by diffusion from the surface of the second cladding layer into the intermediate layer. In the length direction, that is to say in the direction of eventual radiation emission, adjacent p-type areas are spaced apart, typically by 100 micrometres. Individual laser devices are formed by cleaving the semiconductor body mid-way between adjacent p-type areas.The two cladding layers and the active region are all made of gallium aluminium arsenide. However, the two cladding layers have the same bandgap because they are made of material with the same composition, whereas the active region has a different composition with a smaller bandgap.
Unfortunately, this method of manufacturing "window" laser requires a diffusion step to be carried out after providing the various constituent layers of the laser. Careful control of the diffusion step is important so that the dopant reaches no further than the boundary between the intermediate layer and the first cladding layer. Such accurate control of the diffusion is difficult and inconvenient.
According to the present invention a method of manufacturing a semiconductor laser as specified in the opening paragraph is characterized in that the active region is grown by molecular beam epitaxy as a discrete island on the first cladding layer before providing the second cladding layer on the island and on exposed parts of the first cladding layer so that the island is enveloped by said cladding layers.
This method is particularly advantageous not only because it involves fewer steps than the known method, but also because it avoids the difficult and inconvenient diffusion step.
A p-n junction is present between the active region and one or other of the cladding layers. It is across this junction that current injection occurs in order to achieve laser action. As discussed in more detail hereinafter this junction may, in certain circumstances, be a homojunction. However, absorption within the laser of the emitted radiation can be minimized when the junction is a heterojunction.
The manufacture of a semiconductor laser using a method in accordance with the invention is simplified when one or both of the cladding layers are grown by molcular beam epitaxy. Clearly this avoids the need to employ different apparatus for providing the cladding layers.
An embodiment of the invention will now be described, by wav of example, with reference to the accompanying drawing, in which:
Figure 1 is a cross-sectional view, taken on the line
I-I' of Figure 2, of a semiconductor laser manufactured by a method in accordance with the present invention, and
Figure 2 is a plan view of the semiconductor laser of Figure 1 at an intermediate stage of it's manufacture.
For the sake of clarity the Figures are not drawn to scale.
The starting material is an n-type semiconductor substrate 1, for example a gallium arsenide substrate, with a thickness of approximately 500 micrometres and a resistivity of, for example 2 x 10-3 ohm.cm. The major surfaces of the substrate are the (1,0,0) planes. The substrate is prepared by polishing and then etching to a thickness of, for example 300 micrometres using a solution comprising 3 parts
H2SO4, 1 part H2O2, and 1 part H2O. The substrate is then rinsed in silica distilled water before being blown dry using filtered, dry nitrogen. The back surface 1 a of the substrate 1 is then wetted with indium before placing the substrate onto a molybdenum platen (not shown in the Figures) and loading it into the chamber of a conventional molecular beam epitaxial growth apparatus (again, not shown in the
Figures).Once loaded the substrate is heated to a temperature of approximately 6200C in a flux of at
least 1014 arsenic molecules/cm2/sec. The first molecular beam epitaxial growth step can then be commenced. Firstly, the substrate 1 is cooled to approximately 580 C, after which it is exposed to fluxes of gallium, arsenic, and tin molecules to grow an n+ buffer layer 2 of gallium arsenide on the major surface 1 b of substrate 1. The n+ layer 2 may have a thickness of 1 micrometre and the concentration of the n-type impurity may be 1018 atoms cm-3. To meet these conditions the following fluxes can be used, i.e. 6 x 1014 gallium molecules/cm2/sec., 1015 arsenicmolecules/cm2/sec., and 3 x 1010 tin mole
cules/cm2/sec.
The next step is to grow by molecular beam
epitaxy an n-type aluminium gallium arsenide layer
3 to a thickness of approximately 1.5 micrometres on
the n+ layer 2. For this purpose the semiconductor
body is heated to a temperature of approximately 6500C and then it is exposed to the following fluxes,
namely6 x 1014 gallium molecules/cm2/sec.,3 x 1014 aluminium molecules/cm2/sec., 1015 arsenic moleculesicm2/sec., and 3 x 1010 tin molecules/cm2/
sec. Under these conditions the n-type layer will
have the approximate formula A10.33Ga0.67AS and a
concentration of impurity atoms of about 3 x 1017 cm 3. The layer 3 constitutes the first cladding layer
of the laser device.
