<title>Planar substrate-emitting-microcavity light-emitting diodes with 20% external QE</title>

Abstract

The external QE of microcavity light emitting diodes strongly depends on the device size and operational current density. Our experiments reveal that spectral broadening of the optical spectrum emitted by the three InGaAs QW's as well as photon recycling of photons originally emitted into the guided mode of the cavity can explain these differences. An optimized microcavity layer design yielded external QE's of 20% for substrate emitting light emitting diodes with diameters of 1 .5 mm.

Impact of planar microcavity effects on light extraction-Part I: basic concepts and analytical trends

“…Noting that the Airy denominator [(T8)] increases at and from its resonance minimum to a value approximately given by (14) most of the concentration in the resonant mode is achieved when the second factor is about 10. This translates into as a safe practical "working point" and (15) a value generally below 90%, in agreement with recent microcavity LED's in particular studies [9], [11], [18]- [20], [22]- [25], [32]. It is easy to show that such a reflectivity gives 80%, leaving little room for improvements.…”

“…Without losses, the diminished cavity order instead of would translate into an extraction increased from 11% to 20%. Additional enhancement factors [9], [18], [19], [22], [24] including, e.g., dipole orientation, photon recycling, etc., indeed resulted in 23% efficiency [23], [25] in such an asymmetric structure with a six-pair DBR on one side and a nonalloyed high-reflectivity metal contact on the other side.…”

“…Instead, we discuss here what can be expected from microcavities [11], [12], [14]- [21] to alleviate the poor extraction efficiency of high-index materials retaining a simple planar structure but redirecting as many photons as possible into the escape cone by means of interferences. In the GaAs testbed case, optimized microcavity LED's at 980 nm already demonstrated 22.8% [22]- [25], prompting us to generalize this result and to determine what are the ultimate perfomances one can expect.…”

Experimental demonstration of a multichannel micro-optical bridge for multi-gigabit per second free-space intra-MCM interconnects

“…These will make use of new device-level components such as arrays of Vertical Cavity Surface Emitting Lasers (VCSEL's) [2] or arrays of Micro Cavity Light-Emitting Diodes (MCLED's) [3] and low power photoreceiver circuits [4]. One of the challenges associated with the development of free-space intra-and inter-MCM optoelectronic interconnects is the fabrication of manufacturable, chip-compatible, and high precision monolithic micro-optical pathway blocks.…”

InP-based microcavity light emitting diodes emitting at 1.3 μm and 1.55 μm

“…Introduction In the GaAs system, the microcavity concept has proven to be very successful in increasing the overall quantum efficiency of light emitting diodes (LED's)[ 1] [2]. Due to the reduced refractive index contrast available in the InP material system, a transfer to longer wavelengths is certainly not straightforward.…”