Band-GaP Energy and Physical Properties of InN Grown by RF-Molecular Beam Epitaxy
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Band-GaP Energy and Physical Properties of InN Grown by RF-Molecular Beam Epitaxy Yasushi Nanishi1, Yoshiki Saito1, Tomohiro Yamaguchi1, Fumie Matsuda1, Tsutomu Araki1, Hiroyuki Naoi2, Akira Suzuki3, Hiroshi Harima4 and Takao Miyajima5 1
Dept. of Photonics, Ritsumeikan Univ., 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan Center for Promotion of The COE Program, Ritsumeikan Univ., 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan
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Res. Org. of Sci. & Eng., Ritsumeikan Univ., 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan
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Dept. of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto 606-8585, Japan 5 Core Technology Development Center, Core Technology & Network Company, Sony Corporation, 4-14-1 Asahi-cho, Atsugi, Kanagawa 243-0014, Japan
ABSTRACT This paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films were investigated and (1) nitridation process of sapphire substrates prior to growth, (2) precise control of V/III ratio and (3) selection of optimum growth temperature were found to be essential. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films obtained in this study have ideal hexagonal wurtzite structure. FWHMs of ω-2θ mode XRD and E2(high)-phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm-1, respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN grown in this study. PbS, instead of InGaAs, was used as a detector for PL study in order to solve the problem coming from the cut-off wavelength of InGaAs detector. Based on these systematic studies on structural and optical property characterizations using high-quality InN, true band-gap energy of InN is suggested to be less than 0.67 eV and approximately 0.65 eV at room temperature. Single-crystalline InN films are also successfully grown on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated. INTRODUCTION InN is considered to be a very attractive material for future photonic and electronic devices owing to its outstanding material properties like smallest effective mass, largest mobility, highest peak and saturation velocities, and smallest direct band gap in nitride semiconductors. However, until now, InN has been the least studied of nitride semiconductors. This is mainly because of its difficulty in obtaining high quality InN crystals, which is due to the low dissociation temperature and high equilibrium vapor pressure of nitrogen. Properties of InN grown by MOVPE and RF-MBE, however, have been much improved very recently. Especially quality of InN grown by RF-MBE have improved very quickly within a relatively short period of time [1-3] and electrical properties with room temperature electron mobility over 2100 cm2/Vs and residua
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