CA1056043A - Optoelectronic devices with control of light propagation - Google Patents
Optoelectronic devices with control of light propagationInfo
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- CA1056043A CA1056043A CA254,255A CA254255A CA1056043A CA 1056043 A CA1056043 A CA 1056043A CA 254255 A CA254255 A CA 254255A CA 1056043 A CA1056043 A CA 1056043A
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- 230000005693 optoelectronics Effects 0.000 title claims abstract description 8
- 239000000758 substrate Substances 0.000 claims abstract description 40
- 230000004888 barrier function Effects 0.000 claims abstract description 32
- 230000003287 optical effect Effects 0.000 claims description 18
- 238000010521 absorption reaction Methods 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 12
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 10
- 238000005530 etching Methods 0.000 claims description 4
- 239000004065 semiconductor Substances 0.000 claims 11
- 239000011358 absorbing material Substances 0.000 claims 1
- 230000001902 propagating effect Effects 0.000 abstract description 2
- 230000008033 biological extinction Effects 0.000 description 11
- 239000013078 crystal Substances 0.000 description 10
- 230000008901 benefit Effects 0.000 description 5
- 238000002955 isolation Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000000873 masking effect Effects 0.000 description 3
- 239000011521 glass Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229920002120 photoresistant polymer Polymers 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 235000007911 Anacolosa luzoniensis Nutrition 0.000 description 1
- 244000217177 Anacolosa luzoniensis Species 0.000 description 1
- 229910017974 NH40H Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008569 process Effects 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
- H01S5/02—Structural details or components not essential to laser action
- H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/0004—Devices characterised by their operation
- H01L33/002—Devices characterised by their operation having heterojunctions or graded gap
- H01L33/0025—Devices characterised by their operation having heterojunctions or graded gap comprising only AIIIBV compounds
-
- 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
-
- 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
-
- 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
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0601—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium comprising an absorbing region
-
- 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
- H01S5/2054—Methods of obtaining the confinement
- H01S5/2059—Methods of obtaining the confinement by means of particular conductivity zones, e.g. obtained by particle bombardment or diffusion
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- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Computer Hardware Design (AREA)
- Geometry (AREA)
- Manufacturing & Machinery (AREA)
- Semiconductor Lasers (AREA)
- Led Devices (AREA)
- Photovoltaic Devices (AREA)
- Optical Integrated Circuits (AREA)
Abstract
OPTOELECTRONIC DEVICES WITH CONTROL OF LIGHT PROPAGATION Abstract of the Disclosure In an optoelectronic device, light is restrained from propagating in one or both confining layers on either side of an active layer by forming one or more photon absorbing barriers in one, or both, confining layers. A photon absorbing barrier can be formed by proton bombardment of a confining layer, by producing a protrusion from the substrate into the adjacent confining layer, or by producing a protrusion from a capping layer into the other confining layer, or by combinations of these. Spaced apart barriers can define a device, or sections of a multi-sectioned device, for example a monolithic light emitting diode and modulator. -1-
Description
105~043 This invention relates to optoelectronic devices and the control of light propagation therein, particularly to at least reduce the emission of photons from, or into, other than the desired areas of a device.
In optoelectronic devices, such as light emitting diodes (LEDs), 1asers, modulators and detectors, there is often a need to accurately define the active region of these devices, that is the region at which light emission or light absorption takes place. For example, in heterostructure GaAs/GaAlAs devices~ ~
10 a fraction of the light which is either generated directly in the -active layer (LED's or lasers) or coupled into the active region (modulators or detectors) will escape from the active or guiding -layer since the confinement will not be perfect. Such unguided light may exit through the GaAlAs confin7ng layers adjacent to the guiding layer and trigger undesired optical response of subsequent optical elements.
The present invention provides a way of at least reducing the effects of imperfect confinement by providing a barrier, or barriers to the unguided light in the confining layers.
This invention will be readily understood by the following descriptlon of certain embodiments, by way of example, in conjunction with the accn~panying drawings, in which:-Figure 1 is a diagrammatic cross-section through a device illustrating the basic concept of the inventioni Figure 2 is a curve illustrating the light transmission for different parts of the device in Figure l;
Figure 3 is a curve illustrating the ratios of light transmission through bombarded and nonbombarded regions of ~ ;
a device as in Figure 1, for different waveleng~hs, 3V Figure 4 is a diagrammatic cross-section through an integrated LED - modulator device incorporating one form of 1~ 5~ 3 the invention;
Figure 5 illustrates the improvement in modulator extinction ratios, using the invention;
Figures 6 to 9 illustrate steps in the production of an LED emitter - modulator structure, incorporating one form of the invention, Figures 8 and 9 being cross-sections on the lines VIII-VIII and IX-IX of Figures 6 and 7 respective7y;
Figure 10 is a diagrammatic cross-section of the finished structure, as on the line X-X of Figure 7;
Figure 11 is a diagrammatic cross-section of a finished structure incorporating another form of the invention;
Figure 12 is a diagrammatic cross-section of a structure, similar to that of Figure 11, but incorporating the present invention in a further form;
Figures 13 and 14 illustrate diagrammatic cross-sections through two devices which have well-defined active or guiding layers into which optically absorbing barriers are introduced by proton bombardment or crystal growth techniques respectively.
