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 10¹⁰ 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.