Crystal IS Inc.

Green Island, NY, United States

Crystal IS Inc.

Green Island, NY, United States

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Grandusky J.R.,Crystal IS Inc. | Gibb S.R.,Crystal IS Inc. | Mendrick M.C.,Crystal IS Inc. | Schowalter L.J.,Crystal IS Inc.
Applied Physics Express | Year: 2010

High quality bulk aluminum nitride substrates were used to obtain pseudomorphic AlxGa1-xN layers with low dislocation density, smooth surfaces, and high conductivity. These layers were fabricated into mid-ultraviolet light emitting diodes with peak wavelengths in the range of 240-260 nm. The low dislocation density of the pseudomorphic quantum wells resulted in improved performance over previously published data. The output powers of the on-wafer measurements were greater than 5mW in continuous wave operation, and 16mW in pulsed operation. This was achieved utilizing single die (with an active area of 1 x 10-3 cm2). © 2010 The Japan Society of Applied Physics.


Gibb S.R.,Crystal IS Inc. | Grandusky J.R.,Crystal IS Inc. | Cui Y.,Crystal IS Inc. | Mendrick M.C.,Crystal IS Inc. | Schowalter L.J.,Crystal IS Inc.
Materials Research Society Symposium Proceedings | Year: 2010

Low dislocation density epitaxial layers of AlxGa1-xN can be grown pseudomorphically on c-face AlN substrates prepared from high quality, bulk crystals. Here, we will report on initial characterization results from deep ultraviolet (UV) light emitting diodes (LEDs) which have been fabricated and packaged from these structures. As reported previously, pseudomorphic growth and atomically smooth surfaces can be achieved for a full LED device structure with an emission wavelength between 250 nm and 280 nm. A benefit of pseudomorphic growth is the ability to run the devices at high input powers and current densities. The high aluminum content AlxGa 1-xN (x∼0.7) epitaxial layer can be doped n-type to obtain sheet resistances < 200 Ohms/sq/μm due to the low dislocation density. Bulk crystal growth allows for the ability to fabricate substrates of both polar and non-polar orientations. Non-polar substrates are of particular interest for nitride growth because they eliminate electric field due to spontaneous polarization and piezoelectric effects which limit device performance. Initial studies of epitaxial growth on non-polar substrates will also be presented. © 2010 Materials Research Society.


Gibb S.R.,Crystal IS Inc. | Grandusky J.R.,Crystal IS Inc. | Mendrick M.,Crystal IS Inc. | Schowalter L.J.,Crystal IS Inc.
International Journal of High Speed Electronics and Systems | Year: 2011

Low dislocation density pseudomorphic epitaxial layers of Al xGa 1-xN have been grown on c-face AlN substrates prepared from high quality bulk crystals. As reported previously, pseudomorphic growth yields very low dislocation density layers with atomically smooth surfaces throughout the active region of a full LED device structure. An advantage of the low dislocation density is the ability to n-type dope the high aluminum content Al xGa 1-xN (x ∼ 70%) epitaxial layers required for UVLED devices to obtain sheet resistances less than 350 Ohm/square for 0.5 μm thick layers. Here, we report on the characterization of our pseudomorphic epitaxial AlGaN layers via cathodoluminescence (CL) and on-wafer and initial packaged level characterization of fully fabricated pseudomorphic ultraviolet LEDs (PUVLEDs) with an emission wavelength between 250 - 265 nm. An additional benefit of PUVLED devices is the ability to run these devices at high input powers and current densities. Further, the aforementioned low dislocation density of the epitaxial structure results in improved device performance over previously published data. Mean output powers of greater than 4 mW were obtained on-wafer prior to thinning and roughening while output powers as high as 45 mW were achieved for packaged devices. © 2011 World Scientific Publishing Company.


Grandusky J.R.,Crystal IS Inc. | Gibb S.R.,Crystal IS Inc. | Mendrick M.C.,Crystal IS Inc. | Moe C.,U.S. Army | And 2 more authors.
Applied Physics Express | Year: 2011

This letter reports on the improved performance of a pseudomorphic ultraviolet light-emitting diode (LED). At 100mA input current, 9.2mW of quasi-CW output power was measured in a calibrated integrating sphere. The addition of a heat sink, required for CW and higher power operation, introduced a numerical aperture of 0.86, and 72mW was measured in pulsed mode at 1.7 A, indicating that the total output power exceeds 100mW when corrected by the coupling factor. The high characteristic temperature of 983 K was instrumental in achieving these record output powers for an LED with wavelength shorter than 265 nm. © 2011 The Japan Society of Applied Physics.


