Influences of In₂O₃Crystal Grains Formed by Annealing on Characteristics of Hexagonal InN Crystalline Films Grown on Si(111) Substrates

ECR-assisted MBE growth of In1−Ga N heteroepitaxial films on Si

“…The biased electric field was estimated to be +60 V/cm at +300 V. The as-grown films under P III = 4.7 × 10 −5 Pa exhibited many In or/and Ga droplets on the film surface, namely suggesting typical growth under Inor Ga-rich condition, the so-called III-family-rich condition. After growth, some samples were annealed at 500 • C for 5 min in the N 2 atmospheric pressure gas with purity of 99.999% at a flow rate of 2 slm without etching (anneal) or others were annealed under the same conditions after etching them by concentrated HCl solution in order to completely remove the In or/and Ga droplets (HCl etching + anneal) [12,14]. The surface morphology, crystal structure, crystalline quality and optical property were characterized by a Nomarski phase contrast interference microscope, atomic force microscopy (AFM), X-ray diffraction and PL spectroscopy at 8.8-13 K using 325 nm He-Cd, 514.5 and 488 nm Ar + ion lasers as excitation light sources, respectively.…”

“…It is concluded that residual O impurities with concentrations of ∼0.5∼1% were contained in the typical as-grown InN films. The O atoms might be incorporated as impurities into the film, despite the very low background pressure of 2.7 × 10 −7 Pa during growth, through the occurrence of positive ions such as NO 2 + or/and NO + ions [14,15], which would probably be formed in ECR plasma under N 2 atmosphere including residual O 2 gas in the growth chamber. Or/and O 2 molecules in air might also be incorporated by out-diffusion from the film surface after growth.…”

“…As possible reasons for the inconsistency in band-gap energy, the influences of residual oxygen (O) impurities and the presence of In 2 O 3 crystal grains and/or InON alloy grains with wide band-gap energies contained in the α-InN crystals are suspected. Therefore, we have investigated the influences of residual oxygen (O) impurities and the presence of In 2 O 3 crystal grains in α-InN for 200 nmthick α-InN crystalline films grown on Si(111) substrates by electron cyclotron resonance plasma-assisted molecular beam epitaxy (ECR-MBE) [12,14]. We have reported that a high concentration of O 2 molecules incorporated into In droplets adhering to the surface of the InN film by air exposure after growth formed β-In 2 O 3 crystal grains by post-anneal at temperatures higher than 300 • C [14].…”

“…Therefore, we have investigated the influences of residual oxygen (O) impurities and the presence of In 2 O 3 crystal grains in α-InN for 200 nmthick α-InN crystalline films grown on Si(111) substrates by electron cyclotron resonance plasma-assisted molecular beam epitaxy (ECR-MBE) [12,14]. We have reported that a high concentration of O 2 molecules incorporated into In droplets adhering to the surface of the InN film by air exposure after growth formed β-In 2 O 3 crystal grains by post-anneal at temperatures higher than 300 • C [14]. In this paper, the influence of β-In 2 O 3 crystal grains due to In droplets was fully removed by etching the In droplets off before anneal, and the influences of residual O atoms, β-In 2 O 3 crystal grains and/or InON alloy grains included in InN and In 1−x Ga x N films, which were probably formed by thermal reaction of residual O atoms during growth or/and O 2 molecules out-diffused from air into the film after growth with the respective films, have been investigated in more detail.…”

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

“…Therefore, the band-gap energy of 1.89 eV is very doubtful at the present stage, and the reason for this inconsistency requires detailed discussion. We hypothesis that the inconsistencies are due to the influences of residual O impurities and/or the inclusion of In 2 O 3 grains and InON alloy grains with wide band-gap energies [7,8] in InN films, which might be formed through plasma during growth or through air exposure after growth. In this paper, we discuss the influences of residual O impurities and the inclusion of InON alloy grains in addition to In 2 O 3 grains in 200-nm-thick α-InN films grown on Si(111) substrates by electron cyclotron resonance-assisted molecular beam epitaxy (ECR-MBE), which were annealed in N 2 or N 2 20%-mixed with H 2 after growth (N 2 and H 2 annealing).…”