Single-carrier space-charge controlled conduction

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Abstract
Single-carrier space-charge controlled conduction in metal-insulator-metal structures has been studied. The dc J-V characteristics have been calculated over an extended range of current for insulator films of different thicknesses with and without traps. It is found: (i) The current is proportional to voltage at low currents, the proportionality factor depending on the injecting contact carrier concentration, insulator thickness, and trap density. (ii) At moderate currents, the J-V characteristics can be approximated only over a limited range of currents by a power law with the exponent n depending on the injecting contact carrier concentration, insulator thickness, and trap content. (iii) At high currents the conduction is ohmic and the characteristics are identical for insulators with or without traps. The special case of identical carrier concentrations at both contacts is also discussed. It is found that in this particular case the square law in voltage and the cubic dependence in thickness become only good approximations when the normalized trap density M⩾103. The proportionality factor is slightly larger than the value 1.125 obtained from the Mott–Gurney simplified theory and varies slowly with insulator thickness.