Time‐resolved absorption and luminescence following electron‐hole pair creation in ZnO

We report transient absorption induced by electron-hole excitation in undoped ZnO. A laser pump/continuum probe method covers 2–300 ps, and an electron pulse with lamp transmission covers 8–300 ns. The broad absorption spectrum increases monotonically with wavelength from 900 to 1600 nm. Following a reasonable hypothesis that the free-carrier-like induced infrared absorption is proportional to the total number of free carriers, excitons, and shallow-trapped carriers in the sample, these data allow setting an upper limit on the quantum efficiency of a specified lifetime component of luminescence. For the undoped commercial ZnO studied in this report, the quantum efficiency of room temperatur…