In this work we explore planar cathodes emitting electron currents at room temperature, based on a new concept of electron emission from a serial process. This serial process uses a solid-state Schottky metal-semiconductor barrier to inject electrons into a held-controlled negative electron affinity surface which is an ultrathin semiconductor layer. A model for the electron emission for these planar cathodes is proposed and discussed within the experimental data obtained. Analysis of the emission behavior was performed with different planar cathodes presenting a low Schottky barrier metal-semiconductor junction (similar to 0.1 eV) with an injection medium having different cathode geometries in order to localize the emission area. The analysis included measurements of the emitted currents versus applied voltages and time, variations of the currents with temperature, energy distribution of the emitted electrons, and numerical simulations of the field distribution over the cathode. Stable electron currents are experimentally obtained from such planar cathodes with small operating electric fields (similar to 10 V/mu m) and with working vacuum as low as 10(-7) Torr.