The next step involves the growth by molecular
beam epitaxy of the active region 4. At this stage a
mask made of a high purity refractory material such
as silicon is introduced into the apparatus and
placed in contact or in close proximity with the upper
surface of the first cladding layer 3. The mask which
has a window of, for example 300 micrometres x 10
micrometres is oriented such that the sides of the
window are aligned along the < 110 > directions of
the substrate. A discrete island 4 of p-type gallium arsenide is then grown by molecular beam epitaxy on layer 3 through the window in the mask.The thickness of the island may be, for example, 0.25 micrometre and the doping concentration of the gallium arsenide may be 1017 cm#3. To meet these conditions a flux of 6 x 1014 gallium molecules/cm2/ sec., and 1015 arsenic molecules/cm2/sec. may be used. The lateral dimensions of the island 4 will be approximately the same as those of the window in the mask, that is to say 300 micrometres x micrometres. After growing the island 4 the mask is removed from the molecular beam epitaxial growth apparatus.
The next step involves growing by molecular beam epitaxy a p+ layer 5, i.e. the second cladding layer, on the island 4 and on the exposed parts of the first cladding layer 3. In this way the island 4 becomes totally enveloped by the two cladding layers. To grow the second cladding layer 5 to a thickness of, for example, 1.5. micrometres the semiconductor body is exposed to a flux of 6 x 1014 gallium molecules/cm2/sec., 3 x 1014 aluminium molecules/cm2lsec., 1015 arsenic molecules/cm2/sec., and 6 x 1010 beryllium moleculeslcm2/sec.
Next, a 0.5 micrometre thick layer contact of p+ gallium arsenide is grown by molecular beam epitaxy on the entire upper surface of the second cladding layer 5 using a flux of 6 x 1014 gallium molecules/cm2/sec., 105 arsenic moleculeslcm2/sec., and 3 x 1011 beryllium molecules/cm2/sec.
The temperature can then be reduced to about 4000C while exposing the semiconductor body to a flux of 1015 arsenic molecules/cm2/sec. The molecular beams are switched off before cooling the body to room temperature and the removing it from the growth apparatus and from the molybdenum platen.
The indium coating the back surface 1 a of the substrate 1 is then removed using cold hydrochloric acid while the front surface of the semiconductor
body is masked using, for example, wax or photoresist (not shown in the Figures).
The substrate can then be thinned in conventional manner to a thickness of approximately 100 mic
rometres after which a metallization layer 6, for example, a layer 500 angstroms thick of a gold-tin alloy is deposited in known manner on the back surface 1 a of the substrate. A metallization layer, for example, a three layer system of chromium (500 angstroms), platinum (500 angstrons), and gold (100
angstroms) is deposited on the front surface of the semiconductor body, that is to say on the exposed surface of the p+ gallium arsenide layer. By using
conventional photolithographic and etching techni
ques parts of this metallization as well as the p+
gallium arsenide layer are removed to leave metal
contact strip 9 and a low ohmic gallium arsenide
region 7 aligned with the island 4.
As described above the method has been in terms
of manufacturing a single laser device. In practice a
plurality of such devices would be formed simultaneously across a semiconductor wafer. In this case
adjacent islands 4 would be spaced apart by 400
micrometres in the length direction and 400 mic
rometres on the width direction. Individual laser
devices would then be formed by cleaving the the semiconductor body in the < 110 > directions. For example, the semiconductor body may be cleaved mid-way between the long sides of the islands 4 and close to the short sides thereof. The cleaved faces of the device extending at right angles to the long sides of the island 4, that is to say faces 8 in the Figures, form the reflective facets of the laser device. The spacing between these faces 8 and the active region 5 may be, for example, 10 micrometres.Each laser device can then be mounted in a usual package using methods which are well-known to those skilled in the art.
It is noted that the embodiment described here is merely illustrative of a method of manufacturing a semiconductor laser in accordance with the invention. In the light of the above description it will be clear to a person skilled in the artthat many modifications are possible within the scope of the invention. Thus for example the semiconductor material of the laser may be based on Ill-V compounds other than the gallium aluminium arsenidel gallium arsenide system detailed above. More particularly, these compounds may comprise gallium, indium, and/or aluminium from Group Ill of the periodic table and arsenic, phosphorus and/or antimony from Group V. In any case the material of the cladding layers must have a higher bandgap than the material of the active layer.
