Space-charge-limited current analysis in amorphous InSe thin films

Abstract

The study of space-charge-limited currents (SCLC) in amorphous InSe thin films is presented. The temperature-dependent current–voltage (J–V) measurements were carried out for TO/a-InSe/Au sandwich structures in the range of 200–320 K. For all samples, ohmic behavior was observed up to an electric field strength of about 2×105 V cm−1. From the temperature dependence of conductivity data, the position of the thermal equilibrium Fermi level Efo is determined as 250 meV above the valence band Ev. At higher electric field strength values in the SCLC regions, the proportionality constant of voltage changes is between 2 and 2.9 with temperature. The analysis of J–V characteristics using the SCLC method and analytical approach for the determination of density of states (DOS) in the energy range of 190–250 meV shows that DOS changes between 3.8×1017−1.7×1018 eV−1cm−3 with energy. The energy distribution of DOS is temperature independent indicating that the SCLC in these amorphous films is related to the bulk, not to the surface layer between the contact and the film.