Photoresponse of zinc phosphide thin films grown by ionized cluster beam deposition

The photoresponse of zinc phosphide (Zn ₃P ₂) thin films grown by ionized cluster beam deposition has been studied. The spectral response shows a threshold at around 1.6 eV coincident with the optical absorption edge of Zn ₃P ₂. The photoresponse of Zn ₃P ₂ films grown at an acceleration voltage below 0.8 kV was small in spite of its low resistivity. As growth temperature increased above 180°C, the photoresponse increased resulting from the decrease of resistivity due to a preferential orientation along c-axis. The resistivity and the X-ray diffraction peak ratio {(004)}/{(400)} did not change by hydrogen passivation, whereas the photoresponse was greatly improved probably due to the increase of carrier lifetime and/or quantum efficiency.