Abstract

There has recently been renewed interest in AlGaInAs 1.3/1.55 mm lasers for high speed data communications. This laser system is an attractive alternative to the traditional GaInAsP lasers predominately because of higher characteristic temperature, T₀. For example, in the past year, T₀ values for AlGaInAs lasers have typically been observed to be around 80K (with maximum 143K[1]) while T₀ for GaInAsP based laser diodes have been 50-55K with a maximum ~70K[2]. This improved temperature sensitivity is crucial for future high speed uncooled data communications systems where active components may be required to operate at temperatures as high as 80-90°C. To date however little analysis has considered the high temperature, high speed operation of InGaAsP devices. In this paper therefore we have evaluated the feasibility of AlGaInAs lasers for high-speed modulation at high temperatures and compared them with performance of GaInAsP devices. The study has involved both drift-diffusion and rate equation simulations so that the temperature dependence of material parameters can be assessed in terms of overall dynamic performance. The differential gain, g′, is estimated by means of drift-diffusion simulations of gain as a function of carrier density in QWs. At room temperature g′ for AlGaInAs was found up to 2 times higher then in similar GaInAsP structures and up to 3 times higher at 95°C. A dynamic three level rate equation model including carrier transport is then used to predict and compare the performance of ridge laser diodes using the two material systems. In good agreement with recent experiments (preprint of Massara et al.), a maximum operating temperature of 70°C is predicted for the InGaAsP material system and small signal simulations indicate resonance frequencies at bias current of 50mA above threshold of 8 9GHz and 5.1GHz at temperatures of 25°C and 70°C respectively. The simulation of large signal modulation with a 27-1 pattern at 12.5Gb/s indicates a significant broadening in the one and zero rails of the eye diagram, in close agreement with experiment. Simulations for the AlGaInAs active layer, however, indicate resonance frequencies of 15.0GHz at 25°C and 12.3GHz at the elevated temperature of 95°C without any observable patterning under large signal modulation as shown in Figute 1

© 2000 IEEE