The present invention provides a barrier, or barriers which are incorporated into the confining layer, or layers of double heterostructure devices to prevent unguided light in those confining layers from exiting through the side facets. This provides a variety of advantages for LED's, lasers, modulators, and detectors. One advantage is that the only light which exits from these devices comes from the active or guiding layer. This will essentially eliminate undesired optical responses generated by stray light. A second advantage is that the geometry of the active region is well-defined so that emitting areas can be made comparable in size to the cores of optical fibers which might be attached to the end faces. A third advantage occurs in .
~I)St;0~3 electroabsorption or phase modulators in which the light which escapes into and propages along the confining layers will reduce the modulation depth. For example, integrated LED emitter-modulator structures can achieve up to 20dB extinction ratios via the process of electroabsorption. However these high extinction ratios are only achieved by limiting the area of the ~--detector so that only light which exits from the active, or guiding layer is recorded by the detector. If the light which propagates outside the active, or guiding layer is also detected, 10 then the extinction ratio is significantly reduced.
In a typical double heterostructure device, the }guiding or active layer consists of Gal yAlyAs material with y'O.l, such a layer has an optical absorption edge in the range 8~0-870 nm and will guide photons with wavelengths longer than the aborption edge value. It is proposed that one way of over-coming light spill of these photons into and out of the Gal xAlxAs confining layers is by introducing optically absorbing regions into the confining layers by the method of proton bombardment.
Thus photons from the guiding layer must be absorbed in a -. ~
~;~20 confining layer of completely different material (typically GaO 7Alo 3As) where the band edge is near 680 nm. This is a completely different situation to that in which proton bombardment of GaAs provides absorption for wavelengths close to the GaAs absorption edge. The basic validity of the above proposal has been established using the device illustrated in Figure 1. A 5~m thick GaO 7Al o 3As layer was first grown on an n-GaAs substrate.
Approximately one half of the area of this layer was bombarded at 390 keY, 3 x 1015 cm 2, the other half was shielded from the :: .
beam. The crystal was then glued to a glass slide with a trans-3~ parent photoresist and the whole of the n-type substrate was -removed by using a selective etch (H202~NH40H, pH = 8.70). After ' ' ' .
. , .
1()5~43 an etch time of about 60 minutes, only the 5 ~m thick layer remained. In Figure 1 the glass slide is indicated at 10, the photoresist layer at 11 and the 5 ~m thick GaO 7Alo 3As layer is indicated at 12. The proton bombarded area is indicated at 13.
Light from a monochromatic source was then passed through both the bombarded and nonbombarded regions of the crystal, as indicated by arrors X, and detected by a cooled photo-multipler.
Figure 2 illustrates a typical variation in the transmitted light variation across a crystal for a fixed wave-length of 750 nm. The undulations are due to surface roughnessof the etched surface but the location of the boundary 14 between bombarded and nonbombarded regions is easily identified. The two intensities of light are indicated on Figure 1, and as an average on Figure 2, as Tb and To for bombarded and nonbombarded regions respectively.
Figure 3 illustrates how the ratio of light transmission through the unbombarded and bombarded regions of a crystal (i.e. Io/~b) varies as a function of wavelength. As will be seen, the ratio varies from about 1.2 for wavelengths of
In optoelectronic devices, such as light emitting diodes (LEDs), 1asers, modulators and detectors, there is often a need to accurately define the active region of these devices, that is the region at which light emission or light absorption takes place. For example, in heterostructure GaAs/GaAlAs devices~ ~
10 a fraction of the light which is either generated directly in the -active layer (LED's or lasers) or coupled into the active region (modulators or detectors) will escape from the active or guiding -layer since the confinement will not be perfect. Such unguided light may exit through the GaAlAs confin7ng layers adjacent to the guiding layer and trigger undesired optical response of subsequent optical elements.
The present invention provides a way of at least reducing the effects of imperfect confinement by providing a barrier, or barriers to the unguided light in the confining layers.
