Indium nitride was grown on Al2O3 substrate and characterized by x-ray diffraction, Raman, electrical resistivity, Hall, and magnetoresistance studies. Thermoelectric and electrical properties of free-standing films were measured in situ under high pressure HP cycling to 20 GPa, across a phase transformation to a rock-salt-structured lattice. HP-cycling-induced amorphization was established. The thermopower Seebeck effect data evidence that both crystalline and amorphous InN kept n-type conductivity to 20 GPa. Pressure effect on the carrier concentration and effective mass is analyzed. Two features that can be related to structural transitions in amorphous InN were found near 11 and 17 GPa.

Uncapped InN nanostructures undergo a deleterious natural aging process at ambient conditions by oxygen incorporation. The phases involved in this process and their localization is mapped by transmission electron microscopy (TEM)-related techniques. The parent wurtzite InN (InN-w) phase disappears from the surface and gradually forms a highly textured cubic layer that completely wraps up a InN-w nucleus which still remains from the original single-crystalline quantum dots. The good reticular relationships between the different crystals generate low misfit strains and explain the apparent easiness for phase transformations at room temperature and pressure conditions, but also disable the classical methods to identify phases and grains from TEM images. The application of the geometrical phase algorithm in order to form numerical moire mappings and RGB multilayered image reconstructions allows us to discern among the different phases and grains formed inside these nanostructures. Samples aged for shorter times reveal the presence of metastable InN:O zinc blende (zb) volumes, which act as the intermediate phase between the initial InN-w and the most stable cubic In2O3 end phase. These cubic phases are highly twinned with a proportion of 50:50 between both orientations. We suggest that the existence of the intermediate InN: O-zb phase should be seriously considered to understand the reason for the widely scattered reported fundamental properties of thought to be InN-w, as its bandgap or superconductivity.

We report the growth of indium nitride on AlPO4, which is a piezoelectric substrate, by using metal organic vapor phase epitaxy (MOVPE). The substrate we used was the as-grown (011) surface of an AlPO4 crystal grown by hydrothermal synthesis. InN growth occurs as the nonpolar M-plane. The structural, optical, and electrical properties of the epilayer are comparable with those of layers obtained by conventional growth on polar GaN MOVPE templates deposited on C-plane sapphire. We discuss the utilization of other MX-O-4 oxides for growing nitrides.

Thermal annealing of InN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated in nitrogen atmosphere for temperatures ranging from 400 to 550 degrees C and for heat treatment times up to 12 h. This treatment results in hydrogen outdiffusion, lowering significantly the residual n-type background doping. This mechanism is shown to be reversible through thermal annealing under ammonia atmosphere, responsible of hydrogen incorporation during growth. These results establish a MOVPE process allowing the obtention of InN samples, which exhibit similar electrical properties than molecular beam epitaxy grown samples: a key issue in view of future industrial production of InN based devices.

We report the experimental determination of the interband deformation potentials of indium nitride by combining both optical spectroscopy investigations and high-resolution X-ray measurements performed on a series of InN films grown by metal organic vapour-phase epitaxy. Our approach, which follows the one used for GaN by Shan et al. [Phys. Rev. B. 54 (1996) 13460], gives here for InN a1=-7.66 eV, a2=-2.59 eV, b1=5.06 eV, and b2=-2.53 eV.