Transient voltage behavior of free-standing porous silicon layers

The transport in free-standing porous silicon layers has been investigated by applying a current step to samples with a four contact geometry and by measuring the voltage time behavior across the voltage contacts. The voltage response showed a transient waveform typical of a network with two time constants and a continuous regime for very long times. The values of the time constants tau(1) and tau(2) differ noticeably, tau(1) and tau(2) being in the range 0.1-10 milliseconds and 10-150 milliseconds, respectively. The dependence of the time constants on the current step amplitude and on the temperature has been also investigated. Both tau(1) and tau(2) showed a temperature activated behavior, which can be related to the resistance behavior vs absolute temperature. (C) 1996 American Institute of Physics.