Abstract
In this thesis, we present successful growth and characterization (optical, electrical, and thermal) of InN epitaxial films and nanostructures by molecular beam epitaxy. Temperature-dependent photoluminescence (PL) spectroscopy is used as a tool to study the much controversial optical band gap in degenerate InN. Samples with PL peak on the lower and higher energy side of 0.730 eV demonstrate a normal redshift and anomalous blueshift, respectively, with increasing temperature. This can be explained effectively on the basis of a competition between a conventional red shift from lattice dilation and a blue shift of the electron and hole quasi Fermi-level separation. On the electrical characterization part, we report the first observation of negative photoconductivity behavior in InN thin films. Unlike most conventional (non-degenerate) semiconductors, that show increase in conductivity with illumination, InN shows a regular decrease. The results have been qualitatively modeled on the basis of electronic scattering in the conduction band and transitions in degenerate InN with recombination centers. Finally, a systematic thermal diffusivity (related to thermal conductivity) study in the MBE-grown InN thin films on various substrates with different growth temperatures were carried out. A high thermal diffusivity value of 0.55 cm2/s for a combined 1.7 um thick InN film suggests a lower degree of phonon scattering in our sample with fewer structural defects.