  We report strong light emission from a room-temperature n-type unipolar-doped
In0.53Ga0.47As/AlAs double-barrier resonant-tunneling diode (DBRTD) precisely
at the In0.53Ga0.47As band-edge near 1650 nm. The emission characteristics are
very similar to what was observed recently in GaN/AlN DBRTDs, both of which
suggest that the mechanism for emission is cross-gap electron-hole
recombination via resonant- and Zener co-tunneling of electrons, the latter
mechanism generating the required holes. Analysis shows that because of the
relatively small bandgap, the Zener tunneling probability can be large in this
In0.53Ga0.47As/AlAs DBRTD, and is a mechanism that may have been overlooked in
the longstanding literature. The universal nature of the co-tunneling is best
supported by the factor (EG)2/F in the Kane tunneling probability, which is
nearly the same at the peak voltage of the In0.53Ga0.47As and GaN DBRTDs.
