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Strain‐Engineered Modulation on the Electronic Properties of Phosphorous‐Doped ZnO
Author(s) -
Lu YingBo,
Dai Ying,
Wei Wei,
Zhu Yingtao,
Huang Baibiao
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300664
Subject(s) - materials science , band gap , wurtzite crystal structure , acceptor , antibonding molecular orbital , crystallography , condensed matter physics , electronic band structure , doping , direct and indirect band gaps , strain (injury) , chemistry , electron , optoelectronics , atomic orbital , hexagonal crystal system , physics , quantum mechanics , medicine
The modulation of strain on the electronic properties of ZnO:P is investigated by density functional theory calculations. The variation of formation energy ( E f ) and band structure with strains ranging from −0.1 to 0.1 are considered. Although both the conduction band minimum (CBM) and the valence band maximum of ZnO are antibonding states, the CBM is more sensitive to strain, reducing the band gap with an increase in strain. P‐substituted O (P O ) defects show poor p‐type conductivity due to a smaller E f and lower lying acceptor levels as a consequence of lattice expansion. The E f of P‐substituted Zn (P Zn ) defects decreases under tension, owing to the release of strong repulsive stress induced by excess electrons from P Zn . The donor energy band of P Zn broadens under tensile strain, which benefits n‐type conductivity. For Zn vacancies (V Zn ) and P Zn –2V Zn complexes, the distances between the O atoms around V Zn are so large that repulsive and attractive interactions become weak, which results in an easy release of the strain. We herein present for the first time that the E f values of V Zn and P Zn –2V Zn complexes decrease under both tension and compression, or in the high‐pressure rock‐salt phase. Under a strain of 0.1 the P Zn –2V Zn complex shows the smallest E f . Under −0.07 strain the wurtzite/rock‐salt phase transition occurs and the direct band gap becomes an indirect one. The variation of band structures in the rock‐salt phase is similar to that in the wurtzite phase. Consequently, the p‐type conductivity of ZnO:P can be improved with an increase in solubility of P Zn –2V Zn or V Zn defects.