Carrier transport mechanism has been studied in thin insulating hydrogenated amorphous carbon (a-C:H) films. The layers were prepared by plasma polymerization of methane (CH4) at a frequency of 20 kHz. Electron mobility was derived from time-resolved luminescence experiments. Between the application of a rectangular voltage pulse and the first appearance of electroluminescence (EL) a time lag exists, which depends on the pulse height. Transit times are in the order of 10(-3) to 10(-6) s in a voltage range between 10 and 25 V. And the estimated electron mobility varies accordingly from 8 x 10(8) to similar to10(-6) cm(2)/ (Vs). The field dependence of the carriers mobility is characteristic of Poole-Frenkel-detrapping conduction model, and thus confirms the results obtained by do experimental data. (C) 2002 Elsevier Science B.V. All rights reserved.