An analysis of the effective position of the two-dimensional electron gas in the channel of MODFET epitaxial layer structures

The charge control behavior of a range of heterostructure material systems typical of MODFETs has been investigated using a numerical model, and the "effective position of the two-dimensional electron gas (2-DEG) in the channel", /spl Delta/d, has been analyzed. We have shown that the parameter /spl Delta/d is well-defined for double-heterojunction structures, though with values very different from the often quoted figure of 80 /spl Aring/ , and that for AlGaAs/GaAs single heterojunctions, /spl Delta/d is strongly gate voltage dependent with values always larger than 80 /spl Aring/.