This invention will be readily understood by the following descriptlon of certain embodiments, by way of example, in conjunction with the accn~panying drawings, in which:-Figure 1 is a diagrammatic cross-section through a device illustrating the basic concept of the inventioni Figure 2 is a curve illustrating the light transmission for different parts of the device in Figure l;
Figure 3 is a curve illustrating the ratios of light transmission through bombarded and nonbombarded regions of ~ ;
a device as in Figure 1, for different waveleng~hs, 3V Figure 4 is a diagrammatic cross-section through an integrated LED - modulator device incorporating one form of 1~ 5~ 3 the invention;
Figure 5 illustrates the improvement in modulator extinction ratios, using the invention;
Figures 6 to 9 illustrate steps in the production of an LED emitter - modulator structure, incorporating one form of the invention, Figures 8 and 9 being cross-sections on the lines VIII-VIII and IX-IX of Figures 6 and 7 respective7y;
Figure 10 is a diagrammatic cross-section of the finished structure, as on the line X-X of Figure 7;
Figure 11 is a diagrammatic cross-section of a finished structure incorporating another form of the invention;
Figure 12 is a diagrammatic cross-section of a structure, similar to that of Figure 11, but incorporating the present invention in a further form;
Figures 13 and 14 illustrate diagrammatic cross-sections through two devices which have well-defined active or guiding layers into which optically absorbing barriers are introduced by proton bombardment or crystal growth techniques respectively.
The present invention provides a barrier, or barriers which are incorporated into the confining layer, or layers of double heterostructure devices to prevent unguided light in those confining layers from exiting through the side facets. This provides a variety of advantages for LED's, lasers, modulators, and detectors. One advantage is that the only light which exits from these devices comes from the active or guiding layer. This will essentially eliminate undesired optical responses generated by stray light. A second advantage is that the geometry of the active region is well-defined so that emitting areas can be made comparable in size to the cores of optical fibers which might be attached to the end faces. A third advantage occurs in .
~I)St;0~3 electroabsorption or phase modulators in which the light which escapes into and propages along the confining layers will reduce the modulation depth. For example, integrated LED emitter-modulator structures can achieve up to 20dB extinction ratios via the process of electroabsorption. However these high extinction ratios are only achieved by limiting the area of the ~--detector so that only light which exits from the active, or guiding layer is recorded by the detector. If the light which propagates outside the active, or guiding layer is also detected, 10 then the extinction ratio is significantly reduced.
In a typical double heterostructure device, the }guiding or active layer consists of Gal yAlyAs material with y'O.l, such a layer has an optical absorption edge in the range 8~0-870 nm and will guide photons with wavelengths longer than the aborption edge value. It is proposed that one way of over-coming light spill of these photons into and out of the Gal xAlxAs confining layers is by introducing optically absorbing regions into the confining layers by the method of proton bombardment.
Thus photons from the guiding layer must be absorbed in a -. ~
~;~20 confining layer of completely different material (typically GaO 7Alo 3As) where the band edge is near 680 nm. This is a completely different situation to that in which proton bombardment of GaAs provides absorption for wavelengths close to the GaAs absorption edge. The basic validity of the above proposal has been established using the device illustrated in Figure 1. A 5~m thick GaO 7Al o 3As layer was first grown on an n-GaAs substrate.
Approximately one half of the area of this layer was bombarded at 390 keY, 3 x 1015 cm 2, the other half was shielded from the :: .
beam. The crystal was then glued to a glass slide with a trans-3~ parent photoresist and the whole of the n-type substrate was -removed by using a selective etch (H202~NH40H, pH = 8.70). After ' ' ' .
. , .
1()5~43 an etch time of about 60 minutes, only the 5 ~m thick layer remained. In Figure 1 the glass slide is indicated at 10, the photoresist layer at 11 and the 5 ~m thick GaO 7Alo 3As layer is indicated at 12. The proton bombarded area is indicated at 13.
Light from a monochromatic source was then passed through both the bombarded and nonbombarded regions of the crystal, as indicated by arrors X, and detected by a cooled photo-multipler.
Figure 2 illustrates a typical variation in the transmitted light variation across a crystal for a fixed wave-length of 750 nm. The undulations are due to surface roughnessof the etched surface but the location of the boundary 14 between bombarded and nonbombarded regions is easily identified. The two intensities of light are indicated on Figure 1, and as an average on Figure 2, as Tb and To for bombarded and nonbombarded regions respectively.
Figure 3 illustrates how the ratio of light transmission through the unbombarded and bombarded regions of a crystal (i.e. Io/~b) varies as a function of wavelength. As will be seen, the ratio varies from about 1.2 for wavelengths of
2~ 7Z5 nm t~ about 0.45 for wavelengths of 900 nm.
As an example of a device employing the invention, an integrated LED - modulator structure is illustrated in Figure 4. The structure illùstrated is a double heterostructure comprising a GaAs substrate 20, a first Gal xAlxAs (x ~ 0.3) confining layer 21, an active GaAs layer 22, a second Gal xAlxAs (x ~ 0.3) confining layer 23 and an optional capping layer 24.
A masking layer 25 is formed on the capping layer 24 and proton bombardment forms regions of high optical absorption in the second confining layer 23 (and in the capping layer 24 although this is incidental). The conductivity type of the layers can vary provided there is the correct relationship. Thus the substrate is n-type, .
