Solid State Light 
At Rensselaer Polytechnic Institute
|
|
|
Our Patents on
LEDs and Lasers |
|
Mission
Solid
State Lighting Group is established in order to accelerate the
development and commercialization of solid-state lighting technologies.
Members
Prof.
Michael S. Shur
Roberts Professor of Solid
State Electronics and Professor of Physics Room 9017 CII, Rensselaer Polytechnic Institute 110, 8th Street,
Troy, NY 12180 Tel: 518 276 2201 Fax: 518 276 2990 Email: shurm@rpi.edu |
Dr. Remis Gaska
Associate Research Professor ECSE Dept Rensselaer Polytechnic
Institute 110, 8th Street,
Troy, NY 12180 Tel: 518 276 6684 Fax: 518 276 2990 Email: gaskar@rpi.edu |
Prof. Leo J. Schowalter
Professor of Physics Department of Physics Rensselaer Polytechnic
Institute 110, 8th Street,
Troy, NY 12180 Tel: 518 276 6435 Fax: 518 276 6680 Email: schowl@rpi.edu |
Dr. Lionel M. Levinson
(Adjunct Professor, Physics,
RPI) Manager Global Programs Development GE Corporate Research &
Development Building K1, Room MB159, P.O.
Box 8 Schenectady, NY 12301 Tel: 518 387 6332 Fax: 518 387 6204 Email: levinson@crd.ge.com |
Prof. James V. Crivello
Professor of Chemistry Department of Chemistry Rensselaer Polytechnic
Institute 110, 8th Street,
Troy, NY 12180 Tel: 518 276 6825 Fax: 518 276 4045 Email: crivej@rpi.edu |
Dr. N. Narendran
Research Associate Professor Director of Research Lighting Research Center Rensselaer Polytechnic Institute 21 Union Street, Troy, NY 12189 Tel: 518 687 7176 Fax: 518 687 7120 Email: narenn2@rpi.edu |
Prof. Morris A. Washington
Clinical Professor, Physics Rensselaer Polytechnic Institute CII 9019 - CIEEM 110, 8th Street, Troy, NY 12180 Phone: (518) 276-3064 Fax: (518) 276-2990 Email: washim@rpi.edu |
Prof. Glen Slack
Research Professor of Physics Department of Physics Rensselaer Polytechnic
Institute 110, 8th Street,
Troy, NY 12180 Tel: 518 276 6435 Fax: 518 276 6680 Email: schowl@rpi.edu |
Back to the top
Key Research Results
From the
abstracts submitted to SPIE Solid-State Lighting Conference:
Fabrication of Single-Crystal Aluminum Nitride Substrates for Solid
State Lighting Applications*
Leo J. Schowalter,** J. Carlos Rojo, , and Glen Slack,
Crystal IS, Inc., Latham, NY 12110; R. Gaska and M. Shur, Sensor Electronic
Technology, Latham, NY 12110; J. Yang and A. Khan, Electrical Engineering,
Univ. South Carolina, Columbia, SC 29208; D.D. Koleske and R.L. Henry, Naval
Research Laboratory, Washington D.C. 20375
Aluminum nitride (AlN) has received attention as a candidate for
III-nitride epitaxy applications due to its close lattice match, minimal
differential thermal expansion compared to GaN, and high thermal
conductivity. There is interest in AlN
substrates as a competitive substrate for heteroepitaxial growth of GaN until
commercial bulk GaN substrates become available. In addition, AlN is a more desirable substrate than GaN for
device structures that require Al-rich nitride epitaxial layers such as
solar-blind uv detectors, uv light sources and high power microwave
devices.
Large
(15mm diameter) AlN boules have been prepared using sublimation-recondensation
growth. We have demonstrated the possibility of preparing substrates, cut from
these boules, for epitaxial growth using chemical-mechanical polishing (CMP)
techniques, although significant differences between the different
crystallographic orientations have been observed. High quality epitaxial growth
of III-nitrides has been demonstrated on a-face substrates, on the nitrogen
face of c-face substrates when nearly on-axis, and on the aluminum face of
off-axis c-face substrates. When the
nitrogen face of off-axis (more than 10°) c-face substrates were used, a rough surface
morphology resulted even for AlN homoepitaxy.
Quaternary AlInGaN Epilayers and Quantum Structures for Deep
UV Solid-State light Sources
Remis Gaska
Sensor Electronic Technology, Inc., 21 Cavalier Way, Latham,
NY 12110
Michael S. Shur
Rensselaer Polytechnic Institute, Troy NY 12180 and Sensor
Electronic Technology, Inc.
