Basic Properties of InGaN and In-rich Group III-Nitrides
 Recent
progress in the growth of InN and In-rich InGaN and InAlN by molecular
beam epitaxy has created high quality, single crystalline material
for the first time. This led to the discovery that the bandgap
of InN was only 0.7 eV [1], and that the range of direct bandgaps
of the Group III-Nitride alloys was the largest of any semiconductor
system, extending from the infrared (InN) to 6.2 eV (AlN).
We are interested in studying the electronic and structural properties
of these relatively unknown materials, which may be useful for
a wide variety of optoelectronic applications, including high
efficiency solar cells and photoelectrochemical
cells.
The In-rich,
Group III-Nitrides typically have wurtzite structure, and are
grown on substrates (e.g., sapphire) with a large lattice mismatch
due to their small lattice constants. It is therefore not
surprising that they have a large density of dislocations (on
the order of 10^10 cm^-2) and that native
defects play a large role in determining the properties of the
materials. These materials have extremely large electron
affinities, leading to a tendency for n-type doping, and an accumulation
of electrons on the surface that can obscure the properties of
the underlying films.
[1] J. Wu, W. Walukiewicz, K.M. Yu, J.W. Ager III, E.E. Haller, H. Lu, W.J. Schaff , Y. Saito and Y. Nanishi, Unusual properties of the fundamental bandgap of InN, Appl. Phys. Lett. 80 (2002) 3967.
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