105~043 the first confining layer and the active layer are n-type while the second confining layer (and capping layer) are p-type. If the substrate is p-type, the first confining layer and active layer are also p-type and the second confining layer (and capping layer) are n-type.
Hole 26 is then etched through the substrate 20.
A suitable etch is as referred to previously, for removal of the substrate in the preparation of the device of Figure l. Conven-iently the etch is selective for GaAs, stopping at the first confining layer 21, the bottoms of the hole 26 being at the boundary between substrate 20 and confining layer 21. A further proton bombardment is carried out from the substrate side of the structure to form a region 27 of high optical absorption at the bottom of the hole as well as a reg;on 30 along the periphery of the hole. The LED emitter section is at 28 and is energized by an appropriate potential or bias applied to the capping layer 24 in the emitter section and to the contact on the substrate 20.
The modulator section 29 modulates the light emission from the active layer 22 in the emitter section, again by suitable potentials applied to the capping layer 24 and substrate 20.
The photons labelled B and C pass into the confining layers 21 and 23. Photons B will be absorbed by the proton damaged regions 26 and 27. The photons C will be absorbed to some extent by the proton damage at the periphery of the hole 26, indicated at 30. Complete abosrption in the substrate can be assured if the n-type active layer 22 contains a small amount of Al which will shift the photon energy to values beyond the absorption edge of substrate 20. A detector is indicated at 31.
The possible improvement gains are illustrated by the curves in Figure 5. The curves illustrate extinction ratio versus effective detector width at the modulator exit face. The highest lOS~i,043 extinction ratios are obtained when the effective detector width is narrower than the thickness of the guiding layer 22. When the effective width is greater than the guiding layer 22, so that light from the conf;ning layers 21 and 23 is also included, the extinction ratio is reduced by 8-10 dB. By preventing the propagation of light rays through the confining layers of the modulator, the size of the effective detector width is not so critical. A wider effective detector width can be used and still obtain high extinction ratios. The extinction ratio will be improved by 8-lOdB relative to the same wider effective detector width without photon absorption. Curves 33 and 34 illustrate extinction ratio versus effective detector width for two convent-ional modulator devices operated at negative biases of 24 volts and 18 volts, respectively. Curves 33a and 34a illustrate the improvements achieved by introducing optical absorption into the confining layers by proton bombardment.
Figures 6 to 9 illustrate two steps in producing a high-speed high extinction ratio LED emitter-modulator structure, and Figure 10 is a cross-section through the structure - on the line X-X of Figure 7. The structure ;llustrated is a double heterostructure, as in Figure 4, with a substrate 35, first confining layer 36, active or guiding layer 37, a second confining layer 38 and optional capping layer 39. The conductivity type of substrate 35 and layers 36, 37, 38 and 39 as previously described in rélation to Figure 4. High speed operation is obtained by limiting the junction capacity with a first proton bombardment.
A metal stripe 40 is produced on the capping layer 39 and the structure bombarded. The bombardment alters the layers 39, 38 and 37, also part of the layer 36, as seen in Figure 8. Narrow
As an example of a device employing the invention, an integrated LED - modulator structure is illustrated in Figure 4. The structure illùstrated is a double heterostructure comprising a GaAs substrate 20, a first Gal xAlxAs (x ~ 0.3) confining layer 21, an active GaAs layer 22, a second Gal xAlxAs (x ~ 0.3) confining layer 23 and an optional capping layer 24.
A masking layer 25 is formed on the capping layer 24 and proton bombardment forms regions of high optical absorption in the second confining layer 23 (and in the capping layer 24 although this is incidental). The conductivity type of the layers can vary provided there is the correct relationship. Thus the substrate is n-type, .
105~043 the first confining layer and the active layer are n-type while the second confining layer (and capping layer) are p-type. If the substrate is p-type, the first confining layer and active layer are also p-type and the second confining layer (and capping layer) are n-type.
Hole 26 is then etched through the substrate 20.
A suitable etch is as referred to previously, for removal of the substrate in the preparation of the device of Figure l. Conven-iently the etch is selective for GaAs, stopping at the first confining layer 21, the bottoms of the hole 26 being at the boundary between substrate 20 and confining layer 21. A further proton bombardment is carried out from the substrate side of the structure to form a region 27 of high optical absorption at the bottom of the hole as well as a reg;on 30 along the periphery of the hole. The LED emitter section is at 28 and is energized by an appropriate potential or bias applied to the capping layer 24 in the emitter section and to the contact on the substrate 20.
The modulator section 29 modulates the light emission from the active layer 22 in the emitter section, again by suitable potentials applied to the capping layer 24 and substrate 20.
The photons labelled B and C pass into the confining layers 21 and 23. Photons B will be absorbed by the proton damaged regions 26 and 27. The photons C will be absorbed to some extent by the proton damage at the periphery of the hole 26, indicated at 30. Complete abosrption in the substrate can be assured if the n-type active layer 22 contains a small amount of Al which will shift the photon energy to values beyond the absorption edge of substrate 20. A detector is indicated at 31.
