Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
1999-01-19
2001-05-15
Arroyo, Teresa M. (Department: 2881)
Coherent light generators
Particular active media
Semiconductor
C372S045013
Reexamination Certificate
active
06233267
ABSTRACT:
FIELD OF THE INVENTION
This patent application relates generally to solid state laser devices and, in particular, to a method for fabricating a surface emitting short wavelength semiconductor solid state laser device (e.g., a semiconductor solid state laser device capable of operating in the blue, near ultraviolet (NUV), UV, blue-green or green region of the spectrum), as well as to a laser device fabricated in accordance with the method.
BACKGROUND OF THE INVENTION
Blue/NUV/green semiconductor lasers, based on both Group III-nitride and Group II-VI compound semiconductors, have been realized in a so-called edge emitting geometry, wherein continuous-wave room-temperature diode laser operation was achieved under electrical current injection. There has also been exploratory work that has led to the demonstration of a vertical cavity surface emitting laser (VCSEL), constructed with Group II-VI compounds, that operates under optical pumping. Reference in this regard can be had to a publication entitled “Room-temperature optically pumped blue-green vertical cavity emitting laser”, Appl. Phys. Lett. 67 (12), Sep. 18, 1995, H. Jeon et al., pps. 1668-1670.
These device structures have shown that high quality dielectric mirrors can be implemented as the optical resonator in the blue spectrum for VCSEL structures.
OBJECTS AND ADVANTAGES OF THE INVENTION
It is a first object and advantage of this invention to provide an improved solid state vertical cavity surface emitting laser (VCSEL) device.
It is a second object and advantage of this invention to provide methods for fabricating a vertical cavity, surface emitting laser device capable of operation in the blue, near ultraviolet, ultraviolet, or blue-green or green regions of the optical spectrum, wherein the laser device constructed in accordance with the methods utilizes nitride-based semiconductor materials as the active medium.
It is another object and advantage of this invention to provide a solid state laser device that contains an embedded dielectric distributed Bragg reflector (DBR) mirror structure and that is fabricated using a lateral edge overgrowth (LEO) technique.
It is a further object and advantage of this invention to provide a solid state laser device that creates a confined current by aperture formation using the LEO technique, wherein the current constricting aperture may be placed either below or above an active quantum well optical gain medium.
SUMMARY OF THE INVENTION
The foregoing and other problems are overcome and the objects and advantages are realized by fabrication methods and solid state laser devices in accordance with embodiments of this invention.
Methods are herein described for fabricating a vertical cavity, surface emitting laser device capable of operation in the blue, near ultraviolet, ultraviolet, or blue-green or green regions of the optical spectrum. The laser device constructed in accordance with the methods utilizes nitride-based semiconductor materials as the active medium, and exploits their specific epitaxial crystal growth properties for shaping the electrical and optical energy flow paths. The laser device constructed in accordance with the methods of this invention also embeds high reflectivity dielectric optical mirrors in a monolithic manner within the device structure.
The teachings of this invention exploit recent advances in wide bandgap semiconductor materials, and in the optoelectronic area, to realize a novel type of blue/green and near ultraviolet (NUV) VCSEL device. In a presently preferred, but not limiting, embodiment of this invention the semiconductor materials are Group III nitrides, such as a combination of GaN, and its alloys with InN and AlN (for example, InGaN and AlGaN) having a demonstrated ability to emit light that spans the near ultraviolet, blue, and green parts of the spectrum. In general, the device emits light having a wavelength shorter than about 500 nm. Typically, the device will emit light having a wavelength generally in the range of about 250 nm to about 500 nm (e.g., UV through NUV through blue to green or blue-green).
In one aspect of this invention the laser device contains an embedded dielectric distributed Bragg reflector (DBR) mirror structure that is embedded using a lateral edge overgrowth (LEO) technique.
In another aspect of this invention the laser device creates an embedded confined current by aperture formation using the LEO technique. The current constricting aperture may be placed either below or above an active quantum well optical gain medium.
In one aspect then, this invention provides a vertical cavity, surface emitting laser (VCSEL) device having a substrate and, disposed over a surface of the substrate, a Group III nitride buffer layer and a mesa structure containing at least a portion of an n-type Group III nitride layer. The VCSEL device and mesa structure further include a first multilayer dielectric mirror stack, that is embedded within the first Group III nitride layer by the use of a lateral edge overgrowth (LEO) process; a p-type Group III nitride layer; and a p-n junction between the n-type Group III nitride layer and the p-type Group III nitride layer. The p-n junction contains an active multiquantum well region. Also contained in the mesa structure is a dielectric (silicon dioxide) layer having a current constricting aperture. The dielectric layer and aperture is buried within one of the n-type Group III nitride layer or the p-type Group III nitride layer, also by the use of the lateral edge overgrowth process. A second multilayer dielectric mirror stack is disposed on top of the mesa structure and over the p-type Group III nitride layer. The first and second multilayer dielectric mirror stacks define a resonant optical cavity structure that passes through the aperture. The resonant optical cavity structure supports an emission of about 500 nm or less in the green, blue/green, blue or NUV spectral regions. The VCSEL device further includes a first electrode that surrounds a base of the mesa structure and that is conductively coupled to the first Group III nitride layer, and a second electrode that is conductively coupled to the second Group III nitride layer. The placement of the n-type and p-type nitride layers could be reversed.
Methods for fabricating various embodiments of the VCSEL device, using the LEO process, are also disclosed.
REFERENCES:
patent: 5146465 (1992-09-01), Khan et al.
patent: 5701321 (1997-12-01), Hayafuji et al.
patent: 6046465 (2000-04-01), Wang et al.
Nam, Ok-Hyun et al., “Lateral epitaxy of low defect density GaN layers via organometallic vapor phase epitaxy”, Appl. Phys. Lett. 71 (18), Nov. 3, 1997, pp. 2638-2640.
Jeon, H. et al., “Room-temperature optically pumped blue-green vertical cavity emitting laser”, Appl. Phys. Lett. 67 (12), Sep. 18, 1995, pp. 1668-1670.
Song, Y-K. et al., “Gain characteristics of InGaN/GaN quantum well diode lasers” Appl. Phys. Lett., vol. 72, (12), Mar. 23, 1998, pp. 1418-1420.
Kelkar, P., “Excitons in a II-VI semiconductor microcavity in the strong-coupling regime”, American Physical Society, Physical Review B, vol. 52, No. 8, Aug. 15, 1995, 4 pages pp. R5491-R5494.
Nurmikko Arto V
Song Yoon-Kyu
Arroyo Teresa M.
Brown University Research Foundation
Leung Quyen P.
Ohlandt Greeley Ruggiero & Perle LLP
LandOfFree
Blue/ultraviolet/green vertical cavity surface emitting... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Blue/ultraviolet/green vertical cavity surface emitting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Blue/ultraviolet/green vertical cavity surface emitting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2440550