Density of defect states of aluminum nitride grown on silicon and silicon carbide substrates at room temperature

Density of defect states of aluminum nitride (AlN) films deposited by rf magnetron sputtering on < 100 >-oriented silicon (Si) and 4H-silicon carbide (4H-SiC) have been investigated using the deep-level-transient-spectroscopy technique. The films were grown at room temperature with varying nitrogen flow from 4 to 20 sccm and a constant argon flow of 10 sccm. In general the defect densities of AlN are lower when grown on 4H-SiC substrates than on Si substrates. The observed defect levels are identified as donor-like triplet of nitrogen vacancy and DX-like centers. Defects located at 0.35-0.42 eV below the conduction band, attributed to dangling bonds of nitrogen atoms, are seen in samples grown with higher nitrogen flow rate. Shallow level defects, observed at approximately 0.1 eV below the conduction band, can be attributed to the recently discovered prismatic staking fault in the AlN atomic structure.