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

Wurtzite Al1 xScxN 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 1C, high quality 2DEGs can be grown, especially with (EtCp)2Sc(dtbt). Predictions for the growth of AlYN/GaN heterostructures are made.