Diplomarbeit, Rheinisch-Westfälische Technische Hochschule Aachen, 1989; Diplomarbeit, Rheinisch-Westfälische Technische Hochschule Aachen, 1989, The hot electron transport in the ballistic regime is calculated for inhomogeneously doped sub-micron structures [0.4 μm] of GaAS, based on the coupled Boltzmann transport - and Poisson equations. We use for the solution of this integrodifferential equation system the moment method, with a six equations hiearchy. Numerically, we apply for the first time the homotopy analysis method for the solution of this nonlinear equation system which allows us to describe the strong non-equilibrium electron transport in three dimensions. Thereby, for the first time, the three dimensional semi-classical electron transport can be calculated together with quantum-mechanical collision operators, here acoustic electron-phonon as well as electron-impurities interactions. With this three-dimensional electron transport Boltzmann‘ moment equations we are able to calculate the behaviour of temperature variation orthogonal to the direction of transport.