Introduction(1)
• AlGaN-based UV LED remain considerably less
efficient than their InGaN-based LED counterparts.
• One of the primary barriers is the low doping
efficiency and carrier mobility of high-Al content
AlGaN, particularly in the p-type material.
• Magnesium, the only successful p-type dopant for
AlGaN used to date, has a very high activation energy
at the desired AlGaN compositions, resulting in
resistive films.
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Introduction(2)
• Most devices use p-GaN as a contact layer, due to
the high work function that would be required to
make an ohmic contact to p-AlGaN with
sufficient aluminum content to be transparent to
the emission wavelength of the LED.
• Because of the large lattice mismatch between
the GaN and high-Al content AlGaN, many LEDs
either the GaN directly on the blocking layer or
insert intermediate p-layers with decreasing Al
content.
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