Direct Evidence for As as a Zn-Site Impurity in ZnO

Abstract

Arsenic has been reported in the literature as one of the few p-type dopants in the technologically promising II-VI semiconductor ZnO. However, there is an ongoing debate whether the p-type character is due to As simply replacing O atoms or to the formation of more complicated defect complexes, possibly involving As on Zn sites. We have determined the lattice location of implanted As in ZnO by means of conversion-electron emission channeling from radioactive 73 As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites but in its large majority substitutional Zn sites. Arsenic in ZnO (and probably also in GaN) is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system.

Fabrication and Characterization of As Doped p-Type ZnO Films Grown by Magnetron Sputtering

“…The As (3d) binding energies of the As-O and As-Zn bonds were associated with the values of ~45 eV and 41eV, respectively. The observation of the 44.8eV single peak in the As (3d) binding energy in XPS spectrum of ZnO:As film implied that the As atoms occupied the Zn site of the ZnO lattice, which was consistent with the results obtained by Wahl (Wahl, et al, 2005). Asymmetric O1s peak was detected for the sample, which had a shoulder at the higher binding energy side fitting with Gaussian distribution.…”

Stable interstitial dopant–vacancy complexes in ZnO

“…Their presence is supported by a low calculated formation energy and agreement of their calculated transition levels with levels identified in experiments 2-10 , which range from 0.09 to 0.34 eV above the valence band maximum (VBM). In addition, D Zn -2V Zn complexes are consistent with experimental evidence that implanted As and Sb incorporate on Zn sites 11,12 . Furthermore, p-type conductivity emerging from these complexes is consistent with the need for O-rich growth or annealing conditions to create p-type samples, as these defects are stabilized by high oxygen partial pressures.…”

Lattice location of the group V elements Sb, As, and P in ZnO

“…3) and a diversity of interstitial sites resulting from displacements along or off the c-axis 49 . The theoretical emission channeling patterns were calculated by means of the "manybeam" theory of electron diffraction in single-crystals 54 , where u || and u ⊥ represent one-dimensionally projected rms displacements u 1 parallel and perpendicular to the c axis, respectively.…”