Electrical properties of As_xSe_1-x (x ≤ 0.05) Mott-barriers

We have experimentally measured the current-voltage and capacitance-voltage characteristics of Au/amorphous As_xSe_{1 - x} (x ≤ 0.05)/Zr trilayer structures at temperatures from 4 to 295 K. The observed capacitance of structures with an amorphous As_xSe_{1 - x} (a-As_xSe_{1 - x}) thickness of × 0.4 to × 2.8 μm does not significantly change over the entire range of applied bias (- 5 V to 5 V), indicating that the a-As_xSe_{1 - x} films are fully depleted and thus the structures are Mott barriers. The current-voltage (I-V) characteristics of the a-As_0.03Se_0.97 device at low (< 3000 V/cm) to moderate fields (3000 V/cm-10000 V/cm) follow the predictions of trap limited space charge conduction theory, as they exhibit Ohmic behavior at low fields and trap limited space charge current at moderate fields. According to the trap limited space charge current model of Lampert, the a-As _0.03Se_0.97 film has an effective hole mobility, Θμ (with Θ < 1), of × 5 × 10^{- 7} cm ²/V-sec at 295 K. This value is similar to, but consistently lower than previously reported mobilities inferred from time of flight measurements. The current at high fields (> 10⁴ V/cm) increases rapidly with applied field as a result of carrier emission from localized states and is consistent with transport by the Poole-Frenkel mechanism. A permanent transition to a high conductance state (× 10^{- 3} S) is observed after exposure to very high electric fields (× 4 × 10⁵V/cm).