Abstract:
The luminescence intensity saturation of LEDs with quantum wells at an excessive concentration of carriers in the active region has been studied. The experimental electroluminescence spectra for a LED (area 1 mm$^2$) based on the Al$_{0.2}$Ga$_{0.8}$As $p$-$i$-$n$ junction with six In$_{0.1}$Ga$_{0.9}$As quantum wells are analysed and the experimental dependence of the main peak electroluminescence intensity on current density is obtained. At low currents, this dependence is linear (proportional) and sublinear at high currents. Approximation of the sublinear region made it possible to estimate the magnitude of the current $J_{sat}$, at which saturation begins. The energy diagram of the quantum well is also considered and a theoretical model is proposed that makes it possible to independently calculate the value of $J_{sat}$. For the sample under study, the calculation showed that $J_{sat}\sim$ 30 A/cm$^2$. In this case, the experimental value for the LED with six quantum wells was 210 A/cm$^2$, which in terms of one well gives 35 A/cm$^2$. The close correspondence between the calculated and experimental values confirms the applicability of the proposed model. An increase in the width of all electroluminescence peaks from quantum wells with increasing current was also experimentally observed.
Keywords:led, saturation of electroluminescence intensity.
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