Band-to-band tunneling in III-V semiconductor heterostructures

To investigate the expected improvement in oncurrent and sub-threshold slope in III-V heterostructure tunnel field-effect transistors, we assess the band-to-band tunneling probability using a one-dimensional model based on the envelope function approximation. We present results for two-layer heterostructure diodes and compare them to the results of a commercial semi-classical simulator (based on Kane´s model). We observe large discrepancies between our model and the semi-classical simulation. These discrepancies occur when abrupt changes in electric field are present in the energy region associated with the band-to-band transitions. We conclude that Kane´s model is not generally applicable to heterostructures, due to the abrupt changes in electric field at the junction between materials. In contrast with an effective mass approximation, our model predicts additional reflections due to a change from a conductionband state to a valence band state, also in a broken gap structure.