Session Q27 - Quantum Well Lasers.
MIXED session, Wednesday afternoon, March 18
505, Los Angeles Convention Center
Due to total internal reflection, isotropic spontaneous emission in planar InGaAs/InP structures has a very small chance of escaping the high refractive index material. Recycling (i.e. absorption and re-emission) of trapped photons yields additional opportunities for nonradiative recombination and limits the efficiency of ordinary 1600 nm light-emitting diodes to a few tenths of a percent. We are pursuing several strategies for improving the coupling of photoluminescence out of this system. By polishing the substrate into a lens or bringing an index-matching lens into optical contact with the surface of the epilayers, the external efficiency of lattice-matched InGaAs/InP double heterostructures can be increased to about 50 percent at room temperature. We combine optical and thermal measurements on these devices to obtain the absolute external emission efficiency over a wide range of carrier densities. Using a simple model, this efficiency measurement can be used to determine radiative and nonradiative recombination rates in the active material.