AlN films were grown on AlN/sapphire templates at 1400–1500 °C using low‐pressure hydride vapor phase epitaxy (LP‐HVPE). Compared to the step‐flow growth of AlN film at 1200 °C with growth rate of 2.1 μm/h, AlN films with atomic steps were obtained at 1400–1500 °C even with high growth rate. For the AlN film grown at 1450 °C with growth rate of 14.3 μm/h, the RMS value is 0.75 nm and the FWHM values of (0002) and (10‐12) X‐ray rocking curve (XRC) are 351 and 781 arcsec, respectively. Since the FWHM value of (10‐12) XRC for the AlN/sapphire template is 1492 arcsec, the crystal quality of HVPE‐grown AlN is greatly improved compared with the AlN/sapphire template, which is also confirmed by TEM observation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A stress control method was proposed to suppress crack generation in the hydride vapor phase epitaxy (HVPE) of a thick AlN film on an AlN/sapphire template, i.e., a high-compressive-strain (HCS) AlN/sapphire template was employed as a substrate. The AlN films on the HCS AlN/sapphire template were crack-free and very smooth. However, the AlN films on the normal AlN/sapphire template (with a reduced or fully relaxed compressive strain) contained many cracks. This is because the HCS in the AlN/sapphire template may balance some of the thermal tensile strain resulting from the different thermal expansion coefficients of AlN and sapphire and thus suppress the crack generation. The typical full width at half maximum (FWHM) values of X-ray rocking curves for the (0002), (10 " 1 12), and (10 " 1 10) diffractions of the HVPE-grown AlN film on the HCS template were 127, 381, and 520 arcsec, respectively. Accordingly, by atomic force microscopy (AFM), clear atomic steps were observed on the HVPE-grown AlN films on the HCS template, and the root-mean-square (RMS) roughness value of the AlN films was 0.361 nm.