Selectively etchable heterogeneous composite distributed Bragg reflector
View Patent ↗DBR mirrors, and vertical cavity surface emitting lasers that incorporate such mirrors, comprised of stacked, multiple levels of different materials having different etching rates for a selected etchant and etching method. Such DBRs are fabricated by etching an upper level(s) down to a lower level(s) to form a pillar or trenched structure, beneficially having an aperture, that has predetermined optical characteristics. When part of a vertical cavity surface emitting laser, a lower level can include an ion-implanted region that optionally extends into an active region and into a bottom DBR.
1. A Vertical Cavity Surface Emitting Laser, comprising:
a substrate;
an active region over said substrate, said active region for emitting light at a predetermined wavelength;
a bottom distributed Bragg reflector mirror disposed between said active region and said substrate, said bottom distributed Bragg reflector mirror for reflecting light emitted by said active region back to said active region; and
a top distributed Bragg reflector mirror adjacent said active region, said top distributed Bragg reflector mirror for reflecting light emitted by said active region back to said active region, wherein said top distributed Bragg reflector mirror has both a first level and a second level that partially extends over, and is adjacent to, said first level with no intervening layers;
wherein said first level is comprised of a first set of materials;
wherein said second level is comprised of a second set of materials;
wherein said first set of materials and said second set of materials have significantly different etch rates for a selected etchant and etching method;
wherein a combination of said first level and of said second level produces a predetermined reflection characteristic; and
wherein said first level includes an ion-implanted region.
2. A Vertical Cavity Surface Emitting Laser according to claim 1 , wherein said first level is comprised of a material combination selected from a group consisting of AlGaInAs, AlInAs, InGaAsP, and lnP, and combinations thereof.
3. A Vertical Cavity Surface Emitting Laser according to claim 1 , wherein said second level is comprised of a material combination selected from a group consisting of AlGaAs and AlGaAsSb, and combinations thereof.
4. A Vertical Cavity Surface Emitting Laser according to claim 1 , wherein said second level is comprised of an oxidized material.
5. A Vertical Cavity Surface Emitting Laser according to claim 1 , wherein said second level includes an aperture.
6. A Vertical Cavity Surface Emitting Laser according to claim 1 , further including an electrical contact.
7. A Vertical Cavity Surface Emitting Laser according to claim 1 , further including a bottom contact.
8. A method of fabricating a Vertical Cavity Surface Emitting Laser, comprising:
forming a bottom distributed Bragg reflector mirror on a substrate;
forming an active region on the bottom distributed Bragg reflector mirror; and
forming a top distributed Bragg reflector mirror on the active region, wherein the top distributed Bragg reflector mirror is formed by:
growing a first level of a first material combination over the active region, wherein the first material has first optical properties and a first etching rate to a selected etchant;
forming an ion-implanted region in said first level;
growing a second level of a second material combination adjacent to the first level with no intervening layers, wherein the second material has second optical properties and a second etching rate to the selected etchant, wherein the second etching rate is substantially greater than the first etching rate;
masking the second level; and
etching the second level using the selected etchant such that a pillar of the second material is formed and such that the first level acts as an etch stop.
9. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 8 , further including the step of forming a top contact.
10. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 8 , further including the step of forming an aperture in the second level.
11. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 8 , wherein the first material combination is selected from a group consisting of AlGaInAs, AlInAs, InGaAsP, and InP, and combinations thereof.
12. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 8 , wherein the second material combination is selected from a group consisting of AlGaAs and AlGaAsSb, and combinations thereof.
13. A Vertical Cavity Surface Emitting Laser according to claim 8 , wherein said second material is comprised of an oxidized material.
14. A method of fabricating a Vertical Cavity Surface Emitting Laser, comprising:
forming a bottom distributed Bragg reflector mirror on a substrate;
forming an active region on the bottom distributed Bragg reflector mirror; and
forming a top distributed Bragg reflector mirror on the active region, wherein the top distributed Bragg reflector mirror is formed by:
growing a first level of a first material combination over the top active region, wherein the first material has first optical properties and a first etching rate to a selected etchant;
growing a second level of a second material combination adjacent to the first level, wherein the second material has second optical properties and a second etching rate to the selected etchant, wherein the second etching rate is substantially greater than the first etching rate;
masking the second level;
etching the second level using the selected etchant such that a confined region defined by trenches is formed and such that the first level acts as an etch stop; and
forming an aperture in said second level.
15. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 14 , further including the step of forming an ion-implanted region in the first level.
16. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 14 , further including the step of forming a top contact.
17. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 14 , wherein the first material combination is selected from a group consisting AlGaInAs, AlInAs, InGaAsP, InP, and combinations thereof.
18. A method of fabricating a Vertical Cavity Surface Emitting Laser according to claim 14 , wherein the second material combination is selected from a group consisting of AlGaAs and AlGaAsSb, and combinations thereof.
19. The Vertical Cavity Surface Emitting Laser as recited in claim 1 , wherein said first level includes an optical aperture.
20. The Vertical Cavity Surface Emitting Laser as recited in claim 1 , wherein said second level includes an optical aperture that comprises an oxidized layer.
21. The Vertical Cavity Surface Emitting Laser as recited in claim 1 , wherein said second level includes an optical aperture that comprises an air gap.
22. A VCSEL manufactured according to the method of claim 8 .
23. A VCSEL manufactured according to the method of claim 14 .
24. A Vertical Cavity Surface Emitting Laser, comprising:
a substrate;
an active region over said substrate, said active region for emitting light at a predetermined wavelength;
a bottom distributed Bragg reflector mirror disposed between said active region and said substrate, said bottom distributed Bragg reflector mirror for reflecting light emitted by said active region back to said active region; and
a top distributed Bragg reflector mirror adjacent said active region, said top distributed Bragg reflector mirror for reflecting light emitted by said active region back to said active region, wherein said top distributed Bragg reflector mirror has both a first level and a second level that partially extends over, and is adjacent to, said first level;
wherein said first level is comprised of a first set of materials;
wherein said second level is comprised of a second set of materials;
wherein said first set of materials and said second set of materials have significantly different etch rates for a selected etchant and etching method;
wherein a combination of said first level and of said second level produces a predetermined reflection characteristic; and
wherein said second level includes an aperture.