In this work we extend an effective mass model for computing the drain current of tunnel-FETs to account for the anti-crossing of the light- and heavy-hole branches of the valence band. The model is validated by comparison with NEGF simulations based on a k · p Hamiltonian. Application of the new model to the electron-hole bilayer TFET is provided showing that the inclusion of the asymmetry of the real and imaginary branches of the hole dispersion relation is critical in determining the device characteristics. © 2015 IEEE.