The possible improvement gains are illustrated by the curves in Figure 5. The curves illustrate extinction ratio versus effective detector width at the modulator exit face. The highest lOS~i,043 extinction ratios are obtained when the effective detector width is narrower than the thickness of the guiding layer 22. When the effective width is greater than the guiding layer 22, so that light from the conf;ning layers 21 and 23 is also included, the extinction ratio is reduced by 8-10 dB. By preventing the propagation of light rays through the confining layers of the modulator, the size of the effective detector width is not so critical. A wider effective detector width can be used and still obtain high extinction ratios. The extinction ratio will be improved by 8-lOdB relative to the same wider effective detector width without photon absorption. Curves 33 and 34 illustrate extinction ratio versus effective detector width for two convent-ional modulator devices operated at negative biases of 24 volts and 18 volts, respectively. Curves 33a and 34a illustrate the improvements achieved by introducing optical absorption into the confining layers by proton bombardment.
Figures 6 to 9 illustrate two steps in producing a high-speed high extinction ratio LED emitter-modulator structure, and Figure 10 is a cross-section through the structure - on the line X-X of Figure 7. The structure ;llustrated is a double heterostructure, as in Figure 4, with a substrate 35, first confining layer 36, active or guiding layer 37, a second confining layer 38 and optional capping layer 39. The conductivity type of substrate 35 and layers 36, 37, 38 and 39 as previously described in rélation to Figure 4. High speed operation is obtained by limiting the junction capacity with a first proton bombardment.
A metal stripe 40 is produced on the capping layer 39 and the structure bombarded. The bombardment alters the layers 39, 38 and 37, also part of the layer 36, as seen in Figure 8. Narrow
3~ gaps 42 are then etched into the metal stripe and a second proton bombardment which alters only layers 39 and 38 forms electrical , ':
.. . . . . . . .
~(~St;043 isolation between sections and ensures optical absorption in the top confining layer 38. The structure is then as in Figure 9.
Finally holes 43 are etched through the substrate 35 to the first confining layer 36 and a third proton bombardment is performed into these holes from the substrate side, to form regions 44 which provide optical isolat;ons (absorption) in the lower, or first, confining layer. The mask layer for etching the holes 43 and masking from the third bombardment is indicated at 45. A
certain amount of bombardment damage also occurs on the sides of the holes 43 at 46. For both second and third bombardments the proton beam energy is accurately controlled to ensure that protons penetrate only to a minimum extent into the active or guiding layer 37. In Figure 10, the emitter section is the central one third portion between the bombarded regions 42. The structure illustrated in Figure 10 has one LED emitter section 46 with modulator sections 47 positioned on either side. These devices are most conveniently made by fabricating a large number of sections on a common substrate and then dividing along the dashed line 48 (Figure 10).
ln relation to Figures 6 to 10, if high modulator -speed is not critical, the first proton bombardment can be eliminated. The only bombardment required is that which creates regions 42, (now extending in stripes all across the crystal) to provide electrical (and optical) isolation between sections ~; and prevent propagation of leakage photons in the second confining layer 38. It is also possible to provide an alternative optical isolation structure for the first confining layer. In Figure 11 a photon absorbing region is formed by initial profiling of a substrate. As illustrated in Figure 11 a substrate 50 is masked and etched on one sur~ace to form upstanding ribs or ridges 51.
The first confining layer 5~ is then formed followed by formation l~)S~iO43 of the active or guiding layer 53. The thickness of layer 52 can be controlled for careful crystal growth such that the gap between the top surface of the ribs 51 and active layer 53 is small. The second confining layer 54 is formed followed by capping layer 55.
A masking layer 56 is formed on the capping layer 55 and isolation regions 57 are formed by proton bombardment through layers 54 and 55 down to the upper surface of the active or guiding layer 53. The proton bombardment regions 57 prevent propagation of photons B along the upper or second confining layer 54 into the modulator section 60, from the emitter section 61, while the ribs 51 absorb the photons B propagating in the lower or first confining layer 52. The photons C are absorbed in the substrate.
To ensure substantially complete absorption of unwanted protons the active layer 53 contains some Al, having the for~ n-Gal yA1yAs -with y - 0.1. The photons A will be the only light to emit from the emitter 61 and propagate through the modulator 60.
