Absorption and photocurrent properties of thin ZnS films formed by pulsed-laser deposition on quartz

The absorption and photocurrent properties of thin film ZnS on quartz glass formed by pulsed-laser deposition have been studied experimentally and theoretically at room temperature. Using the Lorentzian function to describe the exciton density of states, we show that the absorption is strongly influenced by excitonic formation. The theory for the absorption, however, does not describe the PC spectra of the film since the exciton remains electrically neutral up to fields of 1 kV/cm due to the high binding energy of 36 meV. Therefore, the fundamental absorption according to density of states and Urbach rule determines the shape of the photocurrent spectrum.