Figure 3 EL spectra performed under 1 MHz pulse biasing with several pulse amplitudes. Figure 4 dc EL spectra at several temperatures, under low bias to avoid heating of the device.
Solid curves are linear fits in the low and high current injection regimes.
Figure 6 EL spectra recorded at 7V amplitude pulses of different duration. Figure 7 Time evolution of the violet EL intensity. Figure 9 Violet EL intensity observed after different rest time t OFF . RD and Si stand for shallow donors, SA for shallow acceptors, DLD and DLA for deep levels behaving as donors and acceptors, respectively, and YBA for the deep acceptors involved in the yellow luminescence.