Intrinsic GaAs layers of 1 and 3 mu m thickness on a highly doped n(++)-substrate, were covered with very thin Au layers (10 nm) in order to manufacture planar field emission cathodes. At nearly the tenfold Gunn field of about 50 kV/cm we observe the beginning of hot and ballistic electron emission into vacuum. The energy distributions span several eV, exceeding even 10 eV for thick samples. We have started to describe this high energy transport by means of Monte Carlo calculations including acoustic and optical phonon interaction of electrons, intervalley scattering, and impact ionization of valence band electrons. In earlier work we have done vacuum emission experiments, electron beam induced conductivity and Monte Carlo calculations to examine and analyze high field transport in ZnS and SiO2.