High-density photo-excited carriers in ZnO epitaxial thin films

摘要

In 1997, stimulated emission and optically pumped laser action in ZoN epitaxial thin films have been reported ar room temperature [1]. These emissions were assigned as due to an exciton-exciton collision or an electorn-hole plasma (EHP), and precise lasing properties have been reported [2]. In order to study the precise dynamical properties of photo-excited carriers in ZnO thin films, we measured time-resolved absorption and photoluminescence (PL) spectra using a sub-picosecond pulse laser [3, 4]. We employed a pump-probe method for the former experiment and up-conversion method for the later one. The samples used here were fabricated on a sapphire substate by a plasma enhanced MBE method[5].