Output power saturation in InGaAsP/InP surface emitting LEDs V. Rakovics, S. Püspöki, and I. Réti Research Institute for Technical Physics and Materials Science InGaAsP/InP LED’s are widely used for optical telecommunication, and for selective spectroscopy in the near infrared range. Observations regarding the temperature sensitivity and power saturation of InGaAsP lasers and light emitting diodes (LED's) have led to extensive studies to find the responsible mechanisms -. At high current densities the efficiencies of the diodes drop quickly. As a result of current heating, the junction temperature increase in CW operation, and the emitted power saturate at a certain current. The light-current curves are not linear even in short pulse operation. We prepared and investigated nine different wavelength InGaAsP/InP surface emitting double heterostructure LEDs. Silicon oxide defined different area diodes were prepared. The doping level in the P-InP confining layer was fixed in order to keep the magnitude of the leakage current. Optical power and spectral characteristics of the diodes were investigated as a function of driving current and case temperature. At fixed emitting wavelength, the maximum power is proportional to the volume of active layer. Figure 1 shows the light-current characteristics of the LED’s. Short wavelength diodes perform better at high current densities. At 3 A, the longest wavelength diodes have only third optical power than the shortest wavelength LED’s. The output power saturation and the temperature sensitivity of the diodes depend on the composition of the active layer. Band-to-band Auger recombination greatly affects the radiance saturation in InGaAsP LED's. Fig.1. Output power of the different wavelength LED’s as a function of pulse current Acknowledgements This work was supported by Hungarian National Research Fund (AQUANAL project No. NKFP-3A-07904) References:  A. Sugimura, IEEE Journal of Quantum Electronics, 17 (1981) 441 - 444.  L. C. Chiu, K. L. Yu, S. Margalit, T. R. Chen, U. Koren, A. Hasson, A. Yariv, IEEE Journal of Quantum Electronics QE-19 (1983) 1335-1338.