As an alternative to the proton bombarded regions 57 which were used in Figure 11 to provide optical absorpt;on, some devices can effectively utilize profiling plus crystal growth techniques to provide the required optical absorption in both confining layers. This is illustrated in Figure 12 using the same referencesas in Figure 11 where applicable. In this case, up-standing ridges 51 provide optical absorption in the ~irst confining layer while inverted ridges 62 provide optical absorption in the second confining layer. In such an arrangement ~he capping layer 55 is not optional and would have properties the same as substrate 50, that is, be essentially GaAs (with little or no Al content). This would ensure absorption of photons B provided the guiding or active layer 53 is of GaAlAs, for example 30 GaO gAlo lAs. ;~ -In addition to the integrated emitter-modulator ~S6043 devices discussed previously, the inventions are applicable to many discrete optoelectronic devices such as LED's, laser, -modulators and detectors. Diagrammatic cross-sections are shown in Figures 13 and 14 for the cases of optical barriers introduced by the techniques of proton bombardment and crystal growth, respectively. In each case a well-defined active or guiding layer is defined which provides those advantages discussed previously.
In these devices, the structure comprises a substrate 63 with a p- or n-type active layer 64 and confining layers 65 and 66 on either side o~ the active layer. A capping layer 67 is on top of confining layer 66. Substrate and first confining layer are typically n-type while second confining layer and capping layer are of p-type. Precise definition of the active layer is provided at the exit facets at 68 by proton bombardment in Figure 13 ~;
and at 69 by crystal growth in Figure l4.
i~ : .
, .
;~
:;
. . .. . . . . . .
.. . . . . . . .
~(~St;043 isolation between sections and ensures optical absorption in the top confining layer 38. The structure is then as in Figure 9.
Finally holes 43 are etched through the substrate 35 to the first confining layer 36 and a third proton bombardment is performed into these holes from the substrate side, to form regions 44 which provide optical isolat;ons (absorption) in the lower, or first, confining layer. The mask layer for etching the holes 43 and masking from the third bombardment is indicated at 45. A
certain amount of bombardment damage also occurs on the sides of the holes 43 at 46. For both second and third bombardments the proton beam energy is accurately controlled to ensure that protons penetrate only to a minimum extent into the active or guiding layer 37. In Figure 10, the emitter section is the central one third portion between the bombarded regions 42. The structure illustrated in Figure 10 has one LED emitter section 46 with modulator sections 47 positioned on either side. These devices are most conveniently made by fabricating a large number of sections on a common substrate and then dividing along the dashed line 48 (Figure 10).
ln relation to Figures 6 to 10, if high modulator -speed is not critical, the first proton bombardment can be eliminated. The only bombardment required is that which creates regions 42, (now extending in stripes all across the crystal) to provide electrical (and optical) isolation between sections ~; and prevent propagation of leakage photons in the second confining layer 38. It is also possible to provide an alternative optical isolation structure for the first confining layer. In Figure 11 a photon absorbing region is formed by initial profiling of a substrate. As illustrated in Figure 11 a substrate 50 is masked and etched on one sur~ace to form upstanding ribs or ridges 51.
The first confining layer 5~ is then formed followed by formation l~)S~iO43 of the active or guiding layer 53. The thickness of layer 52 can be controlled for careful crystal growth such that the gap between the top surface of the ribs 51 and active layer 53 is small. The second confining layer 54 is formed followed by capping layer 55.
A masking layer 56 is formed on the capping layer 55 and isolation regions 57 are formed by proton bombardment through layers 54 and 55 down to the upper surface of the active or guiding layer 53. The proton bombardment regions 57 prevent propagation of photons B along the upper or second confining layer 54 into the modulator section 60, from the emitter section 61, while the ribs 51 absorb the photons B propagating in the lower or first confining layer 52. The photons C are absorbed in the substrate.
To ensure substantially complete absorption of unwanted protons the active layer 53 contains some Al, having the for~ n-Gal yA1yAs -with y - 0.1. The photons A will be the only light to emit from the emitter 61 and propagate through the modulator 60.
As an alternative to the proton bombarded regions 57 which were used in Figure 11 to provide optical absorpt;on, some devices can effectively utilize profiling plus crystal growth techniques to provide the required optical absorption in both confining layers. This is illustrated in Figure 12 using the same referencesas in Figure 11 where applicable. In this case, up-standing ridges 51 provide optical absorption in the ~irst confining layer while inverted ridges 62 provide optical absorption in the second confining layer. In such an arrangement ~he capping layer 55 is not optional and would have properties the same as substrate 50, that is, be essentially GaAs (with little or no Al content). This would ensure absorption of photons B provided the guiding or active layer 53 is of GaAlAs, for example 30 GaO gAlo lAs. ;~ -In addition to the integrated emitter-modulator ~S6043 devices discussed previously, the inventions are applicable to many discrete optoelectronic devices such as LED's, laser, -modulators and detectors. Diagrammatic cross-sections are shown in Figures 13 and 14 for the cases of optical barriers introduced by the techniques of proton bombardment and crystal growth, respectively. In each case a well-defined active or guiding layer is defined which provides those advantages discussed previously.