Jianping Zhang, Jinwei Yang, Grigory Simin, and Asif Khan.
University of South Carolina, Dept. of Electrical
Engineering, Columbia, SC 29208
We present our recent results on the growth of quaternary
AlInGaN material lattice matched to GaN over sapphire substrates. By changing
Al/In flow ratio during the material growth, we obtained the AlInGaN layers
with strong PL peaks spanning from 290 nm to 350 nm. The intensity of the PL
peaks does not decrease when the Al fraction increases in the quaternary
material, in contrast to AlGaN layers known to exhibit a significant decrease
of the emission efficiency as the Al fraction increases. This implies that
quaternary AlInGaN layers are much more suitable for UV lighting sources. We
use Rutherford Backscattering spectrometry (RBS) to analyze the quaternary
composition and Atomic Force Microscopy (AFM) to check the sample morphology.
We have found that even for an epilayers up to 0.3 micron thick with the
highest Al fraction (PL emission peak at 290 nm), there were no cracks in the
wafer.
We also demonstrate a quaternary AlInGaN/AlInGaN multiple quantum
well (MQW) structure, which shows a very strong room temperature emission at
320 nm. The high quality of this quaternary MQW was verified by the XRD rocking
curve, where the satellite peaks are well resolved. The intensity of the 320 nm UV emission from the quaternary MQW
is comparable to that of the blue emission from conventional InGaN/InGaN
MQW. This makes quaternary
AlInGaN/AlInGaN MQW LEDs very attractive for solid-state lighting applications.
Keywords: LED fabrication improvement, light extraction.
High power
GaN/InGaN based light emitting diodes for solid-state lighting applications
Asif Khan,
Maxim Shatalov, Jinwei Yang, Durga Basak, Ashay Chitnis, Kirill Simin, Grigory
Simin,
University of
South Carolina, Dept. of Electrical Engineering, 301 S. Main St., Columbia, SC
29208, tel. (803) 777-7941, Fax (803) 777-2447, e-mail: asif@engr.sc.edu
Remis Gaska
Sensor
Electronic Technology, Inc., Latham, NY 12110
Michael Shur
Rensselaer
Polytechnic Institute, Troy NY 12180 and Sensor Electronic Technology, Inc.
One of the key
problems of modern solid-state white light sources is relatively low luminous
efficiency (typically about 20 lm/W) compared to incandescent lamps (about 100
lm/W). Major limitations come from the efficiency of light-emitting diodes
(LED) pumping the phosphor. This efficiency, in turn, depends on extraction
efficiency and internal quantum efficiency of LED. Optimization of the device
design and epitaxial layers growth conditions allowed us to develop GaN/InGaN
based multiple quantum well LED structures with high external quantum
efficiency emitting in violet/blue spectral region. In commercially available
LEDs, the external quantum efficiency has a maximum at very low currents
(typically less than 10mA) and than reduces by 2 - 3 times at 100 mA under
pulse pumping. In contrast to these LEDs, our devices exhibit no significant
current dependence of external quantum efficiency at pulse currents from 10 mA
up to 1 A. This approach allows obtaining efficient high power devices providing
higher external quantum efficiency and capable to operate at high pumping
current. The analysis of external and internal quantum efficiencies as well as
the study of coupling efficiency between the chip and phosphor will be
presented. Enhanced performance of these devices at high power level makes them
very attractive to use as the high brightness light sources for high power/high
brightness solid-state lighting applications.
Keywords: LED fabrication improvement, light extraction.
Optimization of
Multichip White Solid-State Lighting Source with Four or More LEDs
Arturas Zukauskas, Felikas Ivanauskas, Rimantas Vaicekauskas,
Michael S. Shur and Remis Gaska, SET, Inc.
Creating of a viable
source of white light is the ultimate goal of solid-state lighting technology.
As any illuminant, such source is characterized by two parameters, color
rendering index and luminous efficiency that involve design trade-offs. The standard approaches to white solid
lighting applications use phosphor conversion or multichip LEDs that emit three
primary colors. However, phosphor
conversion might reduce luminous efficiency and might lead to additional
problems related to phosphor degradation.
The second approach of using multichip trichromatic LEDs results in a
poor color rendering because of narrow emission lines. In this paper, we exploit an idea that the
color rendering might be significantly improved by using four and more LEDs
with different emission wavelengths. We
report on modeling results that allowed us, for the first time, to find the
optimum emission wavelengths and relative intensities for four and more LEDs in
a solid-state multichip source of white light.
We also established a procedure for the trade-off between the luminous
efficiency and color-rendering index.
