Twinned growth of ScN thin films on lattice-matched GaN substrates

Abstract

Scandium nitride (ScN) has attracted significant interest in recent years for diverse electronic and thermoelectric applications. Most ScN growth utilizes MgO and Al2O3 as substrates that lead to extended defects such as dislocations and grain boundaries. (0001) GaN exhibits less than 0.1% lattice mismatch with (111) ScN, and therefore, should result in single-crystalline ScN film growth. However, not much attention is devoted to understanding the microstructure of ScN on GaN substrates. In this work, we present (111) oriented lattice matched ScN film growth on (0001) GaN substrates. X-ray pole figure exhibited six spots for the (002) ScN superimposed on that of (101) GaN separated by 60° corresponding to twin domains of threefold symmetry for (111) ScN, which are furthermore directly imaged by lattice resolved microscopy images. The presence of twins is attributed to vertical dislocations originating at the GaN/Al2O3 interface and extending throughout the GaN film to its interface with ScN.