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81 results on '"Duan, X. M."'

46. Quantum Effects of Strain Influence on the Doping Energy in Semiconductors

Author

Wang, Z. T., Chen, Shiyou, Duan, X. M., Sun, D. Y., and Gong, X. G.

Subjects
Condensed Matter::Materials Science, Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Applying external strain is an efficient way to manipulate the site preference of dopants in semiconductors, however, the validity of the previous continuum elastic model for the strain influence on the doping forma- tion energy is still under debate. In this paper, by combining quantum mechanical theoretical analysis and first-principles calculations, we show that if the occupation change of different orbitals caused by the strain is negligible, the continuum elastic model is valid, otherwise it will fail. Our theory is confirmed by first-principles calculation of Mn-doped GaAs system. Moreover, we show that under compressive strain the hole density, thus the Curie temperature TC can increase in Mn-doped spintronic materials., 4 pages + 2 figures

Published
2011

48. Single-frequency, Q -switched Er:YAG at room temperature injection-seeded by an Er:YAG nonplanar ring oscillator.

Author

Deng, Y, Yu, X, Yao, B Q, Dai, T Y, Duan, X M, and Ju, Y L

Abstract

We demonstrate a diode-pumped, injection-seeded Q-switched Er:YAG laser operating at room temperature. The diode-pumped single-frequency Er:YAG monolithic nonplanar ring oscillator (NPRO) was used as the seed laser emitting at 1645.22 nm with a maximum output power of 550 mW. Single-frequency, Q-switched operation of the Er:YAG laser was achieved by injection seeding. The output energy of the single-frequency Q-switched pulse was 3.5 mJ, with a pulse width of 195 ns at a repetition rate of 100 Hz. [ABSTRACT FROM AUTHOR]

Published
2014
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49. Design of shallow acceptors in ZnO through early transition metals codoped with N acceptors.

Author

Duan, X. M., Stampfl, C., Bilek, M. M. M., McKenzie, D. R., and Su-Huai Wei

Subjects
*TRANSITION metals, *ZINC oxide, *WURTZITE, *SEMICONDUCTOR doping, *IONIZATION (Atomic physics)
Abstract

We perform first-principles density-functional theory calculations to study the atomic and electronic properties of early transition metals (Zr, Ti, Y, and Sc) codoped with N in wurtzite ZnO. By incorporating early transition metals Ti, Zr, Y, and Sc with N into ZnO simultaneously, we find that forming complexes (Zr-2N), (Ti-2N), (Y-N), and (Sc-N) induces fully occupied impurity bands with the N 2p character above the valence band maximum of host ZnO. With further doping of N in ZnO, the systems (Zr-2N):N, (Ti-2N):N, (Y-N):N, or (Sc-N):N have acceptor ionization energies lower than that of the isolated N acceptor in ZnO. Under different growth conditions (i.e., using an N2O or NO source for the nitrogen atoms), we calculate the formation energies of the defect complexes and compare the dopability of the selected codoped systems. Our results show that the valence band maximum characteristic of ZnO can be altered by compensated donor-acceptor pairs, thus improving the p-type dopability. [ABSTRACT FROM AUTHOR]

Published
2011
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