Applicability of the High Field
Model: A Preliminary Numerical Study
By: Carlo Cercignani, Irene Gamba, Joseph W. Jerome and Chi-Wang Shu
In a companion presentation, we have discussed the theory of a
mesoscopic/macroscopic model, which can be viewed as an augmented
drift-diffusion model. Here, we describe how that model is used.
The device we consider for this presentation is the one dimensional
GaAs n+/n/n+ structure of length 0.8 microns.
First, a full hydrodynamic (HD) model, proven reliable when compared with
Monte Carlo simulations, is used to simulate the device via the ENO finite
As applied to the full device, the new model is
not necessarily superior to traditional
Indeed, when we plot the quantity involving the
electric field, we verify that the high field assumption,
required for the high field model,
is satisfied only in an interval given approximately by [0.2, 0.5].
When we run
both the DD model and the new high field model in
this restricted interval, with boundary conditions of concentration
and potential provided by the HD results, we
demonstrate that the new model outperforms the DD model.
This indicates that the high field and DD models should be used only in
parts of the device, connected by a transition kinetic regime.
will be a domain decomposition issue involving
interface conditions and adequate numerical methods.
This paper has appeared in VLSI DESIGN 8 (1998), 275--282, and
can be viewed in the following format: