Growth of a‐plane AlN on r‐plane sapphire by plasma source molecular beam epitaxy

Abstract

We report the epitaxial growth of a-plane AlN on r-plane sapphire (Al 2 O 3 ) substrates with an AlN nucleation layer. The AlN film is identified to be non polar and of a-plane orientation ( 0 2 11 _ ) which follows the r-plane Al 2 O 3 . The epitaxial films of thickness 0.34 µ were grown at low temperature (650 °C) by Plasma Source Molecular Beam Epitaxy (PSMBE). Initially we deposited a thin (50 Å) buffer layer of AlN on a 3 inch r-plane sapphire substrate at 400 °C in argon/nitrogen plasma followed by a 10 min annealing at 650 °C. The reflection high energy electron diffraction (RHEED) method was used for in situ structural characterization during the growth process. The a-plane growth has been confirmed by ex situ high resolution X-ray diffraction (XRD). Only the a-plane reflection peak appears at 2θ = 59.5º. The surface morphology of the films was examined by atomic force microscopy (AFM). Optical properties of the films have been studied using reflection spectroscopy in the 175-3300 nm wavelength range.

Influence of off-cut angle of r-plane sapphire on the crystal quality of nonpolar a-plane AlN by LP-HVPE

“…The difficulty lies mainly in the anisotropic nature of the growth mode. Recently, a-plane AlN layers have been grown on r-plane sapphire by molecular-beam epitaxy [6] and metalorganic vapor phase epitaxy (MOVPE) [7]. However, it is seldom reported the growth of a-plane AlN layer by hydride vapor phase epitaxy (HVPE).…”

Effects of initial stages on the crystal quality of nonpolar a-plane AlN on r-plane sapphire by low-pressure HVPE

“…However, compared with c-plane AlN, it is difficult to grow nonpolar AlN with high crystal quality, due to the planar anisotropic nature of the growth mode [7][8][9][10]. Recently, a-plane AlN has been obtained by MBE [11] and MOCVD [12][13][14][15]. But, little has been reported on the growth of nonpolar a-plane AlN by HVPE on r-plane sapphire substrate.…”

In-plane structural anisotropy and polarized Raman-active mode studies of nonpolar AlN grown on 6H-SiC by low-pressure hydride vapor phase epitaxy

“…The growth of AlN (1 1 2 0) and (1 1 0 0) thin films have been examined by many researchers using MBE and MOCVD [4][5][6][7][8][9], and nonpolar GaN/AlGaN [10] and AlN/AlGaN [11] quantum wells (QWs) have been demonstrated. Some results have proved the superior properties of nonpolar Al(Ga)N-based LEDs in comparison with conventional polar c-plane structures, particularly a significantly increased photoluminescence intensity.…”