Atmosphere-Dependent Photoconductivity of ZnO in the Urbach Tail

Figure 3

(a) The optical absorption coefficient of ZnO exhibits the strong absorption due to the direct bandgap in the UV range and the Urbach tail in the visible range. Our experiment employs both spectral regions as probe for photoconductivity measurements. (b) Photoluminescence spectrum at 300 K shows emission due to NBE at 3.3 eV and a broad band in the visible range related to defects.