Probing of Carrier Recombination in n- and p-Type 6H-SiC Using Ultrafast Supercontinuum Pulses

Excess carrier dynamics in 6H-SiC substrates with n- and p-type moderate doping were detected using femtosecond pump-probe measurements with supercontinuum probing. Band-to-band recombination and carrier trapping were determined as the main recombination processes in both materials. Spectral fingerprints corresponding to each of these recombination components were obtained using the global and target analysis. It was shown that, in spite of background doping, the band-to-band recombination in 6H-SiC is dominated by the excess electron absorption component and the carrier trapping is dominated by the excess hole absorption.

Charge Carrier Relaxation after Subbandgap Excitation in Doped a-Si:H

Charge carrier dynamics in doped and undoped a-Si:H after subbandgap excitation at 1064 nm was followed by transient photoconductivity experiments. The kind of optical transitions induced by 1064 nm light is strongly dependent on the position of the Fermi-level. This allows the seperation of excess electron and excess hole kinetics as in n-doped samples mainly mobile electrons and in moderately p-doped samples mainly free holes are generated by 1064 nm light. From comparison of the photoconductivity after 532 nm and 1064 nm excitation it is inferred that the rate controlling step for the electron decay is the availability of free holes.