Role of scandium precursor decomposition in MOCVD of AlScN and predictions for AlYN

Wurtzite Al_1−xSc_xN is a novel nitride that attracts attention for its piezoelectric and ferroelectric properties, and further offers the possibility to grow strain-free AlScN/GaN heterostructures due to an a lattice parameter matching with GaN. Growth of AlScN by metal–organic chemical vapor deposition is challenging because of the low vapor pressure of commercially available Sc precursors and a high amount of carbon atoms present in these precursors, that can incorporate into the films. In this work, precursor decomposition and ligand loss of the novel Sc precursors (EtCp)₂Sc(bdma) and (EtCp)₂Sc(dtbt) are studied by density functional theory and related to experimental results. It is found that low temperatures, low pressures, and low NH₃ flows promote carbon incorporation and lead to grey coloration of AlScN films grown with (EtCp)₂Sc(bdma), probably due to the high residual mass of this precursor. At 1100 °C, high quality 2DEGs can be grown, especially with (EtCp)₂Sc(dtbt). Predictions for the growth of AlYN/GaN heterostructures are made.