Cathodoluminescence studies of electron irradiation effects in n-type ZnO

The lifetime of non-equilibrium carriers in n-type unintentionally doped ZnO increases when the sample is exposed to the electron beam of a scanning electron microscope. This is observed by studying the ZnO cathodoluminescence (CL) spectra at different irradiation time durations and temperatures. We found that the decrease in the CL spectra's peak intensity is related to a thermo-activated energy barrier, determined by the calculated activation energy value of 259 ± 30 meV. This energy value comes close to the defect energy level of the zinc interstitial, which is possibly the nature of the energy barrier responsible for this decrease.