Low temperature electrical resistivity on the insulating side of the metal-insulator transition in CdAs(2)semiconductor

In this paper, different hopping theoretical mechanisms have been employed to explain the charge conduction in insulating disordered CdAs2 semiconductor. The low temperature electrical resistivity of four insulating samples, referenced CdAs2(1), CdAs2 (2), CdAs2 (3) and CdAs2 (4) was investigated in order to know the effect of temperature on the carrier transport. A close examination of the resistivity-temperature curves displays that the general hopping process ln rho similar to T-alpha is operative at low temperatures in our four samples. The three samples (1), (2) and (3) exhibit crossover behavior between Mott (alpha = 1/4) and Efros-Shklovskii (alpha = 1/2) variable range hopping conduction upon variation of temperature, and the crossover criterion is also studied. For sample (4), the experimental results show that the carrier transport obeys T-2/3 dependence. A possible explanation of this mechanism has been based on the adaptation of the existing Efros-Shklovskii variable range hopping model. This law is achieved by replacing the conventional Miller-Abrahams expression for hopping probability by another one, which introduces the local energy fluctuations involved in the electron transfer.