Molecular beam epitaxial growth of (1 1 ‐2 2) GaN on m‐plane sapphire

Abstract

The structural and optical properties of semipolar (1 1 ‐2 2) GaN grown on m‐plane (1 0 ‐1 0) sapphire substrates by molecular beam epitaxy were investigated. An inplane orientation relationship was found to be [1 ‐1 0 0] GaN || [1 2‐1 0] sapphire and [‐1 ‐1 2 3] GaN || [0 0 0 1] sapphire for semipolar GaN on m‐plane sapphire substrates. The near band emission (NBE) was found at 3.432 eV, which is slightly blue shifted compared to the bulk GaN. The Raman E2 (high) peak position observed at 569.1 cm–1, which indicates that film is compressively strained. Schottky barrier height (φb) and the ideality factor (η) for the Au/ semipolar GaN Schottky diode found to be 0.55 eV and 2.11, respectively obtained from the TE model. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Semipolar and nonpolar GaN epi-films grown on m-sapphire by plasma assisted molecular beam epitaxy

“…The peak at 2H ¼ 32.37 was assigned to (10-10) GaN and at 2H ¼ 68.21 was assigned to (30-30) Al 2 O 3 . 2H-x HRXRD scan of Sample B shows semipolar GaN epilayer oriented in the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) direction over the (10-10) m-plane sapphire. The peak at 2H ¼ 68.9 was assigned to (11-22) GaN and at 2H ¼ 68.21 was assigned to (30-30) Al 2 O 3 .…”

“…Nonpolar (10-10) GaN and semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN epilayers were separately grown on (10-10) m-plane sapphire substrates by Omicron Nanotechnology plasma-assisted MBE system. The initial chemical cleaning procedure was kept same for both the samples.…”

“…[1][2][3][4] However, optoelectronic devices made out of the conventional polar orientation are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields. 5,6 Growing GaN on nonpolar orientation such as (10-10) m-plane or (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane, avoids the polarization effects. Devices grown on these orientations are receiving a lot of focus due to enhanced behavior.…”

“…7,8 The difficulties in obtaining high-quality nonpolar material lie in the planar anisotropic nature of the growth mode, which is a consequence of the anisotropy of both the lattice mismatch and the adatom diffusion length. 9 Our group has previously reported nonpolar a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) GaN grown on an r-plane sapphire substrate at different growth temperatures and studied the role of growth temperature in controlling the surface morphology and structural and optical properties of the films. 10 Growth of nonpolar m-GaN on m-sapphire by various techniques such as hydride vapour phase epitaxy (HVPE), 11 metal-organic chemical vapor deposition (MOCVD), 12 and on m-sapphire substrates with slight c-axis miscut 13,14 has been reported earlier but not much study was evident by MBE.…”

“…The effect of nitridation was not fully understood, however, was conjectured that either surface energy or elastic energy played a major role, depending on the nitridation condition. 16 In the present work, nonpolar (10-10) GaN and semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN on m-plane sapphire were grown and their structural and optical properties were studied and compared.…”