Aluminum nitride (AlN) is increasingly demanded for use as a substrate for ultraviolet light emitting diodes (UV‐LEDs). A previous study investigated the influence of sputter conditions on the crystalline quality of AlN layers sputtered on nitrided sapphire substrate at 573 and 773 K using radio‐frequency (RF) reactive sputtering. AlN layers were deposited at a higher substrate temperature of 823 K to investigate the influence of sputter power and N2 gas flow ratio on their crystalline quality in this study. The AlN layers were deposited in various conditions (sputter power, 200–900 W; N2 gas flow ratio, 30–70 vol%N2). The growth rate increased concomitantly with increasing sputter power and decreasing N2 gas flow ratio. The crystalline orientation improved with increasing sputter power, except for 900 W at 50 vol%N2. High‐quality c‐axis oriented AlN layers were sputtered with 700 W at 50 vol%N2, and with 800 W at 40 and 50 vol%N2. Results showed that edge dislocation was dominant in AlN layers sputtered with 800 W at 50 vol%N2 from cross‐sectional images observed using transmission electron microscopy (TEM). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Aluminum nitride (AlN) is a promising material for use in applications such as ultraviolet light-emitting diodes and surface acoustic wave devices. In this study, AlN layers were fabricated on nitrided sapphire substrates using radio-frequency (RF) reactive magnetron sputtering. An AlN layer sputtered in 50 vol% N2 with a sputter power of 900 W at 823 K exhibited X-ray rocking curves for AlN (0002) and (10-12) with the best full width at half-maximum of 61 and 864 arcsec, respectively. The c-axis lattice constant of the AlN layers expanded with increasing substrate temperature because of the peening effect and thermal expansion difference between the AlN layer and sapphire substrate. Based on the results obtained here combined with those of our previous studies, a model explaining the roles of sputtering parameters in AlN layer growth using RF reactive sputtering was developed.

Aluminum nitride (AlN) is increasingly demanded for use in semiconductor‐related industries. This study was undertaken for fabrication of high‐quality AlN thick layers using radio‐frequency (RF) reactive sputtering with a pure Al target. The AlN layers were sputtered homoepitaxially on high‐quality thin AlN layers on sapphire substrates for 1.5 h with 300 to 650 W at 573 and 773 K. The AlN thin layers were grown using sapphire nitridation before sputtering. A N2‐Ar gas mixture was used as the sputtering atmosphere and N2 gas flow ratio was changed from 20 to 60 vol%N2. In all sputtering conditions c‐axis oriented AlN layers were fabricated. AlN layer sputtered with 400 W under 40 to 60 vol%N2 at 773 K was grown by about 1 μm thickness. The AlN layer sputtered with 400 W under 40 and 50 vol%N2 at 573 and 773 K showed superior quality, with almost identical crystal structural quality to that of each nitrided sapphire substrate. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)