We present calculations of band discontinuities for Si1-xGex/Si1-yGey strained/relaxed heterointerfaces using the model-solid theory. From the obtained results, we then report a numerical simulation of the conduction-band diagram of a resonant tunneling diode in the Si/Si1-yGey system by solving self-consistently Schrödinger and Poisson equations with and without an applied electric field. An analysis of the Stark effect was made in the investigated heterostructure. Two main features have been extrapolated: (i) two sheets of a two-dimensional electron gas are created, leading to a resonant tunneling through the structure, (ii) a charge transfer can occur due to this tunneling effect. In addition, it is found that this charge transfer is highly sensitive to temperature and tends to saturate as the applied electric field increases. © 2002 American Institute of Physics.