Chen J.,Crystal IS Inc. | Grandusky J.R.,Crystal IS Inc. | Mendrick M.C.,Crystal IS Inc. | Gibb S.R.,Crystal IS Inc. | Schowalter L.J.,Crystal IS Inc.
2012 Lester Eastman Conference on High Performance Devices, LEC 2012 | Year: 2012

We designed and fabricated 260 nm ultraviolet light emitting diodes that were pseudomorphically grown on AlN substrates. Thinning the substrates, roughening the emission surfaces, and encapsulating contributed to increasing the photon extraction efficiency by more than one order of magnitude. © 2012 IEEE.


Sampath A.V.,U.S. Army | Garrett G.A.,U.S. Army | Readinger E.D.,U.S. Army | Enck R.W.,U.S. Army | And 4 more authors.
Solid-State Electronics | Year: 2010

The optical and structural properties of AlGaN active regions containing nanoscale compositional inhomogeneities (NCI) grown on low dislocation density bulk AlN substrates are reported. These substrates are found to improve the internal quantum efficiency and structural quality of NCI-AlGaN active regions for high Al content alloys, as well as the interfaces of the NCI with the surrounding wider bandgap matrix, as manifested in the absence of any significant long decay component of the low temperature radiative lifetime, which is well characterized by a single exponential photoluminescence decay with a 330 ps time constant. However, room temperature results indicate that non-radiative recombination associated with the high point defect density becomes a limiting factor in these films even at low dislocation densities for larger AlN mole fractions. © 2010 Elsevier Ltd. All rights reserved.


Kim Y.S.,Rensselaer Polytechnic Institute | Lin S.-Y.,Rensselaer Polytechnic Institute | Hsieh M.-L.,National Taiwan Normal University | Schowalter L.,Crystal IS Inc.
2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011 | Year: 2011

Ultra-violet light-emitting diodes (UV-LEDs) fabricated with integrated surface textures show an enhancement of the output power and more directionality of the emitted light, which is in agreement with the calculated results. © 2011 OSA.


Grandusky J.R.,Crystal IS Inc. | Chen J.,Crystal IS Inc. | Gibb S.R.,Crystal IS Inc. | Mendrick M.C.,Crystal IS Inc. | And 5 more authors.
Applied Physics Express | Year: 2013

In this letter, the achievement of over 60mW output power from pseudomorphic ultraviolet light-emitting diodes in continuous wave operation is reported. Die thinning and encapsulation improved the photon extraction efficiency to over 15%. Improved thermal management and a high characteristic temperature resulted in a low thermal rolloff up to 300mA injection current with an output power of 67mW, an external quantum efficiency (EQE) of 4.9%, and a wall plug efficiency (WPE) of 2.5% for a single-chip device emitting at 271nm in continuous wave operation. © 2013 The Japan Society of Applied Physics.


Garrett G.A.,U.S. Army | Sampath A.V.,U.S. Army | Shen H.,U.S. Army | Wraback M.,U.S. Army | And 10 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2010

Temperature dependent time-resolved photoluminescence is used to study the development of active regions for optoelectronic devices employing AlGaN nanostructures for deep-UV emission. The changing importance of dislocation versus point defects and their relationship to different forms of carrier localization are discussed. The results presented suggest that AlGaN nanostructure development for deep-UV emitters require both point defect/impurity suppression for improved efficiency and lower dislocation density for improved interface quality. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Moe C.G.,Crystal IS Inc. | Garrett G.A.,U.S. Army | Grandusky J.R.,Crystal IS Inc. | Chen J.,Crystal IS Inc. | And 4 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

Mid-ultraviolet LEDs grown on AlN substrates with a range of quantum efficiencies and wavelengths spanning 250 to 280 nm have been investigated by time-resolved photoluminescence and electroluminescence. Through scaling of room temperature internal quantum efficiencies across all devices, radiative and nonradiative lifetimes are also estimated. General trends observed include an increase in PL lifetime for longer wavelength and higher external quantum efficiency devices, consistent with the increase in the estimated nonradiative life-time with increasing wavelength. Despite these trends, the external quantum efficiency of the devices increases only weakly with increasing wavelength from 258 to 279 nm, suggesting that optimization of radiative lifetime and injection efficiency also play an important role. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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