A numerical model that accurately describes interband tunneling in backward diodes and broken-gap tunnel diode structures based on the InAs/GaSb material system is described. The model applies the transfer matrix method to discretized bias-dependent energy band profiles to calculate the transmission probability for tunneling. The model has been validated against experimental results, with good agreement in the current-voltage and curvature coefficient having been obtained for a range of heterostructure backward diode and interband tunnel diode structures. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim