Limits for n-type doping in In2O3 and SnO2: A theoretical approach by first-principles calculations using hybrid-functional methodology

Abstract

The intrinsic n-type doping limits of tin oxide ͑SnO 2 ͒ and indium oxide ͑In 2 O 3 ͒ are predicted on the basis of formation energies calculated by the density-functional theory using the hybrid-functional methodology. The results show that SnO 2 allows for a higher n-type doping level than In 2 O 3 . While n-type doping is intrinsically limited by compensating acceptor defects in In 2 O 3 , the experimentally measured lower conductivities in SnO 2 -related materials are not a result of intrinsic limits. Our results suggest that by using appropriate dopants in SnO 2 higher conductivities similar to In 2 O 3 should be attainable.

Transparent Conducting Oxides for Photovoltaics: Manipulation of Fermi Level, Work Function and Energy Band Alignment

“…The origin of this difference is related to the higher formation enthalpies of the possible “killer" defects, Sn-vacancies and O-interstitials, which are related to the high charge state of Sn and the rutile crystal structure of SnO${}_2$ [38,39]. Instead, the high-pO${}_2$ electroneutrality regime represents straightforward donor-doping, i.e ., $n=\left[{\mathrm{Sb}}_{\mathrm{Sn}}^{•}\right]$, and the low-pO${}_2$ regime represents the possibility of additional electrons owing to intrinsic defects (e.g., oxygen vacancies).…”

Compensating vacancy defects in Sn- and Mg-dopedIn2O3

“…Also, the formation energy of V In is higher in p-type material than in n type [13]. Hence, it is natural that the Mg-doped samples give S values that are close to the perfect lattice, as V In should be rare, and Mg should substitute In.…”

“…All experimental findings suggest intrinsic point defects to play a major role in influencing the conductivity of In 2 O 3 . Recent calculations of their formation energy using stateof-the art ab initio theory [4,5,7,[13][14][15] agree on a reduced formation energy-corresponding to increased equilibrium concentration-of the donorlike defects (V O , In i ) and acceptorlike defects (V In and O i ) for low and high Fermi levels, respectively, indicating the tendency of these point defects to compensate intentional doping that decrease (acceptor) and increase (donor) the Fermi level, respectively. In addition, these calculations indicate a reduced formation energy of the donorlike and acceptorlike defects for indium-rich (oxygen poor) and oxygen-rich (indium poor) conditions, respectively.…”

Valence-band density of states and surface electron accumulation in epitaxialSnO2films

“…Over the past two decades density functional theory (DFT) calculations using hybrid functionals have been shown to produce improved descriptions of structure, band gap, and defect properties of a range of binary, ternary, and quaternary oxide semiconductors [22][23][24][25][26][27][28][29][30]. In spite of some density functional theory calculations of the density of states (DOS) in SnO 2 [24,31] with comparisons to photoemission spectra [21], no detailed work has been accomplished to correlate the two through the application of photoionization cross sections on the calculated partial density of states (PDOS).…”