Vertical transport and large negative differential resistance of epitaxial GaAs/ErAs/GaAs buried semimetal/semiconductor heterostructures

We have studied vertical transport properties of GaAs/ErAs/GaAs buried semimetal/semiconductor heterostructures grown by molecular beam epitaxy, in which an ultrathin semimetallic ErAs layer is buried in GaAs. The heterostructures are shown to have atomically abrupt interfaces and controlled thickness of ErAs without pinholes, containing defects in the overgrown GaAs layer. In the current–voltage characteristics of the heterostructures with an ErAs thickness of 10 nm, we have observed a clear negative differential resistance with large peak-to-valley ratios of 7.2 at 300 K and 18.3 at 77 K.