Controlled formation of voids at the AlN/sapphire interface by sapphire decomposition for self‐separation of the AlN layer

Abstract

Self‐separation of hydride vapor phase epitaxy (HVPE)‐grown AlN layer from sapphire substrate was achieved by the formation of voids at the AlN/sapphire interface. Voids could be formed through the decomposition of sapphire beneath a thin (100 nm) protective AlN layer grown at 1065 °C by heating at 1450 °C in a carrier gas (H2 + N2) containing NH3. Additionally, the void size could be controlled by varying the heating time. As the results of controlled formation of voids, after growth of a thick (85 μm) AlN layer on the thin protective AlN layer heated at 1450 °C for 30 min, self‐separation of the AlN layer from a sapphire substrate occurred by the compressive stress from difference in thermal expansion coefficients between AlN and sapphire during post‐growth cooling. The self‐separated thick AlN layer had low concentration of impurities, and showed clear photoluminescence peak at 208.4 nm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation of void formation beneath thin AlN layers by decomposition of sapphire substrates for self-separation of thick AlN layers grown by HVPE

“…7(b) and (c). Although not shown here, the self-separation of a thick AlN layer from a sapphire substrate did not occur when a 100 nm thick intermediate AlN layer with R v of less than 20% was used, but cracks were generated in both the AlN layer and sapphire substrate [30].…”