Determining carrier mobility with a metal–insulator–semiconductor structure

The electron and hole mobility of nickel-bis(dithiolene) (NiDT) are determined in a metal–insulator–semiconductor (MIS) structure using admittance spectroscopy. The relaxation times found in the admittance spectra are attributed to the diffusion time of carriers to reach the insulator interface and via Einstein’s relation this yields the mobility values. In this way, an electron mobility of 1.9×10-4cm2/Vs and a hole mobility of 3.9×10-6cm2/Vs were found. It is argued that the low mobility is caused by an amphoteric mid-gap trap level. The activation energy for electrons and holes from these traps is found to be 0.46 eV and 0.40 eV, respectively.