Influences of residual oxygen impurities, cubic indium oxide grains and indium oxy-nitride alloy grains in hexagonal InN crystalline films grown on Si(111) substrates by electron cyclotron resonance plasma-assisted molecular beam epitaxy

摘要

We investigated the influences of residual oxygen (O) impurities, cubic indium oxide (β-In_2O_3) grains and indium oxy-nitride (InON) alloy grains in 200 nm-thick hexagonal (α)-InN crystalline films grown on Si(111) substrates by electron cyclotron resonance plasma-assisted molecular beam epitaxy. Although β-In_2O_3　grains with wide band-gap energy were formed in In film by N_2 annealing, they were not easily formed in N_2-annealed InN films. Even if they were not detected in N_2-annealed InN films, the as-grown films still contained residual O impurities with concentrations of less than 0.5% ([O] ≦0.5%). Although [O]～1% could be estimated by investigating In_2O_3 grains formed in N_2-annealed InN films, [O]≦0.5% could not be measured by it. However, we found that they can be qualitatively measured by investigating In_2O_3 grains formed by H_2 annealing with higher reactivity with InN and O_2, using X-ray diffraction and PL spectroscopy. In this paper, we discuss the formation mechanism of InON alloy grains in InN films.