Our results point out to feasibility of a white polychromatic
solid-state source with characteristics improved in comparison with the trichromatic
LED multichip.
See also:
Our Publications on LEDs and Lasers
- Asif Khan, Maxim Shatalov, Jinwei Yang, Durga Basak, Ashay
Chitnis, Kirill Simin, Grigory Simin, Remis Gaska and Michael Shur, High
power GaN/InGaN based light emitting diodes for solid-state lighting
applications, submitted to SPIE conference on Solid State Lighting
- Remis Gaska, Michael S. Shur, Jianping Zhang, Jinwei Yang, Grigory
Simin, and Asif Khan Quaternary AlInGaN Epilayers and Quantum Structures
for Deep UV Solid-State light Sources, submitted to SPIE conference on
Solid State Lighting
- Leo J. Schowalter,*J. Carlos Rojo, , and Glen Slack, R. Gaska and Shur, J. Yang and A. Khan, Fabrication of Single-Crystal Aluminum Nitride Substrates for Solid State Lighting Applications, submitted to SPIE conference on Solid State Lighting
- Arturas Zukauskas, Felikas Ivanauskas, Rimantas Vaicekauskas,
Michael S. Shur, and Remis Gaska, Optimization of Multichip White
Solid-State Lighting Source with Four or More LEDs, submitted to SPIE
conference on Solid State Lighting
- B. Gelmont and M. S. Shur, Low Threshold Laser Utilizing Junction
Between Two-Dimensional Electron Gas and p-type Semiconductor, in Proceeding of The First International
Semiconductor Device Research Symposium, pp. 193-196, Charlottesville, VA,
Dec. (1991)
- M. Shatalov, A. Chitnis, V. Adivarahan,
A. Lunev, J. Zhang, J. W. Yang, G. Simin,
M. Asif Khan, R. Gaska and M. S. Shur High-Current
Operation of InGaN Multiple Quantum Well Light Emitting Diodes with
Quaternary AlInGaN barriers, to be published
- A. Chitnis, A. Kumar, M. Shatalov, V. Adivarahan, A. Lunev, J. W.
Yang, G. Simin, M. Asif Khan, R. Gaska and M. S. Shur, High-Quality p-n
Junctions With Quaternary AlInGaN Quantum Wells
- G. Tamulaitis, S. Juršėnas, K. Kazlauskas,
A. Žukauskas, M. Asif Khan, J. W. Yang,
G. Simin, R. Gaska, M. S. Shur, Strain Energy Band
Engineering for Band Gap Shaping in AlInGaN Alloys
- M. A. Khan, M.A.; Adivarahan, V.; Shatalov, M.; Lunev, A.; Yang,
J.W.; Simin, G.; Gaska, R.; Shur, M.S. Quaternary AlInGaN based
vertically conducting light emitting diodes on SiC, Device
Research Conference, 2000. Conference Digest. 58th DRC , 2000 Page(s): 123 –124
- A. Žukauskas, G. Tamulaitis, R. Gaska and
M. S. Shur, Materials for Semiconductor Lighting Applications, ISSN
1392-1320 Materials Science (MEDŽIAGOTYRA). Vol. 6, No. 3, pp. 125-130
(2000)
- J. W. Yang, A. Lunev, G. Simin, A. Chitnis, M.
Shatalov and M. Asif Khan, J. E. Van
Nostrand, R. Gaska, "Selective area deposited blue GaN-InGaN
multiple-quantum well light emitting diodes over silicon substrates",Appl. Phys. Lett. 76 (3), pp. 273-275 (2000)
- A. A. Tager, R. Gaska, I. A. Avrutsky, M. Fay, H. Chik, A.
Springthorpe, Z. Husain, J. M. Xu, and M. S. Shur, Ion Implanted
GaAs/InGaAs lateral Injection Ridge QW Laser for OEICs: Study of Operation
Mechanisms, in Proceedings of IEEE Twenty fourth International Symposium
on Compound Semiconductors, Institute Phys. Conference Series, IOP
Publishing, Bristol and Philadelphia (1998), pp. 387-390
- J. Zhang, J. Yang, G. Simin and M. Asif Khan,
M. S. Shur and R. Gaska, Enhanced Luminescence in InGaN Multiple Quantum
Wells with Quaternary AlInGaN Barriers, to be published
- C. J. Sun, M. Zubair Anwar, Q. Chen, J. W. Yang and M. A. Khan, M.
S. Shur, A. D. Bykhovski, H. Temkin, Quantum Shift of Band Edge Stimulated
Emission in InGaN-GaN Multiple Quantum Well Light Emitting Diodes, Appl.
