Current-voltage characteristics of Cr-doped hydrogenated amorphous silicon-V (Cr/p+a-Si:H/V) analogue memory switching devices have been measured over a wide range of device resistance from several kilo-ohms to several hundred kilo-ohms, and over a temperature range from 13 K to 300 K. Both the bias and temperature dependence of the conductance show similar characteristics to that of metal-insulator heterogeneous materials (i.e. discontinuous or granular metallic films), which are analysed in terms of activated tunnelling mechanism. A modified filamentary structure for the Cr/p+a-Si:H/V switching devices is proposed. The influence of embedded metallic particles on memory switching is analysed and discussed.