Point Defects and p -Type Doping in ScN from First Principles

Abstract

Scandium nitride (ScN) has been intensively researched as a prototype of rocksalt nitrides and a potential counterpart of the wurtzite group IIIa nitrides. It also holds great promise for applications in various fields, including optoelectronics, thermoelectrics, spintronics, and piezoelectrics. We theoretically investigate the bulk properties, band-edge positions, chemical stability, and point defects, i.e., native defects, unintentionally doped impurities, and p-type dopants of ScN using the Heyd-Scuseria-Ernzerhof hybrid functional. We find several fascinating behaviors: (i) a high level for the valence-band maximum, (ii) the lowest formation energy among binary nitrides, (iii) high formation energies of native point defects, (iv) low formation energies of donor-type impurities, and (v) a p-type conversion by Mg doping. Furthermore, we uncover the origins of the Burstein-Moss shift commonly observed in ScN. Our work sheds light on a fundamental understanding of ScN in regard to its technological applications.

Ca4Sb2O and Ca4Bi2O: two promising mixed-anion thermoelectrics

“…Both compounds have high-lying valence-band maxima (VBM) relative to the vacuum level, which is a characteristic feature of native p-type semiconductors such as Si, Cu 2 O and ScN. [89][90][91][92] The lower ionisation potential (lower-lying VBM) for Ca 4 Bi 2 O can be attributed to better overlap between the Bi p and Ca states and the resulting stronger orbital interactions and larger band dispersion. The high-lying VBM and conduction-band minima (CBM) in the two materials would result in low ionisation potentials and low electron affinities.…”

One-dimensionally extended oxygen vacancy states in perovskite oxides

“…Note that +1 and neutral charge states in r-TiO 2 show the small polaronic nature, meaning one and two small polarons are trapped at the Ti sites, respectively, as reported in[29,30]. The 2+/+/0 CTL in anatase TiO 2 is confirmed without sampling the conduction band minimum (CBM) using the Monkhorst-Pack k-point mesh (see Refs [31,32]. for details).…”

“…Spin polarization was considered for V O 0 and V O + . Methods for calculating the defect formation energies and the details of the eFNV correction scheme can be found elsewhere [12,31,32]. To avoid other contributions to the electrostatic atomic site potentials and cell size dependences, only the ground state perovskite oxides were treated in this study; when a defect is introduced into a dynamically unstable phase, the defect formation energy and electrostatic potential may be drastically modified because of defect-induced symmetry lowering.…”

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

“…Both compounds have high-lying valence-band maxima (VBM) relative to the vacuum level, which is a characteristic feature of native p-type semiconductors such as Si, Cu 2 O and ScN. [88][89][90][91] The lower ionisation potential (lower-lying VBM) for Ca 4 Bi 2 O can be attributed to better overlap between the Bi p and Ca states and the resulting stronger orbital interactions and larger band dispersion. The high-lying VBM and conduction-band minima (CBM) in the two materials would result in low ionisation potentials and low electron affinities.…”