Thermal and nonthermal switching in a-CdAs2 thin-film sandwich structures: The effect of bias rate

Abstract

Thin-film devices incorporating a-CdAs2 which display current-controlled negative differential resistance (CNDR) under quasistatic bias conditions are described. By biasing devices with short rapid rise-time pulses, threshold switching is observed to set in at much higher voltages than needed for quasistatic CNDR. The transition region between these extremes has been studied by biasing the devices with an adjustable power ramp whose slope was varied over many orders of magnitude. Under ramp bias, the devices show CNDR with a turnover voltage approaching the quasistatic value for bias times to turnover of 0.1 sec or longer. More rapid bias rates result in CNDR with a strongly increasing turnover voltage with increasing bias rate. Analysis of the temperature of the device during ramp bias indicates that the turnover mechanism is Joule-heat induced for bias times of 0.5 sec or longer, ’’electronic’’ for bias times of 10−3 sec or less, and of mixed origin in between.