In another modification the material of the active region may have the same conductivity type as the first cladding layer, in this case the n-conductivity type. The p-n junction would then be formed between the active region and the second cladding layer.
Of course it will be obvious to the person skilled in the art that the conductivity type of all the various constituent parts of the semiconductor laser described above may be reversed simultaneously. In this context it is noted that the absorption edge in n-type gallium arsenide or aluminium gallium arsenide shifts to higher energy with an increase in electron concentration due to the so-called Burstein shift, whereas the emitted photon energy of the p-type material decreases as the impurity concentration increases. Therefore, when the p-n junction is formed between ap-type active region and an n-type second cladding layer, the junction may be a homojunction because the radiation emitted by the active region will not be absorbed to any significant extent by that part of the second cladding layer which is co-planar with the active region. However, in order to ensure minimum absorption the second cladding layer is made of a material having a different composition to the active region and having a higher bandgap. In this case the laser will be of the so-called double heterostructure type as both junctions between the active region and the cladding layers will be junctions between different materials, or at least materials having a different composition.
Claims (8)
1. A method of manufacturing a semiconductor laser comprising a semiconductor body having an active region between two cladding layers, the material of each cladding layer having a larger bandgap than the material of the active region, which method includes the steps of providing the first cladding layer on a semiconductor substrate, the first layer having the same conductivity type as the substrate, providing the second cladding layer on the first layer, and providing the active region between said first and second cladding layers, said active region having the opposite conductivity type to one or other of the cladding layers, characterized in that the active region is grown by molecular beam epitaxy as a discrete island on the first cladding layer before providing the second cladding layer on the island and on exposed parts of the first cladding layer so that the island is enveloped by said cladding layers.
2. A method as claimed in Claim 2, in which the junction between the active region and the first cladding layer and the junction between the active region and the second cladding layer are both heterojunctions.
3. A method as claimed in Claim 2, in which the active region is of the opposite conductivity type to the first cladding layer, the second cladding layer having the same conductivity type as the active region.
4. A method as claimed in Claim 1 or 2, in which the active region is of the same conductivity type as the first cladding layer, the second cladding layer having the opposite conductivity type to the active region.
5. A method as claimed in any of the preceding
Claims, in which at least one of the cladding layers is grown by molecular beam epitaxy.
6. A method as claimed in any of the preceding
Claims, including the step of providing a buffer layer having the same conductivity type as the substrate between the first cladding layer and said substrate.
7. A method as claimed in any of the preceding
Claims, including the step of providing a semiconductor contact layer on the second cladding layer, which contact layer has the same conductivity type as, but a lower resistivity, than said second cladding layer.
8. A method of manufacturing a semiconductor laser substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08132182A GB2109155A (en) | 1981-10-26 | 1981-10-26 | Semiconductor laser manufacture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08132182A GB2109155A (en) | 1981-10-26 | 1981-10-26 | Semiconductor laser manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2109155A true GB2109155A (en) | 1983-05-25 |
Family
ID=10525394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08132182A Withdrawn GB2109155A (en) | 1981-10-26 | 1981-10-26 | Semiconductor laser manufacture |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2109155A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2130007A (en) * | 1982-10-29 | 1984-05-23 | Rca Corp | Semiconductor laser |
| US5028563A (en) * | 1989-02-24 | 1991-07-02 | Laser Photonics, Inc. | Method for making low tuning rate single mode PbTe/PbEuSeTe buried heterostructure tunable diode lasers and arrays |
| US5119388A (en) * | 1989-02-24 | 1992-06-02 | Laser Photonics, Inc. | Low tuning rate PbTe/PbEuSeTe buried quantum well tunable diode lasers and arrays |
-
1981
- 1981-10-26 GB GB08132182A patent/GB2109155A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2130007A (en) * | 1982-10-29 | 1984-05-23 | Rca Corp | Semiconductor laser |
| US5028563A (en) * | 1989-02-24 | 1991-07-02 | Laser Photonics, Inc. | Method for making low tuning rate single mode PbTe/PbEuSeTe buried heterostructure tunable diode lasers and arrays |
| US5119388A (en) * | 1989-02-24 | 1992-06-02 | Laser Photonics, Inc. | Low tuning rate PbTe/PbEuSeTe buried quantum well tunable diode lasers and arrays |
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