One-dimensional microcavities are optical resonators with coplanar ref
lectors separated by a distance on the order of the optical wavelength
. Such structures quantize the energy of photons propagating along the
optical axis of the cavity and thereby strongly modify the spontaneou
s emission properties of a photon-emitting medium inside a microcavity
. This report concerns semiconductor light-emitting diodes with the ph
oton-emitting active region of the light-emitting diodes placed inside
a microcavity. These devices are shown to have strongly modified emis
sion properties including experimental emission efficiencies that are
higher by more than a factor of 5 and theoretical emission efficiencie
s that are higher by more than a factor of 10 than the emission effici
encies in conventional light-emitting diodes.