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Reliability and Performance of Pseudomorphic Ultraviolet Light Emitting Diodes on Bulk Aluminum Nitride Substrates

Published online by Cambridge University Press:  31 January 2011

Shawn R. Gibb
Affiliation:
gibb@crystal-is.com, Crystal IS Inc., Green Island, New York, United States
James R. Grandusky
Affiliation:
gibb@crystal-is.com, Crystal IS Inc., Green Island, New York, United States
Yongjie Cui
Affiliation:
grandusky@crystal-is.com, Crystal IS Inc., Green Island, New York, United States
Mark C. Mendrick
Affiliation:
cui@crystal-is.com, Crystal IS Inc., Green Island, New York, United States
Leo J. Schowalter
Affiliation:
mendrick@crystal-is.com, Crystal IS Inc., Green Island, New York, United States
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Abstract

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 AlxGa1-xN (x∼70%) 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.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

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