Influence of sputter power and N2 gas flow ratio on crystalline quality of AlN layers deposited at 823 K by RF reactive sputtering



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)