Space-charge-limited currents in insulators with two sets of traps distributed in energy: Theory and experiment

Abstract

The theory of space‐charge‐limited current (SCLC) flow in insulators has been extended to include the case of materials with two sets of traps. By using the regional approximation method, two theoretical current‐voltage characteristics have been derived for this situation, referring to different starting positions of the thermal equilibrium Fermi level in the forbidden gap. The general case of traps not localized at a single energy, but rather distributed in energy, has been taken into account for the first time. To account for the effect of the distribution of traps around a single energy, say E_t, on SCLC, the following distribution function has been used: H (E) = (N_t/kT_t) exp[(E−E_t)/kT_t] {exp[(E−E_t)/kT_t]+1}⁻². The theory has been compared with the experimental results obtained in n‐type GaSe(I₂) single crystals, which show current‐voltage characteristics exceptionally similar to the theoretical ones. From the analysis, two electron traps have been found to be centered at 0.63 and 0.42 eV from the conduction band. These results have been confirmed by a different method of analysis of SCLC curves and by other measurements. Finally, two particular cases are analyzed, already experimentally evidenced in GaS and nominally undoped p‐type GaSe.