AlN homoepitaxial growth on sublimation-AlN substrate by low-pressure HVPE
Crack-free thick AlN layers with low impurity concentrations were grown on free-standing AlN substrates fabricated by a sublimation method. Cracks due to tensile stresses were generated in the overgrowth layer when using on-axis AlN (0 0 0 1) substrates, as indicated by Raman scattering spectroscopy. In contrast, cracks were not generated when using 5° off-angle AlN (0 0 0 1) substrates. High crystalline quality was indicated by X-ray rocking curve (XRC) analysis. The full width at half maximum (FWHM) values of the (0 0 0 2) and (1 0–1 0) diffractions were 277 and 306 arcsec, respectively. Secondary ion mass spectrometry (SIMS) measurements indicated that the Si and C impurity concentrations were reduced to half of those in the sublimation-grown AlN substrates.
Fig. 1. X-ray rocking curves of (0 0 0 2) reflection obtained by ω-scans for the substrate and overgrowth layer. The suppression of peak splitting and the reduction suggest that each grain tends to become aligned as AlN is overgrown.
Source: Journal of Crystal Growth