Brightness waves and brightness-current curves in alkali halide electroluminescence

Abstract

A kinetic model has been formulated for electroluminescence (EL) in alkali halide crystals (AHC) on the basis of existing measurements and theoretical concepts on prebreakdown electroluminescence. An expression is derived for the intensity, which contains parameters S1, S2, and S3, which are the probabilities of excitation, ionization, and stepwise ionization for the emission centers when an electron passes through section ρ. If the current density is not more than 1 A/cm2, the EL brightness waveform reproduces the exciting current pulse within the excited-state lifetime, with the amplitude directly proportional to the current density. As the current density increases, the wave becomes damped, because the ionized emission centers are excluded from the EL. The observed waves for KBr have been examined for current densities up to 1 A/cm2 and agree with the theoretical ones. A method is proposed for determining Sx as a function of emission-center concentration from the initial parts of the brightness-current curves.