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HL: Halbleiterphysik

HL 30: Photovoltaik

HL 30.4: Vortrag

Mittwoch, 26. März 2003, 15:15–15:30, BEY/81

Bandgap engineering for HfS_xSe_2−x — •Christof Gaiser, Thorsten Zandt, Ralf Serverin, Alica Krapf, Christoph Janowitz, and Ricardo Manzke — Institut f. Physik Humboldt-Universität zu Berlin Invalidenstrasse 110, 10115 Berlin

The bandgaps of HfS₂(∼2eV) and HfSe₂(∼1.1eV) cover the range of ideal bandgaps for photovoltaic applications which is for a single junction cell about 1.45eV and for a two junction cell about 1.1eV and 1.8 eV . Additionally, in favor of applications the transition metal dichalcogenides have a strong tendency to grow as thin films due to their quasi two-dimensional character. Employing the chemical vapor transport method single crystals of the ternary semiconductor HfS_xSe_2−xwere grown with 9 different compositions for systematic studies in the range 0≤x≤2. They were characterized in detail by LEED, Laue diffraction and EDX. In addition the absorption was measured, revealing an absorption coefficient α(hν) that was remarkably high for an indirect semiconductor. The determined band-gaps of HfS_xSe_2−xshow a nearly linear dependence on x, which is perfect for band-gap engineering. Furthermore, in the region of the band-gap an exponential behaviour of α(hν)is observed, which could be interpreted as an Urbach tail.