Molecular Beam Epitaxy Growth of Scandium Nitride on Hexagonal SiC, GaN, and AlN

TL;DR

This study demonstrates the growth of cubic Scandium Nitride (ScN) thin films on various hexagonal substrates using RF plasma assisted MBE, revealing novel twinned crystal structures and promising electronic properties.

Contribution

First observation of cubic twinned patterns in ScN during epitaxy, with detailed structural and electronic characterization on hexagonal substrates.

Findings

Cubic (111) twinned patterns observed in ScN

High n-type carrier concentration (~1x10^20/cm^3)

Electron mobility around 20 cm^2/Vs

Abstract

RF plasma assisted MBE growth of Scandium Nitride (ScN) thin films on GaN (0001)/SiC, AlN (0001)/Al2O3 and on 6H-SiC (0001) hexagonal substrates is found to lead to a face centered cubic (rock-salt) crystal structure with (111) out-of-plane orientation instead of hexagonal orientation. For the first time, cubic (111) twinned patterns in ScN are observed by in-situ electron diffraction during epitaxy, and the twin domains in ScN are detected by electron backscattered diffraction, and further corroborated with X-ray diffraction. The epitaxial ScN films display very smooth, sub nanometer surface roughness at a growth temperature of 750C. Temperature-dependent Hall-effect measurements indicate a constant high n-type carrier concentration of ~1x1020/cm3 and electron mobilities of ~ 20 cm2/Vs.