In these devices, the structure comprises a substrate 63 with a p- or n-type active layer 64 and confining layers 65 and 66 on either side o~ the active layer. A capping layer 67 is on top of confining layer 66. Substrate and first confining layer are typically n-type while second confining layer and capping layer are of p-type. Precise definition of the active layer is provided at the exit facets at 68 by proton bombardment in Figure 13 ~;
and at 69 by crystal growth in Figure l4.
i~ : .
, .
;~
:;
. . .. . . . . . .
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:-
1. An optoelectronic device comprising a heterostructure having an active layer of semiconductor material sandwiched between first and second confining layers of semiconductor material, the confining layers of opposite conduct-ivity type relative to each other and the active layer of the opposite conductivity type relative to one of said confining layers to form a p-n junction therebetween, and at least one barrier of high photon absorption material in at least one of said confining layers, to reduce the propagation of light in the said at least one confining layer.
2. A device as claimed in claim 1, including a substrate of semiconductor material of a first conductivity type, said first confining layer on a surface of said substrate and of the same conductivity type as said substrate, said active layer formed on said first confining layer and said second confining layer on said active layer, said barrier extending at least through said second confining layer to said active layer.
3. A device as claimed in claim 1, comprising:-a substrate of semiconductive GaAs material of a first conductivity type;
a first confining layer of GaAlAs semiconductor material on said substrate and of the same conductivity type as said substrate;
an active layer of GaAl semiconductor material on said first confining layer;
a second confining layer of GaAlAs semiconductor material on said active layer and of a second conductivity type;
said active layer of a conductivity type the same as one of said first and second confining layers to form a p-n junction therebetween;
a photon barrier of high photon absorbing material in each of said first and second confining layers, said barriers in alignment to reduce light propagation in said confining layers.
a first confining layer of GaAlAs semiconductor material on said substrate and of the same conductivity type as said substrate;
an active layer of GaAl semiconductor material on said first confining layer;
a second confining layer of GaAlAs semiconductor material on said active layer and of a second conductivity type;
said active layer of a conductivity type the same as one of said first and second confining layers to form a p-n junction therebetween;
a photon barrier of high photon absorbing material in each of said first and second confining layers, said barriers in alignment to reduce light propagation in said confining layers.
4. A device as claimed in claim 3, including two photon barriers in said second confining layer, said two photon barriers spaced apart in the direction of light propagation in said active layer.
5. A device as claimed in claim 4, said device including two sections in optical series, said barriers at each end of said device, and including a further photon barrier in said second confining layer at the junction of said two sections.
6. A device as claimed in claim 5, said device a monolithic light emitting diode and modulator, said active layer common to both said diode and said modulator.
7. A device as claimed in claim 4, comprising a plurality of sections in optical series, a photon barrier in said second confining layer at each end of the device and a photon barrier in said second confining layer between each said section.
8. A device as claimed in claim 4, including two photon barriers in said first confining layer, a barrier in said first confining layer aligned with each barrier in said second confining layer.
9. A device as claimed in claim 4, wherein each photon barrier is a proton bombarded region.
10. A device as claimed in claim 4, including a capping layer of GaAs semiconductor material on said second confining layer, said photon barrier comprising regions of said capping layer extending through said second confining layer to said active layer.
11. A device as claimed in claim 8, said photon barrier in said first confining layers comprising regions of said substrate extending through said first confining layer to said active layer.
12. A device as claimed in claim 8, including apertures extending through said substrate aligned with said photon barriers in said first confining layer, said photon barriers in said first confining layer being a proton bombarded region.
13. A device as claimed in claim 12, including a proton bombarded layer on the walls of said apertures.
14. A method of producing an optoelectronic device, comprising:
forming a first confining layer of semiconductor material on a substrate of semiconductor material, said confining layer and said substrate of the same conductivity type;
forming an active layer of semiconducting material on said first confining layer and forming a second confining layer on said active layer, said second confining layer of opposite conductivity type to said first confining layer and said active layer of the same conductivity type as one of said confining layers;
proton bombarding at least one region in said second confining layer, to form a photon absorbing barrier therein.
forming a first confining layer of semiconductor material on a substrate of semiconductor material, said confining layer and said substrate of the same conductivity type;
forming an active layer of semiconducting material on said first confining layer and forming a second confining layer on said active layer, said second confining layer of opposite conductivity type to said first confining layer and said active layer of the same conductivity type as one of said confining layers;
proton bombarding at least one region in said second confining layer, to form a photon absorbing barrier therein.
15. A method as claimed in claim 14, including proton bombarding at least one region in said first confining layer to form a photon absorbing barrier.
16. A method as claimed in claim 15, including etching at least one aperture through said substrate to said first confining layer, and proton bombarding said first confining layer through said aperture.
17. A method as claimed in claim 14, further comprising:
etching one surface of the substrate of semi-conductor material to produce at least one protrusion extending normal to said surface of said substrate; and forming said first confining layer on said substrate, said layer extending over said protrusion, said protrusion forming a photon absorbing barrier.
etching one surface of the substrate of semi-conductor material to produce at least one protrusion extending normal to said surface of said substrate; and forming said first confining layer on said substrate, said layer extending over said protrusion, said protrusion forming a photon absorbing barrier.
