  We propose a compact high-intensity room-temperature source of entangled
photons based on the efficient second-order process of two-photon spontaneous
emission from electrically-pumped semiconductor quantum wells in a photonic
microcavity. Two-photon emission rate in room-temperature semiconductor devices
is determined solely by the carrier density, regardless of the residual
one-photon emission. The microcavity selects two-photon emission for a specific
signal and idler wavelengths and at a preferred direction without modifying the
overall rate. Pair-generation rate in GaAs/AlGaAs quantum well structure is
estimated using a 14-band model to be 3 orders of magnitude higher than for
traditional broadband parametric down-conversion sources.
