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In this work, we present a comprehensive study on the hydrogen impurity depth profiles in InN films with polar c-plane and nonpolar a-plane surface orientations in relation to their structural and free-electron properties. We find that the as-grown nonpolar films exhibit generally higher bulk and near-surface H concentrations compared to the polar InN counter-parts. The latter may be partly associated with a change in the growth mode from 2D to 3D and a decrease in the grain size. Thermal annealing leads to a reduction of H concentrations and the intrinsic H levels are influenced by the structural characteristics of the films. The factors allowing reduction of bulk H and free electron concentrations in a-plane films are discussed., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films., Funding Agencies|FCT Portugal|PTDC/FIS/100448/2008|Swedish Research Council (VR)|2010-3848

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices., Original Publication: Vanya Darakchieva, Mengyao Xie, N Franco, F Giuliani, B Nunes, E Alves, C L Hsiao, L C Chen, T Yamaguchi, Y Takagi, K Kawashima and Y Nanishi, Structural anisotropy of nonpolar and semipolar InN epitaxial layers, 2010, JOURNAL OF APPLIED PHYSICS, (108), 7, . http://dx.doi.org/10.1063/1.3487923 Copyright: American Institute of Physics http://www.aip.org

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices., Original Publication: Vanya Darakchieva, Mengyao Xie, N Franco, F Giuliani, B Nunes, E Alves, C L Hsiao, L C Chen, T Yamaguchi, Y Takagi, K Kawashima and Y Nanishi, Structural anisotropy of nonpolar and semipolar InN epitaxial layers, 2010, JOURNAL OF APPLIED PHYSICS, (108), 7, . http://dx.doi.org/10.1063/1.3487923 Copyright: American Institute of Physics http://www.aip.org

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices., Original Publication: Vanya Darakchieva, Mengyao Xie, N Franco, F Giuliani, B Nunes, E Alves, C L Hsiao, L C Chen, T Yamaguchi, Y Takagi, K Kawashima and Y Nanishi, Structural anisotropy of nonpolar and semipolar InN epitaxial layers, 2010, JOURNAL OF APPLIED PHYSICS, (108), 7, . http://dx.doi.org/10.1063/1.3487923 Copyright: American Institute of Physics http://www.aip.org

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices., Original Publication: Vanya Darakchieva, Mengyao Xie, N Franco, F Giuliani, B Nunes, E Alves, C L Hsiao, L C Chen, T Yamaguchi, Y Takagi, K Kawashima and Y Nanishi, Structural anisotropy of nonpolar and semipolar InN epitaxial layers, 2010, JOURNAL OF APPLIED PHYSICS, (108), 7, . http://dx.doi.org/10.1063/1.3487923 Copyright: American Institute of Physics http://www.aip.org

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices., Original Publication: Vanya Darakchieva, Mengyao Xie, N Franco, F Giuliani, B Nunes, E Alves, C L Hsiao, L C Chen, T Yamaguchi, Y Takagi, K Kawashima and Y Nanishi, Structural anisotropy of nonpolar and semipolar InN epitaxial layers, 2010, JOURNAL OF APPLIED PHYSICS, (108), 7, . http://dx.doi.org/10.1063/1.3487923 Copyright: American Institute of Physics http://www.aip.org

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for the unintentional conductivity in MBE InN., Original Publication: Vanya Darakchieva, K Lorenz, N P Barradas, E Alves, Bo Monemar, M Schubert, N Franco, C L Hsiao, L C Chen, W J Schaff, L W Tu, T Yamaguchi and Y Nanishi, Hydrogen in InN: A ubiquitous phenomenon in molecular beam epitaxy grown material, 2010, APPLIED PHYSICS LETTERS, (96), 8, 081907. http://dx.doi.org/10.1063/1.3327333 Copyright: American Institute of Physics http://www.aip.org

The free electron properties of nonpolar (1120)-oriented and semipolar (1011)-oriented wurtzite InN films are studied by generalized infrared ellipsometry (GIRSE). We demonstrate the sensitivity of GIRSE to the surface charge accumulation layer and find a distinct surface electron accumulation to occur at all surfaces. The obtained surface electron sheet densities are found to vary from 0.9x10(13) to 2.3x10(14) cm(-2) depending on the surface orientation and bulk electron concentration. The upper limits of the surface electron mobility parameters of 417-644 cm(2)/V s are determined and discussed in the light of electron confinement at the surface.

The free electron properties of nonpolar (1120)-oriented and semipolar (1011)-oriented wurtzite InN films are studied by generalized infrared ellipsometry (GIRSE). We demonstrate the sensitivity of GIRSE to the surface charge accumulation layer and find a distinct surface electron accumulation to occur at all surfaces. The obtained surface electron sheet densities are found to vary from 0.9x10(13) to 2.3x10(14) cm(-2) depending on the surface orientation and bulk electron concentration. The upper limits of the surface electron mobility parameters of 417-644 cm(2)/V s are determined and discussed in the light of electron confinement at the surface.