THE ELECTRON-MOBILITY TRANSITION IN N-GAAS HEAVILY-DOPED CHANNELS

Low-field electron transport properties in heavily doped n-GaAs channels at 300 K are investigated by Monte Carlo simulation. The matrix element for electron-impurity scattering is obtained from the Fourier-transformed Coulomb potential accounting for the screening effects of the two-dimensional electron gas. The effects of the screening and the impurity profile are analysed. Electron mobility is calculated for several values of sheet electron density and n-GaAs thickness. For low sheet electron density, the calculated mobility increases with the sheet electron density and is almost independent of n-GaAs thickness. For high sheet electron density, the mobility approaches a constant value and becomes independent of sheet electron density. These findings are explained for the first time as a transition from a two- to three-dimensional nature and are well confirmed by our experiments.