Time-resolved microwave technique for ultrafast charge-carrier recombination time measurements in diamonds and GaAs

Abstract

Recombination times of laser-excited charge carriers in natural diamond crystals, polycrystalline chemical vapor deposited (CVD) diamond films, and GaAs wafers were measured with 1 ns time resolution by a microwave-radiation technique. A waveguide scheme was applied to record time-dependent reflection and transmission of 140 GHz cw radiation. The measured recombination carrier lifetimes in the bulk of natural and CVD diamond samples were found to be of 1–3 ns. In GaAs, a distinguishing difference between the bulk (15 ns) and surface (3.5 ns) recombination times was observed. To validate the applicability of the developed technique, a computer simulation of the microwave-radiation interaction with excited plane–parallel specimens has been performed applying the Fabry–Perot resonator theory and the classical Drude model.