THz photoconductivity dynamics of semiconductors from sub-nanosecond to millisecond timescales

The pump-probe delay in optical pump, terahertz probe (OPTP) spectroscopy (time-resolved THz spectroscopy) is typically varied using a mechanical delay stage, which limits the delay range to a few nanoseconds. Here we demonstrate an inexpensive modification to typical OPTP setups that extends the range of pump-probe delays to beyond millisecond timescales, whilst retaining the sub-nanosecond resolution required to resolve faster processes that are often present at early times after pulsed optical excitation. We used this new method to investigate the photoconductance dynamics in a range of materials including III-V semiconductors, metal halide perovskites, germanium and silicon, whose carrier lifetimes range from a few nanoseconds to milliseconds.