Space charge limited conduction in a-(Ge20Se80)1?xSnx thin films

The present paper reports the dc conductivity measurements at high electric fields in vacuum evaporated amorphous thin films of (Ge₂₀Se₈₀)_1?xSn_x glassy alloys where 0 < x < 1. Current–voltage (I–V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behavior is observed. However, at high electric fields (E ～ 10⁴ V/cm), non-ohmic behavior is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, the density of defect states (DOS) near Fermi level is calculated. These results show that the effect of incorporation of Sn in the Ge–Se system is quite different at its low and high concentration. This peculiar role of third element Sn as an impurity in the pure binary Ge₂₀Se₈₀ glassy alloy is also discussed.