Microstructure and properties of epitaxial antimony-doped p-type ZnO films fabricated by pulsed laser deposition

Abstract

Antimony-doped p-type ZnO films epitaxially grown on (0001) sapphire substrates were fabricated by pulsed laser deposition at 400–600°C in 5.0×10−2Torr oxygen without postdeposition annealing. The films grown at 600°C have among the highest reported hole concentration of 1.9×1017cm−3 for antimony doping, Hall mobility of 7.7cm2∕Vs, and resistivity of 4.2Ωcm. Transmission electron microscopy reveals that the p-type conductivity closely correlates to the high density of defects which facilitate the formation of acceptor complexes and the compensation of native shallow donors. The thermal activation energy of the acceptor was found to be 115±5meV and the corresponding optical ionization energy is ∼158±7meV.

Surface morphology and photoluminescence studies of Sb-doped ZnO layers grown using MOCVD

“…This is surprising since one may have expected an increase of the Sb content at low VI/II ratios, if Sb atoms are incorporated in oxygen sites. This may confirm the possibility that Sb atoms replace Zn atoms in the ZnO matrix [12,13].…”

The role of stacking faults and their associated 0.13 eV acceptor state in doped and undoped ZnO layers and nanostructures

“…Obviously, both transitions compete for free carriers and show total anti-correlation [2]. As an example, the findings on a (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) side facet are shown in Fig. 2.…”

“…As an alternative explanation we suggest, that a high number of SFs might be created due to the presence of group V atoms during growth, which (over-) compensate the n-type background conductivity and lead to a locally strongly fluctuating Fermi level. Indeed, recent TEM microscopy on such doped samples finds a high concentration of partial dislocations and stacking faults [11,12]. However, not only after group V doping this 3.314 eV PL band is found, but also after doping by Mn [13] or doping by Ag [14] introduces this defect band in PLpresumably due to stacking faults introduced in the crystal in high concentration.…”

“…(iii) Hall measurements in van der Pauw configuration give contradictory results when permutating the connections. (iv) Mostly very high dopant concentrations (up to 1%) are necessary to obtain a hole concentration of some 10 18 cm À3 [11]. (v) The carrier mobility of holes is unexpectedly low.…”

Stable interstitial dopant–vacancy complexes in ZnO

“…Experiments have shown that conductivity type can have a strong spatial dependence related to sample topography 13 , that p-type conductivity is associated with increased dislocation density 8 , and that luminescence may be either correlated 14 or anti-correlated 15 with the presence of stacking faults and dislocations. For these reasons, acceptors localized at stacking faults 14 and hole accumulation at interfaces with precipitates 16 have also been proposed as possible causes of the p-type measurements, rather than D Zn -2V Zn acceptor complexes.…”