We present details of a new approach to the modelling of nanometre sca
le devices which are based on the two-dimensional electron gas (2DEG)
confined at the interface of a GaAs/AlGaAs heterostructure. The model,
which is based on a finite difference solution to the Poisson equatio
n, uses a Fang-Howard variational function to describe the 2D electron
wavefunctions, and includes the effects of both a laterally and a ver
tically inhomogeneous distribution of ionized donor impurities. A self
-consistent method of adjusting the boundary conditions is employed to
calculate the effect of an additional bias voltage. We apply our tech
nique to the relatively simple case of a single-barrier lateral tunnel
ling diode. Calculated current-voltage (I-V) characteristics are in ex
cellent agreement with measured data using only the experimentally det
ermined barrier height as a fitting parameter. Although our discussion
is limited to a specific structure, we suggest that our method is app
licable to a wide range of heterostructure devices.