Effect of c‐plane sapphire misorientation on the growth of AlN by high‐temperature MOVPE

Abstract

AlN layers were directly grown on sapphire substrates with slightly different miscut angles from the c‐plane by metalorganic vapor phase epitaxy at 1300 °C. By X‐ray diffraction analysis, the structural quality was found to improve with the increase in substrate off‐angle. When the substrate off‐angle was 0.5°, the X‐ray rocking curve (XRC) full widths at half maximum (FWHMs) of symmetric and asymmetric planes were 170 and 550 arcsec, respectively. At smaller off‐angle, XRC‐FWHMs were wider. When the substrate off‐angle was zero, the XRC‐FWHM was considerably inferior to that on 0.5o‐off‐angle sapphire. The surface morphology was investigated. Atomic steps were observed on the substrates with a small misorientation. In contrast, macro steps appeared on larger‐off‐angle sapphire substrates. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface kinetics in AlN growth: A universal model for the control of surface morphology in III-nitrides

“…The surface energy changes very slowly with a large deviation in λ s due to the exponential in Equation 17, helping to validate the use of the calculated γ s value. According to these results, the surface energy of the Al-polar surface of AlN is of the same order of magnitude as that of the (1-100) and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) planes, which were predicted from density functional theory by Jindal et al to be 175 and 187 meV/Å 2 , respectively. 29 Furthermore, this result can be used to corroborate current theoretical models that try to predict the surface energy.…”

“…All of these general trends were found to be independent of the misorientation direction. The only differences observed for misorientations toward [1-100] as compared to [11][12][13][14][15][16][17][18][19][20] was the step edge shape, as discussed earlier and depicted in Figure 1.…”

“…Figure 1 shows the six primary types of surface morphologies observed in this study for AlN homoepitaxial layers grown on native AlN single crystal substrates. and [11][12][13][14][15][16][17][18][19][20] directions, respectively. In fact, the degree of jaggedness was directly correlated to the deviation of the misorientation direction from the <1-100> directions and reached a maximum for the offcuts toward the <11-20> directions, as all steps decomposed into steps pointing in <1-100> directions.…”

“…The effect of substrate misorientation on surface morphology has been observed for AlN and AlGaN epitaxy on sapphire substrates. 11,12 However, kinetics on these surfaces is controlled primarily by the spiral growth due to high dislocation density (10 9 -10 10 cm -2 ). The spiral growth coupled with high spiral density makes it difficult to directly observe the long-range surface kinetics as related to different growth modes.…”

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

“…The use of off-cut sapphire has been found to be very effective in growing highquality a-plane GaN [10] and c-plane AlN [11] with a fairly flat surface. Shibata et al [12] reported the effect of the misorientation of r-plane sapphire on the crystalline quality of AlN.…”