Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 4: Focussed session: Transparent conductive oxides I (jointly with HL, DS)

O 4.3: Topical Talk

Montag, 14. März 2011, 12:15–12:45, WIL A317

Bulk semiconducting oxides: crystal growth and physical properties — •Roberto Fornari — Leibniz Institute for Crystal Growth, IKZ, Max-Born-Str. 2, 12489 Berlin

Semiconducting oxides have attracted considerable interest in the last few years. In addition to the widely studied ZnO, much attention has recently been devoted to Ga2O3, In2O3 and SnO2. The epitaxial growth has already been achieved on different hetero-substrates; however due to the relatively poor crystallographic quality of the obtained layers it was not possible to get devices or even reliably measure their physical properties so far. It is thus urgent to provide homo-substrates which may allow the deposition of high-quality epilayers with low residual carrier density and fewer extended defects. IKZ has recently undertaken an effort to grow large single crystals of these oxide compounds. In this presentation the growth of transparent semiconducting Ga2O3 single crystals will be reviewed. Single crystals with diameter of 18 mm diameter and 50-60 mm length were grown along the b-axis from an Iridium crucible under a dynamic protective atmosphere. The transmission in IR-region was directly correlated with the free carrier concentration and was found to depend on the growth atmosphere and/or post growth annealing. Typical electrical properties at room temperature are: resistivity = 0.12 Ohmcm, electron concentration = 2-5E17 cm-3 and mobility = 110 cm2/Vs; these results seem to derive from a donor level with activation energy of about 32 meV. Results of thermodynamic calculations, dislocation density studies, ICP-OMS, DTA, EPR and High Resolution TEM are also presented.