  Bose-condensation of mass-less quasiparticles (photons) can be easily
achieved at the room temperature in lasers. On the other hand, condensation of
bosons having a non-zero mass requires usually ultra-low temperatures.
Recently, it has been shown that polaritons, which are half-light-half-matter
quasi-particles, may form condensed states at high temperatures (up to 300K).
Polaritons composed by electron-hole pairs coupled to confined light modes in
optical cavities may form a Bardeen-Cooper-Schriefer (BCS) superfluid. We
propose a new transistor based on stimulated scattering of electron-hole pairs
into the BCS polariton mode. A pn-junction embedded inside an optical cavity
resonantly emits light into the cavity mode. If the cavity mode energy slightly
exceeds the band-gap energy, it couples with electron-hole pairs with zero
centre of mass wave-vector but non-zero wave-vector of relative motion. This
creates a super-current in the plane of the structure. In an isotropic case,
its direction is chosen by the system spontaneously. Otherwise, it is pinned to
the external in-plane bias. We calculate the phase diagram for the
electron-hole-polariton system.
