Tailoring p- and n- type semiconductor through site selective oxygen doping in Cu3N: density functional studies

• Published in: Materials research express Vol. 3; no. 6
• Main Authors: Sahoo, Guruprasad, Kashikar, Ravi, Jain, Mahaveer K, Nanda, B R K
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.06.2016
• Subjects: DFT; electronic structure; formation energy; oxygen doping; semiconductor
• ISSN: 2053-1591
• DOI: 10.1088/2053-1591/3/6/065902

Using ab initio density functional calculations, we have investigated the stability and electronic structure of pure and oxygen doped semiconducting Cu3N. The oxygen can be accommodated in the system without structural instability as the formation energy either decreases when oxygen substitutes nitrogen, or remains nearly same when oxygen occupies the interstitial position. The interstitial oxygen (OI) prefers to stabilize in the unusual charge neutral state and acts as an acceptor to make the system a p-type degenerate semiconductor. In this case the hole pockets are formed by the partially occupied OI-p states. On the other hand, oxygen substituting nitrogen (OS) stabilizes in its usual −2 charge state and acts as a donor to make the system an n-type degenerate semiconductor. The electron pockets are formed by the conducting Cu-p states. In the case of mixed doping, holes are gradually compensated by the donor electrons and an intrinsic gap is obtained for Cu 3 N 1−2 x O S 2 x O I x stoichiometry. Our calculations predict the nature of doping as well as optical band gap ( E g o p t ) variation in experimentally synthesized copper oxynitride. While interstitial doping contracts the lattice and increases the E g o p t , substitutional doping increases both lattice size and E g o p t . Mixed doping reduces E g o p t . Additionally we show that a rare intra-atomic d-p optical absorption can be realized in the pristine Cu3N as the Fermi level lies in the gap between the Cu-d dominated anti-bonding valence state and Cu-p conducting state.