Interface-induced conversion of infrared to visible light at semiconductor interfaces

Efficient, low-temperature conversion of infrared light into visible light (red, orange, green) is reported at single heterojunctions and undoped quantum wells of GaAs and ordered ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{In}{\mathrm{P}}_{2}$; an increase in photon energy of 700 meV is obtained. The signal originates from the high-band-gap layers and disappears only if the excitation energy is tuned below the GaAs band gap. The intensity of the up-converted photoluminescence (PL) is found to decrease significantly slower with increasing temperature than that of the regular PL and it remains observable up to 200 K. Interface-induced cold Auger processes along with the presence of trapped states for both electrons and holes in these ordered alloys account for this nonlinear mechanism. A colinear double-beam experiment confirms this.