Long-range pair transport in graded band gap and its applications

The transport of electron–hole pairs in graded band gap of mixed crystal semiconductors is examined. It is estimated that a pair can be transferred for about 30 μm within its lifetime in the band gap gradient of 1 meV/μm in the low-temperature AlGaAs quantum well. Various opto-electronic devices by means of the pair transport are proposed. As one of exciting applications, the author proposes the quantum up-converter, where incoherent low-energy photons are converted to high-energy photons.