Improved performance by optimised planar doped barrier launcher in GaAs vertical FET with very short channel width

The current-voltage characteristics of a GaAs vertical field effect transistor (VFET) with an n⁺ip⁺in⁺ planar doped barrier (PDB) launcher has been successfully improved by the optimisation of the launcher structure as well as the reduction of the channel width. Electron-beam direct writing has been used to obtain a small channel width of 0.1 approximately 0.15 mu m, resulting in good pinchoff characteristics. The measured maximum transconductances are 383 and 220 mS/mm at 77 and 300 K, respectively. In spite of a very short channel length (0.1 mu m) and relatively low channel doping density (5*10¹⁶ cm^-3), a high voltage gain of 15 has been obtained.