Impact of planar microcavity effects on light extraction-Part II: selected exact simulations and role of photon recycling

In this paper we use an exact calculation of dipole emission modifications in an arbitrary multilayer structure to obtain the extraction efficiency from realistic planar microcavities, additional insights gained through this exact approach compared to the simplified one of Part I of this paper [see ibid., p. 1612, 1998] are first discussed in the case of a dielectric slab. We next optimize for the extraction purpose asymmetric cavities bounded by metal on one side and dielectric mirrors on the output side for any pair of material indices in a broad range (n=1.4-4). The decrease of extraction when taking into account relative linewidths of the source of a few percent is shown to be moderate, allowing the large enhancements of monochromatic light to be maintained in many useful cases. The fractions of power emitted into guided modes, leaky modes, etc., are detailed. The beneficial role of possible photon recycling (reabsorption of emitted photons by the active layer) on extraction efficiency is evaluated using the fractions of power in guided and leaky modes. Extraction efficiencies in the 50% range are predicted for optimized, hybrid, planar metal-semiconductor structures for a wide range of active materials and wavelengths. We show that exact calculations justify the simple model used in Part I evaluating the extraction efficiency of a microcavity-based light-emitting diode as 1/m/sub c/ where m/sub c/ is the effective cavity order.