Despite decades of efforts, achieving p-type conductivity in the wide band gap ZnO in its ground-state wurtzite structure continues to be a challenge. Here we detail how p-type ZnO can be realized in the metastable, high-pressure rocksalt phase (also wide-gap) with Li as an external dopant. Using modern first-principles defect theory, we predict Li to dope the rocksalt phase p-type by preferentially substituting for Zn and introducing shallow acceptor levels. Formation of compensating donors like interstitial Li and/or hydrogen, ubiqutous in the wurtzite phase, is inhibited by the close-packed nature of the rocksalt structure, which also exhibits relatively high absolute valence band edge that promotes low hole effective mass and hole delocalization. Resulting concentrations of free holes are predicted to exceed ∼1019 cm−3 under O-rich synthesis conditions while under O-poor conditions the system remains n-type dopable. In addition to revealing compelling opportunities offered by the metastable rocksalt structure in realizing a long-sought p-type ZnO our results present polymorphism as a promising route to overcoming strong doping asymmetry of wide-band gap oxides.
@article{arxiv.1802.00360,
title = {Metastable rocksalt ZnO is $p$-type dopable},
author = {Anuj Goyal and Vladan Stevanović},
journal= {arXiv preprint arXiv:1802.00360},
year = {2021}
}
Comments
Updated with actual Fig. 3. In original submission, Fig. 3 was an older version, which does not include possibility of different geometries for hydrogen interstitial and thereby, has slightly inaccurate position of H(1/1-) transition