Optical Properties of Aluminum Nitride Thin Films Prepared by Magnetron Sputter Epitaxy

Aluminum nitride (AlN) due to its wide bandgap, electro-optic coefficient, nonlinear effects, high thermal conductivity, and complementary metal-oxide semiconductor compatibility has emerged as an attractive material for optical wave guides and modulators that operate in deep ultraviolet wavelengths. AlN thin films exhibiting low optical absorption are desired for these applications, as it can reduce optical losses in waveguides. To achieve AlN with low absorption, this study sputters AlN on different substrates, process gas, and seed layers and investigates their crystalline quality, impurity concentration, and optical absorption. This findings demonstrate that controlling these parameters is essential for obtaining AlN with minimal optical absorption. Furthermore, it also shows that the waveguides prepared using sputtered AlN have an average optical loss of 0.15 dB cm-1 at 1550 nm which is similar to MOCVD grown AlN, indicating the potential of this material in opto-electronic applications.