Room temperature electroluminescence efficiency as a function of forward bias voltage,VF, shows that there are two recombination regions in device qualitya‐Si:H diodes. The recombination threshold voltage,Vt1, is 0.48–0.49 V. The transition voltage,Vt2, is 0.7–0.8 V. WhenVt1<VF<Vt2the electric field strongly enhances the luminescence efficiency, whenVF≳Vt2the luminescence efficiency is almost independent of the electric field. The increase of the EL efficiency in the low injection regime depends on the competition of radiative and nonradiative recombination. ©1995 American Institute of Physics.