Deep level in the InAs/InAsSb superlattice revealed by forward-bias tunneling

The analysis of forward-bias tunneling data to determine the energy position of a deep level in the gallium-free InAs/InAsSb superlattice is reported. The level is found in p–n junction devices built for mid-wavelength infrared detection. The traps that produce this level can facilitate a trap-assisted tunneling (TAT) current in forward bias that adds to the conventional diffusion dark current. The effect is manifested as a peak in the ideality factor, where the TAT current turns off at a voltage above which the band alignment no longer permits tunneling. We apply the tunneling model of Anderson developed for HgCdTe. Our analysis of data from InAs/InAsSb having a bandgap energy of 220 meV finds the trap energy to be 170 meV above the valence band edge.