Electron behavior and impurity properties as functions of growth temperature for InN grown by using plasma-assisted molecular beam epitaxy

Unintentionally doped n-type InN epilayers were grown on sapphire by using plasma-assisted molecular beam epitaxy and were characterized by using Hall effect and X-ray diffraction. The electron density was in a narrow range of 3.6 - 4.5 x 10(18) cm(-3). Hall effects showed that two scattering mechanisms due to ionized impurities and space charges dominate at temperatures lower than room temperature. The lattice-limited mobility was calculated at 5800 cm(2)/V.s at 300 K. Despite the high density of edge dislocations, scattering due to those dislocations turned out to be negligible. Instead, space-charge scattering was significant and likely originated from randomly clustered dislocations, typically in InN layers. Two donor states were observed, one above and the other below the conduction band minimum. The thermal activation energy of the lower state donor was high due to the Fermi energy level being located deep in the conduction band, and the state seemed to be related to the dislocations.