Trap-recharging waves versus damped, forced charge-density oscillations in hexagonal silicon carbide

Resonant excitation of space-charge waves (SCW) by means of an oscillating light pattern has been investigated in hexagonal silicon carbide with 4H and 6H stacking sequence, respectively. The experimental data set can be well explained by the existence of trap recharging waves for the 4H sample and allows to determine the product of mobility and lifetime μτ=(5.7   ±   0.6) × 10<Superscript>-7</Superscript> cm<Superscript>2</Superscript>/V, and the effective trap density N<Subscript>eff</Subscript>=(8.0 ±   1.0) × 10<Superscript>13</Superscript> cm<Superscript>-3</Superscript>, respectively. The data set of the 6H polytype indicates a comparably smaller effective trap density, but an unambiguous assignment to the existence of trap recharging waves fails. Taking into account the general classification of material parameters which provides the existence for SCW, the particular case of damped, forced charge-density oscillations can be concluded. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007