Switching effects in polycrystalline cadmium telluride films

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Abstract
Experimental observations of switching phenomena in evaporated polycrystalline CdTe films are described. The off-state behavior of CdTe samples sandwiched between crossed metallic electrodes was investigated using standard I-V curve tracing techniques. Symmetric I-V characteristics were observed for different combinations of metallic electrodes. The CdTe samples exhibited Ohmic conduction (ρ∼108 Ω cm) for small applied voltages followed by an exponential current region of the form I=I0 exp(V/V0) which terminated with memory switching. The resistance of the memory on state was typically 100–200 Ω. A single reset voltage pulse (∼ 1 μsec duration, 50 nsec rise time) of magnitude comparable to the switching voltage and applied through a 10-K load resistor usually sufficed to return the samples to the off state. The switching voltage was found to increase with film thickness in an approximately linear fashion. A rudimentary form of threshold switching was also detected when the samples were subjected to short voltage pulses. Many of the observations can be accounted for by considering the CdTe films to be crystalline trap-dominated relaxation semiconductors.

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