Light saturation of InGaAsP-InP LED's

The saturation behavior of the spontaneous light-current characteristic of InGaAsP (
\lambda = 1.3 \mu
m) lasers and light emitting diodes are investigated as a function of injection level and temperature. For carrier injection levels below that at which optical gain is observed, it is shown that a nonradiative Auger recombination mechanism is consistent with the observed saturation behavior of the spontaneous emission intensity of lasers. Further evidence of the importance of Auger recombination at these low injection levels is provided by the dependence of the nonradiative component of the measured carrier lifetime (τ
A
) on injection level (
n
) where it is found that
\tau_{A}^{-1} \propto n^{2.1}
. For injection levels above that required to achieve optical gain we report the direct observation of superlinear emission due to single pass gain in edge emitting LED's. The onset of this superluminescence at low temperatures (
T < 200
K) is found to correspond with the onset of saturation of the spontaneous emission from the sides. These results show that both Auger recombination and superluminescence should be taken into account when the electrooptical characteristics of InGaAsP LED's are calculated.