As a HEMT channel is formed by heterolayers with typical channel widths of 10 nm-20 nm, a highly quantum mechanical situation is
encountered. The typical geometrical width is smaller than the de Broglie length of 26 nm in GaAs,
as pointed out by Shur in  and also given in Appendix B.
This work treats the channel in a classical approach. This section
supplies some basic estimates of the error introduced with respect
to the material systems used. Based on the stationary Schrödinger equation