Phys. Lett. 70 (22), pp. 2978-2980, June 2 (1997)
- M. A. Khan and M. S. Shur, Recent Progress in
AlGaN/GaN Based Optoelectronic Devices, in Proceedings of SPIE - The
International Society for Optical Engineering, Vol. 3006, Optoelectronics
Integrated Circuits, Yoon-Soo Park and Ramu V. Ramaswamy, Editors, (1997),
pp. 154-163
- G. L. Tan, J. M. Xu, and M. S. Shur, A GaAs/AlGaAs
Double-Heterojunction Lateral PIN Ridge Waveguide Laser, Optical
Engineering, 32, No. 9, pp. 2042-2045, 1993 (Invited)
- M. A. Khan, Q. Chen, J. W. Yang, C. J. Sun, B. Lim, M. Z. Anwar,
M. Blasingame, M. S. Shur and H. Temkin, GaN-InGaN Based Optoelectronic
Devices, in Proceedings of Workshop on Blue Light Emitting Diodes and
Lasers, Chiba, Japan, March (1996)
- M. A. Khan, Q. Chen, J. Yang, C. J. Sun, B. Lam, H. Temkin, J.
Schetzina, and M. S. Shur, UV, Blue And Green Light Emitting Diodes Based
On GaN-InGaN Multiple Quantum Wells Over Sapphire and (111) Spinel
Substrates, Materials Science and Engineering, B43, pp. 265-268 (1997)
- M. A. Khan, Q. Chen, J. Yang, C. J. Sun, B. Lam, M. Z. Anwar, M.
S. Shur, H. Temkin, B. T. Dermott, J. A. Higgins, J. Burm, W. Schaff, and
L. F. Eastman, Visible Light Emitters, Ultraviolet Detectors, and
High-Frequency Transistors Based on III-N Alloys, (Invited.) The Physics
of Semiconductors ed. by M. Scheffler and R. Zimmermann, pp. 3171-3178
(World Scientific, Singapore 1996)
Our Patents on LEDs and Lasers
J. Xu, M. S. Shur, and M.
Sweeny, Electronic and optoelectronic devices utilizing light hole properties,
United States Patent, #4,899,201, February 6 (1990)
M. S. Shur, Modulation Doped
Radiation Emitting Device, United States Patent 4,905,059, Feb. 27 (1990))
J. Xu, M. S. Shur, and M.
Sweeny, Electronic and Optoelectronic Laser Devices Utilizing Light Hole
Properties, United States Patent, # 4,999,682, March 12 (1991)
J. M. Xu, M. S. Shur, and B.
L. Gelmont, Semiconductor Ridge Waveguide Laser with Lateral Current Injection,
United States Patent #5563902, 10/08/1996
Useful Links
http://nina.ecse.rpi.edu/shur/nitride.htm
http://www.optical-engineer.com/lighting/
Society for Photo-Instrumentation Engineers (SPIE)
Lighting Research Center
at Rensselaer Polytechnic Institute
Sensor Electronic Technology, Inc.
Affiliated Companies
Sensor
Electronic Technology, Inc.
General Electric, Inc.
Facilities
Device Fabrication
The Center for Integrated
Electronics and Electronics Manufacturing at Rensselaer Polytechnic Institute,
is equipped with a 9,500 square foot Microfabrication Clean Room (MCR)
facility. Of this, 5,700 square feet is certified as Class 100. A semiconductor
fabrication facility must minimize airborn particles that can disturb the
submicron etching processes, and render the resulting semiconductor unreliable.
The MCR facility is used to
fabricate silicon and compound semiconductor structures, devices, and circuits
with submicron feature sizes. Baseline silicon processes for NMOS and CMOS are
utilized on a regular basis as the vehicles for Microelectronic Manufacturing
Laboratory courses, and to provide researchers with the capability of materials
research within existing integrated processes. Special emphasis is given to
processes for novel planarization and metalization as used with multi-level
metal systems for both chip and packaging module fabrication.
The Microfabrication
facility is equipped with tools that can handle 3" or 5" wafers. Many
tools have also been modified to enable the processing of non-standard
substrate sizes and shapes commonly found in compound semiconductor research
applications. The equipment base is comparable with an industrial semiconductor
fabrication operation.
A comprehensive capability
for measurement and characterization of devices, circuits and materials is
available within the Clean Room environment. Extended capability exists within
other CIEEM affiliated laboratories at RPI for substantial characterization and
analysis.
Occupying a three floor wing
of the Rensselaer Center for Industrial Innovation (CII), the facility has been
constructed to be adaptable to the changing needs of semiconductor processing
and microfabrication. Dedicated support systems have been provided, including
air handling, de-ionized water, toxic and non-toxic gas distribution systems,
equipment cooling water, process vacuum, compressed air, and all exhaust and
liquid effluent is treated within the facility to meet locally mandated
standards (that include scrubbing and neutralization).
A comprehensive monitoring
system oversees the basic operation of the environmental and safety systems. A
sophisticated interface exists to warn of a facility malfunction, or of
hazardous situations such as toxic gas leakage or exhaust failure. All lithographic
and metrology areas of the Microfabication Facility are vibration isolated from
the main construction to enable the highest possible precision and accuracy.
Within the Microfabrication Clean Room, silicon and compound semiconductor structures, devices and circuits are fabricated as well as thin film packaging structures. Integrated NMOS and CMOS processes are available. Line widths as low as 0.8 micrometer can be obtained with the currently available photolithography and etching equipment base. In affiliated laboratories, materials work with GaAs and other compound semiconductors is undertaken, as well as with many other semiconductor oriented materials and processes. Within the microfabrication facility, a full range of physical and parametric measurements are available.
High Temperature Crystal-growth Furnaces
Rensselaer has acquired a high-temperature
furnace, from Thermal Technologies, that will allow us to grow AlN crystals at
temperatures up to 2400 °C and at pressure ranging from 0.1 atmospheres to
15 atmospheres. There are several
special aspects to this furnace including special care to avoid oxygen and
metal contamination and to provide a sharp and controllable temperature
gradient between the source and the growing crystal. Delivery on this unit is expected in April 1999. This unit is being acquired on DURIP funds
from the Office of Naval Research. In
addition, we already have in operation an Arthur D. Little (ADL) Crystal
growth furnace with a 60 kW rf power supply from GE. This furnace is capable of achieving temperatures up to 2700 °C and
total pressure varying from 0.1 bar up to 100 kbar (10 kPa to 10 MPa). While programming precise thermal gradients
is more difficult with this system, it will allow us to explore the effects of
high pressure on formation of point defects in the bulk AlN crystals.
Atomic Force Microscopy
We will make use of a D3100 Scanning Probe
Microscope from Digital Instruments. We
have already demonstrated that this instrument is capable, after proper surface
preparation, of identifying defects (such as dislocations and planar defects)
which intersect the surface of the crystal and has also been used to image
surface topology down to atomic steps.
Crystal Preparation and Polishing Facility
We have also acquired crystal orientation (Laue
x-ray), cutting (high-speed annular saw) and polishing equipment. This equipment will allow us to cut and
polish AlN samples with different orientations. This is needed to prepare samples for optical and electrical studies
on different orientations and to prepare seed crystals for different
orientations of growth.
Molecular Beam Epitaxy (MBE)/Analysis System
We will make use of the VG Semicon V90 MBE
facility at Rensselaer. This system is
designed for metals and Si MBE. The Si/metal MBE growth chamber presently has
three thermal evaporation sources (Knudsen cells) and 4 electron-beam
evaporation sources which are being used for Si, Ge, Co and Pt deposition.
We have added an in-situ STM to the
preparation/analysis chamber of our MBE system that allows us to make
atomic-resolution images of the doped AlxGa1-xN epitaxial
layers that we grow. This STM is also designed to allow in-situ BEEM
measurements, which allows us to make measurements on metal layers that would
oxidize outside the UHV system. We also
have an STM instrument that we operate outside the MBE system for BEEM
measurements at room temperature and at 77K.
Hot-isostatic Press (HIP)
We will make use of a HIP made by American Isostatic Press which is capable of 2000°C at 2 kbar (200 MPa) pressure. To avoid C contamination during annealing experiments, we have budgeted $20k to build a special sample chamber that will allow us to make sure that the sample is only exposed to clean N2 or to forming gas.
Spectrophotometer and other optical measurements
Optical absorption measurements will be made with a Varian CARY 05. This spectrophotometer can scan between 175nm out to 3,300 nm. We will also have access to an Argon ion laser that operates at 363 nm. This will be used to excite nitrogen vacancy luminescence. An appropriate spectrometer (Spex 403) and a detector will be used to monitor luminescence in the red and near infrared.
M. E. Levinshtein, S. L. Rumyantsev, and M. S. Shur, Editors,
“Properties of Advanced Semiconductor Materials: GaN, AlN, InN, BN, and SiGe“,
John Wiley and Sons, ISBN 0-471-35827-4, New York (2001)
See also http://nina.ecse.rpi.edu/shur/nitride.htm
.