18. A method as claimed in claim 17, including etching said second confining layer to form at least one aperture extending to said active layer, and forming a capping layer of semiconductive material on said second confining layer of the same conductivity type as said second confining layer, said capping layer extending into said aperture and forming a photon absorbing barrier.
19. A method as claimed in claim 17, including forming a plurality of spaced apart protrusions on said substrate.
20. A method as claimed in claim 14, including proton bombarding at least one region in said first confining layer to form a photon absorbing barrier in said first confining layer.
Priority Applications (9)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA254,255A CA1056043A (en) | 1976-06-07 | 1976-06-07 | Optoelectronic devices with control of light propagation |
| GB11617/77A GB1578638A (en) | 1976-06-07 | 1977-03-18 | Optoelectronic devices with control of light propagation |
| IT21941/77A IT1076300B (en) | 1976-06-07 | 1977-03-31 | ORTHO-ELECTRONIC DEVICES WITH LIGHT PROPAGATION CONTROL |
| NL7703509A NL7703509A (en) | 1976-06-07 | 1977-03-31 | OPTICAL-ELECTRONIC DEVICES EQUIPPED WITH CONTROL OF LIGHT PROPAGATION. |
| DE19772716749 DE2716749A1 (en) | 1976-06-07 | 1977-04-15 | OPTOELECTRONIC DEVICE WITH CONTROL OF LIGHT PROPAGATION |
| JP5715777A JPS5319843A (en) | 1976-06-07 | 1977-05-19 | Optooelectronic element for suppressing light transmission and method of producing same |
| FR7717285A FR2354637A1 (en) | 1976-06-07 | 1977-06-06 | OPTOELECTRONIC DEVICE EQUIPPED WITH LIGHT PROPAGATION CONTROL MEANS, AND THEIR MANUFACTURING PROCESS |
| ES459549A ES459549A1 (en) | 1976-06-07 | 1977-06-07 | Optoelectronic devices with control of light propagation |
| SE7706624A SE7706624L (en) | 1976-06-07 | 1977-06-07 | OPTOELECTRONIC DEVICE AND KIT FOR ITS MANUFACTURE |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA254,255A CA1056043A (en) | 1976-06-07 | 1976-06-07 | Optoelectronic devices with control of light propagation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056043A true CA1056043A (en) | 1979-06-05 |
Family
ID=4106155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,255A Expired CA1056043A (en) | 1976-06-07 | 1976-06-07 | Optoelectronic devices with control of light propagation |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5319843A (en) |
| CA (1) | CA1056043A (en) |
| DE (1) | DE2716749A1 (en) |
| ES (1) | ES459549A1 (en) |
| FR (1) | FR2354637A1 (en) |
| GB (1) | GB1578638A (en) |
| IT (1) | IT1076300B (en) |
| NL (1) | NL7703509A (en) |
| SE (1) | SE7706624L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5845736U (en) * | 1981-09-21 | 1983-03-28 | 不動建設株式会社 | Hollow pipes for creating sand piles, etc. |
| JPS58164814A (en) * | 1982-03-25 | 1983-09-29 | Fudo Constr Co Ltd | Sand pile formation work |
| JPS5845737U (en) * | 1981-09-22 | 1983-03-28 | 不動建設株式会社 | Hollow pipes for creating sand piles, etc. |
| JPS59203117A (en) * | 1983-05-02 | 1984-11-17 | Fudo Constr Co Ltd | Method and apparatus for improvement of soft ground |
-
1976
- 1976-06-07 CA CA254,255A patent/CA1056043A/en not_active Expired
-
1977
- 1977-03-18 GB GB11617/77A patent/GB1578638A/en not_active Expired
- 1977-03-31 IT IT21941/77A patent/IT1076300B/en active
- 1977-03-31 NL NL7703509A patent/NL7703509A/en not_active Application Discontinuation
- 1977-04-15 DE DE19772716749 patent/DE2716749A1/en active Pending
- 1977-05-19 JP JP5715777A patent/JPS5319843A/en active Pending
- 1977-06-06 FR FR7717285A patent/FR2354637A1/en not_active Withdrawn
- 1977-06-07 ES ES459549A patent/ES459549A1/en not_active Expired
- 1977-06-07 SE SE7706624A patent/SE7706624L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| FR2354637A1 (en) | 1978-01-06 |
| GB1578638A (en) | 1980-11-05 |
| NL7703509A (en) | 1977-12-09 |
| DE2716749A1 (en) | 1977-12-15 |
| SE7706624L (en) | 1977-12-08 |
| JPS5319843A (en) | 1978-02-23 |
| IT1076300B (en) | 1985-04-27 |
| ES459549A1 (en) | 1978-11-16 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |
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